Research On Continuous Sliding Mode Control Of Electronic Throttle System

With the rapid growth in human population,as well as advancement in modern technology,energy conservation and environmental protection is a necessity.This awareness has resulted into a demand for automobile systems with better engine performance,in terms of fuel efficiency and low emission.Electronic throttle(ET)system plays a significant role in actualizing this performance.It is very paramount to reducing environmental pollution and optimizing fuel consumption,because it controls the air-fuel-mixture by controlling air inflow into the system engine.The ET system is made up of various parts,such as the throttle body,sensors,gear sets and DC motor that controls the throttle plate opening.The ET system is a coupled nonlinear system,whose model is an approximate of the real system,so there are unmodelled dynamics which are not usually considered.Hence,it is difficult for conventional linear control methods to satisfy ET system application requirements.Therefore,this thesis considers the closed-loop performance of the electronic throttle(ET)system,and presents a higher-order sliding mode control scheme.The contributions of this thesis are highlighted as follows:Firstly,a new higher-order sliding-mode control approach that can provide finite time stability for uncertain systems is utilized in this thesis to improve the closed loop performance of the ET system,where the sliding variable has relative degree greater than one with respect to the control input.Generally,higher-order sliding-mode control retains the main advantages of conventional sliding-mode control and has the additional advantage that it can be used to curtail the chattering effect,providing more smooth control.It also provides better accuracy with respect to switching delays.A comparison between the conventional sliding-mode and higher order sliding mode control is made via numerical simulation and experimental verification.The implementation results demonstrate the practical importance of higher order sliding mode control to improving the position tracking performance of the electronic throttle system.Secondly,a novel observer based continuous terminal sliding-mode control method is developed to further improve the stability of ET system in the presence of external and internal disturbances.The application of the new higher-order sliding mode control requires more system information,that is the derivative and higher order derivatives of the ET system output,which are to be measured by sensors.Unfortunately,the ET system only have its throttle position information available for measurement.The speed information and acceleration need to be obtained by differentiation,which could affect the stability of the ET system,because differentiation of sensor signals usually result into noise amplification.Therefore,a universal finite-time observer is designed to estimate the unknown variables and total disturbances.The ET system output information,and observer estimations are utilized in the construction of the continuous terminal sliding-mode controller.The controller ensures finite-time convergence of system output to a predefined reference position,with a smoother control action.