Research On Braking Torque Control Of Front-mounted Hydraulic Hybrid Vehicle

With the consumptioin of energy and the aggravation of air pollution,energy saving and emission reduction are becoming an increasingly important research direction.The crane often works in the urban conditions,which causes more frequent start and more severe load changes.And it has practical significance to carry out research on hybridization of energy-saving and emission reduction.The core technology of a hybrid vehicle is the braking system.For the hybrid vehicle,how to achieve good energy recovery under the premise of ensuring the safety of the brake is the premise for vehicles to select the hybrid configuration and the composite control.An important factor to ensure the safety of the brake is to realize the control of the braking torque of the vehicle.This paper studies the control of the braking torque of the hybrid crane with selected configuration based on the school-enterprise cooperation project "crane hybrid power system development".The main work of research is as follows:1.The hydraulic hybrid technology and its characteristics are analyzed.The full researchs have been done on status of the brake system of hybrid vehicles at home and abroad in recent years and test technology.2.According to the working characteristics and structure of the crane,the front-mounted hydraulic hybrid system is selected as its structure compared with the existing hybrid configuration for the research on energy-saving and emission reduction technology.And the common operating conditions of the front-mounted vehicles are analyzed.3.The auxiliary brake torque provided by the hydraulic pump/motor in the front-mounted hydraulic hybrid vehicle may change with the gear position of the transmission,which may easily cause a safety accident.The corresponding solution was proposed.The key of the torque control is divided into two parts on the basis of studying the structure and working principle of the front-mounted vehicle brake system.One is the displacement control of the hydraulic pump/motor and the other is recognition of gear position of manual transmission when braking.The specific solution is as follows:(1)The transmission relationship between key components such as electro-hydraulic servo valve,variable cylinder and swash plate is analyzed,and the mathematical model of hydraulic pump/motor displacement control is established.(2)The torque distribution brakes strategy under different braking conditions of the front-mounted vehicle is built,which combines the strategy of front and rear wheel brakes.And braking condition of the vehicle with the gear is discussed.(3)It is proposed to determine the gearbox position during braking phase by the corresponding relationship between speed of input shaft of gearbox and speed of output shaft of gearbox for the problem that the manual gearbox is not equipped with the gear position sensor and cannot directly detect the gear position.(4)The theoretical model of vehicle braking torque control under different braking conditions of front-mounted vehicles is established on the basis of the above.4.The braking simulation model of the front-mounted hybrid vehicle is built in the AMESim software environment,and the performance of the hybrid braking system is verified by simulation analysis.5.The feasibility of constant torque control during front-mounted vehicle braking is verified and the relevant performance parameters such as energy recovery rate?energy loss rate are obtained through the experimental car,and do tests for the energy loss in the system due to leakage of some components,which builds the basis for further research on front-mounted hydraulic hybrid vehicles.