A new active rehabilitation training mode for upper limbs based on Tai Chi Pushing Hands

Abstract

Robot-assisted rehabilitation is a crucial approach to restoring motor function in the limb. However, the current training trajectory lacks sufficient theoretical or practical support, and the monotony of single-mode training is a concern. Tai Chi Pushing Hands, a beneficial and effective daily exercise, has been shown to improve balance function, psychological state, and motor function of the upper extremities in patients recovering from stroke. To address these issues, we propose a new active rehabilitation training that incorporates Tai Chi Pushing Hands movements and yin-yang balance principles. The training trajectory and direction are encoded by the velocity field and consist of two processes: yang (push) and yin (return). During yang, the limb actively pushes the robot to move, while during yin, the limb actively follows the robot’s movement. To provide necessary assistance, an admittance controller with self-adaptive parameters is designed. In addition, we introduce two indexes, the ‘Intention Angle’ ($\varpi$) and the time ratio ($\Gamma$), to evaluate motion perception performance. Our experiment was conducted on a 4-degree-of-freedom upper limb rehabilitation robot platform, and the subjects were separated into a familiar group and an unfamiliar group. The experiment results show that the training could be completed well no matter whether the subject is familiar with Tai Chi Pushing Hands or not. The parameters and the movement of the robot can be adjusted based on the interactive force to adapt to the ability of the subject.