Control Method of Upper Limb Rehabilitation Exoskeleton for Better Assistance: A Comprehensive Review

The upper limb rehabilitation exoskeleton is a robotic-arm-like device that fits the human upper limb and assists in movement, having the potential to be widely used in medical practice. The control method of the upper limb rehabilitation exoskeleton system is an important factor that affects the effectiveness of its rehabilitation training assistance and is also the focus of research in this field. In this article, we divide the control method of the upper limb rehabilitation exoskeleton into two levels, the high-level control mode (including passive mode, active mode, and ANN, etc.) and the low-level controller. The design of the controller aims to meet the requirements of the control mode but faces difficulties such as complex dynamic models of the system, unknown external disturbances, and motion intention recognition to achieve accurate motion trajectory tracking and flexible human–robot interaction. Based on relevant literature in the field of upper limb rehabilitation exoskeleton control methods in recent years, we analyze the rehabilitation training control modes that researchers aim to achieve, as well as the work they have done in controller design to achieve these control modes. We also propose potential research directions for achieving better exoskeleton-assisted training effects.