Reconfigurable Control Research Articles

An adaptive law based online system identification of cropped delta unmanned aerial vehicles from flight tests

Online system identification of an aircraft has multifaceted advantages, such as real-time health monitoring, fault detection and reconfiguration of control, to name a few. Researchers have utilized variants of the equation error method, which involves non-gradient-based computation to carry out online system identification, due to its feasibility for real-time implementation. However, it was found to be underperforming while handling high angles of attack as well as time-varying bias parameters. In the current manuscript, an attempt has been made to alleviate the aforementioned limitation by proposing a novel online system identification technique based on adaptive law and its applicability is demonstrated by using compatible flight data sets, acquired from two cropped delta wing unmanned aerial vehicles, pertaining to linear, moderately nonlinear, and near stall flight regimes. It is observed that the proposed method is able to predict unknown aerodynamic derivatives, irrespective of flight envelopes, if dynamic modes are adequately excited. Confidence in the estimated aerodynamic parameters is assured with the two-sigma error bound. It is noticed that the maximum relative standard deviation in the estimates obtained with the proposed method is less than the recursive least squares method and higher than the sequential least squares-recursive Fourier transform method in the linear flight regime. Simulated responses using the estimates obtained from aforementioned methods are compared with measured flight data, and it is witnessed that the simulated nondimensional lift coefficient with the proposed method has a relative offset of less than 34.2% w.r.t measured value in near-stall flight regimes, which is least among all three methods.

Cascade sliding mode control implementation in photovoltaic power supply for camping-car applications

A cascade proportional integral sliding mode control for a two-stage interleaved boost converter (2IBC) serving as a reliable supplementary power source for camping-car applications is reported. Unlike the active fault-tolerant control approaches used for interleaved boost converters, which require controller reconfiguration, the proposed control scheme is passive fault-tolerant and does not require reconfiguration in the event of a faulty stage. The 2IBC model is analyzed together with the most important parasitic parameters, then, the averaged state-space model is derived to implement the control scheme. The appropriate linear cascade control is determined by using the small-signal equivalent model and improving the robustness and dynamic performance, thereby a proportional integrator controller is replaced by a sliding mode controller. The prototype system uses a signal processor and a low-power solar panel. The control code is generated by a PSIM software and loaded to the via a code composer tool. The experimental results validate the control design and demonstrate the efficiency of the proposed control scheme. In addition, the proposed controller ensures the continuity of service in the event of a faulty stage by verifying the reliability of the power supply.

Integrated planning and control for formation reconfiguration of multiple spacecrafts: A predictive behavior control approach

This paper addresses the trajectory planning and control problem of multi-spacecraft formation reconstruction in the presence of obstacles. By expressing spacecraft dynamics relative to a leader spacecraft in the formation, an integrated planning and control approach named predictive null-space-based behavior control (PNSBC) is proposed. First, a planner using null-space-based behavior control (NSBC) is designed at an upper layer to resolve multi-task conflicts. Here, both global tasks, e.g. formation keeping, and local tasks, e.g. obstacle avoidance, are considered. Second, a tracking controller is designed at the bottom layer using decentralized model predictive control. Unlike traditional two-layer approaches that treat planning and control separately, the proposed PNSBC integrates the planning and control in two ways: 1) the planner provides reference trajectories for the controller to track; 2) the model predictive control (MPC) controller provides predicted trajectories that can be employed by the planner for future task priority predictions, which extends the capability of NSBC from one-step planning to multi-step predicting. In addition, the computational burden of the MPC controller is greatly reduced by putting the nonlinear obstacle avoidance constraints into the planner as a local task. Simulation results show that such integrated approach has better performance in terms of safety constraint guarantee, fuel consumption and travel distance when compared against traditional non-integrated approaches, or all-in-one MPC methods, while constraints and task objectives are fully satisfied.

Distributed Fault-Tolerant Formation Tracking Control for Multiagent Systems With Multiple Leaders and Constrained Actuators.

The distributed formation tracking control problem with multiple leaders under actuator faults and constraints is investigated in this article. All followers in the multiagent system should achieve a desired time-varying formation and track the convex combination of multiple leaders. To accomplish the control task, an active reconfigurable control scheme is proposed using the local information between agents, as well as the fault values of individuals provided by fault estimation observers. Combining with the Lyapunov stability theorem and the property of the Laplacian matrix, the control gains are calculated using the adaptive technique with a formation tracking feasibility condition. The original reconfigurable protocol is modified by utilizing anti-windup compensators to against saturation phenomenons (both magnitude and rate) in actuators. The simulation results validate that the presented scheme can address the faults as well as the actuator saturation.

Distributed Adaptive Formation Reconfiguration Control for Multiple AUVs Based on Affine Transformation in Three-Dimensional Ocean Environments

This article addresses the distributed formation reconfiguration control problem for a fleet of nonlinear multiple autonomous underwater vehicles (AUVs) in three-dimensional (3-D) ocean environments. A novel solution to the nonplanar multi-AUV formation reconfiguration control issue is presented by using the graph rigidity and affine transformation (GR-AT) method. Firstly, all AUVs cooperatively achieve a predefined initial cube formation by using the strategy of regulating the inter-AUV distances in a rigid graph. Then the proposed GR-AT method is used to reconstruct the formation shape in multi-obstacle underwater environments. A rigorous Lyapunov stability analysis shows that these distances converge to desired values. The efficiency of the formation reconfiguration control algorithm is confirmed by a series of simulation results. Finally, the corresponding 3-D realistic experiment based on bionic robot fish is carried out to validate the feasibility of the proposed formation control.

Transient Open‐Closed Loop Experimental Validation of a Nonlinear Two‐Phase Flow Distributed System

AbstractThe oil well drilling process is a nonlinear system with transient nature. Conventional drilling is unable to assure safe and cost‐effective operation for fractured, cavernous, and highly permeable carbonate reservoirs, which contain the largest oil reserves worldwide. Concerning drilling technologies, Pressurized Mud Cap Drilling (PMCD) is suitable for the challenging scenario previously mentioned. According to PMCD technique, a sacrificial fluid is injected through the drill string and a light annular mud is pumped in countercurrent through the annulus region (bullheading), without surface return, forcing gas and drilled cuttings back to formation. A two‐phase flow distributed model (Drift Flux Model – DFM) is developed to properly describe the complex nature of the system. Also, an experimental facility, presenting field similarity, is employed to validate the open – closed loop schemes. The main objective of the controller (control reconfiguration with gain scheduling) is to regulate annulus pressure, handling gas kick, drilling fluid losses and inverse response dynamics. Besides, gas injection, migration and bullheading are studied. The simulations, validated through experimental data, highlight the methodology usefulness for field applications.

Reconfiguration control allocation of actuator faults for tailless aircraft with low aspect ratio

The triaxial attitude control of the tailless aircraft depends heavily on the effectiveness of the actuators. Still, the actuators have redundancy characteristics, cross-coupling of rudder effect, and so on. Therefore, the reconfigurable control allocation of the tailless aircraft under typical actuator faults is deeply studied in this paper. The effectiveness and rationality of the incremental control allocation method based on quadratic programming are thoroughly verified for application to maximize the residual control ability of the aircraft, ensure that the aircraft can still complete the flight mission typically, and guarantee flight safety. According to the research principle of surface failures from slight to severe, three typical rudder surface faults are designed successively: Efficiency loss of single actuator, single actuator stuckness, and double actuators combined stuckness. On this basis, the mechanism of reconfiguration allocation after actuator failures is studied, and the residual control ability of the actuator after loss is fully explored. What’s more, the range of allowable reduction of efficiency of each actuator and the acceptable stuck angle range of each actuator are explored, and the most severe failure in the combination of double actuators stuck is obtained. The attitude controller is designed with incremental backstepping (IBKS). The reconstruction allocation adopts a quadratic programming allocation method based on an effective set solver, which can be seamlessly connected with the IBKS method to improve the control accuracy and disturbance immunity effectively.

Nonlinear Fault-Tolerant Vibration Control for Partial Actuator Fault of a Flexible Arm

This paper presents a nonlinear fault-tolerant vibration control system for a flexible arm, considering partial actuator fault. A lightweight flexible arm with lower stiffness will inevitably cause vibration which will impair the performance of the high-precision control system. Therefore, an operator-based robust nonlinear vibration control system is integrated by a double-sided interactive controller actuated by the Shape Memory Alloy (SMA) actuators for the flexible arm. Furthermore, to improve the safety and reliability of the safety-critical application, fault-tolerant dynamics for partial actuator fault are considered as an essential part of the proposed control system. The experimental cases are set to the partial actuator as faulty conditions, and the proposed vibration control scheme has fault-tolerant dynamics which can still effectively stabilize the vibration displacement. The reconfigurable controller improves the fault-tolerant performance by shortening the vibration time and reducing the vibration displacement of the flexible arm. In addition, compared with a PD controller, the proposed nonlinear vibration control has better performance than the traditional controller. The experimental results show that the effectiveness of the proposed method is confirmed. That is, the safety and reliability of the proposed fault-tolerant vibration control are verified even if in the presence of an actuator fault.

Fault Diagnosis and Its Applications to Fault Tolerant Control of a Turbojet Engine

This paper presents a comprehensive study of model-based fault diagnosis (FD) and a fault-tolerant control (FTC) scheme for sensor and actuator faults of turbojet engines. For actuator FD, an unbiased estimation scheme with a modified Kalman filter (KF) was developed. For sensor FD, two approaches, the generalized likelihood ratio with robust KF and the pseudo actuator model with modified KF, were investigated in a comparative study. For fault detection and isolation, test statistics are commonly employed to detect fault behavior. For FTC, integral-type sliding mode control using control reconfiguration and the reconstruction of the sensor signal was adopted with the FD schemes. The effectiveness of the employed methods was demonstrated in this study and discussed with numerical simulations.

Automated design and usage of the Fault-Tolerant dynamic partial reconfiguration controller for FPGAs

This article presents a new design automation method for Fault-Tolerant (FT) systems implemented on dynamically reconfigurable Field Programmable Gate Arrays (FPGAs). The method aims at minimizing the human interactions needed to incorporate FT mechanisms into an existing system. It starts with a source code of an original unhardened circuit. It continues by automated manipulation of the source code, algorithmic strategic selection of suitable FT techniques, design space exploration of candidate FT implementations, and selection of the resulting implementation. The method also includes efficient evaluation of achieved FT parameters performed on the target HW. As a novel approach working on the level of HW description languages is employed, the code modification is separated, which differentiates our method from others. The case study utilizing this method targets the design of an experimental FT dynamic partial reconfiguration controller for an FPGA. This controller is helpful for the restoration of faulty components due to a single-event upset on an FPGA. We used the method to generate a set of Pareto-optimal controllers concerning the design’s Mean Time to Failure (MTTF) parameter, power consumption, and size. Then, the FT controller is connected to several benchmark circuits, and the reliability parameters are evaluated at the entire system level. Our results show that by replacing the standard reconfigurable controller with our automatically-designed FT controller for one specific benchmark, the design size increased by 20.1%, and MTTF increased by 11.7%. However, the efficiency is highly dependent on the target system size, MTTF, and circuit functionality. We also estimate that a complex system defined by half a million configuration bits would improve MTTF by more than 50%.

Robust control scheme based on an uncertainty and disturbance estimator for a quadrotor with motor failures

AbstractThis paper proposes a new robust fault tolerant control architecture based on a disturbance observer. The control architecture is composed of a nominal controller and a rotor's fault observer capable to identify and estimate motors' degradation performance. Besides, is designed for a quadrotor vehicle and validated in critical and noncritical motors' failures. For both failure cases, each motor performance is analyzed to counteracted the failure and restore the system stability. If the practical stability is not recovered (critical case) a control reconfiguration is performed for safe landing. Experimental tests are carried out in real time to illustrate the effectiveness of the proposed architecture when confronting the stability of the system with aggressive disturbances or uncertainties.

Cyber-Resilient Control of an Islanded Microgrid Under Latency Attacks and Random DoS Attacks

The information exchange among distributed energy resources (DERs) in microgrids (MGs) is through sensing and communication systems, which are prone to expose cyber-attack threats. This article investigates the stability issue of MG systems with distributed secondary control under latency attacks and random denial-of-service (DoS) attacks. Considering these two kinds of attack modes, the corresponding attack consequences including network jamming and time-varying latency in the communication network are simultaneously studied. First, a new metric is defined to quantify the DoS attacks by considering different network jamming choices. Then, the time-domain stability study is conducted considering both attack consequences. Next, a cyber-resilient control strategy is proposed with two control modes: 1) An adaptive-gain resilient controller to sustain the fast stabilization of MG systems under nonuniform time-varying latency attacks, which is proved by the stochastic stability analysis using Lyapunov–Krasovskii functional method. 2) An event-trigger topology reconfiguration controller against excessive latency and damaged cyber connectivity caused by DoS attacks. A switching mechanism for coordinating the above control modes is also designed to guarantee the secondary control functions of MG systems. A modified IEEE 13-bus MG system with five DERs is tested and the effectiveness of the proposed controller under different attack scenarios is verified by OPAL-RT real-time tests.

Self-Adaptive Obstacle Crossing of an AntiBot From Reconfiguration Control and Mechanical Adaptation

AbstractOne drawback of wheeled robots is their inferiority to conquer large obstacles and perform well on complicated terrains, which limits their application in rescue missions. To provide a solution to this issue, an ant-like six-wheeled reconfigurable robot, called AntiBot, is proposed in this paper. The AntiBot has a Sarrus reconfiguration body, a three-rocker-leg passive suspension, and mechanical adaptable obstacle-climbing wheeled legs. In this paper, we demonstrate through simulations and experiments that this robot can change the position of its center of mass actively to improve its obstacle-crossing capability. The geometric and static stability conditions for obstacle crossing of the robot are derived and formulated, and numerical simulations are conducted to find the feasible region of the robot’s configuration in obstacle crossing. In addition, a self-adaptive obstacle-crossing algorithm is proposed to improve the robot’s obstacle-crossing performance. A physical prototype is developed, and using it, a series of experiments are carried out to verify the effectiveness of the proposed self-adaptive obstacle-crossing algorithm.

Fault-Tolerant Attitude Control Incorporating Reconfiguration Control Allocation for Supersonic Tailless Aircraft

This paper presents a fault-tolerant attitude control scheme, incorporating reconfiguration control allocation for supersonic tailless aircraft subject to nonlinear characteristics, actuator constraint, uncertainty, and actuator faults. The main idea is to propose an incremental reconfiguration closed-loop control allocation scheme, coupled with a basic backstepping attitude controller, to achieve attitude control. Based on the virtual control input generated by the basic backstepping attitude controller, firstly, the incremental nonlinear control allocation method is adopted to deal with the nonlinear characteristics and actuator constraint. Secondly, a distribution error feedback loop is constructed in the incremental nonlinear control allocation method to enhance the robustness against the uncertainty of the control effectiveness matrix. Thirdly, the control effectiveness matrix is reconstructed by different kinds of fault information to deal with actuator faults, and the proper combination of actuator deflections is generated to achieve accurate command tracking. The stability of the proposed scheme is guaranteed by the Jury stability criterion and the Lyapunov stability analysis. Finally, in comparison with the three existing approaches, the simulation results of two cases are provided to show the effectiveness of the proposed scheme.

A Fault-Tolerant and Reconfigurable Control Framework: Modeling, Design, and Synthesis

Manufacturing systems (MS) have become increasingly complex due to constraints induced by a changing environment, such as flexibility, availability, competition, and key performance indicators. This change has led to a need for flexible systems capable of adapting to production changes while meeting productivity and quality criteria and reducing the risk of failures. This paper provides a methodology for designing reconfigurable and fault-tolerant control for implementation in a Programmable Logic Controller (PLC). The main contribution of this methodology is based on a safe control synthesis founded on timed properties. If a sensor fault is detected, the controller switches from normal behavior to a degraded one, where timed information replaces the information lost from the faulty sensor. Switching between normal and degraded behaviors is ensured through reconfiguration rules. The primary objective of this method is to implement the obtained control into a PLC. In order to achieve this goal, a method is proposed to translate the controllers of the two behaving modes and the reconfiguration rules into different Grafcets. This approach relies on the modular architecture of manufacturing systems to avoid the combinatorial explosion that occurs in several approaches.

IEC 62264 standard-based manufacturing operations management resource modelling for electron beam welding

The development and deployment of a Manufacturing Operations Management (MOM) system for electron beam welding aims the integration and organization of the accumulated knowledge for the process, and the application of this knowledge for the improvement of the modelling and control capabilities, their efficiency, adaptability, flexibility and re-configurability, as well as integration with other technological processes. The paper presents the Unified Modelling Language (UML) information modelling of electron beam welding installation as a part of an IEC 62264 standard-based manufacturing operations management system development.

Distribution network reconfiguration control and protection method based on multi-source data interaction

Distribution network reconfiguration technology is the key technology of distribution network fault treatment and power supply recovery. Given the problem that the traditional distribution network reconfiguration algorithm needs a lot of power flow calculation and low efficiency to find the optimal target, the simulated annealing algorithm is proposed to optimize the computing speed and searching ability of the distribution network reconfiguration algorithm. Firstly, the information interaction technology of distribution network protection and control equipment is studied, and the real-time data rapid peer-to-peer exchange and data and information interaction model is built, which improves the fault detection and timely removal ability of the distribution network. Secondly, the simulated annealing algorithm is used to reduce the number of power flow calculations, reduce the calculation time, improve the calculation speed of network reconstruction problems, and ensure that the optimal or better network topology can be obtained. Finally, the simulation analysis of the IEEE37 node system verifies the effectiveness of the proposed reconfiguration protection method in a complex environment with massive access to distributed energy.

Adaptive fault-tolerant control for electro-hydraulic servo actuator based on multiple unmodeled dynamics estimation and compensation

The internal leakage fault-tolerant control problem of the electro-hydraulic servo actuator under the influence of multiple unmodeled dynamics is investigated in this paper, and an adaptive fault-tolerant control scheme based on unmodeled dynamics estimation and compensation is proposed. The model of the actuator is divided into two subsystems, which extended-state observers are respectively constructed to estimate the matched and mismatched unmodeled dynamics. Combined with the estimation results of the unmodeled dynamics, an adaptive fault-tolerant controller is designed by using the backstepping method. In which a controller reconfiguration mechanism based on internal leakage fault parameter online adaptation is used to accommodate the fault, and a feedforward compensation strategy is used to suppress the influence of unmodeled dynamics. Semi-physical simulation test of the proposed scheme is conducted under serious cylinder internal leakage. The test result shows that when the maximum internal leakage flow reaches 10.53 L/min, accounting for about 56.77% of the load flow, at the moment the opening of the servovalve is close to the maximum and the proposed scheme can still achieve high-precision position tracking control, where the maximum position tracking errors of fault transient and post-fault steady state are both limited within ±1.5% of the given position.

The multi-AUV time-varying formation reconfiguration control based on rigid-graph theory and affine transformation

This paper studies the time-varying formation reconfiguration control for multiple underactuated autonomous underwater vehicles (AUVs) with an Euler–Lagrange-like model. The goal is to control a fleet of AUVs to achieve any desired formation shape using a distance-based graph rigidity and affine transformation (GR-AT) algorithm. Firstly, the distance-based graph rigidity with backstepping technology is utilized to solve the formation controlproblem, and we acquire the initial nominal formation. In the sequel, we transform the nominal formation into any desired formation shape using the properties of the affine transformation (including translation, scaling, rotation, shearing, or a combination of them). Even the geometric shapes formed can be constantly changed. The Lyapunov stability theory can ensure the uniform ultimate boundedness of whole distance errors. Finally, several simulation examples with formation reconfiguration are given to validate the efficacy of the designed control methods. Moreover, some experimental results are presented to confirm the validity and applicability of the scheme with four real bionic robot fish.

Disturbance observer-based performance guaranteed fault-tolerant control for multi-spacecraft formation reconfiguration with collision avoidance

In this study, the issue of the performance guaranteed fault-tolerant control for formation reconfiguration with collision avoidance in the multi-spacecraft system subjects to space perturbations and thruster faults is investigated. A new nonlinear iterative learning disturbance observer is constructed to accurately reconstruct the synthesized disturbance no matter it is time-varying or not. Then, an exponential artificial potential function with a simple structure and low computation requirement is designed to avoid collision between spacecrafts. A nonsingular terminal sliding mode fault-tolerant control method is explored to accomplish fault-tolerant formation reconfiguration with collision avoidance ability and prescribed robust performance. Finally, numerical simulations and comparisons are performed to validate the effectiveness and superiority of the proposed approaches.