Research Of Adaptive Fault Tolerant Control Method On Networked Control System

Along with the rapid development of modern science and technology,the merging of computer technology,information technology,control technology and network communication technology,networked-based control technologies have been widely applied in industrial control applications.Generally speaking,two kinds of problems are still open to be solved in the network-based control systems.Problems of the first category are induced by the network itself such as time-delay,data loss and congestion,et.al.Problems of the second category are caused by the communication fading,actuator failure and other malfunctions related to the software/hardware involved in the networked control systems.With the reliability and security consideration of networked control systems,we are dedicated to develop adaptive fault tolerant control techniques for performance enhancement of the networked control systems in the presence of failures,in which the adaptive control schemes and the fault-tolerant control schemes were skillfully combined and utilized.Main contributions of this dissertation are listed as follows.(1)Networked control system model capturing actuator failure and communication fading is built on the basis of characterization analysis of time-delay.A time stamp based scheme for measuring the network-induced time-delay is proposed,in which the singular values among the measurement set were screened out a priori.Furthermore,to implement the adaptive fault tolerant control in the presence of random measured value of time-delay,a discrete-time quadratic index based time-delay estimation method is developed with the aid of stochastic estimation theory.(2)For master-slave networked control systems in the presence of communication fading and actuator failures in general types such as loss of effectiveness,outage,offset and stuck,a failure and controller parameter estimation based distributed adaptive fault tolerant control strategy is proposed for fault-tolerant asymptotic synchronization of the master-slave control system.In order to estimate the controller gain,the effectiveness loss factor and fading factor online,a group of adaptive laws are designed.Those estimated parameters make it feasible to design adaptive fault-tolerant controller for attenuating the external disturbance as well as driving the states of all sub-systems synchronously stable.Also,the synchronously stability of the closed system could be validated by using the Lyapunov stability theory.(3)A direct adaptive fault tolerant control scheme without system paremeters and fault estimation is proposed for network control systems.The effects caused by faults can be compensated by virtue of controller parameter online update,moreover,master-slave type global exponential asymptotical synchronization of the corresponding networked control system can also be guaranteed.Based on the Lyapunov stability theory,the asymptotic stability of the master-slave control system implementing the adaptive fault tolerant controller is validated.(4)The performance optimization problems in the framework of adaptive fault-tolerant control scheme are discussed.In order to optimize the prescribed performance index,the LMI techniques are utilized in the adaptive control gain design.Aiming at the networked control system with software and hardware faults and disturbance,a controller design method of output feedback adaptive robust fault tolerant is proposed.The closed system will be stable and possess sub-optimal fault tolerance H? performance to some extent.(5)To emulate the adaptive fault-tolerant synchronization scheme and the delay measurement scheme,the multi-axis servo control systems control system and the multi stirrers control system are constructed on the platform of the Rockwell Automation Networks and the Siemens Profinet,respectively.The practical operating results from the two experimental systems reveal the effectiveness of the proposed schemes from the engineering aspect.