Research On Event-Triggered Control Strategy Under Network Environment

Control system based on wireless sensor networks become more and more popular,however,the traditional periodic communication and control methods in networked con-trol systems will lead to access constraints,affect system performance,and even cause system instability.On the other hand,for battery-powered wireless sensors and actua-tors,periodic communication can severely shorten the life of the whole system.Therefore,recent studies advocate using event-triggered communication to replace periodic commu-nication.Event-triggered mechanism can reduce the number of communication transmis-sion,improve network utilization and prolong the service life of battery-powered wireless sensor nodes with a small loss of system performance.In recent years,event-triggered control has become a popular topic in networked control systems,but there are still many types of control systems without corresponding event-triggered control strategies proposed.This paper is based on the latest research result of event-triggered control strategy.The contents and main contributions are as follows:(1)The event-triggered controller and the corresponding event transmission rule are designed for a class of stochastic system subject to state delay.The basic theories are approximate quadratic performance index and mean-square bounded theory.First,the event-triggered state feedback control scheme constrained by the approximate quadratic performance index is proposed which used the current state and time-delay state simulta-neously.Subsequently,an event-triggered output feedback control scheme is established which eliminates the influence of the state-delay terms according to the mean-square bounded theory.All the theorems are presented in the form of matrix inequalities.Fur-thermore,two event-triggered tuning parameters are provided for the event-triggered con-trol strategy.Finally,a numerical example is given to illustrate the effectiveness of the proposed strategies(2)Two novel event-triggered fault-tolerant control strategies are proposed for a class of stochastic systems with state delays.The plant is disturbed by a Gaussian process,actuator faults,and unknown disturbances.First,a special case about fault signals that are coupled to the unknown disturbances is discussed;and then,a fault-tolerant strategy is designed based on an event condition on system states.Subsequently,a send-on-delta transmission framework is established to deal with the problem of fault-tolerant control strategy against fault signals separated from the external disturbances.Two criteria are provided to design feedback controllers in order to guarantee that the systems are expo-nentially mean-square stable,and the corresponding H_?-norm disturbance attenuation levels are achieved.Two theorems were obtained by synthesizing the feedback control gains and the desired event conditions in terms of linear matrix inequalities.Finally,two numerical examples are provided to illustrate the effectiveness of the proposed theoretical results.(3)The event-triggered fault tolerant control for a class of state-saturated systems subject to stochastic faults,unknown but bounded disturbances,state saturations,and deception attacks are studied.After formulating stochastic faults,state saturations,and deception attacks,a hybrid system model is developed to facilitate analysis and design.An event-triggered transmission mechanism is proposed to decide whether the measurement values should be sent to the controller via wireless network.Since the sensor data is attacked by the adversary during the transmission,the actual measurement value received by the controller needs to be recalculated.Expressions of the dynamic output feedback controller are presented,and criteria are used to design a dynamic feedback controller to ensure that the system is uniformly ultimately bounded.To deal with the current problem,an algorithm is also developed and tested using the linear matrix inequality toolbox.Finally,a numerical example is given to illustrate the improvements of the proposed strategies.(4)A novel event-triggered scheme based on state partition for unstable systems is proposed.First,the event-triggered control system is modeled as a switched system with two modes:an autonomous system and a controlled system.The corresponding switch rules are also designed.Second,the entire state space is divided into two subspaces by two lines and each can be represented by a symmetric matrix.The two subspaces correspond to the two models of the switched system above.Based on the state par-tition and switched system model,the criteria for co-designing both the controller and the event-triggered scheme were derived to achieve uniform exponential stability.The proposed event-triggered scheme can save network resources in both the controller-to-actuator channels and the sensor-to-controller channels.It can also reduce the energy resources of wireless sensors,controllers and actuators.Finally,a numerical example is provided to demonstrate that global exponential stability can be guaranteed at the cost of only 50 percent of the network resources.