Active Disturbance Rejection Control Of Event-Triggered Networked Control Systems

With the rapid development of communication technology and the improvement of computing capacity,control systems have advanced from centralized to open distributed,networked control systems(NCSs)emerging as the times require.Since the NCSs have many appealing advantages such as easy maintenance,modularization,lower cost and increased flexibility,they have been widely used in industrial production,intelligent transportation,unmanned aerial vehicles,wind turbine system,telemetry measurement,and other fields.However,the involvement of the network induces some communication restrictions in the transmission process of data information,such as time delay,etc.Besides,NCSs are inevitable affected by disturbance.There is no doubt that the networkedinduced delay and external disturbance will reduce the dynamic performance of NCSs and even disrupt the stability of the system.Recently,networked predictive control has been achieved an active method to compensate for the network induced phenomenon,which has a wide application prospect because of its simpler and more general way to deal with communication constraints.On the other hand,to deal with the limited communication capacity of NCSs and channel congestion problems,event-triggered scheme is introduced to significantly reduce the transmission times of data information thereby saving network bandwidth resources.It should be noted that how to design a more effective communication strategy to further improve the system performance while reducing the bandwidth resource utilization rate is of great significance and application.Therefore,further researches on event-triggered networked predictive control and disturbance rejection problems are essential to guarantee the performance of NCSs,and enhance the robustness of system while saving the communication bandwidth resources.Based on the above analysis,this thesis is concerned with the event-triggered based active disturbance rejection control for NCSs with networked-induced delay and external disturbance.Combining networked predictive control strategy,active disturbance rejection technique and sliding mode control theory,the effective control mechanism is presented to actively compensate for the time delay and disturbance,and the improved event-triggered control algorithms are designed to reduce the network resource occupation.The specific contents of the paper are summarized as follows:(1)Chapter 2 investigates the networked predictive control problem for NCSs based on event-triggered scheme and active disturbance technique.A novel combination of the disturbance rejection technique,and the networked predictive control strategy for the NCSs with external disturbance and time delay.To be specific,the state and disturbance observers based networked predictive control method are constructed to compensate for the networked-induced delay and then,the active disturbance rejection technique is utilized to improve the robustness of NCSs.On this basis,the event-triggered scheme is embedded in the controller to ensure the stability and the desired closed-loop system performance with limited bandwidth.Finally,the simulation example is exploited to validate the effectiveness of the developed method.(2)Chapter 3 investigates the active disturbance rejection control problem for NCSs based on hybrid-triggered scheme and disturbance observer.Firstly,the state and disturbance observers are constructed and the active disturbance control technique is presented by utilizing the information of the system state and disturbance estimation to improve the disturbance rejection capacity of NCSs.Then,a hybrid triggered control scheme with a random switching between time-triggered and event-triggered is established to guarantee the dynamic balance between the usage of network communication resources and system performance.Furthermore,by utilizing the stochastic analysis method,the sufficient condition is provided to ensure the mean square exponential stability of closed-loop control system and the algorithm of controller is designed,which can further improve systems’control precision by utilizing a more efficient triggered scheme.Finally,the advantage of the proposed result is demonstrated by two simulation examples.(3)Chapter 4 investigates the sliding mode control problem for NCSs based on an improved hybrid-triggered scheme and composite disturbance rejection technology.Combining the advantages of sliding mode control and active disturbance rejection control,the idea of composite control is proposed.Particularly,an improved hybrid-triggered strategy is introduced and the adaptive triggered threshold method is designed to switch between traditional event-triggered and memory event-triggered scheme.To be specific,the sliding mode surface function is designed,and the sufficient condition is provided to guarantee the stability of the system with an H∞ performance.Further,the sliding mode control law is given to ensure the reachability of sliding mode surface.Finally,the feasibility of the theoretical method is verified by a simulation example.