| Current energy and environmental issues as a constraint to the development of modern industry are the important factors, and the automobile industry is the major factor of the environmental pollution and energy consumption. Decreasing energy consumption, reducing vehicle exhaust pollution on our environment, energy-saving and emission reduction of motor vehicle research, such works have important strategic significance. Through a large number of different countries’studies of the national environmental protection and energy saving technology to the automotive industry, the results show that hybrid electric vehicle (HEV) is the most industrial, commercial prospects for mass production of environmentally friendly cars, and which has gotten a lot of attention. The plug-in hybrid electric vehicle (PHEV), using of high-capacity battery to improve hybrid electric vehicle’s (HEV) performance, further enhance the degree of people’s attention. In this dissertation, a company’s plug-in hybrid MPV is discussed.This dissertation is divided into seven parts.1. Based on the mechanism of energy saving of the hybrid electric vehicle, the contribution and potential of the energy-saving of the crucial parts, the writer analyses the energy-saving way of the HEV. Through research and analyze domestic and international research and development trends and government support policies of the hybrid electric vehicles, the direction of the development of hybrid vehicles is determined. The current hybrid development process, development tools, optimization methods and test equipment are also discussed in this dissertation.2. The advantages and disadvantages of the hybrid electric vehicles with different types and different structural forms are analyzed, ultimately the power train of the plug-in hybrid electric drive system with two clutches is chosen as the finally power train. In this power train configuration, the electric motor is located between the two clutches, and this configuration solves the problems of the vehicle’s function which includes hybrid vehicle limp home, security, shift performance and brake energy recovery and other issues.3. Comparing and analyzing the critical components of the Hybrid electric vehicle, the type of vehicle’s components are chosen combined with the development trend of critical components and current technology. The design method of DOH (degree of hybridization) is introduced and an idea DOH is chosen base on the crucial part’s parameters.4. Based on bench test data of crucial components, in the Matlab/Simulink environment, the Pre-transmission parallel configuration with two clutches (before and after electric machine) model is established using the model building method which combins theoretical analysis and bench test data, which provides a necessary simulation platform for the research and development of the control strategy.5. Control strategies of plug-in hybrid electric MPV with two clutches (before and after electric machine) has a huge impact on vehicle’s fuel economy, so this strategy operates the engine in one of three regions depending on the combined power requirement needed by the road and the battery. This dissertation mainly discusses the basic control logic of the propelling systems, such as the engine ON/OFF control logic, the modes switching and torque distribution between pure electric mode and hybrid mode, down and up logic of transmission, the modes switching and torque distribution between regenerative braking mode and the mechanical braking torque, and the strategy of cooling systems of electric motor and engine. Through planning the energy flow of the plug-in hybrid electric MPV, rationally distributing the engine torque and controlling the engine work in the high efficiency area, all these works found a solid foundation for parameters optimization of vehicle control strategy.6. The parameters of control strategy of the plug-in hybrid electric MPV are optimized under the global optimization algorithm. Traditional optimization methods and expertise are confronted with the problem such as high cost, long time and local optimization, so Design Of Experiment (DOE)—Approximate Model—Optimization Algorithm is chosen as the optimization method in this dissertation. First, sensitivity analysis of ten crucial variables of the control strategy is done using DOE method, The Design Variables used in the control strategy are A (SOC below which the engine is turned on), B (SOC above which the engine is turned off), C (Once on, Minimum time for the engine to stay on), D (Once off, Minimum time for the engine to stay off), E (The wheel torque must be above wh_trq_above_turn_on for this amount of time before the engine turns on), F (The wheel torque must be below wh_trq_below_turn off for this amount of time before the engine turns off), G (min power for the engine to turn on), H (max power for the engine to turn off), I (Charging is forbidden if the SOC is above this value), and J (Charging is allowed if the SOC is below this value). The hybrid electric vehicle’s fuel economy is selected as the test target, and to explore the design space and identify significant design variables, a101-level DOE study is carried out using Optimal Latin Hypercube method, and the main factors are gotten from main effect and interactive effect calculations.Then, through analyzing the construction methods of the approximate model, one Approximate Model is established base on the input and output relationship using Kriging model method, which avoids the high strength simulation, reduce the iterative time. Five points are used to analysis the tolerance between PSAT simulation and Approximate Model, the results show that the tolerances between the PSAT simulation test and the Approximate Model simulation are less than5%, it is clearly seen that the Approximate Model can substitute the direct simulation test commendably.Finally, global optimization algorithm (multi-island genetic algorithm) is used to find the optimum using the Approximate Model in this dissertation, it is proved that Design Of Experiment (DOE)—Approximate Model—Optimization Algorithm is the feasible and effective optimum design method.7. Based on global optimization results, the simulations of the plug-in hybrid electric MPV are carried out under the drive cycle50×ECE,100×ECE,20×EUDC,10×NEDC,1×FTP,20×Japan1015,10×UDDS and10×US06. Finally, the MPV’s basic functions such as pure electric propelling and regenerative braking are validated.The simulations of the plug-in hybrid electric MPV are carried out based on optimization results. The parameters of the engine, transmission, motor and battery used in the simulations are bench test values. The10×NEDC driving cycle is divided into three vehicle modes which are celeration, deceleration and steady state. Percentage of the torque, speed, power and efficiency of the engine and motor,and the Percentage of battery current, voltage, power and efficiency are analyzed under the three vehicle modes. Fuel economy of the plug-in hybrid MPV are also calculated under the50×ECE,100×ECE,20×EUDC,10×NEDC,1×FTP,20×Japan1015,10x UDDS and10x US06drive cycle. Finally, the real MPV’s basic functions such as pure electric propelling and regenerative braking are validated.Summary of this thesis points out the engineering methods and ideas which can be used for reference in plug-in hybrid electric MPV design, and the shortages of this thesis needing for further study are also described. |
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