GB2080082A - Agricultural distribution control system - Google Patents

Abstract

In order to regulate the supply of a substance from a moving vehicle, the substance is fed through a variable rate supply gate 1 incorporating apertures 13 the open cross- section of which may be controlled by shutter blades 12 coupled to a ram 9. The position of the ram 9 is determined by an electrical control signal supplied to an electric motor 8 from a control box 3. The control signal is regulated in dependence on the speed of the vehicle and the instantaneous position of the ram 9, as sensed by a ram position sensor 11, to cause the opening of the gate 1 to vary with speed such that the rate of application of the substance is maintained substantially constant as the speed of the vehicle varies over a particular speed range. <IMAGE>

Description

SPECIFICATION Agricultural control system This invention relates to a control system for agricultural purposes, and more particularly to a system for regulating the supply of a substance from a moving vehicle, such as a tractor or an aircraft.

When distributing fertilizer pellets from a moving tractor or aircraft it is usual for the pellets to be fed from a hopper so that, once the size of the hopper opening has been set for a particular rate of application, the fertilizer leaves the tractor or aircraft at a constant rate.

It is important that the fertilizer should be distributed as evenly as possible over the land, and it is therefore essential that the tractor or aircraft is driven at a substantially constant speed during delivery of the fertilizer.

Moreover this constant speed must be equal to the lowest speed which the vehicle would attain when being driven normally over the course. It is an object of this invention to overcome these disadvantages by providing a control system for regulating the supply of the fertilizer so that the vehicle speed can be varied during delivery of the fertilizer.

According to the invention there is provided an agricultural control system for regulating the supply of a substance from a moving vehicle, the system comprising a variable rate supply gate, an electrical actuator for varying the opening of the gate in dependence on an electrical control signal, and control circuitry for supplying the electrical control signal and for regulating that signal in dependence on the speed of the vehicle to cause the opening of the gate to vary with speed such that the rate of application of the substance is maintained substantially constant as the speed of the vehicle varies over a particular speed range.

Preferably the speed range over which the rate of application is maintained substantially constant extends from zero to a maximum application speed. Thus, once the target application rate of the control system has been set, this rate is maintained as the vehicle moves away from rest, as the vehicle moves along the course with its speed varying in the range from zero to the maximum application speed, and as the vehicle subsequently slows down to rest. This reduces the time required to apply fertilizer, as well as other granular or liquid agricultural substances, and ensures a more even application. Furthermore this obviates the arduous task of having to maintain the vehicle speed substantially constant during application.

The supply gate may have a plurality of apertures each of which is provided with a respective shutter for closing off that aperture.

The actuator may comprise an electric motor and a ram arranged to be linearly displaced by the motor in response to receipt of an electrical signal by the motor. Thus, as the speed is decreased or increased, the opening crosssection of the apertures, and hence the application rate, may be descreased or in creased by supplying an electrical signal to the motor for a sufficient length of time to cause the ram to be displaced through the required distance in the appropriate direction.

The system preferably also comprises a ram position sensor for feeding back to the control circuitry a signal indicative of the instantaneous position of the ram. This then enables the control circuitry to determine whether the instantaneous position of the ram corresponds to the instantaneous speed of the vehicle for the target application rate and to apply a correction signal of the required period and polarity where adjustment of the position of the ram is necessitated by a decrease or an increase in the speed of the vehicle.

In order that the invention may be more fully understood, reference will now be made, by way of example, to the accompanying drawing in which the single figure is a schematic diagram of an agricultural control system in accordance with the invention.

The control system illustrated comprises a variable rate supply gate 1 by means of which the rate of application of fertilizer fed by gravity or by force from a moving tractor or aircraft may be controlled, an electrical actuator 2 for the gate 1, and a control box 3 incorporating control circuitry for regulating the opening of the gate 1 in dependence on the forward speed of the tractor or aircraft.

The control box 3 is mounted in front of the driver of the tractor or aircraft and includes a six character display 4 for indicating the vehicle speed or fertilizer application rate, a keyboard 5 for setting the target application rate and target speed, a control knob 6 for causing the display to indicate the target application rate, the target speed, the instantaneous speed or the instantaneous application rate, a warning lamp 7 and a key operated switch 6A. The keyboard 5 incorporates six sets of keys for setting each of the six characters of the display.

The actuator 2 incorporates a reversible electric motor 8 capable of moving a linearly displaceable ram 9 either forwards or backwards on receipt of an electrical signal from the control box 3 by way of a line 10. A ram position sensor 11 is provided in order to sense the position of the ram 9. The ram 9 is coupled to four shutter blades 1 2 for closing off the four apertures 1 3 of the supply gate 1 by means of a control arm 14.

In operation the keyboard 5 is set to a code denoting a target application rate with the knob 6 in the "target application rate" position and is then set to a code denoting a target speed corresponding to the estimated average speed of the vehicle with the knob 6 in the "target speed" position in order to set a target gate opening before the vehicle moves away, after having set the control box 3 in a programming mode by means of the key operated switch 6A. The key is then withdrawn from the switch 6A so as to prevent the target application rate and target speed from being altered during subsequent operation. When the vehicle is moving a pulsed signal proportional to the forward speed of the vehicle obtained from electrical, mechanical or radar speed measuring means (not shown) is supplied to the control box 3 by a line 15.Simultaneously a pulsed signal indicative of the actual position of the ram 9, and hence indicative of the instantaneous opening of the gate 1, obtained from the sensor 11 is supplied to the control box 3 by a line 16. The control circuitry is programmed so as to be capable of converting the signal proportional to the position of the ram 9 to a signal proportional to the total opening crosssection of the gate 1 to operate the display 4, bearing in mind that there is a complex nonlinear relationship between the position of the ram 9 and the opening cross-section of the gate 1 due to the circular shape of the aper tures 13 3 and the concave profile of the shut- ter blades 1 2. The control circuitry is also programmed to convert the speed signal to a signal indicative of the required position of the ram 9 corresponding to that speed utilising the relationships between the speed and the application rate and between the position of the ram and the opening cross-section of the gate.The signal indicative of the required position of the ram is compared with the signal indicative of the actual position of the ram, and, where these differ, a signal having a period proportional to the difference and of the appropriate polarity is supplied to the motor 8 to move the ram 9 either backwards or forwards by the appropriate amount so that the shutter blades 1 2 are maintained at all times in the appropriate positions dependent on speed to ensure the target application rate.

This automatic control process will operate to maintain the application rate substantially constant over a speed range from zero to a maximum application speed. When the speed falls to zero or increases to the maximum application speed, the control arm 14 will actuate a microswitch 1 7 or 1 8 in order to light the warning lamp 7. In operation of the system the knob 6 may be set to any desired position to display the target application rate, the target speed, the instantaneous speed or the instantaneous application rate.

Although the control system has been described above as being provided for agricultural purposes, it will be appreciated that the system could really equally as well be used for other purposes in which a substance is supplied from a moving vehicle. For example the system could be utilized in a gritter lorry.

Claims (11)

1. An agricultural control system for regulating the supply of a substance from a moving vehicle, the system comrising a variable rate supply gate, an electrical actuator for varying the opening of the gate in dependence on an electrical control signal, and control circuitry for supplying the electrical control signal and for regulating that signal in dependence on the speed of the vehicle to cause the opening of the gate to vary with speed such that the rate of application of the substance is maintained substantially constant as the speed of the vehicle varies over a particular speed range.

2. A control system according to claim 1, wherein the speed range over which the rate of application is maintained substantially constant by the control circuitry extends from zero to a maximum application speed.

3. A control system according to claim 1 or 2, wherein the supply gate has a plurality of apertures each of which is provided with a respective shutter for closing off that aperture.

4. A control system according to claim 1, 2 or 3, wherein the actuator comprises an electric motor and a ram arranged to be linearly displaced by the motor in response to receipt of an electrical control signal by the motor.

5. A control system according to any preceding claim, wherein a position sensor is provided for feeding back to the control circuitry a signal indicative of the instantaneous position of the actuator.

6. A control system according to claim 5, wherein the control circuitry is adapted to determined whether the instantaneous position of the actuator corresponds to the instantaneous speed of the vehicle for a target application rate, and to apply a correction signal where adjustment of the position of the actuator is necessitated by a decrease or an increase in the speed of the vehicle.

7. A control system according to any preceding claim, wherein the control circuitry includes adjustable means for setting a target application rate.

8. A control system according to any pre- ceding claim, wherein the control circuity includes a display for indicating the vehicle speed and/or target application rate.

9. A control system according to any preceding claim, wherein warning means are provided for indicating when the speed of the vehicle is no longer within said particular speed range.

10. A control system according to claim 9, wherein to the warning means includes at least one switch arranged to be operated by the actuator.

11. A control system according to claim 9 or 10, wherein the warning means includes a warning lamp.

1 2. An agricultural control system for regulating the supply of a substance from a moving vehicle, substantially as hereinbefore described with reference to the accompanying drawing.

1 3. A vehicle incorporating a control system according to any preceding claim.