TRUCK DRIVER USAGE OF MAIN DRIVING CONTROLS Master’s Thesis in Master Degree Programme, Product Development PAUL PRAVEEN PETER Department of Product and Production Development Division of Product Development CHALMERS UNIVERSITY OF TECHNOLOGY Gothenburg, Sweden, 2012 2 3 TRUCK DRIVER USAGE OF MAIN DRIVING CONTROLS Master’s Thesis in Master Degree Programme, Product Development PAUL PRAVEEN PETER Supervisors at Volvo Patrik Blomdahl, Ergonomics Team Leader, Volvo Trucks Martina Söderberg, Feature Leader, Volvo Trucks Supervisor at Chalmers Professor Hans Johannesson, Head of Division, Product Development Department of Product and Production Development Division of Product Development CHALMERS UNIVERSITY OF TECHNOLOGY Gothenburg, Sweden, 2012 4 Truck Driver Usage of Main Driving Controls Paul Praveen Peter, 2012. Copyright© 2012 Paul Praveen Peter Gothenburg, Sweden, 2012 Department of Product and Product Development Division of Product Development Chalmers University of Technology SE-412 96 Gothenburg Sweden Telephone: +46 (0) 31-772 10 00 Cover Page Picture: Truck Picture belongs to Volvo Trucks Product Design, Sweden. Steering Wheel, Pedals and Gear shift lever pictures were taken from Google and they are not affiliated with Volvo Group. 5 Acknowledgements The Thesis work “Truck Driver Usage of Main Driving Controls” was carried out at Volvo Group Trucks Technology from March 2012 to October 2012. The thesis work is the final project that needs to be accomplished for the master‟s degree in Product Development in Chalmers University of Technology. At this special time, I would like to thank my supervisors of the project, Patrik Blomdahl, Martina Söderberg and Peter Johansson for their continuous feedback and support during the course of the Project. I also extend my thanks to: Jonas Persson, Johan Landen, Richard Larsson, Marcus Elmer, Helen Kjellen, Thomas Fagerström, Tommy Larsson and all the test drivers, feature leaders, feature specialists and drivers for active participation in the driving sessions and interviews. I would like to thank my -supervisor Professor Hans Johannesson at Chalmers University of Technology, for his constant support and encouragement during the course of the Project. My special thanks goes to my wonderful family, Dad (Peter Brundin), Mom (Shanthini), and Sis (Patsy) for your support during these two and half years. I also thank my near and dear ones. Finally, thank you Jesus. “In God We Trust” Paul Praveen Peter 6 Table of Contents Acknowledgements ........................................................................................................5 Abstract ............................................................................................................................ 10 1. Background .............................................................................................................. 11 1.1 Ergonomics ............................................................................................................................. 12 1.2 Truck Manufacturers and Industry........................................................................................... 13 1.3 Volvo Group ............................................................................................................................ 14 1.4 Truck Segments ....................................................................................................................... 14 1.5 Truck Drivers ........................................................................................................................... 17 1.6 An Overview of the Truck Driving Controls in the Volvo FH ...................................................... 18 1.7 Ergonomic Background Studies ............................................................................................... 20 1.7.1 Anthropometry................................................................................................................. 20 1.7.2 Percentiles........................................................................................................................ 20 1.7.3 Human Variations ............................................................................................................. 21 1.7.4 Force Limits in using the controls ...................................................................................... 21 1.8 Occupant Packaging Nomenclature ......................................................................................... 22 2. Methods of Data Collection ................................................................................ 24 2.1 Questionnaires ........................................................................................................................ 24 2.2 Interviews ............................................................................................................................... 24 2.3 Brainstorming ......................................................................................................................... 25 2.4 Benchmarking ......................................................................................................................... 25 2.5 Observations ........................................................................................................................... 25 2.6 Literature Materials................................................................................................................. 25 3. Data Collection in the Project ............................................................................ 26 3.1 Interviews at Björkäng ............................................................................................................. 26 3.2 Volvo Demonstration Centre ................................................................................................... 26 3.3 Scania Demo Centre ................................................................................................................ 26 3.4 Hällered Proving Ground ......................................................................................................... 26 3.5 Feature Specialists................................................................................................................... 27 3.6 Ergonomic Feature Leaders ..................................................................................................... 27 4. Results of the Data Collection ........................................................................... 28 4.1 Kano Model ............................................................................................................................. 28 4.1.1 Steering Wheel Control .................................................................................................... 29 7 4.1.2 Gear Shift Lever ................................................................................................................ 33 4.1.3 Pedals ............................................................................................................................... 35 5. Measurement Technique for driving controls ............................................. 38 5.1 Steering Wheel Control ........................................................................................................... 38 5.1.1 Steering Effort Sensor ....................................................................................................... 38 5.1.2 Measuring Steering Wheel Adaptor .................................................................................. 39 5.1.3 Glove Pressure Sensor ...................................................................................................... 40 5.1.4 Pressure Mats................................................................................................................... 41 5.1.5 Force Gauges .................................................................................................................... 43 5.1.6 Steering Robot .................................................................................................................. 44 5.2 Gear Shift Lever ....................................................................................................................... 45 5.2.1 Ricardo Gear Shift Quality Assessment ............................................................................. 45 5.2.2 Shift Knob Load Cell .......................................................................................................... 47 5.2.3 Hand Sensor Array ............................................................................................................ 47 5.3 Pedals ..................................................................................................................................... 49 5.3.1 Accelerator & Brake Robots .............................................................................................. 49 5.3.2 Brake Pedal Force Sensor.................................................................................................. 51 5.3.3 Pedal Load Cell ................................................................................................................. 52 5.4 Results from the Measurements.............................................................................................. 53 5.4.1 Forces from the Steering Wheel using measurement steering wheel adaptor ................... 53 5.4.2 Forces from the Brake pedal using brake pedal load cell ................................................... 54 5.5 Evaluation of the measurement technique for ergonomics testing .......................................... 56 6. Evaluation of Driving Controls for further Investigation ........................ 58 Kesselring Matrix .......................................................................................................................... 58 7. Pedals ......................................................................................................................... 63 7.1 Type of Pedals ......................................................................................................................... 63 7.1.1 Suspended Pedals ............................................................................................................. 63 7.1.2 Floor Mounted Pedals ...................................................................................................... 63 7.1.3 Combination of Floor Mounted and Suspended Pedals: .................................................... 64 7.1.4 Areas of Application ......................................................................................................... 64 7.2 Pedal Aspects .......................................................................................................................... 65 7.2.1 Pedal Size ......................................................................................................................... 65 7.2.2 Pedal Curvature ................................................................................................................ 66 7.2.3 Movement between the pedals ........................................................................................ 67 8 7.2.4 Fitts Law ........................................................................................................................... 68 7.2.5 Friction ............................................................................................................................. 71 7.2.6 Reachability ...................................................................................................................... 72 7.2.7 Strokes and Sensitivity ...................................................................................................... 72 8. EuroFOT –European Field Operative Test ...................................................... 73 8.1 Background ............................................................................................................................. 73 8.2 Process .................................................................................................................................... 74 8.3 Investigation ........................................................................................................................... 75 8.4 Results .................................................................................................................................... 76 8.5 Observations ........................................................................................................................... 77 8.6 Proposals ................................................................................................................................ 77 8.7 Limitations .............................................................................................................................. 78 9. Pedal usage observations ................................................................................... 79 9.1 Background ............................................................................................................................. 79 9.2 Fixture Design ......................................................................................................................... 79 9.3 Process .................................................................................................................................... 79 STEP 1: Installation .................................................................................................................... 80 STEP 2: Driving session with shoes............................................................................................. 82 STEP 3: Driving session with barefoot ........................................................................................ 83 STEP 4: Post processing of the video material ............................................................................ 84 Processing the Video Material ................................................................................................... 85 9.4 Limitations of the Method: ...................................................................................................... 86 10. Results from Pedal usage observations ..................................................... 87 10.1 Objective Measurements ...................................................................................................... 87 10.2 Subjective Evaluation ............................................................................................................ 92 11. Discussion of the results ................................................................................. 99 12. Recommendations ............................................................................................ 103 13. Future studies in Driving Controls ............................................................. 107 Bibliography .................................................................................................................. 108 APPENDIX - A ................................................................................................................. 109 APPENDIX - B ................................................................................................................. 110 APPENDIX - C ................................................................................................................. 124 APPENDIX - D ................................................................................................................ 141 APPENDIX - E ................................................................................................................. 151 APPENDIX - F ................................................................................................................. 152 9 APPENDIX - G ................................................................................................................. 156 APPENDIX - H................................................................................................................. 158 Forces from the gear shift lever ............................................................................................... 159 APPENDIX - I .................................................................................................................. 164 APPENDIX - J .................................................................................................................. 172 Pedal Angles in 2D (SAE Manikin) ................................................................................................ 172 APPENDIX - K ................................................................................................................. 175 APPENDIX - L ................................................................................................................. 194 APPENDIX - M ................................................................................................................ 196 APPENDIX - N................................................................................................................. 198 APPENDIX - O ................................................................................................................ 200 APPENDIX - P ................................................................................................................. 201 APPENDIX - Q ................................................................................................................ 203 APPENDIX - R ................................................................................................................. 205 APPENDIX - S ................................................................................................................. 218 APPENDIX - T ................................................................................................................. 230 10 Abstract The aim of the thesis work was to investigate and study the ergonomic issues related to the usage of the main driving controls; the steering wheel, pedals and gear shift lever in the truck. The drivers‟ expectations and evaluations of different features were presented in the Kano model to explore new possibilities for improvement. A methodology to search for different tools and equipment for measuring the forces from the steering wheel, pedals and the gear shifter lever was carried out. Then, one measurement technique was proposed to measure the forces from the driving controls for ergonomics testing and evaluation. The driving controls were evaluated with the Kesselring matrix to select one final driving control for detailed investigation. Pedals were selected for detailed investigation on the usage of driving controls across different truck segments. Keywords: Steering wheel, Pedals, Gear shift lever, EuroFOT, Ergonomics, Pedal usage, driving controls 11 1. Background The CAB division interior at Volvo Group Truck Technology (Volvo GTT) was responsible for the development of new interiors for the different Truck brands (Volvo Trucks, Renault Trucks, Mack, UD Trucks) and maintains today's production. A truck driver spends a lot of time in the driver seat. It is important that he or she can handle the truck in an optimal way. In this thesis project, “Truck Drivers usage of main Driving Controls”, the following driving controls were investigated with regards to how the drivers use the controls and how the controls could be improved.  Steering wheel  Pedals  Gear shift (manual / automatic)  Stalks Initial studies were made about the driving controls usage in different transport segments (long-haul / distribution / construction) as well as the influences from different road conditions (smooth / rough, flat / hilly and straight / winding) and weather conditions (e.g. good friction versus slippery). Then the force levels, strokes, feeling and feedback of the driving controls were investigated and a suitable force measuring method was proposed for the Ergonomics Division at Volvo Trucks. The primary target of the project was to come up with detailed information about how the controls were used, i.e. how the driver‟s hands and feet should be positioned in relation to the different controls. In parallel to this, proposals for how existing controls could be improved were also established. Together with Volvo GTT, one set of controls was chosen for further investigation to establish prerequisites for a later product implementation and mean mutual gains for the truck drivers and Volvo Trucks. 12 1.1 Ergonomics “Ergonomics is defined as scientific discipline concerned with the understanding of the interactions among the humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human wellbeing and overall system performance” – International Ergonomics Association Advantages of ergonomics for Vehicle Manufacturers and Customers •Sustainable Design • Improved Safety • Low injury rate •Better Brand Image •Improved Quality •Improved Satisfaction •Better Market Position •Higher reliability of Delivery •Fewer cases of disability •Fewer lost working days •Lower cost •Better Motivation •Less Fatigue •Efficient Movements Productivity Cost Values and Standards Competitiveness 13 1.2 Truck Manufacturers and Industry Truck Manufacturers have a stake in and ownership over other truck companies to boost the sales and to share technology and expertise within their development centers. The Volvo Group consists of four truck brands, Volvo, Renault, UD trucks and Mack Trucks. The top three truck manufacturers on the global truck market were Daimler AG, the Volvo Group and Dongfeng Trucks. In Europe, other known truck brands are Scania from the Volkswagen Group, DAF from the PACCAR group and MAN SE and IVECO from the Fiat group. The commercial vehicle market has grown, and will continuous to grow drastically. The picture below shows the market trend in the commercial vehicle (Light commercial vehicle with 6 tons and above 6 tons) market from 2006 to 2012. From a truly global perspective, the truck market is a growth oriented market with a forecast for increasing up to 33 million units by 2015 if current trends continue. (Dieter, 2011) 14 1.3 Volvo Group This thesis work was carried out at the Volvo Group Trucks Technology‟s headquarters in Lundby in Gothenburg. Volvo Trucks Technology, itself a company within the Volvo Group, develops solutions for the commercial truck industry for four brands across the globe. The four truck brands are Volvo Trucks, Renault Trucks, MACK trucks and UD Trucks. It also has a joint venture with Eicher India Limited as Volvo Eicher Commercial Vehicle which develops medium duty trucks for the South Asian Market. Volvo Group Trucks Technology works with Volvo Technology in advanced research programs within the transportation industry. Volvo Group Trucks Technology was established in 2012 by combining Volvo Powertrain and Volvo Trucks Corporation. Now, Volvo Trucks Technology develops solutions for a truck as a whole and focuses on Product Development, Cab Development, Vehicle Engineering and Powertrain Development – nearly everything within the Truck. This thesis work was carried out in the Ergonomics Division within the cab engineering department working with the ergonomic features; Driver Position, Visibility, Resting Comfort, Working Comfort and Entry & Exit. 1.4 Truck Segments A truck generally is a type of vehicle used to ship goods. Commercially, trucks are used for various applications. Heavy trucks can be specified as vehicles having a total weight of around 16 tons. A loaded truck could weigh from 20 to 40 tons. The fully loaded truck may have a length of around 16 meters and weight of around 40 tons, as determined by the legal requirements in Sweden. There are heavier and longer trucks with a length of around 20 meters which are primarily referred to as road trains in Sweden. These are used for long Figure 2: The market share of the truck manufacturers in Western Europe Figure 1: Development of the Commercial Vehicle Market of Trucks by region 15 distance transportation. Even road trains are being tested by Volvo Trucks for timber transportation applications in Sweden. The project focuses on the trucks for different applications like long haulage, distribution and construction. The truck‟s container or trailer configuration differs based on the applications. Long-haul Trucks: Long haulage trucks are used to transport goods regionally, nationally or even as cross- country cargo shipments. Since long haulage trucks move the goods both in the day as well at night, the drivers have to stay in the truck for few days in order to transfer the goods. The truck travels on the motorways during its mission, so emphasis is placed on driver comfort and fuel economy. For Volvo the FH series serves this application. The Volvo FH truck is available in different configurations, normally with the tractor unit and trailers attached to it. Figure 3 : Volvo FH –Long haulage truck The Long-haul truck is available in 420, 460, 500, 540, 600, 700, 750 horsepower engine configurations. Distribution Trucks: The distribution trucks are used to transport goods within communities and cities and involve shorter distances with a lot of “start-stop” events. Nowadays, emissions and regulations on sustainable transport are pushing vehicle manufacturers to develop energy efficient and low emission vehicles with good energy recuperation system within the powertrain. The distribution trucks will travel for shorter distances with loading and unloading of goods. Usually, the driver will use the entry/exit doors more frequently than the long-haul truck drivers. In Volvo, FL and FE models serve the distribution segment. The distribution trucks are powered by low power engines with smaller cab. Distribution trucks are powered by low power engines with 240 and 280 horsepower. The distribution truck drivers use the driving controls more often than the long-haul truck drivers, since the distribution trucks are often used within the city traffic limits. 16 Figure 5: Volvo FE Distribution Truck Construction Trucks: Construction trucks are employed at mining sites and in specific geographical locations. The construction trucks are rugged with high strength and maneuverability to meet the driver‟s demand to move gravel and dirt on rough ground. The FMX trucks can be seen where construction equipment, like wheel loaders and excavators, are employed. These trucks can transport heavy weights and have a higher towing capability than normal trucks. The FMX is powered by a high torque capable engine specially designed for construction purposes. The FMX is a perfect off-road truck that can handle 100 tons of cargo. The drivers usually drive the vehicle in rugged terrain so the main priority is placed on increasing driver comfort by reducing the vibrations and on increasing fuel economy. The Figure 4:Volve FL Distribution Truck 17 Volvo FMX engine is available in 380, 420, 480 and 500 horsepower configurations in I-shift, manual and Powertronic (automatic) transmissions. Figure 6: Volvo FMX Construction Truck 1.5 Truck Drivers There were around 115,000 drivers working in Sweden in 2004. However, this number was hard to pinpoint because of the number of foreign drivers who travel to and from Sweden. The truck industry is a male dominant industry with a very small percentage of female drivers. A study by Volvo says that 6% of the total 100,000 drivers are female. This percentage includes women driving the long-haulage truck as well. (PublicReport) There are many laws regulating the driving of trucks on Swedish roads. One law is the drive and rest times. The driver is only allowed to drive for a maximum of 9 hours/day, with one break of at least 45 minutes, alternatively two breaks of 15 and 30 minutes respectively. A driver is not allowed to drive more than 4.5 hours in one run (According to EU regulations, 2006). A built-in trip computer in the truck cab automatically monitors and records the driving time. The trip computer is analyzed by the traffic police if the truck driver is stopped along the way. If the driver continues to drive one minute more than what the trip computer stipulates, the truck driver or owner of the company has to pay a fee of, at most, 10000 to 200000 SEK. (Report, 2011) 18 1.6 An Overview of the Truck Driving Controls in the Volvo FH The driver is surrounded by the driving controls, gauges, buttons and levers in the truck cab. The main driving controls investigated in the project were the steering wheel, pedals (accelerator, brakes and clutch) and gear shift lever. The transmission system in the FH is available in two main configurations (1) Manual gearbox and (2) Powertronic (automatic) gearbox (3) I-Shift in 12 speed gearbox. The figure below shows the I-Shift gear lever in Volvo FH truck. I-shift combines the best characteristics of manual and automatic transmissions. I-Shift offers electronically controlled splitter and range gear shifting unlike manual transmission gear levers with I-Shift, the driver can focus on driving. It is still possible to change gears manually by simply pulling the gear lever to the manual setting and then change up or down using the button on the side of the gear knob. The truck with I-Shift system has no clutch pedal and the gear Engagement and disengagement are entirely automatic. Figure 7: Volvo I-SHIFT Gear shift lever Figure 8: Volvo FH Steering Wheel 19 The steering wheel in Volvo is equipped with a button to control the entertainment and communication system in the truck as well as to active and deactivate the cruise control features. The steering wheel, with telescopic and tilt adjustment features, can be adjusted by manipulating a pedal operated by the left foot. However, the neck tilt function is available only in the new Volvo FH truck. Figure 9: Volvo FH Pedal Layout The accelerator and brake pedal is mounted to the right side of the steering column with two separate pedal carriers. The accelerator pedal is found in the far right position. The brake pedal is mounted between the accelerator pedal and steering column. The clutch pedal in the manual transmission truck is mounted to the left side of the steering column. The parking brake is located at the top of the instrumental panel. The dash board or instrument panel is equipped with speedometer, tachometer and gauges in the front shelf and displays the technical information related to various systems in the truck. Figure 10: Volvo FH Interior Layout 20 1.7 Ergonomic Background Studies 1.7.1 Anthropometry The branch of science that relates to the measurement of the human individual is called anthropometry. Anthropometry plays an important role in driving control design and ergonomics. The anthropometric measurements can be classified into two categories. Static Anthropometric Measurements: The static measurements are traditional measurements obtained by the anthropologists from the human body and are comprised of length, width, height with respect to standard positions, either sitting or standing. Function Oriented Measurements: The functional measurements are taken with the human body at work. These measurements are mostly three-dimensional and they are expressed in three co-ordinates for workspace or body landmarks. The functional anthropometric measurements for drivers of trucks were completely different when compared with drivers of cars. Some measurements, like total foot length and ankle height, can be used as supportive data for designing the foot controls in the truck. (R.W.Roe, 1993) 1.7.2 Percentiles The body dimensions of humans can be plotted on a graph with measurements on the horizontal x-axis increasing towards the right from the zero. The frequency of occurrences was plotted on the y-axis, increasing towards the top from the zero. A smooth curve averaging the particular height dimension will appear bell-shaped. In this case mean, median and mode do not coincide. The data from one dimension does not correlate with the other dimensions. For instance, small woman may have a small or large hip width. This information should be kept in mind when designing for an average person. It is difficult to design for everyone. The few percent at either end of the normal curve may be so extreme that a design becomes too expensive to produce. In military standards they chose to exclude 5% at the small end and 5% at the large end. Thus, only 90% of the measured population was considered. The 5% of the value is called the 5th percentile and 95% of the value is called the 95th percentile. 21 Figure 11 Percentile in Human Population If we need different percentile, the standard deviation needs to be calculated. √ Where = summation, d = difference between one person‟s measurements and arithmetic mean of that measurement N = Number of people measured 1.7.3 Human Variations Human beings are unique and no two people are identical, not even twins. Therefore, three categories of human variability exist. Intra-individual sizes: Sizes changes during adult life. Some changes are due to aging, others are due to movement or environmental differences from one place to another. Inter-individual: There are big differences due to sex, ethnic and racial factors. Differences include skin, colour, body proportions and other features. The dimensions of feet and fingers differ drastically between sex and race. Secular variability: changes occur from generation to generation for various reasons. However, the pace of change is slow; they have limited effect on human variations. (Henry Dreyfuss, 2002) 1.7.4 Force Limits in using the controls The force limits of pedals differ based on sex and foot dimensions. Hand Controls: Steering Wheel: Normal force in one hand – 13 N to 22 N 22 Maximum force in one hand – 89 N Maximum force in two hands – 133 N Gear Shift Lever: Hand Forces Push 22 N Hand Forces Pull: 44 N Max Force Push or Pull: 66N Foot Controls: Pedals: The ball of the foot reaches the brake pedal with the force of 507N for the 5th percentile man whereas for the 5th percentile female it reaches with a force of 338N. The resistance force from the brake pedal should be around 44.5 to 222.4 N. The resistance force in the accelerator pedal should be around 17.8 to 44.5 N. (Henry Dreyfuss, 2002) 1.8 Occupant Packaging Nomenclature This section discusses the major technical landmark in the occupant packaging. The functional task oriented design of foot controls is comprised of anthropometric measurements that are referenced to specific human body landmarks like BOF (Ball of Foot) and PCP (Pedal Contact Point). The reference points are normally related to the driver‟s foot in relation to the vehicle interior such as floor, foot controls or seat.  Accelerator Heel Point (AHP): The lowest point at the intersection of the manikin heel and the depressed floor covering with the shoe on the default accelerator pedal position.  Ball of Foot (BOF): A point on a straight line tangent to the bottom of the manikin shoe parallel to the y-plane 200 mm from the accelerator pedal according to the SAE standards.  Pedal Contact Point (PCP): The point where the shoe or foot comes in contact with the pedal.  Foot Angle: The angle measured between lower leg centreline and the barefoot flesh line, i.e. the line connecting the ball and heel of the foot. The foot angle was recommended to be around 87 degrees from an ergonomic perspective.  Accelerator Foot Plane (AFP): A plane passing through the accelerator heel point (AHP) and the ball of foot (BOF) that is normal to the y-plane. (R.W.Roe, 1993) 23 Figure 12 Two dimensional H-point machine Figure 13 Dimension in SAE J1100 that define the interior space 24 2. Methods of Data Collection The following tools were used in various phases of the project from the preliminary; and planning to the concept generation phases. 2.1 Questionnaires A questionnaire is a document with questions with the specific focus on gathering the required information. It was used as a mechanism for obtaining information and opinion about the product or the system. The questionnaire can be used to investigate user needs, expectations, perspectives, priorities, preferences and satisfaction. The questionnaire can be prepared in two ways; one with open ended questions and the other with close ended questions. The open ended question is used to gather information from the respondent in his own way or opinion. The close ended questions are designed with pre- selected answers. The respondent needs to choose the answer based on his opinion. Close ended questions are similar to a forced-answer format however, they are simpler to answer and take less time. The questionnaires can be distributed to a large or small population based on the need for information. The questionnaire format is familiar to most respondents. The information can be collected in a structured way for analysis. Finally, the opinions are evaluated to extract the information. The main disadvantage of the questionnaire is that the respondents may ignore or misunderstand the questions. It could be difficult to represent complex issues in the questionnaire. 2.2 Interviews Interviews are an effective tool for investigating issues in an in-depth way. An Interview can disclose how individuals think and feel about the topic. Interviews can reveal the user‟s desires and expectations about the product. Even sensitive topic which may make some people feel uncomfortable can be discussed in the interviews. The interviewer‟s behavior has a great influence on the interview. The main advantage of interviews is that it is easy to obtain information about the respondents perceptions based on his own words and there is the possibility to ask follow up questions based on the answers from the respondent‟s answers. In some cases, the respondent may exaggerate about some topics. Interviews are time consuming and expensive. The interviewer‟s understanding of the interviewee may be colored by his own perceptions. This could be the main disadvantage of the interviews. (Ulrich & Eppinger, 2000) 25 2.3 Brainstorming Brainstorming is one of the best idea generators that is used to generate as many ideas as possible. Brainstorming is highly effective when done in a team of people. It is the team activity that allows everyone to share their thoughts and ideas about a topic. Interesting ideas are documented as short notes for further analysis and exploration. Brainstorming was done in several phases based on the needs of the project. It was used to promote the creative thought process within the team. The collected information was processed in an effective way. 2.4 Benchmarking The benchmarking process involves “what” and “how” issues. It is a simple process tool used to achieve a thorough understanding of the competitor‟s solutions and how their product functions in different scenarios. The benchmarking process compares the results of two companies and their product in the same market. In some cases, benchmarking was employed to understand the competitor‟s ideas behind their product. It was used to find the strength and weakness of the product in comparison to the competitor. The benchmarking should not limit the scope to its own industry, nor should benchmarking be a one-time event. (Stroud) 2.5 Observations An observation based study is usually performed in a project to gather information about user, user needs or perform specific tasks. The observer can make notes and document the user action and facts for later investigation. During direct observation, the user focuses on specific tasks. The observer can also observe indirectly by viewing video material or tasks. Indirect observation might go unnoticed in a natural environment. Observations are simple, inexpensive and provide firsthand information. The main advantage of observational research is flexibility. The researchers can change their approach or intentions as needed. The main disadvantage is that it is limited to behavioral variables. 2.6 Literature Materials The literature materials study includes background reports within Volvo and ergonomic resource materials from SAE journals and other institutions which address the issues regarding the driving controls. Apart from them internet sources like Trucking Report, Forum and Trucking magazine and Driver Forums like kingsclubb.se; as well as automobile magazines and videos have been used as resource materials for this project. Customer feedback from the sales and marketing department provided some insights from a marketing perspective. 26 3. Data Collection in the Project 3.1 Interviews at Björkäng In order to get firsthand information during the initial study phase of the project, interviews were conducted with ten drivers at a truck stop. The questions were very general and closed ended. The drivers were asked to explain the difficulties and challenges of using the driving controls in order to give a better understanding of the areas that need improvement within the driving controls. The drivers used trucks for long haulage, tank and timber transportation applications. The questions include the driver‟s background information, experience in driving trucks, vehicle applications and usage of driving controls. 3.2 Volvo Demonstration Centre An interview session was conducted with the driver in the Volvo Demonstration Team to get information about the features and usage of the driving controls within the Volvo Product Variants. The session also involved observation based study of driving in different variants of Volvo products, like the FH, FM, FL and FMX, which were tailor made for specific applications. The interview sessions were useful for getting to know Volvo products. 3.3 Scania Demo Centre The visit to Scania Demo Centre was carried out after the visit to the Volvo Demonstration Centre in order to acquire information about the usage of controls in Scania Trucks, which is one of Volvo‟s competitors. The manager of sales within Scania was interviewed in order to gain knowledge about the features of the driving controls and product variants within the Scania portfolio. The session was a discussion and demonstration of the usage of driving controls. The Scania Demo Centre visit was considered a part of the benchmarking process to get information about the competitor‟s products. During the visit, the usage of the driving controls in the Scania truck was reviewed. The steering wheel control was enhanced with the neck tilting adjustment for improving the comfort to the driver. The gear shift lever was replaced by a gear shift stalk in the steering column making it much easier to shift gears without much effort for the drivers. The gear shift stalk gives more room for the driver around the seat and increases the accessibility to the shelf under the bed. The observations from the visit were documented for further investigation. 3.4 Hällered Proving Ground The visit at Hällered Proving Ground contained a combination of interviews as well as observation based study. The questionnaire was prepared with specific questions targeted towards the driving controls in particular to gain deeper insight into the problems and challenges the drivers encounter when driving in both normal and adverse driving conditions 27 (e.g. using the steering wheel and brake pedal while climbing a hill during winter). The questionnaire focused on the steering wheel control, gear shift lever and pedals (accelerator & brake pedals), since Volvo has implemented I-Shift in the FH and FM series which gives the possibility to eliminate the clutch pedals. The drivers interviewed were test drivers with exceptional driving skills and good experience. The interviews were conducted at Hällered in the test circuit while driving the Volvo Trucks (FH & FM). Around 25 drivers actively participated in the session to share their experience in the usage of the driving controls. 3.5 Feature Specialists At Volvo Product Development the features specialists of different driving controls systems, such as Steering System, Gear Shift System, Transmission System, Braking System, and Vehicles Dynamics actively participated in the interview sessions to share the insights on the usage of driving controls and possible improvements. The interviews, carried out with 10 feature specialists, covered the driving controls and measurement systems need to measure the forces required to operate the driving controls. The discussion involves improvements not only from the driving controls but also from the system perspective. 3.6 Ergonomic Feature Leaders The final phase of the pre-study data collection was the conduction of interviews with ergonomic feature leaders within Volvo Trucks. The interviews were made while driving an FH truck near Torslanda, Gothenburg. The driving controls, steering wheel, gear shift lever and pedals were analysed individually. The comments and feedback from the feature leaders were documented. 28 4. Results of the Data Collection The individual results from the interviews and questionnaires were documented in APPENDIX –C and APPENDIX - D The desires and expectations of the drivers were presented in the Kano model to give a holistic approach towards the driving controls evaluation. 4.1 Kano Model The requirements of the future/idealistic driving controls are that they must possess superior features to the current ones. The Kano model was used in order to evaluate the requirements and needs of the drivers from a competitive perspective. Figure 14 Kano Model The Kano model consists of four quadrants with two lines separating them. The vertical line shows the level of satisfaction and the horizontal line shows the level of implementation or fulfilment. The first quadrant represents the performance zone and contains the features that improve the performance of the product. The second quadrant represents the excitement zone and has features that excite the customers but are not fully implemented in the product. The third quadrant represents features which are not favourable or satisfactory to user expectations and needs. These features may be an old feature that after due course of time need to be improved. The fourth quadrant represents the basic features. The product must 1 4 3 2 29 have these features with full implementation in order to satisfy the user needs which are considered as mandatory. The features are shown as spheres in the Kano Graph. The Kano model based study was carried out to present the features in the zones described above. The Kano model for a product shows its features arranged among the quadrants based on user opinion and expectations. The subjective evaluation of the questionnaire and comments from the drivers during the interviews or observation based studies were documented. The input from the interviews was translated to the Kano model by analysing individual responses from the each user / driver about each feature of the product. The features of the product were categorized by the number of responses from the drivers through the ratings in the subjective evaluation; also, the comments of each driver and the ratings were summed up. Based on the maximum responses and individual comments the features were translated to the respective quadrants in the Kano model. For example, a study on the steering wheel in which; 10 truck drivers were interviewed regarding the size of the steering wheel. The steering wheel diameter comes in two configurations, 500 mm and 450 mm. If 7 drivers prefer the 450 mm steering wheel and 3 drivers the 500 mm version, then the 450 mm diameter steering wheel was considered the desired size. At the same time the comments from the drivers were also analysed - larger diameter steering wheels demand more effort and force to steer the truck while a smaller diameter steering wheel requires less effort with excellent comfort. Some questions had mixed responses, so the individual driver‟s comments were examined in order to draw conclusions. The Kano model was prepared for each driving control to show the drivers‟ opinions about the features in the current Volvo FH truck as well as their wants and expectations related to the future driving controls in the Volvo. The features were plotted based on the interviews with the drivers, test drivers, feature specialists and feature leaders within Volvo. Through the Kano models the user expectations and preferences were clearly revealed. 4.1.1 Steering Wheel Control The Kano model regarding the steering wheel is represented below. The user needs and expectations were plotted in the Kano Graph. The steering wheel in the Volvo FH comes with two diameter sizes, (1) 500mm and (2) 450mm. The drivers feel that the 450 mm diameter steering wheel offers more comfort and lower force levels than the 500mm diameter steering wheel, because larger diameter steering wheels demand more work load and force to steer the vehicle. If the diameter of the steering wheel could be reduced to 425mm then it would be considered a “delight” to the drivers. Of course, a reduction in the steering wheel diameter requires that legal requirements be addressed before implementation. In the Kano graph the 500mm diameter steering wheel was represented as 1 in quadrant 3 and the 450mm diameter steering wheel was represented as 2 in quadrant 1 and the proposed 425mm diameter steering wheel was plotted in quadrant 1 and represented as 3. The reduced diameter steering wheel improves steering wheel usage to a greater extent by providing excellent comfort. 30 Figure 15 Kano Model for Steering Wheel The shape of the steering wheel is round. However, feature specialists and feature leaders also considered a D-shaped steering wheel from a design perspective. During the interviews, the drivers were more comfortable with the round steering wheel when compared with the D- shaped steering wheel. Even though drivers were quite excited about the D-shaped steering wheel they were not sure about its full scale implementation. They also considered that the D-shaped steering wheel would not improve steering wheel performance even though it did offer a better view of the instrument cluster. So, the round type steering wheel was represented as 4 and plotted in quadrant 4 and because of the nature of its importance it was considered a “basic” feature. The D- shaped steering wheel was represented as 5 and plotted in quadrant 2 to emphasize its exciting nature but that it was not useful in improving the performance of steering wheel usage. The adjustment of the steering wheel can be carried out in three different ways. Including telescopic and tilt adjustments. The driver can adjust the steering wheel based on his preferences. The neck tilting feature was not available on the old Volvo FH whereas the competitor Scania has the neck tilt function which improves driver comfort without adjusting the seat position. Today, this neck tilt feature is available in the new Volvo FH but not at the time of the studies. The telescopic movement and the tilt movement were represented as 6 and 7 and they were plotted in quadrant 4. They are basic features and are considered mandatory since without these features the users feel disappointment when using the steering wheel. The neck tilt function was represented as 7 and plotted in the 1 quadrant because it delights the customers by offering higher levels of comfort and pleasure. 31 The friction patterns in the steering wheel were available in a plain single pattern made of leather. However, multiple patterns with friction points made of leather could increase the comfort to a higher level in different weather conditions. The single friction pattern was represented as 9 and plotted in quadrant 4 because this feature was considered as basic. The multiple friction patterns were represented as 10 and plotted in quadrant 1 because this delights the driver and provides adequate comfort and friction. The drivers prefer the friction material to be leather because it offers enough support in terms of grip and reliability. Based on the drivers‟ experience they feel materials like plastic and foam are slippery when using the steering wheel. The friction materials were represented as 14 for plastic, 15 for foam and 16 for leather. The plastic friction material was plotted in quadrant 3 because it was considered a poor feature by the drivers in various ergonomic aspects. Foam and leather were considered as basic features and they were plotted in quadrant 4. During the observation based studies, drivers felt it difficult to adjust the steering wheel position between the driving sessions, i.e. during the entry and exit to and from the cab. A few decades back the vehicle steering wheel was rigid and non-adjustable, but now it can be adjusted easily through a tilt away function which moves the steering wheel back to its original position (with the steering wheel adjustment pedal in the Volvo FH and the Volvo FM). The drivers prefer, though, computerized functions like a customizable memory system which could reduce the work load and improve the comfort in the steering wheel usage to a greater extent by assisting the drivers in achieving a comfortable steering wheel position during entry and exit through the push of a button. The adjustment positions can be stored electronically along with the seat adjustments in a database containing the individual drivers‟ profiles. The customizable memory function will delight the drivers and reduce the work load. (This function was not available commercially in trucks.) The rigid steering wheel feature was represented as 11 and it was plotted in quadrant 3 because of the poor feedback from the drivers. The tilt away feature in the steering wheel was represented as 12 and plotted in quadrant 4. It was considered a basic feature. The customizable memory feature in the steering wheel adjustment position during entry and exit was represented as 13 and plotted in quadrant 1 because it delights the drivers and increases the performance factor of the steering wheel, offering comfort and reducing the work load for the drivers in the long run. The driver normally makes 2.5 laps of the steering wheel to steer the vehicle from the left side to the right side and vice-versa. During the driving session some drivers felt comfortable with the stroke while a few drivers would prefer to reduce the strokes to less than 2 laps. If the strokes of the steering wheel were reduced in distribution trucks, then the drivers would have better control in turning the vehicle in dense city traffic situations. The steering stroke with 2.5 laps was represented as 17 and plotted in quadrant 4 which was considered as basic. Whereas, the strokes with 1.5 to 2 laps were considered as performance features and plotted in the line that separates quadrant 1 and quadrant 4. The force levels for turning the steering wheel were similar to the force levels for the strokes. Reducing the force required to turn the steering wheel could benefit the drivers. High force levels were unacceptable and they were represented as 19 and plotted in quadrant 3 which shows their poor characteristics. Low force levels were represented as 20 and plotted in quadrant 4 which shows this feature to be a “basic” feature which cannot be compromised. 32 Figure 16 Key Feature table of Steering Wheel The stability of the vehicle when exposed to wind was an important feature because the drivers feel the feedback in the steering wheel. Manual steering could drastically increase the effort in using the steering wheel and automatic steering or an electronic stability program could reduce the effort and improve the controllability aspect of the steering wheel. Manual steering was represented as 21 and plotted in quadrant 4 because it was considered as basic. The automatic steering against wind was represented as 22 and plotted in quadrant 1 which shows it improves the performance. It also delights the drivers while driving in different weather conditions. Over the past years the vibration from the steering wheel has been reduced in the truck. Now, the vibrations in the steering wheel were almost the same as that of a passenger car and driver comfort in regards to vibrations is extremely good. Higher vibration levels were 33 unacceptable from the ergonomics perspective and they were represented as 23 and plotted in quadrant 3 because of their poor characteristics. Lower vibration levels were represented as 24 and plotted in quadrant 2. A trade-off should be made because maximum filtration of vibrations could eventually reduce the feedback from the steering wheel, so any improvement in reducing the vibrations should be made without compromising on the feedback from the steering wheel. 4.1.2 Gear Shift Lever The Kano model shown below illustrates the features of the gear shift lever. Figure 17 Kano Model of Gear shift lever The Volvo FH comes with three different types of transmissions, (1) manual, (2) automatic and (3) I-shift. The gear shift lever is used mostly for changing gears in manual transmission trucks and in I-shift transmission trucks. In automatic transmission trucks it is only used for reverse and forward functions. In Europe, the demand for manual transmission trucks has declined in the past 5 years at the same time the I-Shift technology has replaced the manual transmission segment. However, the demand for manual transmission trucks has risen in Russia and India according to studies within the Volvo Powertrain Division. During the interviews, the drivers considered the gear shift lever in manual transmission trucks as poor because of the high force and vibration levels, and the long stroke length. So, 34 the gear shift lever in manual transmission trucks was represented as 1 and plotted in quadrant 3. I-shift transmission system was considered as delight as it reduces the force levels and stroke lengths from the gear shift lever. I-shift gear shift lever was represented as 2 and plotted in quadrant 1. I-shift also improves the comfort and performance in shifting the gears for the drivers. The automatic transmission also reduces the effort and work load for the drivers in the long run. Automatic transmission gear shift levers were represented as 3 and plotted in quadrant 2. There was speculation among the truck manufactures in positioning the gear shift lever. In Volvo, the gear shift lever is attached to the seat, in Scania it is in the steering stalks and in DAF it is near the dashboard. The gear shift lever attached to the seats were represented as 4 and plotted in quadrant 3, gear shift controls in the stalks and dashboard were represented as 5 and 6 and they were plotted in quadrant 2. However, initial studies showed that gear shift controls in the stalks would be easy to operate and require cognitive attention to shift gears and the button in the dashboard would also be an interesting area to explore. Every driver interviewed preferred leather as a material to be used in the gear shift knob. Plastic materials were represented as 7 and plotted in quadrant 3 and leather was represented as 8 and plotted in 1. Foam was represented as 9 and plotted in quadrant 4. Figure 18 Feature table of Gear shift Lever 35 The force levels required to operate the gear shift lever were considered an important ergonomic factor. The gear shift lever requiring lower force levels was represented as 10 and plotted in quadrant 1 because it delights and improves performance when using the gear shift lever and the gear shift lever requiring higher force levels was represented as 11 and plotted in quadrant 3. Longer strokes of the gear shift lever were represented as 12 and plotted in quadrant 3. Shorter strokes of the gear shift lever were considered as basic so they are represented as 13 and plotted in quadrant 4. The vibrations from the gear shift lever were within the acceptable range. However, maximum filtration of the vibrations could affect the feedback from the gear shift lever. Higher vibration levels from the gear shift lever were represented as 14 and plotted in quadrant 3 and lower vibration levels were represented as 15 and plotted in quadrant 4 as a basic feature. The drivers‟ opinions regarding the feedback from gear shifting was in the form of (1) noise, (2) display in the instrument cluster and (3) position movement of the gear shift lever. Noise feedback was represented as 16 and plotted in quadrant 2. Display feedback in the instrument panel was represented as 17 and plotted in quadrant 1. Position of the gear shift lever was represented as 18 and plotted in quadrant 4. 4.1.3 Pedals The Kano model for the pedals includes the accelerator, brake and clutch pedals. They were presented in the pictures below. The type of pedal was a key parameter in pedal usage from an ergonomics perspective because it determines the foot position and contact points between the pedal and foot. The pedals are mounted in two different ways, suspended and floor mounted. In the Volvo FH, the accelerator and brake pedals are suspended pedals. In the DAF, the brake pedal is a floor mounted pedal and the accelerator pedal is suspended. The Kano model shown below represents the drivers‟ opinions regarding various aspects of the pedals. The suspended accelerator pedal was represented as 1 and plotted in quadrant 4. It was considered a basic feature. The floor mounted accelerator pedal was represented as 2 and plotted in quadrant 3. The suspended brake pedal was represented as 21 and plotted in quadrant 4. The floor mounted brake pedal was represented as 22 and plotted in quadrant 3. The suspended clutch pedal in manual transmission trucks was represented as 41 and plotted in quadrant 4. The floor mounted clutch pedal was represented as 42 and plotted in quadrant 3. The floor mounted clutch pedal doesn‟t improve the performance factor of the pedal, so this feature was considered as poor by the drivers. The drivers use their shoes/bare foot for pedal usage. Driving with shoes for accelerator, brakes and clutch operation was represented as 3 for the accelerator pedal, 23 for the brake pedal and 43 for the clutch pedal and they were plotted in quadrant 4 because these were considered “basic” features without which difficulties in pedal operation could arise. Comfort while driving barefooted was considered a delight for long haul truck drivers. Barefoot driving was represented as 4 for the accelerator, 24 for the brakes and 44 for the clutch 36 operation. They were plotted in quadrant 3 because they satisfy user expectations and increase the performance factor of pedal usage. Figure 19 Kano Model for Pedals The friction material is laid over the pedal plate to create enough friction when using the pedals. All the drivers prefer the friction material to be rubber. The drivers say the pedals feel slippery when using the plastic friction material. The plastic friction material on the accelerator, brake and clutch pedal was represented as 5, 25, and 35 and plotted in the Kano graph in quadrant 3 because of its poor reviews from the drivers. The rubber friction material on the accelerator, brake and clutch pedal was represented as 6, 26 and 36 and they were plotted in quadrant 4 which emphasizes this as a basic or mandatory feature when using the pedals as seen from the drivers‟ point of view A longer pedal stroke would give sufficient control for the drivers while a shorter stroke could reduce the work load for drivers in the long run. The longer strokes were represented as 7 for the accelerator pedal, 27 for the brake pedal and 47 for the clutch pedal and they were plotted in quadrant 4. The shorter pedal strokes were represented as 8 for the accelerator pedal and plotted in quadrant 1, 28 for the brake pedal and plotted in quadrant 2 and 48 for the clutch pedal and plotted in quadrant 1. The drivers prefer longer strokes over shorter strokes for brakes. 37 Figure 20 Key Features table of Pedals Higher force levels for pedal operation were unacceptable from an ergonomics perspective because they directly affect the comfort and demand more effort from the driver. Higher pedal force levels were represented as 9 for the accelerator pedal, 29 for the brake pedal and 49 for the clutch pedal. The higher position of the pedal makes the drivers feel uncomfortable when resting their foot and it was represented as 11 for the accelerator pedal, 31 for the brake pedal and 51 for the clutch pedal. The higher position of the accelerator pedal was plotted in quadrant 3, the brake pedal in quadrant 2 and the clutch pedal in quadrant 3 based on the drivers‟ opinions. The lower pedal positions could improve the comfort and reduce the work load for the drivers. The lower position of the accelerator pedal was represented as 12 and plotted in quadrant 1 because it increases the performance in pedal usage. The lower position of the brake pedal was represented as 32 and plotted in quadrant 4 because it was considered a basic feature that needs to be fulfilled. The lower position of the clutch pedal was represented as 52 and plotted in quadrant 1 because it improves the performance of the product. 38 5. Measurement Technique for driving controls The following part of the project involves finding equipment and tools to measure the force levels, as the driver perceives them, required to manipulate the driving controls. The main focus was given to finding tools which were easy to use for the ergonomics team. So, different measurement techniques were researched and presented to suit the requirements of the team. The following lists of parameters were useful from the ergonomics perspective. Steering Wheel: Required Force, Strokes, Torque, Number of laps to rotate the steering wheel Gear Shift Lever: Required force and strokes to shift the gears. Pedals: Required force and strokes to depress and release the pedal as it travels along the stroke. 5.1 Steering Wheel Control The force and strokes required for using the steering wheel need to be measured in different road conditions to improve the usage of the steering wheel because the force levels differ when driving on a dry road or in snow and with a loaded or unloaded truck. To make driving more pleasurable and comfortable the force levels and number of strokes need to be measured and improved. The force levels and number of strokes required when using the steering wheel can be measured by the following measurement systems.  Steering Effort Sensor  Measuring Steering Wheel Adaptor  Glove Pressure Sensor  Pressure Mat  Force Gauges  Steering Robot 5.1.1 Steering Effort Sensor The steering effort sensor is a telemetry system, which can be employed in trucks. It was designed to evaluate the steering torque. A small transducer that can calculate the dynamic values from standard steering wheel input was used between the steering column and steering wheel. A particular feature of the transducer is that it has the ability to feed all electrical signals from the steering wheel, so, the functionality can be adapted for airbag as well as non- airbag variants. The steering effort sensor can be easily mounted with a three point clamp assembly. The measurements from the steering effort sensor were reliable and accurate. At Volvo‟s Hällered Proving Ground, the steering effort sensor was used to calculate the forces from the test vehicle in order to measure the steering input from the driver. The test 39 vehicle was tested in different road patterns to analyse the steering behaviour. The vehicle was also tested while climbing a hill, both in normal and 5% gradient roads. The steering effort sensor can be used for ergonomic testing in measuring the steering wheel torque. In Normal driving conditions on a straight road (unloaded truck) Steering wheel torque: 5-10 Nm ((based on measurement test)) In sharp turns on a dry road (unloaded truck) Steering wheel torque: 20-40 Nm (based on measurement test) The steering effort sensor can measure: Steering torque of around 250 Nm Advantages:  Easy to mount  High Accuracy  Minimum effects on the measurement  A modular solution to measure forces from the steering wheel.  Airbag compatible Disadvantages:  Takes time for installation.  The steering effort sensor cannot be used for other controls. Figure 21 Steering Effort Sensor 5.1.2 Measuring Steering Wheel Adaptor The measuring steering wheel adaptor is also a telemetry system that offers continuous, non- contact torque data from a rotating steering sensor to a stationary receiver. The steering wheel adaptor system is a portable system that can be deployed both for air bag as well as non-airbag variants for measurement of steering torque and steering angle. The entire system is easy to mount and use. However, from an ergonomic perspective, the add-on steering Figure 22 Measuring steering wheel adaptor 40 wheel could affect the driver‟s natural behaviour and steering wheel usage which could affect the results. In Normal driving conditions on a straight road (unloaded truck) Steering wheel torque: 5-10 Nm ((based on measurement test)) In sharp turns on a dry road (unloaded truck) Steering wheel torque: 20-40 Nm (based on measurement test) The measurement steering adaptor can measure: Steering torque measurements up to 600 Nm Advantages:  Easy installation of the equipment in the truck  No drag from bearings or slip rings friction  Measure steering torque and steering angle  Digital telemetry to eliminate signal interference  Airbag compatible models are available  The measurement system is used within Volvo Disadvantages:  Expensive  Takes time for installation  Add-on steering wheel affects the natural steering behavior  Cannot be used for other controls 5.1.3 Glove Pressure Sensor The Glove Pressure Sensor is a multi-sensor pressure mapping system with the force acquisition system that consists of a Glove Mat and a Computer Interface. The sensors are deployed in the gloves with a customizable positioning feature and can be mounted in the double sided straps. The sensors in the gloves are covered with a Teflon coated lamination making them much more durable. The Pressure mapping system is ideally used for ergonomic applications including steering wheel analysis and vibrations. The standard configuration has around twenty-four sensors with an accuracy of ± 10%. The sensors are calibrated with the known load calibration jig. The advantage of the Glove Pressure Sensor is that it comes with a remote data logging facility which improves its usage. It can store 4000 scans in its memory when used with a 9-volt alkaline battery power during the Remote Mode. The Glove Pressure Sensor is ideal for measuring the grip forces on the steering wheel. The Glove Pressure Sensor could be an ideal solution from an ergonomic perspective for measuring the forces from the steering wheel. (Ergonomics -Glove Pressure Mapping System) 41 Figure 23 Glove Pressure Sensors In Normal conditions Pressure range in common usage less than 10 psi Glove pressure sensor capable of measuring pressure up to 100 psi Advantages:  20 or 24 sensor configuration allows for detailed measurement  Available in 5 different Glove Sizes  Sensor locations can be modified  Computer interface can store the pressure data from up to 4000 scans  Pressure range is limited to 0-100 psi Disadvantages:  Will measure the gripping force and not the torque from the steering wheel or gear shift lever  Accuracy 5.1.4 Pressure Mats Pressure mats are perfect pressure sensing materials for ergonomic analysis. They are three dimensional and stretchable and made with a Lycra (material). Arrays of sensors are arranged in the mats in order to sense pressure fluctuations. These sensors are extremely flexible and 42 are available in standard and industrial mat sizes, based on customer requirements. The data acquisition system in the pressure mats captures the pressure fluctuation at various points in the mat and displays this information in a digital way. The scanning rates from the pressure mats are relatively quick. Pressure mats are widely use in research and in development of various products. Figure 24 Pressure Mats The smart fabric is elastic and flexible and has three elastic layers with air and vapour permeability. (Ergonomics - Pressure Mats) In Normal conditions Pressure range in common usage less than 10 psi. Pressure mats can measure up to 4 psi. Figure 25 Pressure Mats Advantages:  Customized size  100% fabric which makes it flexible for different applications  Pressure range 0-200 mmHg ~ 3.87 psi  Cost effective 43  Dense array of sensors as per requirements  Minimum thickness  Used for several applications  Uniform pressure distribution  Measure only the gripping force Disadvantages:  Does not measure the steering torque and steering angle 5.1.5 Force Gauges Force gauges are used to measure the force levels in various applications. Force gauges are an economical solution for push and pull testing of up to 1500 Newton with an accuracy of ± 0.5%. The force gauges are compact, easy to hold and rugged in construction with an aluminium housing making the force gauges durable. The three push buttons allow the user to easily select the units of measurement, reset to zero and recall tensile and compressive peak loads. Force gauges are found in ergonomic toolkits as an essential testing solution. Force gauges are either operated by battery or AC power. The handles in force gauges have a good gripping feature with consistent results. The paddle attachments can be changed to flat, curved and square padded mounts to measure the forces in the musculoskeletal joints. Figure 26 Force gauges Advantages:  Widely used force measurement tools  Simple & rugged in construction  Capacity to measure up to 1500 newton  Safe operation  No external power source  Used within Volvo by the Ergonomic Division and the Vehicle Dynamics Testing Division Disadvantages:  Hard to measure forces such as the driver‟s perception of torque  Cannot be used for other controls in an effective way, e.g. Gear shift lever  Measurement error is higher than with sensors 44 5.1.6 Steering Robot The steering robot is a special test and measuring system specifically made for the steering system. The system is designed to feed multiple inputs to be applied with high precision and accuracy to enable very high quality of precision data. The measured data were manipulated with an external data capture system with multi-channel hardware in the vehicle. There are two variants in the steering robots system. The first configuration is called an Omni controller and the second configuration is called a mono controller. The Omni controller has been equipped to allow for multiple actuators so that it can be used for tests that require simultaneous control of steering, braking and accelerator. The mono controller is a low cost alternative to the Omni controller. The steering robot is equipped with a steering column torque sensor, gyroscopes, a transducer and GPS-motion packs with a steering wheel adaptor that needs to be mounted on the original steering wheel which can affect the natural driving behaviour. The user interface system in the steering robot assists the user to define and run the test easily within a short period of time. The processing of the test data can be stored in the data library for future references. Some special tests, like roll stability, can also be performed with the steering robot for automotive certification and validation purposes. Figure 27 Steering robot The main advantage of the steering robot is that the measurements are highly reliable. It is a proven technology adapted by almost 90% of the vehicle manufacturers. However, the limitation is that it is a relatively expensive hardware. (Steering Robot) Advantages:  Installation can be done in 30 minutes  Reliable data  High accuracy  Widely used by automobile manufacturers Disadvantages:  Weight of the motor is heavy 15-19 Kg for trucks  Expensive  Cannot be used for other controls  Does not measure the force levels as the drivers perceive them  Not easy to use  Add on steering wheel affect the results 45 5.2 Gear Shift Lever The gear shift lever is used to shift the gears in the manual transmission truck. The forces and strokes of the gear shift lever need to be reduced for a comfortable driving experience. The following measurement system is used to measure the forces from the gear shift lever.  Ricardo Gear Shift Quality Assessment  Shift Knob Load Cell  Hand Sensor Array 5.2.1 Ricardo Gear Shift Quality Assessment Gear Shift Quality Assessment (GSQA) is equipment for measuring the gear shift quality in changing gears in passenger cars and trucks. The system consists of a hardware and software test system to capture the forces from the gear shift lever in manual transmission vehicles. The GSQA technique is an objective measurement technique developed by Ricardo in order to avoid the subjective measurement technique in shift quality assessment. The gear shift lever characteristics are captured in terms of forces, position and time, then they are converted to perceived gear shift quality. Hence, the measurement technique provides precise and objective results of the gear shift quality instead of subjective results from different test drivers. The GSQA system is used to compare and benchmark the gear shift quality between different systems for further improvement. The Gear Shift Quality Assessment is the best solution for engineers to measure the forces, strokes and position of the gear shift lever. (Bergström & Doverborn, 2009) Under Normal conditions: Gear shifting- the torque required to shift gears is around 100Nm Gear Shift Quality assessment can measure torque up to 300 Nm Advantages:  Best solution for measuring the forces from the gear shift lever  Most successful measurement technique among vehicle manufacturers  Test can be carried out in 4 hours  Highly accurate and reliable  Gear Shift Quality Assessment system is used in the Volvo Powertrain Division Disadvantages  Expensive  Takes time for installation  Only employed in manual transmissions, not even with I-shift because the test lever is connected to the mechanical links in the gear box. 46 Figure 28 Ricardo Gear Shift Quality Assessment (GSQA) installations 47 5.2.2 Shift Knob Load Cell The Shift Knob load sensor has a dummy gear shift knob that replaces the original gear shift knob. The dummy knob is mounted by a supporting shaft gripping adaptor. The gear shift load cell allows real time measurement of the X and Y component force level experienced by the drivers. The dynamic recording of the signals from the sensor is possible through the data acquisition system. The results can be recorded simultaneously to assist the engineers in improving the gear shift mechanisms. Shift knob load cell is used to improve the feel and feedback from the gear shift lever. Figure 29 Gear Shift knob load cell The gear shift knob load cell can handle a force capacity of up to 850N with an over-load capacity of 150% of the full scale capacity. The load cell is used at a temperature of around - 53 to 120 degrees Celsius. Normally, it takes less than 100 Nm to shift gears in a truck. The gear shift knob load cell can be used in the ergonomics division to improve the feel and feedback from the gear shift lever. Advantages:  Measure forces in the X and Y direction from the Gear Shift Lever  Reliable measurement data  Cheaper than the Ricardo gear shift quality assessment system  The gear knob is an add-on to the original knob which affects the measurement data. However, the issue can be resolved by replacing the original knob with the test knob. Disadvantages:  Cannot be used for measuring forces from other controls  Limited to manual transmission vehicles. 5.2.3 Hand Sensor Array The Hand Sensor Array system is similar to pressure mats with an array of sensors in two different configurations, 8 x 8 arrays of 1 inch sensors and 24 x 24 arrays of 5/16 inch sensors, placed inside the flexible mat material. The Hand Sensor array can be used for numerous applications where you grab, grasp or apply a force to a tool or object or handle. 48 The Hand Sensor Array can measure the force that is exerted by each finger as an object is grasped. It is also used in seat as well as back pressure monitoring units in ergonomic seat analysis. The pressure mapping system from the hand sensor array will record the results showing each sensor‟s pressure data. The data gathered can be easily transferred to a spreadsheet to facilitate in depth statistical analysis. It can also be worked with the Lab view program. There is an option to use this as a telemetry system. Figure 30 Hand sensor array The picture above illustrates the pressure changes in the grid when holding the object. Advantages:  Grab/Pull/Grasp/apply force  Available in 8x8 or 24x24 arrays of sensors with 1 inch or 5/16 inch sensors for effective calibration  Color mapping system for each finger  It can measure up to a pressure range of 0-30 psi Disadvantages:  Accuracy with a 10% variable  Not all force aspects that the driver experiences are measured  The mat itself may affect the results based on the method in which the person holds the gear shift lever.  The Hand sensor array can be used to measure forces from the steering wheel and gear shift lever. It cannot used to measure forces from the pedals because it is designed to measure forces in grab/pull/grasp functions and the calibrated pressure range is not compatible with the pedal forces. 49 5.3 Pedals The driver uses the pedals continuously during his driving missions both within the city limits as well as on motorways, so, the forces and strokes expended when using the pedals need to be reduced to improve comfort for the drivers. The following measurement equipment is used to measure the forces from the pedals.  Accelerator Robot  Brake Robot  Pedal Force Sensor  Pedal Force Load Cell 5.3.1 Accelerator & Brake Robots The brake robot is a test and measurement system designed to apply inputs to a vehicle‟s brake pedal for braking characterization and handling behaviour measurement. The brake robots are employed to control the vehicle deceleration or brake pressure with the feedback controller. The brake robot is available in two configurations, one with an on-seat configuration and another with under the seat configuration. The on-seat configuration is optimized to allow quick installation in a wide range of vehicles and it is easy to mount on the brake pedal. The under the seat configuration employs a structured arrangement with a rigid installation unit. Both these systems can be updated to driverless configurations. The forces and strokes expended during pedal travel can be efficiently monitored and optimized with the accelerator and brake robots. The force measurement is in line with the drivers‟ foot input. For ergonomic analysis these robots can be effectively used to measure the forces dynamically under different road conditions and environment. There are several encoders available with the kit in order to measure the forces from brake pedals when used by customers who aggressively apply the brake pedals. Figure 31 Brake Robot 50 The Accelerator robot can be installed in the truck to apply inputs to the gas pedal for vehicle speed, force and pedal travel stroke measurements. The input to the pedal is more frequently programmed to follow the driving cycle or any user profile. The accelerator robot can be used in combination with the brake robot in vehicle testing. The combination can also be upgraded to a driverless testing system. The accelerator robot can be mounted in the driver‟s seat within a few minutes. There is also the possibility to mount the accelerator robot as a driverless system by mounting it under the seats. These accelerator and brake robots are highly accurate and reliable. The data acquisition software provided with the system can easily predict the results. Figure 32 Accelerator Robot The parameters mentioned in the table above are limited to the accelerator pedal robot. The Accelerator robot is a part of a driverless system. The maximum continuous pedal force is approximately 150 N with 70mm arm length and 110N with 95mm arm length. The maximum pedal travel will be approximately 130 mm for the 70 mm arm length and 180 mm for the 95 mm arm length versions of the robot. At 95 mm arm length the throttle pedal speed will be around 300mm/s (AB Dynamics) Normal force in using the pedals is around 100N The Pedals robots can measure forces up to 150N Advantages:  Adjustable to enable easy installation in most vehicles  Vehicle can be driven normally and safely with accelerator robot installed 51  Can control pedal position or follow a speed profile  Highly accurate and reliable data.  Can be operated in autonomous and non-autonomous modes. Disadvantages:  Expensive  Autonomous system affects the driver behaviour in pedal usage.  Cannot be used for other controls  Not easy to use 5.3.2 Brake Pedal Force Sensor The pedal force sensor is used to measure the forces from the pedals. It can be mounted on the pedal through a clamp and fixture arrangement. Wire cables can also be used to tie the transducer to the pedal. The pedal force sensor consists of a transducer which converts the mechanical force into electrical signals. It can measure forces in the range from 110 to 1700 Newton. The results of the force measurements can be interpreted using a standard digital display or with the bar graph predicting the force applied with respect to time or the brake pedal position. (Sensor Developments Inc) Under normal conditions the pedal force is less than 200N In adverse conditions it may reach 450N The brake pedal force sensor can measure forces up to 1700N Advantages:  Strain Gauge based  Lightweight  Low profile height  One piece construction Figure 33 Brake pedal force sensor 52  Error less than 1%  Ideal for automotive applications Disadvantages:  Add-on, the driver will not be in contact with the pedal which could affect the results  Complex and time consuming installation  Cannot be used to measure forces in other controls. 5.3.3 Pedal Load Cell Figure 34 Pedal Load Cell The pedal force load cell is used to measure the forces from the brake pedals. It can be mounted on the pedal through a clamp and fixture arrangement similar to the arrangement in the brake pedal force sensor. Wire cables can also be used to tie the load cell to the pedal. The pedal force load cell can measure forces in a range from 220 to 2200 Newton. (Interface Force Measurement, 2012) Under Normal conditions the pedal force is less than 200 N In adverse conditions it may reach 500 N The brake pedal force sensor can measure forces up to 2200 N Advantages:  Lightweight  Low hysteresis losses, less than 0.05%  Ideal for brake, clutch and gas pedals  Mounts easily on the pedals using straps Disadvantages:  Add-on, the driver will not be in contact with the pedal which affects the results  Higher thickness of the Load Cell affects the results  Cannot be used to measure forces from other driving controls  Complex and time consuming installation and calibration of the load cell. 53 5.4 Results from the Measurements This section illustrates the results of the test to measure the forces from the driving controls. 5.4.1 Forces from the Steering Wheel using measurement steering wheel adaptor The test to measure the steering torque and steering angle was carried out by myself at the Hällered Proving Grounds with the Vehicle Dynamics Testing Engineers in a Volvo FH Truck. The test mission consisted of three driving sessions. The measurement steering wheel adaptor unit was used to measure the steering wheel torque and steering wheel angle with respect to time during the driving sessions. The first two driving sessions were carried out on two straight roads at the testing ground. The last driving session was carried out by driving the truck through sharp 90 degree left and right hand turns in order to measure the steering torque and steering angle. Driving Session: Test carried out on a straight road at the Hällered Proving Grounds Figure 35 Steering angle & steering torque in Driving Session 1 The picture shown above (figure 26) illustrates the results of the first driving session on the straight road at the Hällered Testing Grounds. The x-axis represents the time in seconds, the y-axis scale on the left side represents the steering angle and the y-axis scale on the right side represents the steering torque. The values are plotted while driving on a straight road by steering the vehicle left and right for the given time period. During the driving session the torque reached a maximum of 4.5 Nm when turning left and 4 Nm when turning right. 54 Discussion The driving sessions 1 and 2 illustrate that the measured steering torque was around 4 Nm. when the vehicle was moving on the straight road. The forces were completely dependent on the road conditions and road gradient. The forces may increase if the truck is climbing a straight hill in snow. The steering torque nearly doubled when the truck took sharp, 90 degree turns (see graph driving session 3) due to the force demands from the steering wheel, which are dependent upon the load in the truck and on the road conditions. The measured steering torque provides the driver with feedback about the road conditions, reducing the forces to a minimum value could affect the feeling and feedback from the steering wheel. The measured steering torque does not include the gripping forces from the driver as the driver perceives them. So, this test data could be investigated further using the glove pressure sensor or pressure mats to measure the grip forces when using the steering wheel. Conclusion: The measurement steering adaptor could provide the steering torque and steering angle information for the ergonomics team, however, in order to measure the exact steering grip forces, the pressure mats or the glove pressure sensor should be used. 5.4.2 Forces from the Brake pedal using brake pedal load cell The forces from the Brake pedal were measured by the Brake system team using the brake pedal load cell. As the driver depresses the pedal along the stroke to the maximum stroke length the force amounts to 450 N. The trend shows the forces gradually increasing until 60 mm along stroke. After that, the forces increased drastically from 150N to 300N before the pedal reached a stroke length of 80 mm. The forces nearly doubled as the pedal moved along the stroke from 60 to 80 mm. When the pedal reached its maximum stroke length the forces amounted to 420N. 55 Figure 36 Brake pedal Discussion: Finally, the forces from the brake pedal amounted to 420N at the maximum pedal stroke. If we consider real time brake pedal usage, in the city or on the highway, maximum pedal stroke travel was not common. However, the forces being measured were high. This makes it difficult for the female drivers when using the brake pedal. The measured brake pedal force could be used by the ergonomics team to analyse the forces from the brake pedal and compare the force level with competitors‟ trucks and make necessary modifications to improve the force level in future pedals. Conclusion: The brake pedal load cell provides the pedal force data as the pedal moves along the stroke; however, the results were not reliable from an ergonomics perspective because the load cell was a very thick piece of metal which obviously affected the results. At the same time, during the calibration the driver's foot/shoes do not have any contact with the pedal as the pedal moves along the stroke. 56 5.5 Evaluation of the measurement technique for ergonomics testing Figure 37 Pugh Matrix to select the best measurement technique P re ss u re M at s ar e b ei n g se le ct ed t h ro u gh t h e se le ct io n M at ri x A m o n g d if fe re n t m ea su re m en t te ch n iq u es t h e p re ss u re m at s w as b ei n g p ro p o se d b ec au se it c an b e u se d f o r m u lt ip le a p p lic at io n s. U se d w it h V o lv o t o m ea su re th e st ee ri n g to rq u e an d st ee ri n g an gl e B ra ke p ed al lo ad c e ll is b e in g u se d w it h in V o lv o t o m e as u re t h e b ra ke p e d al fo rc e as t h e p ed al m o ve s al o n g th e st ro ke R ic ar d o G SQ A s ys te m is b ei n g u se d t o m ea su re t h e fo rc es , s tr o ke s an d o th er at tr ib u te s re la te d t o G ea r sh if t le ve r 57 The evaluation of the measurement techniques was carried out by Pugh Matrix to select the best measurement technique to measure the forces from the driving controls. In the figure above criteria were established to define the most important technical parameters to be measured, from the ergonomics perspective, to improve the driving controls. The detailed table that provides information related to the cost and supplier are presented in the (APPENDIX – E) In the steering wheel, the forces the driver perceived while driving were categorized into three types. The steering force, steering torque and the grip force when steering the vehicle. In the gear shifter, the forces the driver perceives while shifting gears were classified into shift force and shift torque to change the gears. Similarly, in the pedals the force for depressing the pedal and the force exerted at different points along the pedal stroke length need to be measured. These are the technical parameters of the driving controls that need to be measured by the ergonomics team. The measurement systems that were investigated were listed and analysed for their capability to measure the necessary technical functions. If the measurement system can measure the technical parameters then it would be represented as „positive‟ and if it does not have the capability to measure the technical function then it would be represented as „negative„. The measurement systems were rated with positive and negative scores. Then the positive and negative scores are summed up together to find the net score. The net scores were counted and compared with other measurement systems. The ranking was made with the final scores. In the figure, the measurement systems were rated based on their capability to measure the required technical parameters. As discussed earlier, a positive sign was used to represent the possibility to measure the forces from the technical parameters. And „negative‟ sign was used to represent the measurement system‟s inability to measure the technical parameters. Most of the measurement systems can measure the technical parameters of either the steering wheel or gear shift lever. Among the investigated measurement systems the pressure mats have the capability to measure the forces from all the driving controls for ergonomics analysis and they were ranked „1‟ because of the possibility of using them in different applications as well as for being cost effective. Recommendation The study of the measurement systems best suited for measuring the forces from driving controls illustrates that pressure mats were the most effective and reliable measurement technique for ergonomics testing and verification. The pressure mats were available in customized si