Windrower header speed control

Details Windrower header speed control Windrower header speed control

1999-03-24

2001-01-02

Pezzuto, Robert E. (Department: 3671)

Harvesters

Motorized harvester

With condition-responsive operation

C056S01020G, C056S011100

Utility Patent

active

06167685

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to control of the speed of the header of a windrower. More particularly, the invention provides for microprocessor control of header speed based on both the speed and the acceleration or rate of change in header speed.
BACKGROUND OF THE INVENTION
The header of a windrower or mower/conditioner typically includes a cutter which may take the form of sickle-bar or a plurality of disk cutter knives for cutting a crop material such as hay. The cut crop is then passed through conditioning rolls after which it is deposited in a windrow on a field. Windrowers having the disk type cutters present a problem in that when the windrower moves from an area having heavy crop to an area having light or no crop, such as when the windrower moves from the area of crop into the headlands of a field, the lightened load permits a considerable increase in header speed. An operator may rapidly turn the windrower in the headlands so that it is ready to reenter the crop area rather quickly to begin cutting the next swath. However, if the header speed is too high, the knives may blow the crop material away from the cutting mechanism and the operator must wait until the over speed has been corrected before moving back into the crop area. Therefore, it is desirable that the over speed condition be corrected as rapidly as possible, not only to save operator time and reduce operator irritation, but also reduce fuel consumption and wear on the windrower.
Currently, header speed is sensed to develop a control signal tending to keep the header speed within a window or range centered on a speed selected by the operator via a control console or panel. Since no control signal is developed until the sensed speed falls outside the window, there is a considerable delay in correcting an over speed condition. In some windrowers the output of a proportional hydraulic pump drives the header drive motors and the response time of the pump adds to the delay.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the problems of the prior art by providing a header speed control system which responds more quickly than the prior art to changes in header speed.
A further object of the invention is to provide a closed loop header speed control system wherein the control signal for controlling the header to a set point speed is determined by both header speed and header acceleration.
Another object of the invention is to provide a header speed control system for controlling the speed of a header in a windrower to a set point speed, the system including a source of variable drive power producing a variable power output for driving the header, a header speed sensor for sensing the speed of the header and a controller responsive to the header speed sensor for developing a control signal to control the power output of the source of variable drive power, the control signal being a function of header speed and header acceleration.
According to the invention, a system for controlling the header speed of a windrower to a set point includes a proportional or variable displacement pump producing a variable outflow of hydraulic fluid for driving the header via at least one hydraulic motor, the system being characterized in that the pump is driven by a pulse width modulated (PWM) signal having a duty cycle that is dependent on the speed and the acceleration of the header. When the header speed falls outside a window or range of speeds centered at the set point, header speed is used to modify the duty cycle of the PWM signal and bring the header speed back within the window. In addition, if the header includes a disk type cutter, the duty cycle of the PWM signal is decremented if the acceleration of the header exceeds a threshold and the header includes disk type cutters. This is done even though the header speed is within the window.
Other objects and advantages of the invention will become obvious upon consideration of the following description and the accompanying drawings.


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