Mechanism Design and Control of Shoulder Rehabilitation Robots: A Review

Neurological injuries are one of the main reasons for the loss of functional mobility in humans. Compromised functionalities may include restrictions in the shoulder’s range of motion. Robotic devices, used for the physical therapy of shoulder, have different mechanism designs and control strategies. The aim of this paper is to provide a detailed review of different mechanisms used in shoulder rehabilitation robots as well as their control strategies. Shoulder robot mechanisms are grouped based on their actuating systems, namely, cable-driven shoulder rehabilitation mechanisms and power-driven mechanisms. The actuation systems considered during this study include electrical actuators, pneumatic actuators, series elastic actuators, and pneumatic muscle actuators. Experimental evaluation and validation of previous shoulder rehabilitation robots is also discussed citing their constraints and limitations. Safety aspects of existing shoulder robots have also been discussed. This paper also presents the advantages and disadvantages of previously proposed shoulder rehabilitation robots, their actuation, and control strategies and concludes by presenting future challenges and pathways.