Actuator Gain Fault Research Articles

Adaptive Neural-Network-Based Fault-Tolerant Control for a Flexible String With Composite Disturbance Observer and Input Constraints

We propose an adaptive neural-network-based fault-tolerant control scheme for a flexible string considering the input constraint, actuator gain fault, and external disturbances. First, we utilize a radial basis function neural network to compensate for the actuator gain fault. In addition, an observer is used to handle composite disturbances, including unknown approximation errors and boundary disturbances. Then, an auxiliary system eliminates the effect of the input constraint. By integrating the composite disturbance observer and auxiliary system, adaptive fault-tolerant boundary control is achieved for an uncertain flexible string. Under rigorous Lyapunov stability analysis, the vibration scope of the flexible string is guaranteed to remain within a small compact set. Numerical simulations verify the high control performance of the proposed control scheme.

Fault-Tolerant Control of Multi-Joint Robot Based on Fractional-Order Sliding Mode

In this paper, the problem of fault-tolerant control of actuators for multi-joint robots is studied. Aiming at the jitter problem in the design of fault-tolerant control law for conventional sliding mode controllers (SMC), a controller design method based on fractional-order sliding mode (FSMC) theory is proposed. At first, the mathematical model of the multi-joint robot is established and the fractional-order sliding mode surface is constructed according to the mathematical model. Then, the robust control law is designed based on the Lyapunov function. Finally, the experiments are carried out. Compared with the conventional sliding mode control, the experimental results show that the multi-joint robot is more stable under the control of fractional-order sliding mode, and it can achieve almost no jitter while tracking the reference. The steady-state error for joint1 and joint2 could reach 0.073 radians under the control of SMC, while it is 0.015 radians under the control of FSMC. The steady-state error data indicate that the fluctuation amplitude under FSMC is five times smaller than SMC for the end part of the multi-joint robot under actuator gain faults. The regulation time for joint1 and joint2 is about 0.11 s under the control of SMC, and it is around 0.04 s for FSMC. The regulation time is reduced to one of three or four. These data show the effectiveness of the FSMC proposed in this paper.

Adaptive Fuzzy Control for an Uncertain Axially Moving Slung-Load Cable System of a Hovering Helicopter With Actuator Fault

This study addresses adaptive fuzzy control for an axially moving slung-load cable system (AMSLCS) of a helicopter in the presence of an actuator fault, system uncertainty, and disturbances with the aid of a fuzzy logic system (FLS). The actuator fault considered is depicted by a more general faulty plant that includes an unknown actuator gain fault and a fault deviation vector. First, to compensate for system uncertainty and the fault deviation vector, a fuzzy control technique is adopted. Then, under the introduced FLS, a novel adaptive fuzzy control law is developed by employing a rigorous Lyapunov derivation. The closed-loop system of the AMSLCS is proved to be uniformly bounded even when considering the actuator fault, system uncertainty, and disturbances. Finally, a simulation is executed to expound the performance of the developed controller.

Observer-based adaptive sliding mode fault-tolerant control for the underactuated space robot with joint actuator gain faults

An adaptive sliding mode fault-tolerant controller based on fault observer is proposed for the space robots with joint actuator gain faults. Firstly, the dynamic model of the underactuated space robot is deduced combining conservation law of linear momentum with Lagrange method. Then, the dynamic model of the manipulator joints is obtained by using the mathematical operation of the block matrices, hence the measurement of the angular acceleration of the base attitude can be omitted. Subsequently, a fault observer which can accurately estimate the gain faults is designed, and the estimated results are fed back to the adaptive sliding mode fault-tolerant controller. It is proved that the proposed control algorithm can guarantee the global asymptotic stability of the closed-loop system through the Lyapunov theorem. The simulation results authenticate the effectiveness and feasibility of the control strategy and observation scheme.

Active fault tolerance control for active suspension with control input time-delay and actuator gain variation fault

An active suspension system (ASS) subject to control input time-delay and actuator gain fault is considered in this paper. The system dynamics models with time-delay and gain fault are built. A sliding-mode controller is designed to maintain the stability for the time-delay system. By employing a robust observer and residue errors, the gain fault is detected and diagnosed. The control law reconfiguration is adopted to realise the active fault tolerance control. The act-and-wait control is applied for the active suspension nonlinear system. Comparative simulation results for a quarter-car ASS are presented to show the effectiveness of the adopted control scheme.

Fuzzy adaptive fault tolerant IGC method for STT missiles with time-varying actuator faults and multisource uncertainties

This paper studies the integrated guidance and control (IGC) problem for a class of skid-to-turn (STT) missiles subjected to rapidly changing actuator failures and coupled multisource uncertainties. Meanwhile, during interception, the target is allowed to possess unknown and changeable maneuver accelerations. By analyzing the dominating factors in the IGC system, a nonlinear uncertain strict-feedback system suffering from matched and mismatched uncertainties is utilized to describe the IGC dynamics. Furthermore, for each subsystem, the control gain functions and their boundaries are assumed unknown, which make it difficult to design the controllers. By using a hyperbolic tangent function and estimating the bounds of the lumped disturbances, the time-varying multisource uncertainties can be handled. To compensate the unknown nonlinearities existing in the IGC system, several fuzzy logic systems are established. Furthermore, a number of reciprocal adaptive laws are developed such that unwanted effects caused by the unknown control gain functions and changing actuator gain faults can be surmounted. As a result, a novel fault tolerant IGC structure is constructed and satisfactory hit-to-kill interception performance can be obtained. Finally, the numerical simulations are provided to verify the validity and advantage of the proposed method.

2D Fuzzy Constrained Fault-Tolerant Predictive Control of Nonlinear Batch Processes

Concerning actuator gain faults and strong system nonlinearity in batch processes, a design method of a kind of 2D fuzzy constrained model fault-tolerant predictive controller is proposed. Firstly, introduce two errors: state error and output error, after that the original system model is converted into a 2D Roesser fault model. Meanwhile, the design of iterative learning fault tolerant control under constraints has been transformed into the determination of the constrained update law. Subsequently, real-time on-line design of the fuzzy fault-tolerant update law that ensures the closed-loop system robustly asymptotic stability is presented by taking the appearance of linear matrix inequalities (LMIs) with constraint subject to the designed infinite optimization performance index and Lyapunov stability theory. Finally, taking a three-tank case as an example to compare with the 1D of the method proposed in this paper, the comparison results illustrated the 2D method of this paper has better control effects.

Robust adaptive fault tolerant attitude control for post-capture non-cooperative targets with actuator nonlinearities

This paper develops an attitude takeover control structure for post-capture non-cooperative targets with actuator nonlinearities and faults. In this paper, the contingent actuator gain faults, deviation faults and the undesirable non-symmetric dead-zone nonlinearities of the actuator are all under consideration. An effective robust adaptive fault tolerant attitude control method is synthesized such that the actuator nonlinearities and faults can be well handled. As a result, the accurate attitude stabilization and tracking are maintained. Moreover, an extended fault tolerant attitude control scheme that can work well in the presence of inaccurate measurement information is proposed. Based on a quadratic Lyapunov function, the proof of the convergence is completed. Simulation results demonstrate the effectiveness and advantages of the proposed method.

Adaptive fault detection and estimation scheme for a class of uncertain nonlinear systems

This paper presents a novel fault detection and estimation (FDE) scheme for a class of Lipschitz nonlinear systems subjected to modeling and measurement uncertainties. Many works in this field assume that the states of the system are measurable and the fault function acts as an additive term. The proposed FDE strategy deals with the uncertain nonlinear systems subjected to multiplicative faults, and it does not rely on availability of the full state. Multiplicative fault corresponds to the parameter or structure changes in the system or in the process model. Also, actuator gain fault is another important fault type which can be modeled as a multiplicative fault. The effects of this kind of fault are combined with the inputs and outputs of the system in a multiplicative form which, in turn, make the detection and estimation of the fault complex. The proposed scheme is based on an adaptive diagnostic observer that not only can estimate the states of the system and generate the residual signal simultaneously, but also is able to estimate the characteristic and magnitude of an unknown fault. In the fault detection step, the threshold is derived analytically to ensure the robustness of the proposed detection scheme against uncertainties. Also in the fault estimation step, a robust adaptive law based on the switching $$\sigma $$ -modification is developed to estimate the detected fault accurately. Design steps of the proposed estimation scheme are introduced in the form of LMI problem. This formulation provides an effective way to calculate the design parameters. The proposed FDE scheme guarantees that all signals are uniformly ultimately bounded. Simulation results of a single-link, flexible joint, robotic arm show the effectiveness and robustness of the proposed FDE strategy.

Adaptive fault‐tolerant backstepping control against actuator gain faults and its applications to an aircraft longitudinal motion dynamics

SUMMARYThe problem of fault‐tolerant control (FTC) for a class of uncertain nonlinear systems with actuator faults is discussed, and an observer‐based FTC scheme is proposed. Adaptive fuzzy observers are designed to provide a bank of residuals for fault detection and isolation. Using a backstepping approach, we proposed a novel fault diagnosis algorithm, which removes the classical assumption that the time derivative of the output error should be known. Further, an accommodation scheme is proposed to compensate for the effect of the fault, where it is not needed to know the bounds of the time derivative of the fault. The proposed controller guarantees that all signals of the closed‐loop system are semi‐globally uniformly ultimately bounded and converge to a small neighborhood of the origin by appropriately choosing designed parameters. In addition, a sufficient condition for the existence of an fault detection and isolation observer is derived using Lyapunov stability theory. Finally, a numerical example and a practical aircraft longitudinal motion dynamics are used to demonstrate the effectiveness of the proposed FTC approach. Copyright © 2013 John Wiley & Sons, Ltd.

ROBUST FAULT DETECTION AND ISOLATION FOR UNCERTAIN LINEAR RETARDED SYSTEMS

ABSTRACTA robust fault detection and isolation scheme is proposed for uncertain continuous linear systems with discrete state delays for both additive and multiplicative faults. Model uncertainties, disturbances and noises are represented as unstructured unknown inputs. The proposed scheme consists of a Luenberger observer for fault detection and a group of adaptive observers, one for each class of faults, for fault isolation. The threshold determination and fault isolation are based on a multi‐observer strategy. Robustness to model uncertainties and disturbances can be guaranteed for the scheme by selecting proper thresholds. All the signals, i.e., the fault estimate and the state and output estimation errors of each isolation observer can be shown to be uniformly bounded, and the estimate of the fault by the matched observer is shown to be satisfactory in the sense of extended H2 norm. Furthermore, the sensitivity to fault and the fault isolability condition are analyzed also in the paper. Simulations of a heating process for detecting and isolating an actuator gain fault and an additive fault show the proposed scheme is effective.