Research On Hybrid Model Predictive Control For Dual Planetary Gear Hybrid Electric Vehicle

The power split hybrid electric vehicle has advantages of series type and parallel type,and has been widely recognized now.With characteristics of two degrees of freedom,the planetary gear set is often used as the power coupling device in the hybrid electric vehicle to realize decoupling of engine torque and speed from the wheels.However,the complex structure of planetary gear set coupling system increases the difficulties in design of energy management control strategies.Specially,the working process of planetary gear set coupling system often involves the coexistence of discrete state switching and continuous state evolution,which puts forward higher requirements for the design of energy management strategies.In this paper,a new type of dual planetary gear hybrid electric vehicle is taken as the research object.On the basis of the comprehensive study in its working characteristics,the hybrid characteristics of energy management system are revealed.The hybrid model predictive control strategy is further proposed to optimize the output power of different power sources in order to improve the fuel economy of the vehicle.Firstly,the working characteristic analysis and model construction of the dual planetary gear hybrid electric vehicle are studied.With the lever method,the torque and speed coupling models of power coupling device are established,the power split characteristics are analyzed,and the transmission efficiency of the system is also deduced based on the idea of power balance.On this basis,the operation modes of the hybrid electric vehicle are divided according to the actual driving conditions,and the dynamic relationships of components under different operation modes are studied.By combining theoretical modeling method and experimental modeling method,the main power component models,vehicle longitudinal dynamic model and driver model are built based on the MATLAB/Simulink platform.Secondly,the hybrid dynamic model of the energy management system for dual planetary gear hybrid electric vehicle is established.The common hybrid system modeling methods are introduced.The hybrid structure characteristics of dual planetary gear hybrid electric vehicle are studied in depth.Meanwhile,the piecewise linearization of the nonlinear models such as the battery,motors and other components are achieved by using piecewise affine technology.On this basis,the discrete working mode and piecewise affine boundary are described by introducing logical variables.Combined with the different operation constraints,the operation mode set of the hybrid system is integrated by adopting the mixed logical dynamical(MLD)modeling method.Finally,based on hybrid system description language HYSDEL and its supporting software,the compilation of the mathematical model of the energy management system is completed,and the standard form of the MLD model energy management system is formed.Thirdly,the optimal design of energy management strategy for dual planetary gear hybrid electric vehicle is studied.After fully mastering the principle of predictive control,the model predictive control is determined to be used in optimal design of energy management strategy.By setting appropriate optimization target,the optimal operation point of engine is decided,and the decision process is reduced to a kind of constrained optimal control problem in finite time domain.Mixed integer quadratic programming(MIQP)is adopted to obtain the solution of optimal control sequence in finite time domain.Simulation results show that,compared with the control strategy based on rules,the proposed control strategy improves vehicle fuel economy by 7.6% and 8.4%,respectively,under UDDS and HWFET conditions.Finally,the hardware in the loop test of the energy management strategy is conducted.The rapid prototyping development of energy management strategy is realized based on D2 P platform,and the compilation and download tasks of control plant model are completed based on NI hardware in the loop test equipment.The test platform is constructed by connecting the controller to the test cabinet with hard wires and bus.On this basis,the effectiveness of the energy management strategy is verified.Results show that the proposed energy management strategy is effective and superior,which lays a foundation for the product-level development and application of the controller.