Observers which approximately reconstruct missing state-variable information necessary for control are presented in an introductory manner. The special topics of the identity observer, a reduced-order observer, linear functional observers, stability properties, and dual observers are discussed.

An introduction to observers

In order to estimate the state of a linear time-invariant multivariable system by using a Luenberger observer, it is generally assumed that all system inputs are measurable. This correspondence presents a simple and useful procedure for the construction of minimal-order state estimators for systems with unmeasurable disturbances.

Observing the states of systems with unmeasurable disturbances

Survey paper: A survey of some recent results in linear multivariable feedback theory

Reduced order observers: A new algorithm and proof

This paper presents a reduced-order memoryless state observer with a /spl gamma/-stability margin (0</spl gamma/<1) for linear discrete-time systems with multiple delays in both the state and control vectors. The dynamics of the observer are derived from a set of unstable and/or poorly damped eigenvalues of the system. A simple and systematic design method is presented. A numerical example is given to illustrate the properties of the new observer and its design method.

A memoryless state observer for discrete time-delay systems

A simple method of designing a stable (n – m)-state observer for an n-state linear deterministic system with m independent outputs is presented

S.D.G. Cumming

Papers

Design of observers of reduced dynamics