Reconfigurable Control System Research Articles

Functional reconfiguration of sensitive elements motion control system of the space vehicle

В статье рассмотрен алгоритм функциональной реконфигурации измерительных приборов системы управления движением для обеспечения целевой эффективности непилотируемых космических аппаратов.

Adaptation of System Configuration under the Robot Operating System

This paper lays down the foundations of developing a reconfigurable control system within the Robot Operating System (ROS) for autonomous robots. The essential components of robots are programmed under a ROS system. A formal model is defined as a tripartite graph to represent the robots functional architecture. ROS systems are then generalised to component libraries for any ROS architecture and an abstract model as a “system graph” is introduced. Orthogonality of a library and a system graph is defined and redundancy levels of robot components are studied for maintaining full functionality of the robot by automated reconfiguration in face of hardware malfunction. This allows AI planning tools, such as Planning Domain Definition Language (PDDL), to compute permissible reconfigurations. We present an example of a pair of robotic arms which requires reconfiguration of the underlying control system in order to retain the capability to carry out a task.

Reconfiguration and optimization of flight control system based on multi-model adaptive method

For the reconstruction problem of the flight control law when aircraft actuator was damaged or in failure cases,a new reconfiguration scheme of flight control system was proposed based on the linear quadratic optimal control theory and multi-model adaptive method.Based on fault diagnosis and detection technology,the reference model was obtained by the Linear Quadratic Regulator(LQR).Lyapunov stability theory was applied to ensure the strictly positive real parts and global asymptotic stability of the closed-loop control system.According to the vehicle dynamics control law for fault identification and model switching,the reconfiguration and optimization of vehicle control law based on the multi-model adaption was designed.Against the typical fault conditions,the reconfiguration simulation of the flight control system was made to verify the method,and the corresponding verification results were given,which can ensure that the aircraft effective operation.

Reconfigurable fault-tolerant controller synthesis for a steer-by-wire vehicle using independently driven wheels

In this paper, a synthesis method for a reconfigurable fault-tolerant control system for use in a steer-by-wire vehicle is proposed. The vehicle considered in this paper is also assumed to have independently driven wheels. The control objective in this work is to enable the vehicle yaw rate to track the reference signal even when the steering actuator breaks down. Since the vehicle yaw rate can be controlled with either the front wheel turn angle or the yaw moment generated by the independently driven wheels, this system has actuator redundancy. We attempt to design a control system that manages this actuator redundancy so that the performance degradation due to the actuator failure is minimised. We utilise a control allocator based on on-line optimisation for managing the actuator redundancy. The fault-tolerant control system with a control allocator has several excellent properties. For example, the method can handle various failure situations. Also, since the control allocation problem is reduced to a convex quadratic programming problem, the on-line computational effort is relatively little. However, so far, it has been unclear whether the stability of the control system with the control allocator is guaranteed when the actuator failure occurs. Therefore, we propose a design method of a fault-tolerant controller based on on-line optimisation that guarantees the stability of the overall system. The effectiveness of the method is established through numerical examples.

Detecting and Tolerating Faults in Switched Reluctance Motors

The switched reluctance motor (SRM) has inherently high level of fault tolerance. However despite of its high robustness and reliability it can face windings and bearings faults. The faults can cause costly downtimes in industrial environment, or they can bring about more severe consequences in safety critical applications. Therefore the detection of the faults in their incipient phase and the ability to tolerate them is a very important requirement for the electrical drive systems used in such applications. The paper deals with the most important faults of the SRMs, their effects on the machine performances and their detection. Also a reconfigurable fault tolerant control system for the SRMs is proposed, which is able to detect diverse winding faults and to mask these faults by imposing increased currents in the healthy remained coils of the machine. The fault detection capability and the correct reconfiguration of the proposed control system are proved by laboratory tests.

Proactive fault‐tolerant model predictive control

Fault‐tolerant control methods have been extensively researched over the last 10 years in the context of chemical process control applications, and provide a natural framework for integrating process monitoring and control aspects in a way that not only fault detection and isolation but also control system reconfiguration is achieved in the event of a process or actuator fault. But almost all the efforts are focused on the reactive fault‐tolerant control. As another way for fault‐tolerant control, proactive fault‐tolerant control has been a popular topic in the communication systems and aerospace control systems communities for the last 10 years. At this point, no work has been done on proactive fault‐tolerant control within the context of chemical process control. Motivated by this, a proactive fault‐tolerant Lyapunov‐based model predictive controller (LMPC) that can effectively deal with an incipient control actuator fault is proposed. This approach to proactive fault‐tolerant control combines the unique stability and robustness properties of LMPC as well as explicitly accounting for incipient control actuator faults in the formulation of the MPC. Our theoretical results are applied to a chemical process example, and different scenaria were simulated to demonstrate that the proposed proactive fault‐tolerant model predictive control method can achieve practical stability and efficiently deal with a control actuator fault. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2810–2820, 2013

Dynamic reconfigurability of control systems using IEC 61499 standard

The reconfigurable control systems are able to rearrange dynamically the system elements in order to accommodate the failure events and the new requirements. Reconfigurability of control systems is highly related to satisfying the requirements for interoperability, configurability, integrability, modularity, customization, scalability, convertibility, diagnosability and portability. All these features of control system are reachable using the reference architecture and models provided in the IEC 61499 standard. The event-driven structure of the models and applications supports the reconfigurability but there is no recommended solution to this issue, given in the standard. This paper presents and discusses an approach for model driven development of reconfigurable control systems based on IEC 61499 standard. For achieving dynamic reconfigurability of control application the concepts of management resource and device are defined and applied. The proposed development life cycle including design and implementation of control system is simplified through the software engineering concept of model driven architecture and model driven engineering (MDA/MDE), based on development of reusable platform independent models (PIM) and their transformation to different platform specific models (PSM), depending on the selected device. The suggested approach is illustrated with a case study for model driven development of reconfigurable control system for FESTO processing station S-BE-M, to which two new modules are developed and added in order to test different reconfiguration scenarios.

Distributed actuator reconfiguration in networked control systems

In this paper, we address the problem of distributed reconfiguration of first-order networked control systems under actuator faults. In particular, we consider the scenario where a network of actuators cooperates in order to recover from actuator faults. Such recovery is performed through a reconfiguration which minimizes the performance loss due to actuator faults, while guaranteing that the same state trajectory is obtained. The design of the distributed reconfiguration scheme is proposed and evaluated in numerical examples.

Modular robust reconfigurable flight control system design for an overactuated aircraft

In this study a modular approach to the robust reconfigurable flight control system design for an overactuated aircraft is proposed. The structure of the proposed scheme consists of three parts: a backstepping controller module, a robust control allocator and an online actuator effectiveness estimator. Firstly, the backstepping control law is developed for the strict feedback form of an Aero-Data Model in Research Environment aircraft to produce the desired commands. Furthermore, a novel robust optimisation-based control allocation algorithm is proposed to distribute the commands among redundant actuators with the consideration of control effectiveness uncertainties. Lastly, the control effectiveness factors are introduced to denote the healthiness of the actuators, and the least trimming squares-based estimator is designed for online estimation of the actuator effectiveness. With the proposed scheme, good tracking performance, robustness and reconfigurable capability are achieved. Evaluation of the overall system is accomplished by numerical simulation with various conditions, including adverse scenarios where actuator failures occur. The results show the effectiveness of the proposed scheme.

Designing similarity measurement with distance measure and application on laterally directional mode flight test

Similarity measure construction has been proposed as fault detection of flight test method in order to obtain the primary control surface stuck and the combination stuck of primary control. Similarity measures were obtained through analyzing the certainty and uncertainty of fuzzy membership functions, which were designed based on well-known Hamming distance. It was applied to the fault detection of primary control surface stuck of uninhabited aerial vehicle (UAV). At post-failure control surface, if the UAV is controllable and trimmable using other control surfaces, the UAV is able to fly or return to the safety region through reconfiguration of flight control system. To detect the fault, similarity measure computations were carried out. This result could be applicable with the real-time parameter estimation method. By monitoring the value of coefficients due to the control surface deviation, it becomes aware that the control surface fault occurs or not. The control surface stuck position and value were separated by comparing the trim value with the reference value. This is the advantage of increasing in reliability without adding sensors or with additional low cost.

Reconfigurable flight control for robust transient response

When a control surface fails during aircraft flying, reconfigurable control system with new configuration aims to use the other available control surfaces and attempts to preserve the design properties of the original system. Restoring transient response is particularly important when transition from damaged to healthy configuration takes place. In this article, a new design procedure for robust transient response of the reconfigured system is presented. A linear algebraic formulation for right eigenstructure assignment in state feedback format is derived. A system of linear equations for the controller is solved. Reconfigurable control using an F-18 model is illustrated.

UML-Based Design and Validation of Intelligent Agents-Based Reconfigurable Embedded Control Systems

The paper examines UML-based design and validation of reconfigurable embedded control systems which can have multiple software architectural configurations such that each one is designed by a set of inter-connected software components. To handle dynamic reconfiguration scenarios, the authors define a software agent which interacts with users and applies several forms of reconfiguration at different granularity levels of the system’s architecture. The agent has the ability of monitoring the system’s environment and to apply appropriate and valid reconfiguration scenarios under well-defined constraints. Three architectural levels are defined in order to consider all possible reconfiguration forms of embedded systems. The authors define a set of UML-compliant metamodels to describe the knowledge about the reconfiguration agent, the system architecture, the reconfiguration scenarios, and the reconfiguration events. Validity of reconfigurations scenarios are checked using an UML-based environment which allows evaluating architectural and reconfiguration constraints. The proposed reconfiguration approach is applied to the FESTO production system.

Discussion on: “Decentralized Fault Free Model Approach for Fault Detection and Isolation of Discrete Event Systems”

In this paper, we focus on the problem of incremental system identification for the purpose of automatic reconfiguration of control systems. We consider the particular case where a linear time-invariant system is augmented with either an extra sensor or an extra actuator and derive prediction error methods for recursively estimating the additional parameters while retaining the existing system model. Next, we propose a novel measure of the “usefulness” of new signals that appear in an existing control loop due to the addition of a new device, e.g., a sensor. This measure, which we refer to as awareness, indicates if there is a relation between the signal provided by the new device and the existing process, as well as what the new device is good for in terms of control performance. Finally, a simulation example illustrates the potentials of the proposed method.

Awareness and its use in Incremental Data Driven Modelling for Plug and Play Process Control

In this paper, we focus on the problem of incremental system identification for the purpose of automatic reconfiguration of control systems. We consider the particular case where a linear time-invariant system is augmented with either an extra sensor or an extra actuator and derive prediction error methods for recursively estimating the additional parameters while retaining the existing system model. Next, we propose a novel measure of the “usefulness” of new signals that appear in an existing control loop due to the addition of a new device, e.g., a sensor. This measure, which we refer to as awareness, indicates if there is a relation between the signal provided by the new device and the existing process, as well as what the new device is good for in terms of control performance. Finally, a simulation example illustrates the potentials of the proposed method.

Fault-tolerant control design for trajectory tracking in driver assistance systems

The paper proposes a control system with the brake and the steering for developing a driver assistance system. The purpose is to design a cruise control method to track the road geometry with a predefined velocity and guarantee the road stability of the vehicle simultaneously. An actuator selection method is developed in the control design, in which the actuator limits, energy requirements and vehicle operations are taken into consideration. The method is extended with a fault-tolerant feature based on a robust LPV method, into which the actuator selection procedure and the detected fault information are incorporated. The operation of the reconfigurable control system is illustrated through various vehicle manoeuvres.

Invariant-set-based fault tolerant control using virtual sensors

In this study an invariant-set approach to sensor FDI is employed together with control system reconfiguration based on the use of a virtual sensor. In the proposed FDI approach, invariant sets are specified for each considered healthy/faulty situation in the system's sensor structure. The detection mechanism is based on the separation between the computed invariant sets and ‘transition’ sets where appropriate residual variables ‘jump’ when faults occur. The closed-loop system is then reconfigured by means of a virtual sensor which is adapted to the detected fault. Furthermore, conditions are derived in terms of bounds on reference signals, noise and disturbances which guarantee the stability of the closed-loop system under the resulting fault tolerant control scheme for all considered fault situations. Simulation results of the proposed scheme on a longitudinal car following scenario and experimental results on a laboratory scale magnetic levitation system confirm the validity of the approach under realistic conditions.

Data‐based monitoring and reconfiguration of a distributed model predictive control system

SUMMARYIn this work, we develop a data‐based monitoring and reconfiguration system for a distributed model predictive control system in the presence of control actuator faults. Specifically, we first design fault detection filters and filter residuals, which are computed via exponentially weighted moving average, to effectively detect faults. Then, we propose a fault isolation approach that uses adaptive fault isolation time windows whose length depends on the rate of change of the fault residuals to quickly and accurately isolate actuator faults. Simultaneously, we estimate the magnitudes of the faults using a least‐squares method and based on the estimated fault values, we design appropriate control system reconfiguration (fault‐tolerant control) strategies to handle the actuator faults and maintain the closed‐loop system state within a desired operating region. A nonlinear chemical process example is used to demonstrate the approach. Copyright © 2011 John Wiley & Sons, Ltd.

공압형 인공근육을 이용한 상극 구동의 모델 추정 및 정밀 위치제어

This paper presents a frequency-response test performed on an antagonistic actuation system consisting of two Mckibben pneumatic artificial muscles and a pneumatic circuit with pressure valves. Varying switching frequency to pressure valves from 0.1 Hz to 5 Hz, parameters of a linear model were estimated optimally to predict dynamic characteristics of the antagonistic actuation. A model-base control scheme with estimated parameters was built for the precise trajectory tracking of the antagonistic structure and realized on a reconfigurable embedded control system, CompactRIO. Experimental results showed that the proposed model-based control scheme gave good performance in trajectory tracking comparing with a PD control scheme when square wave and sinusoidal wave were given as references to follow.

Low-Cost Reconfigurable Control System for Small UAVs

A case study of an open-source low-cost reconfigurable autopilot design for small unmanned aerial vehicles (the Remotely operated Aerial Model Autopilot (RAMA) control system) is presented in this paper. A novel distributed hierarchical architecture, implementing graceful degradation and run-time system reconfiguration techniques, is introduced. RAMA is capable of reconfiguration in case of emergency, meaning that the most critical functions, needed for vehicle controllability, can be taken over by another node of the system if the primary node fails, sacrificing some noncritical functionality. RAMA also utilizes a novel control scheme and controller implementation. Some of the results, obtained during several hundred test flights performed so far, are presented at the end.

A reconfigurable control method based on face searching algorithm for aircraft with multiple effectors

This paper presents a reconfigurable flight control method based on face searching allocation algorithm for aircraft with multiple effectors. Besides the function of distributing the desired moments to control surfaces reasonably, face searching method is beneficial for the design of the reconfigurable control system. It can provide the biggest attainable moment subset and provide the maximum moment in any direction. The approach solves different effector failures by the solution of re-allocating the healthy effectors. With the redundancy of remaining effectors, the method can compensate the effects of the failure surfaces and still provide the same desired control input. Simulation results show that reconfigurable control system designed by this method can deal with the different effector failures well.