Hoyt, KennethHao, Shuang2023-08-302023-08-302022-052022-05-01May 2022https://hdl.handle.net/10735.1/9821An estimated 11% of the world's population either faces difficulty with daily mobility or uses assistive devices such as walkers, canes, crutches, and wheelchairs, reducing the quality of life and impairing the independence of their living. Lower-limb robotic assistive devices such as prosthetic limbs and exoskeletons hold a great promise to improve the quality of life of these individuals by replicating most of the actions of healthy biological limbs. However, the clinical translation and widespread adoption of these devices are still hindered by the lack of control intuitiveness and continuous adaptation to user intentions. Ultrasound is a noninvasive sensing modality that can access human neuromuscular information by measuring muscle activation and contraction. Hence, the objective of the present dissertation was to investigate the feasibility of using the ultrasound sensing modality as a wearable human-machine interface for lower-limb robotic assistive devices. We hypothesize that human lower-limb muscle kinematics and kinetics, noninvasively tracked by ultrasound sensing, can be used to estimate continuous lower-limb joint movements. We further hypothesize that ultrasound sensing can be used as a sensing interface with a continuous volitional control framework to integrate with lower-limb robotic assistive devices. In this dissertation, we: 1) develop a framework to extract muscle contraction features from ultrasound images demonstrate their use for lower-limb joint motion estimation, 2) develop an ultrasound-based control framework for continuous joint-level control of lower-limb assistive devices during various steady-state and non-steady-state ambulation modes, and 3) improve the potential integration of the ultrasound technology with existing lower-limb assistive devices by reducing the integrationlimiting parameters of the current ultrasound technology. The outcomes of this dissertation may eventually enhance the clinical relevance of lower-limb robotic assistive devices and facilitate their widespread adoption for the population with mobility problems.application/pdfenEngineering, BiomedicalThesis2023-08-30