Event-triggered Mechanism Based Control Of Complex Dynamic Networked Control

Cascade control(CC)is an effective strategy to improve the control performance for it with double control loops.Most of the disturbances are designed into the inner loop,which can be attenuated quickly by the inner loop of the CC system.The outer control loop is mainly responsible for the steady performance of the systems.The components of feedback control systems,such as sensors,controllers and actuators,are connected through the networks,which is called networked control systems(NCSs).In modern large scale industry control area,NCSs have many applications,such as aircraft and space shuttle,nuclear power stations and high-performance automobiles.The control loop of CC systems closed via a communication network is called a networked cascade control systems(NCCSs),which possess the advantages of both CC systems and NCSs.NCCSs have become one of the most important control architectures and have been applied to many industrial systems,such as power plants,chemical plants,underwater vehicles.In this paper,the main work is as follows:Firstly,this paper deals with the event-triggered control for networked cascade control systems.Different from the conventional event-triggered schemes by predetermining a fixed threshold to reduce the data-releasing rate,this paper proposes a novel event-triggered mechanism in an adaptive way.Under this ETM,it has the following merits: 1)The data-releasing rate of the system remains a lower level so as to save the limited network bandwidth;2)The reliability of the control system can be enhanced since the threshold of ETM is increased with the elapse of time.Based on the proposed ETM,an integrated model of networked cascade control systems with consideration of multiplicative stochastic nonlinearties and actuator failures is established.Sufficient conditions are obtained to ensure the mean-square stability and stabilization of the networked cascade control system under study.Finally,two examples are exploited to show the effectiveness of the proposed method.Secondly,this paper investigates the problem of dynamic output feedback control for networked nonlinear systems.A novel event-triggered mechanism is proposed by introducing a new event-triggering condition.Compared with the existing ETMs,this ETM has at least three merits: i)The data-releasing rate can be further decreased,leading to reduction of network loads;ii)During the time when the system is disturbed by external signals,this ETM can release more sampled data to be transmitted to the controller.As a result,some better dynamic performance for the closed-loop system can be achieved;and iii)Wrong decision-making on data-releasing can be avoided due to a new definition of the error in ETM.Under this ETM,sufficient conditions are derived by employing the Lyapunov-Krasovskii functional method so that both the controller parameters and the ETM parameters can be designed.An example with four cases is given to show the effectiveness and superiority of the proposed method.Thirdly,the variable period sampling control system is studied and an event-trigger ed mechanism based on variable period sampling is proposed in this paper.The main innovations of this mechanism are: 1)The ETM not only determines the sending rate of data packets,but also determines the sampling period of the system.2)On the one hand,the system is disturbed by the external signals,this ETM can choose a relatively small sampling period to sample more data packets and release more data packets to the controller for better dynamic performance.3)On the other hand,when the system tends to be stable,the ETC will use a relatively large sampling period to reduce the number of sampling data packets and release fewer data packets which will save the system's computing resources and reduce the network burden.Based on the proposed mechanism,a comprehensive model for the ETM and variable-period sampling control is established.Then sufficient conditions for the mean-square stability of the system are obtained.Finally,an example is used to prove the effectiveness of the proposed method.