UC Berkeley

Overexertion is a common cause of work related musculoskeletal disorder (WMSD) in the modern industry. The shoulder is one of the most susceptible joints to injury and requires the longest amount of recovery time to heal, currently accounting for about one fifth of the total cost associated with WMSD’s. Exoskeleton technology has the potential to provide beneficial augmentation to workers in many industrial fields. A strategic application of support reduces the forces exerted by the operator, potentially decreasing risk of injury and increasing productivity though the added capability. Their mobility allows for application in environments where a static aid is not feasible due to constantly changing surroundings, such as in construction or shipbuilding, or due to high costs of modifying an established manufacturing line for ergonomic benefit. As the field of shoulder supporting exoskeletons begins to emerge, little is known about the effects these devices have on operator’s effort and productivity.

This work introduces a novel design for a shoulder supporting exoskeleton as well as a preliminary evaluation of the device’s effects during common workplace tasks. The exoskeleton builds off of the success of a trunk and a leg supporting exoskeleton developed at the UC Berkeley Human Engineering and Robotics Laboratory. A passive actuation strategy is presented to augment the torques about the shoulder due to the gravitational forces on the arm and a handheld tool for a variety of workplace tasks and individual preference. A modified iso-elastic base profile divides support into a working and non-working range of motion and can be modified in its amplitude, on/off state, and gravitational offset. A biomimetic frame design provides the support and motion necessary to apply the supporting torques across the shoulder joint for a majority of worker dimensions. Couplings at the arm, shoulders, and hip comfortably secure the frame to the body in a familiar manner that is easy to use while glenohumeral, scapulothoracic, and spinal degrees of freedom allow for relatively unrestricted mobility. A modular approach to combining the shoulder supporting exoskeleton to neck, trunk, and leg assisting devices is discussed to accommodate tasks with risk of injury to multiple joints. A combination of two, three, and four devices is presented for commonly occurring tasks, comprising what is probably the most sophisticated workplace exoskeletons that has been designed to date. A controlled study has been conducted to assess the shoulder supporting exoskeleton’s effects on effort and usability for a common set of workplace tasks and tools. Results show a substantial and desirable decrease in muscle activation for all conditions.