Multi-Model Based Hierarchical Switching Control For Vehicle Longitudinal Motion

As an important subsystem of the advanced vehicle control and safety systems(AVCSS), the vehicle longitudinal motion control technology has received more and more attention due to the critical traffic safety problems. The complexities of the vehicle longitudinal dynamics result in large model uncertainties and the conventional robust or parameter adaptive control methods can hardly ensure good control performances such as control stability, trackability and accuracy. To solve the above problems, a robust multi-model hierarchical switching control method and its application are studied in this thesis for implementation of the vehicle speed and acceleration control systems. And the vehicle speed and acceleration can be controlled rapidly and exactly in the presence of large model uncertainties based on the proposed method.A multi-model hierarchical switching control method based on robust control theory is established firstly. Under the framework of the robust control system, a switching index function by estimating the system gain of the uncertainties between the model and the plant is proposed, the corresponding multi-estimator and the switching logic are designed, and the exist conditions and design methods of the robust controller set are given. The robust stability and the disturbance attenuation ability have been validated by theoretical analyses and simulations.For the vehicle speed controller and acceleration controller of the vehicle longitudinal dynamic system, the linearization approach at working point and the inverse model approach are used to obtain the linear models of the vehicle longitudinal dynamics respectively. Based on the model sets, the vehicle speed and acceleration controllers are designed by the proposed method and some simulation tests have been conducted to evaluate the performances.To validate the effectiveness of the proposed method, an experimental vehicle platform based on CAN bus is constructed by developing the electronic control assistant braking system, the CAN protocol of application layer, and the CAN-nodes. Compared with the old one, the new platform improves the expand and information share abilities.Furthermore, the performances of the vehicle speed and acceleration control systems are investigated by experiments on various vehicle and environmental parameter conditions. Compared with the controllers designed by the parameter adaptive control method and PID control method, the controllers have the better robust performance. It is an effective way to solve the problems of the vehicle longitudinal motion control system resulting from model uncertainties.