Research On Coordinated Control Of Mode Transition And Energy Management Strategy For A Parallel Hybrid Electric Vehicle

Hybrid electric vehicles(HEVs)become one of the practical techniques to alleviate the pressure on resources and the environment in our country in the short term,which combine the advantages of both conventional vehicles and electric vehicles(EVs).In this dissertation,to improve the performance of the drivability,fuel economy and emissions,the main researches focus on the vehicle dynamic modeling,coordination control of the mode transition from the electric driving mode to the hybrid driving mode,energy management strategy,control system implementation of mode transition and energy management as well for the hybrid electric vehicle.Firstly,the simulation model of a parallel hybrid electric bus is set up in the MATLAB/Simulink using the forward modeling method,which consists of the engine,electric motor,automated mechanical transmission,battery pack,longitudinal vehicle dynamic model,etc.Considering the complexity and low-precision of the engine mean value model,a torque estimation method based on the least square support vector machine is proposed to model the engine dynamic characteristics.On this basis,estimation of distribution algorithm is applied to optimize parameters of the penalty factor C and kernel function width?.Moreover,a torque observer with optimal parameters is established to realize real-time and accurate torque identification of the engine.Secondly,the cause of coordination control for the mode transition is discussed,and the hybrid characteristics of the mode transition is analyzed in this dissertation.The transition from the electric driving mode to the hybrid driving mode is selected as the object,and a coordinated control strategy of mode transition based on hybrid system theory is proposed.On this basis,the mode transition can be divided into three phases.According to different control objectives,a fuzzy-PI controller is applied to regulate the engine speed,and an adpative sliding mode controller is applied to adjust the electric motor torque.Considering the uncertainty of system disturbance,a RBF neural network is applied to estimate the disturbance.The adaptive law is obtained and the stability of the system is also proved by the Lyapunov stability theory.The simulation results demonstrated that the proposed strategy is effective for reducing the torque fluctuation in the driveline and improving the performance of the drivability and driving comfort.Thirdly,the energy management strategy of the hybrid electric bus is transformed into a class optimal control problem with some constraints using Berman optimality principle.At the same time,the state variables,control variables,objective function and constraints of the problem are determined.To avoid deterioration of the dynamic performance during the solution process,an adaptive factor?is applied to correct gear-shifting curves,whose value is determined by the fuzzy logic control.In addition,iterative dynamic programming is employed to obtain the optimal control law over the CCBC cycle,which reduces the complexity in the time and space horizons.Considering the difficulty of the optimal law being applied in real vehicle,an adaptive neuro-fuzzy inference system(ANFIS)is proposed to model the nonlinear relationship between optimal solution and state variables of the hybrid powertrain,which achieves a set of control sequences with the system state changing.On this basis,the multi-ANFIS controller is set up to produce the optimal control law for the paralle hybrid electric bus.At the end,a hardware in the loop simulation platform for the hybrid bus is constructed,and the proposed energy management strategy is investigated using this platform.The simulation results demonstrated that the proposed strategy can achieve significant improvements in the fuel economy and emissions on the basis of the vehicle drivability performance and battery SOC-sustaining.Based on the digital signal processor MPC5744P,a control system of mode transition and energy management for the hybrid powertrain is built,which supply a lot informantion for the experimental platform verification of the proposed strategy.And then,the experimental studies are carried out,and the experimental results show that the proposed strategy is effective for reducing the torque fluctuation and vehicle jerk during the transition from the electric driving mode to hybrid driving mode.Specifically,the maximum jerk is less than 3 m/s~3.For the IDP-ANFIS,the fuel economy and emissions performance are improved significantly for the hybrid bus with real-time control requirement,which offers a new approach to optimize energy management strategy.