| The development of automobiles is one of the most important achievements of modern industrial technology.Automobiles have made significant contributions to meeting the needs of people’s daily mobility,which has promoted the progress of human beings highly developed industrial society.However,the application of huge amount of automobiles all over the world has generated and is continuing to cause serious environmental problems.Air pollution,global warming and the rapid decline of the earth’s petroleum resources have gradually become the focused issues.The development and application of new energy vehicles have thus become one of the solutions for energy issues in countries around the world.Motor controller,vehicle controller and battery management system are the three main control systems for pure electric vehicles.The motor controller is directly related to the running performance and energy efficiency of pure electric vehicles,so it is the focus of this research.In this paper,the dynamic mathematical model of induction motor is analyzed and discussed.The motor control algorithms including voltage frequency control,vector control,direct torque control and model predictive control are studied and discussed.The hardware platform of motor controller for pure electric busis designed.The vector control and model predictive control algorithms of motor controller for pure electric vehicles is developed and implemented on the micro processor chips.A field weakening algorithm and overmodulation algorithm suitable for pure electric vehicles are proposed to improve the voltage utilization and torque output capability.Three levels of system protection logic are proposed,including overvoltage and undervoltage protection,overcurrent and undercurrent protection,overspeed protection,etc.The communication protocol between motor controller and vehicle controller is addressed.The computer debugging software of motor controller is developed for experiments.The practical problems of pure electric vehicles,such as standing with zero speed on the slope,are proposed and solved.The developed motor controller was experimentally verified on a pure electric bus equipped with an AC induction motor.The main research work and contributions of the paper include the following aspects:1.The main motor control algorithms domestic and abroad are studied.According to the control system composition and operating conditions of pure electric bus,the motor controller algorithm for pure electric bus is designed,implemented and verified.The main algorithm of the motor controller is based on the field oriented control method.With the support of the algorithm,the motor controller can quickly respond to the request of the vehicle controller,and can achieve the driver’s desired target quickly and steadily.In this paper,the rotor flux oriented vector control algorithm and the coordinate transformation of the three-phase induction motor are used to match the variables in the model with the actual driving information of the pure electric bus.The algorithm modules of the motor controller are established,and the parameters are tuned.The experimental results verifies the accuracy and reliability of the algorithm models and enables the physical implementation of the motor controller.The field weakening control algorithm and the overmodulation algorithm are added according to the actual pure electric bus requiments,which improves the torque output and energy utilization of the motor.For the automotive-grade product of motor controller,the fault detection and driving protection mechanism is designed.A classified fault diagnosis architecture is adopted,which can effectively monitor the running state of the vehicle and handle the fault,and reduce the fault occurrence rate to improve the service life of the product.According to the adopted resolver combined with the core processor module,the accuracy of the speed measurement is calculated,and the parameter selection is optimized.The function of standing on the slope with zero-speed is added according to the driving demand,which can prevent the car from slipping on the slope.The motor controller designed in this paper can be modified for different type of vehicles,which can be matched with specialized control algorithms and support the application and optimization of advanced control algorithms.2.Based on the actual pure electric bus requiments,the hardware of motor controller for pure electric bus and the corresponding debugging software are designed and implemented.The main hardware components of the motor controller include a power supply module,an IGBT and its drive module,a micro processor module of motor controller,and a speed measurement module.In this paper,the communication protocol between the motor controller and the vehicle control system is developed for the pure electric bus that is actually running,and the CAN data channel for communication with the commanding computer is configured.The debugging software for desktop computer is designed and updated.The software can download the motor parameters and the control parameters of the motor controller to micro processor chips,and can simulate the driver’s driving signal,and can also collect the real-time running data of the motor for background analysis and optimization.3.Model predictive control algorithm is designed,implemented and verified in the motor controller for electric vehicles.The model predictive control algorithm uses the state space model of the induction motor to calculate the cost function by predicting the stator current,flux linkage and torque,and selects the optimal control voltage vector as the next control output.According to the requirements of the motor controller,the model predictive control algorithm architecture is established in the two-phase rotating coordinate reference.The flux linkage observer and the speedless sensor algorithm are designed and implemented.According to the actual microprocessor functions,the model predictive control algorithm with extended basic vector control set is proposed.Finally,the MPC algorithm is verified by experiments on the electric motor test bench and compared with the FOC algorithm.The experiments show that the model predictive control can achieve good control performance in the motor controller for electric vehicles,which deserves further study.The motor controller designed in this paper was finally applied on hundreds of pure electric buses as a successful product.The capability of the motor controller is that the torque fluctuation range is±5%,and the rotation speed can reach 2.5 times of the rated speed smoothly.These performance indicators meet the design requirements.I hope that the above research work can contribute to the development and implementation of motor controllers for pure electric buses in China. |
