Driving Of Wheel Motor In Electric Vehicle Based On Low Resolution Hall Sensors

Energy shortage and aggravation of environmental pollution have brought opportunities of the development of. As it integrates drive motor, mechanical drive and brake device to the wheel hub, Wheel motor, which, combines motor and vehicles, can greatly simplify the mechanical transmission parts of electric vehicles, thus earning widespread attention. Permanent magnet synchronous motor drive technology applied to wheel motor is studied in this paper. Given its characteristics, low resolution position sensor, namely, Hall position sensor instead of the traditional high resolution position sensor such as optical-electricity encoder is used to detect the position of the rotor. However, as the three-phase Hall position sensor can only output six position signals, its detection effectiveness and accuracy have yet to be improved. This article focuses on the methods to use low-resolution position sensor. Both hardware and software platforms are developed and built for wheel motor control and drive. Then experimental research is completed.In this paper the vector control principle of permanent magnet synchronous motor (PMSM) is studied firstly. Then its mathematical model and the formula of3/2transformation are given in static three-phase coordinates and rotary two-phase coordinates. Also, the principle of space vector pulse width modulation (SVPWM) is introduced. Aiming to improve the accuracy of rotor position and speed estimated by low resolution Hall effect sensors, several different methods to obtain high resolution rotor position from the low resolution Hall sensors are described and compared with experimental test. Then a novel method to adjust rotor position gradually rather than immediately force to reference angle while sector switching and a new algorism to adjust reference angle automatically are proposed in this paper.Then the experimental platform based on TMS320F28035is built, and the various parts of hardware of wheel motor drive system are introduced respectively, such as the driver circuit, switching power supply, sampling circuit, signal conditioning circuit, protection circuit, etc. On the hardware platform, the configurations of the peripheral in TMS320F28035are completed, based on which the control software platform and its subroutines are set up to achieve speed and electric current double closed-circle control of wheel motor. Furthermore Communication program based on SCI and CAN, AD sampling programs, velocity and angle calculation based on Hall position signal,3/2transformation based on angle, SVPWM control, PI regulator controlled by rotational speed and torque, etc are also included on this platform. And the protections of over current/voltage/heat are also considered.And finally, some elementary experimental test and adjustment are completed in order to improve the performance of the driver system; the experimental results indicate that the new method is capable of improving rotor speed and position with higher accuracy and lower error. And the driving system basically meets the design requirements and lays a good foundation for further optimization and experiments in electric vehicle applications.