Research On Energy-saving And Stability Control Of H-type Distributed Drive Electric Vehicles

Under the background of the rapid development of China’s automobile industry and the increasing pressure of oil demand and environmental protection,electric vehicles have become an important development direction of China’s automobile industry.With the advantages of ordinary electric vehicle,distributed drive electric vehicle has higher transmission efficiency and drive redundancy,which can further improve the economy and stability of the system through torque distribution,and has become a research hotspot in recent years.As a special distributed configuration,"H-type distributed drive electric system" not only inherits the advantages of ordinary distributed drive electric system,but also further has a more compact structure,excellent trafficability and off-road ability,which is of great research significance.However,it often works on off-road,beach driving and other severe conditions.The working location is remote and the operating environment is poor.As a result,it has a high requirement for the endurance and stable driving ability of the vehicle,so energy-saving and stability are the core of the system control.Nevertheless,there is little research on H-type distributed drive electric system in the existing literature,and there is no complete reference on energy-saving and stability control for the system.Due to the uniqueness of the configuration,the research of ordinary distributed drive electric system can only provide some references and cannot be transplanted completely.Therefore,by considering the special driving form of H-type distributed drive electric system,this paper studies the energy-saving and stability algorithm for the system.Then,to prevent interference between energy-saving and stability algorithm,an integrated control is carries out,and finally a hardware in the loop test platform is built for real-time testing.The main research contents of this paper are as follows:1)The model of H-type distributed drive electric system is established.First,under the environment of Matlab/Simulink,the body dynamics model,tire model and power source model of H-type distributed drive electric system are established respectively,and compared with the results of mature commercial software Truck Sim to verify the accuracy of the model.Then,to ensure that the vehicle can follow the desired speed and trajectory,a driver model based on single point preview and PID control is further established,which provides a simulation basis for subsequent energy-saving and stability control algorithm.2)The energy-saving control algorithm suitable for H-type distributed drive electric system is developed.First,the application of the traditional energy-saving control allocation method based on the minimum motor power loss(MMPL)algorithm is analyzed and improved,and its shortcomings is explored.Then,by considering the influence of lateral force in the steering process,the generation mechanism of steering resistance is deduced,and the energy-saving torque distribution method with minimum comprehensive energy consumption(MCEC)is established,which can improve the economy by optimizing the motor working point and steering resistance.Compared with the MMPL algorithm,it is verified that the MCEC algorithm can obtain better energysaving effect.3)A hierarchical stability control algorithm based on model predictive control(HCMPC)is designed.First,according to the structural characteristics of the system,the two degree of freedom reference model of the system is deduced,thereby obtaining the reference of stability control.Then,a HC-MPC algorithm is designed.The upper layer uses model predictive control to obtain a stable additional yaw.In this layer,the piecewise affine(PWA)tire model is introduced into the prediction model,which comprehensively considers the linear and nonlinear characteristics of tires without increasing the computational complexity and the accuracy of the prediction model is improved.The lower layer distributes the motor torque by establishing the optimal distribution function,which can comprehensively coordinate the distribution of torque,stable yaw demand and system drive/braking characteristics.Finally,the proposed HC-MPC algorithm is tested and compared with the control effect of traditional hierarchical stability control algorithm based on PID(HC-PID).4)The integrated control for energy-saving and stability algorithm and hardware in the loop test are carried out.First,the improved phase plane stability interval judgment method is adopted to divide the stability boundary of the system,and the quantitative evaluation method of vehicle stability is designed.Then,the system interval is divided,and the integrated control is coordinated with the interval type for the system,and the integration effect is simulated and tested.Finally,a constrained quadratic programming solver for the integrated algorithm is proposed based on the active set method,and a hardware in the loop test platform is built to verify the control effect of the integrated algorithm in real-time condition.