scholarly journals Adaptive Fuzzy Path Tracking Control for Mobile Robots with Unknown Control Direction

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Qifei Du ◽  
Lin Sha ◽  
Wuxi Shi ◽  
Liankun Sun
Keyword(s):  
Mobile Robots ◽  
Tracking Control ◽  
Center Of Mass ◽  
Approximation Error ◽  
Path Tracking ◽  
Robust Controller ◽  
Adaptive Fuzzy ◽  
Unknown Control ◽  
Unknown Control Direction ◽  
Control Direction

In order to synthesize controllers for wheeled mobile robots (WMRs), some design techniques are usually based on the assumption that the center of mass is at the center of the robot itself. Nevertheless, the exact position of the center of mass is not easy to measure, thus WMRs is a typical uncertain nonlinear system with unknown control direction. Based on the fast terminal sliding mode control, an adaptive fuzzy path tracking control scheme is proposed for mobile robots with unknown control direction. In this scheme, the fuzzy system is used to approximate unknown functions, and a robust controller is constructed to compensate for the approximation error. The Nussbaum-type functions are integrated into the robust controller to estimate the unknown control direction. It is proved that all the signals in the closed-loop system are bounded, and the tracking error converges to a small neighborhood of the origin in a limited time. The effectiveness of the proposed scheme is illustrated by a simulation example.

scholarly journals Observer-Based Adaptive Fuzzy Predefined Performance Control of a Class of Nonlinear Pure-Feedback Systems with Input Delay

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xin Li ◽  
Qiang Zhang ◽  
Dakuo He
Keyword(s):  
Dynamic Surface Control ◽  
Input Delay ◽  
Feedback Systems ◽  
Estimation Errors ◽  
Dynamic Surface ◽  
Performance Control ◽  
Adaptive Fuzzy ◽  
Unknown Control ◽  
Unknown Control Direction ◽  
Control Direction

This paper presents a problem of observer-based adaptive fuzzy predefined performance control of a class of nonlinear pure-feedback systems with input delay and unknown control direction. Compared with the existing research, a novel predefined performance controller is proposed, which relaxes the assumption that the initial error is known. In addition, it is difficult to design the controllers due to input delay and nonaffine properties of the pure-feedback systems, which can be simplified by Pade approximation. Moreover, dynamic surface control and Nussbaum functions are applied to overcome the calculation explosion caused by repeated differentiations and unknown control direction, respectively. Based on the above methods, an adaptive fuzzy predefined performance controller is proposed, and it is proved that all the signals of a closed-loop system are semiglobally uniformly ultimately bounded (SGUUB). The tracking errors converge within a predefined range, while the observer estimation errors converge within a small zero region. Finally, the simulation results demonstrate the effectiveness of the proposed control system.

scholarly journals Adaptive tracking control for uncertain nonlinear systems subject to unknown control coefficients, state constraints, and input saturation

2021 ◽  
Author(s):  
Chunxiao Wang ◽  
Lu Qi ◽  
Yan Zhao ◽  
Jiali Yu
Keyword(s):  
Tracking Control ◽  
State Constraints ◽  
Input Saturation ◽  
Approximation Error ◽  
Tracking Performance ◽  
Dynamic Surface ◽  
Unknown Control Coefficients ◽  
Unknown Control ◽  
Control Direction ◽  
Control Coefficients

Abstract This article is committed to studying the tracking control problem for a class of uncertain nonlinear system with unknown control coefficients. The system is subject to full state constraints, input saturation constraint, and external disturbances simultaneously. By introducing a hyperbolic tangent function to approximate the saturated input function, the sharp corner caused by the input saturation is avoided. In the meanwhile, an auxiliary system is constructed to compensate the resulting approximation error. By using the barrier Lyapunov function (BLF) based adaptive backsteping control, the Nussbaum-type adaptive controllers are constructed for the augmented system with unknown control direction. It not only ensures the system states are always within the constrained range, but also guarantees the tracking performance of the system, no matter whether the control direction of the system is known or not. Meanwhile, dynamic surface control (DSC) is used in the controller design, which avoids ”computation explosion” caused by the repeated derivation of virtual control law. Aiming at the nonparametric uncertainty of the system, a common adaptive law is designed by combining the unknown constant bounds of the external disturbance with the error term caused by input saturation estimation. It improves the tracking performance of the system and reduces the burden of the controller greatly. Finally, a simulation example is given to demonstrate the effectiveness of the proposed control scheme in three scenarios.

ADAPTIVE FUZZY TRACKING CONTROL FOR A CLASS OF PERTURBED NONLINEAR TIME-VARYING DELAYS SYSTEMS WITH UNKNOWN CONTROL DIRECTION

2013 ◽  
Vol 21 (04) ◽  
pp. 497-531 ◽  
Author(s):  
HONGYUN YUE ◽  
JUNMIN LI
Keyword(s):  
Controller Design ◽  
Adaptive Fuzzy Control ◽  
Small Neighborhood ◽  
Design Procedure ◽  
Time Varying ◽  
Adaptive Fuzzy ◽  
Control Scheme ◽  
Unknown Control ◽  
Unknown Control Direction ◽  
Control Direction

An adaptive fuzzy control scheme with only one adjusted parameter is developed for a class of nonlinear time-varying delays systems. Three kinds of uncertainties: time-varying delays, control directions, and nonlinear functions are all assumed to be completely unknown, which is different from the previous work. During the controller design procedure, appropriate Lyapunov-Krasovskii functionals are used to compensate the unknown time-varying delays terms and the Nussbaum-type function is used to detect the unknown control direction. It is proved that the proposed controller guarantees that all the signals in the closed-loop system are bounded and the tracking errors converge to a small neighborhood around zero. The two main advantages of the developed scheme are that (i) by combining the appropriate Lyapunov-Krasovskii functionals with the Nussbaum-gain technique, the control scheme is proposed for a class of nonlinear time-varying delays systems with unknown control directions, (ii) only one parameter needs to be adjusted online in controller design procedure, which reduces the computational burden greatly. Finally, two examples are used to show the effectiveness of the proposed approach.

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