Objective The aim of this study is to determine the effectiveness of using a leg support exoskeleton (legX) in different modes on simulated work tasks which emulate real-world job tasks. Background Prolonged kneeling and squatting tasks increase the risk of work-related musculoskeletal disorders at the knee in industrial occupations. Methods We evaluated legX capable of spring assistance throughout one’s range of motion and/or locking support at a fixed angular position. Participants performed a dynamic panel task, alternating between hip and knee height, and a sustained floor level task with and without the exoskeleton. The exoskeleton was evaluated in spring mode, locking mode, and spring + locking mode for the panel task and only in locking mode for the floor task. The participants’ ( N = 15) muscle activity was recorded for the right lumbar erector spinae, thoracic erector spinae, tibialis anterior, rectus femoris, semitendinosus, and lateral gastrocnemius. Results Significant reduction of the rectus femoris activity was observed with the exoskeleton (median reduction: 22%–56% and peak reduction: 12%–48% for the panel task and median reduction: 57% and peak reduction:34% during the floor task). Conclusion legX significantly reduces rectus femoris activity during squatted static (floor) and dynamic (panel) work and may reduce pain and discomfort associated with squatting and potentially reduce the risk of developing knee disorders. Dynamic tasks benefit from both locking modes and spring assistance, the greatest benefit occurring with a combination of the two. Application These results show that the legX can be beneficial to activities such as electrical panel work, grinding, sanding of larger surfaces, and concrete laying.

Trunk Supporting Exoskeletons are increasingly being evaluated in workplaces as viable ergonomic interventions for reducing the risk of back injuries. A series of trunk-supporting exoskeletons have been designed and built at the University of California at Berkeley and suitX. These exoskeletons decrease the forces on the wearer’s back at L5/S1 location. This article describes one of these exoskeletons, referred to as backX, and its evaluation method. backX is designed not only to reduce the forces and torques on the wearer’s back at L5/S1 location, but also to allow the wearer to perform all kinds of maneuvers such as walking, squatting, ascending and descending stairs, slopes and ladders, riding bicycles and driving trucks. This study finds that average muscle activities of the thoracic and lumbar erector spinae muscles among equal populations of male and female subjects, wearing backX while maintaining forward bending postures, are reduced by 75% and 56% respectively. The results of this study and extended field evaluations indicate that wearing backX minimizes the risk of back injuries among workers who repeatedly go through stooping, squatting, and bending postures for various tasks, such as lifting objects.

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Lower-extremity powered exoskeletons have traditionally used four to ten powered degrees of freedom to provide gait assistance for individuals with spinal cord injury (SCI). Systems with numerous high-impedance powered degrees of freedom commonly suffer from cumbersome walking dynamics and decreased utility due to added weight and increased control complexity. We propose a new approach to powered exoskeleton design that minimizes actuation and control complexity by embedding intelligence into the hardware. This paper describes a minimalistic system that uses a single motor for each exoskeleton leg in conjunction with a bio-inspired hip-knee coupling mechanism to enable users to walk, sit, and stand. Operating in concert with a custom orthotic knee joint, the exoskeleton hip joint has been designed to mimic the biarticular coupling of human leg muscles thus allowing a single actuator to power both hip and knee motions simultaneously. The implementation of this design resulted in a system that provides comparable performance to existing exoskeletons. This system has been tested on paraplegic subjects and has successfully enabled patients to stand up, sit down, and ambulate in numerous real world situations.

This paper discusses the control of a medical exoskeleton swing leg that has a “passive” (unactuated) knee. Previous work in legged locomotion has demonstrated the feasibility of achieving natural, energy efficient walking with minimally actuated robotic systems. This work will present early results for a medical exoskeleton that only has actuation that powers the flexion and extension of the biological hip. In this work, a hybrid model of the state dependent kinematics and dynamics of the swing leg will be developed and parameterized to yield swing hip dynamics as a function of desired knee flexion dynamics. This model is used to design swing hip motions that control the flexion behavior of the passive swing knee in a human-like manner. This concept was tested by a paraplegic user wearing a new minimally actuated exoskeleton. The presented results show that a human-like swing phase can be achieved with an exoskeleton that has fewer actuated degrees of freedom than current medical exoskeletons.