22 research outputs found
Fault detection using transfer function techniques
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The implementation of a generalised robust adaptive controller
An adaptive controller is developed, comprising a robust parameter estimator
and an explicit pole assignment controller design. The controller
is reformulated to have a standard PID structure. A practical implementation
is facilitated on a digital microcomputer, connected to a physical
process. Test results are presented for this real process subject to
variable dead-time and an external disturbance. Simulation results are
also presented, for a nominally non minimum-phase process subject to variable
dead-time and large open-loop gain changes. Robust performance is
demonstrated under all of these circumstances. Recommendations are given
for the choices and considerations required in a robust practical implementation.
Much research has been done in the field of adaptive control over the past
few decades. However, a let needs to be learned about the robustness of
adaptive control algorithms. This research investigates the implementation
of a practical adaptive control algorithm, with numerous features
incorporated to improve the robust performance of such a controller. Parameter
estimation is performed using Recursive Least Squares (RLS), with
various signal conditioning filters to reduce estimator sensitivity to
noise and modelling errors. The control design is based on closed-loop
pole assignment, with adaptive feed forward compensation included. Further,
provision is made in both the estimation model and the feedback
control structure to eliminate deterministic immeasurable disturbances,
and to track deterministic set point variations. This is based on the
Internal Model Principle. Measured random disturbance signals are included
in the estimation model, for which "transfer function" polynomial
coefficients are estimated and then used in the feed forward control d e sign.
A new shift- operator, namely the 6-operator, is used in all controller
and estimator formulations. This has been shown to have better
numerical properties and to correspond more closely to continuous-time
control, than the traditional q operator of z-domain discrete control.
A practical implementation on a digital computer is investigated, applied
to a real plant typical of an industrial application. Simulation results
are also obtained for plant with non minimum-phase zeros and variable
dead-time
Control Engineering
Control means a speci?c action to reach the desired behavior of a system. In the control of industrial processes generally technological processes, are considered, but control is highly required to keep any physical, chemical, biological, communication, economic, or social process functioning in a desired manner
Integrated System Identification and Adaptive State Estimation for Control of Flexible Space Structures
Accurate state information is crucial for control of flexible space structures in which the state feedback strategy is used. The performance of a state estimator relies on accurate knowledge about both the system and its disturbances, which are represented by system model and noise covariances respectively. For flexible space structures, due to their great flexibility, obtaining good models from ground testing is not possible. In addition, the characteristics of the systems in operation may vary due to temperature gradient, reorientation, and deterioration of material, etc. Moreover, the disturbances during operation are usually not known. Therefore, adaptive methods for system identification and state estimation are desirable for control of flexible space structures. This dissertation solves the state estimation problem under three situations: having system model and noise covariances, having system model but no noise covariances, having neither system model nor noise covariances. Recursive least-squares techniques, which require no initial knowledge of the system and noises, are used to identify a matrix polynomial model of the system, then a state space model and the corresponding optimal steady state Kalman filter gain are calculated from the coefficients of the identified matrix polynomial model. The derived methods are suitable for on-board adaptive applications. Experimental example is included to validate the derivations
Bias Removal Approach in System Identification and Arma Spectral Estimation
Electrical Engineerin