Design Of Wheel Speed Signal Processing Moudle With FFT/IFFT And CAN Communication Functions

Indirect tire pressure monitoring system(TPMS)、anti-lock braking system(ABS)、anti-slip regulation system(ASR)、active yaw control(AYC)、electronic stability programcontrol system(ESP)and dynamic stability control system(DSC)use wheel speed signalafter processing to calculate the speed, acceleration/deceleration, wheel slip rate, yawrate or understeer quantity and so on. The wheel speed signal noise at high speed is thecommon problem of the control systems.This paper designs a wheel speed signal processing module, including a centralprocessing module, a analog input module, a analog output module, a CANcommunication module, a serial communication module and a voltage regulator module. Itrealizes the acquisition, processing and transmission of wheel speed signal. MCU programis compiled with CodeWarrior5software and the wheel speed signal is collected. Then iscarried on the fast Fourier transform (FFT) and the wheel speed signal is filtered infrequency domain. Afterwards Fourier inverse transformation (IFFT) is conducted and wecalculate the wheel speed and the number of pulses according to the processing wheelspeed signal. Finally the wheel speed is transmitted to the CAN bus. This paper makes awith visual basic6.0software, and realizes the connection between the PC program andthe CAN bus through the USBCAN-II dual intelligent CAN interface card, real-timemonitoring the changes of wheel speed and the number of pulses on the CAN bus.Vehicle tests show that the number of wheel speed signal is very close to thetheoretical number after going through the wheel speed signal processing module. Most ofthe interference signal is eliminated.