Stroke impacts 7 million people in US. Of the disabilities induced by stroke, mobility limitations are among the strongest factors limiting quality of life. Robotic approaches to stroke rehabilitation in the lower-limb have historically focused on rhythmic movements and activities which replicate gait kinematics. These approaches have not yet yielded better outcomes than standard therapy. A reason for this could be the lack of volitional engagement and goal-directed behavior in these activities. This Dissertation explores the design of robotic and software systems required for the study of goal-directed lower-limb motor control and the application of these systems to derive new insights through controlled experiments. The outcomes of this Dissertation aim towards facilitating future studies of rehabilitation in stroke affected populations.

The First chapter describes the design, development, and validation of NOTTABIKE, a high-power haptic robot developed for the study of motor control and the delivery of lower-limb therapy. The second chapter explores the results of experiments on healthy subjects performing lower-limb reaching tasks in a dynamic environments. The results center around the time course of adaptation to these varied environments and an optimal control model of adaptation. The third chapter details an experiment investigating the effect of cognitive models on the skill learning in the lower-limb, an important yet understudied aspect of rehabilitation with robotic systems. Finally, the fourth chapter documents the optimal design of the linkage system for a 2DOF high power haptic robot using a novel force-space matching approach. This Dissertation lays the foundation for a Research Program in the BADGER Lab oriented towards the study of lower-limb motor control and the application of rehabilitative therapy in the lower-limb that focuses on the training of volitional movements.