Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Title: CONTROLLED APPLICATION OF WEED CONTROL CHEMICALS
FROM MO~1NG SPRAYER
Field of the Invention
This invention relates means for applying
herbicides to control of weeds. More specifically, it
relates to an apparatus for selectively directing weed-
killing chemicals to weeds under open-field conditions.
Background to the Invention
Environmental and economic concerns are forcing
agricultural producers to modify traditional practices to
remain viable. Soil conservation, moisture conservation,
and herbicide costs are the primary concerns facing the
North American agricultural producer.
In most dry land farming the crops are moisture
limited so that a field must be rotated, using a fallow
year. The traditional practice in fallow is to use
tillage to control the weeds. However in dry land
conditions the use of tillage promotes moisture loss and
soil erosion. Leaving the field to stubble reduces the
moisture loss and soil erosion. The stubble is useful in
trapping snow during the winter, reduces the evaporation
during the summer, and fixes the soil to reduce erosion.
Chemical fallow procedures use herbicides to
control the weeds in stubble. Traditionally chemical
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weed control procedures for land in fallow require the
applicator to spray the entire field. Broadcast spraying
of herbicide for weed control is more expensive, in the
short term, than tillage.
Techniques have been developed to detect weeds
in fallow or stubble fields so that the weeds can be
selectively sprayed without spraying the entire field.
Current general usage does not, however, adequately
control the release of the herbicide spray. This is
particularly true where the spraying boom must be swept
in an arc. The present invention allows the applicator
to more selectively spray weeds in stubble or fallow,
thus reducing the cost of chemically controlled fallow.
A prior art selective sprayer product sold
under the trademark Detect-Spray by an Australian company
is described in U.S. Patent No. 5,144,767.
Two further patents that specifically
contemplate synchronizing the release of herbicide with
the speed of all the spray nozzles carried by the vehicle
boom are U.S. Patents 5,222,324 and 5,278,423.
The present invention has as its objective the
provision of an improved means for directing herbicidal
spray at selected weeds and particularly weeds in
portions of fallow or stubble fields where the farm
implement providing weed-control chemicals must sweep
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out a radius while the chemicals are being applied to
such weeds.
The invention in its general form will first be
described, and then its implementation in terms of
specific embodiments will be detailed with reference to
the drawings following hereafter. These embodiments are
intended to demonstrate the principle of the invention,
and the manner of its implementation. The invention in
its broadest and more specific forms will then be further
described, and defined, in each of the individual claims
which conclude this Specification.
Summary of the Invention
The invention in its broadest aspect provides
a means by which identified weeds are selectively sprayed
with herbicide through use of multiple spray nozzles.
The timing of the release of herbicide spray from each
individual nozzle is co-ordinated with the speed with
which each nozzle is passing over the ground. The
individual speed at which each nozzle is passing over the
ground is determined by measuring the ground speed at two
points from within the structures carrying the nozzles,
and extrapolating the ground speed of each nozzle in
accordance with its location within the structure.
The controller provides a delay means that
allows for the passage of time between the identification
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of a weed by a weed sensor, and the release of herbicidal
spray by each individual weed spray nozzle as it passes
over the ground, ensuring that herbicide is primarily
released in order to arrive at the location where weeds
have been detected.
In a preferred embodiment, Ground Speed sensors
are installed at two or more locations along with the
booms carrying the spray nozzles, causing them to
traverse the field. In particular, controlled release is
co-ordinated with the ground during the turning of the
booms while the farm implement changes its direction of
travel in the field.
The foregoing summarizes the principal features
of the invention and some of its optional aspects. The
invention may be further understood by the description of
the preferred embodiments, in conjunction with the
drawings, which now follow.
Summary of the Figures
Figure 1 is a functional block diagram of the
weed detection and spray control functions of the
invention;
Figure 2 is a functional block diagram of the
weed sensor system;
Figure 3 is a schematic block diagram of the
components of a multi-unit spray control system; and
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Figure 4 is a plan view of a tractor pulling a
boom with spray nozzles, viewing sensors and speed
sensors.
Figure 5 is a profile schematic view of a
viewing sensor and nozzle on the boom.
Figure 6 is a perspective schematic depiction
of the elements of Figure 6 plus a ground speed sensor
mounted on the boom.
Figure 7 is a depiction of the tractor of
Figure 4 as it sweeps its nozzle carrying booms in an
arc.
Description of the Preferred Embodiment
The invention in respect of the identification
of objects will be exemplified by reference to a weed
control system. For convenience, the invention and its
variants will hereafter be referred to as the Spray
Vision System. The described weed detection system is
only one example of a weed detection methodology and
other means for detecting weeds may be employed.
The functional block diagram of the Spray
Vision System shown in Figure 1 provides a Weed Sensor
which measures through chromatic filters the reflected
chromagraphic light (Reflected Light) and, by comparison
with the ambient chromagraphic light (Ambient Light) to
produce a reflectance value, provides the Weed Signal.
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This is done by generating a chromatic vector based on
four bands of the electromagnetic spectrum. Although
four bands are preferred, at least three may be used.
The Ambient Light is the amount of ambient light coming
from the sky. The Reflected Light is the light reflected
from the target area. The Weed Signal is, in the
preferred mode, a four dimensional vector which is used
to provide an estimation of the amount of weeds in the
field-of-view.
The Weed Detector compares the Weed Signal in
a colour space transform to the Weed Threshold, with an
internally provided comparative standard, and determines
if there is a basis to issue the Weed Present signal and
effect the automatic spraying of the weeds. The Weed
Threshold is an operator-adjustable level. The Weed
Present signal is issued if the Weed Signal exceeds the
Weed Threshold; otherwise the Weed Present signal is
cleared.
The Estimate Sensor Speed function in Figure 1
provides a signal based on the speed of at least two
Sensors, or their equivalent, as they travel over the
ground. These speed values can be provided from one of
three different sources: by operator input, by a speed
sensor mounted on the tractor, or by measuring the speed
of the boom or nozzle support structure as it passes over
the ground.
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The Operator Input Speed parameter is
preferably the default speed that can be entered by the
operator from the cab of the tractor. The Tractor Speed
parameter is determined by interfacing the System to the
speedometer, or a groundspeed sensor, on the tractor.
The Boom Speed parameter uses one or more groundspeed
sensors located along the boom(s), preferably at or near
the tips of the boom. Using this input data and knowing
the location of each nozzle along the boom(s) the Spray
Vision Controller then calculates the ground speed of
each nozzle relative to it's position on the boom and
controls release of herbicide.
The Speed Mode input is an operator input to
allow the operator to select which method of estimating
speed to use.
The Spray Vision Controller is a microprocessor
which uses the various inputs to control the operation of
each nozzle solenoid (via SolenoidCntl) that releases
chemical herbicide. The Controller also sends status and
alarm information to the operator.
The Solenoid Control Mode (SolenoidCntlMode)
sets the operation of the Spray Vision Controller to one
of three modes (OFF, ON, and AUTO). In the OFF mode the
Solenoid Control (SolenoidCntl) output is forced to be
off. In the ON mode the Solenoid Control is forced on.
In the AUTO mode the Solenoid Control is determined by
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the Weed Present signal and the Sensor Distance
(SensorDistance) which is the spacing between the Weed
Sensor and the nozzle in the direction of travel.
The Sensor Distance, Sensor Speed, and the
Solenoid Control turn-on delay inputs are used by the
Spray Vision Controller to calculate the delay between
when a Weed Present signal is generated or set, and when
the Solenoid Control should be set to release herbicide
from a nozzle. The objective of this calculation is to
release the chemical herbicide from the nozzle at the
moment when the nozzle passes over a weed. The delay
function, and timing established by the Spray Vision
Controller provides the valuable benefit of minimizing
the consumption of herbicide by restricting its dispersal
to substantially the area where weeds are located.
The Status Display (StatusDspl) output in
Figure 1 indicates if the Spray Vision Sensor is spraying
or not. The Alarm indicates if the Spray Vision Sensor
or system has a problem or fault. The Power Indication
(PwrInd) indicates if there is power applied to the
system.
The Weed Sensor may measure the presence of
weeds by the preferred method described in U.S.
application Serial No. 08/191,578, now U.S. Patent No.
5,507,115, the contents of which are adopted herein by
reference.
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The invention preferably uses distributed
microprocessor-based sensors to detect and selectively
spray the weeds in a field. The system uses a
distributed communications system to allow the individual
units to exchange information for added flexibility and
reliability. The system is designed in a modular fashion
to allow for system flexibility and low cost, mass
manufactured units. A simplified physical block diagram
of the Spray Vision System is given in Figure 3.
The Spray Vision Network allows the units to
communicate with each other, to send operator commands to
the Sensor Units, transmit ambient light levels to the
sensors, transmit the ground speed, display status and
alarms to the Operator Panel, and distribute power to the
units.
As the Spray Vision System uses a distributed
control structure, each Spray Vision Sensor contains a
microprocessor that executes the decision algorithm and
controls the solenoid locally. All of the relevant
information required to execute the decision algorithm is
transmitted to the sensor over the distributed
communications system. The status and fault conditions
of the sensor can be transmitted to other units using the
communications satem also.
The alternative of a centralized controller,
while possible, can reduce the reliability of the system
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because of the number of electrical connections, and
because the centralized controller is typically more
complex than the individual distributed controllers. The
reliability of a centralized controller is typically
lower than the reliability of a distributed control
system because if the centralized controller fails then
the entire system has failed; however if a distributed
controller fails then only a small incremental portion of
the system is inoperative and the rest of the system
operates normally.
The input speed of the unit to be used by each
of the micro processors can be optionally entered at the
Operation Panel, monitored at the tractor, or measured by
the Speed Units located on the booms, the herbicide
carrier or on the tractor. Preferably 2 Speed Sensors
are utilized, one at either end of the boom, as shown in
Figure 4. The use of two ground speed measurements taken
from separated locations within the nozzle support
structure allows the Spray Vision Controller to
compensate for tractor speed and turns. Use of two boom-
mounted Speed Units is optional and the system employing
the invention can operate on the basis of two ground
speed inputs, one of which may be obtained using the
tractor ground speed or an operator input speed which is
attributed to a specific portion of the assembly, e.g.
the tractor.
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A variety of known ground speed measuring
devices may be employed. These may operate on the basis
of sonar, radar, laser light and may include wheel or
speedometer-coupled wheel sensors. One sonar based
system sold under the trade mark TRAK-STAR is referenced
in U.S. Patent No. 4,728,954.
In Figure 4, a preferred arrangement is
depicted in which a tractor 30 pulls a boom 31 carrying
nozzles 32 with solenoids 33. Viewing sensors 34 and
preferably two speed sensors 35 are located at the
outermost ends of the boom 31. A sprayer tank 36
provides herbicide through tubing (not shown) to the
nozzles 32. Power for the solenoids 33 originates from
the power distribution assembly 37. An ambient light
sensor 38 measures ambient light and an operator display
39 provides information to the operator.
In Figure 5, the viewing sensor 34 has a field-
of-view 40, and the nozzle 32 has a field-of-spray 41.
The micro-processor 45 for activation of the solenoid 33
times the opening of the nozzle 32 to allow for the speed
over the ground 42 of the part of the boom 31 carrying
each nozzle 32 in the direction of travel 43, as well as
for the delay taken by the herbicide to pass from the
nozzle 32 to the ground 42.
In Figure 6, a sonar or radar-type speed sensor
35 located along at a boom end views the ground and
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detects (from the motion of the image or by other means)
the speed of the boom end 44 (where the sensor 35 is
located) over the ground 42.
As shown in Figure 7, as the tractor wheels
through a turn the individual processors/controllers 45
at each nozzle 32 receive the ground speed signal of at
least two of the speed sensors 35 via wires 46. Based on
their known locations along the boom 31, the individual
controllers 45a can interpolate the ground speed for
their assigned nozzle 32a. This permits individual
adjustment of the timing of the release of herbicide by
a nozzle to ensure that the field-of-view 40 and field-
of-spray 41 overlap, even when the boom 31 is sweeping-
out an arc.
Conclusion
The foregoing has constituted a description of
specific embodiments showing how the invention may be
applied and put into use. These embodiments are only
exemplary. The invention in its broadest, and more
specific aspects, is further described and defined in the
claims which now follow.
These claims, and the language used therein,
are to be understood in terms of the variants of the
invention which have been described. They are not to be
restricted to such variants, but are to be read as
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covering the full scope of the invention as is implicit
within the invention and the disclosure that has been
provided herein.
