scholarly journals Robust Finite-Time Tracking Control for Robotic Manipulators with Time Delay Estimation

Mathematics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 165
Author(s):  
Tie Zhang ◽  
Aimin Zhang
Keyword(s):  
Time Delay ◽  
Finite Time ◽  
Robotic Manipulators ◽  
High Gain ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Closed Loop System ◽  
External Disturbances ◽  
Estimation Errors ◽  
Theorem Proof

In this study, a robust H∞ finite-time tracking controller is proposed for robotic manipulators based on time delay estimation. In this controller, there is no need to know the dynamics of robots, so it is quite simple. The high-gain observer is employed to estimate the joint velocities, which makes it much lower in cost. The theorem proof shows that the closed-loop system is finite-time stable and has a L2 gain that is less than or equal to γ, which shows high accuracy and strong robustness to estimation errors and external disturbances. Simulations on a two-link robot illustrate the effectiveness and advantages of the proposed controllers.

scholarly journals Underwater Acoustic Time Delay Estimation Based on Envelope Differences of Correlation Functions

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1259 ◽  
Author(s):  
Guodong Li ◽  
Jinsong Wu ◽  
Taolin Tang ◽  
Zhixin Chen ◽  
Jun Chen ◽  
...  
Keyword(s):  
Time Delay ◽  
Correlation Functions ◽  
Estimation Method ◽  
Digital Signal ◽  
Low Complexity ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Estimation Errors ◽  
Underwater Acoustic ◽  
Amplitude Fluctuations

This paper proposes underwater acoustic time delay estimation based on the envelope differences of correlation functions (EDCF), which mitigates the delay estimation errors introduced by the amplitude fluctuations of the correlation function envelopes in the traditional correlation methods (CM). The performance of the proposed delay estimation method under different time values was analyzed, and the optimal difference time values are given. To overcome the influences of digital signal sampling intervals on time delay estimation, a digital time delay estimation approach with low complexity and high accuracy is proposed. The performance of the proposed time delay estimation was analyzed in underwater multipath channels. Finally, the accuracy of the delay estimation using this proposed method was demonstrated by experiments.

Passive and active rehabilitation control of human upper-limb exoskeleton robot with dynamic uncertainties

Robotica ◽  
2018 ◽  
Vol 36 (11) ◽  
pp. 1757-1779 ◽  
Author(s):  
Brahim Brahmi ◽  
Maarouf Saad ◽  
Cristobal Ochoa Luna ◽  
Philippe S. Archambault ◽  
Mohammad H. Rahman
Keyword(s):  
Time Delay ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Stability And Convergence ◽  
External Disturbances ◽  
Upper Limb Exoskeleton ◽  
Uncertain Dynamics ◽  
Exoskeleton Robot ◽  
Active Rehabilitation ◽  
The Impact

SUMMARYThis paper investigates the passive and active control strategies to provide a physical assistance and rehabilitation by a 7-DOF exoskeleton robot with nonlinear uncertain dynamics and unknown bounded external disturbances due to the robot user's physiological characteristics. An Integral backstepping controller incorporated with Time Delay Estimation (BITDE) is used, which permits the exoskeleton robot to achieve the desired performance of working under the mentioned uncertainties constraints. Time Delay Estimation (TDE) is employed to estimate the nonlinear uncertain dynamics of the robot and the unknown disturbances. To overcome the limitation of the time delay error inherent of the TDE approach, a recursive algorithm is used to further reduce its effect. The integral action is employed to decrease the impact of the unmodeled dynamics. Besides, the Damped Least Square method is introduced to estimate the desired movement intention of the subject with the objective to provide active rehabilitation. The controller scheme is to ensure that the robot system performs passive and active rehabilitation exercises with a high level of tracking accuracy and robustness, despite the unknown dynamics of the exoskeleton robot and the presence of unknown bounded disturbances. The design, stability, and convergence analysis are formulated and proven based on the Lyapunov–Krasovskii functional theory. Experimental results with healthy subjects, using a virtual environment, show the feasibility, and ease of implementation of the control scheme. Its robustness and flexibility to deal with parameter variations due to the unknown external disturbances are also shown.

Model-free robust finite-time force tracking control for piezoelectric actuators using time-delay estimation with adaptive fuzzy compensator

2019 ◽  
Vol 42 (3) ◽  
pp. 351-364
Author(s):  
Shengzheng Kang ◽  
Hongtao Wu ◽  
Xiaolong Yang ◽  
Yao Li ◽  
Yaoyao Wang
Keyword(s):  
Time Delay ◽  
Finite Time ◽  
Sliding Mode ◽  
Piezoelectric Actuators ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Terminal Sliding Mode ◽  
Adaptive Fuzzy ◽  
Model Free ◽  
Force Tracking

A robust and practical force control system is crucial to the sensitive piezo-driven micromanipulation applications. This paper presents a new model-free robust finite-time force tracking controller for piezoelectric actuators (PEAs). The proposed controller composes of three intuitive terms: (1) a time-delay estimation (TDE) term that eliminates the requirement of detailed information about the PEA system, realizing model-free control; (2) a fast integral terminal sliding mode-based desired error dynamics injection term that ensures fast convergence and high tracking precision; (3) a correcting term based on adaptive fuzzy logic system that compensates for TDE errors caused by discontinuous nonlinearities and improves the robustness of the system. Force differential signal used in the controller is estimated online by a force state estimator. Stability of the closed-loop system and finite-time convergence are analyzed in theory. Comparative experiments are carried out on a PEA system with two superposed PEAs. Results show that the proposed control strategy has faster convergence, higher tracking accuracy and stronger robustness compared with the traditional TDE-based force controllers.

scholarly journals Model-free Control of Manipulator in Task Space Containing Mismatched Uncertainty

2021 ◽  
Author(s):  
Xiaohui Yang ◽  
Zhenghong Xu ◽  
Wenjie Zhang ◽  
Wei Zhang ◽  
Peter Xiaoping Liu
Keyword(s):  
Time Delay ◽  
Control Method ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Task Space ◽  
Estimation Errors ◽  
Trajectory Tracking Control ◽  
Model Free ◽  
Model Free Control ◽  
Mismatched Uncertainty

Abstract In this paper, a novel trajectory tracking control method for manipulator task space containing mismatched uncertainty is proposed. This paper considers the mismatched uncertainty that exists in the signal conversion between joint space and task space in the robotic arm system. The time delay estimation is employed to approximate the dynamic and kinematic parameters of the system to achieve model-free control. The time delay estimation errors is treated as part of the system disturbances and a disturbance observer based on an auxiliary control system capable of estimating both matched and mismatched disturbances is designed, which does not require additional design of adaptive laws to compensate for disturbances or upper bounds on the derivatives of disturbances. We transform the control error by a prescribed performance function to accomplish transient control of the error, and design a fast terminal sliding surface for the virtual control variables based on the backstepping design method to improve the convergence speed of the controller. Based on the Lyapunov criterion, the closedloop stability of the whole system is demonstrated. The feasibility and superiority of the method in this paper is demonstrated by numerical simulation compared with other control methods.

A practical time-delay control scheme for aerial manipulators

2020 ◽  
pp. 095965182094651
Author(s):  
Yadong Ding ◽  
Yaoyao Wang ◽  
Bai Chen
Keyword(s):  
Time Delay ◽  
Unmanned Aerial Vehicles ◽  
Closed Loop ◽  
Sliding Mode ◽  
Robotic Manipulators ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Terminal Sliding Mode ◽  
Nonsingular Terminal Sliding Mode ◽  
Control Scheme

In recent years, aerial manipulators consist of unmanned aerial vehicles and robotic manipulators have been widely utilized in aerial operations. The complex dynamic coupling effects between unmanned aerial vehicles and robotic manipulators will bring some issues to the motion control. Therefore, the article proposes a new control scheme for aerial manipulators. The proposed method includes three elements, that is, time-delay estimation, backstepping design, and nonsingular terminal sliding mode. The time-delay estimation technique is adopted to estimate the complex system dynamics and to bring a model-free feature of the system. With the backstepping design, the proposed control strategy can ensure the asymptotic stability of the closed-loop system by recursive procedure. To deal with the unmodelling dynamics and disturbances, and to assure finite-time convergence of the system states, the nonsingular terminal sliding mode is adopted. By combining three elements, the tracking performance of aerial manipulators is improved under unmodelling dynamics and disturbances. Global stability of closed-loop control system is analyzed using Lyapunov stability theory. Finally, comparative simulations are conducted, and the results show that the proposed controller has better performance than a conventional proportional–derivative controller or a nonsingular terminal sliding mode controller.

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