The Simulation Study Of Hydraulic Retarder’s Braking Characteristics Based On Simulink

With the rapid development of the transportation in our country, the workload of the heavy vehicles braking system increases, especially during the long downhill driving, which could make the braking system fail and cause accidents. With the rapid development of all kinds of auxiliary braking device, hydrodynamic retarder gets more and more attention because of its advantages. But the research of hydraulic retarder in our country lags behind foreign countries and the products are basically depend on import. In this paper, the main parameters of the hydrodynamic retarder are selected and calculated, and the simulation of its braking characteristics based on Simulink is conducted, which provides some references for the product engineering and the parameter optimization.In this paper, firstly, the classification of vehicle auxiliary braking device is introduced, and the structure, principle and characteristics of all kinds of auxiliary braking device are expounded. Secondly, the parameters of the hydrodynamic retarder are selected and calculated and the mathematic model of braking torque is built based on the beam theory and similarity theory, and its 3D model is built and the fluid flow model is exported according to the related parameters. The submodels including the braking, engine exhaust braking, driving resistance are integrated and the vehicle braking simulation model is constructed. The auxiliary braking characteristics of the hydrodynamic retarder was simulated under different working conditions: smooth braking, downhill road and engine braking.Through the analysis of the results of simulation, the following conclusions can be drawn:(1) the hydraulic retarder has good braking effect under a certain driving speed. The higher the rate of liquid, the stronger braking performance of the hydraulic retarder, and the braking effect is better associated with the engine braking.(2) The braking effect of the hydraulic retarder is not obvious when the speed is less than 20km/h, at this moment, the wheel braking is needed to brake stop.(3) The hydraulic retarder can make the vehicles maintain a steady speed when driving downhill, and the steady speed is independent of the initial speed, but is related to the gear of the hydraulic retarder and the slope.(4) Under a certain rate of liquid and the slope, the fixed gear is corresponded with a uniform velocity. The downhill speed can be adjusted under the constant speed gears. In order to ensure the speed fluctuation is small and the time that the vehicle spends to reach a preset speed is short, the hydraulic retarder control system must be of high precision and fast response speed.