为解决电控空气悬架(electric control air suspension,简称ECAS)车身高度切换过程中的振荡及"过充"、"过放"现象,以空气弹簧特性为媒介,与车辆动力学相结合,对车身高度调节系统的进行建模。通过遗传算法优化车身高度调节系统PID的控制参数,提出一种新的积分分离PID控制策略。采用Matlab/Simulink搭建模型并对控制前、后仿真结果进行了对比。结果证明,所设计的控制方法能有效解决以上问题,优化后的车身高度调节系统能显著减少汽车振荡及干扰,操纵稳定性得到改善。
The current research of air suspension mainly focuses on the characteristics and design of the air spring. In fact, electronically controlled air suspension （ECAS） has excellent performance in flexible height adjustment during different driving conditions. However, the nonlinearity of the ride height adjusting system and the uneven distribution of payload affect the control accuracy of ride height and the body attitude. Firstly, the three-point measurement system of three height sensors is used to establish the mathematical model of the ride height adjusting system. The decentralized control of ride height and the centralized control of body attitude are presented to design the ride height control system for ECAS. The exact feedback linearization method is adopted for the nonlinear mathematical model of the ride height system. Secondly, according to the hierarchical control theory, the variable structure control （VSC） technique is used to design a controller that is able to adjust the ride height for the quarter-vehicle anywhere, and each quarter-vehicle height control system is independent. Meanwhile, the three-point height signals obtained by three height sensors are tracked to calculate the body pitch and roll attitude over time, and then by calculating the deviation of pitch and roll and its rates, the height control correction is reassigned based on the fuzzy algorithm. Finally, to verify the effectiveness and performance of the proposed combined control strategy, a validating test of ride height control system with and without road disturbance is carried out. Testing results show that the height adjusting time of both lifting and lowering is over 5 s, and the pitch angle and the roll angle of body attitude are less than 0.15°. This research proposes a hierarchical control method that can guarantee the attitude stability, as well as satisfy the ride height tracking system.
