Showing papers by "Ron J. Patton published in 1991"

Robust fault detection using eigenstructure assignment: a tutorial consideration and some new results

Abstract: Developments in the eigenstructure assignment approach to robust fault detection are discussed. By suitable assignment of the eigenstructure of an observer, the residual signal is decoupled from disturbances. The main contribution of this work is the novel use of right eigenvector assignment of observers, which gives more freedom for achieving disturbance decoupling. It is shown that, when decoupling conditions are satisfied, the resulting deadbeat design is equivalent to the first-order parity space structure for residual generation. Two tutorial examples are presented to illustrate the disturbance decoupling property and the conditions under which left or right eigenvectors are assignable. >

Fault detection and diagnosis in aerospace systems using analytical redundancy

Abstract: Performance requirements in aeronautics and the rapid growth of electronics, especially of digital computers, have gradually led to the combination of advanced control theories and fly-by-wire technology. This has resulted in designs for which the control systems are flight critical. The required reliability is usually achieved by a multiplication of sensors, computers and actuators accompanied by a voting system. The on-board computer provides the possibility of replacing the sensor hardware replication, which is very expensive, with a management of the functional or analytical redundancy constituted by the knowledge of the system. Different techniques have been proposed; the aim of this article is to outline an review the state of the art and describe some of the studies of analytical methods of fault diagnosis procedures, based on fault monitoring in aircraft and spacecraft sensor systems.

A robust parity space approach to fault diagnosis based on optimal eigenstructure assignment

Abstract: By assigning the left eigenvectors of the observer orthogonal to the disturbance directions, robust fault detection is achievable. Eigenstructure assignment together with a dead-beat design yields the same structure as the 1st order parity relation, when applied to the observer's estimation error dynamics. The fault diagnosis scheme can be implemented in the parity space format. The dead-beat structure also gives a robust and time-optimal monitor performance which is capable of discriminating between the separate effects of plant uncertainties and faults. The directional properties of the residual are used to isolate faults in either sensors or actuators. The paper also shows that the observer-based fault detection approach is equivalent to the generalized parity space approach in a particular case. The proposed method is applied to a tutorial example. Simulation results demonstrate the robustness of the method. >

Robust fault detection of jet engine sensor systems using eigenstructure assignment

Abstract: This paper examines a robust fault detection scheme that can be used to detect faulty sensors of jet engines. The fault detection scheme has to be insensitive to disturbances while being highly sensitive to sensor faults (robust). The paper presents a complete description of a robust fault detection approach based on eigenstructure assignment, both in continuousand discrete-time domains. By assigning the left (or right) eigenvectors of the observer orthogonal (or parallel) to the disturbance directions, the robust (disturbance decoupling) fault detection is achieved. The approach has been applied to a realistic jet engine simulation system. The system is a 17th-order system, and a reduced-order model is used to approximate the system. Modeling errors are considered as disturbances acting on the fault detection scheme. A particularly novel feature of the work is the development and use of a new method (new in this context) for estimating disturbance direction. The robust fault detection scheme design uses this estimated direction as that of the direction of unknown inputs (disturbances). Simulation results show that the scheme can detect soft or incipient faults efficiently.

Design of a low-sensitivity, minimum norm and structurally constrained control law using eigenstructure assignment

Abstract: The freedom for eigenvalue assignment in specified areas of the complex plane and of the scope for placing the corresponding eigenvectors is utilized to form an analytical gradient-based optimization problem which may be used to determine a low-sensitivity eigenvalue assignment with a structurally constrained and low-norm linear gain matrix. Examples are used to compare the properties of such optimized controllers with those obtained using single-objective design techniques.

A robust disturbance decoupling approach to fault detection in process systems

Abstract: The authors describe a robust scheme for use in the role of fault detection in sensors and actuators of process systems. The fault detection scheme is designed to be insensitive to disturbances, while being sensitive to faults. The authors present the robust fault detection approach based on eigenstructure assignment in the discrete-time domain. By assigning the left eigenvectors of the observer orthogonal to the disturbance, robust (disturbance decoupling) fault detection is achievable. The approach has been applied to an 11th-order nuclear reactor system. A reduced-order model is used to approximate this system and modeling errors are considered as disturbances acting on the reduced-order model contained in the observer. The work involves the development and use of a method for estimating the disturbance direction. The robust fault detection scheme design uses this direction as that of the direction of unknown input acting on a fourth-order model. Simulation results show that the scheme can detect soft or incipient faults efficiently. >

Insensitivity properties of multirate feedback control systems

Abstract: The design capabilities of a class of periodic systems, multirate systems with multiple input and fixed output (MIFO) rates, for application to the eigenstructure assignment robust design technique, are examined. A special feature of the MIFO multirate systems is the ability to introduce extra design freedom in the eigenproblem by a suitable choice of sample rates. The criteria for the selection of minimum sample rates to produce this extra design freedom and the implication of this choice for the eigenstructure procedure are outlined. The use of the extra freedom to produce perfectly decoupled closed-loop modal responses is examined. The improved insensitivity properties of these solutions are demonstrated with an example which compares the performance of multirate and corresponding single rate designs. >