| The traditional retarding device relies on one-way energy conversion to help the vehicle slow down and brake,there is a certain amount of energy waste,and it cannot be used for a long time.The two-way energy conversion technology of hybrid technology is used to realize auxiliary braking and energy recovery of the vehicle,reduce the friction loss of the main brake system,and assist the vehicle to start acceleration.The use of digital hydraulics in hybrid power systems,according to the braking needs,to achieve different displacement output,make the control system more flexible and control response time is shorter.Based on the above analysis,the research of this subject was carried out.In order to calculate the maximum braking torque required by the auxiliary braking system,the required displacement of the hydraulic pump/motor,the transmission ratio of the torque coupler,etc.it is necessary to obtain the engine braking efficiency,retarder braking torque,vehicle braking Parameters such as torque,engine gear ratio,combined drag coefficient,etc.Therefore,a test plan for the modified prototype was designed and the required parameters were obtained.On the premise of not changing the original vehicle power system,the hydraulic auxiliary brake system and its control strategy were designed.The simulation model of the whole vehicle was built under the AMESim environment.The simulation analysis was carried out under the conditions of Japan10-15 and NEDC to verify the auxiliary The feasibility of the braking system and the correctness of the control strategy.Designed and developed the torque coupling,control valve group,control system,and completed the prototype development.The research results of this paper show that,compared with the original vehicle eddy current retarder,the hydraulic assisted braking system can help the vehicle to brake,and can output different braking torques according to the actual braking demand,which has flexible control and high stability.Continuous operation for a long time can help the vehicle to go downhill at a constant speed when long downhill,thus avoiding the safety hazards caused by the vehicle using friction brake for a long time.Under Japan10-15 working conditions,the braking torque of the vehicle’s main braking system when the auxiliary braking system is involved is about 54.9% of the braking torque provided by the vehicle’s main braking system when the auxiliary braking system is not involved;in NEDC Under operating conditions,when the urban speed is low,the auxiliary braking system can independently complete the auxiliary braking.When the urban speed is high,the braking torque provided by the auxiliary braking system reduces the main braking system by about 46.6% The braking torque reduces the braking torque of the vehicle’s main braking system by about 41.6% when the auxiliary brake system is involved in braking in the suburbs.Under both working conditions,the friction braking strength of the main brake is effectively reduced,the service life of the main brake is extended,the vehicle safety is effectively protected,and the effect of fuel saving can be achieved;In a long downhill condition with a slope of 9% and an initial speed of 40km/h,the vehicle can rely on the auxiliary braking system to achieve a constant speed downhill,reducing the safety hazards caused by long-term use of the brake. |
