Disturbance Accommodating Control Theory Research Articles

Observer design and optimization for model-based condition monitoring of the wind turbine rotor blades using genetic algorithm

In this paper a model based approach for condition monitoring and diagnosis of faults in the wind turbine rotor blades is described. The investigation is focused on creating a fault-free reference system, the design and optimization of the controller/observer based on the Disturbance Accommodating Control theory and the multi-objective genetic optimization algorithm in order to further enhance the condition monitoring and faults diagnosis. Test cases are presented by injecting a parameter change, e.g. pitch angle, as an error to the non-linear wind turbine simulation model in order to demonstrate that the proposed method is able to detect the fault on the blades.

Non Linear Disturbance Accommodation Fuzzy Control

This paper deals with the problem of chaotic disturbances accommodation when these are generated by known non linear dynamics. In order to accomplish this goal, Takagi-Sugeno fuzzy models are called for as they offer the advantage of having virtually a linear rule consequent to approximate non linear systems. A control law inspired from the known disturbance accommodation control theory (DAC theory) is used to make the effects of disturbances vanish or attenuated while the considered linear plant is stabilized at the same time. An illustrative example is provided.

05/02091 Integration of a fuel cell into the power system using an optimal controller based on disturbance accommodation control theory

05/02091 Integration of a fuel cell into the power system using an optimal controller based on disturbance accommodation control theory

Integration of a fuel cell into the power system using an optimal controller based on disturbance accommodation control theory

Abstract In this paper, the integration of a fuel cell into the power system is treated as a load frequency control (LFC) problem with the fuel cell acting as a load disturbance source. The integration of a fuel cell into the power system results into a change in real power. But changes in real power affect the system frequency. Thus, the integration will result into a change of frequency of the synchronous machines. Hence, we need to design a control scheme for keeping the system in the steady state. An optimal controller based on the disturbance accommodation control (DAC) theory is proposed for this load frequency control problem. For demonstrating the effectiveness of the proposed controller, we have considered a two-area power system with the fuel cell introduced in area 1. The fuel cell is considered as an external disturbance to each subsystem. A mathematical model is derived for each subsystem and based upon these models controllers are designed for keeping each subsystem stable, which in turn stabilizes the overall system. So, the proposed controller is decentralized in nature. To account for the modeling uncertainties, an observer is designed to estimate each subsystem’s own and interfacing variables. The controller uses these estimates to optimize a given performance index and allocate generating unit outputs according to the requirements.

Dual-mode disturbance-accommodating pointing controller for Hubble Space Telescope

Cyclic thermal expansions and mechanical stiction effects in the solar arrays on the Hubble Space Telescope (HST) are triggering repeated occurrences of damped, relaxation-type flex-body vibrations of the solar arrays. Those solar array vibrations are, in turn, causing unwanted deviations of the telescope from its specified pointing direction. In this paper we propose two strategies one can adopt in designing a telescope-pointing controller to cope with the aforementioned disturbances: 1) a total isolation (TI) control strategy whereby the HST controller torques are designed to adaptively counteract and cancel out the persistent disturbing torques that are causing the unwanted telescope motions and 2) an array damping (AD) control strategy whereby the HST controller torques are used to actively augment the natural dampening of the solar array vibrations and the attendant telescope motions, between triggerings of the stiction-related flex-body relaxation oscillations. Using the principles of disturbance accommodation control theory, a dual-mode controller for a generic, planar-motion (single-axis) model of the HST is proposed. This controller incorporates both the TI and AD modes of disturbance accommodation. Simulation studies of the closed-loop system using generic parameter values clearly indicate, qualitatively, the enhanced pointing performance such a controller can achieve.

A singular condition in linear adaptive control theory

In a recent paper (Johnson 1985) the theory of disturbance-accommodating control was used to derive a new family of adaptive controllers. A critical step in the derivation presented by Johnson (1985) involves the assumption that certain higher-order perturbation terms are negligible with respect to terms that are linear in the perturbations. In the present paper the validity of that approximation is investigated and the special (singular) condition under which the assumption fails is identified and characterized in terms of a new observability-like determinant.

A ball balancing demonstration of optimal and disturbance-accomodating control

The modeling, analysis, and design of a ball-balancing control system are considered. An optimal linear regulator control system is constructed, and an optimal hybrid controller capable of absorbing external disturbance is implemented. The controller design is based on the theory of disturbance-accommodating control, optimal linear quadratic regulator control, and a digital delayed-data observer. Experimental results presented are useful for demonstrating practical aspects of the analysis. Furthermore, the ball-balancing control system developed is ideal for demonstrating the design and hardware implementation of optimal controllers based on modern control theory.

Adaptive controller design using disturbance-accommodation techniques

In this paper, the theory of disturbance-accommodating control (DAC) is extended to include the case of internal ‘disturbances’ arising from uncertain plant-parameter variations. This extension of DAC theory, when combined with existing DAC theory for external disturbances, leads to what is believed to be the first general theory of adaptive control for finite-dimensional linearized dynamical systems.

Disturbance-utilizing controllers for noisy measurements and disturbances I. The continuous-time case

Abstract In this paper, the theory of disturbance-accommodating control i" extended to the case of disturbances which may have both wave form-type and noise-type components. Moreover, the plant output measurements are allowed to be corrupted by additive noise. Continuous-time plants and controls are considered in the present paper. The discrete-time case is considered in a companion paper (Part II) which follows.

Discrete-time disturbance-accommodating control theory with applications to missile digital control

This paper describes an extension of the theory of (analog) disturbance-accommodating control to include a general class of control problems involving sampled-data and digital controllers. Digital control systems designed by the methods described herein will maintain performance specifications in the face of a wide range of disturbances encountered in practical applications. Design algorithms are derived for stabilization, set-point regulation, and servo-tracking digital control problems. Application of these results to the design of a digital control system for a missile is illustrated by an example.