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Gimbal System for Natural Wrist Motion for a Manipulator

IP.com Disclosure Number: IPCOM000083097D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 91K

Publishing Venue

IBM

Related People

Folchi, G: AUTHOR [+3]

Abstract

This is a gimbal system with differential gears providing a natural wrist motion. It is very compact in size and delivers a high-force output for use with a computer controlled manipulator.

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Gimbal System for Natural Wrist Motion for a Manipulator

This is a gimbal system with differential gears providing a natural wrist motion. It is very compact in size and delivers a high-force output for use with a computer controlled manipulator.

Referring to Fig. 1, which is a fragmentary view of a structure, a finger assembly gimbal linkage, L, of a computer controlled manipulator system is rigidly fastened to gear A, with a fragment of gripper GR and fingers FI holding load LD. Gear A rotates freely with respect to cross shaft MN. When gear A rotates, gimbal L, one arm of which is shown, and gear A change pitch angle Theta. If cross shaft MN rotates on its vertical axis YY, the angular position of gimbal L changes in the yaw direction, e.g., angle phi in Fig. 1.

Fig. 2 is a sectional front elevation of the system of Fig. 1. Gears A, B, C, and D form a differential gear set. They rotate freely with respect to the cross axes MN. Gears E and F fasten rigidly to gears B and D, respectively. Motor U drives gear E and motor W drives gear F. Gears A and C support the gimbal assembly of the computer controlled manipulator system. Gear A connects rigidly to arm L1 of gimbal L. However, gear C is not fastened to arm L2 of gimbal L. Bearings are installed between arm L2 and gear C to allow rotation between them. Operating Principles of Pitch Direction

If motors U and W rotate in opposite directions at the same speed, gear A and gimbal L have pitch motion only about the X axis but shaft MN does not move. To assure that there is no speed error between motors U and W, clutch H is engaged to lock the position of shaft MN. (Disengaging of clutch H allows shaft MN to rotate with respect to ground). The greatest advantage in this gimbal system is that both motors U and W can share the external load. If the load is tau in-1b, two small motors with a deliverable torque of 1/2 tau(L) in-1b can be used. (In a conventional system, a motor of tau(L)in-1b must be used). If one motor fails in the proposed system, the system functions without detrimental effect to the total system. Operating Principles of Yaw Direction

If motors U and W rotate at the same speed and in the same direction, gears E and F and B and D turn shaft MN carrying gimbal L and gripper GR about the vertical axis YY. There is no relative motion between gear A and clutch G. Clutch G engages gimbal arm L1 to lock gear A to shaft MN, to assure that there will be no speed difference between motors U and W. An external load of tau in- 1b is shared by motors U and W so each motor delivers 1/2 tau in-1b. Operating Principles of General Motions

Both clutches H and G disengage to release the shaft MN with respect to the manipulator arm and to unlock gear A from shaft MN, respectively. displacement of gear D is defined as beta, the positive direction is chosen when they are rotating in the counterclockwise direction. (alpha, beta, theta and phi are defined in Figs. 1 and...