Study On Time-delay Analysis And Composite Compensation Strategy Of Networked Control System

Networked control system(NCS) is a real-time closed-loop feedback control system which actuator, sensor and controller constitute through the network. All transmission and exchange of information between components is carried out through the network. It is a complex distributed control system which can realize network resource sharing and integrate the complex control system of horizontal or vertical direction, and is convenient to extend and maintain.Although the networked control system has many advantages compared with the traditional control system, however, the introduction of the network in control system has brought a series of special problems to be researched and solved. The network induced delay is one of the main problems, whose presence can reduce the control performance of system, and even cause the instability of system, also makes the system analysis and design complicated at the same time. Therefore, it is particularly important to conduct the thorough research to the problem of time delay in networked control systems, and explore effective strategies to compensate the time delay. The influence of time delay in networked control system is analyzed and effective composite compensation strategy has been proposed in this thesis.First of all, the selected topic background and research significance of this project is introduced,the main research idea of the experts and scholars home and abroad in recent years are compiled, the current research status of system time delay compensation is introduced, and the main research work in this thesis is summarized.Secondly, the structure of the networked control system and the main problems existing in the research are introduced, the influence of time delay to networked control system performance is studied from three different angles. Simulation and the result analysis shows that with the certain sampling period, the greater the percentage of time-delay use cycle is, the greater the effect on the control system is, and τca takes the dominant place.Further more, the basic principle of the traditional Smith estimates controller to compensate the delay which is analyzed in this thesis, aimed at the shortcomings of its application in the networked control system, improved the structure of the Smith prediction controller, the network induced delay and pure lag controlled object can be compensated at the same time without identification the system time delay online.At last, aiming at the shortcoming that excessively depends on the precise mathematical model of the Smith prediction controller, design two kinds of compound controller to effective compensate the time delay, the compound controller is Smith estimates controller combined with fuzzy adaptive PID controller and single neuron Proportional Summation Differential(PSD) controller with the capable of self-study and parameter setting respectively. Based on TrueTime toolbox the networked control system simulation model is set up and the simulation is carry on. Simulation and the result analysis show that in both cases that the estimates model and the controlled object model match exactly or not, the two kinds of compound controller designed in this thesis can achieve good dynamic and static performance, and the effective compensation for delay.