Motor Speed Synchronization And Mode Transition Control For DCT-based Integrated Powertrain Systems

As a kind of hybrid systems,powertrain systems which integrates the traction motor and the transmission are capable of multiple operation modes.On one hand,it improves fuel efficiency and exhaust emissions.On the other hand,multiple modes and gears also pose requirements on performances of control strategies.Motor speed synchronization control during gear shift under the electric driving mode and mode transition control from electric driving to compound driving of a DCT-based integrated powertrain system are studied in this dissertation.Details as follows:a)Architecture design and operation modes analysisArchitecture of the powertrain system is determined based on screening common configurations according to functionality requirements.After that,operation modes,power flows and corresponding gear shift/mode transition processes are analyzed.Vehicle model is then established to provide a simulation environment for assessment of fuel economy and drivability as well as development of control strategy for gear shift/mode transition processes.b)Research on motor speed synchronization control during gear shift of the electric driving modeP+DO controller is developed for the motor speed synchronization problem during gear shift of the electric driving mode.Firstly,the control law is derived through the optimal control theory considering disturbances.After that,it is simplified by taking advantages of characteristics of the controlled system.Theoretical analysis proves that the simplified control law consists of two components:(a)proportional feedback;(b)disturbance compensation.The unknown disturbances are estimated through a timedomain disturbance observer and compensated in a feedforward manner.Explicit relationship between the feedback gain and the duration of synchronization,which is one of the performance metrics,is derived through model-based analysis.Furthermore,suggestions are given on calibration of the disturbance observer gain.These efforts make P+DO a“parameter-free” controller.To screen out the most appropriate speed synchronization controller for practical engineering use,components of P+DO are substituted by A&W,ISMC,and I,resulting in three new controllers: A&W+DO,P+ISMC,and PI,respectively.Performances of the four controllers are compared through simulations and experiments,whose results show that P+DO,P+ISMC,and A&W+DO all possess good transient performances provided appropriate parameters.In contrast,PI with fixed gains fails to attain both small settling time and overshoot at the same time.Regarding the number of parameters as well as the convenience of calibration,P+DO is advised to be used in practical projects.c)Research on mode transition control from electric driving to compound drivingAn open-loop control strategy with power interruption is firstly proposed.After that,two closed-loop strategies without power interruption are studied,classified by implementation of speed regulation of the crankshaft:(a)using the clutch;(b)using the engine.For the problem of engine torque control during clutch engagement,three options are compared:(a)shutting off the engine;(b)keeping the engine torque constant;(c)maintaining the control law of the previous phase,regarding acceleration variation and jerk amplitude.Simulation results show that the engine torque should be kept constant during clutch engagement.For the problem of disturbance torque estimation and compensation,an equivalent inverse dynamic model is proposed,which divides the motor torque command into three components:(a)torque for acceleration;(b)torque for compensation of known disturbances;(c)torque for compensation of unknown disturbances.Simulation results prove that the method is able to track the disturbance torque promptly and robustly.To tackle the discontinuity resulting from change of disturbance torque and system inertia at the end of the clutch engagement phase,strategies to reset the motor torque are proposed for three different circumstances,classified by how the engine speed approaches the odd shaft speed:(a)from upside;(b)from downside;(c)from tangential.Simulation results indicate that resetting the motor torque at the end of the clutch engagement phase with a proper value helps maintaining the longitudinal acceleration stable.The proposed control strategies are also applicable to other gear shift/mode transition processes which include phases like motor speed synchronization,clutch engagement,and load transfer.