Reconfigurable Control System Research Articles

A generic architecture of manufacturing cell control system

The depiction of an agile manufacturing cell includes a synopsis of some of the agilities obtained by the configuration. The agile configuration here brings additional values, such as rapid new product introduction, accommodation to unpredictable demand, longer equipment applicability, etc. To achieve agile configuration, the cell-control system for agile manufacturing must be rapidly and efficiently generated or modified. The high reconfigurability of cell-control software, such as modularity, reusability and maintainability, must be considered. The aim of this paper is to propose an objectoriented generic architecture that efficiently supports the design and implementation of highly reconfigurable control systems for agile manufacturing cells. The generic architecture is composed of resource objects, informational objects and control object. The structure of resource objects is proposed in detail. To develop cell-control software rapidly, the OPN model is established so as to describe the dynamic behaviour of a resource object, control logic, as well as exchanging with other objects.

Evaluating the performance of reactive control architectures for manufacturing production control

The requirement for adaptable and re-configurable control systems for manufacturing has highlighted the inadequacies of traditional centralised control approaches, leading researchers to focus on decentralised approaches. The question of what is the most appropriate control architecture for a given system has led industrial and academic researchers to develop a spectrum of decentralised control architectures ranging from hierarchical to non-hierarchical structures. While current research has confirmed the potential of decentralised architectures, neither extreme of this control architecture spectrum has proven to be the most appropriate choice for a given manufacturing system. Recent research into providing an objective comparison of alternative control architectures has shown that some degree of hierarchy is important for distributed manufacturing control architectures. This paper is concerned with our current investigations into why these partial hierarchies appear to display superior performance.

Study on the architecture of control system for manufacturing cells

The depiction of the agile manufacturing cell includes a synopsis of some of the change proficiencies obtained by the configuration. To achieve agile configuration, the cell control system for agile manufacturing must be rapidly and efficiently generated or modified. In this paper, the object-oriented architecture is defined that supports design and implementation of highly reconfigurable control systems for agile manufacturing cells, which is composed of database objects, control objects, and resource objects, so as to reduce costs and to increase the control system’ s agility with respect to changing environment.

Two Reconfigurable Flight-Control Design Methods: Robust Servomechanism and Control Allocation

Two methods for control system reconfiguration have been investigated. The first method is a robust servomechanism control approach (optimal tracking problem) that is a generalization of the classical proportional-plus-integral control to multiple input-multiple output systems. The second method is a control-allocation approach based on a quadratic programming formulation. A globally convergent fixed-point iteration algorithm has been developed to make onboard implementation of this method feasible. These methods have been applied to reconfigurable entry flight control design for the X-33 vehicle. Examples presented demonstrate simultaneous tracking of angle-of-attack and roll angle commands during failures of the fight body flap actuator. Although simulations demonstrate success of the first method in most cases, the control-allocation method appears to provide uniformly better performance in all cases.

Reconfiguration of flight control systems for actuator failures

We consider the problem of designing fault tolerant control for transient failures in the flight control system caused by harsh electromagnetic environments. We examine principles of fault tolerant design and discuss integrated local supervisory control of these systems. As an example, we present a sample design of a control mixer to achieve fault tolerance in the event of failures in the actuators.

Sensor Fault-Tolerant Control of an Induction Motor Drive System

This paper describes the application of a new fault-tolerant control scheme for nonlinear systems. The approach presented takes into account the stability and design of non-linear fuzzy inference systems based on Takagi-Sugeno (T-S) fuzzy models. The necessary conditions for eigenvalue assignability to a region in the s-plane are derived along with necessary conditions to guarantee the stability of adaptive fuzzy models for both diagnostic T-S fuzzy observers and controllers. The problem is solved using Linear Matrix Inequalities (LMI). The feasibility of this system architecture is demonstrated using a 3-phase induction motor laboratory rig as an example of a fault-tolerant system for applying principles of fault detection and isolation (FDI) and control system reconfiguration. The scheme uses the D space® software and digital signal processing to implement the fault detection and control system reconfiguration on the test rig.

Multiple-Model Fault-Tolerant Control of an Induction Motor in the Presence of Uncertainty

This paper describes the application of a new fault-tolerant control scheme for nonlinear systems. The approach presented takes into account the stability and design of non-linear fuzzy inference systems based on Takagi-Sugeno (T-S) fuzzy models. The necessary conditions for eigenvalue assignability to a region in the s-plane are derived along with necessary conditions to guarantee the stability of adaptive fuzzy models for both diagnostic TS fuzzy observers and controllers. The problem is solved using Linear Matrix Inequalities (LMI). The feasibility of this system architecture is demonstrated using a 3-phase induction motor laboratory rig as an example of a fault-tolerant system for applying principles of fault detection and isolation (FDI) and control system reconfiguration. The scheme uses the D space software and digital signal processing to implement the fault detection and control system reconfiguration on the test rig.

Actuator fault-tolerant control design: Demonstration on a three-tank-system

Fault-tolerant control or reconfigurable control systems are generally based on a nominal control law associated with a fault detection and isolation module. A general review of techniques dealing with this problem is given and a new fault-tolerant control approach is presented. This method is based on the on-line estimation of an eventual fault and the addition of a new control law to the nominal control law in order to reduce the fault effect once this fault is detected and isolated. The performances of this method depend on the time delay between the occurrence of the fault and its detection and isolation. A modified approach is then proposed in order to avoid the problems generated by delays, false alarms or non-detection inherent to diagnosis techniques. These methods are applied to a pilot plant and their performances are compared and discussed.

A generic event control framework for modular flexible manufacturing systems

A generic event control framework is presented for a class of modular flexible manufacturing systems (FMSs). A modular FMS is characterized as a set of flexible workstations inter-connected by a material handling system consisting of a transporter and a stocker. Many of the existing FMS implementations in industry fall into this class. Furthermore, the modularity also allows the capability to effectively model a complex FMS by decomposing it into several modular FMSs. In order to achieve reconfigurability of control system for various FMS implementations and control policies, the proposed control framework is defined as a set of distributed resource controllers and a central system supervisor coordinating them. The resource controllers are further classified into workstation, transporter, and stocker controllers. As the controllers exchange a series of events according to pre-defined protocols, they are modelled as event handlers in which control actions are made based on the event occurrences. Specifically, for each controller, an event-based control structure specified in terms of generic logical and performance control functions, is presented. Since the proposed framework is defined by the use of the interacting distributed processes with the well-defined protocols and computationally efficient algorithms, it is expected that the framework is easily implementable for most industrial FMSs. Finally, the performance and reconfigurability is demonstrated by the distributed simulation from which we can also verify the correctness of the proposed algorithms.

Optimal redundancy management in reconfigurable control systems based on normalized nonspecificity

In this paper, the notion of normalized nonspecificity is introduced. The nonspecificity measures the uncertainty of the estimated parameters that reflect impairment in a controlled system. Based on this notion, a quantity called a reconfiguration coverage is calculated. It represents the likelihood of success of a control reconfiguration action. This coverage links the overall system reliability to the achievable and required control, as well as diagnostic performance. The coverage, when calculated on-line, is used for managing the redundancy in the system.

Fault monitoring and re‐configurable control for a ship propulsion plant

Minor faults in ship propulsion and their associated automation systems can cause dramatic reduction on ships' ability to propel and manoeuvre, and effective means are needed to prevent simple faults from developing into severe failure. The paper analyses the control system for a propulsion plant on a ferry. It is shown how fault detection, isolation and subsequent reconfiguration can cope with many faults that would otherwise have serious consequences. The paper emphasizes analysis of re-configuration possibilities as a necessary tool to obtain fault tolerance, showing how sensor fusion and control system reconfiguration can be systematically approached. Detector design is also treated and parameter adaptation within fault detectors is shown to be needed to locate non-additive propulsion machinery faults. Test trials with a ferry are used to validate the principles. © 1998 John Wiley & Sons, Ltd.

Fault monitoring and re-configurable control for a ship propulsion plant

Minor faults in ship propulsion and their associated automation systems can cause dramatic reduction on ships' ability to propel and manoeuvre, and effective means are needed to prevent simple faults from developing into severe failure. The paper analyses the control system for a propulsion plant on a ferry. It is shown how fault detection, isolation and subsequent reconfiguration can cope with many faults that would otherwise have serious consequences. The paper emphasizes analysis of re-configuration possibilities as a necessary tool to obtain fault tolerance, showing how sensor fusion and control system reconfiguration can be systematically approached. Detector design is also treated and parameter adaptation within fault detectors is shown to be needed to locate non-additive propulsion machinery faults. Test trials with a ferry are used to validate the principles. © 1998 John Wiley & Sons, Ltd.

Reconfigurable Control System Synthesis Using Parameter Estimation and Robust Control

Abstract A new design scheme of a Reconfigurable Control System (RCS) based on a bounding parameter estimation scheme and the parametric robust control method is proposed in this paper. The main advantage of this approach over the existing ones is that it allows the systen designers to integrate the Fault Detection and Isolation (FDI) schemes with the reconfigurable control at the control system design stage. To demonstrate the effectiveness of the proposed scheme, an illustrative example is presented. The simulation results indicate that the proposed scheme has some distinctive features which are potentially useful in the development of a truly Fault Tolerant Control System (FTCS).

Reliability Criteria Based Reconfigurable Control System Design

Abstract A performance measure for a reconfigurable control system is introduced in the form of an interval between two values of coverage that is to enter the overall system reliability computation. The size of the interval is a reRection of information deficiency. The definition of such coverage depends explicitly on the performance measures of a control module and a diagnostic module. It allows us, in a precise manner, to depict the relationships between the overall system reliability and the performance requirements on these modules. An example is given to show how reliability is functionally related to the values of diagnostic resolution and of control performance threshold.

Novel approach to reconfigurable control systems design

Abssact: A novel linear model fdlowing appoach is proposed fa: rmfigurable contrd systems design, where a unique system configuration and design method are employed. It compares favOcaMy to the existing methods in that the design pw;edure is quite s t r a i g h t f i d and does not require intensive computation. Furthermure, it is shown that the new method provides better tracking perfopmane by significantly reducing the unstraints d pafea model following. It is also shown (hat even when perfect model fdlowing is not achieved, the pqmed approtach still minimizes the upper bound of the tracking m. The effectiveness d the new design approach is demonstrated in an aircraft longitudinal control system problem where it is compared to a recently proposed method.

A real-time reconfigurable entrance control system

A real-time reconfigurable entrance control system is presented in this paper. The system is designed and implemented with considering compatibility with the existing systems, reliability, expandability, and maintenance. The presented system consists of a host which manages a central database, terminals which control entrances, and terminal controllers which connect the host with terminals. To utilize the existing popular network, Ethernet is used for the network between the host and terminal controllers, while LONNET is used to connect terminal controllers and terminals. The software in each terminal controller and terminal is divided into two parts. The kernel part which is unchangeable for the normal cases is responsible for low level communication and house keeping. The application part controls peripherals. It can be replaced with a new one with aid of the kernel during initialization process or even on-line operation. With this approach, an application program can be modified without stopping the system. Another advantage is that installation and maintenance become very easy, saving the related cost.

New plans for FIRST far infrared and sub-millimetre space astronomy mission for 2007

The Far Infra Red and Submillimetre space Telescope (FIRST) mission is an ESA “cornerstone” mission planned for the year 2007. This paper describes the new status of the FIRST satellite design following a redefinition of the mission in 1992/3 to better meet the cost targets. One challenging aspect of this redefinition was the substitution of the large liquid helium cryostat by Stirling cycle mechanical coolers. This posed a number of new thermal and configuration problems. In addition, a new payload complement configuration had to be defined which retained as many of the originally planned scientific capabilities of the system as possible, and which also optimised the instruments' compatibility with the cooling system. Other changes to the design included a reduction in the diameter of the primary reflector with corresponding cost and configurational benefits, and the reconfiguration of the attitude control system to use only existing hardware. These measures had to be introduced with minimum loss of mission capability.

Fault detection-isolation and control reconfiguration

In industrial applications of process control, we can find a very large variety of supervision structures including diagnosis and prognosis techniques. Here, we are concerned with the problem of reconfigurable control systems that possess the ability to accommodate failures. After some general considerations about reconfiguration, this paper moves on the conception of a supervision scheme which includes: the identification of the process parameters, the detection of modifications of the process, the adaptation of the control input in case of parameters variations.

Minimal Time Change Detection Algorithm for Reconfigurable Control System and Application to Aerospace

System parameters should be tracked on-line to build a reconfigurable control systems even though there exists an abrupt change. For this purpose, a new performance index that we are studying is the speed of adaptation - how quickly does the system determine that a change has occurred? In this paper, a new, robust algorithm that is optimized to minimize the time delay in detecting a change for fixed false alarm probability is proposed. Simulation results for the aircraft lateral motion with a known or unknown change in control gain matrices, in the presence of doublet input, indicate that the algorithm works fairly well. One of its distinguishing properties is that detection delay of this algorithm is superior to that of Whiteness Test.

Fault Detection/Diagnosis and Controller Reconfiguration in Dynamic Systems

A novel reconfigurable control system has been designed by combining a newly developed fault detection/diagnosis scheme with a model following control strategy. The fault detection/diagnosis is carried out in s - domain by estimating the modal information of the system, and comparing the eigenvalues of the faulty system with a pre-determined set of root loci. The model following control scheme utilizes the pre-fault system model as a reference model to compute the reconfigured controller. The performance of the scheme has been evaluated on a simulated DC motor system where various types of faults are introduced.