Feedback Distortion to Augment Controllability of Human Limb Motion

Virtual robotic rehabilitation is beginning to show its efficacy in motor function recovery for stroke survivors. However, due to the lack of understanding in the potential danger imposed by large energetic actuators safety for intimate interaction is typically not taken into account beyond software. For this reason the ability to extend virtual robotic rehabilitation to hospital or domestic settings is limited. Our group has constructed a safer, purely dissipative, robotic device for rehabilitation of large whole body movements. Consequently, shifting to passive actuation fundamentally changes common control strategies that work well for active devices. In this paper, we present a method that distorts visual feedback to the subjects as a first step to achieve the desired controllability hereto limited by passivity constraints. With visual distortion we demonstrate how a subject's arm trajectory can be altered in a way that passive actuation alone cannot. Our results show that subjects involuntarily changed their path motion up to 30% with distortion applied; this ability to steer user's movements can be harnessed to offset controllability issues.