Intelligent sensorless ABS for in-wheel electric vehicles

The design of electric vehicles (EVs) is increasingly based upon using the in-wheel technology. In this design, the use of a separate electric machine at each corner of the vehicle provides unique opportunities for innovative vehicle control strategies. In this paper, a sensorless antilock braking system (ABS) is proposed that eliminates the need for the installation of separate conventional ABS sensors and saves the costs associated with the installation and maintenance of those sensors for in-wheel EVs. The proposed ABS exploits the information carried by the back electromotive force (EMF) of the electric machines of the in-wheel vehicle to obtain accurate wheel speed estimation at each wheel and conduct road identification simultaneously. A wavelet-packet denoising method is used to maintain the accuracy of wheel speed estimation in the presence of noise. In addition to sensorless wheel speed estimation, the proposed ABS is capable of road identification by analyzing the back EMF signal using discrete wavelet transforms. The design was realized and fully tested using actual ABS hardware. The results of the sensorless technique were compared with a commercial ABS sensor. The experimental results showed that the sensorless ABS can adequately replace the conventional ABS sensor in in-wheel EVs and significantly improve the performance of the ABS.