Architecture Design, Analysis And Mode Transition Research Of A Multi-mode Hybrid Powertrain Using A Single Electric Machine

The hybrid electric vehicle(HEV) is the most promising new energy vehicle due to the advantages in fuel economy, power performance, and driving range. However, the complexity in the electric drive system and power coupling mechanism improves the cost and reduces the reliability of the hybrid system, which is the key obstacle to HEV’s promotion. Therefore, it is of great significance to develop a high efficiency hybrid system with good technology of inheritance as well as stable and reliable performance.A novel single electric machine(EM) driven hybrid system architecture using double planetary gearsets and four automatic clutches as power coupling mechanism is designed. A series of research work is conducted. The assessment and analysis of fuel economy are fulfilled through comparative simulation and global optimization. The coordinated control of typical mode transitions is achieved using multi-phase feedback compensation and optimal control. Moreover, this dissertation also develops the hybrid controller and carries out the bench test validation.Synthetically analyzing the architectures worldwide, the hybrid systems can be divided into double EM schemes and single EM schemes. Considering the problems of system complexity and high energy conversion loss in double EM schemes, as well as the shortcomings of only one freedo m modulation in single EM schemes based on automatic transmissions(ATs), this dissertation designs a novel single EM hybrid system architecture using a successive-six-step design method. This is a system using double planetary gearsets and four automatic clutches as power coupling mechanism with sixteen operating modes. It inherits refined components of automatic transmission thus is very realiable and stable. It can transfer the engine power in purely mechanical paths and continuously modulate the engine speed or torque. On the basis of operating mode analysis, this dissertation performs the powertrain parameter matching, as well as the establishment of kinetic models in MATLAB/Simulink applying the modularized modeling method in ’plug and play’ structure, which is the key development platform for virtual analysis and control research.Fuel economy(FE) is the primary index for evaluating a HEV system. Aiming at improving the FE, this study develops a real-time control strategy(RTCS) composed of ’Mode Selection’ module and ’Torque Distribution’ module. Comparative simulation is conducted under various drive cycles worldwide both for the proposed single EM scheme and a typical double EM scheme in conjunction with the established models. The results show that the FE of them is close to each other. A quantitative analysis method for comparison of HEV FE is proposed and the reason for their comparable FE is obtained. Furthermore, global optimization of fuel consumption(FC) under comprehensive driving cycles is implemented using refined dynamic programming method, the 3.66L/100 km result demonstrates again and the fuel-saving potential of the new architecture. The 3.94% minor difference with real-time FC validated the effectiveness of the proposed RTCS.Driveability is another important index for evaluating the performance of a hybrid system. In this study, two typical mode transitions that have significant effects on driveability are selected for control and research. For the ’Electric to Compound’ mode transition, aiming at the problems of slow engine start and fierce jerk during clutch slip-stick, a coordinated four phase control method is proposed using sub-control system in each phase and fuzzy gain scheduling PID as the feedback compensator in torque control. For the ’Compound to Compound’ mode transition, optimization of jerk and clutch wear is fulfilled using optimal control method under the prerequisite of ensuring mode transition response speed. Results from closed- loop simulation and bench test indicate that, the proposed method can ensure the driving stability, improve the speed of response, and reduce the clutch wear simultaneously, i.e., expected control results can be realized.Besides, this dissertation developed an Infineon XE166 high-speed chip based vehicle electronic control unit(EC U) using the development tools from ETAS of Germany. The hardware-in-the- loop(HIL) test results are quite close to the simulation results, which demonstrate that the vehicle ECU realizes the designed real-time control strategy very well. Finally, the test bench is constructed. Based on this test bench, the tests of basic operating mode realization and the mode transition control validation are carried out. Test results show that the designed coordinated control method achieves the expected control objectives, thus has good practicability.