Research On Networked Predictive Control And Event-triggered Control Based On Switching

The last two decades have witnessed the quick progress of networked control systems (NC-Ss), where network predictive control (NPC) scheme and event-triggered control (ETC) scheme are two hot research issues. NPC scheme is used to compensate the effect of unreliable network, while ETC scheme is used to reduce the transmission load without a performance penalty. How-ever, there exist a lot of problems needed to be solved. Based on switched system technology, this thesis will start to study these issues. The main content of this thesis is listed as follows:1. For a discrete-time linear-time-invariant NCSs with time-varying delays and packet drop-outs, the stability analysis and the NPC design are studied. Delays and packet dropouts in sensors-to-controllers channels and controllers-to-actuators channels are described under the switched system technology. An NPC scheme is designed based on active packet loss method. The problem on large computing, caused by the augmented matrix in stability analysis is solved by using small gain theorem. The asymptotical stability (input-to-state stability) for the closed-loop system can be guaranteed without (with) consideration of external disturbances. An exper-imental example on a DC-motor based speed control rig is demonstrated the effectiveness of the proposed method.2. The problem for the stability analysis of NCSs with norm-bounded uncertainties is stud-ied. Similarly, the nominal system will be used to construct the networked predictive controller. The closed-loop NCS with uncertainties under the networked predictive controller is described as a coupled switched control system. Then based on the switched system method, sufficient conditions are provided to guarantee the robust stability of the system. As an application, the proposed NPC scheme is applied to a practical DC-motor control rig.3. Problems for the NPC scheme with unstable observation existing in feedback channels and the NPC scheme with time-varying delays existing in forward channels are considered. For the former, the observer error system has been rewritten as a switched system consisting of stable observations and unstable ones. Under the well known average dwell time scheme in switched systems, sufficient conditions are given to ensure the observer error system asymptotically stable. For the latter, time-varying network-induced delays in forward channels are seen as the switched law and embed into the closed-loop system. Estimated states of networked predictive controller have difference with estimated states of the observer. A switched system with its states consisting of plant states, observer errors and predictor-observer errors is established. Based on the common Lyapunov function in switched systems, sufficient conditions are given to ensure the stability of the closed-loop system. Both theory and numerical simulations show the proposed method much less conservative than exiting ones.4. The integrated design on event-triggered control and NPC scheme are considered. In order to synchronize states of controllers, sensors and actuators, all these elements will be re-designed. Based on switched system technology, the closed-loop system with the consideration of network-induced delays is rewritten into an easy analysis form. By using the switched Lya-punov function, sufficient conditions for ensuring the stability of the closed-loop system are proposed. Both numerical simulations and practical experiments show the effectiveness of the proposed method.5. The problem for the stability analysis of NCSs under ETC scheme with respect to packet dropout is studied by using the switched system method. A special Lyapunov based ETC design with the consideration of packet dropouts is considered. The closed-loop system with the ETC and the packet dropouts can be re-written as a switched system, switching between the normal transmission and the communication dropout. By adopting the well-known concept:average dwell-time in switched systems, sufficient conditions in terms of transmission intervals that can ensure the stability of the closed-loop system in the presence of the transmission dropouts are provided. Experimental results using DC-motor based speed control are demonstrated the effec-tiveness of the proposed method.