Research And Optimization On The Key Technologies Of Secondary Regulation Hydrostatic Transmission Vehicles

Along with the rapid development of industrial technology in the word, the increasingly serious problem of energy shortage and environmental pollution requires automobile industries all over the world exploring and developing energy saving and clean automobile. Hydrostatic transmission with secondary regulation is a new kind of transmission technology, which changes the swash angle of hydraulic pump/motor in the constant pressure network to adapt to the load change. Hydraulic pump/motor has the characteristic of four quadrant work, which can regenerate and reuse the inertial and gravitational energy of load. Hydraulic accumulator has the advantage of higher power density and the ability to accept the high rates and high frequencies of charging and discharging, both of which are favorable for energy conversion and storage requirements during vehicle braking. In addition, hydrostatic transmission with secondary regulation has the advantages of continuously variable speed adjustment, easy to achieve positive inversion and prevent overload of engine and so on. Therefore hydraulic hybrid technology is well suited for luxury passenger cars, sport utility vehicles, light duty trucks and heavy-duty trucks. It is undoubtedly important to apply secondary regulation to developing and exploring new hybrid vehicles to save energy and protect environment. Based on the application of secondary regulation technology in hybrid vehicles, series hybrid vehicles of hydrostatic transmission with secondary regulation are studied and analyzed in depth and breadth in this article.After consulting a lot of related literatures and reference materials at home and abroad, this paper summarizes and compares the properties of the different energy storage technologies. This paper also analyses the advantages of hydraulic energy storage system and the characteristics of hydrostatic transmission hybrid technology. Furthermore, summarizes the development of hydrostatic transmission hybrid vehicles at home and abroadAfter studying the operation principle of hydrostatic transmission hybrid vehicles, vehicle mathematical mode and simulation model were established. Furthermore, a new type of hydrostatic transmission hybrid system configuration was proposed to improve vehicle efficiency and adaptability to the complexity of the road on the basis of analysis of the factors influencing the system efficiency, such as difference configurations, driving cycles and control strategies.After the analyzing the interactive influence of hybrid vehicle actual engineering constraints, vehicle performance design target and power systemic components, the matching relationship of key components and design guideline of hydrostatic transmission hybrid vehicles were researched. Simulation studies have shown that adaptive simulated annealing genetic algorithm multi-objective optimization method effectively distinguishes the key components optimal parameters values, substantial improving the performance of hydrostatic transmission hybrid system.The hydraulic regenerative braking strategy was designed according to the large power density characteristics of hydrostatic transmission technology, which reasonably distributes the front/rear axle braking forces and the relationship between regenerative braking force and frictional braking force according to braking intensity. Hydraulic regenerative braking system and frictional braking system work together to brake safely, and effectively regenerate braking energy. The"power following"+"thermostat"energy distribution strategy was designed and optimized by using the simulation model. The simulation results have shown that the energy strategy ensure the engine work in high efficiency area, effectively overcome the lower energy density of hydraulic accumulator and avoid frequent start/stop of engine.As to deal with the robust control problems against parameter uncertainty and load disturbance, discrete sliding mode control method is employed to design the robust controller of hydraulic regenerative braking system.The experimental research was done using hydrostatic transmission hybrid test bed. The experimental results shown that torque control method is well suit for hydrostatic transmission hybrid system, discrete sliding mode robust controller is better than PID controller and hydraulic regenerative braking strategy and energy control strategy are quite effective.