Abstract
A rehabilitation robot plays an important role in relieving the therapists’ burden and helping patients with ankle injuries to perform more accurate and effective rehabilitation training. However, a majority of current ankle rehabilitation robots are rigid and have drawbacks in terms of complex structure, poor flexibility and lack of safety. Taking advantages of pneumatic muscles’ good flexibility and light weight, we developed a novel two degrees of freedom (2-DOF) parallel compliant ankle rehabilitation robot actuated by pneumatic muscles (PMs). To solve the PM’s nonlinear characteristics during operation and to tackle the human-robot uncertainties in rehabilitation, an adaptive backstepping sliding mode control (ABS-SMC) method is proposed in this paper. The human-robot external disturbance can be estimated by an observer, who is then used to adjust the robot output to accommodate external changes. The system stability is guaranteed by the Lyapunov stability theorem. Experimental results on the compliant ankle rehabilitation robot show that the proposed ABS-SMC is able to estimate the external disturbance online and adjust the control output in real time during operation, resulting in a higher trajectory tracking accuracy and better response performance especially in dynamic conditions.
Highlights
The ankle joint plays a key role in maintaining balance during walking [1,2,3]
In order to confirm the performance of the proposed control method, experiments were carried out on the 2-DOF ankle rehabilitation robot
The experiments can be divided into four groups: (1) step response experiment; (2) sine trajectory tracking experiment; (3) robustness test with human subjects; and (4) sudden external disturbance experiment
Summary
The ankle joint plays a key role in maintaining balance during walking [1,2,3]. Recently, there have been an increasing number of people suffering from ankle injuries caused by diseases and accidents.In the US, more than 23,000 cases of ankle sprain injuries happen every day [4]. The ankle joint plays a key role in maintaining balance during walking [1,2,3]. There have been an increasing number of people suffering from ankle injuries caused by diseases and accidents. In the US, more than 23,000 cases of ankle sprain injuries happen every day [4]. The postoperative recovery from ankle injury is slow and ineffective while the application of rehabilitation robots is supposed to be possible to solve this problem. Rehabilitation robots can help patients accomplish repetitive training tasks more accurately and effectively without physical therapists’ excessive participation [5,6,7]. Increasing attention has been paid to the robotic rehabilitation that is appropriate to perform repetitive exercises for the recovery from neuromuscular injuries [8]
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