The research in this BRIGE proposal explores Chemo-Muscle actuation as a novel actuation approach for energetically-active above-knee (AK) prostheses. With the high performance provided by this novel actuation approach, the resulting active AK prosthesis is expected to generate sufficient power output to restore the locomotive functions in energetically-demanding modes (such as upslope walking and stair climbing). This research will lay a solid foundation for the PI's long-term research goal of creating a practical powered-knee-and-ankle AK prosthesis with comparable functionality, weight, and size as biological lower limbs. Leveraging the research in robotic prosthetics, the PI will also create a series of educational activities with the common theme of "Helping Disabled Persons with Robotics!" These activities will develop a basis for the PI's educational goal of broadening the participation in engineering research and education among an increasingly diverse student population, leveraging the biomedical robotics as an innovative educational media.

INTELLECTUAL MERIT In the area of AK prosthetics, the majority of state-of-the-art devices are energetically passive. The inability to deliver joint power significantly impairs their ability of restoring lost limb functions. To overcome this limitation, a novel Chemo-Muscle actuation approach will be introduced. This actuation system enables high power output and long duration of operation within a compact package. Two key elements are incorporated, including: (1) a high-energy-density supply, achieved through a special type of liquid fuel, namely monopropellant (e.g. hydrogen peroxide), which decomposes instantaneously upon the contact with certain catalytic materials and generates a large volume of gaseous mixture for pneumatic actuation; and (2) a high-power-density actuator, namely pneumatic artificial muscle, which emulates the functioning mechanism of biological muscles and provides a large power output with a light-weight flexible structure. While providing high actuation performance, Chemo-Muscle also provides adequate safety and endurance features for prosthetic use, leveraging the inherently safe nature of monopropellant in combination with proper design measures. To explore the application of Chemo-Muscle actuation in active AK prostheses, the proposed two-year plan is expected to achieve three objectives, including: (1) Collect user inputs and create a design guideline for powered AK prostheses; (2) Establish a flexible and compact actuation structure for Chemo-Muscle actuated AK prostheses, and develop a tethered prosthesis prototype (with powered knee and ankle joints) for performance evaluation; (3) Develop a robust control algorithm to generate a smooth and natural walking gait.

BROADER IMPACTS Currently, there are more than 357,000 above-knee amputees in the U.S., and this number is expected to double by 2050. The proposed research has the potential to benefit society by significantly enhancing these amputees' mobility and improving their life quality. Furthermore, leveraging the interactive nature of biomedical robotics, the PI will create a series of educational activities with the common theme of "Helping Disabled Persons with Robotics!" (1) Recruiting, retaining and mentoring disabled students for robotic prosthetics research, with the notion of "Disability-related research conducted by disabled persons for disabled persons." (2) Recruiting graduate student researchers from underrepresented groups through a variety of routes. (3) Integrating undergraduate research with the development of a robotic arm exhibit for a science museum. (4) Developing a new graduate-level course "Biomedical Robotics." (5) Promoting science and engineering in middle/high schools with robotic activities, with the emphasis on the African American students in the nearby Sumter County, one of the lowest-income school districts in the nation with 99% African American enrollment.

Project Report

In this BRIGE project, we explored the use of high-performance muscle actuation for the powered above-knee prostheses. Currently, most existing above-knee prostheses are energetically passive (i.e., unpowered). These passive prostheses are unable to deliver joint power like biological joints do, causing a number of problems such as the users being unable to walk upslope/upstairs and expending more energy in walking. To solve these problems, our research aims at creating lightweight powered prostheses with the new muscle actuation technology. In this project, we created a new actuation system such that only one muscle actuator is needed to power each joint, while the traditional system requires two (the muscle actuator only generates force in one direction). We also developed a robust control algorithm for this new actuation system to control the robotic joint motion. Utilizing these new technologies, we built an energetically active prosthesis prototype with powered knee and ankle joints, and it was able to allow a user to walk naturally in the experiments. To further reduce the weight and size of the powered prostheses, we have designed and fabricated the second prototype, which is currently being tested in the principal investigator's lab. With our research, we hope to benefit the large number of above-knee amputees in the United States. Powered prostheses would enable them to be more independent and enjoy a higher-quality life. The impact of this project is also generated by the educational activities. Three Ph.D. students and ten undergraduate students have contributed to the project. The students conducted research on the powered above-knee prostheses described above, as well as a robotic hand demonstrator for the education outreach purpose. This robotic hand demonstrator provides similar functions as a human hand, and a user can interact with it through a highly intuitive controller. With this robotic hand demonstrator, we participated in various outreach activities, such as the Engineering Showcase at the McWane Science Center at Birmingham, AL and the STEAM Night event at the University Place Elementary School near the UA campus. Through these activities, we hope to spark the young children's interest in robots and attract them to the science and engineering fields. Last but not least, we were able to recruit four students with disabilities (including three lower-limb amputees) into this project. They participated in the project by serving as test subjects, designing the robotic hand, and creating control systems for the robotic hand and the powered prostheses through circuitry construction and microcontroller programming. In the future, we plan to conduct this type of disability education activities on a regular basis and continue serving the disability community.

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University of Alabama Tuscaloosa
United States
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