Performance Analysis And Robust Control For Stochastic Networked Control Systems  Posted on:20100119  Degree:Doctor  Type:Dissertation  Country:China  Candidate:X S Fang  Full Text:PDF  GTID:1118360302966599  Subject:Control theory and control engineering  Abstract/Summary:  PDF Full Text Request  Networked control systems (NCSs) are special distributed control systems in which feedback control loops are closed via communication networks. Comparing with the conventional pointtopoint control systems, NCSs present a number of advantages, such as low cost,reduced system wiring, ease of system diagnosis and maintenance, and increased system agility. The targeted applications are industrial plants, transportation, power gird, and unmanned aerial vehicles (UAVs), etc. However, the introduction of communication networks in feedback control loops complicates the analysis and synthesis of NCSs, because the networkinduced transmission delays, data packet dropouts and fluctuation or limitation of bandwidth will inevitably degrade the control performance of NCSs, or even cause the system to be unstable. Consequently, the research on NCSs is of great theoretical and applicable significance and has appeared to be a topic of significant interest to the control community. In this dissertation, the modeling, analysis, and control of NCSs with uncertain network quality, such as networkinduced delay, packed dropout, and limitation of bandwidth are deeply studied by applying the robust control and stochastic control theory. In terms of the Lyapunov approach and linear matrix inequality (LMI) techniques, stability conditions and design methods of the robust controller are presented for NCSs with uncertain network quality. By introducing kinds of optimal performance index, the inner relationship between performance index and network quality is also established. The main contents are as follows:The observerbased guaranteed cost control problem is first studied for a class of NCSs with random data packet dropouts. Two kinds of packet dropouts (the packet dropout from sensor to controller (S/C) and controller to actuator (C/A)) are both modeled by two mutually independent stochastic variables satisfying the Bernoulli binary distribution. New NCS models are provided considering both single and multiplepacket transmission. A new observer is designed to estimate the states and system input simultaneously by constructing an augmented system in which the original system input is regarded as a new state. Based on this observer, a guaranteed cost controller is designed such that the closedloop system is stochastically exponentially meansquare stable and the cost function value is not more than a specified upper bound. Then the design method of such controller is formulated in terms of the LMI approach and iterative Cone Complementarity Linearization (CCL) algorithm.The observerbased Hâˆžcontrol problem is investigated for a class of discrete NCSs with communication constraints. Assuming that the network has limited capacity and the total bandwidth is random fluctuated satisfying a known probability distribution, the NCS models are provided considering both single and multiplepacket transmission. The sufficient conditions on the stochastic stability of NCSs are obtained in terms of different bandwidth distribution and communication constraints. By introducing the optimal Hâˆžperformance index, the inner relationship between Hâˆžperformance and communication constraints is established. Using the iterative LMI approach and CCL algorithm, the Hâˆžcontroller is designed such that the closedloop system is stochastically meansquare stable and the optimal Hâˆždisturbance attenuation level is also achieved.The statefeedback Hâˆžcontrol problem is investigated for a class of NCSs in the discretetime domain with random but bounded delay. At each sampling time, the current S/C delay is known for controller by, e.g., the timestamping technique. Considering both single and multiplepacket transmission, the closedloop NCSs are modeled as stochastic discretetime jump linear systems with the S/C time delays are modeled as a Markov chain. In order to reduce the conservativeness of the results, the statefeedback controller gains are switched depending on the value of the S/C time delays. The sufficient conditions on the existence of Hâˆžcontroller are obtained. The iterative LMI approach and CCL algorithm are employed to calculate the statefeedback gains.Finally, the Sampleddata Hâˆžcontrol problem for a class of networked control systems (NCSs) with random packet dropouts is investigated. The NCS is modeled as a sampleddata system which involves a continuous plant, digital controller, eventdriven holder, and network channels. In this model, two types of packet dropouts in the S/C and C/A sides are both considered, which are described by two mutually independent stochastic variables satisfying Bernoulli binary distribution. By applying an input delay approach, the sampleddata NCS is transformed into a continuous timedelay system with stochastic parameters. An observerbased control scheme is designed such that the closedloop NCS is stochastically exponentially meansquare stable and the prescribed Hâˆždisturbance attenuation level is also achieved. The controller design problem is transformed to a feasibility problem for a set of LMIs.
 Keywords/Search Tags:  Networked control systems, stochastic systems, guaranteed cost control, H_∞control, networked time delay, packet dropout, communication constraints, linear matrix inequality  PDF Full Text Request  Related items 
 
