Patient simulator using wearable robot: Representation of invariant sitting-down and standing-up motions of patients with knee-OA

It is ethically problematic to engage people with impaired motor functions in experiments, wherein they may face severe pain and unacceptable risk of injuries. We developed a wearable robot for healthy adults and its control algorithm to simulate the behaviors of patients with knee osteoarthritis. We focused on invariant motions, which are typically presented for avoiding knee pain. In order to simulate patient movements by a healthy person wearing a robot, we formulated a model motion that represented invariant patient motions. We then determined the output torque of the exoskeletal knee robot such that the wearer´s motion followed the model motion. The effectiveness of the method was testified for standing-up and sitting-down motions, and some characteristic impaired motions such as body inclination to the healthy side and imbalanced right and left knee angles were manifested by the simulator.