基于滑模控制的空气悬架车高控制系统研究

Investigation of Height Control for Air Suspension System Based on Sliding Mode Method

以提高空气悬架车高控制精度为目的,充分考虑空气悬架系统充放气过程的非线性特性,建立了气体管路流量特性方程,并结合变质量气体热力学定律,建立电磁阀开启和关闭时的空气弹簧充放气压力梯度方程,实现空气弹簧充放气过程的非线性特性数学描述,并进一步完成空气悬架车高升降的1/4车模型.针对充放气过程的非线性特性,基于微分几何理论,将车高升降模型通过状态反馈进行全局线性化,在线性域中设计滑模控制器,进而经过线性逆变换,得到原坐标系中的非线性车高控制算法.仿真试验表明,基于状态反馈线性化方法设计的滑模控制器,能够有效克服充放气过程的非线性特性,消除过充过放现象,显著提高车高控制品质和精度.

Aiming to improve the precision of vehicle height control in air suspension systems, the nonlinear character existing in the lift and lower process was deeply considered based on the thermodynamics laws for variable mass air system. It includes establishing the equations of air mass flow character through the solenoid valve and gas pipes, and also the equations of pressure gradient in the air spring. Based on these mathematical descriptions, a nonlinear quarter car air suspension model was established to describe the lift and lower process for the research of vehicle height control algorithm. To deal with the nonlinear character in the lift and lower process, the nonlinear model was globally linearized through the state feedback method based on the differential geometry theory. Then a sliding mode controller was able to be designed in the linear domain and then transformed in inverse-linearization ways to obtain the nonlinear control algorithm in the original coordinate system. The simulation tests show that, the proposed sliding mode controller designed based on the state feedback linearization theory, is able to handle the nonlinear character existing in the lift and lower process of air suspension system, can eliminate the over control and improve the vehicle height precision obviously.