Vasfi Eldem

Fault detection and diagnosis in propulsion systems - A fault parameter estimation approach

The paper presents the development of a fault detection and diagnosis (FDD) system with applications to the Space Shuttle main engine. The FDD utilizes a model-based method with real-time identification and hypothesis testing for actuation, sensor, and performance degradation faults.

The solution of diagonal decoupling problem by dynamic output feedback and constant precompensator: the general case

In this paper, the solution to diagonal decoupling problem via dynamic output feedback and constant precompensator is presented in the general case. The literature contains a number of particular solutions for this problem. These solutions are valid, for instance, for square transfer matrices or they employ restricted dynamic output feedback schemes. Here, we start with a nonsquare transfer matrix and consider a dynamic output feedback scheme where there is a proper compensator in the feedback loop accompanied by a constant gain (precompensator) in the feedforward path. In this respect, the problem being considered is the dynamic output feedback version of the well-known Morgans problem. The approach taken involves the characterization of open-loop diagonalizers which admit a dynamic output feedback realization. The key concepts involved in the solution are the generalized version of diagonal causality degree dominance and the set of attainable infinite zero orders. An example is also included to illustrate the main result. >

Parameter and structure identification of linear multivariable systems

Abstract In this paper, a parameter and structure identification scheme, which can be used for both continuous and discrete time systems, is presented. This scheme has an “on-line” nature and it incorporates standard techniques such as state variable filters and adaptation laws developed through stability analysis. The canonical form being used is based on the output injection which is constructed to assign all the poles of the system to α, an arbitrary chosen real number. It is therefore named the “α-canonical form”.

Parametrization of multivariable systems using output injections: alpha canonical forms

Abstract In this paper the parametrization of multi-output systems is considered. The method developed is based on the notion of output injections. A similar method has also been used in connection with the identification of a special class of systems. There, the resulting canonical form is called the α-canonical form. Here, using the same terminology, we address the following issues on the α-canonical form. First, we show that the α-canonical forms can be used to parametrize a more general class of systems, namely all minimal (reachable and observable) systems. This is achieved by the use of isomorphisms of the output space. Then, it is proven that the output injections used in constructing the α-canonical forms need to have a special structure in order to guarantee the uniqueness of the parametrization. This result also reveals the key role played by dead-beat observers in constructing the α-canonical forms. Finally, the connections between the α-canonical forms and input-output relations are investigated.

On the general solution of the state deadbeat control problem

In this note, the state deadbeat control problem is considered. It is shown that, after appropriate change of basis of input and state spaces, the general solution of the state deadbeat control problem can be expressed completely by the rows of the powers of system matrix. This result yields a very simple procedure for the calculation of a state feedback deadbeat control gain. It also provides the number of free parameters which could be used for further design purposes. The results are illustrated by an example at the end of the note. >

On the Problem of Decoupling

Abstract The row-by-row decoupling of linear multivariable systems with stability is considered. An implicit necessary and sufficient condition for this problem to have a solution is provided. The approach used here takes advantage of the properties of the ring of proper and stable rational functions.

A Simplified Dynamic Model of the Space Shuttle Main Engine

This paper presents a simplified model of the space shuttle main engine (SSME) dynamics valid within the range of operation of the engine. This model is obtained by linking the linearized point models obtained at twenty five differenc operating points of the SSME. The simplified model was developed for use with a model-based diagnostic scheme for failure detection and diagnostics studies, as well as control design purposes.

Stabilizing and deadbeat properties of receding-horizon controllers

ABSTRACT It is shown that receding-horizon controllers with horizon length N ≥ v (v being the controllability index of the system) stabilize a given discrete-time linear multi-variable system. Necessary and sufficient conditions for a receding-horizon controller to be a deadbeat controller are also given. It is further shown that by modifying a receding-horizon controller m of the poles of the closed-loop system (where m is the dimension of the input space) can be assigned to zero with simultaneous stabilization. The deadbeat properties of such modified receding-horizon controllers are also investigated,

Partial Disturbance Rejection with Internal Stability and

Complete disturbance rejection problems are equivalent to zeroing (cancelling) all the Markov parameters of the closed loop system between the disturbance and the controlled output. When this is not possible, one might consider partial disturbance rejection which can be defined as zeroing the first, say

H_\infty

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