下肢步行助力外骨骼机器人的模糊自适应PID控制

Fuzzy adaptive PID control of the lower-limb walking-assistance exoskeleton robot

针对人体生物学特点及户外步行助行要求,设计了一款下肢步行助力外骨骼机器人。为实现外骨骼机器人对人体下肢助力柔顺性目标,研究并提出了模糊自适应PID控制方法。在MATLAB/SIMULINK中搭建仿真模型,比较外骨骼关节力矩控制分别采用传统PID及模糊自适应PID控制算法的跟随效果。由仿真和试验结果可知,模糊自适应PID算法相较于经典PID算法具有响应速度快、超调量小等优点。模糊自适应PID算法对关节力矩跟踪效果有明显改善。在步态周期30%~40%时,误差最大;在步态周期15%~20%时,误差最小,为0.5 N·m。模糊自适应PID算法力矩跟踪曲线更加平滑,与参考输入幅值更为接近,支撑相最大误差为7%,且可以有效抑制外骨骼助力行走过程中带来的关节抖动。力矩跟踪能够达到理想的跟随效果,能够使得不同穿戴者的髋关节助力更加柔顺。

According to the human body’s biological characteristics and the requirements of outdoor walking assistance,the lower-limb walking-assistance exoskeleton robot is designed in this article.In order to ensure that the exoskeleton robot provides the human lower limbs with compliant walking assistance,the method of fuzzy adaptive PID control is proposed.The simulation model is built in MATLAB/SIMULINK,so as to compare the following effects of the exoskeleton joint-torque control by means of the traditional PID control algorithm and the fuzzy adaptive PID control algorithm.The simulation and experimental results show that compared with the classic PID control algorithm,the fuzzy adaptive PID algorithm has such advantages as fast response speed and small overshoot.The fuzzy adaptive PID algorithm has significant improvement in the effect of joint-torque tracking.The error is the largest when the gait period is 30%~40%.When the gait period is 15%~20%,the error is the smallest,which is 0.5 N·m.In addition,the fuzzy adaptive PID algorithm’s torque-tracking curve is smoother and closer to the referred input amplitude;the maximized error of the support phase is 7%,and it can effectively suppress any joint jitters caused by assisted walking.This mechanism enjoys a desirable effect of torque tracking,and makes the hip-joint assistance of different wearers more compliant.