Control Actuator Failures Research Articles

Fault-Tolerant Terminal Sliding Mode Control with Disturbance Observer for Vibration Suppression in Non-Local Strain Gradient Nano-Beams

This research investigates the stabilization and control of an uncertain Euler–Bernoulli nano-beam with fixed ends. The governing partial differential equations of motion for the nano-beam are derived using Hamilton’s principle and the non-local strain gradient theory. The Galerkin method is then applied to transform the resulting dimensionless partial differential equation into a nonlinear ordinary differential equation. A novel fault-tolerant terminal sliding mode control technique is proposed to address the uncertainties inherent in micro/nano-systems and the potential for faults and failures in control actuators. The proposed controller includes a finite time estimator, the stability of which and the convergence of the error dynamics are established using the Lyapunov theorem. The significance of this study lies in its application to the field of micro/nano-mechanics, where the precise control and stabilization of small-scale systems is crucial for the development of advanced technologies such as nano-robotics and micro-electromechanical systems (MEMS). The proposed control technique addresses the inherent uncertainties and potential for faults in these systems, making it a valuable choice for practical applications. The simulation results are presented to demonstrate the effectiveness of the proposed control scheme and the high accuracy of the estimation algorithm.

Design of a multi-vectored thrust aerostat with a reconfigurable control system

This paper presents an aerostat developed in the shape of an ellipsoid, which is a cross between a ball and a water droplet. This aerostat is equipped with four vectored thrusters. Its coefficient of forward drag is smaller than that of the spherical aerostat, and its lift efficiency is higher than that of the conventional airship. To allocate control among the multi-vectored thrusters, a control system based on pseudo-inverse dynamics is designed. A reconfiguration strategy is also proposed to reallocate actuators in case of control actuator failure. Three diagonal weight matrices are combined to represent all possible failure situations occurred on vectored thruster, they make the reconfigurable controller more general. Based on simulation results under different fault situations, the reconfigurable control system performs more effectively than a normal control system in cases of actuator failure, even when more than one actuator fails. Reconfigurable ability of controller also validated in real flight experiment.

Fault tolerant autonomous rendezvous and docking architecture for spacecraft in presence of control actuator failures

PurposeThe purpose of this paper is to present novel robust fault tolerant control design architecture to detect and isolate spacecraft attitude control actuators and reconfigure to redundant backups to improve the practicality of actuator fault detection.Design/methodology/approachThe Robust Fault Tolerant Control is designed for spacecraft Autonomous Rendezvous and Docking (AR&D) using Lyapunov direct approach applied to non‐linear model. An extended Kalman observer is used to accurately estimate the state of the attitude control actuators. Actuators on all three axes (roll/pitch/yaw) sequentially fail one after another and the robust fault tolerant controller acts to reconfigure to redundant backups to stabilize the spacecrafts and complete the required maneuver.FindingsIn the simulations, the roll, pitch and yaw dynamics of the spacecraft are considered and the attitude control actuators failures are detected and isolated. Furthermore, by switching to redundant backups, the guarantee of overall stability performance is demonstrated.Research limitations/implicationsA real time actuator failure detection and reconfiguration process using robust fault tolerant control is applied for spacecraft AR&D maneuvers. Finding an appropriate Lyapunov function for the non‐linear dynamics is not easy and always challenging. Failure of actuators on all three axes at the same time is not considered. It is a very useful approach to solve self‐assembly problems in space, spacecraft proximity maneuvers as well as co‐operative control of planetary vehicles in presence of actuator failures.Originality/valueAn approach has been proposed to detect, isolate and reconfigure spacecraft actuator failures occurred in the spacecraft attitude control system. A Robust Fault Tolerant Control scheme has been developed for the nonlinear AR&D maneuver for two spacecrafts. Failures that affect the control performance characteristics are considered and overall performance is guaranteed even in presence of control actuator failures. The architecture is demonstrated through model‐based simulation.

Fault detection and accommodation via neural network and variable structure control

This paper proposes a novel idea that classifies faults into two different kinds: serious faults and small faults, and treats them with different strategies respectively. A kind of artificial neural network (ANN) is proposed for detecting serious faults, and variable structure (VS) model-following control is constructed for accommodating small faults. The proposed framework takes both advantages of qualitative way and quantitative way of fault detection and accommodation. Moreover, the uncertainty case is investigated and the VS controller is modified. Simulation results of a remotely piloted aircraft with control actuator failures illustrate the performance of the developed algorithm.

Integrated fault‐detection and fault‐tolerant control of process systems

AbstractThe problem of implementing fault‐tolerant control to nonlinear processes with input constraints subject to control actuator failures is considered, and an approach predicated upon the idea of integrating fault‐detection, feedback and supervisory control is presented and demonstrated. To illustrate the main idea behind the proposed approach, availability of measurements of all the process state variables is initially assumed. For the processes under consideration, a family of candidate control configurations, characterized by different manipulated inputs, is first identified. For each control configuration, a Lyapunov‐based controller that enforces asymptotic closed‐loop stability in the presence of constraints, is designed, and the constrained stability region, associated with it, is explicitly characterized. A fault‐detection filter is used to compute the expected closed‐loop behavior in the absence of faults. Deviations of the process states from the expected closed‐loop behavior are used to detect faults. A switching policy is then derived, on the basis of the stability regions, to orchestrate the activation/deactivation of the constituent control configurations in a way that guarantees closed‐loop stability in the event that a failure is detected. Often, in chemical process applications, not all state variables are available for measurement. To deal with the problem of lack of process state measurements, a nonlinear observer is designed to generate estimates of the states, which are then used to implement the state feedback controller and the fault‐detection filter. A switching policy is then derived to orchestrate the activation/deactivation of the constituent control configurations in a way that accounts for the estimation error. Finally, simulation studies are presented to demonstrate the implementation and evaluate the effectiveness of the proposed fault‐tolerant control scheme, as well as to investigate an application in the presence of uncertainty and measurement noise. © 2006 American Institute of Chemical Engineers AIChE J, 2006

Multiple-model adaptive estimation using a residual correlation Kalman filter bank

We propose a modified multiple model adaptive estimation (MMAE) algorithm that uses the time correlation of the Kalman filter residuals, in place of their scaled magnitude, to assign conditional probabilities for each of the modeled hypotheses. This modified algorithm, denoted the residual correlation Kalman filter bank (RCKFB), uses the magnitude of an estimate of the correlation of the residual with a slightly modified version of the usual MMAE hypothesis testing algorithm to assign the conditional probabilities to the various hypotheses that are modeled in the Kalman filter bank within the MMAE. This concept is used to detect flight control actuator failures, where the existence of a single frequency sinusoid (which is highly time correlated) in the residual of an elemental filter within an MMAE is indicative of that filter having the wrong actuator failure status hypothesis. This technique results in a delay in detecting the flight control actuator failure because several samples of the residual must be collected before the residual correlation can be estimated. However, it allows a significant reduction of the amplitude of the required system inputs for exciting the various system modes to enhance identifiability, to the point where they may possibly be subliminal, so as not to be objectionable to the pilot and passengers.

Multivariable-control-system design concepts in failure analysis of a class of nuclear-reactor spatial-control systems

Given a symmetrical sector-control configuration for the control of the azimuthal modes of a cylindrical nuclear-power reactor and a feedback-control design which produces the required stability and transient responses of each of the dominant spatial modes of that system, the problem of system reliability, in the sense of stability with respect to sensor or control-actuator failure in any one sector, must be investigated. This paper derives a simple relationship between transfer-function elements of the multivariable closed-loop system and the reliability of that system with respect to a class of failures which can be represented by a zero transmission path in one of the loops, together with some known system input. For example, a jammed control rod no longer has any effect on the dynamics of the system, but will introduce static effects. The use of the relationship as a constraint in the final closed-loop design is discussed by reference to an example.