Actuator Disturbances Research Articles

Robust Adaptive Fault Reconfiguration for Micro-gas Turbine Based on Optimized T–S Fuzzy Model and Nonsingular TSMO

This paper presents a novel robust fault reconfiguration scheme based on optimized Takagi–Sugeno (T–S) fuzzy model and nonsingular terminal sliding mode observer (NTSMO) with adaptive law for micro-gas turbine (MGS). An optimized T–S fuzzy model is introduced because it can approximate any nonlinear model with arbitrary precision, and an improved imperial competition algorithm (ICA) using adaptive reform probability is proposed to improve the accuracy of the model. A linear transformation method is introduced to decouple the fault and disturbance of the system. The nonsingular terminal sliding mode observer is designed to reconstruct actuator fault and disturbance with unknown upper bound of a change rate, in which an adaptive law is introduced to update the sliding mode gain in real-time to eliminate the influence of fault, disturbance and modeling uncertainty. Simulations in Matlab/Simulink show high reconfiguration accuracy and high-speed of the proposed method despite of the presence of fault, disturbance and modeling uncertainty.

Dissipative PI control for a class of semilinear heat equations with actuator disturbance

The problem of dissipative proportional-integral (PI) output-feedback control for a class of semilinear heat equations with actuator disturbance is addressed. Sufficient conditions for strict dissipativity in the state and thus exponential stability of the closed-loop system are derived which are stated in terms of the dissipavity properties of the nonlinearity, the controller gains and the actuator and sensor shape functions (i.e., their form and localization). Based on these conditions a dissipation maximization procedure is proposed to appropriately choose the degrees of freedom using optimization algorithms. Numerical simulation results illustrate the performance of the proposed controller.

Exponential input-to-state stability of globally Lipschitz time-delay systems under sampled-data noisy output feedback and actuation disturbances

In this paper we deal with the problem of global exponential practical stability preservation for globally Lipschitz time-delay systems, by Euler emulation of continuous-time dynamic output feedback controllers affected by measurement noises and actuation disturbances. Nonlinear time-delay systems not necessarily affine in the control input are studied. It is shown that, if the continuous-time closed-loop system at hand is globally exponentially stable and the maps describing the plant and the continuous-time dynamic output feedback controller are globally Lipschitz, then, under suitably fast sampling, the Euler emulation of the continuous-time controller at hand preserves the global exponential stability of the sampled-data closed-loop system (no matter whether periodic or aperiodic sampling is used). In the case of bounded measurement noises and bounded actuation disturbances affecting the control law, it is proved that, under suitable fast sampling, (global) exponential input-to-state stability with respect to both these external inputs is guaranteed. A generalisation of the Halanay's inequality is used as a tool in order to prove the results. The existence of a Lyapunov-Krasovskii functional for the continuous-time closed-loop system is sufficient to ensure the preservation of the global exponential practical stability. On the other hand, the explicit knowledge of a Lyapunov-Krasovskii functional allows us to compute an upper bound for the sampling period. An example is presented which validates the theoretical results.

Sliding mode observer design for fault and disturbance estimation using Takagi-Sugeno model

Abstract This paper presents an actuator fault and disturbance estimation scheme using sliding mode observer (SMO) based on Takagi–Sugeno (TS) fuzzy system model. The TS model is first transformed in order to decouple disturbance and faults. Then a TS fuzzy SMO is developed for the transformed system. Finally, the disturbance and the fault are estimated using equivalent output error. The stability of the proposed observer is analyzed and its performances are tested for a doubly fed induction generator with actuator fault and disturbance.

Adaptive super-twisting sliding mode control of 6-DOF nonlinear and uncertain air vehicle

In this paper, to control the six degree-of-freedom non-linear unmanned aerial vehicle, two strategies are implemented using adaptive super-twisting sliding mode control approach. The first one is a single-channel controller that is designed on the basis of decoupled equations of motion. The other one is a three-channel controller that is designed based on the coupling equations of motion along with an adaptive super-twisting observer. The stability of the closed loop system of the controller-observer is proven. The comparison between the single-channel controller and the three-channel could lead us to select between a little lower efficiency and less complexity versus efficiency and more complexity. To examine the performance and robustness of these two control loops, their performances are analyzed in the presence of combined uncertainties, including aerodynamics, mass, inertial moment, sensor, and actuator disturbances and parametric uncertainties in the stage separation phase. The explosive bolt separation mechanism is assumed to perform the stage separation, and its forces, moments and disturbances are modeled as needed. Finally, the responses are compared with the classic PID controller.

Active control of large-amplitude vibration of a membrane structure

This paper studies active control of large-amplitude vibration of a membrane structure with piezoelectric actuators. First, dynamic equation of large-amplitude vibration of the membrane structure is established based on the von Karman’s large deformation assumption. Next, a four-mode nonlinear model is obtained by applying Galerkin decomposition to the nonlinear dynamic equation. Then, a model reference adaptive controller is designed to suppress the large-amplitude vibration of the membrane structure, and the stability of the controller is proven by Lyapunov’s stability theory. Finally, numerical simulations are carried out to verify the validity of the studies in this paper. Simulation results indicate that the model reference adaptive controller given in this paper can suppress the large-amplitude vibration of the membrane structure effectively; this adaptive controller is robust to modeling errors, and it is also more robust than the classical velocity feedback controller in the presence of actuator disturbance and sensor disturbance.

Higher order sliding mode control for active suspension systems subject to actuator faults and disturbances

As the possibility of faults in active suspension actuators are higher and more severe compared to other components, this study presents a fault-tolerant control approach based on the second-order sliding mode control method. The aim of the controller is to improve riding comfort, guarantee handling stability, and provide adequate suspension stroke in the presence of disturbances and actuator faults. A nonlinear full-vehicle suspension system and hydraulic actuator with nonlinear characteristics are adopted for accurate control. Firstly, a nonlinear sliding manifold based on a nonsingular fast terminal sliding mode controller is introduced to suppress the sprung mass heave, pitch, and roll motions arising from road disturbances. Secondly, a second-order sliding mode-based super twisting controller is utilized to track the desired forces generated by the nonsingular fast terminal sliding mode controller with actuator faults and uncertainties. The controllers are robust against disturbances, uncertainties, and faults. Moreover, the stability of the super twisting controller is proved by the strong Lyapunov functions. Finally, numerical simulations are performed to demonstrate the effectiveness of the controller. Four different conditions, random road profile, bump road excitation, single-wheel bump excitation, and partial faults are considered. The main contributions of this study are: (1) combination of the above algorithms to deal with actuator faults and improve active suspension performance; (2) the controller proposed in this study has a simple structure. Simulation results indicate that the nonsingular fast terminal sliding mode super twisting controller can guarantee the performance of the closed-loop system under both faulty and healthy conditions.

Design of reduced-order observers for nonlinear sampled-data strict-feedback systems with actuator dynamics and disturbances

ABSTRACTWe design reduced-order observers for nonlinear sampled-data strict-feedback systems with actuator dynamics and disturbances. First, we use the property of the Euler model of sampled-data systems and the structure of discrete-time observers to design reduced-order observers of the Euler model. Then, we show that the designed observers are semiglobal and practical in T for the exact model. We also give both numerical and practical examples to illustrate the proposed design of reduced-order observers.

Error-constrained path-following control for a stratospheric airship with actuator saturation and disturbances

ABSTRACTThis paper is concerned with the path-following control problem for an under-actuated stratospheric airship with error constraint, actuator saturation, and external disturbances. To address the tracking error-constrained requirements of airship position and attitude, novel tan-type barrier Lyapunov functions are proposed and incorporated with the guidance and attitude control schemes, which calculate the desired attitude and angular velocity. An auxiliary design system in the form of anti-windup compensator is employed to deal with actuator saturation, and the stability of the saturated control solution is verified. Nonlinear disturbance observer is developed to estimate the unknown external disturbances. Rigorous stability analysis shows that the constrained requirements on the airship position and attitude will not be violated under the proposed control method and all closed-loop signals are uniformly ultimately bounded, despite the presence of actuator saturation and disturbances. Simulation results and comparisons illustrate the effectiveness of the proposed controller.

Robustification of sample-and-hold stabilizers for control-affine time-delay systems

This paper deals with the stabilization in the sample-and-hold sense of nonlinear, control affine, retarded systems, affected by actuation disturbances and observation errors. Input-to-state stability redesign methods are used in order to design a new sampled-data controller. It is shown that stabilization in the sample-and-hold sense can be preserved by means of this new controller, regardless of the above disturbances and errors. It is assumed that both actuator disturbance and observation error are bounded, and the (arbitrary) bounds are known a-priori. It is moreover assumed that the observation errors do not affect or affect marginally the new control term obtained by input-to-state stability redesign. Simulations on a continuous stirred tank reactor with recycle validate the theoretical results.

Fault-tolerant sampled-data control of singular networked cascade control systems

ABSTRACTThis paper investigates the reliable sampled-data control problem for a class of singular networked cascade control systems with randomly occurring actuator failures, time-varying delay and disturbances. In particular, the randomly occurring actuator failures describes the phenomenon of the actuator failure appearing in a random way and is modelled by a Bernoulli distributed white noise sequences with a known conditional probability. The main purpose of this work is to design a reliable sampled-data controller such that an optimised upper bound of the predefined performance index is well guaranteed for the systems under consideration even in the presence of both the randomly occurring actuator failures and disturbances. The resulting controllers are reliable in the sense that they will provide guaranteed stochastically admissible and performance index when all actuators are operational as well as when some actuators experiences failure. Finally, two numerical examples are given to exhibit the effectiveness of the proposed control scheme.

Fault-Tolerant Control of a Nonlinear System Actuator Fault Based on Sliding Mode Control

This paper presents a fault-tolerant control scheme for a class of nonlinear systems with actuator faults and unknown input disturbances. First, the sliding mode control law is designed based on the reaching law method. Then, in view of unpredictable state variables and unknown information in the control law, the original system is transformed into two subsystems through a coordinate transformation. One subsystem only has actuator faults, and the other subsystem has both actuator faults and disturbances. A sliding mode observer is designed for the two subsystems, respectively, and the equivalence principle of the sliding mode variable structure is used to realize the accurate reconstruction of the actuator faults and disturbances. Finally, the observation value and the reconstruction value are used to carry out an online adjustment to the designed sliding mode control law, and fault-tolerant control of the system is realized. The simulation results are presented to demonstrate the approach.

Disturbance rejection control for attitude control of air-breathing hypersonic vehicles with actuator dynamics

A novel disturbance rejection control scheme is proposed to address the robust attitude control problem for the air-breathing hypersonic vehicle with actuator dynamics and disturbances based on predictive sliding mode control and nonlinear disturbance observer. To achieve attitude control subtly and precisely, the attitude control system is decomposed into two subsystems: the outer-loop subsystem and inner-loop subsystem. Different control schemes are taken to attenuate or reject model uncertainties and external disturbances, whose influences on the two subsystems are different. The predictive sliding mode control is first utilized to attenuate model uncertainties imposed on the outer-loop subsystem. Then, a novel nonlinear disturbance observer–based predictive sliding mode control is proposed to tackle the mismatched disturbances with remarkable influence on the inner-loop subsystem. Afterward, both the effectiveness and stability of the proposed nonlinear disturbance observer–based predictive sliding mode control disturbance rejection control scheme are demonstrated from the theoretical prospective. Finally, simulation results are given to present the effectiveness and robustness of the proposed disturbance rejection control scheme.

Robust Sample-and-Hold Stabilization for Nonlinear Retarded Systems

In this paper we deal with the stabilization in the sample and hold sense of retarded systems affected by actuation disturbances and observation errors. We make use of input-to-state stability redesign methods in order to arbitrarily attenuate the effects of the above disturbances and measures errors. We show that stabilization in the sample-and-hold sense can be achieved, as long as actuation disturbances and observation errors are bounded and the bounds are known a priori, and as long as the observation errors do not affect or affect marginally the new added control term.

Design and implementation of new optimal linear actuator fault diagnosis observers

The paper presents the design for new three linear observers based on three optimal theorems to detect and diagnose an actuator fault and disturbance. The diagnosed fault for two observers AOA have been considered as an actuator fault while the fault for the third observer AOAD has been assumed as an additive fault. The gain matrices satisfied the proposed optimal conditions based on Lyapunov functions to diagnose fault and disturbance. The proposed faults and disturbance are white noise, coloured noise and non-Gaussian fault. Conditions for the observers AOA based on Theorem 1 and AOAD have been optimised according to the gain and actuator matrices while the observer AOA based on Theorem 2 has been designed according to the optimisation of the gain, actuator and fault matrices. As the results show, the observer AOA based on Theorem 2 is superior in terms of fault detection and diagnosis FDD when compared with the AOA based on Theorem 1 and AOAD observers. Finally the AOAD observer is the least efficient.

Robust adaptive fault tolerant control for a class of Lipschitz nonlinear systems with actuator failure and disturbances

This article presents novel robust adaptive fault tolerant control strategies for the class of nonlinear Lipschitz systems in the presence of bounded matched or unmatched disturbances and actuator faults (failure, loss of effectiveness, and stuck). Two constructive algorithms, based on linear matrix inequalities with creatively using Lyapunov stability theory, are developed for online tuning of adaptive and fixed state feedback gains to stabilize the closed-loop control system asymptotically, to compensate actuator faults, and to attenuate disturbance effects. The resultant control schemes have simpler and constructive structures as compared with most existing methods. The merits of the proposed schemes have been verified by the simulation on an unstable nonlinear process subjected to actuator faults.

Optimal Transport Approach for Probabilistic Robustness Analysis of F-16 Controllers

This paper presents a new framework for controller robustness verification with respect to an F-16 aircraft’s closed-loop performance in longitudinal flight. The state regulation performance of a linear quadratic regulator and a gain-scheduled linear quadratic regulator are compared, where both controllers are applied to nonlinear open-loop dynamics of an F-16, in the presence of stochastic initial condition and parametric uncertainties, as well as actuator disturbance. It is shown that, in the presence of initial condition uncertainties alone, both the linear quadratic regulator and gain-scheduled linear quadratic regulator have comparable immediate and asymptotic performances, but the gain-scheduled linear quadratic regulator exhibits better transient performance at intermediate times. This remains true in the presence of additional actuator disturbance. Also, the gain-scheduled linear quadratic regulator is shown to be more robust than the linear quadratic regulator against parametric uncertainties. The probabilistic framework proposed here leverages transfer-operator-based density computation in exact arithmetic and introduces optimal transport theoretic performance validation and verification for nonlinear dynamical systems. Numerical results from the proposed method are in unison with Monte Carlo simulations.

Robustification of nonlinear stabilizers in the sample-and-hold sense

It is well known in the literature that stabilization in the sample-and-hold sense is robust with respect to suitably small actuator disturbances. In this paper it is shown that, given a locally bounded steepest descent feedback (continuous or not), induced by a Control Lyapunov Function, the input-to-state stability redesign method can be exploited such that, with a new sampled-data control law, stabilization in the sample-and-hold sense is still guaranteed with arbitrarily large, bounded, actuator disturbance, as long as the bound of the disturbance is known a priori. Observation error is partially allowed too. It is allowed to be arbitrarily large, with a known bound, as long as it does not affect (or affects marginally) the new added control term. The provided results are validated by simulations on a continuous stirred tank chemical reactor.

Robust control of a yaw-pitch gimballed seeker

Purpose – This paper aims to present a robust design approach to realize disturbance attenuation for a yaw – pitch gimballed system subject to actuator saturation and disturbances. Design/methodology/approach – To minimize the impacts of disturbances in the presence of saturation nonlinearity and acquire desired response performance, the control approach is of double closed-loop configuration. State feedback controllers are synthesized via convex optimization and used to stabilize the inner loops; robust controllers are synthesized via mixed H ∞ optimization and used to stabilize the outer loops. Findings – It is shown through performance simulations that the proposed control scheme is effective in terms of command following, stability and disturbance attenuation. Practical implications – The presented robust control approach provides a theoretical method to facilitate designing a stable servo control loop for a yaw – pitch gimballed seeker. Originality/value – This paper supplies an effective way of addr...

Adaptive actuator failure compensation and disturbance rejection scheme for spacecraft

An adaptive actuator failure compensation scheme is proposed for attitude tracking control of spacecraft with unknown disturbances and uncertain actuator failures. A new feature of this adaptive control scheme is the adaptation of the failure pattern parameter estimates, as well as the failure signal parameter estimates, for direct adaptive actuator failure compensation. Based on an adaptive backstepping control design, the estimates of the disturbance parameters are used to solve the disturbance rejection problem. The unknown disturbances are compensated completely with the stability of the whole closed-loop system. The scheme is not only able to accommodate uncertain actuator failures, but also robust against unknown external disturbances. Simulation results verify the desired adaptive actuator failure compensation performance.