Shared Control in Exoskeletons

Currently, lower-body exoskeletons for paraplegics are investigated as an alternative to wheelchairs and as an exercise method with medical benefits. Literature provides little examples for users to influence the length or frequency of steps taken by the exoskeleton, complicating stability and practical usability. This study proposes a novel control paradigm that allows users to influence step parameters of the exoskeleton, through a bi-directional haptic interface that also provides feedback. The exoskeleton handles the cyclic walking pattern while the patient is enabled to correct for disturbances. I adapted an existing lower-body exoskeleton trajectory generator to allow real-time adaptation of step length and swing time. To demonstrate a proof-of-concept of the control paradigm, I implemented the controller for a virtual 2D exoskeleton, to be controlled by an existing bi-manual haptic control interface. A human-in-the-loop experiment was performed with the goal to compare the benefits of user control over either step length or swing time with a situation with no human control. In the experiment perturbations of increasing magnitude were applied to a 2D virtual exoskeleton, participants could increase or decrease either step length or swing time during swing to correct for these disturbances. The number of successful step taken before the perturbations resulted in a fall were measured. The swing time group succeeded in making the exoskeleton walk stably significantly longer then when there was no human input, proving that the proposed control paradigm is feasible and beneficial for stability.