Research On Design Methodology And Optimal Control Of The Electromechanical Coupling System In Hybrid Powertrain Based On Two Planetary Gearsets Configuration

The architecture design and optimal control of the electromechanical coupling system is the key technology to improve the fuel economy of hybrid electric vehicle.The hybrid system with the planetary gear as the coupling mechanism has a variety of working modes,which improves the system efficiency with compact structure,has become the most promising development design.However,due to the the complexity and diversity,the coupling configuration based on two planetary gearsets with multimode hinders the proposal for the new power split hybrid system.Therefore,a comprehensive design method of hybrid system based on double planetary gearsets coupling mechanism is proposed,which plays an important role in the design and optimization of both two motor and generator and single motor type hybrid architecture.In this dissertation,a multi-mode electromechanical hybrid configuration based on double planetary gearsets mechanism is designed by a systematic design methodology and then the research of optimal control is also carried out.The key of the design process is mapping the characteristic between a basic compound lever configuration and coupling mechanism dynamics.The design method is implemented by two stages.The feasible schemes are evaluated with the term of the fuel economy based on an instantaneous power optimization strategy by modeling and simulation.The influence of the operating modes on the economic performance is summarized from the simulation results.Based on the model predictive control(MPC),dynamic coordination of the torque is realized in the transient process of the multi-mode power split hybrid system mode switching.The simulation showed the improvement of the drivability and finally verificated through the semi-physical platform testing.In order to solve the above problems of the multi-mode hybrid system,the main research contribution are as follows:Firstly,the basic configuration of the hybrid powertrain is analyzed.By mapping between the compound lever model and the double row planetary gearsets,a methodology of a multi-mode power split hybrid system design is established.Compared with the large-scale calculation based on the brute-force method,the design method decomposes the design space to eliminate the invalid connection and inefficient scheme.By analyzing and comparing the mechanical efficiency,three basic configurations with two motor generator are proposed as the multi-mode power split hybrid system “Minimum architecture”.The methodology can also apply to multi-mode hybrid system with single electric motor.Secondly,as the fuel economy is the primary design goal of the program screening process,a common energy management strategy needs to ensure the optimization of performance while reducing the calculation of the load.Compared with the global optimization DP algorithm,the equivalent consumption minimum fuel consumption strategy can satisfy the real-time requirement,and the control strategy can be regarded as the necessary and sufficient conditions with the minimum value for the fuel consumption under the condition of electricity balanced.Therefore,this kind of instantaneous power optimization algorithm is used as the sub-optimal real-time algorithm as the unified control frame of the multi-mode power split hybrid system.On the basis of this framework,the simulation analysis of the fuel economy is realized,and compared with the single power split mode,the multi-mode power split hybrid system over different cycles can decrease the fuel economy by 5% ~ 15%.The single eletric machine hybrid powertrain has a slightly higher fuel consumption but lower cost.Drivability performance is another important index of hybrid powertrain,especially during the mode switching problem of multi-mode power split type hybrid system.In this research,the drivability of transient process is taken as the optimal object,switching from the pure electric drive to hybrid drive mode.The control strategy based on the model predictive control method is established to follow the switching speed of the model as the target,and the method of rolling optimization and correction is used to coordinate the control of the engine during the switching process,and also the clutch and motor torque output,and a typical two-planetary gearsets hybrid power transmission switching from the pure electric mode to the proposed hybrid mode,is respectively verified,through the simulation platform and semi-physical test bench.It is shown that the proposed control method can guarantee the smoothness of the mode switching and reduce the clutch slip loss.The contribution of this dissertation is proposing the design methodology of multimode electromechanical coupling system.Based on the research of fuel economy and drivablity performance,the optimization control both in quasi-steady and transient process are carried out.Through the combination of simulation and experiment,the relevant research work is completed.The methodology of a comprehensive and systematic forward design optimization is important for the development of a particular power-split structure and also innovative design platform for optimal control.