Composite Nonlinear Feedback Control Method Research Articles

Tracking control for a class of fractional order uncertain systems with time-delay based on composite nonlinear feedback control

<abstract><p>In this paper, we dealt with the tracking control problem of a class of fractional-order uncertain systems with time delays. In order to handle the effects brought by the uncertainties, external disturbances, time-delay terms, and to overcome the obstacles caused by inputs saturation, the tracking controller, which consisted of linear control law, nonlinear law, and robust control law proposed in this paper, was designed by combining the composite nonlinear feedback control method and the properties of fractional order operators. Furthermore, the validation of this tracking controller was proved.</p></abstract>

Robust composite nonlinear feedback control based on integral sliding-mode control of uncertain time-delay systems under input saturation

In this research, based on the integral sliding-mode scheme, a robust composite nonlinear feedback (CNF) control is addressed for time-delayed uncertain systems. Such an uncertain system may contain some complexities like time-varying delays, actuators saturation, and exterior disturbances. Hence, the tracking problem would be solved under the mentioned constraints. Thus, for achieving these goals, the tracking problem is firstly formulated by considering system’s limitations. The controller parameters may be determined via a solution for linear matrix inequality. As a result, the CNF tracker law is numerically simulated in some control cases. The simulation outcomes are compared with a similar technique in terms of the transient response, boundedness of the error, and the disturbance rejections. Thus, the findings illustrate the efficiency of the advised CNF control method comparing to the recent technique.

Fuzzy Observer-Based Transitional Path-Tracking Control for Autonomous Vehicles

This study addresses the path-tracking control issue of autonomous vehicles (AVs) when the GPS measurement is temporarily unavailable. In such a case, the vehicle states, location or the curvature of the reference path might be unobtainable, while the camera can be potentially used to detect the path-tracking states. To this end, this paper proposes a fuzzy-observer-based composite nonlinear feedback (CNF) controller with a Takagi-Sugeno (T-S) vehicle lateral dynamic model to guarantee the normal path-tracking maneuver and improve the transient performance. A parallel distributed compensation (PDC)-based CNF control method is developed to realize the control objective with the T-S vehicle model considering the transient performance and actuator saturation. The closed-loop stability and ${H} _{ \boldsymbol {\infty }}$ index performance integrating the tracking and estimation errors have been proved with a Lyapunov approach. The observer-based controller design has been implemented based on the formulation of the linear matrix inequalities (LMIs). High-fidelity simulations using CarSim-Matlab/Simulink have demonstrated the validity of the proposed approach in terms of enhancing the tracking performance under the input saturation and disturbances in GPS-denied environments.

A robust control approach for MEMS capacitive micromachined ultrasonic transducer

An optimal composite nonlinear feedback control method with integral sliding mode is presented in this paper. The controller extends the travel range of the micro-electromechanical system capacitive micromachined ultrasonic transducer (CMUT). Moreover, enhanced transient response and precise tracking performance is achieved. It is known that CMUT is inherently unstable which results in pull-in phenomenon and it is very sensitive to small perturbations, so one of the major problems is to stabilize the CMUT beyond the pull-in limit with the external disturbances. In addition, the input saturation problem is significant to CMUT. Based on that, a robust control scheme is derived using composite nonlinear feedback control law combined with integral sliding mode control law. Then all the tuning parameters for the proposed control method are converted into a minimization problem and solved by particle swarm optimization algorithm automatically. We verified the effectiveness through extending the travel range of the CMUT gap by three control methods which are proportional integral derivative, composite nonlinear feedback and the method we proposed. The stability and small range tracking performance with three control methods is compared on the pull-in position of CMUT. The simulations show that the proposed control method has desired tracking performance and robustness to external disturbance with input saturation.

Robust time-varying output tracking control in the presence of actuator saturation

This paper considers the problem of output tracking of a time-varying reference signal for a class of uncertain systems in the presence of actuator saturation. To achieve this capability, a new controller is proposed by robustifying the generalized composite nonlinear feedback control method with the integral sliding mode controller. Since the proposed controller may be saturated, a precise analysis is done to show its robust performance despite the presence of actuator saturation and model uncertainties. For this purpose, a theorem is given and proved that guarantees the robust output tracking via the proposed control law for three different cases of the saturation function and it is shown that even if the control signal is saturated, the proposed controller achieves output tracking of the time-varying reference signal. Also, in order to show the applicability of the proposed controller, it is applied on two practical systems, the XY-table and inertia wheel inverted pendulum. Computer simulations verify the theoretical results and also display the effective performance of the proposed controller.

Design of a robust tracker and disturbance attenuator for uncertain systems with time delays

This article considers the composite nonlinear feedback control method for robust tracker and disturbance attenuator design of uncertain systems with time delays. The proposed robust tracker improves the transient performance and steady state accuracy simultaneously. The asymptotic robust tracking conditions are provided in the form of linear matrix inequalities and the resultant conditions yield the controller gains. Moreover, to improve the reference tracking performance, a new nonlinear function for the composite feedback control law is offered. Simulation results are presented to verify the theoretical results. © 2014 Wiley Periodicals, Inc. Complexity 21: 340–348, 2015

Composite nonlinear feedback controller design for an overhead crane servo system

This paper investigates the design of a composite nonlinear feedback (CNF) control law for an overhead crane servo system to improve the transient performance of both displacement tracking of the trolley and anti-sway of the payload. To address the property of underactuation of the overhead crane system, a novel nonlinear function of the CNF control law is specifically proposed to compromise the tracking performance of the trolley and the anti-sway performance of the payload. The performance improvement in both tracking of the trolley and anti-sway of the payload is illustrated with a complete comparison between the CNF control method and the trajectory planning method, which has been proposed in recent literature. The simulation results show that this well-tuned CNF control law can significantly shorten the settling time of the trolley displacement tracking and reduce the sway of the payload.

Robust tracking control method based on composite nonlinear feedback technique for linear systems with time-varying uncertain parameters and disturbances

In this paper, the composite nonlinear feedback control method is considered for robust tracking and model following of uncertain linear systems. The control law guarantees that the tracking error decreases asymptotically to zero in the presence of time varying uncertain parameters and disturbances. For performance improvement of the dynamical system, the proposed robust tracking controller consists of linear and nonlinear feedback parts without any switching element. The linear feedback law is designed to allow the closed loop system have a small damping ratio and a quick response while the nonlinear feedback law increases the damping ratio of the system as the system output approaches the output of the reference model. A new collection of different nonlinear functions used in the control law are offered to improve the reference tracking performance of the system. The proposed robust tracking controller improves the transient performance and steady state accuracy simultaneously. Finally, the simulations are provided to verify the theoretical results.