Research On Nonlinear Control And Its Application In Vehicle Powertrain Systems

With the development of automotive industry, more and more new vehicle tech-nologies are introduced and updated, which increase the degree of control freedom andsystem coupling in automotive systems, and increase the map calibration workload anddifculty in engineering. To reduce the development cycle and cost of automotive con-trol systems, application of nonlinear control method in automotive electronic controlsystems has become a research trend. However, nonlinear control methods is facing en-gineering applications bottlenecks including large computation, difcult to simplify, highimplementation costs. Aiming at the research status and challenges, in this paper, railpressure control problem in direct injection gasoline engine is first considered, accordingto the fuel rail system characteristic and the algorithm engineering requirements, a newnonlinear control method, called’Triple-step method’, is proposed to solve rail pressurecontrol problem. Then the implementation strategy of rail pressure controller based onTriple-step method which is based on map characteristic is formulated, and the controllerperformance is verified by the engine electric control system hardware in-the-loop plat-form and engine test bench. In order to verify the Triple-step method in other system, ashift process controller is developed in vehicle power-train system.Firstly, for solvingrail pressure control problem in GDI engine, the Control-orientedmathematical model including high pressure pump, fuel rail is established through theanalysis of system mechanism composition and working principle. Then the Backsteppingnonlinear controller is designed for rail pressure control system in non-singular points byvariable substitution and the control in singular point is designed for making the systemback to non-singular state. To verify the validity of the controller, we establish the railsystem simulation model in detail. The simulation results under diferent conditions showthat the rail pressure control system proposed in this paper has good steady trackingperformance, and can meet the requirement of controller design.Secondly, according to the problem of engineering realizing Backstepping controller,a new nonlinear controller design method, called”Triple-step”, is proposed. With this method, the controller can be designed as the form of”steady control, feed-forward controland error feedback control”. The structure and physical meaning of control law are veryclear. The important point is that controller gains depend on the system states, so thecontroller is gain scheduling. In order to illustrate the design idea, we derived the triple-step controller for one-order and two-order afne nonlinear system. Then the method isused to design the controller in three cascade nonlinear system and two order multi inputmulti output nonlinear system respectively.Next, Triple-step method is applied into design rail pressure tracking controller inGDI engine. Through considering the system disturbances and modeling error, parameteruncertainties and so on, robustness of the closed loop system is analyzed in the frameworkof the ISS theory, and the principle of selecting the controller parameters is given. The railpressure controller based on Triple-step is validated by of-line simulation under diferentoperating conditions. On that basis, the engineering implementation of the Triple-step isdiscussed, and the verification strategy of rail pressure control system and implementationscheme of the control law are made, which includes the transformation between controlleroutput and the control angle of pressure control valve, the calculation of steady statecontrol map, the reference dynamic feedforward control map and feedback control map.Rely on GDI engine electric control system HiL and engine test-bench from FAW Co.,Ltd. R&D Center, the Triple-step map controller is verified under diferent engine speedand engine load, the test results show that the pressure controller deduced by Triple-stepmethod has strong engineering practicability and validity.Finally, according to the nonlinear parametric varying in powertrain system, Triple-step method is applied to deal with shift control problem for Dual Clutch Transmission,by analyzing dynamic in the shift process of the transmission. Considering the nonlinearand parametric factors of systems such as the clutch friction characteristics, hydraulichysteresis characteristics, and the engine speed and so on, the system dynamics model isestablished, and the clutch speed tracking control strategy based on Triple-step methodis proposed. In the framework of Triple-step controller, the system varying parametricdoes not afect the controller structure. Moreover, the control gains are state-parameterdependent. The efectiveness of the controller is verified by the vehicle simulation modeland DCT control Hardware in the Loop platform, the experimental results show that thecontroller has good Shift quality.From the theoretical analysis and application in vehicle control problems, it canbe initially explained that the proposed nonlinear control methods is correct and it hasguidance for engineering practice. Nevertheless, the research work is still needed to furthercomplete:1) To extend the Triple-step method to a more general or other forms of non- linear systems, and to further improve the theoretical analysis;2) Further to discuss theimplementation scheme of three-step engineering;3) the further experimental validationstudy of Triple-step method in real vehicle.