Skid control of small electric vehicle with hydraulic-mechanical hybrid brake system (Effect of ABS and regenerative brake control on an icy road)

In this paper, an active safety device for skid control of a small in-wheel electric vehicle that uses a hydraulic-mechanical brake system (HMBS) is proposed. An anti-lock braking system (ABS) which is a basic skid control method is difficult to install at the driving tire because the space is insufficient. To improve the stability and the safety of the small electric vehicle with two in-wheel motors, we have constructed a simulation model of the HMBS with ABS and regenerative brake control. During braking, when skid occurs, especially on an icy road, ABS will maximize the slip ratio and cornering force, thus, assuring the stability control of the vehicle and eliminating the possibility of accident. However, due to the rigidness and low response performance of the rear mechanical braking system, ABS is still not enough to maximize the slip ratio and cornering force of the rear tire. To obtain the optimum slip ratio and cornering force at the rear tire, we proposed the regenerative brake control timing. During braking, we consider that an in-wheel motor at the rear tire will produce the regenerative braking force. The regenerative brake control timing operates similar as ABS. When the slip ratio increased more than the optimum value, the regenerative brake is turned off and the excessive energy is used to charge the battery. On the other hand, when the slip ratio decreased more than the optimum value, the regenerative brake force is again restored. The effectiveness of our proposed model has been evaluated by a MATLAB/Simulink The results of the numerical analysis indicate that the combination of the HMBS with ABS and regenerative brake control can prevent the vehicle to skid and improve the stability of the vehicle.