Decentralised Control Law Research Articles

Affine transformation‐based no‐beacon circular formation of agents

This paper proposes a circular formation control algorithm for a group of agents to form a circular motion behaviour without the guidance of a global beacon. The control law consists of two parts which correspond to two systems (original system and reference exosystem) based on affine transformation. First, a displacement-based decentralised control law is used to form a regular polygon formation for the reference exosystem. Second, let the original system track a rotating motion of reference exosystem by affine transformation. Combining the above two steps, the proposed strategy ensures exponential convergence of a group of single-integrator modelled agents to the desired circular formation. Then, the authors generalise the approach to double-integrator and unicycle type. Both theoretical analysis and numerical simulations are given to show the effectiveness of the proposed strategies.

Robust decentralised state feedback control design for large-scale networked control system

ABSTRACTThis paper deals with robust decentralised feedback control for large-scale networked control systems (NCSs). A NCS model is extended to a class of large-scale system. Less conservative sufficient conditions are formulated in the form of a nonconvex matrix inequality, of which a feasible solution can be obtained by solving an optimisation problem in terms of linear matrix inequalities. The sufficient conditions are constructed by a set of new Lyapunov–Krasovskii functionals, which are based mainly on the lower and upper bounds of delay and packet loss. An explicit expression for the desired robust decentralised state feedback control law is also given. In order to verify the proposed method, it is applied to a numerical example and the load frequency problem in a multi-area power system. The simulation results show good performance and more robust stability against digital network communications delays, packet loss and external disturbances.

Decentralised finite-time attitude synchronisation and tracking control for rigid spacecraft

The problem of finite-time attitude synchronisation and tracking for a group of rigid spacecraft nonlinear dynamics is investigated in this paper. First of all, in the presence of environmental disturbance, a novel decentralised control law is proposed to ensure that the spacecraft attitude error dynamics can converge to the sliding surface in finite time; then the final practical finite-time stability of the attitude error dynamics can be guaranteed in small regions. Furthermore, a modified finite-time control law is proposed to address the control chattering. The control law can guarantee a group of spacecraft to attain desired time-varying attitude and angular velocity while maintaining attitude synchronisation with other spacecraft in the formation. Simulation examples are provided to illustrate the feasibility of the control algorithm presented in this paper.

Decentralised event-triggered cooperative control with limited communication

This note studies event-triggered control of Multi-Agent Systems (MAS) with first-order integrator dynamics. It extends previous work on event-triggered consensus by considering limited communication capabilities through strict peer-to-peer non-continuous information exchange. The approach provides both a decentralised control law and a decentralised communication policy. Communication events require no global information and are based only on local state errors; agents do not require a global sampling period or synchronous broadcasting as in sampled-data approaches. The proposed decentralised event-triggered control technique guarantees that the inter-event times for each agent are strictly positive. Finally, the ideas in this note are used to consider the practical scenario where agents are able to exchange only quantised measurements of their states.

05/02142 Using a FACTS device controlled by a decentralised control law to damp the transient frequency deviation in a deregulated electric power system

05/02142 Using a FACTS device controlled by a decentralised control law to damp the transient frequency deviation in a deregulated electric power system

Using a FACTS device controlled by a decentralised control law to damp the transient frequency deviation in a deregulated electric power system

In a deregulated electric power system, energy exchanges may exist depending on load following contracts between agents belonging to different areas. As direct consequence of this, the need may arise for new control apparatus and new effective control laws that favour power flows along specific corridors. In such a context, in the paper a great interest has been devoted to the use of FACTS devices to improve the load–frequency control of the system. Indeed, FACTS devices can regulate the power flow in a transmission line, also improving both transient and dynamic stability. This paper then proposes a method based on the application of the overlapping decomposition technique, to design a decentralised control law of a SSSC device. The principal idea is so to decompose a multi-area power system into two decoupled subsystems. The SSSC represents the former subsystem, while the latter is made up of the whole multi-area power system with inside the conventional controllers. As a consequence, each subsystem may be considered as independent. Greater simplicity hence results in designing decentralised optimal control laws for each of them with respect to a defined performance index. In the paper, in order to verify the validity of the proposed method, some numerical tests are carried out.

Improved condition for the optimality off decentralised control for large-scale systems

For a linear constant large-scale system composed for interconnected subsystems, if a decentralised control law which minimises a quadratic cost function with respect to individual decoupled subsystems is used, this simple control strategy is shown to result in a globally optimal interconnected system, provided the condition given by M. Ikeda and D.D. Siljak (1982) is satisfied and the quadratic cost function is modified to include the additional terms arising from the subsystem interactions. An improved condition for the global optimality is given, which implies that, as long as a local eigenvalue condition given in the paper is satisfied for the decentralised local optimal control and the global detectability condition is satisfied, global optimality can also be ensured. It can be expected that, owing to this new simple condition, some of the difficulties in the application of decentralised optimal control approaches could be overcome. >

Design of decentralised load-frequency regulators for interconnected power systems

The paper presents a new method of designing decentralised load-frequency regulators for interconnected power systems. Within the framework of this method, the interconnected mutliarea power system is decomposed into several subsystems, each of which is controlled separately by a decentralised regulator. Each subsystem consists of one area and its external equivalent in a simplified form. A decentralised control law for the study area is introduced by using a quadratic performance index. Feedback gains of the decentralised regulator, which minimise the index, are determined by a Newton-Raphson iterative algorithm. The proposed method is applied to an interconnected longitudinal 4-area system, and the effects of the proposed regulator are examined by digital simulations and associated sensitivity analysis of the system. Furthermore, a suitable means for preventing excessive control action is also considered involving a significant system nonlinearity, i.e. some generation rate constraint.