Improvement of flexion/extension angle range of KneeRobo to replicate involuntary movements

We developed KneeRobo, which replicates knee joint disorders experienced by patients, to enable students studying to become physical or occupational therapists to gain practical training/testing experience virtually. We also developed a control algorithm that enables KneeRobo to realize involuntary internal/external rotation and abduction/adduction during knee flexion and extension. However, in the previous study, involuntary movements were replicated only in the flexion/extension angle range of 0°-40°. In this paper, we propose a new mechanism to replicate the involuntary movements in the flexion/extension angle range of 0°-90°. Moreover, we propose a new method to calculate winding lengths of the wires connected to the motors in KneeRobo. Then, according to the new calculation method, the target winding lengths are obtained. In the experiment, we use these target winding lengths and we find that by using the proposed method, KneeRobo can replicate the involuntary movements more accurately than previous method.