Application Of PID Control In Networked Control System

Networked Control System (NCS) is a synthetic application which combines control science, computer science and network technology. However, when the distributed applications are implemented over the control network, it will result in the information collide and re-transmit because of information transmitted through the limited bandwidth and weight capability. Besides, in networked control system (NCS), undetermined network delays always exit in the data communication. The delay can cause significant deterioration of system performance, even make the system unstable. Therefore, it is of especial importance to analyze and research network delays.This dissertation proposes the Smith predictor aiming at removing delays of the NCS, and then the stability of the system can be ensured. And the controller can also be designed with traditional methods.Firstly, this dissertation introduces the main problems and several methods about time-delay in networked control system.Secondly, the dissertation tells the principle of the Smith predictor including classical and new kind. This part also clarified how to use this method in NCS.Thirdly, as the PID control method is widely used and it is a convenient and rapid method for project application, then the adjustment method of optimum PID parameters is provided. So this part combines this method with Smith predictor and applies it to NCS control. And we can see this method is useful from the simulation. Then, based on fuzzy control tactics, the fuzzy PID control strategy is researched. Since the fuzzy control is also a universal method in the project and it has very good robustness. And this method is also combined with Smith predictor in NCS. Afterwards, the simulation verifies the good result of this method. Besides above, on the basis of organism immune system and fuzzy cogitation, the fuzzy immune PID control strategy is provided. Then fuzzy immune PID method and Smith predictor are used in NCS at the same time. Also we can see the improved performance of the system from the simulation.Concluding remarks are presented and the end of this dissertation. Some open problems are also pointed, which deserve further study.