Research On Permanent Magnet Brushless DC Motor Drive Control System Used In Small Electric Vehicles

With strong support of the state for the development of new energy vehicles, small electric vehicle (EV) develops rapidly and has broad market prospect because of its extremely low price and usage costs. As one of the three key components, motor drive controller is critical to the drive performance and cost of electric vehicle. Just under such a background and combined with the specific needs of the joint venture project, the paper developed a set of permanent magnetic brushless DC motor (BLDCM) drive control system used in small electric vehicles.Firstly, mathematical model of the drive control system was established through analysis of BLDCM’s working principle. On the basis of the model, both the hardware and software architecture of the drive control system was designed. In the process of the hardware architecture design, the type of matching motor, power source, interface and board structure were determined. Furthermore, the hardware block diagram was designed. According to the actual operating conditions of electric vehicles, the software architecture was divided into three stages which include launching, running and braking. In the launching stage, staircase method was used to set up the given value in case of overcurrent of BLDCM during start-up time. During braking stage, combined with mechanical brake method, energy regenerative brake method was taken to obtain the maximum energy feedback rate. As for the running stage, considering the driving requirements of EV, speed drive control strategy was determined as control method through analysis of the different mechanical characteristics of BLDCM under three different drive control strategies. These three strategies include voltage strategy, torque strategy and speed strategy.Secondly, under the speed drive control strategy, double loop PI control algorithm based on load segments was proposed to overcome the poor ability to reject disturbance in traditional double loop PI control. The simulation model of drive control system was established respectively in both two algorithms using Simulink software and the superior anti-jamming performance of double loop PI control algorithm based on load segments was verified by comparing the speed response curves.Thirdly, on the basis of the previously theoretical analysis and simulation, the software and hardware of drive control system was detailedly designed and realized. The design of the entire system aimed to reduce costs, improve security and reliability, enhance endurance ability and increase comfort.Finally, taking advantage of the existing experimental condition, the paper built the test platform and tested the drive control system prototype both in empty board mode and no-load mode. Through analyzing the results, the rationality and practicality of the hardware and software design were validated.