Control Design For Interconnected Systems Research Articles

Structured Controller Design for Interconnected Systems via Nonlinear Programming

Dear Editor, This letter deals with the structural controller design problem of interconnected systems with unknown feedback topology. Firstly, under a cardinality constraint on the directed communication links among sub-controllers, a distributed controller's feedback gain and feedback topology are incorporated in a unified co-design framework. Secondly, the cardinality constraint introduced in the distributed control is represented by a binary integer programming. To deal with the complementary constraint, a nonlinear programming (NLP) is proposed to relax the binary integer programming. Finally, incorporating the NLP into the standard distributed event-triggered control method, an algorithm is developed for interconnected systems to simultaneously design the feedback topology and controller gain.

Abstraction-based control synthesis using partial information

The problem studied in this paper is that of distributed controller design for interconnected systems using abstraction-based techniques. Controller synthesis for each subsystem uses local distributed sensor information from other subsystems. Such partial information in an abstraction will be characterized in terms of ranking functions which can be deemed as level sets of Lyapunov functions. An effective procedure is proposed for the computation of ranking functions in the case of reach and stay specifications. A step-by-step algorithmic procedure implementing the proposed approach is presented for controller synthesis based on partial information. A numerical example is provided to illustrate the implementation.

Decentralised controller design for a class of interconnected systems

This study considers the decentralised controller design for interconnected systems. For the case that the interconnections satisfy certain matching conditions, a decentralised static controller is presented, which is designed in a separate way. On the basis of the presented controller, a relaxed sufficient condition is proposed, and the corresponding decentralised static controller is also given. Furthermore, the decentralised dynamic controller is designed for interconnected systems with two subsystems satisfying the relaxed sufficient condition. The efficiency of proposed controllers is demonstrated both theoretically and numerically.

Output feedback overlapping control design of interconnected systems with input saturation

In this paper, we establish new results to the problem of output feedback control design for a classof nonlinear interconnected continuous-time systems subject to input saturation. New schemes basedon overlapping design methodology are developed for both static and dynamic output feedback controlstructures. The theoretical developments are illustrated by numerical simulations of a linearized nuclearpower plant model.

Performance-oriented communication topology design for distributed control of interconnected systems

Communication networks provide a larger flexibility for the control design of interconnected systems by allowing the information exchange between the local controllers of the subsystems which can be used to improve the overall system performance. However, the interconnected systems may become unstable due to permanent communication link failures. This article presents a novel two-layer control architecture that allows to jointly improve the system performance which is the decay rate and guarantee the stability of the interconnected system under permanent communication link failures. As a novelty, the design of communication topology between the local controllers is also taken into account. On the other hand, it is still not well understood how significant the role of each possible communication link is in improving the system performance. Another novelty of this article is thus to propose a method based on eigenvalue sensitivity analysis in order to characterize the influence of each possible communication link in improving the performance of the overall system. In addition, for a special class of systems and physical interconnection topology, explicit solutions on communication topology design are derived for the first time. The solutions provide some insights into how the heterogeneity of the subsystem local dynamics, the strength of interconnection and the size of the network affect the optimal communication topology.

A New Scheme on Robust Observer-Based Control Design for Interconnected Systems With Application to an Industrial Utility Boiler

This paper presents a new design algorithm for the decentralized output feedback control problem of large-scale interconnected systems. Each subsystem is composed of a linear (possibly unstable) time-invariant part and an uncertain additive nonlinearity which is a discontinuous function of time and state of the overall system. The nonlinear function is assumed to be bounded by a quadratic inequality, and a decentralized estimated state feedback controller and a decentralized observer are designed for each subsystem, based on linear matrix inequalities. Sufficient conditions for the synthesis of feedback action are provided, under which the proposed controllers and observers can achieve robust stabilization of the overall large-scale system. An attractive feature of the proposed scheme is that it guarantees connective stability of the overall system and requires no intersubsystem communication. The controller design is evaluated on a natural circulation drum boiler, where the nonlinear model describes the key dynamical properties of the drum, the risers, the downcomers, and the turbine-generator unit. The linearized system has two poles at origin, one associated with water dynamics and the other with generator dynamics. Simulation results are presented that show the effectiveness of the proposed control against instabilities following sudden load variations. The control is also effective for steady-state operation.

Stabilization of decentralized control systems by means of periodic feedback

This paper deals with structurally constrained periodic control design for interconnected systems. It is assumed that the system is linear time-invariant (LTI), observable and controllable, and that its modes are distinct and nonzero. It is shown that the notions of a quotient fixed mode (QFM) and a structured decentralized fixed mode (SDFM) are equivalent for this class of systems. Then, it is proved that if the system is decentrally stabilizable, then one candidate for the decentralized stabilizing controller is a time-varying one consisting of a decentralized LTI discrete-time compensator and a zero-order hold. More specifically, the non-quotient fixed modes of the system will be eliminated via sampling for almost all sampling periods, while any QFM will still remain a fixed mode. The results obtained are ultimately extended to the case when the system has some repeated modes, none of which is a DFM.

Decentralized Sliding Mode Control Design for Interconnected Systems

This paper presents a decentralized sliding mode control scheme for a linear interconnected system, where the controller of each subsystem needs only local information to work. A sufficient condition under which the sliding surface and a sliding mode controller are certainly determined is given in terms of the Riccati equation on the subsystem level. This condition is equivalent to the stabilizability condition by decentralized state feedback. Thus, our results are more reasonable and less conservative than those reported in previous works.

Analysis and Control of Interconnected Discrete System Using Robust Stability Condition

This paper presents sufficient conditions for the stability of interconnected discrete systems and interconnected uncertain discrete systems. The stability conditions are developed by employing the property of spectral radius. It is shown that the stability conditions can be used in designing controllers for interconnected uncertain discrete systems. Specifically, using the proposed condition yields a new robust control design method for interconnected uncertain discrete system. A controller designed by the proposed method is demonstrated for a sample system. The proposed method significantly simplifies a robust controller design for interconnected systems.

Robust control design for interconnected systems with time-varying uncertainties

Abstract We consider a design of decentralized control for a class of interconnected non-linear dynamical systems having uncertainty. This uncertainty is (possibly fast) time-varying, and it may appear in each system as uncertain parameter and input disturbance. It also may appear in the interconnections. No statistical information about the uncertainty is imposed; only its possible bound is assumed to be known. The two control schemes proposed here, namely the linear and the non-linear, take the bounds of the interconnections into account. The use of the non-linear control requires more assumptions than the use of linear control. In applications where these assumptions are met, the designers have both controls at their disposal, and depending on the particular application, one may be preferable to the other.

A Method of Decentralized Controller Design for Interconnected Systems

In this paper, a design method of decentralized controller for interconnected large systems by using dynamical local output feedback is presented. The local controller for each system is designed individually and the overall system is stabilized The resultant system is robust with respect to the structural perturbation.