External Disturbance Attenuation Research Articles

Consensus Tracking of Singular Multiagent Systems via Sliding-Mode Approach

The admissible consensus tracking control of singular multiagent systems under nonlinear actuator attacks is investigated in this paper. A novel distributed adaptive protocol is designed, which can approximate the actuator attack by adaptive updating the weight matrix of neural network. An integral sliding surface is constructed based on the singularity of agents, and the sliding mode dynamics can reach the sliding mode surface in finite time under the proposed protocols. Sufficient conditions of impulse free and consensus tracking control of the singular multiagent systems are proved, and the attenuation of external disturbances is verified. The effectiveness of the proposed methods is verified through the numerical simulation examples.

Applying Cognitive Methodology in Designing On-Line Auto-Tuning Robust PID Controller for the Real Heating System

A novel design and implementation of a cognitive methodology for the on-line auto-tuning robust PID controller in a real heating system is presented in this paper. The aim of the proposed work is to construct a cognitive control methodology that gives optimal control signal to the heating system, which achieve the following objectives: fast and precise search efficiency in finding the on- line optimal PID controller parameters in order to find the optimal output temperature response for the heating system. The cognitive methodology (CM) consists of three engines: breeding engine based Routh-Hurwitz criterion stability, search engine based particle swarm optimization (PSO) and aggregation knowledge engine based cultural algorithm (CA). Matlab simulation package is used to carry out the proposed methodology that finds and tunes the optimal values of the robust PID parameters on-line. In real-time, the LabVIEW package is guided to design the on-line robust PID controller for the heating system. Numerical simulations and experimental results are compared with each other and showed the effectiveness of the proposed control methodology in terms of fast and smooth dynamic response for the heating system, especially when the control methodology considers the external disturbance attenuation problem.

Repetitive control design for switched neutral systems with input time‐delay

SummaryThe design of tracking control problem and compensation of disturbance for switched neutral systems with multiple time‐delays and external disturbances are addressed in this paper. In this regard, a modified repetitive control technique based on the Matausek‐Micic modified Smith predictor approach is being implemented, which assures the exact tracking performance and disturbance attenuation with high precision in the considered system. To be specific, the integration of transfer function with modified Smith predictor block not only provides the accurate compensation of input time‐delays but also ensures the exact estimation and attenuation of external disturbances effectually. Furthermore, according to Lyapunov stability approach combined with average‐dwell‐time technique, a group of adequate conditions is derived in the form of matrix inequalities. Simultaneously, by solving the established matrix inequalities using available software the controller gain matrices are calculated. Ultimately, the simulation results of three numerical examples are presented to validate the efficiency and dominance of the suggested control procedure.

Switched linear parameter‐varying tracking control for quadrotors with large attitude angles and time‐varying inertia

AbstractThis paper is concerned with large‐angle attitude tracking control for quadrotors in the presence of time‐varying inertia and external disturbances using a switched linear parameter‐varying (LPV) system method. The attitude system of the quadrotor is divided into two parts, that is, the outer attitude‐angle loop and inner angular‐velocity loop. A feedback linearization controller is designed in the outer loop to generate the desired angular velocities. In the inner loop, the nonlinear quadrotor dynamics with time‐varying inertia is approximated by a switched LPV system that consists of a series of LPV models. The persistent dwell time (PDT) switching logic is adopted to describe the fast and slow switches coexist among these LPV models. Then, both the continuous‐time state‐feedback and dynamic output‐feedback controllers are designed, which ensure the globally uniformly asymptotically stability and external disturbance attenuation performance of the attitude tracking error system. Finally, the effectiveness of the proposed tracking control method of quadrotors is validated with an example.

Active Vibration Suppression of Uncertain Hose and Drogue Systems in the Presence of Actuator Nonlinearities

This paper investigates vibration suppression of uncertain hose and drogue systems in the presence of actuator nonlinearities. Firstly, a previously presented model of the hose and drogue systems is extended to describe how the hose and drogue systems restrain the vibration, while the accompanying unknown aerodynamic coefficients are estimated by invoking the parameter projection method. Subsequently, for the actuator nonlinearities of dead-zone and saturation, a smooth dead-zone approximate function is constructed to design the dead-zone compensation method, based upon which the proposed control scheme can handle actuator dead-zone and saturation simultaneously while improving the output efficiency of the actuator. Next, for the actuator nonlinearities of backlash and saturation, a smooth backlash inverse is constructed based upon which the presented control scheme can cope with the both actuator nonlinearities simultaneously. Finally, by utilizing backstepping method and hyperbolic tangent function, the proposed control schemes can also achieve the control objectives of vibration suppression and external disturbance attenuation. Simulation examples are included to demonstrate the validity of the proposed control schemes.

High-speed trains automatic operation with protection constraints: a resilient nonlinear gain-based feedback control approach

This paper addresses the control design for automatic train operation of high-speed trains with protection constraints. A new resilient nonlinear gain-based feedback control approach is proposed, which is capable of guaranteeing, under some proper non-restrictive initial conditions, the protection constraints control raised by the distance-to-go &#x0028 moving authority &#X0029 curve and automatic train protection in practice. A new hyperbolic tangent function-based model is presented to mimic the whole operation process of high-speed trains. The proposed feedback control methods are easily implementable and computationally inexpensive because the presence of only two feedback gains guarantee satisfactory tracking performance and closed-loop stability, no adaptations of unknown parameters, function approximation of unknown nonlinearities, and attenuation of external disturbances in the proposed control strategies. Finally, rigorous proofs and comparative simulation results are given to demonstrate the effectiveness of the proposed approaches.

Path Planning Generation Algorithm for a Class of UAV Multirotor Based on State of Health of Lithium Polymer Battery

Nowadays, it exists path planning strategies dedicated to generate trajectories considering different navigation issues in UAV multirotors, such as 3D navigation in cluttered and uncluttered environments, obstacle avoidance, and path re-planning. Such path generators are mainly based on the dynamics associated to position and orientation of the UAV, and the attenuation of external disturbances as the wind. However, one of the main limitations of these methods is that they do not take into account the relationship between the path planning task and the energy consumption associated with the battery performance or State of Health (SoH). In this work, a path planning generation algorithm that take into account the evolution of the battery performance is presented. First, the computation of the battery SoH is realized by introducing two degradation models. Subsequently, the path planning algorithm is defined as a multi-objective optimization problem where the objective is to find a feasible trajectory between way-points whiles minimizing the energy consumed and the mission final time depending on the variation of the battery SoH. Finally, the proposed path planning algorithm is compared with a classical path generation method based on polynomial functions to evaluate the minimization of the energy consumption. The simulation results demonstrate that the proposed path planning algorithm is able to generate feasible and minimum energy trajectories despite the constraints in the battery SoH.

Design of observer-based controller for T–S fuzzy systems with intermittent measurements

This paper studies the problem of observer-based fuzzy control for a class of nonlinear networked control systems (NCSs) in the framework of interval type-2 (IT2) Takagi–Sugeno (T–S) fuzzy model. Both imperfect communication channels and parameter uncertainties are taken into consideration. Bernoulli random distribution is used to describe such unreliable communication environment. Nonlinear NCSs are modeled via the IT2 T–S fuzzy model, in which membership functions with lower and upper bounds can capture and express parameter uncertainties. The observer is designed to observe unmeasurable state variables. Moreover, based on these techniques, sufficient conditions are derived to guarantee the resulting closed-loop system to be stochastically stable and possess the property of external disturbance attenuation. Finally, a numerical example is provided to illustrate the effectiveness of the approach proposed in this paper.

Inverse optimal sliding mode control of spacecraft with coupled translation and attitude dynamics

This paper proposes two robust inverse optimal control schemes for spacecraft with coupled translation and attitude dynamics in the presence of external disturbances. For the first controller, an inverse optimal control law is designed based on Sontag-type formula and the control Lyapunov function. Then a robust inverse optimal position and attitude controller is designed by using a new second-order integral sliding mode control method to combine a sliding mode control with the derived inverse optimal control. The global asymptotic stability of the proposed control law is proved by using the second method of Lyapunov. For the other control law, a nonlinear H∞ inverse optimal controller for spacecraft position and attitude tracking motion is developed to achieve the design conditions of controller gains that the control law becomes suboptimal H∞ state feedback control. The ultimate boundedness of system state is proved by using the Lyapunov stability theory. Both developed robust inverse optimal controllers can minimise a performance index and ensure the stability of the closed-loop system and external disturbance attenuation. An example of position and attitude tracking manoeuvres is presented and simulation results are included to show the performance of the proposed controllers.

Terminal sliding mode control for continuous stirred tank reactor

A continuous stirred tank reactor (CSTR) is a typical example of chemical industrial equipment, whose dynamics represent an extensive class of second order nonlinear systems. It has been witnessed that designing a good control algorithm for the CSTR is very challenging due to the high complexity. The two difficult issues in CSTR control are state estimation and external disturbance attenuation. In general, in industrial process control a fast and robust response is essential. Driven by these challenging issues and desired performance, this paper proposes an output feedback terminal sliding mode control (TSMC) framework which is developed for CSTR, and can estimate the system states and stabilize the system output tracking error to zero in a finite time. The corresponding stability analysis is presented in terms of the Lyapunov method. Illustrative examples are demonstrated by using Matlab simulations to validate the effectiveness of the proposed approach.

A Symbolic Computation Approach to Parameterizing Controller for Polynomial Hamiltonian Systems

This paper considers controller parameterization method ofH∞control for polynomial Hamiltonian systems (PHSs), which involves internal stability and external disturbance attenuation. The aims of this paper are to design a controller with parameters to insure that the systems areH∞stable and propose an algorithm for solving parameters of the controller with symbolic computation. The proposed parameterization method avoids solving Hamilton-Jacobi-Isaacs equations, and thus the obtained controllers with parameters are relatively simple in form and easy in operation. Simulation with a numerical example shows that the controller is effective as it can optimizeH∞control by adjusting parameters. All these results are expected to be of use in the study ofH∞control for nonlinear systems with perturbations.

An Adaptive -Based Formation Control for Multirobot Systems

We describe a decentralized formation problem for multiple robots, where an formation controller is proposed. The network of dynamic agents with external disturbances and uncertainties are discussed in formation problems. We first describe how to design social potential fields to obtain a formation with the shape of a polygon. Then, we provide a formal proof of the asymptotic stability of the system, based on the definition of a proper Lyapunov function and technique. The advantages of the proposed controller can be listed as robustness to input nonlinearity, external disturbances, and model uncertainties, while applicability on a group of any autonomous systems with -degrees of freedom. Finally, simulation results are demonstrated for a multiagent formation problem of a group of six robots, illustrating the effective attenuation of approximation error and external disturbances, even in the case of agent failure or leader tracking.

Optimal Output Feedback Controllers for Spacecraft Attitude Tracking

AbstractThis paper investigates the problem of output feedback attitude tracking control of a rigid spacecraft in the presence of external disturbances. Two optimal control laws with a disturbance estimator are developed to deal with this problem. An adapted extended state observer is used to estimate the angular velocity tracking errors and to allow for compensation for the total disturbances. The proposed control can be expressed as the sum of a nonlinear optimal controller and an estimated disturbance. For the optimal controller, the state‐dependent Riccati equation and optimal Lyapunov techniques are employed to solve the infinite‐time nonlinear optimal control problem. The developed controllers can minimize a performance index and ensure the stability of the closed‐loop system and external disturbance attenuation. On the other hand, using the adapted extended state observer, the asymptotic convergence of estimation error dynamics is proven. An example of multiaxial attitude manoeuvres is given and simulation results are included to demonstrate and verify the usefulness of the proposed controllers.

Applying posture identifier in designing an adaptive nonlinear predictive controller for nonholonomic mobile robot

This paper presents a trajectory tracking controller for a nonholonomic mobile robot using an optimization algorithm based predictive feedback control and an adaptive posture identifier model while following a continuous and a non-continuous path. The posture identifier model is a modified Elman neural network that describes the kinematics and dynamics of the mobile robot model. The feedforward neural controller is trained off-line and its adaptive weights are adapted on-line to find the reference torques, which controls the steady-state outputs of the mobile robot system. The feedback neural controller is based on the posture neural identifier and quadratic performance index prediction algorithm to find the optimal torque action in the transient state for N-step-ahead prediction. General back propagation algorithm is used to learn the feedforward neural controller and the posture neural identifier. Simulation results and experimental work show the effectiveness of the proposed adaptive nonlinear predictive control algorithm; this is demonstrated by the minimized tracking error and the smoothness of the torque control signal obtained, especially with regards to the external disturbance attenuation problem.

A Novel Robust Decentralized Adaptive Fuzzy Control for Swarm Formation of Multiagent Systems

In this paper, a novel decentralized adaptive control scheme for multiagent formation control is proposed based on an integration of artificial potential functions with robust control techniques. Fully actuated mobile agents with partially unknown models are considered, where an adaptive fuzzy logic system is used to approximate the unknown system dynamics. The robust performance criterion is used to attenuate the adaptive fuzzy approximation error and external disturbances to a prescribed level. The advantages of the proposed controller can be listed as robustness to input nonlinearity, external disturbances, and model uncertainties, and applicability on a large diversity of autonomous systems. A Lyapunov-function-based proof is given of robust stability, which shows the robustness of the controller with respect to disturbances and system uncertainties. Simulation results are demonstrated for a swarm formation problem of a group of six holonomic robots, illustrating the effective attenuation of approximation errors and external disturbances, even in the case of agent failure. Moreover, experimental results confirm the validity of the presented approach and are included to verify the applicability of the scheme for a swarm of six real holonomic robots.

Adaptive fuzzy formation control for a swarm of nonholonomic differentially driven vehicles

In this paper, an adaptive fuzzy robust H∞ controller is proposed for formation control of a swarm of differential driven vehicles with nonholonomic dynamic models. Artificial potential functions are used to design the formation control input for kinematic model of the robots and matrix manipulations are used to transform the nonholonomic model of each differentially driven vehicle into equivalent holonomic one. The main advantage of the proposed controller is the robustness to input nonlinearity, external disturbances, model uncertainties, and measurement noises, in a formation control of a nonholonomic robotic swarm. Moreover, robust stability proof is given using Lyapunov functions. Finally, simulation results are demonstrated for a swarm formation problem of a group of six unicycles, illustrating the effective attenuation of approximation error and external disturbances, even in the case of robot failure.

Robust pole placement controller design in LMI region for uncertain and disturbed switched systems

This paper concerns the state feedback control for continuous-time, disturbed and uncertain linear switched systems with arbitrary switching rules. The main result of this work consists in getting a LMI (Linear Matrix Inequalities) condition guaranteeing a robust pole placement according to some desired specifications. Then, external disturbance attenuation with a fixed rate according to the H ∞ criterion is ensured. This is obtained thanks to the existence of a common quadratic Lyapunov function for all sub-systems. Finally, an academic example illustrates the efficiency of the developed approach.

Satisfactory reliable H∞ guaranteed cost control with D-stability and control input constraints

Based on the satisfactory fault-tolerant control strategy, the problem of reliable guaranteed cost control with multiple criteria constraints is investigated for a class of uncertain discrete-time systems subject to sensor faults. The state-feedback controller is developed by linear matrix inequalities approach such that, for all admissible parameters uncertainties and possible sensor faults, the given upper bounds on the amplitudes of control input signals be ensured, all the closed-loop poles be placed into the pre-specified regional disk, and the expected quadratic cost performance index as well as the given H∞ norm index of disturbance rejection level be guaranteed, simultaneously. Thus, with the above multiple criteria constraints, the resulting closed-loop system can provide satisfactory stability, transient property, external disturbance attenuation level and quadratic cost performance, despite the possible sensor faults.

Disturbance Attenuation and Trajectory Tracking via a Reduced-order Output Feedback Controller for Robot Manipulators

This paper presents a solution to the problem of trajectory tracking with external disturbance attenuation in robotics systems via a reduced-order output feedback controller, without velocity measurement. The proposed control law ensures both semi-global asymptotic stability of the closed-loop system and external disturbance attenuation. The approach is based on the notion of the L 2 -gain and requires to solve two algebraic Riccati inequalities. The proposed controller design is illustrated by a simulation example.

Synthesis of uncertain cascaded multiple loops systems with time delay

This paper presents a frequency domain design method for uncertain cascaded multiple loops systems with time delays. It is shown that the plant uncertainties and time delays can be transferred to the values of equivalent external disturbances at the plant output. Thus, the control design problem coping with parametric and time delay uncertainties can be treated as an equivalent external disturbance attenuation problem. An example is provided to illustrate the proposed design method.