Steady And Transient Optimal Control For A Dual-mode Power-split Hybrid System

This thesis investigated optimal control strategy for a power-split hybrid system whose key component was a device composed of three planetary sets and two clutches.Firstly,its speed and torque charasteristics were analysed and four martrices for both EVT1 and EVT2 mode were obtained.Based on experimental data and components’ physical characteristics,a simulation model was bulit in MATLAB/Simulink.A rule-based energy management was developed to improve fuel economy of the PS system and off-line simulation validation was conducted.Two engine control schemes were presented,in the first scheme ECU controlled engine speed and engine target torque control was fulfilled by two motors;in the other scheme ECU controlled engine torque and engine target speed control was fulfilled by the generator.Through simulation,we found that the sceond scheme was better in terms of regulation time and overshoot in transient process.Secondly,the dynamic coordination problem was researched.Its defination was wided to all dynamic process in which engine target torque changed significantly.The working state of two motors was analysed in two EVT modes and by the analysis who should play the toruqe coordination role was determined.And the specific value was calculated through the torque matrices.Through simulation we found that by the strategy output torque was smoother.Thirdly,a key technique which was torque estimation was researched.Two eatimation methods were developed,the first one consisted of a mean-value model and a Kalman filter;the other was based on neural network.Both achieved a high estimation accuracy.Finally,a transient optimation strategy was presented to further improve fuel economy of the PS system.A Neural Network Model based Predictive Control(NNMPC)algorithm was applied and by solving a quadratic cost function the optimal injected fuel quantity was obtained which decreased fule consumption further.