Output Tracking Control Of Networked Cascade System:A Switched Cascade System Approach

The development of computer,microelectronics and network communication technology has promoted a series of changes in the unit parts,the system structure and the control technical methods,which makes the system towards the direction of network development.Networked control systems,exchange the information.between actuators,controllers,estimators and sensors by sharing communication networks,have a lot of advantages such as reducing system wiring,easy extension and maintenance,sharing information resource and increasing the reliability and flexibility of the systems.Networked control systems have been formed the distributed open web systems which are combining of control and information.It conforms to the trend of the integration of computer,network and control technology,and it is the inevitable development of logic.On the other hand,cascade control systems have a very prominent role to handle large time delays and dramatic varying disturbances,and the systems through the two closed-loop coordination to achieve the effect of control.Meanwhile,cascade control systems have a strong ability to overcome disturbance which entering the inner loop,reduce the time parameter of controlled object,and improve the response speed of the system.This thesis studies the stabilization,H? control and output tracking control problems of networked cascade control systems with network induced delays and packet losses based on switched cascade control systems approach.It contains the following works:Firstly,for a class of networked cascade control system with short time-varying delays,the system is modeled as a class of switched cascade control system by using the distribution characteristics of network-induced delays,thus avoiding the exponential time-varying items problem.By using the average dwell time method and the switched system theory,a co-design method of the inner-loop and the outer-loop controllers to achieve exponentially stabilization and weighted H? performance is given.Simulation result is applied to illustrate the feasibility and the efficiency of the proposed method.Secondly,in the real network,delays may be longer than one sampling period,therefore weighted and non-weighted H? output tracking control performance of networked cascade control system with short delays and large delays is studied in this section.A sufficient condition on the existence of H? output tracking switching controller of networked cascade control system with short network-induced delays is derived by using the average dwell time approach.Furthermore,such a condition with respect to large network-induced delays is further extended.In view of advantages of the cascade control architecture,a co-design method of the inner-loop and the outer-loop controllers combining with the switching rules to achieve the H?output tracking performance and simultaneously' attenuate the exogenous disturbance is presented as well.Two examples are shown to illustrate the feasibility and the effectiveness of the switched cascade system approach.Finally,a switched cascade system is modeling based on the networked cascade control system with time-delays and packet dropouts,which can depict the new characteristics by the presence of networked-induced delays and packet losses.Introducing integral control into the outer controller,a sufficient condition on the constant tracking control of networked cascade control system with a non-zero disturbance to achieve zero steady-state error is derived by the mode-dependent average dwell time approach.An example of turboshaft engine is presented to show the feasibility and the effectiveness of the constant output tracking designs.