Development of Exoskeleton for Loggers: User Centred Design of Passive Lower-Back Support for Motor-Manual Tree Felling, in collaboration with Husqvarna AB

Abstract

This thesis was conducted in collaboration with Husqvarna AB, which is one of the biggest providers of products for forestry applications in Sweden. Aiming to be at the forefront of technical innovation, exoskeletons was seen as an area of interest for the company. The aim of the project was to investigate the possibilities of using an exoskeleton as a facilitator for prevention of musculoskeletal disorders (MSDs) for loggers performing motor-manual forestry work using chainsaws. User evaluations and literature studies showed that MSDs in the lower back are frequently occurring among the user group, materializing as pain. Lower back pain can stem from a number of issues, where strain or spasms of back extensor muscles is common. The lower back is mainly affected by body posture and the physical load when performing work tasks with the chainsaw, frequently executed with a forward leaning posture and standing with bent legs. The tasks with the highest risk of postural strain are felling and limbing, where the working posture in combination with duration is classified as high ergonomic risk. The project follows the Double diamond design process with great emphasis on the discovery and development phases. The theory of emotional design was implemented with behavioural design as the main focus and with the aim to achieve user acceptance by influencing via the visceral and reflective design levels. The final design concept is a spring loaded passive exoskeleton supporting the lower back of the wearer, focusing on lowering back extensor muscle activity. The functionality is facilitated by using elastic bands as they can be worn close to the body across the back, allowing free mobility along the side areas of the body. The solution consists of a torso harness, a tool belt and two leg supports with inter-connectivity. The torso harness and tool belt use existing Husqvarna equipment as a base, modified to suit a forestry context and to facilitate the function of relieving strain on the lower back of the user. While adaption of ergonomically correct working postures remain the most important factor for preventing MSDs and pains among loggers, it is concluded that an exoskeleton product could potentially give further support to the user and help prevent pains from materializing.