Active Wheel System Based Electric Vehicle Dynamics Analysis And Integrated Control

With the electrification and intellectualization of vehicle systems, the requirement of revolution for vehicle chassis is increasing. The key features of this tendency are the vehicle dynamic control methods turn to be spatial and three-dimensional within one integrated solution. The active wheel technology which integrated with functions of driving, braking, steering as well as suspension is an effective candidate for the innovative evolution of vehicle system. The main purpose of the active wheel technology is to extract the dynamic control assembly from the vehicle body and integrate these longitudinal, lateral and vertical dynamics modules within in-wheel motor for vehicle. By the means of this method, the vehicle dynamics control system is improved with reliability and effectiveness, and the functionalities of different chassis system could be decoupled with the avoidance of contradictions between different vehicle dynamics control objectives. Thanks to the ideal of active wheel, the advantages of “high functionalities with low system coupling” could be achieved.To maximize the performance and coordinate the functions of active wheel chassis system, this dissertation investigated the analysis and control methods for active wheel, which improves the dynamics performance of the electric vehicle equipped with the active wheel chassis system. This research could supply the theoretical basis and technical support for the future electric vehicle, and the main works including:① In-wheel motor driving and vibration excitation mechanism analysis for electric vehicles. The in-wheel motor is one of the key actuator for the active wheel system, the control method of in-wheel motor is discussed based on the study on the driving and vibration excitation mechanism for electric vehicles propulsion and ride comfort purpose.② Electromagnetic active suspension actuator characteristics study and control. The linear motor is another key actuator in the active wheel system. In the practical working scene, the linear motor exhibits nonlinear characteristics such as friction, force ripple, power limit and magnetic saturation. The influence and improve control method for these nonlinearities are investigated for a better active suspension performance.③ Electromagnetic active suspension optimization and parameters match. The electromagnetic active suspension integrated within the active wheel system could effectively resolve the ride comfort and stability contraction. However, the energy cost problem should be considered. The combined optimization of performance and energy cost is conducted for a better application prospect of active wheel system.④ Modeling of the full vehicle system with considerations of multiple DOFs coupling. Due to the integration of longitudinal, lateral and vertical dynamics control modules, the vehicle with active wheel chassis requires a complete and unified dynamics model for further analysis and control. The vehicle model with 4-wheel driving, 4-wheel steering and 4 active suspension is established to illustrate the features of active wheel chassis system.⑤ Electric vehicle stability analysis based on multiple objectives. Based on the active wheel integrated features of longitudinal, lateral and vertical dynamics control, the coupling relationships between the electric vehicle lateral stability and anti-rollover stability are studied, meanwhile the role of road excitation in the stability analysis is also considered.⑥ Electric vehicle control methodology based on active wheel system. The control methodology of chassis system constituted with four active wheels is studied for the stability control. The 4-wheel steering and electric stability program as well as active suspension is implemented. Also the coordination of different stability control methods are discussed. The “high functionalities with low system coupling” feature of active wheel is highlighted based on the integrated spatial and three-dimensional control of vehicle dynamics.In the end, the research is concluded, followed by the introduction of the characteristics and the innovation of the whole thesis. Besides, the possible problems that need further study are pointed out.