Transcript Document
Fault-tolerant Control System Design and Analysis Jin Jiang Department of Electrical and Computer Engineering The University of Western Ontario London, Ontario N6A 5B9 Canada 7/17/2015 1 Outline of the presentation Overview of two approaches to fault-tolerant control system design and analysis Redundancy in fault-tolerant control systems Trade-offs among redundancy, performance and integrity An example of passive fault-tolerant control design An example of active fault-tolerant control design Some open problems 2 Fault-tolerant control: An overview Passive fault-tolerant control systems Active fault-tolerant control systems Robust fixed structure controller Faults have been considered at the controller design stage Explicit fault detection/diagnosis schemes Real-time decision-making and controller reconfiguration The key to any fault-tolerant control system Redundancy 3 Passive fault-tolerant control systems faults - Controller L Actuator System Outputs Sensor faults 4 Active fault-tolerant control systems 5 Features and limitations Passive fault-tolerant control systems Simple to implement Difficult to account for large number of fault scenarios Unable to deal with unforeseen faults Active fault-tolerant control systems Potentially be able to deal with a large number of fault scenarios Can deal with certain number of unforeseen faults More complex to implement Real challenge is real-time decision-making 6 Redundancies Actuator redundancies • Sensor redundancies • Multiple physical actuators They usually act on the system at different locations Multiple physical sensors They usually measure the same physical quality Analytical redundancies Rely on mathematical models (FDI) 7 Actuator redundancies 8 Actuator Redundancies 9 Definitions of actuator redundancies 10 Sensor redundancies u2 A2 A3 System Dynamics y2 .......... u3 um 1 S 21 z21 S22 z22 S 2q z2q S p1 zp 1 S p2 zp2 2 Am z1q S 1q1 yp Spq p 2 Sensor Outputs A1 z12 .... u1 S12 .... y1 .... System Outputs .... System Inputs z11 .... .... Actuator Inputs S 11 zpqp 11 System Outputs .... .... Inputs Analytical Redundancies Sensors Redundant system output Intermediate system variables Analytical model 12 Performance trade-offs Three main factors to consider in any fault-tolerant control system design: System Integrity (safety requirements) Performance (design specifications) Redundancy (physical and financial constraints) Problem: How to design a control system, under a given degree of redundancy such that the integrity of the system is guaranteed and the performance is satisfactory. Issue 1: System integrity should always be maintained Issue 2: Faults should result in reduction of the degree of redundancy first Issue 3: One should consider performance degradation with available redundancies. 13 Example of passive fault-tolerant control system 14 Description of system 15 Control system performance 16 Control system performance 17 Example of active fault-tolerant control system 18 Simulation results 19 Simulation results 20 Simulation results 21 Simulation results 22 Some open problems Reliability analysis of fault-tolerant control systems Stability analysis of fault-tolerant control systems Graceful performance degradation Integration of passive and active approaches Industrial applications of fault-tolerant control system technologies 23 Thank You ! 24