Model-Based Design and Development of an Offboard Actuation System for Lower-Limb Biomechatronic Devices

Abstract

New robotic technologies allow for the rapid research and development of wearable assistive devices. Offboard robotic actuation systems use large, stationary actuators and versatile control systems to apply joint torques to assistive devices through flexible transmission tethers. This setup allows researchers to rapidly prototype assistive device behaviors and control laws without committing to a specific wearable device embodiment. The goal of this thesis was to develop an offboard robotic actuation system capable of actuating lower-limb wearable devices through Bowden cables. During the design process, a novel dynamic model of the biomechatronic system was developed. This model was used within an optimization framework to select optimal mechanical design parameters and servomotors. After design parameter optimization, a motor chassis and mechanical power transmission were designed and manufactured. A high-voltage electrical circuit and electrical panel were designed and constructed to provide power to the servomotor amplifiers. A commercially available prosthetic foot was modified to be Bowden cable driven in the sagittal plane and was instrumented with sensors to detect joint rotation and Bowden cable force. A National Instruments PXI was purchased to read sensor signals, send motor commands, send data to a user interface in real-time, and log data.