Partial Loss Of Actuator Effectiveness Research Articles

Resilient anti-disturbance dynamic surface control of uncertain strict-feedback systems subject to partial loss of actuator effectiveness

This paper is concerned with the tracking control of a class of uncertain strict-feedback systems subject to partial loss of actuator effectiveness, in addition to uncertain model dynamics and unknown disturbances. A resilient anti-disturbance dynamic surface control method is proposed to achieve stable tracking regardless of partial actuator faults. First, data-driven adaptive extended state observers are designed based on memory-based identifiers, such that the uncertain model dynamics, external disturbances and the unknown input gains due to actuator faults can be estimated. Next, a resilient anti-disturbance dynamic surface controller is developed based on recovered information from the data-driven adaptive extended state observers. After that, it is proven that the cascade system formed by the observer and controller is input-to-state stable. Finally, comparative studies are performed to validate the efficacy of the resilient anti-disturbance dynamic surface control method for nonlinear strict-feedback systems subject to partial loss of actuator effectiveness.

Collision-avoiding formation for multiple Euler–Lagrange systems against external disturbances and actuator faults

In this paper, for multiple Euler–Lagrange systems embodying external disturbances and unknown uncertainties, the problems of collision-avoiding formation (CAF) are investigated. With regard to Euler–Lagrange systems under healthy actuator condition and under actuator failures, two distributed collision-avoiding formation (DCAF) control laws are proposed. In one case, which the systems are under healthy actuator condition, firstly, a robust continuous term with adaptive variable gain is utilized to reduce the influence of external disturbances under unknown range. In addition, in order to handle the uncertainties of dynamical systems and collision avoidance, both the estimations for uncertain terms and repulsive potential functions are established in design of algorithms. For the other case, the systems under actuator failures, by utilizing the Lyapunov function and relevant adaptive updating laws, the effects subjected to partial loss of actuator effectiveness can be eliminated. Eventually, two distributed algorithms are proposed to achieve the expected formation configuration with no collision occurred. Numerical simulations are conducted to illustrate the validities of the presented control methodologies.

Arttirimli doğrusal olmayan dinamik çevirmeye dayali bir quadrotor'un hata toleransli kontrolü

The multirotor unmanned aerial vehicles (UAVs) have rapidly attracted interest of the researchers since they play a unique role in a variety of areas including the military, agriculture, rescue, and mining. Actuator fault or failure is inevitable during multi-rotor’s operations, which can endanger humans on the ground in addition to costly damage to the system itself. Therefore, this paper introduces a nonlinear controller algorithm for fault-tolerant control of a quadcopter with partial loss of actuator effectiveness. The introduced controller includes a cascade structure of the fast inner-loop dynamics and slow outer-loop dynamics. In the inner-loop part of the controller, an incremental nonlinear dynamic inversion controller is applied and a modified PID control algorithm is used in the outer-loop of the controller. Simulation results for different fault scenarios demonstrate that the proposed fault-tolerant controller approach can quickly adapt itself to the abrupt change due to the motor faults and tracks the desired inputs satisfactorily.

Attitude Compensation Control for Quadrotor Under Partial Loss of Actuator Effectiveness

In this paper, an augmented fault tolerant attitude control system is presented to address the problem of attitude adjustment for a quad-rotor unmanned aerial vehicle with inertia parameter uncertainties, the external disturbance and the partial loss of actuator effectiveness. To tackle system uncertainty and actuator faults, a fixed time compensation controller is developed based on adaptation mechanism combing with a monitor strategy and Nussbaum gain technique. Robust compensation algorithms under the proposed closed loop system structure are derived in the sense of Lyapunov stability analysis such that the attitude tracking-errors converge to a prescribed compact set in a fixed time. Finally, the simulation results demonstrate the effectiveness of the proposed controller.

Adaptive Fault Tolerant Attitude Control of a Nano-Satellite with Three Magnetorquers and One Reaction Wheel

In this paper, a passive fault tolerant attitude control is investigated for a nano-satellite with three magnetorquers and one reaction wheel in the presence of actuator constraints, external disturbances, and partial loss of actuator effectiveness as unknown actuator faults. For this purpose, a variable structure control approach is employed due to its ability to deal with the partial loss of actuator effectiveness and adjusting the maximum amplitude of the control signal by a control gain. A modified sliding variable is designed based on angular velocity and attitude errors with an adaptive parameter coefficient. The dynamics equation of the adaptive parameter is extracted during the stability proof of the closed-loop system. Changing the value of this parameter changes the effect intensity of the quaternion errors on the sliding variable and causes the attitude errors to maintain within a limited range. Applying this parameter to the modified sliding variable makes the controller perform well even if the adaptive parameter is significantly reduced. Furthermore, directly using the adaptive parameter in the structure of control law makes the controller generate a chattering-free torque. Comparing the simulation results with the results of two variable structure control methods designed in previous articles shows that its performance in attitude tracking commands has improved. In addition, Monte Carlo simulations with random actuator faults are performed to show the robustness of the proposed controller in the presence of actuator constraints and external disturbances.

Hypersonic Re-entry Vehicle Fault-Tolerant Control Against Actuator Failure via Integral Sliding Mode

A fault-tolerant control (FTC) scheme is proposed based on integral sliding mode(ISM) for attitude control of hypersonic re-entry vehicle (HRV) under partial loss of actuator effectiveness. First, the inner/outer loop mathematical model of HRV in the present of actuator failure is given with specific analysis on torque. Then prescribed performance approach is introduced to the ISM controller design by error transformation. Specifically, the transformation error rather than tracking error is chosen as the sliding variable to establish the sliding mode surface and reaching law. As a result, the attitude tracking error of HRV is limited into the expected range. Meanwhile, the transient process and the steady state behavior are both considered. Considering that the unknown fault information of actuator can cause adverse effect on HRV, an extended state observer(ESO) is adopted to estimate the unknown actuator failure. Thus the observer result is served as compensation for the loss of the controlled system performance. Simulation results show that the proposed scheme can fulfil the tracking task with prescribed performance.

Fault and Failure Tolerant Model Predictive Control of Quadrotor UAV

This paper presents fault tolerance control (FTC) of a quadrotor under actuator faults. A complete FTC design approach with fault detection and diagnosis (FDD) is addressed. The proposed FTC is based on the model predictive control, which can be applied to nonlinear systems using the so-called successive convexification algorithm, which converts a nonconvex function to a convex function in a successive manner through linearization. The faults are parameterized in the form of loss of effectiveness (LOE) of a quadrotor actuator and estimated using a two-stage Kalman filter. Compared with other FTC, the proposed FTC is capable of controlling not only partial loss of actuator effectiveness defined as a fault but also a complete loss of actuator effectiveness defined as failure. Controller switching is not required, while an actuator saturation limit is also considered. The proposed FTC approach has been validated under various actuator fault conditions through nonlinear simulation studies.

Adaptive fault tolerant control for a small coaxial rotor unmanned aerial vehicles with partial loss of actuator effectiveness

This paper investigates the trajectory tracking problem for a small coaxial-rotor unmanned aerial vehicle (CRUAV) with partial loss of actuator effectiveness. The CRUAV model is decomposed into a dual loop structure based on back-stepping design idea. First, certain performance function specified a priori by the designer is introduced into the position loop such that the original position tracking error is transformed into an equivalent constrained variable providing for the performance judgment of the position loop. Then, a fault-tolerant control scheme is proposed based on adaptive strategies for compensating the effect caused by various adverse factors. Subsequently, an attitude control loop is derived by incorporating adaptive compensation method. It is proved that the proposed dual-loop structure is able to guarantee the satisfaction of the pre-specified constraint on the transformed errors. Finally, the effectiveness and benefits of the design dual-loop control system are validated via computer simulation.

Constrained adaptive fault-tolerant attitude tracking control of rigid spacecraft

A saturated fault-tolerant attitude tracking controller for disturbed rigid spacecraft is derived using nonlinear state feedback control method. The proposed controller achieves the constraints of control inputs by directly using the bounded function instead of the traditional saturation compensator technique, and the active tolerance to the partial loss of actuator effectiveness is also achieved by directly using the known bounds of the actuator faults in the controller. Specifically, compared with the traditional saturated control methods, a continuously bounded nonlinear function in the proposed controller is used to guarantee that the actuator outputs are smoothly bounded under the prescribed constraints. Based on some properties of the attitude tracking dynamics, the proposed controller can ensure the attitude tracking errors converge to small neighborhoods of zero via stability analysis in the Lyapunov framework. Simulation results are presented to illustrate the effectiveness of the control scheme.

Fault tolerant tracking of Mars entry vehicles via fuzzy control approach

In this paper, a fault tolerant attitude tracking control scheme is proposed for Mars entry vehicles (MEVs) with disturbances and actuator failures. The original attitude dynamics of MEVs is divided into two subsystems, named as slow subsystem and fast subsystem, respectively. For slow subsystem, the control-like angular velocity command is generated. For fast subsystem, the Takagi–Sugeno (T-S) fuzzy models are used to describe it at first. Based on these, the partial loss of actuator effectiveness with the generated angular velocity problem is transformed into solving the tracking problem with uncertain parameters. Then, a fault tolerant tracking control scheme is proposed by combining fuzzy line-integral Lyapunov function method with robust H∞ control approach. The proposed controller design is simple and can guarantee the faulty closed-loop system to be stable with acceptable attenuation level. Finally, the effectiveness of the proposed design method is demonstrated in a MEVs attitude control system subject to loss of actuator effectiveness.

Adaptive Distributed Fault-tolerant Formation Control for Multi-robot Systems under Partial Loss of Actuator Effectiveness

This paper presents an adaptive distributed fault-tolerant formation control for multi-robot systems. Both the kinematics and dynamics of differential wheeled mobile robots are considered. In particular, the problem caused by actuator faults is investigated. Based on dynamic surface control techniques, adaptive formation controllers can be obtained under a directed communication network. The closed-loop stability is guaranteed by using Lyapunov stability analysis such that all followers can exponentially converge to a leader-follower formation pattern. Simulation and experimental results illustrate that the desired formation pattern can be preserved for a group of wheeled robots subject to unknown uncertainties and actuator faults.

Adaptive active fault-tolerant MPPT control for wind power generation system under partial loss of actuator effectiveness

In order to improve the dynamic performance and reliability of the maximum power point tracking (MPPT), this paper proposes an adaptive active fault-tolerant control (AFTC) strategy of the wind power generation system to overcome uncertain problems, including potential partial loss of actuator effectiveness, unknown modeling errors and external disturbances. The AFTC method is designed according to a new dynamic model of angular speed tracking for wind power generation system based on generalized perturbation. It neither requires the actuator fault information detection, nor relies on the system model parameters and external disturbance identification. In terms of the on-line estimation of the disturbance boundary amplitude and the nonlinear state feedback based on MPPT tracking error, the gain of the switching control is adaptively adjusted to speed up the convergence of the system and reduce the delay of the fault compensation. A first-order integral process is involved in the AFTC law to further weaken the chattering of output signal amplitude, hence smooth the torque and improve the tracking accuracy during generation. In addition, the global stability of the closed-loop control system based on AFTC is proved by the Lyapunov approach. By comparing with the conventional linear PID control and the nonlinear dynamic state feedback control (NDSFC), the case studies simulation results validate the great MPPT fault-tolerant capability even subject to partial loss of actuator effectiveness, and separately show the strong robustness and self-adaptation of the proposed adaptive AFTC method.

Adaptive Fault-Tolerant Consensus for a Class of Uncertain Nonlinear Second-Order Multi-Agent Systems With Circuit Implementation

In this paper, a robust fault-tolerant consensus control strategy and its circuit implementation method are proposed for a class of nonlinear second-order leader-following multi-agent systems against multiple actuator faults and time-varying state/input-dependent system uncertainties. The faults of partial loss of actuator effectiveness and bias-actuators are considered without knowing eventual faulty information. The uncertainties are supposed to be structured and to satisfy integral quadratic constraints. The nonlinear dynamics of underlying systems are described by linear state-dependent functions based on the differential mean value theorem. By designing adaptive schemes and state-feedback control gains, a novel distributed control strategy is constructed to ensure the asymptotic consensus of agents in the presence of actuator faults, uncertainties, and nonlinear dynamics. The control strategy is further physically implemented based on the circuit theory. The efficiency of the developed control circuits is verified by a multiple coupled nonlinear forced pendulum system based on a circuit simulation software.

Fault-Tolerant Cooperative Motion Planning of Connected and Automated Vehicles at a Signal-Free and Lane-Free Intersection

Compared with a conventional intersection, a signal-free and lane-free intersection enables the vehicles to drive more flexibly, thereby to promote the throughput and to reduce congestions. This work proposes a fault-tolerant cooperative motion planning method for a number of connected and automated vehicles (CAVs) which are passing through a signal-free and lane-free intersection. Partial loss of actuator effectiveness is considered as the fault type. Even a subtle fault may significantly affect the overall team performance. Thus correctly judging whether each faulty/healthy CAV can still achieve its original goal is impossible until a corresponding motion replanning problem turns out to be solvable or not. To maximize the completeness of the original task, we propose a parallel computation framework, wherein the fault-recovery motion replanning problems in multiple levels of task completeness are tried simultaneously. Concretely, i) each faulty/healthy CAV should accomplish its original goal; ii) only each healthy CAV is required to accomplish its original goal; and iii) all the faulty/healthy CAVs try to stop safely without the need to achieve any original goals. Problems iii), ii), and i) are ranking with increasing computational difficulty. Among all the three problems, the achievable solution to the most difficult one is implemented as the fault-recovery strategy.

Adaptive dynamic control allocation for over-actuated dynamic positioning system based on backstepping method in case of thruster faults

The objective of the research considered in this paper is dynamic positioning of a nonlinear over-actuated marine vessel in the presence of limited information about thruster forces. First, the adaptive backstepping method is used to estimate the input matrix which will compensate partial loss of actuator effectiveness in the presence of actuator dynamics. Then, the adaptive commanded virtual forces and moment are allocated into individual thrusters by employing the control allocation algorithm to compensate total faults. The effectiveness of the proposed control scheme is demonstrated by simulations involving a redundant set of actuators, when actuators lose partially their efficiency or failed.

Chattering-Free Sliding Mode Control for Diesel Engine Air Path System with Actuator Faults

In this paper, a chattering-free sliding mode control law is constructed for the diesel engine air path system with consideration of partial loss of actuator effectiveness and additive fault. Firstly, sliding mode method and adaptive technique are employed to develop a fault-tolerant controller. With the adaptation update law, there is no requirement of the priori knowledge of the upper bounds of the actuator faults. Then, to attenuate the chattering behavior and improve system performance, the boundary layer is introduced to modify the sliding mode control method. Rigorous theoretical analysis is presented based on Lyapunov stability theory, which demonstrates that the system trajectories converge to a small neighborhood around the origin. Finally, numerical simulation results are carried out to show the effectiveness and validness of the proposed algorithms.

Adaptive fault tolerant attitude tracking control for miniature rotorcrafts under actuator saturation

The problem of attitude tracking control for a miniature rotorcraft with partial loss of actuator effectiveness is investigated in this paper. By using adaptation mechanism and by combining with Nussbaum gain technique, an adaptive tolerant control strategy capable of attenuating immeasurable disturbances, compensating system parameters uncertainties, and accommodating actuation faults is developed. Then, the rotorcraft attitude system subjected to control constraints is further considered, and a novel fault tolerant controller equipped with auxiliary systems is designed to achieve both attitude tracking and saturation alleviation of control signal. Moreover, fault detection and diagnosis unit are not needed in using and implementing the proposed method. It is proven that attitude errors can asymptotically converge to a small neighborhood of equilibrium point in the face of faulty actuator, model uncertainties, external disturbances and even actuator saturation. Finally, the simulation results demonstrate the effectiveness of the proposed controller.

Adaptive disturbance observer‐based finite‐time continuous fault‐tolerant control for reentry RLV

SummaryThe control effectors of reusable launch vehicle (RLV) can produce significant perturbations and faults in reentry phase. Such a challenge imposes tight requirements to enhance the robustness of vehicle autopilot. Focusing on this problem, a novel finite‐time fault‐tolerant control strategy is proposed for reentry RLV in this paper. The key of this strategy is to design an adaptive‐gain multivariable finite‐time disturbance observer (FDO) to estimate the synthetical perturbation with unknown bounds, which is composed of model uncertainty, external disturbance, and actuator fault considered as the partial loss of actuator effectiveness in this work. Then, combined with the finite‐time high‐order observer and differentiator, a continuous homogeneous second‐order sliding mode controller based on the terminal sliding mode and super‐twisting algorithm is designed to achieve a fast and accurate RLV attitude tracking with chattering attenuation. The main features of the integrated control strategy are that the adaptation algorithm of FDO can achieve non‐overestimating values of the observer gains and the second‐order super‐twisting sliding mode approach can obtain a more elegant solution in finite time. Finally, simulation results of classical RLV (X‐33) are provided to verify the effectiveness and robustness of the proposed fault‐tolerant controller in tracking the guidance commands. Copyright © 2017 John Wiley & Sons, Ltd.

A modified profust-performance-reliability algorithm and its application to dynamic systems

In the field of system health monitoring, system performance degradation or fault occurrence will decrease the system reliability to some degree. However, traditional reliability analysis is of limited usefulness in evaluating the reliability of an individual product under dynamic operating and env ironmental conditions. In this case, research on performance reliability as well as real-time reliability has attracted extensive attentions. Considering the characteristics of fuzzy reliability theory, a performance reliability based on profust reliability theory has its advantage on tracking system’s continuous degradation. On the basis of our previous work, this paper proposes a modified profust-performance-reliability (PPR) algorithm as a supplement to the profust reliability based approach to prognostics and health management. In the modified PPR algorithm, the item of transition probability among system’s multi-states is replaced with the real-time distribution of system’s health status, which achieves an easier implementation of PPR’s calculation in practice with higher real-time capability and accuracy. Then, its application in the performance evaluation and prediction of dynamic systems are comprehensively proposed. Finally, a simulation of a quadrotor with partial loss of actuator effectiveness is presented to validate the availability and effectiveness of the proposed method.

Self-tuned local feedback gain based decentralized fault tolerant control for a class of large-scale nonlinear systems

In this paper, a decentralized fault tolerant control (DFTC) scheme is proposed for a class of large-scale nonlinear systems based on self-tuned local feedback gain against partial loss of actuator effectiveness (PLOAE). Consider a large-scale nonlinear system as a set of interconnected subsystems, a decentralized control method is proposed by employing two radial basis function neural networks (RBFNNs) for the fault-free system. Then, the unknown system is identified using RBFNNs. By establishing a decentralized observer, the derived self-tuned local feedback gain is placed before the proposed decentralized controller to guarantee control performance for the subsystem suffering from PLOAE fault. Finally, simulation examples are provided to demonstrate the effectiveness of the present DFTC scheme. The main contributions of this paper are: i) The unknown large-scale nonlinear system can be identified using locally measured states, so the actuator fault can be handled in its local subsystem. It implies that the performance degradation of the faulty subsystem cannot affect the fault-free subsystems. ii) The estimated effectiveness factor is placed before the proposed decentralized scheme. The fault tolerant control structure is simple since it does not need to be redesigned in the case of PLOAE.