Modal characterization with nonlinear behaviors of a two-link flexible manipulator

This paper aims to explore the convergence of per capita carbon and ecological footprints in G7 countries during 1961–2016. For this purpose, we propose a new unit root test in the panel setting–the panel Fourier threshold unit root test. This test takes into consideration both multiple smooth structural changes and nonlinearity. According to the literature, the power of the nonlinear unit root tests is reduced in the case of ignoring structural breaks. Therefore, we expect to get more reliable empirical findings by utilizing this methodology. The empirical results of this paper show that these series have nonlinear behaviors for the period 1961–2016. Furthermore, they demonstrate that the absolute convergence hypothesis is valid in G7 countries for both regimes. Thus, governments can conduct common environmental policies, including international climate summits and agreements, instead of national-based policies to mitigate environmental deterioration in their countries.

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The Study of Dynamic Modeling and Multivariable Feedback Control for Flexible Manipulators with Friction Effect and Terminal Load

Sensors ◽

10.3390/s21041522 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1522

Author(s):

Fuli Zhang ◽

Zhaohui Yuan

Keyword(s):

Dynamic Model ◽

Vibration Suppression ◽

Control Method ◽

Coupling Effect ◽

Flexible Manipulator ◽

Flexible Beam ◽

Robot Dynamics ◽

Joint Friction ◽

Balance Principle ◽

Multivariable Feedback

The flexible manipulato is widely used in the aerospace industry and various other special fields. Control accuracy is affected by the flexibility, joint friction, and terminal load. Therefore, this paper establishes a robot dynamics model under the coupling effect of flexibility, friction, and terminal load, and analyzes and studies its control. First of all, taking the structure of the central rigid body, the flexible beam, and load as the research object, the dynamic model of a flexible manipulator with terminal load is established by using the hypothesis mode and the Lagrange method. Based on the balance principle of the force and moment, the friction under the influence of flexibility and load is recalculated, and the dynamic model of the manipulator is further improved. Secondly, the coupled dynamic system is decomposed and the controller is designed by the multivariable feedback controller. Finally, using MATLAB as the simulation platform, the feasibility of dynamic simulation is verified through simulation comparison. The results show that the vibration amplitude can be reduced with the increase of friction coefficient. As the load increases, the vibration can increase further. The trajectory tracking and vibration suppression of the manipulator are effective under the control method of multi-feedback moment calculation. The research is of great significance to the control of flexible robots under the influence of multiple factors.

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Period-doubling bifurcation analysis and chaos control for load torque using FLC

Complex & Intelligent Systems ◽

10.1007/s40747-021-00276-2 ◽

2021 ◽

Author(s):

Eman Moustafa ◽

Abdel-Azem Sobaih ◽

Belal Abozalam ◽

Amged Sayed A. Mahmoud

Keyword(s):

Floquet Theory ◽

Chaos Control ◽

Fuzzy Logic Controller ◽

Chaotic Behavior ◽

Period Doubling ◽

Parameter Variation ◽

Period Doubling Bifurcation ◽

Load Torque ◽

Nonlinear Behaviors ◽

Scientific Fields

AbstractChaotic phenomena are observed in several practical and scientific fields; however, the chaos is harmful to systems as they can lead them to be unstable. Consequently, the purpose of this study is to analyze the bifurcation of permanent magnet direct current (PMDC) motor and develop a controller that can suppress chaotic behavior resulted from parameter variation such as the loading effect. The nonlinear behaviors of PMDC motors were investigated by time-domain waveform, phase portrait, and Floquet theory. By varying the load torque, a period-doubling bifurcation appeared which in turn led to chaotic behavior in the system. So, a fuzzy logic controller and developing the Floquet theory techniques are applied to eliminate the bifurcation and the chaos effects. The controller is used to enhance the performance of the system by getting a faster response without overshoot or oscillation, moreover, tends to reduce the steady-state error while maintaining its stability. The simulation results emphasize that fuzzy control provides better performance than that obtained from the other controller.

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Modeling and approximate analytical solution of nonlinear behaviors for a self-excited electrostatic actuator

Nonlinear Dynamics ◽

10.1007/s11071-020-06157-6 ◽

2021 ◽

Author(s):

Yangsheng Zhu ◽

Zhiwei Liu ◽

Mingjing Qi ◽

Xiaojun Yan

Keyword(s):

Analytical Solution ◽

Approximate Analytical Solution ◽

Electrostatic Actuator ◽

Nonlinear Behaviors

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Fuzzy nonsingular terminal sliding mode control for rigid flexible manipulator

Journal of Physics Conference Series ◽

10.1088/1742-6596/1952/3/032013 ◽

2021 ◽

Vol 1952 (3) ◽

pp. 032013

Author(s):

Lisha Xu ◽

Xiaoshan Qian ◽

Chong Lin

Keyword(s):

Sliding Mode Control ◽

Sliding Mode ◽

Flexible Manipulator ◽

Terminal Sliding Mode Control ◽

Terminal Sliding Mode ◽

Mode Control ◽

Nonsingular Terminal Sliding Mode

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Sampled-data extended state observer-based backstepping control of two-link flexible manipulator

Transactions of the Institute of Measurement and Control ◽

10.1177/0142331219832954 ◽

2019 ◽

Vol 41 (13) ◽

pp. 3581-3599 ◽

Cited By ~ 3

Author(s):

Umesh Kumar Sahu ◽

Bidyadhar Subudhi ◽

Dipti Patra

Keyword(s):

Control Strategies ◽

Estimation Error ◽

Experimental Studies ◽

State Observer ◽

Lyapunov Theory ◽

Extended State Observer ◽

Flexible Manipulator ◽

Sampled Data ◽

Extended State ◽

Model Uncertainties

Currently, space robots such as planetary robots and flexible-link manipulators (FLMs) are finding specific applications to reduce the cost of launching. However, the structural flexible nature of their arms and joints leads to errors in tip positioning owing to tip deflection. The internal model uncertainties and disturbance are the key challenges in the development of control strategies for tip-tracking of FLMs. To deal with these challenges, we design a tip-tracking controller for a two-link flexible manipulator (TLFM) by developing a sampled-data extended state observer (SD-ESO). It is designed to reconstruct uncertain parameters for accurate tip-tracking control of a TLFM. Finally, a backstepping (BS) controller is designed to attenuate the estimation error and other bounded disturbances. Convergence and stability of the proposed control system are investigated by using Lyapunov theory. The benefits (control performance and robustness) of the proposed SD-ESO-based BS controller are compared with other similar approaches by pursuing both simulation and experimental studies. It is observed from the results obtained that SD-ESO-based BS Controller effectively compensates the deviation in tip-tracking performance of TLFM due to non-minimum phase behavior and model uncertainties with an improved transient response.

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