End effector design and control
End effector design and control
The design, analysis and control of a dextrous end-effector used for grasping rigid objects in an unsaturated environment has been investigated. The end-effector is a non-anthropomorphic hand, consisting of three articulated fingers, placed symmetrically on a circular base. The finger is not tendon-operated but has a sophisticated linkage mechanism which results in three degrees of freedom in the task space. The advantages are high reliability, low friction in the driving sense, no compliance and no back driving.
Analytical and numerical solutions are developed to solve the kinematics of the end-effector. Inverse kinematics is solved in several methods: polynomial, analytically and numerically derived Jacobian matrix, and neutral network. The derived solutions can be applied to manipulators with high non-linear kinematic equations. An evaluation and comparison of the approaches in precision shows that the polynomial approach is the best.
A grasping approach is proposed based on classification of objects into different shape and size, to form grasp primitives as spherical, cylindrical, circular, and having two parallel sides grasps. These primitives provide force-closure grasps either using the fingertips or an envelope grasping. A set of finger inputs is provided for control system to arrange each grasp primitive using the inverse kinematic solutions. For grasping objects with unknown width or diameter, the input data are provided as functions of the diameter or the width of object. These are fitted to quadratic functions in order to trace a suitable trajectory and to complete the grasp. A useful approach is also proposed for envelope grasping of either regular or irregular objects. The finger configurations are simulated for the grasp primitives.
To grasp an object firstly the end-effector is aligned centrally above the object, then the object shape is recognised and a suitable grasp primitive is selected. Finally a position/force control approach is executed. Several control strategies are discussed and the Proportional-Integrative controllers are proposed for the position/force control of the end-effector under maximum force strategy for grasping rigid objects in unstructured environment. Simulated results show a satisfactory performance of the control system.
University of Southampton
Fateh, Mohammed Mahdi
9c54582a-c921-4394-9247-a421cb202b40
2001
Fateh, Mohammed Mahdi
9c54582a-c921-4394-9247-a421cb202b40
Fateh, Mohammed Mahdi
(2001)
End effector design and control.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The design, analysis and control of a dextrous end-effector used for grasping rigid objects in an unsaturated environment has been investigated. The end-effector is a non-anthropomorphic hand, consisting of three articulated fingers, placed symmetrically on a circular base. The finger is not tendon-operated but has a sophisticated linkage mechanism which results in three degrees of freedom in the task space. The advantages are high reliability, low friction in the driving sense, no compliance and no back driving.
Analytical and numerical solutions are developed to solve the kinematics of the end-effector. Inverse kinematics is solved in several methods: polynomial, analytically and numerically derived Jacobian matrix, and neutral network. The derived solutions can be applied to manipulators with high non-linear kinematic equations. An evaluation and comparison of the approaches in precision shows that the polynomial approach is the best.
A grasping approach is proposed based on classification of objects into different shape and size, to form grasp primitives as spherical, cylindrical, circular, and having two parallel sides grasps. These primitives provide force-closure grasps either using the fingertips or an envelope grasping. A set of finger inputs is provided for control system to arrange each grasp primitive using the inverse kinematic solutions. For grasping objects with unknown width or diameter, the input data are provided as functions of the diameter or the width of object. These are fitted to quadratic functions in order to trace a suitable trajectory and to complete the grasp. A useful approach is also proposed for envelope grasping of either regular or irregular objects. The finger configurations are simulated for the grasp primitives.
To grasp an object firstly the end-effector is aligned centrally above the object, then the object shape is recognised and a suitable grasp primitive is selected. Finally a position/force control approach is executed. Several control strategies are discussed and the Proportional-Integrative controllers are proposed for the position/force control of the end-effector under maximum force strategy for grasping rigid objects in unstructured environment. Simulated results show a satisfactory performance of the control system.
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Published date: 2001
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Local EPrints ID: 464368
URI: http://eprints.soton.ac.uk/id/eprint/464368
PURE UUID: 016cd393-fefe-4a51-9fba-be2cf3a3424e
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Date deposited: 04 Jul 2022 22:21
Last modified: 16 Mar 2024 19:27
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Author:
Mohammed Mahdi Fateh
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