Research On Air Suspension Controller

Air suspension system is the most advanced one among the existing vehicle suspension systems. It can reduce noise of whole vehicle caused by vibration, decrease the dynamic load of wheels, improve the ride comfort and protect the road surface. In recent years, it has an extensive application in high-level buses, heavy trucks and limousines. However, the research into active control suspension system of air suspension is still in experimental stage and is technologically immature. This dissertation has made research into air suspension controller and also analysized and designed the control algorithm of controller, relevant actuator, electronic control unit (ECU), related transducer and test platform.The optimal adaptive algorithm has origirally been proposed for the control algorithm. Such an algorithm divided the control algorithm into two parts: offline part and online part. The core of offline algorithm is based on LQG algorithm. On the base of linear system, it has integrated the requirements for comfortability and handling to establish the quadratic performance index, so as to obtain the optimal feedback, and to form the optimal controlling system. While the core of online part is based on Lyapunov Reference Model Adaptive Algorithm. The reference model is the optimal system obtained by the offline algorithm, which can eliminate the impacts of time variation and linearization of suspension system at different work location by using different reference models and utilizing the features of adapive algorithm. Meanwhile, as the adaptive algorithm meets the requirement of Lyapunov stability, it can stablize the system. Such an algorithm is featured by conciceness and clear physical meanings.A design scheme for cascaded connection of adjustable electromagnetic vibration absorber and fixed hydraulic vibration absorber have been brought into the actuator of active air suspension. The design provides easy adjustment and rapid response for electromagnetic control system. Meanwhile, owing to the consideration of structure, the hydraulic vibration absorber can be used to consume partial power, whereby to reduce the volume and difficulty in manufacture of electromagnetic vibration absorber and to improve the reliability of the system. It also tests the performance of electromagnetic vibration absorber by home-made testing system.Drive circuit used for acceleration transducer has been designed for testing unit of suspension system. This dissertation has designed a differential transformer type of displacement transducer and its drive circuit, and enployed displacement testing system to test the performance of the displacement transducer.A hierarchical structure based on main controller and executive controller has firstly been put forwards to the controller frame, improving the suspension systen in safety and reliability by allocating different functions to controllers.The suspension test platform is an important condition in the controller reseach. In this dissertation, a test platform has been designed, and an optimum design has been performed for the hydraulic servo system in the suspension test platform, and the electronic control system has been analysized and designed.Basing on the above-mentioned research, this dissertation has presented the comprehensive strategy for the air suspension control, analysized the different requirements of different movement state of automobiles on air suspentions, and proposed the overall scheme for the realization of comprehensive control strategy in the frame of hierarchical controller.