Adaptive admittance control of a robot manipulator under task space constraint

Author(s):  
Keng Peng Tee ◽  
Rui Yan ◽  
Haizhou Li
2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Xichang Liang ◽  
Yi Wan ◽  
Chengrui Zhang

To improve the tracking precision of robot manipulators’ end-effector with uncertain kinematics and dynamics in the task space, a new control method is proposed. The controller is based on time delay estimation and combines with the nonsingular terminal sliding mode (NTSM) and adaptive fuzzy logic control scheme. Kinematic parameters are not exactly required with the consideration of kinematic uncertainties in the controller. No dynamic models or numerous parameters of the robot manipulator system are required with the use of TDE. Thus, the controller is simple structure and suitable for practical applications. Furthermore, errors caused by time delay estimation are compensated by the adaptive fuzzy nonsingular terminal sliding mode scheme. The simulation is performed on a 2-DOF robot manipulator with three cases in the task space. The results show that the proposed controller provides faster convergence rate and higher tracking precision than TDE based NTSM and improved TDE based NTSM controller.


Author(s):  
Q. Tu ◽  
J. Rastegar

Abstract In a recent article, Rastegar and Tu (1993), the authors presented a method for determining allowable link shapes for robot manipulators once their preferred operational environment is specified. The operational environment may include the preferred size and geometry of the end-effector task space(s), the obstacle and the installation spaces, and the enclosure within which the robot is to operate. In this method, by defining weighted (preferred) distributions for the task and/or obstacle spaces and for the enclosure geometry, weighted allowable manipulator link shapes are determined. In the present study, the developed method is extended to address the problem of optimal geometric design of robot manipulator link shapes. The developed methods are very simple, numeric in nature, readily implemented on computer, and can be classified as being based on the Monte Carlo method. The extension of the present method to the solution of optimal geometric shape synthesis for task and obstacle spaces is discussed. Numerical examples are presented.


Robotica ◽  
2019 ◽  
Vol 38 (10) ◽  
pp. 1807-1823 ◽  
Author(s):  
Leon Žlajpah ◽  
Tadej Petrič

SUMMARYIn this paper, we propose a novel unified framework for virtual guides. The human–robot interaction is based on a virtual robot, which is controlled by the admittance control. The unified framework combines virtual guides, control of the dynamic behavior, and path tracking. Different virtual guides and active constraints can be realized by using dead-zones in the position part of the admittance controller. The proposed algorithm can act in a changing task space and allows selection of the tasks-space and redundant degrees-of-freedom during the task execution. The admittance control algorithm can be implemented either on a velocity or on acceleration level. The proposed framework has been validated by an experiment on a KUKA LWR robot performing the Buzz-Wire task.


Author(s):  
Guanghui Liu ◽  
Bing Han

We propose a cascaded impedance control algorithm based on a virtual dynamics model (VDM) to achieve robust and effective mechanical impedance for a robot interacting with unknown environments. This cascaded controller consists of an internal loop of virtual impedance control based on a VDM and an external loop of impedance reference control. The VDM-based virtual impedance control can achieve the same effect as the conventional admittance control; its intermediate output of force/torque serves as the input for the external loop reference impedance control. Therefore, this cascaded controller shows superior performance by combining the advantages of admittance control and impedance control. We evaluate the controller in multiple-contact experiments on a six-degrees of freedom (6-DOF) industrial robot manipulator. The result shows that under various contact situations such as soft and rigid surfaces and free space, the proposed method can rapidly track the target and effectively maintain stability. In the experiments conducted on the robot in contact with various environments, the proposed control method reduced the steady-state error by more than 20% compared with the conventional admittance control.


PAMM ◽  
2018 ◽  
Vol 18 (1) ◽  
Author(s):  
Dominik Kaserer ◽  
Hubert Gattringer ◽  
Andreas Müller

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