Objective: To examine the safety and efficacy of ambulation utilizing a semi-passive and lightweight powered exoskeleton by spinal cord injury (SCI) patients.Methods: This is a multi-center, open-label, prospective cohort study across three facilities. A cohort of 40 individuals with SCI from T4-L5 was recruited into a 20-session training and assessment protocol, utilizing the SuitX Phoenix. All patients were tested using a 10-m-walk test (10 MWT), 6-min-walk test (6 MWT), and Timed up & Go test (TUG). Patient satisfaction, pain, exertion, changes in affect, as well as overall comfort and confidence were reported using a satisfaction survey, Rated Perceived Exertion (RPE) scale, and Positive and Negative Affect Schedule (PANAS). Safety outcomes, adverse events, and device malfunctions were reported.Results: Forty participants completed the study. There were no serious adverse events. All participants reported moderate to high levels of comfort and confidence using the device. All patients were able to achieve FIM of >4 on transitional movements and walking. The neurological level of injury had a statistically significant association with walking speed, WISCI-II, and FIM. Participants with an incomplete spinal cord injury had a higher FIM, faster speed, and higher WISCI-II in all outcome measures.Conclusion: This is the first study to examine the safety and efficacy of SuitX Phoenix for ambulation by SCI patients. We have shown that Phoenix is efficacious in allowing adults with SCI T4 to L5 perform walking and transitional movements. This study also reports the safety-profile of the device, user satisfaction, and psychological trends during training.

A novel method of controller tuning is introduced to achieve a desired closed-loop response. It uses the same strategy as Iterative Feedback Tuning (IFT), but instead of relying on a scalar cost function of the performance error between the desired response and system response, it utilizes the expanded version of the performance error in the time-scale domain for estimating the suitable controller parameters. The proposed method relies on the enhanced delineation of output sensitivities in the time-scale domain to identify regions in the time-scale domain wherein the performance error can be attributed to individual controller parameters [1]. It then relies on the error association in each region to estimate the corresponding controller parameter. It is shown that given a realistic desired response for the closed-loop system, the proposed method can lead to satisfactory controller parameters. It is also shown that the results from this method can be integrated with those from IFT to represent the best of the two solutions from the time and time-scale domains.

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.

This article describes the design of Austin exoskeleton – a minimally actuated medical exoskeleton with mechanical swing-phase gait generation and sit-stand assistance. The Austin exoskeleton is an accessible lightweight system that enables individuals with paraplegia to walk. The gait generation hardware of the Austin exoskeleton suit consists of three major components: hip actuation, a hip-knee coupler, and a controllable locking knee. Users operate the exoskeleton with a simple wireless user interface consisting of two push buttons that are installed on the handle of the stability aid. Electrical components are located on the back of the exoskeleton. A single actuator per leg and a mechanical hip-knee coupler power the knee during swing phase and provide assistance for sitting and standing. The suit’s design embeds gait generation into hardware, decreasing controller complexity. By using a bio-inspired coupling mechanism, the Austin system is able to power both the hip and knee joints using a single hip actuator.