Impedance Control for Flexible Robot Manipulators Using an End-Effector Trajectory Tracking Control Method.

Purpose This paper aims to propose a dynamic trajectory-tracking control method for robotic transcranial magnetic stimulation (TMS), based on force sensors, which follows the dynamic movement of the patient’s head during treatment. Design/methodology/approach First, end-effector gravity compensation methods based on kinematics and back-propagation (BP) neural networks are presented and compared. Second, a dynamic trajectory-tracking method is tested using force/position hybrid control. Finally, an adaptive proportional-derivative (PD) controller is adopted to make pose corrections. All the methods are designed for robotic TMS systems. Findings The gravity compensation method, based on BP neural networks for end-effectors, is proposed due to the different zero drifts in different sensors’ postures, modeling errors in the kinematics and the effects of other uncertain factors on the accuracy of gravity compensation. Results indicate that accuracy is improved using this method and the computing load is significantly reduced. The pose correction of the robotic manipulator can be achieved using an adaptive PD hybrid force/position controller. Originality/value A BP neural network-based gravity compensation method is developed and compared with traditional kinematic methods. The adaptive PD control strategy is designed to make the necessary pose corrections more effectively. The proposed methods are verified on a robotic TMS system. Experimental results indicate that the system is effective and flexible for the dynamic trajectory-tracking control of manipulator applications.

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Adaptive Fast Nonsingular Fixed-Time Tracking Control for Robot Manipulators

Complexity ◽

10.1155/2021/6629993 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Huihui Pan ◽

Guangming Zhang

Keyword(s):

Trajectory Tracking ◽

Tracking Control ◽

Control Method ◽

Sliding Mode ◽

Robot Manipulators ◽

Fixed Time ◽

Convergence Time ◽

Trajectory Tracking Control ◽

Uncertain Dynamics ◽

Adaptive Technique

This paper studies the fixed-time trajectory tracking control problem of robot manipulators in the presence of uncertain dynamics and external disturbances. First, a novel nonsingular fixed-time sliding mode surface is presented, which can ensure that the convergence time of the suggested surface is bounded regardless of the initial states. Subsequently, a novel fast nonsingular fixed-time sliding mode control (NFNFSMC) is developed so that the closed-loop system is fixed-time convergent to the equilibrium. By applying the proposed NFNFSMC method and the adaptive technique, a novel adaptive nonsingular fixed-time control scheme is proposed, which can guarantee fast fixed-time convergence of the tracking errors to small regions around the origin. With the proposed control method, the lumped disturbance is compensated by the adaptive technique, whose prior information about the upper bound is not needed. The fixed-time stability of the trajectory tracking control under the proposed controller is proved by the Lyapunov stability theory. Finally, corresponding simulations are given to illustrate the validity and superiority of the proposed control approach.

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Trajectory Tracking Control of Robot Manipulators Based on U-Model

Mathematical Problems in Engineering ◽

10.1155/2020/8314202 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Xianghua Ma ◽

Yang Zhao ◽

Yiqun Di

Keyword(s):

Trajectory Tracking ◽

Tracking Control ◽

Control Algorithm ◽

Control Method ◽

Robot Manipulators ◽

Computation Time ◽

Initial State ◽

Trajectory Tracking Control ◽

Model Method ◽

Trajectory Tracking Controller

A new trajectory tracking control method based on the U-model is proposed to improve the trajectory tacking speed of robot manipulators. The U-model method is introduced to relieve the requirement of the dynamic mathematical model and make the design of trajectory tracking controller of robot manipulators simpler. To further improve the trajectory tacking speed, an improved iterative learning control algorithm is used to suppress the influence of the initial state error with less computation time. Experimental results show that the proposed control method is effective and practical for the trajectory tracking control of robot manipulators, especially with a high real-time requirement.

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Trajectory Tracking Control of Flexible Manipulators Considering Modeling Discrepancy

Dynamic Systems and Control, Parts A and B ◽

10.1115/imece2005-80370 ◽

2005 ◽

Cited By ~ 1

Author(s):

S. Kilicaslan ◽

S. K. Ider ◽

M. K. Ozgoren

Keyword(s):

Tracking Control ◽

Control Method ◽

Feedback Stabilization ◽

Flexible Manipulators ◽

Flexible Robot ◽

Equilibrium Equations ◽

Trajectory Tracking Control ◽

Elastic Deformations ◽

End Effector ◽

Joint Variable

A new method is proposed for the end-effector motion control of flexible manipulators. The dynamic equations of flexible robot manipulators are partitioned as pseudostatic equilibrium equations and deviations from them. The pseudostatic equilibrium considered here is defined as a hypothetical state where the end-effector motion variables have their desired values while the elastic deformations are instantaneously constant. Then, the control torques for the pseudostatic equilibrium are computed and the feedback stabilization of the deviation equations is achieved using strain gage and joint variable or tip point variable measurements. A planar two link robot with flexible forearm is taken into consideration for demonstration of the method. The elasticity of the forearm is approximately described by the first two modes and a controller is designed using this two-mode model. Furthermore, in order to investigate the effects of modeling discrepancies, a “submodel controller” is considered using a model that has only the first mode. The performances of these two controllers are compared by means of simulations. It is observed that the proposed control method does not seem to be sensitive to the number of modes included in the model of the manipulator.

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Robust finite-time trajectory tracking control for a space manipulator with parametric uncertainties and external disturbances

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/09544100211014754 ◽

2021 ◽

pp. 095441002110147

Author(s):

Qijia Yao

Keyword(s):

Trajectory Tracking ◽

Finite Time ◽

Tracking Control ◽

Disturbance Observer ◽

Control Method ◽

Parametric Uncertainties ◽

External Disturbances ◽

Trajectory Tracking Control ◽

Space Manipulator ◽

Tracking Controller

Space manipulator is considered as one of the most promising technologies for future space activities owing to its important role in various on-orbit serving missions. In this study, a robust finite-time tracking control method is proposed for the rapid and accurate trajectory tracking control of an attitude-controlled free-flying space manipulator in the presence of parametric uncertainties and external disturbances. First, a baseline finite-time tracking controller is designed to track the desired position of the space manipulator based on the homogeneous method. Then, a finite-time disturbance observer is designed to accurately estimate the lumped uncertainties. Finally, a robust finite-time tracking controller is developed by integrating the baseline finite-time tracking controller with the finite-time disturbance observer. Rigorous theoretical analysis for the global finite-time stability of the whole closed-loop system is provided. The proposed robust finite-time tracking controller has a relatively simple structure and can guarantee the position and velocity tracking errors converge to zero in finite time even subject to lumped uncertainties. To the best of the authors’ knowledge, there are really limited existing controllers can achieve such excellent performance under the same conditions. Numerical simulations illustrate the effectiveness and superiority of the proposed control method.

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