adaptive controller for nonlinear time-varying reference systems

This paper presents an uncalibrated visual servoing scheme for underwater vehicle manipulator systems (UVMSs) with an eye-in-hand camera under uncertainties. These uncertainties contain vision sensor parameters, UVMS kinematics and feature position information. At first, a linear separation approach is addressed to collect these uncertainties into vectors, and this approach can also be utilized in other free-floating based manipulator systems. Secondly, a novel nonlinear adaptive controller is proposed to achieve image error convergence by estimating these vectors, the gradient projection method is utilized to optimize the restoring moments. Thirdly, a high order disturbance observer is addressed to deal with time-varying disturbances, and the convergence of the image errors is proved under the Lyapunov theory. Finally, in order to illustrate the effectiveness of the proposed method, numerical simulations based on a 9 degrees of freedom (DOFs) UVMS with an eye-in-hand camera are conducted. In simulations, the UVMS is expected to track a circle trajectory on the image plane, meanwhile, time-varying disturbances are exerted on the system. The proposed scheme can achieve accurate and smooth tracking results during simulations.

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Finite-Time Synchronization of Complex Multilinks Networks with Perturbations and Time-Varying Delay Based on Nonlinear Adaptive Controller

Mathematical Problems in Engineering ◽

10.1155/2019/7656820 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12

Author(s):

Lixiang Li ◽

Qingbiao Liu ◽

Tao Li

Keyword(s):

Finite Time ◽

Time Synchronization ◽

Sufficient Conditions ◽

Adaptive Controller ◽

Linear Matrix ◽

Time Varying ◽

Finite Time Stability ◽

Analytical Technique ◽

Time Varying Delay ◽

Product Inequality

This paper utilizes nonlinear adaptive feedback controller to make the complex multilinks networks with perturbations and time-varying delays achieve the finite-time synchronization. By designing nonlinear controllers, we use suitable Lyapunov functions and sufficient conditions to guarantee the finite-time synchronization between the drive system and the response system in terms of adaptive control. Several novel and useful finite-time synchronization criteria are accurately derived based on linear matrix inequality, Kronecker product, inequality analytical technique, and finite-time stability theory. Finally, numerical examples are given to demonstrate the validity and the effectiveness of our theoretical results.

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Complete Periodic Synchronization of Memristor-Based Neural Networks with Time-Varying Delays

Discrete Dynamics in Nature and Society ◽

10.1155/2013/140153 ◽

2013 ◽

Vol 2013 ◽

pp. 1-12 ◽

Cited By ~ 9

Author(s):

Huaiqin Wu ◽

Luying Zhang ◽

Sanbo Ding ◽

Xueqing Guo ◽

Lingling Wang

Keyword(s):

Neural Networks ◽

Periodic Solution ◽

Matrix Theory ◽

Adaptive Controller ◽

Network System ◽

Time Varying ◽

State Dependent ◽

Coincidence Theorem ◽

Error System ◽

Theoretical Results

This paper investigates the complete periodic synchronization of memristor-based neural networks with time-varying delays. Firstly, under the framework of Filippov solutions, by usingM-matrix theory and the Mawhin-like coincidence theorem in set-valued analysis, the existence of the periodic solution for the network system is proved. Secondly, complete periodic synchronization is considered for memristor-based neural networks. According to the state-dependent switching feature of the memristor, the error system is divided into four cases. Adaptive controller is designed such that the considered model can realize global asymptotical synchronization. Finally, an illustrative example is given to demonstrate the validity of the theoretical results.

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Adaptive gain-order fractional control for network-based applications

Fractional Calculus and Applied Analysis ◽

10.2478/s13540-014-0180-6 ◽

2014 ◽

Vol 17 (2) ◽

Cited By ~ 12

Author(s):

Inés Tejado ◽

S. HosseinNia ◽

Blas Vinagre

Keyword(s):

Control Systems ◽

Networked Control Systems ◽

Adaptive Controller ◽

System Stability ◽

Switching Systems ◽

Time Varying ◽

Control Performance ◽

Velocity Control ◽

Fractional Control ◽

Gain Scheduled

AbstractThis paper deals with the application of adaptive fractional order control to networked control systems (NCSs) to compensate the effects of time-varying network-induced delays. In essence, it adapts both the gains and the orders of a local PIαDμ controller in accordance with the current network condition in order to avoid a decreased control performance. A frequency domain framework is provided to analyze the system stability on the basis of the switching systems theory. The velocity control of a servomotor through the Internet is given to show the effectiveness of the proposed adaptive controller, including a comparison with non- and gain scheduled controllers.

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L1 Adaptive Controller for a Class of Nonlinear Systems

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4026302 ◽

2014 ◽

Vol 136 (3) ◽

Cited By ~ 7

Author(s):

Jie Luo ◽

Chengyu Cao

Keyword(s):

Nonlinear Systems ◽

Reference System ◽

Adaptive Controller ◽

Time Varying ◽

Robot Arm ◽

Performance Bounds ◽

Estimation Errors ◽

State Dependent ◽

Low Pass ◽

L1 Adaptive Controller

This paper presents an extension of the L1 adaptive controller to a class of nonlinear systems where the control effectiveness is time-varying and unknown, but with a known sign. Moreover, this class of nonlinear systems contains time-varying and unknown state-dependent nonlinearities. The proposed L1 adaptive controller consists of three components, a state predictor used to estimate real states, an adaptive law used to update the adaptive parameters in the state predictor, and a low-pass filtered control law. First, the stable closed-loop reference system is constructed. Then, the estimation errors between estimated states and real states are proved to be arbitrarily small by increasing the adaptation rate. After that, we further prove that the adaptive controller ensures uniformly bounded transient and asymptotical tracking of the reference system. The performance bounds can be systematically improved by increasing the adaptation rate. Simulation results on a single-link nonlinear robot arm verify the theoretical findings.

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Robust Adaptive Control of Mildly Nonlinear Systems With Time Varying Input/Output Delays

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring ◽

10.1115/smasis2012-7924 ◽

2012 ◽

Author(s):

James P. Nelson ◽

Mark J. Balas ◽

Richard S. Erwin

Keyword(s):

Adaptive Control ◽

Nonlinear Systems ◽

Adaptive Controller ◽

Robust Adaptive Control ◽

Control Law ◽

Time Varying ◽

Robust Adaptive ◽

Input Delays ◽

Persistent Disturbances ◽

Adaptive Control Law

Many systems must operate in the presence of delays both internal to the system and in its inputs and outputs. In this paper we present a robustness result for mildly nonlinear systems. We use this result to show that, for small unknown time varying input delays, a simple adaptive controller can produce output regulation to a neighborhood with radius dependent upon the size of an upper bound on the delay. This regulation occurs in the presence of persistent disturbances and the convergence is exponential. We conclude with an example to illustrate the behavior of this adaptive control law.

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