Browse Prior Art Database

Counterbalance Mechanism

IP.com Disclosure Number: IPCOM000040066D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Alewine, NJ: AUTHOR [+3]

Abstract

A technique is described whereby a mechanism counterbalances an overhung load, without significantly adding to rotary inertia, so as to decrease load power positioning requirements. The counterbalance mechanism enables accurate positioning control of linkages moving in a vertical plane about a horizontal axis. It eliminates the need for a powerful motor to overcome gravitational forces, as was required in the prior art. The mechanism is particularly useful in shoulder joint robotic manipulator applications. Typically, robotic control linkages must be designed to accurately and to quickly position arm mechanisms despite gravitational loads, which can vary as a function of the position of the linkages.

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Counterbalance Mechanism

A technique is described whereby a mechanism counterbalances an overhung load, without significantly adding to rotary inertia, so as to decrease load power positioning requirements. The counterbalance mechanism enables accurate positioning control of linkages moving in a vertical plane about a horizontal axis. It eliminates the need for a powerful motor to overcome gravitational forces, as was required in the prior art. The mechanism is particularly useful in shoulder joint robotic manipulator applications. Typically, robotic control linkages must be designed to accurately and to quickly position arm mechanisms despite gravitational loads, which can vary as a function of the position of the linkages. If a controller is tuned to be responsive when the link is horizontal, stability problems can result when the link is vertical. Likewise, if the controller is turned for the vertical position, stability can degrade when the arm is moved to the horizontal position. Adding weight

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to the linkage, so that the mass center moves closer to the rotational axis, increases system inertia and requires an increase in motor power in order to achieve the proper level of performance. The counterbalance mechanism described herein effectively decreases the effect of gravitational loading, without adding to the inertia of the system. The counterbalance mechanism consists of spring 10, as shown in Fig. 1 which when compressed by the increase in load mass to be positioned, is such that the spring force tends to apply movement about fixed pivot 11, to counteract the movement created by the weight of the mass. When the mass is directly above fixed pivot 11, the design of the mechanism provides that fixed pivot 11, pivot 12 and pivot 13 lie along a straight line. In this configuration, there is no moment about fixed pivot 11 fr...