Hydraulic retarder torque control for heavy duty vehicle longitudinal control

This paper studies the hydraulic retarder torque control strategies for heavy duty vehicle longitudinal control to reduce the abrasion of the friction brake. A hydraulic retarder whose oil volume rate is controlled by a pneumatic system is modelled. A hierarchical controller is developed for longitudinal control. In the upper controller, the target total brake force is calculated and then distributed on the friction brake and the retarder. In the lower controller, two retarder torque control strategies, PID control and mixed PID and sliding mode control, are employed and compared. Simulations are conducted with varying vehicle mass and varying desired vehicle velocity. Results show that the mixed PID and sliding mode controller has better speed tracking performance, robustness and torque control accuracy.