Evaluating Efficacy of Continuous Assistance Control During Orientation Tasks with an Active Wrist Exoskeleton

This article reports a study evaluating the effect of continuous assistance via an active exoskeleton during orientation tasks of the human wrist in a serious game. The proposed platform features a complete system that may be used for robot-assisted rehabilitation in clinics, offering support for both the therapist and the patient. It gives the possibility to customize the rehabilitation session by regulating the assigned task difficulty, the assistance level offered by the exoskeleton, and the wrist Degrees of Freedoms (DoFs) to be supported, providing a versatile, easy-to-use, rehabilitation station. The setup consists of a 3-DoFs wrist exoskeleton activated by three electric motors, connected to a wheeled station containing the control unit and the host PC to actuate the exoskeleton. The exoskeleton allows to monitor the positions of the human wrist joints and the force applied to the device by the user while performing a movement. Advanced software has been implemented to create a stimulating environment during therapy through virtual reality. The Flight Simulator serious game has been used to investigate the user's wrist Range of Motion (RoM) covered while reaching twenty targets. Thirteen healthy subjects tested the system under two different conditions, considering the device assistance on/off. Results show a significantly higher performance under assistance, rather than without it, on the exploitation of the wrist RoM and on the intuitiveness of movements during the orientation task. A reduction of around 30% of the overall muscle stress has been measured, highlighting the assistance efficacy of the system.