负载中含有负值弹性刚度的电液负载模拟器机理研究

High performance control of high-speed Vehicle steering gear and flow control of large flow valve is of concern, in order to achieve fast and high-precision loading experiment in such occasions, the development for electro-hydraulic load simulator seem urgent. Electro-hydraulic load simulator is naturally an electro-hydraulic force control system. Such occasion’s loads exhibit negative spring stiffness attributes. The presence of negative spring stiffness in the loads makes electro-hydraulic control system loses stability in nature. Due to the spring stiffness and position disturbance, performances of the force control system become deterioration. This project is to investigate the dynamic coupling in the force control system in the occasion that the spring stiffness in the loads contains a negative magnitude; to explore the mechanism of loss of stability for the load simulator and to solve Lyapunov’s stability. By the addition of a compensator for inhibition of extraneous force caused by the forced flow under the perturbing displacement and by the employment of fuzzy control and sliding mode control, the control algorithm is constructed for the improvement of system response and control precision. In the situation of a complicated variable load, the efforts in which the load simulator can be continuously loaded in high precision might break the situation that electro-hydraulic load simulator can only loaded in a fixed magnitude. This project provide a test prototype for the practical application of high response and high accuracy electro-hydraulic force control system under complex loads and for the high accuracy test development such as the high-speed aircraft steering gear and the large flow valve.

高速飞行器舵机控制及大流量阀门流量的高精度控制已备受关注，为了实现对这类场合的试验进行快速、高精度加载，电液负载模拟器的研发显得迫切。电液负载模拟器本质上是一个电液力控制系统。然而这类场合中的负载表现出弹性刚度为负值的属性。当负载中存在负值弹性刚度时，电液力控制系统在本质上失去稳定性；由于弹性刚度和位置扰动的存在，导致力系统品质变差。本项目通过深入分析在负载中弹性刚度含有负值时力控制系统的动力学耦合，探究模拟器系统稳定性丧失的机理和李雅普诺夫理论求解稳定性；借助加入抑制由于位置扰动导致强迫流量进而引起多余力抑制的补偿器，采用以及采用模糊控制和滑模控制等，构建提高系统响应速度和控制精度的控制算法。以期打破目前电液负载模拟器只能定载荷有级加载的局限，实现在复杂载荷下可变载可连续地高精度加载；为复杂负载高响应电液力控制系统精确控制的实际应用和高速飞行器舵机及大流量阀门的高精度试验提供原理样机。

本项目针对电液负载模拟器中电液力控制系统自身结构的本质不稳定、被动式加载时存在多余力、负值弹性刚度负载和响应低精度差等问题展开研究。通过对一类负载中含有负值弹性刚度的复杂负载、以位置为扰动量的电液力控制系统的非线性动力学建模，得到了该场合下系统性状和特征；被动式加载时多余力主要与液压缸的作用面积和运动速度成正比，并在系统主要工作频率范围内起作用，提出了一种并联有源电液伺服阀的多余力补偿物理实现方案和一种速度负反馈加二阶微分形式的前馈补偿器算法，极大地抑制了多余力的影响；借助李雅普诺夫直接法，求解了系统稳定性条件并得到稳定性补偿的控制策略及其算法；设计了一种具有变增益的双幂次趋近律的滑模控制器，并借助了一次反步控制算法，克服了负载中弹性刚度值正负切换引起的输出力抖振，输出力稳态误差控制在1%以内；借助Narendra稳定自适应控制理论和系统动力元件的固有频率，设计了以主导极点为主要模型形式的控制策略，系统稳定工作频宽最高可拓展到10Hz；同时，探讨了电液负载模拟器的整体控制策略、电液负载模拟器实验系统实现和试验系统中作为被加载对象的电液位置控制系统在负值弹性刚度负载场合下的校正方法等问题。本项目工作成果为复杂负载高响应电液力控制系统精确控制和系统工作频宽拓展等研究提供了理论依据和可行的新方法；为电液控制运动平台、振动台、大功率舵机和大流量阀门开度控制系统的快速高精度加载试验等提供了有价值的理论和应用参考。