Studies On The Electro-hydraulic Proportional Control Technology On Charging And Discharging Of Vehicular High Power Hydraulic Retarder

Hydraulic retarder is one kind of auxiliary braking device, which is widely used onheavy vehicles. The adjustment of its braking torque is achieved by controlling the fluidcharging into the chamber to an accurate amount at the exact time. Therefore, how tocontrol the charging and discharging of fluid is one of the key factors that have significantinfluence on the retarder’s overall performance. Traditional mechanical-hydrauliccharge/discharge control system has a complex structure, slow response speed, few controlfunctions and other drawbacks. It is gradually replaced by electric control system whosecore components are electro-hydraulic/pneumatic valves.This dissertation takes a certain kind of high-power hydraulic retarder as the researchobject. Based on the analysis on foreign leading techniques, a new control system isdeveloped, which is centered on electro-hydraulic components, and which can achieve afaster response and easier control. After that, based on the result of a3D flow fieldsimulation, a mapping relationship between the character of the flow field and the brakingtorque is established. The parameters and control strategy are determined by analyzing thestable mechanical state of the hydraulic components so that the control strategy and thehardware are combined together. The control system can achieve multi functions at thevehicle level, such as quick braking response, constant torque braking,hydraulic-mechanical combined braking, constant-speed control at ramp-driving conditions,etc. Additionally, the computer simulation models of charging and discharging logic controlunit, the hydraulic circuit system, the output character of the retarder, and the dynamic stateof the vehicle are developed respectively on AMESim simulation platform. A dynamic jointsimulation of the vehicle is conducted for ramp braking process, and the control strategy isrefined according to the simulation results, in order to achieve those functions mentionedabove better. Finally, evaluation of the newly developed control system is given bycomparing it to the simulation results of the original mechanic—hydraulic control system.The comparison results show that the Electro-hydraulic Proportional Control systemcan reach the level of the original mechanical control system in terms of response speed,steady control on braking torque and hydraulic-mechanical combined braking. Also，it canrealize the new control function-constant-speed control at ramp-driving conditions. It hasadvantage on the simplicity of hydraulic circuit structure, control function diversity andcontrol flexibility, compared with the original system.