Design of a filling ratio observer for a hydraulic retarder: An analysis of vehicle thermal management and dynamic braking system

Hydraulic retarders are auxiliary braking devices that reduce vehicle speed by converting its kinetic energy into thermal energy of a working fluid. This study analyzes the torque-output characteristics of a new type of hydraulic retarder and optimizes its control strategy under different braking conditions. The design of an observer is based on an analysis of the vehicle dynamic system to ensure that it sets the control target of the dynamic filling ratio for hydraulic control system. With the assistance of the observer, the hydraulic retarder can produce the required braking torque as quickly and as accurately as possible. This study simulates a feedback control system of the vehicle dynamic model with the observer. The results prove that even if the vehicle is driven under complex conditions wherein the slope of the road is changed, the observer effectively sets a control target of the filling ratio for the hydraulic control system. This mechanism strengthens the adaptability and accuracy of the hydraulic retarder control strategy.