Comparative Study on Servo Control Technology of Liquid Discharging of Hydrodynamic Retarders

The liquid discharge valve control system is the key to ensure the hydrodynamic retarder play its auxiliary braking role, for the current problem of unstable flow and slow response of the liquid-controlled liquid discharge valve, respectively, to build a predictive model of the liquid control valve and servo-electric cylinder valve discharge control characteristics, for the inlet pressure fluctuations, control chamber pressure or sudden changes in the inlet pressure and other operating conditions, the outlet flow of the liquid discharge valve simulation calculations, comparison calculations show that The static control characteristics and dynamic control characteristics of the servo-electric valve are greatly improved compared with the liquid-controlled drain valve, because the liquid-controlled drain valve is controlled by the pressure control valve spool position, and the high speed interaction of the retarder wheel cavity inside the leaf grid leads to pressure fluctuations inside the wheel cavity, thus causing the spool to vibrate and the outlet flow rate to fluctuate, while the spool displacement of the drain valve driven directly by the servo motor is more stable and the outlet flow rate fluctuation is smaller. The spool displacement driven by servo motor is more stable and the outlet flow fluctuation is less. Combined with the vehicle driving dynamics model and retarder braking characteristics model, the control strategy is developed from the vehicle level, and the simulation analysis is carried out for the typical working condition of constant torque braking. The calculation results show that the hydrodynamic retarder braking system using servo-electric cylinder valve can adjust the braking torque more quickly and the torque fluctuation is small. The research results show that the solution of using servo motor to directly drive the discharge valve spool can effectively reduce the spool vibration, resist the fluctuation of the inlet pressure, and improve the stability of the outlet flow, so as to achieve fast and accurate adjustment of the braking torque of the retarder output..