零重力模拟气动悬挂系统的建模及恒压控制

为模拟空间结构地面动力学测试时的零重力环境,针对研制的气动悬挂装置(PSD)采用比例流量阀开发了高精度的恒定气压控制系统.在分析了系统原理的基础上,建立压力控制系统的非线性数学模型.模型包含了比例阀的动力学特性、阀口流动的非线性、气缸容腔的压力动态和由实验结果拟合的气体泄漏.针对实现恒压控制的目标,采用输入输出线性化方法得到相对阶为2的等价系统,由于模型具有参数不确定和未建模动态特性,设计了基于观测器和等效控制的模糊滑模变结构控制器(FSMC).实验结果表明,设计的控制器对负载变化、气源压力变化、活塞运动和外部干扰均具有较强的鲁棒性,稳态压力波动小于26 Pa,实现了高精度的恒压控制.

Modeling and constant pressure control of pneumatic suspension system for zero-gravity simulation

A high precision constant pressure control system using proportional flow valve was developed for a pneumatic suspension device (PSD) in order to simulate zero-gravity environment for dynamic test of space structures. The nonlinear mathematical model of the pressure control system was built, which consisted of valve dynamics, flow nonlinearities through the valve orifice, pressure evolution in cylinder chambers, and leakage model based on curve fitting using experimental values. The equivalent model with relative degree of 2 was achieved by using input-output linearization approach. A fuzzy sliding mode controller (FSMC) was developed combined with equivalent control and observer of the valve orifice area due to parametric uncertainties and unmodeled dynamics. Experimental results show that the controller has good robustness against the influences of payload, air supply pressure, movement of the pistons and exogenous disturbances. The steady-state pressure fluctuation is less than 26 Pa, which verifies the validity of the method.