Browse Prior Art Database

Force Accommodating Moves in Manipulators

IP.com Disclosure Number: IPCOM000089392D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 30K

Publishing Venue

IBM

Related People

Will, PM: AUTHOR

Abstract

Force-accommodating moves arise when it is required to move in a direction subject to a constraint in a second direction. For example, inserting a pin in a hole requires a putting down movement to insert it, but this also requires the freedom or accommodation in another plane to allow for axial misalignment. The general statement of the problem allows arbitrary primary movements and arbitrary secondary movements which, in turn, involve much computation, often to be performed in real time, to resolve the forces encountered in the primary direction into components in the directions which are under computer control. This general problem has been attacked by others, but the solutions are necessarily slow and require substantial computer hardware.

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Force Accommodating Moves in Manipulators

Force-accommodating moves arise when it is required to move in a direction subject to a constraint in a second direction. For example, inserting a pin in a hole requires a putting down movement to insert it, but this also requires the freedom or accommodation in another plane to allow for axial misalignment. The general statement of the problem allows arbitrary primary movements and arbitrary secondary movements which, in turn, involve much computation, often to be performed in real time, to resolve the forces encountered in the primary direction into components in the directions which are under computer control. This general problem has been attacked by others, but the solutions are necessarily slow and require substantial computer hardware.

Techniques are described for implementing a force-controlled move with little computation by utilizing the facts that the sensors are placed at the base of the fingers and the primary force is measured by a single sensor.

In the figures, a manipulator is illustrated by an arm 10 having fingers 12 rotated on gimbal 14. Sensors 16 are placed at the base of the manipulator fingers or gripper, such as shown in U.S. Patent 3,948,093. These sense forces in a cartesian geometric frame (x,y,z) are centered at the base of the fingers.

The wrist motion in space is generally orthogonal or axial relative to the motion of the primary joint. This wrist motion is illustrated by the arrow 18 on gimbal 14, and the motion of the primary joint is indicated by the arrow 20.

Because of the use of cartesian joints, motion of any extremity of the manipulator in any plane can be accomplished by simple interpolation algorithms in joint space, i.e., for a given grippe...