A Control Method for Asymptotically Improving Kinesthetic Transparency of a Wearable Joint

It is considered to be desirable that a wearable joint can be operated by human daily skills. In order to realize such a joint, the joint should be controlled so that the kinesthetic feeling induced by the kinetic characteristic of an object is directly, or transparently, transmitted to a person without any kinetic distortion by the joint itself, because it is considered that kinesthetic feeling induced by the object plays an important role in performance of the skills. This is the control issue of "kinesthetic transparency". This paper proposes a control law to improve kinesthetic transparency of a wearable joint based on active compensation for the kinetic characteristic of the joint, and adaptive control is incorporated in order to eliminate necessity of off-line estimation for unknown kinetic parameters of the joint. Simulation results demonstrate that the proposed control law effectively improves kinesthetic transparency of the joint. However, experimental results reveal that more accurate compensation of frictional terms is necessary for further improvement of kinesthetic transparency.