Research on Composite Braking Strategy of Pure Electric Commercial Vehicle on Downhill Low-Adhesion Road Considering Rainfall Intensity

<div class="section abstract"><div class="htmlview paragraph">As a distributed wire control brake system, the electro-mechanical brake (EMB) may face challenges due to the need to integrate the actuator in the limited space beside the wheel. During extended downhill braking, especially on wet roads with reduced adhesion, the EMB must operate at high intensity. The significant heat generated by friction can lead to thermal deformation of components, such as the lead screw, compromising braking stability. This paper focuses on pure electric light trucks and proposes a tandem composite braking method. This approach uses an eddy current retarder (ECR) or motor to provide basic braking torque, while the EMB supplies the dynamic portion of the braking torque, thereby alleviating the braking pressure on the EMB.</div><div class="htmlview paragraph">First, a driver model, tire model, motor model, and braking models are developed based on the vehicle's longitudinal dynamics. In addition, the impact of various factors, such as rainfall intensity, road slope, ramp length and vehicle speed, on the road adhesion coefficient is analyzed. Combined with road conditions and driver intentions, three state variables—vehicle speed, battery state of charge, and braking intensity — are employed as control inputs. A fuzzy controller is then designed to distribute the basic braking torque between the motor and retarder. Additionally, a slip ratio controller is developed to dynamically adjust the braking torque of the electro-mechanical brake, preventing wheel lock-up. Finally, simulations are conducted using MATLAB/Simulink to validate the effectiveness of the proposed composite braking method.</div></div>