Showing papers by "Ron J. Patton published in 2010"

Issues of Fault Diagnosis for Dynamic Systems

Abstract: There is an increasing demand for dynamic systems to become safer, more reliable and more economical in operation. This requirement extends beyond the normally accepted safety-critical systems e.g., nuclear reactors, aircraft and many chemical processes, to systems such as autonomous vehicles and some process control systems where the system availability is vital. The field of fault diagnosis for dynamic systems (including fault detection and isolation) has become an important topic of research. Many applications of qualitative and quantitative modelling, statistical processing and neural networks are now being planned and developed in complex engineering systems. Issues of Fault Diagnosis for Dynamic Systems has been prepared by experts in fault detection and isolation (FDI) and fault diagnosis with wide ranging experience.Subjects featured include: - Real plant application studies; - Non-linear observer methods; - Robust approaches to FDI; - The use of parity equations; - Statistical process monitoring; - Qualitative modelling for diagnosis; - Parameter estimation approaches to FDI; - Fault diagnosis for descriptor systems; - FDI in inertial navigation; - Stuctured approaches to FDI; - Change detection methods; - Bio-medical studies. Researchers and industrial experts will appreciate the combination of practical issues and mathematical theory with many examples. Control engineers will profit from the application studies.

Friction compensation as a fault-tolerant control problem

Abstract: The control of systems that involve friction presents interesting challenges. Recent research has focused on detailed modelling of friction phenomena in order to use robust on-line friction compensation procedures, attempting to cancel out the friction force effect in the feedback control of a mechanical or mechatronic system. However, the friction modelling problem remains a very difficult challenge and this article proposes a new approach to friction compensation which is based on the theory of robust fault estimation. The friction forces acting in a dynamic system can be viewed as actuator faults with time-varying characteristics to be estimated and compensated within an output feedback fault-tolerant control (FTC) scheme, so that the limitations arising from the use of a friction model are obviated. The friction (fault) estimation problem is hence embedded inside a control system with required stability, and performance robustness. This can be a significant advantage over well-known model-based friction compensation methods in which detailed modelling of friction phenomena is essential and for which robustness with respect to friction characteristics is difficult to achieve using non-linear models.

Fault Detection and Diagnosis for Aeronautic and Aerospace Missions

Abstract: The term Fault Detection and Diagnosis (FDD) is a development of the term Fault Detection and Isolation (FDI). Generally speaking, FDD goes slightly further than FDI by including the possibility of estimating the effect of the fault and/or diagnosing the effect or severity of the fault. Hence, the term FDD also covers the capability of isolating or locating a fault. Both of these topics have received considerable attention worldwide and have been theoretically and experimentally investigated with different types of approaches, as can be seen from the general survey works [1, 2, 3, 4, 5, 6, 7].

LPV fault estimation and FTC of a two-link manipulator

Abstract: This work is motivated by the challenge to develop an adaptive strategy for systems that are complex, have actuator faults and are difficult to control using linear methods. The novelty lies in combined use of LPV fault estimation and LPV fault compensation to meet active FTC performance requirements. The paper proposes a new design approach for systems which can be characterized via sets of LMIs and can be obtained using efficient interior-point algorithms. A polytopic LPV estimator is synthesized for generating actuator fault estimates used in an FTC scheme to schedule the nominal system state feedback gain, thereby maintaining the system performance over a wide operating range within a proposed polytopic model. The active FTC controller is a function of fault effect factors derived on-line. The effectiveness of the proposed method is demonstrated through a nonlinear two-link manipulator system with torque input faults at each joint.

An LPV pole-placement approach to friction compensation as an FTC problem

Abstract: The concept of combining robust fault estimation within a controller system to achieve active Fault Tolerant Control (FTC) has been the subject of considerable interest in the recent literature. The current study is motivated by the need to develop model-based FTC schemes for systems that have no unique equilbria and are therefore difficult to linearise. Linear Parameter Varying (LPV) strategies are well suited to model-based control and fault estimation for such systems. This contribution involves pole-placement within suitable LMI regions, guaranteeing both stability and performance of a multi-fault LPV estimator employed within an FTC structure. The proposed design strategy is illustrated using a non-linear two-link manipulator system with friction forces acting simultaneously at each joint. The friction forces, considered as a special case of actuator faults, are estimated and their effect compensated within a polytope controller system, yielding a robust form of active FTC that is easy to apply to real robot systems.

LPV approach to friction estimation as a fault diagnosis problem

Abstract: The control of systems that involve friction presents interesting challenges. Recent research has focused on detailed modelling of friction phenomena as a very complex and difficult modelling challenge. However, the friction effects acting in a dynamic system can be viewed as actuator faults with time-varying characteristics to be estimated and compensated within a Fault Detection and Diagnosis (FDD) scheme, so that the limitations arising from the use of a friction model are obviated. This work is motivated by the utilisation of robust Linear Parameter Varying (LPV) estimation approach providing effective and robust fault estimation. The approach is illustrated using a two-link manipulator system with Stribeck friction. Results show that the time-varying friction forces on each joint can be simultaneously and robustly estimated through the online measurement of the varying parameters.

Fault tolerant plug and play vibration control in building structures

Abstract: The number and severity of earthquakes has led to a growing interest in control systems capable of improving the safety and integrity of buildings and other structures that are subject to violent vibration control on each building floor is considered as a local control problem within the hierarchical two-level structure. The distributed control system, based on receding horizon control, gives rise to a “plug and play” structure. If individual controller subsystems fail the global can be maintained. An example of a building structure excited by standard seismic data with semi-active hydraulic floor actuators is described. Results demonstrate the fault tolerance of the plug and play distributed system as the coordinator compensates for actuator malfunctions. The distributed system performance is compared with a single level H-∞ controller as a robust system benchmark.

Integral hierarchical SMC of uncertain interconnected systems

Abstract: An Integral Sliding Mode approach to hierarchical control of interconnected systems with uncertainties arising from unknown interconnection states and unknown parametric variation is proposed. The work is based on a recent study using constrained LQR showing that a two-level hierarchical control system with global coordination control provides a suitable architecture for control of uncertain interconnected systems, in which the control coordinator seeks to balance the effects of the interaction uncertainties. The new method is viewed as an extension to the constrained LQR approach and a nonlinear tutorial example problem is used to illustrate the comparison.

Robust LPV Estimator Approach to Friction Diagnosis

Abstract: The control of systems that involve friction presents interesting challenges. Recent research has focused on detailed modelling of friction phenomena as a very complex and difficult modelling challenge. However, the friction effects acting in a dynamic system can be viewed as actuator faults with time-varying characteristics to be estimated and compensated within a Fault Detection and Diagnosis (FDD) scheme, so that the limitations arising from the use a friction model are obviated. This work is motivated by the utilisation of robust Linear Parameter Varying (LPV) estimation approach providing effective and robust fault estimation. The approach is illustrated using a two-link manipulator system with Stribeck friction. Results show that the time-varying friction forces on each joint can be simultaneously and robustly estimated through the online measurement of the varying parameters.