Observer-based Adaptive Output Feedback Research Articles

Observer-Based Adaptive Control for Trajectory Tracking of AUVs with Input Saturation

In this paper, an observer-based adaptive control method is investigated for the horizontal trajectory tracking of autonomous underwater vehicles (AUV) with input saturation and system disturbances. Firstly, the desired surge speed and trajectory angle are established, which could decouple the tracking error subsystem and avoid the complex form. Secondly, the input saturation is approximated by a smooth function, and a nonlinear extended states observer (NESO) is designed for estimating system disturbances. Based on the command filtered backstepping technique, which can avoid the explosion caused by the derivative of the virtual control, an observer-based adaptive output feedback control method is developed, and an auxiliary system is applied to compensate for filtered tracking errors, input saturation bias, and observer errors. Finally, simulation results show the proposed method has good robustness in the face of system uncertainties, and the error is nearly 33.3% smaller than that of other control methods when meeting sudden trajectory changes. A good control performance is guaranteed.

Damping assignment of boundary controlled port-Hamiltonian systems with unknown open-loop damping

A damping assignment control law for infinite-dimensional port-Hamiltonian systems in one-dimensional space with actuators and sensors located at the spatial boundaries is proposed with the novelty that the boundary damping is unknown. This allows us to fix a desired decay of energy for the cases in which the system is over-damped, poorly damped, and even with negative damping. We propose an observer composed of an infinite-dimensional model and a finite-dimensional one for the state and parameter estimation. The asymptotic convergence of the observer is shown using LaSalle's invariance principle assuming that the trajectories are pre-compact. Finally, an observer-based adaptive output feedback controller is proposed for the damping assignment in the closed loop. The passivity of the closed-loop system is guaranteed with respect to the initial Hamiltonian of the system under the assumption that the observer is initialized identically to the current state and close enough to the parameter value. The transmission line is used to exemplify this approach.

Nonlinear observer-based adaptive output feedback tracking control of underactuated ships with input saturation

Nonlinear observer-based adaptive output feedback tracking control of underactuated ships with input saturation

Sampled observer-based adaptive output feedback fault-tolerant control for a class of strict-feedback nonlinear systems

This paper studies the sampled outputs-based adaptive fault-tolerant control problem for a class of strict-feedback uncertain nonlinear systems, where the nonlinear functions are allowed to include the unmeasured system states. Within the framework, a sampled output observer is introduced to jointly estimate the system states and parameters. By combining the estimated states and the supervisory switching strategy, an adaptive fault-tolerant controller is designed to achieve the desirable tracking performance. By using Lyapunov stability theory, it is proved that all the signals of the closed-loop systems are bounded and the tracking error converges to an adjustable neighbourhood of the origin eventually both in the fault free and faulty cases. Especially, if the outputs are available all the time, the proposed output feedback fault-tolerant control method can ensure the tracking error satisfy the prescribed performance bounds regardless of the faults. Finally, two examples are used to illustrate the effectiveness of the proposed method.

Observer-Based Adaptive Output-Feedback Fault-Tolerant Control of a Class of Complex Dynamical Networks

This paper is concerned with the observer-based adaptive output-feedback fault-tolerant control (FTC) problem for a class of complex dynamical networks (CDNs) with actuator faults. First, to address the coupling terms involved in the node dynamics, algebraic graph theory is used to design a new distributed state observer. Then, an observer-based adaptive output feedback FTC scheme is given to achieve the desired synchronization performance. Furthermore, via the Lyapunov analysis approach, it is proved that both the state estimation errors and the synchronization errors are all bounded for the faulty cases, while the asymptotical convergence is ensured for the fault-free case. In addition, it is shown that the proposed FTC scheme is valid for CDN with both time-invariant and time-variant graphs. Finally, a simulation example is given to illustrate the effectiveness of the theoretical results.

Nonlinear augmented state observer-based adaptive output feedback anti-disturbance control for nonlinear systems with non-harmonic multiple uncertainties

In this paper, a novel output feedback anti-disturbance control method is carried out for a class of nonlinear systems subject to non-harmonic multisource disturbances. By using a nonlinear exogenous system, a class of non-harmonic disturbances possessing complex and nonlinear characteristics are taken fully into consideration. Based on a nonlinear damping term, we establish an adaptive augmented state observer that can achieve robust asymptotic disturbance estimation for the system states, the harmonic disturbances and the non-harmonic disturbances. By fusing the augmented state observer and a state-feedback controller, a robust adaptive output feedback anti-disturbance control structure is constructed. The boundness of the combined controller–observer system is derived on the basis of Lyapunov analysis. Furthermore, aiming at the intense non-harmonic disturbances, the proposed method is extended and a new output feedback controller is obtained. The effectiveness of the proposed scheme is demonstrated through experimental studies on a practical example.

Observer-Based Adaptive Output Feedback Control for Miniature Aerial Vehicle

In this paper, we propose an observer-based adaptive output feedback flight tracking system for the miniature aerial vehicle (MAV) in the presence of bounded uncertainty. The proposed design has two parts. First, a state feedback based nonlinear adaptive control algorithm is designed by assuming that all the states are available for feedback. The convergence analysis with the state feedback based design is derived by using the Lyapunov method. Second, we replace the unknown velocity states by a linear observer to develop adaptive output feedback flight tracking system for the MAV. The convergence analysis with the observer-based output feedback design is shown by using a singularly perturbed method. The analysis shows that the performance achieved under state feedback can be recovered by using an output feedback based design. Evaluation results are given to demonstrate the effectiveness of the proposed design for real-time applications.

Observer-based adaptive output feedback tracking control of dynamically positioned surface vessels

This work concentrates on tracking control of dynamically positioned surface vessels where only position and orientation measurements are available. Specifically, in order to remove the velocity measurement dependency of the control formulation, we designed a nonlinear, model-free observer which enables the observer-controller couple to achieve asymptotic tracking. Stability of the closed-loop system is ensured by Lyapunov-based arguments. Simulation studies are also presented to illustrate the effectiveness of the proposed method.

Adaptive Output Feedback Design Using Asymptotic Properties of LQG/LTR Controllers

This technical note introduces an observer-based adaptive output feedback tracking control design for multi-input-multi-output dynamical systems with matched uncertainties. The reported methodology exploits asymptotic behavior of LQG/LTR regulators. Sufficient conditions for closed-loop stability and uniform ultimate boundedness of the corresponding tracking error dynamics are formulated. This method is valid for systems whose nominal linearized dynamics are controllable and observable. We assume that the number of the system measured outputs (sensors) is greater than the number of the control inputs (actuators) and that the system output-to-input matrix product has full column rank. In this case, the system can be “squared-up” (i.e., augmented) using pseudo-control signals to yield relative degree one minimum-phase dynamics. Since it is known that the “squaring-up” problem is solvable for any controllable observable triplet (A, B, C), the proposed design is applicable to systems whose regulated output dynamics may be non-minimum phase or have a high relative degree. A simulation example is presented to demonstrate key design features.

A novel error observer-based adaptive output feedback approach for control of uncertain systems

We develop an adaptive output feedback control methodology for nonaffine in control of uncertain systems having full relative degree. Given a smooth reference trajectory, the objective is to design a controller that forces the system measurement to track it with bounded errors. A neural network with linear parameters is introduced as an adaptive signal. A simple linear observer is proposed to generate an error signal for the adaptive laws. Ultimate boundedness is shown through Lyapunov's direct method. Simulations of a nonlinear second-order system illustrate the theoretical results.