Assist-As-Needed Control Strategy of Bilateral Upper Limb Rehabilitation Robot Based on GMM

Maoqin Li,Guang Feng,Xueliang Zhang,Jiaji Zhang,Guokun Zuo

doi:10.3390/machines10020076

Abstract

Robotic-assisted rehabilitation therapy has been shown to be effective in improving upper limb motor function and the daily behavior of patients with motor dysfunction. At present, the majority of upper limb rehabilitation robots can only move in the two-dimensional plane, and cannot adjust the assistance mode in real-time according to the patient’s rehabilitation needs. In this paper, according to the shortcomings of the current rehabilitation robot only moving in the two-dimensional plane, a type of bilateral mirror upper limb rehabilitation robot structure with the healthy side assisting the affected side is proposed. This can move in three-dimensional space. Additionally, an assist-as-needed (AAN) control strategy for upper limb rehabilitation training is proposed based on the bilateral upper limb rehabilitation robot. The control strategy adopts Gaussian Mixture Model (GMM) and impedance controller to maximize the patient’s rehabilitation effect. In the task’s design, there is no need to rely on the assistance of the therapist, only the patients who completed the task independently. GMM guides the rehabilitation robot to provide different assistance for the patients at different task stages and induces the patients to complete the rehabilitation training independently by judging the extent to which the patients can complete the task. Furthermore, in this paper, the effectiveness of the proposed control strategy was verified by three volunteers participating in a two-dimensional task. The experimental results show that the proposed AAN control strategy can effectively provide appropriate assistance according to the classification stage of the interaction between the patients and the rehabilitation robot, and thus, patients can better achieve the rehabilitation effect during the rehabilitation task as much as possible.

Highlights

According to the 2019 global health estimate report [1], stroke is the second leading cause of death in humans
In order to prove the effectiveness of the proposed control strategy, we carried out experiments on the developed end-effector upper limb mirror rehabilitation robot, and the relevant contributions are as follows: (a) In order to restore the upper limbs of patients with motor dysfunction, we developed a new end-effector upper limb mirror rehabilitation robot
Aiming at patients with upper limb motor dysfunction, this paper developed a type of end-effector bilateral mirror upper limb rehabilitation robot device, which has three degrees of freedom and can guide patients’ arms to carry out rehabilitation training in a three-dimensional space trajectory (Figure 1)

Summary

Introduction

According to the 2019 global health estimate report [1], stroke is the second leading cause of death in humans. As a result of stroke, most patients’ limbs have different degrees of motor dysfunction. Clinical studies have shown [4] that rehabilitation robots can effectively improve the motor function of the patient’s limb, and even restore daily life movements. For patients with motor dysfunction, the rehabilitation process mainly repeats a movement for a long time, in order to strengthen the movement function of the damaged parts of the body. Continuing the same movement for a long time is exhausting, and may make the patients produce negative attitudes, leading to a decrease in the level of attention, and a reduction in the effectiveness of rehabilitation therapy [5]. How to promote patients’ active participation and improve their attention [6] has become a hot topic in the field of neural rehabilitation research [7]

Methods

Discussion

Conclusion