Research On Sensor Fault Diagnosis And Fault-tolerant Control Of Cascade System

Where high-quality control is required,cascade systems are frequently used to satisfy process requirements.At the same time,system faults are inevitable,and feedback control will make faults propagate in the system and alter stability.In this paper,the level control system of the double-capacity water tank is taken as the research object,and fault diagnosis and fault-tolerant control are studied based on a data-driven method for the sensors’ fault of the double feedback loop.The main work is as follows:(1)Summarized the background and research significance of the subject,analyzed the working principle of the double tank combined with the knowledge of the cascade system,and established the static mathematical model of the double tank.(2)Built a cascade control system based on PID control law on the experimental platform.In Matlab/Simulink,OPC communication technology is a bridge of data transmission between the upper and the lower computer to construct the system semi-physical model.Set the normal and fault operation states in the Simulink model and access the sensors’ output signal as the research data.(3)Proposed a fault diagnosis method based on data-driven.Fault detection is realized by the threshold obtained from the data window which is adjacent sampling points;locate the fault according to the sequence of two sensors data exceeding the threshold;fault estimation is realized by quantization of before and after the difference of data series;the eigenvalues are extracted by the data fitting method,and the fault separation is realized by combining discriminant analysis.The above methods established the static models of fault detection,location,estimation,and separation of primary and secondary sensors.Provided the calibration and diagnosis process of the dynamic diagnosis model.Through experiments,verified the effectiveness and accuracy of the fault diagnosis method.(4)Active fault-tolerant control is adopted based on the fault diagnosis method.In the feedback loops of the semi-physical model,the S-function module is used to embed the online fault-tolerant control algorithm.The whole feedback loops involve fault injection,fault self-diagnosis,and fault-tolerant control.Online examples verified the effect of real-time fault-tolerant control.