Resiliency of control systems means characteristics that a system operates well under malicious attacks on instrumentation. In this thesis, we propose Unknown Input Observer (UIO) based resilient control system design method for the case of simultaneous attacks on sensors and actuators. We use an observer based Resilient State Estimation (RSE) method for protecting from sensor attack. Limitation of existing RSE method is that state estimation error is affected by disturbance and actuator attack. In order to supplement the drawback, we propose the UIO based RSE method. Proposed method provides superior state estimation performance regardless of the effect of disturbance and actuator attack. In addition, we suggest an algorithm that would be able to diagnose which sensors are attacked or broken. In order to protect the system from actuator attack, we propose a method that would be able to estimate and reject the effect of actuator attack. Proposed method exploits UIO based RSE method. The proposed method provides a level of resiliency to the control system when disturbance and attack are slow varying. Simulation and experiment are implemented on the magnetic levitation system platform so as to validate the effectiveness of proposed method. In addition, we compare the performance between existing method and proposed method. ⓒ 2017 DGIST
Table Of Contents
1 Introduction 1 -- 1.1 Significance of Resilient Control Systems 2 -- 1.2 Motivation 2 -- 1.3 Thesis Outline 4 -- 2 Unknown Input Observer Based Resilient Control System Design 5 -- 2.1 Problem Formulation 6 -- 2.2 Unknown Input Observer Based Resilient State Estimation Method 11 -- 2.2.1 Limitation of the Existing Resilient State Estimation Method 11 -- 2.2.2 Unknown Input Observer Based Resilient State Estimation Method Design 16 -- 2.2.2.1 Unknown Input Observer Design 17 -- 2.2.2.2 Median Operator 22 -- 2.2.3 Analysis of State Estimation Error of Proposed RSE Method 23 -- 2.2.4 Diagnosis Method of the System under Sensor Attack and Fault 37 -- 2.3 Defense Approach Against Actuator Attack 40 -- 3 Validation with Magnetic Levitation Platform 43 -- 3.1 Modeling 44 -- 3.2 Design of Resilient Control System Design 46 -- 3.2.1 Existing Resilient State Estimation Method Using Median Operation 46 -- 3.2.2 Proposed Resilient Control System Design 47 -- 3.3 Scenarios 50 -- 3.3.1 Scenario 1 50 -- 3.3.2 Scenario 2 51 -- 3.3.3 Scenario 3 51 -- 3.4 Simulation Results 51 -- 3.4.1 Simulation Results of Scenario 1 51 -- 3.4.2 Simulation Results of Scenario 2 58 -- 3.4.3 Simulation Results of Scenario 3 62 -- 3.5 Experiment Results 67 -- 3.5.1 Experiment Results of Scenario 1 67 -- 3.5.2 Experiment Results of Scenario 2 71 -- 3.5.3 Experiment Results of Scenario 3 78 -- 4 Conclusion 83 -- A MATLAB Code For Numerical Simulation 85 -- Bibliography 97 -- 국문초록 99
Research Interests
Resilient control systems; Control systems with nonlinear sensors and actuators; Quasi-linear control systems; Intelligent transportation systems; Networked control systems