ETD

• active prostheses
• impedance control
• lower-limb prostheses
• middle-level control
• non-steady-state locomotion
• robotics
• transition tasks

This thesis addresses the challenge of enabling a robotic ankle prosthesis to perform non-steady-state locomotion tasks, an area still underexplored by current control strategies largely designed for stationary walking.
Although human gait has been extensively studied, much less is known about how it is used in daily life, where community ambulation typically consists of short walking bouts, few sequential steps, and frequent pauses. For lower-limb amputees, these patterns make transitional and irregular movements a major component of functional mobility, highlighting the need for prosthetic controllers able to respond to different joint demands.
To this end, this work develops a middle-level finite-state-machine(FSM) controller that modulates ankle impedance throughout the contact and no-contact phases, to replicate physiological behavior during non-steady-state tasks.
An open-access dataset of healthy subjects was first analyzed to characterize ankle impedance during transitional movements and to provide physiological benchmarks for controller tuning.
The proposed strategy was then experimentally tested on three able-bodied participants performing stand-to-walk, walk-to-stand, and walking transitions using a fully active ankle prosthesis with a bypass socket. A dedicated protocol was designed to compare the impedance-based FSM developed in this thesis with a position-based FSM.
Results show that, despite the preliminary and partly suboptimal model fitting, the full-stride impedance-based controller manages transitional gait more effectively than the position-based strategy, offering several important insights and a solid foundation for future advancements in adaptive prosthetic control.