Please find a small subset of our active projects below. This is intended to give a flavor of the type research conducted in our lab, and provide a means for oversight of federally sponsored projects, rather than to act as an exhaustive list.

We are always interested in new project ideas related to our mission. If you are a student with an idea for a project please see joining the lab. If you are interested in collaborative research or product development please contact Steve Collins.

User-optimal robotic prosthesis design

The objective of this research is to develop methods for optimizing robotic ankle-foot prosthesis function to the needs of individual users. The approach is to develop computational models of human-prosthesis interaction, use them to predict optimal device designs, and refine predictions in experimental work with a versatile robotic testbed. A detailed musculoskeletal simulation model of amputee locomotion, with tunable user-specific properties, will be generated. Numerical optimization will be used to obtain designs that are optimal for specific users and robust to small changes in user characteristics. Designs will be presented to human subjects with a `universal ankle-foot prosthesis emulator' in experiments that measure human energy use, muscle activity, body mechanics, and balance. Experimental results will be used to generate a model with high predictive accuracy. The research will result in an empirically-validated software tool for use by clinicians in prescribing optimal prosthesis designs to individual patients.

If successful, the benefit of this research will be improved mobility and quality of life for individuals with amputation, achieved through a software tool that guides the design of user-optimal robotic ankle-foot prostheses. For example, the research is expected to quantify trade-offs between the costs and benefits of more powerful, but heavier and more expensive, motors, allowing optimal product design for individual users. The resulting devices are expected to reduce chronic problems with walking speed, fatigue, falls, and pain for more than 1 million people with lower-limb amputation in the United States. This methodology and infrastructure is also expected to improve biomechatronic design processes in general, for example improving the design of rehabilitation robots. The research will provide a collaborative, interdisciplinary environment for students, including minority, female, and disabled individuals.

Team: Steve Collins, Josh Caputo and Evan Dvorak,

Collaborators: Manoj Srinivasan at The Ohio State University

Funding: National Science Foundation, ENG Directorate, CMMI Division, E&SD Program.

Rapid exploration of robotic ankle exoskeleton control strategies

The objective of this project is to compare different techniques for assisting individuals with stroke-related mobility impairments using a robotic ankle orthosis. Several promising assistance techniques have been developed for robotic prostheses and rehabilitation platforms. We extend these techniques to exoskeletons worn at the ankle joint, adapt them for individuals with stroke, and perform direct, controlled comparisons of their efficacy. We use an ankle exoskeleton testbed with unique versatility to emulate each assistance technique, allowing comparisons within the same platform. Each promising technique is first programmed and verified in pilot tests with this emulator. We then perform multi-dimensional parameter studies, first on subjects without neurological impairment and then on subjects with hemiparesis following stroke. Results are used to identify ideal parameters for each technique, and these settings are used in an across-technique comparison. We are also developing and validating a standardized set of quantitative performance metrics, including measures of effort, preferred speed, and stability. This project is expected to provide a scientific foundation for the design and prescription of robotic ankle-foot orthoses that manage the symptoms of chronic hemiparesis for the millions of individuals who have had a stroke. Results will inform improved designs and test feasibility of low-cost designs, potentially leading to improved treatments and outcomes.

Team: Steve Collins, Rachel Jackson, Katie Poggensee, Kirby Witte, Juanjuan Zhang and Kyle Rawding

Collaborators: Greg Sawicki at NC State and UNC Chapel Hill

Funding: National Science Foundation, CISE Directorate, IIS Division, NRI Program - Slides: PPT, PDF

Development and Comparison of New Methods for Stabilizing Amputee Gait

About half of the one million people in the United States with lower-limb amputation experience at least one fall each year, usually during walking. These falls often result in serious injury, with annual health care costs of over one billion dollars. Side-to-side motions are least stable during walking, especially on uneven terrain, and require more active control for balance. Surprisingly, little is known about how balance is affected by prosthesis properties that influence side-to-side motions. While robotic prostheses have improved propulsion and energy cost, this technology has not yet been used to improve stability or reduce fall risk.

This project explores new approaches to the control of side-to-side balance using robotic prostheses. We characterize the effects of prosthesis parameters on stability and establish quantitative cost-benefit relationships for balance-related performance. This project will yield new fundamental understanding of the role of ankle control in human balance and of the impact of instability on other aspects of gait and mobility. It will develop technologies that lead to reduced fall rates, increased satisfaction and enhanced mobility for individuals with amputation, improving quality of life. Active, semi-active and passive prosthesis elements that enhance balance are being developed and their relative costs and benefits quantified along key dimensions, facilitating rational design choices. This will lead to increased efficiency in health care delivery, with increases in device cost being offset by reductions in costs for treating fall-related injuries.

Team: Steve Collins, Myunghee Kim, Vincent Chiu, Tyler Del Sesto, and Hannah Lyness

Funding: National Science Foundation, ENG Directorate, CBET Division, GARDE Program

Balance Recovery Control for Amputees Using Powered Leg Prostheses

The overarching goal of this project is to test the hypothesis that a reflex-like prosthesis control strategy inspired by human motor control can improve balance for above-knee amputees during walking. Balance recovery has evolved into a major research area as fall-connected injuries are one of the main causes of impairment, disability and death in aging societies. Lower limb amputees are especially at risk of falling as current prosthetic limbs provide only limited functionality for recovering from unexpected disturbances. The project combines methods from computational neuromechanics, robotic prosthetics, and biomechanical gait analysis to identify prosthesis control strategies that help above-knee amputees recover balance after large disturbances such as trips, slips and pushes. An existing reflex control model of human locomotion is adapted to amputee gait, involving theoretical research on feedback control algorithms for powered prosthetic limbs and predictions of amputee recovery behavior in simulated experiments. Prototypes of powered knee-ankle prostheses are developed, including a tethered prosthesis emulator for rapid human-in-the-loop control design and evaluation on a treadmill, and a mobile prosthesis allowing evaluation outside the laboratory. Control algorithms identified in the reflex control model are embedded in these prototypes and systematically evaluated in balance recovery experiments with above-knee amputees. We expect this project to establish new control paradigms for powered prostheses and enable practical controllers for improved balance recovery in amputee gait. In addition, the project will advance theoretical models of human balance recovery as well as control algorithms and hardware designs for robotic knee-ankle prostheses.

Team: Steve Collins, Myunghee Kim, Vincent Chiu, Blair Emanuel, and James Gabriel

Collaborators: Hartmut Geyer and Nitish Thatte, at The Robotics Institute, Carnegie Mellon University

Funding: National Science Foundation, CISE Directorate, IIS Division, NRI Program

Clinic-based robotic prosthesis emulator for amputee gait capacity assessment

This project comprises the development of a robotic prosthesis emulator for use in clinical settings. This system will allow rapid, objective, prospective assessment of the functional benefits of different conventional and robotic ankle-foot prostheses for individual patients with amputation, allowing the determination of the best choice of prescribed prosthesis. The proposed system will emulate commercial prostheses across the available spectrum, and provide hard data demonstrating how much gait improvement (e.g. increased speed or reduced energy cost) an individual subject can expect at each level of prosthesis performance and cost.

Team: Steve Collins

Collaborators: Peter Adamczyk, University of Wisconsin and Josh Caputo, Human Motion Technologies L.L.C.

Funding: National Institutes of Health, NICHD, SBIR program.