Robust Decentralized Servomechanism Problem Research Articles

The structured robust decentralized servomechanism problem for interconnected systems

The decentralized robust control of a servomechanism problem for a composite system with interconnected subsystems is considered in this paper. Previous work is extended in two important ways. Firstly, each subsystem is assumed to have its own set of local reference and disturbance signals. Secondly, the perturbations which arise due to modelling uncertainty are shown to have a structured form due to interconnection topology. Necessary and sufficient conditions, together with a characterization of all decentralized robust controllers which enable asymptotic tracking to occur, independent of disturbances and structured perturbations in the plant, are obtained.

The Robust Decentralized Servomechanism Problem for General Inter-connected Systems

In [5], the robust decentralized servomechanism problem (RDSP) is analyzed for a composite system with interconnected subsystems. All subsystems are assumed to have the same set of local reference and disturbance signals. Specialization of the above results to deal with the case of input-output interconnections between subsystems is developed in [8]. In this paper, the case of heterogeneous tracking and regulation requirements for each subsystem is explored; that is, each subsystem has its own distinct set of local reference and disturbance signals. The structural properties of the system are used to solve the RDSP so that decentralized controllers have minimum order servocompensator [5] dynamics and give asymptotic tracking and regulation in the presence of structured system perturbations.

Reliability of Robust Decentralized Controllers

The following problem is considered. Assume a decentralized system has ѵ control agents in which the actuators (inputs) or/and sensors (outputs) are subject to failure. It is desired to solve the robust decentralized servomechanism problem [5] for the system, so that the following requirements are satisfied:(a) The closed loop system is asymptotically stable.(b) Robust error regulation occurs.(c) If a sensor or/and actuator failure occurs in one or more control agents, it is desired that requirement (a) still be satisfied and that requirement (b) be satisfied with respect to the non-failed control agent stations.This is called the robust decentralized servomechanism problem with reliability, and is a generalization of [1] which dealt with the notion of sequential reliability.Existence conditions and a control characterization are obtained to solve this problem, and a number of non trivial examples are given to illustrate the type of results obtained.

Time Scale Based Modular Synthesis of Controllers to Solve the Robust Decentralized Servomechanism Problem*

In [6], the Robust Decentralized Servomechanism Problem (RDSP) is formulated and solved. The controller existence conditions and construction techniques of [6] are based on a global knowledge of the plant dynamics. In this paper, we cast the RDSP in a multimodel situation. This is done by using the multiparameter singular perturbation characterization of multimodelling introduced in [9]. We consider a more restricted information flow between control agents than previous work in multimodelling [9], [10], [16]. The information flows considered are of two types: canonical and non-canonical. The existence conditions and construction techniques for controllers that solve the RDSP for both information flows are considered.

Simplified Design of Controllers to Solve the Robust Decentralized Servomechanism Problem for Large Systems

In [9], the Robust Decentralized Servomechanisiu Problem (RDSP) was formulated and solved. In [12], [13], and [15] parameter optimization techniques wore developed to design controllers with desirable properties: closed loop asymptotic regulation, fast response, low channel interaction, integrity and tolerance to plant variations. The methods of [12] and [13] produce excellent designs - however they are computationally demanding: this makes them impractical to apply directly to large scale system problems. In this paper, the multiparameter singular perturbation characterization of multimodelling introduced in [17] is used to decompose the complex RDSP into smaller manageable problems. The resulting simplified design yields a controller which behaves similarly to a controller that the complex design would produce.

The decentralized control of large flexible space structures

The decentralized robust servomechanism problem with constant disturbances/set points is considered in this paper for large flexible space structures (LFSS). It is shown that for LFSS which have colocated, mutually dual sensors and actuators, the decentralized fixed modes [1] of the system are precisely equal to the centralized fixed modes [2] of the system. Simple necessary and sufficient conditions are then obtained for a solution to exist for the robust decentralized servomechanism problem [3] for the system. A controller is demonstrated which, for this class of LFSS systems, eliminates the "spillover problem." A two-hundreth-order numerical example of an LFSS control problem using the Purdue model [4] is included to illustrate the results.

Reliability of the Robust Servomechanism Controller for Decentralized Systems

A study of the reliability of the robust servomechanism controller for decentralized systems is made. In particular, it is desired to find conditions for a υ-control agent system, so that there exists a solution to the robust decentralized servomechanism problem for the system, and such that when a failure occurs in controller j, the resultant failed system still has the property that regulation and tracking occurs for control agents 1, 2, ..., j-1, ∀jϵ[1, 2, ..., ν]. This is called the decentralized robust servomechanism problem with sequential reliability. Necessary and sufficient conditions to solve the sequential reliability problem are given and an algorithm to construct sequential reliable robust controllers is given. Some numerical examples are included to illustrate the results.

The robust decentralized-control of a servomechanism problem for composite systems with input-output interconnections

In [1], it was shown that under certain mild conditions, there "almost always" is a solution to the robust decentralized servomechanism problem for a composite system consisting of a number of subsystems interconnected in any arbitrary manner, provided that there exists a solution to the servomechanism problem for each subsystem. In this note, it is shown that for the special case when the composite system consists of subsystems interconnected by inputs and outputs, then there always is a solution to the robust decentralized servomechanism problem for the composite system if and only if there exists a solution to the robust servomechanism problem for each subsystem.

The robust decentralized servomechanism problem with extra stabilizing control agents

Results of a previous paper [1] on the decentralized robust control of a general servomechanism problem are generalized to include the effect of a system having control agents whose outputs are not to be regulated.

The robust decentralized control of a general servomechanism problem

The decentralized robust control of a completely general servomechanism problem is considered in this paper. Necessary and sufficient conditions, together with a characterization of all decentralized robust controllers which enables asymptotic tracking to occur, independent of disturbances in the plant and perturbations in the plant parameters, and gains of the system, are obtained. A new type of compensator called a decentralized sercocompensator which is quite distinct from an observer is introduced. It is shown that this compensator, which corresponds to an integral controller in classical control theory, must be used in any decentralized servomechanism problem to assure that the controlled system is stabilizable and achieves robust control; in particular, it is shown that a decentralized robust controller of a general servomechanism problem consists of two devices 1) a decentralized servocompensator and 2) a decentralized stabilizing compensator. It is then shown that, under certain mild conditions, there almost always is a solution to the robust decentralized servomechanism problem for any composite system consisting of a number of subsystems interconnected in any arbitrary manner. This last observation has important implications for process control.