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- PostOn the CFD Modelling of Monolithic Catalytic Converters using FIDAP for Axi-symmetric, Isothermal, Incompressible and Turbulent Flow(1994) Grönstedt, Tomas; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
- PostAn Experimental Study of the Flow Around the Front Wheels of a 20% Scale Car Model in Moving Ground Conditions(2004) Christoffersen, Lasse Malmkjaer; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThis diploma work is based on two parts. The first part is a study of the equipment for the Chalmers wind tunnel with the aim to specify what needs improvement in order to setup a fully functional aerodynamics laboratory. Further it includes the conceptual design of a sting that should carry a car model when using moving ground. The second part contains a study of the flow around a wheel in a wheel house cavity in moving and stationary ground condition. The aim of the study was to try to give further explanation to the change in the drag coefficient so often reported from such studies. The conclusion of the study was somewhat fuzzy owing to the pour function of the experimental equipment. However some good flow visualizations came about that lead to a better understanding of the flow field around the front wheels. The experiment was carried out in the Wind tunnel of Chalmers University of Technology.
- PostA Study of Knee Injury Mechanisms in Car-to-Pedestrian Impacts Using(2004) Yao, Jianfeng; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThe aim of the master thesis was to study the knee injury mechanisms in an impact condition associated with car-to-pedestrian accidents, analyse the influences of the physical parameters on the lower extremity impact responses, and predict the injury risks under different impact conditions. The study also contributed to the evaluation of the validity of the EEVC legform model and a FE model of the lower extremity. For the purpose mentioned above, two substitutes of lower extremity were simulated by using MADYMO MBS-FEM coupling technique and RADIOSS program respectively. One was the EEVC legform model, another the human lower limb model (LLMS) developed by MECALOG in France. The knee and leg injury mechanisms were first investigated using EEVC legform model. The influence of car front structures, upper body mass and presence of tibia fracture on the calculated injury parameters was investigated using total 24 simulations. The LLMS model was refined and evaluated using published cadaver test data. Six simulations of bumper-to-lower extremity impacts were carried out under various loading conditions including two types of car front models at impact speeds of 20 and 40 km/h. The results from LLMS model simulations were analysed and compared with the results from simulations of EEVC legform impacts in terms of injury related parameters: knee shearing displacement, knee bending angle and impact forces. The results showed that the shearing and bending injuries of the knee joint were two important injury mechanisms associated with car-to-pedestrian crash accidents. During the impacts, the major parameters influencing the lower extremity injury severity were bumper stiffness, bumper height and impact velocity. It was confirmed that the upper body mass had certain influence on the knee bending angle and shearing displacement. The tibia fracture had a significant influence on the knee joint injuries. The results also showed that the EEVC legform model was much stiffer than LLMS model for both knee joint and tibia. Further improvement of EEVC legform biofidelity was suggested. The rupture mechanism of the soft tissues in the knee joint was recommended to be simulated in the LLMS model.
- PostStudy of steering effects. Virtual testing of front suspension of heavy trucks.(2005) Axelsson, Erik; Olsson, Mattias; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThe truck suspension works today in many different environments. Demands on good handling are high and need to be fulfilled in all possible situations. Good handling needs good control on steering effects. These effects can both be unwanted like brake and bump steering or wanted like understeering. Methods used at Volvo have changed by time from simple geometry sketches and knowledge from test-driving studies to analysis on non-linear FE-models. The department for front suspension and steering at Volvo 3P has developed a non-linear FE model for virtual testing of the front suspension and steering. Steering effects considered in this report are bump, brake and roll steering, with the main emphasis on the last mentioned that has not been previously modeled. The aim of this thesis is to enhance knowledge of steering effects phenomena at Volvo 3P through in-dept studies of output from a complemented and improved modeling of the front suspension steering effects, and to map parameters influence on induced steer angle due to bump, brake and roll load cases. Our approach has been to develop and enhance the load cases of the considered steering effects. The load case representing roll has been broken down into separate parts in order to make the analysis easier. The in-dept analysis of the load cases then gave us a foundation to choose the parameters of the front suspension to be included in the parameter study. The parameter study was then executed with the help of several UNIX, Python and Matlab scripts. The outcome of the steering effects study showed some not well known phenomena, such as twist of the axle beam. The result from the parameter study confirmed the result from the study of steering effects and gave a good picture of the influence of parameter changes. Our conclusion is that modeling of load cases is crucial to get a trustworthy output and that an advanced FE model such as the present is necessary.
- PostTowards modelling of motion of ground vehicle with active suspension(2005) Chantre Fortes, Samu Almeida; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThis master thesis work shows the capability of active and fully-active suspensions to improve the performance of a ground vehicle. The study is based on showing substantial vehicle improvement gains in comparison with the performance of standard vehicle suspension system. Ride comfort (sprung mass acceleration) and handling (tire displacement) are the two main criteria used to evaluate these improvements. Remarkable improvements over the passive suspension are demonstrated base on vehicle simulations and analyses. In this work, the quarter car model is used and has been implemented and simulated in two software environment, MSC.ADAMS and Matlab. The only input is the road profile that introduces vibration to the system. Two road profiles are used: 1) off road and 2) smooth road. First the passive suspension is simulated using the MSC.ADAMS model. At this stage of the work the response of the passive suspension according to road profiles is analyzed and improved in order to get the best suspension setting for each road profile. The next step is to simulate the passive suspension with the founded best settings using MatLab model. This procedure allows the validation of the results achieved with MSC.ADAMS model. Also the values achieved by others researchers are used to verify the accuracy of the results. At this stage of work important conclusion is that for each road profiles a specific suspension setting must be used if one wants to maintain good vehicle performance. Therefore smart suspension that can change their characteristic continuously is a priority in this work. Next step is the implementation of the active and fully-active suspension in MatLab model were control law is used to predict the actuator force. It is assumed that the system is linear; hence the control law is based on a linear state feedback controller where the Linear Quadratic Gaussian regulator, LQG, is used to calculate the feedback gain matrix minimizing the cost function used to calculate the actuator force. It is commonly assumed that the commanded force is produced accurately. Simulation is done without considering the actuators dynamics. The final step is to simulate and analyze the improvements brought by the active and fully-active suspensions. This part of work is performed using the Matlab. Again the best suspension settings found earlier for the two different roads are used in these simulations. For the fully-active suspension apart from the actuator only the spring coil is used whereas in the active suspension both the spring and damper are used in parallel with an actuator. As expected the results show considerable improvements of vehicle ride comfort particularly for the off road. The road handling improvement is minimal in both road profiles. In order to improve the handling these systems must suppress the motion created by the wheel-hop frequency situated at high frequencies values creating higher reaction forces deteriorating the improved ride comfort. Nevertheless, these systems still brings in improvements when particular driving condition arises, for example: reducing pitch motion in acceleration and braking, minimizing rollover in cornering and maintaining the ride height for payload compensation.
- PostInterior design of a volume model(2005) Duran Murrieta, Daniel; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsEver increasing market competitions pushes automaker to reduce their design cycle and use common components in order to reduce cost. A need to evaluate how the design could look at a very early stage is imperative. The aim of this thesis is to provide the reader with a direction on how to design an interior model, where different seating positions can be used. The goal is to try to use as many CO (Carry Over) components as possible yet achieving completely different looks. Instead of using the traditional approach where all the studies are based on a design, the approach taken is by establishing a bandwidth in which the design could work. The traditional approach has been used for several years and it has been shown to be slow and expensive. By introducing the bandwidth design the goal is to reduce the iterations needed to get a design to work, which will reduce both time and money investments. The term hard point will be introduced and some of the most important hard points on the design of an interior will be discussed. The hard points where established by using UG (Unigraphics) which is the CAD program used by SAAB. In addition to this CAD program Alias and Clay work was done to evaluate all A surfaces (all visible surfaces within a vehicle). Due to the confidentiality of their nature this surfaces can not be included on the thesis, and therefore an explanation on how the hard points where used to evaluate the surfaces will be given. In addition to the above mentioned programs Product Vision was used for illustration purposes. It is important to highlight that in order to establish a hard point a lot of issues have to be taken into account. Some of them include a subjective analysis which can only be acquired by years of automotive experience; hence for each of the hard points established discussions within the different departments where held until an agreement was reached. The result of the work of this thesis was the establishment of two interior volumes which hopefully one day will reach the production market. The work has just started and further hard points are needed to bring the product to life. Further development of hard points is needed especially as the project advances into different stages, the methodology has just begun and how to implement it into the different stages will determine how accurate the parts come out to be.
- PostDesign of Front Cab Suspension System for a New Generation Volvo Trucks(2005) Monroy, Oscar; Cerci, Tekin; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThe cab suspension of a truck constitutes the connection of the cab to the frame. Its main task is to suspend the cab from harmful excitations coming from the frame since the life of cab structure and the comfort of driver is mostly dependent on these vibrations. In modern trucks, the entire main truck manufacturers use four-point cab suspension, which means cab, is suspended in both front and rear side of the cab. The main task of this thesis work is to create different solutions to cab suspension problem of the new generation (NG) trucks. The design and development phase of NG trucks is continuous till the product is launched which results in change of boundary conditions during the thesis project. This report complies with the changes made till January 2005. The thesis work starts with the product planning phase, where all the requirements of the product are established, analysis of the main competitors is done and new ideas are generated through brainstorming sessions. The second part is composed of the development phase, where the ideas generated in the product planning phase are developed into final products satisfying the targets set in the planning phase. In this part of the thesis work, two different approaches to the problem are introduced. The first approach is mainly concentrated to solve the problem different suspension mechanism, namely instead of using conventional suspension mechanisms, other alternatives satisfying the requirements are analysed. The second approach is mainly concentrated to change of suspension type, which proposes to use different solutions other than conventional air or mechanical spring types. Results of the development phase leads to different solutions applicable to new generation trucks. As the final steps, all solutions are compared with the requirements as well as the current solution. In conclusion, there are two different mechanism change proposals and alternative suspension type changes which comply with all the requirements for the product, which can be adapted for future design changes.
- PostComputation of the Crack-Driving Force in Elastic-Plastic Materials - A Comparative Study(2005) Tillberg, Johan; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsIn fracture mechanics a material force, or the crack-driving force, is defined as the energy release rate due to a small variation of the position of the crack tip. For material, that does not dissipate energy due to irreversible (dissipative) mechanisms, the material force and the classical J-integral are equivalent. The main advantage of using the material force is that it is defined even in the case of elastic-plastic response. In this thesis, two numerical examples are studied. The first example is a central crack in a plate with prescribed stress on the boundary, where linear elastic fracture mechanics (LEFM) is used to obtain the crack-driving force. The results show that the computed stress-intensity factor coincides with the analytic result. The second example describes an edge crack in a plate with prescribed displacement on its upper and lower boundary. In this example, non-linear fracture mechanics (NLFM) is used, in terms of the computation of the material force, to obtain the crack-driving force. The results show that the elastic-plastic material response has significant influence on the investigated measure of the material force.
- PostFinite Element Rail Vibration Dynamics - Ground Improvement with Lime-Cement Columns(2005) Berg, Sebastian; Larsson, Martin; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsGround vibrations from trains are a major problem for people living close to railway lines. When a high-speed train passes at an embankment constructed on soft soils resonance effects can appear and cause high amplitude vibrations for the surrounding environment. To design appropriate railways without expensive costs on field tests it is important to create models and simulate the effects of countermeasures for the embankment and the surrounding soil. In this thesis countermeasures with Lime-Cement Columns have been integrated into a 3D FEM90 train-induced ground vibration model developed by the Computational Dynamics Group at Chalmers. Three types of configurations of Lime-Cement Columns have been studied: 1. A case with columns straight under the rails (LC-Column Model). 2. Leaning columns under the embankment (LLC-Column Model). 3. Barrier, where the columns is placed outside the embankment. The column configurations has been evaluated and compared when an X2000 train pass in velocities between 140 km/h and 300 km/h. The effect of the angle for the leaning columns has been evaluated as well as the influence of the diameter and the strength of the columns. At the track the simulations demonstrate the importance with columns near the rail when reducing dynamic amplifications at the track. The simulations also show that the effect of the countermeasures in the soil is dependent of the critical velocity of the system. For low train velocities below the critical the columns straight under the track is the most effective. At higher velocities the leaning columns works better regarding the vertical amplitude in the soil. The leaning column angle shows that a higher angle has good effect at the track. In the soil a high angle has opposite effect.
- PostA Numerical Study Of Fibers In A Fluid Flow(2005) Mark, Andreas; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsIn the thesis a sphere fiber model is developed and implemented to study flocs of flexible and stiff fibers in a shear flow. The spheres in the model are bounded by springs and the bending force is proportional to the angle between the connected spheres. Fiber-fiber and fiber-wall interactions are included to study flocculation in different geometries. The hydrodynamic interaction is modelled by Stoke drag, which is dependent of neighbouring spheres. To study different kinds of fibers, flows and walls the simulation parameters can easily be changed. The model do not include twisting torque and momentum transfer from fibers to fluid and assumes that the flow is a low Reynolds number flow. The backward differential and Runge-Kutta methods are implemented to solve the equations describing the fiber system, where boundary conditions, step-size and tolerance are dependent of the model. The two methods are compared and the Runge-Kutta method is determined to be the best suited method for this problem. Simulation examples are done to study flocculation in shear flow. Simulated rotational periods and rotation velocities of a stiff fiber are compared with Jeffery's simplified equation. The simulations is showed to follow Jeffery's results but is affected by the inertia included in the model. When inertia effects are made smaller the simulations better approximates the solution of Jeffery's equation which does not include inertia. The simulation program is developed under linux and all the code is written from scratch (except the math library) under Dolfin name spaces in C++. The results in the thesis show how flocculation occur and that the fiber simulation program successfully model fibers and fiber flocs in a fluid flow.
- PostDevelopment and Validation of Mathematical Model to Optimize a New Pedestrian Sensor Concept(2005) Huang, Sunan; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsABSTRACT - EEVC proposed the pedestrian headform impact test procedure to minimize the risk of head injuries in passenger car to pedestrian collisions. To meet the test requirements one protective system was developed and named Active Hood. It consists of a hood that is lifted in the rear end in case of a pedestrian impact. To activate it a contact sensor placed in the bumper is needed. An important issue of the sensor system to be solved is the temperature sensitivity arising from the unstable stiffness of bumper foam with the variety of environment temperature. A new concept pedestrian sensor has thus been developed and it should be less temperature dependent. This study aims at development of mathematical model of a new bumper system. Then the model will be used to optimize the new pedestrian sensor concept so as to solve the temperature sensitivity issue. Based on physical tests with simplified experimental bumpers in Autoliv Research, three Finite Element (FE) experimental bumper models have been developed in a first phase. Using these experimental bumper models, 11 physical tests were simulated to obtain the valid material parameters for a production bumper. Then a detailed production bumper FE model has been developed using validated material parameters. The standard production bumper model was evaluated according to EEVC WG17 test procedure requirements. Two aspects of improvement were then made on this model for the purpose that the improved FE bumper model can meet the requirements of the EEVC WG17 legform test procedure. Based on the improved bumper FE model, the new pedestrian sensor has been introduced in bumper foam and optimization has been carried out with varying concept sensor parameters. According to the optimization analysis, the smaller sensor tube diameter will lead to a better result. In all the tested parameters, the 25 mm diameter of sensor tube with 2.5 bars initial air pressure can give a high distinction of sensor signals when impact with objects of different masses. The signals from this FE model are less temperature dependent, which provided a mathematical model and background knowledge for a pedestrian sensing system design.
- PostSimulation of effect of different chassis set up on dynamic performance of a passenger car.(2005) Ahmed, Shamim; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
- PostDevelopment of a subframe for 20 feet ISO containers on rigid trucks(2005) Hatesse, Eric; Krona, Johan; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThis report presents the achievements of the Master Thesis Work that has made at Volvo Truck Corporation. The task consists in developing a subframe that will be fitted on a rigid truck able to carry 20 feet ISO-Containers. The main purpose of the subframe is to support the truck chassis while attaching the container by lock members mounted on the subframe. The design criteria for the subframe are that the construction should prevent rattling, limit high torsion to the chassis, and withstand the forces created from a fully loaded container. The result of the thesis consists in four different solutions, two of which grew from a totally new design, while the other two are based on design ideas from an already existing solution used at Volvo Trucks for carrying swap bodies. The recommendation for the future is to choose for further develop the design concept based on the existing solution for swap bodies as a first step. In the next phase the concept based on totally new design should be fully developed and analysed from manufacturing aspects.
- PostToeards modelling and optimisation of semi-active suspension. Magnetorheological damper and magnetostrictive electric generator.(2005) Andersson, Christian; Stojanovic, Bojan; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsMagnetorhelogical technology is a promising method for avoiding conflicts associated with optimisation of vehicle suspensions. With MR dampers, the damping coefficient can be varied by applying relatively small magnetic fields. Multi-criteria optimisation was conducted to investigate the potential performance improvements obtainable with this technology. Vehicle simulations were implemented in Matlab using a quarter car model, after which the results were verified in Adams. Apart from performance, the electric current necessary to sustain the system was estimated. Additionally, an attempt to convert mechanical into electric power was made using a magnetostrictive electric generator, or MEG. An adaptive structure consisting of a rack and pinion and a cam was designed to amplify the frequency of excitation, and thereby enhance the MEG s conversion efficiency. Finally, its effect on passenger comfort was investigated. The simulations showed that MR dampers can have a positive effect, particularly to counteract motion caused by load shifts. Installation of the harvesting device was found to have a negative influence on passenger comfort, and thus requires further development.
- PostModelling and Design of an Air-cushioned Hitch for Passenger Cars(2005) Gutierrez, Enrique; Lemoine, Julien; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsComfort and road handling are two mains areas in which car engineers put a lot of efforts. Suspensions are designed to offer the best compromise between well-being and safety. However, leisure market is appreciably increasing those years and more and more people use their car to carry features as boats, motorbikes or caravans. Extra weight is brought on the rear axle of the towing vehicle, the front one tending to lift. Thus, suspensions efficiency decreases leading to nuisances in comfort or handling. The two major motions that have to be controlled are pitch and bounce. The first represents the rotation of the car around its transversal axis, the second deals with the vertical displacement of the vehicle. The purpose of the thesis consists in modelling and designing an air-cushioned hitch that will reduce vibrations on both car and trailer. This kind of product already exists, especially in the truck field. Indeed, many trucks use a system called fifth wheel that absorbs energy due to the motion of the trailer. Then, the challenge of this project is to design a system applicable on common passenger cars and determining adequate structural parameters values for suspension features. MSC.ADAMS/View and MSC.ADAMS/Insight are the softwares used in this purpose. A simplified model based on mass-spring-damper system is implemented and allows obtaining suboptimal stiffness/damping for the air hitch. This simulation is also a way to get insight into the performance of the product. Design development has been established using Solidworks. All parts are created respecting space constraints and regulations and assembled to give the final product. FEM analysis is performed to check if strength requirements are fulfilled. One of the results from this work is a document with dimensions and characteristics of the final product that can reduce about 30% of vibrations. The air hitch is aimed to be industrialized. However, rig tests and manufacturing cost analysis have to be achieved in order to validate design choices.
- PostOptimization of Chassis Design Parameters, Braking and Stability Analysis of Autonomous Vehicles on Elevated Guideway(2005) Hann, Hoo Chee; Rehan, Mond; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsIn the development of the PRT (Personal Rapid Transit) systems every detail, ranging from autonomous vehicle dimensions to dynamic performance in the longitudinal (acceleration and braking) ride (vertical and pitch motions) and handling require rigorous study and research to make the system successful as their counterparts (normal cars) moving on the roads. The supposedly enclosing guideway can make analysis more intricate with its confounding surface properties and geometry. The thesis work here proceeds with the dimension estimation the context of which is to propose the autonomous vehicle geometrical dimensions including the wheel base, track width and height, the centre of gravity height which is certainly the most recognized parameter influencing almost all the vehicle performances. The dimension estimation is divided into four major steps. The modus for the dimension estimation is to employ optimized performance equation, for instance optimal braking equation, vehicle dynamic index, rollover threshold and estimation of vehicle size with given centre of gravity height. Continuing with the performance analysis, braking ability of the vehicle was thought to be principal reason behind the stability and hence analyzed subsequently. The optimal braking performance of the PRT system is analyzed and the suitable braking system conforming to the requirement is proposed. For further considerations on the chassis design, the wheel loads especially the amount of load transfer have been discussed in detail with given vehicle data and operating conditions. Also, another important criterion is the risk for overturning and sliding of a vehicle due to wind disturbance, especially the vehicle with high centre of gravity and narrow wheel track during standstill on banked curves. A simple analysis of the guideway design has been proposed with given operating conditions, which is regarding the maximum allowed guideway deflection, support columns spacing and the vehicle top speed. Ride performance as the other major area regarding the human comfort is analyzed and the required suspension stiffness and damping of the autonomous vehicle is estimated using ADAMS. Looking in the fact that the PRT system in discussion here travels on a smooth metallic guideway with nominal surface roughness elevation, two other combinations namely, vehicle without suspension system and vehicle without suspension system but the springs beneath the car seat is analyzed on ADAMS view. At the end the future work is discussed and the report concludes with the discussion and references.
- PostMounting System Design for Drive Trains of Hybrid Electric Vehicles(2006) Kataria, Amit; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsAlthough individual mobility represents a general desire of today s society, the role of passenger cars within actual traffic systems is discussed more and more controversially. One main reason is the carbon dioxide content of the exhaust gas emissions which is considered to contribute to global warming. This situation led to a renewed interest in hybrid vehicles which combine at least two types of propulsion systems. Generally an Electrical Motor (EM) is integrated between Internal Combustion Engine (ICE) and Gear Box (GB). The resulting Hybrid Electric Drive Train (HEDT) differs from the original one with respect to mass distribution, inertia moments and cg position, for example, thus requiring an adaptation of the mounting system in order to maintain a low vibration and noise level inside the passenger cabin. A powertrain mounting system has a significant effect in the noise, vibration and harshness (NVH) as well as ride and handling characteristics of a vehicle. Lighter vehicles and increasing customer demands for a vehicle refinement and dynamics are placing a greater emphasis on the optimization of the position, stiffness and damping characteristics of the mounts. A modeling approach is described, using the multibody dynamic simulation package ADAMS/ Engine, which allows the compromises between conflicting design requirements to be assessed rapidly and an optimum specification reached. The use of time domain non-linear approach allows the motion of the powertrain and mounts deflection to be assessed under normal and extreme driving conditions. Model of the major engine components allow the forced response of the powertrain, to low frequency engine excitation, to be predicted in order that idle shake and, via the use of transfer functions, interior vibration may be assessed. In addition the rigid body modes of the powertrain can be predicted and separated from known vehicle and powertrain forcing frequencies for good vehicle dynamics and NVH. Finally, Active Vibration Compensation methods are investigated and a piezo active controller is designed and tested in laboratory. This thesis deals with the development of a controller that receives inputs from a sensor and accordingly generates a response which in turn is fed to the piezo actuators. Since the road conditions vary continuously, it is necessary for the controller to generate a very quick response. Besides reduction in the weight and volume, this "Active Method" offers a high reduction in vibrations in the low frequency range.
- PostModelling of Vacuum Holding Force in Pick-and-Plce Machine(2006) Anastasovski, Marjan; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsPresently manufacturers of surface mount assembly machines used predefined solutions for vacuum nozzle selection and acceleration level according to the package size. Usually this results lower production efficiency than maximum possible. The focus of this research is to make pick-and-place machines more intelligent in a way to determine operational parameters based on the input values of vacuum level and package size. Based on experimental data, mathematical model was developed which from the input values of vacuum level and package size, determines operational parameters, such as nozzle selection and acceleration level, hence minimizing operators influence. MYDATA MY9 pick-and-place machine used in this work is equipped with two placement units; single and multi nozzle unit. Different nozzle materials are used at the nozzle tip such as plastic, rubber, ceramic and steel. The model is based on experimental data regarding Area of Contact, friction coefficient, acceleration, and off centred pick-up, after which compensation factors are included into the basic Newtonian law. Using MATLAB® script based on the mathematical algorithm, a case study was done to validate the model. The solutions regarding nozzle selection and acceleration level, obtained from the case study, proved increase in operational range of the nozzles, resulting with 8% to 11% lower cycle time for PCB assembly.
- PostControl Strategies for Electronically Controlled Limited Slip Differentials(2006) Carlén, Mattias; Yngve, Simon; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThe objectives of this master thesis work were to develop control strategies for electronically controlled limited slip differentials with main aspect on the yaw rate. The control strategies were developed in Matlab/Simulink with the use of VehSim, GM version of the commercial product CarSim. An ideal electronically controlled LSD (eLSD) and a new invention called Direction Sensitive Locking Differential (DSLD) were evaluated. A bicycle model was derived to use as a reference model and an extended model was derived to show the influence on the vehicle behaviour from the differential. The control strategy implemented for the eLSD combines logic with a variable PID-controller and the strategy for the DSLD was based on logic. To evaluate the control strategies, four different driving scenarios were simulated. The results from the simulations are that with the control strategies developed in this master thesis work the vehicle’s stability, traction and cornering performance are enhanced significantly.