Fault Diagnosis And Fault-tolerant Control Of Nonlinear And Time-varying Networked Control Systems

The 21 st century is an information age with the Internet as the core.The rapid development of computer technology,network technology,intelligent terminal equipment,and mobile communication technology changes people's daily life and industrial production methods.At the same time,with the continuous improvement of automation in modern manufacturing industries,industrial control systems have become more and more complex,and the uninterrupted production activities have made people more demanding on the operational safety and stability of the systems.It is very urgent to diagnose the fault in time and make the system still meet the production requirements after the fault occurs.The research of fault detection(FD)and fault-tolerant control technology(FTC)has attracted the attention of engineers and technicians and has practical significance.As the networked control system(NCS)controller and the controlled object located in different geographical locations,the control signal from the controller to the actuator and the output signal from the sensor to the controller need to be transmitted through the network in real time,transmission delay will inevitably result.This kind of delay,which may make the fault diagnosis and fault-tolerant control fail,exists extensively in the networked control system and has a great influence on the system operation.In this thesis,based on the Ethernet signal transmission control system as the background.Considering the transmission delay of signal subject to exponential distribution and uniform distribution,respectively,the original system is transformed to obtain the equivalent system,which does not contain delay terms.Thus the complexity of control algorithm is simplified and the purpose of control is achieved.The specific research contents are as follows:(1)It is assumed that the transmission delay obeys the exponential distribution or uniform distribution.However,the delay of communication transmission in the actual network is uncertain,not necessarily strictly obey a certain mathematical distribution.In this regard,the first part of this chapter on the third chapter of the control strategy and algorithm using Simulink actual communication simulation experiments to verify the effectiveness of the algorithm and strategy.Aiming at fault diagnosis and fault tolerant control of nonlinear networked control system with random delay in signal transmission process,Laplace transform is applied to random delay block to obtain the equivalent control system without delay.Then the fault diagnosis observer is used to estimate the state and fault of the equivalent system.Based on the obtained information,a fault-tolerant controller based on PI tracking and adaptive compensation is designed.Observer gain and fault-tolerant control law are obtained by solving linear matrix inequality and the equivalent system and the original system output could track the desired output.The corresponding computer simulation results verify the effectiveness of the method.(2)In this part,the Laplace transformation is used for the networked control system with time-varying parameters to get the relevant equivalent system.Then the optimal fault-tolerant control law is designed under the assumption of fault occurrence and amplitude,and the relevant parameters are solved by Hamilton function and normal equation so that the equivalent system and the original system can still achieve fault tolerance.Finally,the feasibility of the fault tolerant control algorithm is verified by MATLAB simulation.(3)The speed control experiment of the permanent magnet brushless DC motor based on the NetConARM-9 networked control system is carried out.The NetConARM-9 system is mainly composed of NetController,NetConLink and NetConTop,which can be used to rapidly develop and construct control systems and realize monitoring configuration,real-time monitoring and management functions.After Laplace equivalent transformation,an equivalent system is obtained and the Simulink model is constructed.Under the actual working environment of Ethernet,the experiment of speed control of permanent magnet brushless DC motor is carried out to achieve the expected result.