Exoskeleton for forestry workers

Development of Exoskeleton for Loggers

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

The full report can be view here: https://odr.chalmers.se/handle/20.500.12380/305484

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.

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.

Functionality

The core functionality of the H-EXO is provided by elastic bands attached to straps placed on the back, connecting the torso and upper legs. The elastic elements function as artificial external muscles, giving relief to the back extensor muscles during forward bending. Kinetic energy is stored in the elastic bands during bending, where the bands expand. The energy is then 'released' as the body is returned to a straight position. The bands thus act as a spring mechanism, making the product self-reliant with no further addition of energy sources.

The clasps attached to the front side of the shoulders are designed to enable activation and deactivation of the elastic bands. This functionality allows the exoskeleton function to be activated at will, to allow for deactivation during transportation and work pauses when the user is not in need of physical assistance. The strap connected to the spring gets activated when the clasp is pushed down/forwards and the elastic band gets stretched. The reasoning behind this function is to allow the user to move freely when not actively working, and avoid having the spring mechanism from the harness acting on the body. The environment in which loggers operate varies widely and can be demanding, where there might be dense vegetation and uneven ground which emphasizes the need of mobility for the user. While the exoskeleton is in deactivated mode the logger can walk and navigate in the forest environment without any impact from the spring mechanism.

Process

The project was conducted using the double diamond with the main focus on the discovery and development phases. The discovery phase involved a literature study, benchmarking, survey, observations and interviews. Ergonomic evaluation was conducted using REBA, OWAS, KIM I and KIM III. The development phase included sketching, prototyping and 3D-modeling. And the concepts were evaluated via interviews and a focus group.

A patent for parts of the final concept is currently pending.

Team Member: Anton Widell