Abstract: Characterizing the Performance of Fluidic Muscles for Use in an Assistive Knee Brace

A fluidic-muscle-based robotic knee brace was developed/tested at SJSU and the research work was widely published [SCCUR 2019/IMECE 2019/IMECE 2020/NCUR 2020]. The brace was designed to facilitate rehabilitation for impaired stroke patients who need assistance to perform recovery exercises. The initial knee brace design incorporated Festo’s industrial-grade flexible fluidic muscles along with rotary sensors that measured the angular displacement of the leg. Additionally, an Arduino-based control system was designed that triggered the brace operation by inflating the fluidic muscle to the desired pressure. While the knee brace is fully operational, design limitations do not allow the current design to achieve greater than approximately 45 degrees of angular displacement which is significantly below the required 90 degrees necessary for complete leg extension. In this new effort, a fluidic muscle is being designed using latex tubing surrounded by an expandable sleeving. As the muscle inflates, the latex tubing expands and the wire sleeving restricts this expansion, causing the muscle to contract. Manufacturing custom-based fluidic muscle allows more control over the geometry of the muscles on the leg brace. Multiple muscles with different lengths have been manufactured and investigated for their contraction behavior under different operating pressures and load conditions. Based on this data, the design of a new knee brace is currently underway to ensure that 90 degrees of angular displacement can be achieved. The current work also includes the analysis of additional shortcomings of the current device and looks at new efforts to make other design changes in the current system.