Application of fuzzy logic in constant speed control of hydraulic retarder

Hydraulic retarders are extensively used in commercial vehicles because of their advantages, such as their large braking torque and long continuous operating hours. In this article, the structure and working principles of hydraulic retarders are introduced, and their dynamic characteristics are analyzed. The theoretical model of a hydraulic retarder is then established based on the dynamic analysis of a vehicle driving downhill. The braking process that involves the hydraulic retarder is divided into three stages. Moreover, the filling ratio controller of the hydraulic retarder is designed by adopting fuzzy control theory to control the braking torque of the vehicle while driving downhill. The vehicle dynamic model and constant-speed control model were then established in the MATLAB/Simulink environment. The simulation results showed that the fuzzy logic controller designed in this study has good constant-torque control and anti-inference performances, which can accurately and immediately produce braking torque to satisfy the braking requirement, thereby enabling the vehicle to drive downhill at a constant speed. As a result, the control strategy designed in this article can lead to significant improvements toward a safe road transport.