On The Design Of Robust Sliding Mode Control Method For Networked Systems With Incomplete Information

With the rise and wide applications of internet technology,the networked systems(NSs)have gradually penetrated into many areas of life.So far,the control and measurement schemes based on NSs have been widely used in the integrated navigation system,electro-hydraulic servo system,telemetry measurement,wind turbine system and so on.Besides,notice that the introduction of network environment brings lots of uncertainties to the measurement and transmission of information,such as sensor measurement losses,information scheduling,equipment failure,input nonlinearity,network attack and so on.It should be noted that the incomplete information mentioned above has not been received enough attention by the scholars,not to mention the insensitivity of the sliding mode control(SMC)on the specified disturbance,and there are still many critical and difficult problems to be solved.This thesis investigates the missing measurements,information scheduling(stochastic communication protocol(SCP)and event-triggered mechanism),actuator fault,network attack(Do S attack and deception attack)and other incomplete information situations,and then focuses on robust SMC problem for several types of NSs.The research framework of this thesis is carried out from the following aspects.1.Considering the incomplete information yielded by missing measurement,the problem of robust SMC for NSs with mixed time delays is studied.By introducing the Bernoulli distributed random variables,the phenomenon of missing measurements is described.Moreover,both the nominal probability and probability error are employed to depict the uncertainty of missing measurements probability.With the help of nominal probability information,a suitable sliding surface is constructed and the sliding mode dynamics is further obtained.Furthermore,by employing the equivalent transformation technique,the sufficient conditions guaranteeing the asymptotic stability of sliding motion are presented.Combined with the available packet,a novel robust sliding mode control mechanism based on the nominal probability is proposed.2.The robust H_?SMC problem is studied for classes of NSs,where the incomplete information caused by SCP scheduling is considered.Firstly,a two-state Markov mode is constructed to describe the Markov missing measurements.In order to improve the quality of network communication and avoid data confliction,the communication between controller-actuator channels is scheduled through SCP.Subsequently,by utilizing the Markov chain transition probability information corresponding to missing measurements,the sliding surface is constructed.Moreover,the SCP based SMC design scheme is proposed and the new Lyapunov-Krasovskii functional which depends on missing measurements mode and SCP mode is established to analyze the H_?performance of the closed-loop system and the reachability of sliding surface.3.Considering the incomplete information caused by equipment faults,the sliding mode fault-tolerant(SMFT)control problem is studied for a class of discrete time-delay systems with actuator faults.By introducing the fault-tolerant injection signal and augmentation technique,the observer of the augmented system is constructed based on measurement information.By designing fault-tolerant control injection signal,the finite-time convergence of sliding surface is ensured and the H_?performance of the error system is analyzed.To proceed with the procedure of analyzing the system performance,a new sliding surface based on decomposed state observer is developed.With the help of adaptive technique and considering the characteristic of input nonlinearity,a new robust adaptive SMC scheme is proposed to solve the actuator fault problem,while ensuring the asymptotic stability of sliding motion and reachability of sliding surface.4.The problem of sliding mode secure control is discussed for a class of NSs in the presence of incomplete information caused by cyber-attack and dead-zone characteristic.The event-triggered scheme scheduling in output channel and the cyber-attack occurring in network transition are discussed.Furthermore,the considered cyber-attack includes two cases which are described by introducing two independent random variables satisfying Bernoulli distribution.For the selected sliding surface,sufficient conditions are presented to ensure that sliding mode dynamics is(?)-secure in mean square sense based on delay-fractioning approach.In addition,combined with the dead-zone characteristic and measurement information,an adaptive sliding mode controller which can effectively circumvent the effects from cyber-attack and input nonlinearity is designed,while ensuring the reachability of the sliding surface.5.The maximum power point tracking problem is investigated for wind turbine via the SMC scheme.Firstly,the relationship between the aerodynamic power,wind speed and some other parameters is provided.Through the maximum power point tracking strategy,the optimal blade tip speed ratio and the blade pitch angle are given.Moreover,the expression of the ideal rotor speed is given subsequently by combining the relationship among the rotor speed,wind speed and the blade tip speed ratio.Furthermore,the model of the aero-turbine is established,and the discretized mathematical model is obtained by Euler discretization method.Combined with the SMFT scheme,an observer of the discrete aero-turbine system is constructed,and the injection signal is provided to ensure that the sliding surface is achieved in finite time.Finally,by using the second-order sliding mode technique,a new robust SMFT aerodynamic torque control scheme is proposed.