利用空气弹簧低频减振特性良好的特点,提出了一种用于微振动控制的主动隔振单元,并利用该隔振单元构建了6自由度减振平台系统,建立了系统的运动微分方程式,并对系统在最优控制下的性能进行了仿真和实验研究,结果表明:所提出的主动隔振单元构建的减振平台减振效果高达了20 d B左右,不仅对中高频扰力具有良好的隔振效果,而且对低频和超低频扰力能进行有效的隔振,对精密制造和测量具有很重要的意义。
The control problems associated with vehicle height adjustment of electronically controlled air suspension(ECAS) still pose theoretical challenges for researchers, which manifest themselves in the publications on this subject over the last years. This paper deals with modeling and control of a vehicle height adjustment system for ECAS, which is an example of a hybrid dynamical system due to the coexistence and coupling of continuous variables and discrete events. A mixed logical dynamical(MLD) modeling approach is chosen for capturing enough details of the vehicle height adjustment process. The hybrid dynamic model is constructed on the basis of some assumptions and piecewise linear approximation for components nonlinearities. Then, the on-off statuses of solenoid valves and the piecewise approximation process are described by propositional logic, and the hybrid system is transformed into the set of linear mixed-integer equalities and inequalities, denoted as MLD model, automatically by HYSDEL. Using this model, a hybrid model predictive controller(HMPC) is tuned based on online mixed-integer quadratic optimization(MIQP). Two different scenarios are considered in the simulation, whose results verify the height adjustment effectiveness of the proposed approach. Explicit solutions of the controller are computed to control the vehicle height adjustment system in realtime using an offline multi-parametric programming technology(MPT), thus convert the controller into an equivalent explicit piecewise affine form. Finally, bench experiments for vehicle height lifting, holding and lowering procedures are conducted, which demonstrate that the HMPC can adjust the vehicle height by controlling the on-off statuses of solenoid valves directly. This research proposes a new modeling and control method for vehicle height adjustment of ECAS, which leads to a closed-loop system with favorable dynamical properties.
SUN XiaoqiangCAI YingfengWANG ShaohuaLIU YanlingCHEN Long
