Control of an Exoskeleton for Realization of Aquatic Therapy Effects

Exoskeletons are attracting great attention as a new means of rehabilitation devices. In such applications, control algorithms of exoskeletons are often inspired by nature for natural and effective assistance for patients. In this paper, a control algorithm inspired by aquatic therapy is introduced. Aquatic therapy provides various beneficial effects for rehabilitation based on useful properties of water, e.g., buoyancy and drag. The proposed controller calculates joint torques equivalent to the buoyant and drag forces. Then, an exoskeleton-type assistive device generates the calculated joint torques to provide the similar effects as aquatic therapy. In this paper, the Sogang University biomedical assist robot is utilized as a testbed. This paper also discusses the mechanical impedance of actuators, which obstructs implementation of controllers in practice. The resistive forces generated by actuators are precisely modeled and compensated to realize the control algorithm inspired by aquatic therapy correctly and effectively.