Garrett E Swierenga

US Patent:

51901110, Mar 2, 1993

Filed:

Jun 3, 1991

Appl. No.:

7/709237

Inventors:

Steven C. Young - Lancaster PA
Bradley A. Nielsen - New Holland PA
James W. Macqueene - Willowbrook IL
Garrett E. Swierenga - Westmont IL

Assignee:

Ford New Holland, Inc. - New Holland PA

International Classification:

A01B 63112

US Classification:

172 7

Abstract:

An automatic draft control for controlling the position of a tractor-mounted hitch includes a slip override circuit responsive to a wheel signal for modifying a hitch position command so that hitch draft is reduced by raising the hitch when the degree of tractor wheel slip exceeds a threshold value. The slip is determined by measuring theoretical (no-slip) ground speed with a sensor which senses the rate of rotation of the tractor rear axle, and measuring true ground speed with a radar unit mounted on one side of the tractor. Because the radar unit does not indicate the speed of the center line of the tractor as it turns, the slip signal is prevented from modifying the hitch position command if the hitch is raised since the hitch is usually raised when turning and there is no need to modify the position command with the slip signal when the hitch is raised. The true ground speed is automatically and repeatedly divided by the rate of rotation of the tractor rear axle when conditions are such that wheel slippage is unlikely. The multiple divisions produce plural indications of a correction factor.