Friction compensation control of pneumatic position servo system based on the adjustable stiffness

基于刚度可调的气动位置伺服系统摩擦补偿控制

School of Mechanical Engineering, Hubei University of Technology, Wuhan 430068, China

Received: 5 January 2023

Abstract

Due to the characteristics of low stiffness, low air source pressure, and easy fluid saturation of the pneumatic servo system, the energy dissipation of the system during the working process is large, the system is easily affected by friction, and the compensation effect is not obvious. Especially, the "Flat roof phenomenon" will become stronger when changing the speed direction. It seriously affects the tracking accuracy of the pneumatic servo system. In this paper, the independent metering valve control structure is proposed to eliminate the energy dissipation caused by the coupling of two chambers, so that the air fluid characteristics are within the linear range as far as possible. The nonlinear adaptive robust control method is designed for the uncertainty of some parameters in the friction, external disturbances, and dynamic loads in the pneumatic system. At the same time, the stiffness adjustment and adaptive robust control of the system are coordinated to improve the dynamic performance of the pneumatic position servo system. The simulation and experimental results show that the adaptive robust controller with stiffness adjustment can effectively reduce the energy dissipation of the system, improve the position tracking accuracy of the system, and weaken the "Flat roof phenomenon" caused by friction.

摘要

气动伺服系统的低刚度、低气源压强、流量易饱和等特性, 导致系统在工作过程中能量耗散较大, 系统易受摩擦影响, 且补偿效果不明显。尤其是当系统的运动方向改变时, 会产生明显的"平顶现象", 严重影响气动伺服系统的跟踪精度。采用负载口独立控制结构, 消除因两腔耦合而导致的能量耗散, 使系统流量特性尽可能地位于线性区间; 针对气动系统中存在的摩擦中部分参数不确定, 以及外界干扰、动态负载的不确定性, 设计非线性自适应鲁棒控制方法; 将系统的刚度调节与自适应鲁棒控制进行协同控制, 提高气动位置伺服系统的动态性能。仿真和实验结果均表明: 具有刚度调节的自适应鲁棒控制能够明显降低系统能量耗散, 提高系统位置跟踪精度, 有效改善摩擦引起的"平顶现象"。