Sprayer control system

• US 4,392,611 A
• Filed: 05/15/1981
• Issued: 07/12/1983
• Est. Priority Date: 05/15/1981
• Status: Expired due to Term

• Current Assignee: Dickey-John Corporation (Churchill Industries, Inc.)
• Original Assignee: Dickey-John Corporation (Churchill Industries, Inc.)
• Inventors: Funk, Robert C., Bachman, Wesley J.
• Primary Examiner(s): Kashnikow, Andres
• Application Number:
  US06/264,147
• Time in Patent Office: 788 Days
• Field of Search: 239/71, 239/72, 239/74, 239/155, 239/156, 222/613, 222/614, 222/617, 222/623-627, 222/55, 222/63
• US Class Current: 239/74
• CPC Class Codes: A01M 7/0089 Regulating or controlling systems the delivery being related to the movement of a vehicle B05B9/06
• CPC Class Codes: B05B 9/06 the delivery being related to the movement of a vehicle, e.g. the pump being driven by a vehicle wheel
• CPC Class Codes: G05D 7/0623 characterised by the set value given to the control element

Abstract

An automatic control system for a vehicular liquid sprayer includes a control circuit for receiving a liquid pressure signal and a vehicle ground speed signal and operator accessible controls for delivering to the control circuit signals corresponding to a desired application rate, to the number of nozzles associated with the vehicular liquid sprayer and to the nozzle spacing. The operator may vary the input signal corresponding to desired application rate plus or minus a given percentage to compensate for tolerances in the liquid sprayer system. The control circuit calculates the liquid pressure necessary to achieve the desire application rate and the difference between this desire liquid pressure and the measured liquid pressure and produces control signals corresponding to this difference. A duty cycle control circuit converts these control signals to a cyclical control signal for driving a motor-driven flow control valve. The duty cycle of this cyclical control signal varies in proportion to the magnitude of the pressure difference. This duty cycle controlled signal is automatically modified to overcome inertia and motor lag time in a motor driven flow control valve, and to shut off the valve at a given minimum operating pressure.

Claims

1. An automatic control system for a vehicular liquid sprayer which pumps liquid at a desired pressure to a plurality of nozzles which dispense liquid at a desired volume per unit area application rate, said application rate being a function of predetermined properties of said vehicular liquid sprayer and of the liquid, said control system comprising:

pressure sensing means for sensing the instantaneous pressure of the liquid supplied to said nozzles and for producing a corresponding pressure electrical signal, means for measuring the ground speed of said vehicular liquid sprayer and for producing a corresponding ground speed electrical signal, control circuit means for receiving said pressure signal and said ground speed signal, operator accessible control means for delivering to said control circuit means input electrical signals corresponding to a desired application rate, to the number of nozzles associated with said vehicular liquid sprayer and to the nozzle spacing, said control circuit means being responsive to said pressure signal, said ground speed signal and said input signals for calculating a desired pressure of the liquid supplied to said nozzles necessary to achieve said desired application rate and for calculating the difference between said desired pressure and said instantaneous pressure and producing a first output control signal of a magnitude corresponding to the difference between said desired pressure and said instantaneous pressure and a second output control signal corresponding to the sign of said difference, duty cycle control means for converting said first output control signal to a cyclical control signal of a fixed period whose duty cycle varies in proportion to the magnitude of said first output control signal and pressure control means responsive to said cyclical control signal and to said second output control signal for varying said instantaneous pressure in the amount and direction necessary to equal said desired pressure to thereby achieve and thereafter maintain said desired application rate.

2. A control system according to claim 1 wherein said control circuit means further includes means responsive to said calculated desired pressure being below a predetermined minimum value for producing predetermined first and second output control signals, said duty cycle control means and said pressure control means being responsive to said predetermined first and second output control signals for establishing substantially zero instantaneous pressure of said liquid supplied to said nozzles.

3. A control system according to claim 2 wherein said control circuit means further includes means responsive to said instantaneous pressure being at or below a predetermined minimum value and said calculated desired pressure being at or above said predetermined minimum value for driving said first output control signal to a predetermined maximum magnitude irrespective of the difference between said desired pressure and said instantaneous pressure, until said instantaneous pressure exceeds said predetermined minimum value.

4. A control system according to claim 1 wherein said predetermined variable properties comprise the nominal flow characteristics of said nozzles and the nominal relative density of said liquid and wherein said operator accessible control means further includes means for delivering to said control circuit means control input signals corresponding to said nominal flow characteristics and to said nominal relative density, said control circuit means including means for taking into account said nominal flow characteristics and said nominal density in calculating said desired pressure.

5. A control system according to claim 4 wherein said operator accessible control means includes means for varying the control input signal corresponding to said desired application rate by an amount less than or equal to a predetermined percentage in either direction so as to achieve and maintain said desired application rate substantially without regard for variations in the flow characteristics of said nozzles or in the relative density of said liquid from their respective nominal values.

6. A control system according to claim 1 or claim 5 and further including display means, said control circuit means including means for calculating the instantaneous application rate in accordance with said instantaneous pressure signal and said ground speed signal and for energizing said display means to display said instantaneous application rate.

7. A control system according to claim 6 wherein said operator accessible control means includes manual override means for disabling the production of said first and second control output signals by said control circuit means and for actuating said pressure control means directly to achieve and maintain said desired application rate by observing said display of said instantaneous application rate.

8. A control system according to claim 1 or claim 5, said control circuit means further including means for producing a test ground speed signal corresponding to a known predetermined ground speed when said vehicular liquid sprayer is stationary so as to achieve and maintain a known predetermined application rate, whereby the liquid discharged from said nozzles may be collected and measured, thereby providing an indication of a desired amount of variation in said control input signal corresponding to said desired application rate for achieving and maintaining said desired application rate.

9. A control system according to claim 8 and further including display means, said control circuit means including means for energizing said display means to display said instantaneous pressure whereby said displayed pressure may be compared with a known desired pressure to be achieved and maintained in response to said test ground speed signal and said desired application rate signal to verify the proper functioning of said control system.

10. A control system according to claim 1 or claim 5 wherein said duty cycle control means includes means for producing a ramp signal of predetermined peak-to-peak value and at a predetermined constant frequency, means responsive to said first output control signal for producing an error signal of analog value corresponding to the magnitudes of said first output control signal and comparator means for receiving and comparing the values of said error signal and said ramp signal and thereby producing said cyclical control signal.

11. An automatic control system for a vehicular liquid sprayer which pumps liquid at a desired pressure to a plurality of nozzles which dispense liquid at a desired volume per unit area application rate, said application rate being a function of said desired pressure, of the ground speed of said vehicular liquid sprayer and of predetermined properties of said vehicular liquid sprayer and of the liquid, said vehicular liquid sprayer including pressure sensing means for sensing the instantaneous pressure of the liquid supplied to said nozzles and for producing a corresponding pressure electrical signal and ground speed sensing means for measuring the ground speed of said vehicular liquid sprayer and for producing a corresponding ground speed electrical signal, said control system comprising:

control circuit means for receiving said pressure signal and said ground speed signal, operator accessible control means for delivering to said control circuit means input electrical signals corresponding to a desired application rate and to said predetermined properties of said vehicular liquid sprayer and of the liquid, said control circuit means including calculating means responsive to said pressure signal, said ground speed signal and said input signals for calculating said desired pressure, and for producing an error signal corresponding to the difference between said desired pressure and said instantaneous pressure and an output control signal corresponding to the sign of said difference, pressure control means responsive to said error signal and said output control signal for varying said instantaneous pressure in the amount and direction necessary to achieve and maintain said desired pressure, said control circuit means further including means responsive to said calculated desired pressure being below a predetermined minimum value for producing a predetermined error signal and a predetermined output control signal, said pressure control means being responsive to said predetermined error signal and said predetermined output control signal for establishing substantially zero instantaneous pressure to said nozzles, and said control circuit means further including means responsive to said instantaneous pressure being at or below a predetermined minimum value and said calculated desired pressure being at or above said predetermined minimum value for producing a predetermined maximum error signal and a predetermined output control signal until said instantaneous pressure exceeds said predetermined minimum value.

12. A control system according to claim 11 wherein said predetermined variable properties comprise the nominal flow characteristics of said nozzles and the nominal relative density of said liquid and wherein said operator accessible control means further includes means for delivering to said control circuit means control input signals corresponding to said nominal flow characteristics and to said nominal relative density, said control circuit means including means for taking into account said nominal flow characteristics and said nominal density in calculating said desired pressure.

13. A control system according to claim 12 wherein said operator accessible control means includes means for varying the control input signal corresponding to said desired application rate by an amount less than or equal to a predetermined percentage in either direction so as to achieve and maintain said desired application rate substantially without regard for variations in the flow characteristics of said nozzles or in the relative density of said liquid from their respective nominal values.

15. A control system according to claim 11 or claim 14 and further including duty cycle control means interposed between said control circuit means and said pressure control means for producing a cyclical control signal of a fixed period and of variable duty cycle, said variable duty cycle varying in proportion to the magnitude of said error signal when said instantaneous pressure is above said predetermined minimum value and said desired pressure is above said predetermined minimum value.

16. A control system according to claim 15 wherein said duty cycle control means includes means for producing a ramp signal of predetermined peak-to-peak value and at a predetermined constant frequency, means responsive to said first output control signal for producing an error signal of analog value corresponding to the magnitude of said first output control signal and comparator means for receiving and comparing the values of said error signal and said ramp signal and thereby producing said cyclical control signal.

14. An automatic control system for a vehicular liquid sprayer which pumps liquid at a desired pressure to a plurality of nozzles which dispense liquid at a desired volume per unit area application rate, said application rate being a function of said desired pressure, of the ground speed of said vehicular liquid sprayer and of predetermined variable properties of said vehicular liquid sprayer and of the liquid, said vehicular liquid sprayer including pressure sensing means for sensing the instantaneous pressure of the liquid supplied to said nozzles and for producing a corresponding pressure electrical signal and ground speed sensing means for measuring the ground speed of said vehicular liquid sprayer and for producing a corresponding ground speed electrical signal, said control system comprising:

control circuit means for receiving said pressure signal and said ground speed signal, operator accessible control means for delivering to said control circuit means input electrical control signals corresponding to nominal values of said predetermined variable properties of said vehicular liquid sprayer and of the liquid and corresponding to a desired application rate, said control circuit means being responsive to said pressure signal, said ground speed signal and said control signals for calculating a desired pressure of the liquid supplied to said nozzles necessary to achieve said desired application rate and for calculating the difference between said desired pressure and said instantaneous pressure and producing control output signals corresponding to said difference and to the sign of said difference and pressure control means responsive to said control output signals for varying said instantaneous pressure in the amount and direction necessary to achieve said desired pressure to thereby achieve and maintain said desired application rate, and wherein said operator accessible control means further includes means for varying the control signal corresponding to said desired application rate by an amount less than or equal to a predetermined percentage so as to achieve and maintain said application rate substantially without regard for variations in said variable properties from the nominal values established by said operator accessible control means.

17. A control system according to claim 14 wherein said predetermined variable properties comprise the nominal flow characteristics of said nozzles and the nominal relative density of said liquid and wherein said operator accessible control means further includes means for delivering to said control circuit means control input signals corresponding to said nominal flow characteristics and to said nominal relative density, said control circuit means including means for taking into account said nominal flow characteristics and said nominal density in calculating said desired pressure.

18. An improvement in a control system for a mobile material distribution apparatus wherein the rate of material distribution per unit area varies as a predetermined function of the ground speed of the mobile apparatus and including ground speed sensor means for developing a ground speed signal corresponding to the ground speed of the mobile apparatus, distributing means for distributing said material along a given path of travel of the apparatus, variable rate delivery means for delivering material at a controllable rate to said distributing means, delivery rate sensor means for developing an actual delivery rate signal corresponding to actual rate of delivery of material and desired distribution rate control means for developing a desired distribution rate signal corresponding to a desired distribution rate of material per unit area, the improvement comprising:

control circuit means responsive to said ground speed signal, to said actual delivery rate signal and to said desired distribution rate signal for calculating a desired delivery rate of material to the distributing means necessary to achieve said desired distribution rate and for calculating the difference between said desired delivery rate and said actual delivery rate and for developing a corresponding difference signal and duty cycle control means responsive to said difference signal for developing a cyclical control signal whose duty cycle varies in a predetermined fashion in accordance with said difference signal, said delivery means being responsive to said cyclical control signal for varying the delivery rate of material to said distributing means in the amount necessary to achieve said desired material delivery rate so as to achieve and thereafter maintain said desired distribution rate.

19. The improvement according to claim 18 wherein said control circuit means further includes maximum output signal means responsive to said difference signal being at or above a predetermined value for developing a maximum value output signal in place of said cyclical control signal, said delivery means being responsive to said maximum output signal for varying the delivery rate of material at a maximum rate of change until said difference signal falls below said predetermined value.

20. The improvement according to claim 18 wherein said desired rate control means further includes means for developing a percentage variation signal for varying the desired distribution rate signal by an amount less than or equal to a predetermined percentage thereof in either direction so as to achieve and maintain said desired distribution rate substantially without regard for variations in the nominal operating characteristics of said material distribution apparatus.

21. The improvement according to claim 18 and further including operator accessible manual control means for controlling said delivery means directly to achieve and maintain said desired distribution rate.