Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Mechanical Engineering & Applied Mechanics

First Advisor

Katherine J. Kuchenbecker


Many mechanical devices and robots operate in home environments, and they offer rich experiences and valuable functionalities for human users. When these devices interact physically with humans, additional care has to be taken in both hardware and software design to ensure that the robots provide safe and meaningful interactions. It is advantageous to have the robots be customizable so users could tinker them for their specific needs. There are many robot platforms that strive toward these goals, but the most successful robots in our world are either separated from humans (such as in factories and warehouses) or occupy the same space as humans but do not offer physical interactions (such as cleaning robots).

In this thesis, we envision a suite of assistive robotic devices that assist people in their daily, physical tasks. Specifically, we begin with a hybrid force display that combines a cable, a brake, and a motor, which offers safe and powerful force output with a large workspace. Virtual haptic elements, including free space, constant force, springs, and dampers, can be simulated by this device. We then adapt the hybrid mechanism and develop the Gait Propulsion Trainer (GPT) for stroke rehabilitation, where we aim to reduce propulsion asymmetry by applying resistance at the user's pelvis during unilateral stance gait phase. Sensors underneath the user's shoes and a wireless communication module are added to precisely control the timing of the resistance force. To address the effort of parameter tuning in determining the optimal training scheme, we then develop a learning-from-demonstration (LfD) framework where robot behavior can be obtained from data, thus bypassing some of the tuning effort while enabling customization and generalization for different task situations. This LfD framework is evaluated in simulation and in a user study, and results show improved objective performance and human perception of the robot. Finally, we apply the LfD framework in an upper-limb therapy setting, where the robot directly learns the force output from a therapist when supporting stroke survivors in various physical exercises. Six stroke survivors and an occupational therapist provided demonstrations and tested the autonomous robot behaviors in a user study, and we obtain preliminary insights toward making the robot more intuitive and more effective for both therapists and clients of different impairment levels. This thesis thus considers both hardware and software design for robotic platforms, and we explore both direct and indirect force modulation for human-assistive technologies.


Available to all on Saturday, September 09, 2023

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