Research On The Structure Of The Program And The Energy Control For Parallel Hydraulic Hybrid Vehicles

As the science and technology develops and people’s living standards increase,more and more vehicles has been used in people’s daily lives. As the growth of theamount of vehicles is increasing rapidly, the energy required and consumed isgrowing at the same time. Meanwhile, auto exhausts have caused severe pollutionand have a direct impact on our health. Therefore, the development of automotiveenergy-saving technologies and new energy vehicles have become our priorities.Hydraulic hybrid vehicle is a representative of the energy-saving and new energyvehicles. It has got increasingly more of attention due to its great energy saving inthe recent years. Hydraulic hybrid utilizes hydraulic accumulators, hydraulic pump(motors) and other hydraulic components as energy storage, energy conversioncomponents. It takes advantage of the high power density of the hydrauliccomponents, and fully recycle the kinetic energy consumed by traditional vehiclesduring the breaking phase through friction brakes, then release the stored energywhen accelerate, thus reduce the exhausts and save energy. Hydraulic hybridtechnology is especially suitable for large trucks, engineering vehicles, city busesand other heavy vehicles as they stop and go frequently.Under the funding of the Science and Technology Development Program inJilin province--"The research of secondary regulation technology in automobileenergy saving"(Project Number:3R111R482414), this dissertation researches onparallel hydraulic hybrid vehicles and mainly involves the following work:1. It analyzes the characteristics of several mainstream hybrid technologies andgives a detailed introduction to the development trend of the hydraulic hybridtechnology and its advantages both at home and abroad in recent years.2. By analyzing the three main structures of hydraulic hybrid vehicles, it identifiesthe parallel structure to be our focus. The traditional parallel hybrid structure is toplace the torque coupler on the main shaft. However, the pre-biaxial parallelarrangement mentioned in this dissertation puts torque coupler between the engineand the transmission. This structure allows the hydraulic pump (motor) to work in amore efficient area, thus incredibly improves the dynamic performance of thevehicles.3. It builds the mathematical models of the main components on the parallel hydraulic hybrid vehicles such as engine, clutch, transmission, torque coupler,hydraulic pump (motor) and accumulator. It also analyzes the kinematics of vehiclesand models the vehicle brake system, thus lay the theoretical foundation for thesimulation and experiments on the next stage.4. The control strategies for parallel hydraulic hybrid vehicles are described indetail. Based on the analysis of the two types of vehicle power supply power flow, itintroduces the hydraulic hybrid engine start-stop system and establishes logiccontrol strategies, which is based on fuzzy control algorithms. It also analyzes indetail several common vehicle operations and establishes the corresponding fuzzyrules, vehicle regenerative braking control strategy and driving control strategy.5. It uses AMESim to create the models of parallel hydraulic hybrid vehicles andthe vehicles without hydraulic hybrid. Real vehicle parameters are setcorrespondingly in the models in order to better simulate the actual vehicleoperations. The Simulation results show that the hydraulic hybrid system canachieve effective control of the engine starting, as well as in the situations withmultiple start-ups. In the simulation of Six-Cycles,10-15Working Condition,ECE+EUDC Conditions, and UDDS Condition, a series of simulation curves areobtained, such as speed, acceleration, accumulator pressure, hydraulic pump (motor)flow coefficient, driving distance, the fuel consumption of the vehicles with andwithout hydraulic hybrid systems. Additionally, the oil-saving rates of the parallelhydraulic hybrid vehicles under different conditions are obtained.6. Though the real vehicle modified test, it conducts a series of performance testson the vehicles with and without parallel hydraulic hybrid systems, includingoil-saving performance test, dynamic performance, braking performance testing, etc.By comparing and analyzing the data obtained from the two types of vehicles, theenergy saving effect of the parallel hydraulic hybrid vehicle is more apparent inthe aspects of vehicle acceleration, braking performance, etc. Regarding the systemresponse time, hydraulic hybrid system not only meets the requirements, but alsohas a shorter response time during charging and discharging. On the other hand, theroad tests also prove the accuracy of the theoretical models, control algorithm andthe simulation models. It lays the foundation and provides a reference for furtherstudy in the future.In summary, this dissertation has a thorough research on the energy controlstrategies of parallel hydraulic hybrid vehicles. It verifies relative theories and thevehicle control strategies by creating models and real vehicle tests. It provides a guidance to the promotion and application of the hydraulic hybrid technology.