NZ750501B2 - System and method for calibrating an irrigation system - Google Patents
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Abstract
system and method for calibrating an irrigation system to account for variations in flow rates caused by field elevation changes, pipe friction losses, water emitter nozzle wear, pressure-regulator inaccuracies, and other factors. A calibration map is created to account for the flow rate variations and then consulted to control operation of the irrigation system. ns and then consulted to control operation of the irrigation system.
Description
SYSTEM AND METHOD FOR CALIBRATING
AN IRRIGATION SYSTEM
This application claims priority from US Application No. 15/891,977 filed on 8 February 2018, the
contents of which are to be taken as incorporated herein by this reference.
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to agricultural irrigation systems. More particularly, the
invention relates to a system and method for calibrating an irrigation system to account for
variations in water flow rates from the irrigation system.
2. BACKGROUND
Agricultural irrigation systems such as central pivot and lateral move irrigation systems
are commonly used to irrigate crops. A central pivot irrigation system typically includes, among
other things, a central pivot communicating with a pressurized water supply and a main section
that moves about the central pivot to irrigate a circular or semi-circular field. The main section
includes a number of mobile support towers connected to the central pivot and to one another by
truss-type framework sections. The mobile support towers are supported on wheels that are
driven by a motor on each tower. A water distribution conduit is supported by the framework
sections, and a number of sprinkler heads, spray guns, drop nozzles, or other water emitters are
spaced along the length of the conduit for irrigating crops below the irrigation system. Lateral
irrigation systems are similar except they don=t include central pivots and move in a relatively
straight line rather than a circle.
It is desirable to monitor and control the amount of water delivered by an irrigation
system to prevent over or under-watering of crops and to conserve water. Similarly, it is often
desirable to deliver different amounts of water to different portions of a field to accommodate
different soil conditions, types of crops, and the existence of roads, boundaries, etc. in the field.
Thus, it is common to divide a field into sections and to create an irrigation plan that calls for
prescribed amounts of water to be delivered to each section. A control system then controls the
speed of the mobile towers and/or the opening and closing of water valves to deliver the
prescribed amounts of water to each section.
Unfortunately, even when following irrigation plans, irrigation systems often fail to
accurately deliver prescribed amounts of water because field elevation changes, water pipe
friction losses, water emitter nozzle wear, pressure-regulator inaccuracy, and other factors can
cause variations in water flow rate, especially over time. Irrigation plans are typically created for
expected flow rates from an irrigation system when its on flat, level ground and therefore may
call for too little water as the irrigation system travels up a hill (and water pressures drop) and too
much water as the irrigation system operates in a valley (and water pressures increase).
Moreover, irrigation plans are typically created when an irrigation system is first placed into
service and become less accurate over time as pipes, valves, pressure regulators, water emitters
and other components age.
SUMMARY
The present invention solves the above described problems by providing a system and
method for calibrating an irrigation system to compensate for variations in flow rates caused by
field elevation changes, pipe friction losses, water emitter nozzle wear, pressure-regulator
inaccuracies, and other factors. In general, the invention first creates a calibration map to assess
and record the above-described flow rate variations and then controls operation of the irrigation
system in accordance with the calibration map to more accurately compensate for the flow rate
variations.
To create a calibration map, actual flow rates through the irrigation system, or portions of
the irrigation system, are periodically or continuously measured and recorded as the irrigation
system moves across a field. These measured flow rates are then compared to expected flow
rates through the irrigation system, or portions of the irrigation system, based on the original
design or configuration of the irrigation system. Correction factors that account for the
differences between the measured flow rates and the expected flow rates are then created for
different portions or sections of the field. For example, if the measured flow rate in a first
section is 5% less than expected, a correction factor of +5% is assigned to that section to indicate
% more water is required. Similarly, if the measured flow rate in a second section is 10% more
than expected, a correction factor of -10% is assigned to that section to indicate 10% less water is
required. The correction factors and positional information for the corresponding field sections
are then stored in the calibration map.
The calibration map may be created while the irrigation system is operating in a
calibration mode or Aon-the-fly@ while the irrigation system is irrigating a field. The calibration
map may be created when the irrigation system is first placed into service and may be
periodically or continuously updated to account for changing conditions such as degradation of
the valves, water emitters, pressure regulator and/or other components of the irrigation system.
Once the calibration map is created, a control system consults the calibration map to
adjust at least one operational aspect of the irrigation system in accordance with the correction
factors. For example, if an irrigation plan or an initial setting of the irrigation system calls for 10
gallons per minute (G.P.M.) of water in a section of the field, but the calibration map indicates a
+10% correction factor for that section, the control system adjusts an operational aspect of the
irrigation system so as to apply 10% more water than it would have without the calibration map.
The operational aspect that is adjusted may be the speed of the irrigation system=s mobile
towers, a duty cycle of the irrigation system=s water emitters, a water flow rate of individual
water emitters or banks of water emitters, or anything else that controls the rate of fluid flow of
the irrigation system to adjust water flow rates in accordance with the correction factors. For
example, the control system may operate the mobile towers 10% slower than called for by an
irrigation plan so as to apply 10% more water.
One particular embodiment of the invention is a method of calibrating an irrigation
system having a plurality of mobile towers and a plurality of water emitters supported by the
mobile towers. The method comprises: operating the mobile towers to move the irrigation
system over a ground surface; toggling the water emitters as the irrigation system moves over the
ground surface; determining positions of the irrigation system as the irrigation system moves
over the ground surface and as the water emitters are toggled; measuring flow rates through the
irrigation system as the irrigation system moves over the ground surface and as the water emitters
are toggled; comparing the measured flow rates to expected flow rates; creating a calibration map
that reflects differences between the measured flow rates and the expected flow rates at the
determined positions; and calibrating operation of the irrigation system with the calibration map
by adjusting an operational aspect of the irrigation system to account for the differences between
the measured flow rates and the expected flow rates at the determined positions.
Another embodiment of the invention is an irrigation system comprising: a central pivot;
a series of mobile towers each having wheels and a motor for driving the wheels; support
structure for connecting the mobile towers to each other and to the central pivot; a water-carrying
conduit supported by the support structure; a plurality of water emitters connected to the conduit
for delivering water to a ground surface; a valve for controlling water flow to the water emitters;
and a control system for controlling operation of the mobile tower motors and the valve so as to
control the amount of water delivered to sections of a field. The control system is programmed
to: operate the mobile towers to move the irrigation system over the field; toggle the valve as the
irrigation system moves over the ground surface; determine positions of the irrigation system as
the irrigation system moves over the ground surface and as the valve is toggled; measure fluid
flow rates through the irrigation system as the irrigation system moves over the ground surface
and as the valve is toggled; compare the measured flow rates to expected flow rates for the
determined positions of the irrigation system; create a calibration map that reflects differences
between the measured flow rates and the expected flow rates at the determined positions; and
calibrate operation of the irrigation system with the calibration map by adjusting an operational
aspect of the irrigation system to account for the differences between the measured flow rates and
the expected flow rates at the determined positions.
This summary is provided to introduce a selection of concepts in a simplified form that
are further described in the detailed description below. This summary is not intended to identify
key features or essential features of the claimed subject matter, nor is it intended to be used to
limit the scope of the claimed subject matter. Other aspects and advantages of the present
invention will be apparent from the following detailed description of the embodiments and the
accompanying drawing figures. For example, the principles of the present invention are not
limited to central pivot irrigation systems, but may be implemented in other types of irrigation
systems including linear move irrigation systems.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
Embodiments of the present invention are described in detail below with reference to the
attached drawing figures, wherein:
Fig. 1 is a perspective view of an exemplary central pivot irrigation system that may be
used to implement aspects of the present invention.
Fig. 2 is a block diagram that depicts selected components of a control system of the
irrigation system.
Fig. 3 is a schematic plan view of a field that has been subdivided into a number of
wedge-shaped sections and showing the irrigation system operating in the field.
Fig. 4 is a schematic plan view of a field that has been subdivided into a number of
wedge-shaped sections with each section further divided into a number of annulus sectors and
showing the irrigation system operating in the field.
Fig. 5 is a graphical representation of a calibration map that may be used to calibrate
operation of the irrigation system.
Fig. 6 is a graphical representation of another calibration map that may be used to
calibrate operation of the irrigation system.
Fig. 7 is a flow diagram depicting exemplary steps in a method of the present invention or
portions of a computer program of an embodiment of the present invention.
The drawing figures do not limit the present invention to the specific embodiments
disclosed and described herein. The drawings are not necessarily to scale, emphasis instead
being placed upon clearly illustrating the principles of the invention.
DETAILED DESCRIPTION
The following detailed description of embodiments of the invention references the
accompanying drawings. The embodiments are intended to describe aspects of the invention in
sufficient detail to enable those skilled in the art to practice the invention. Other embodiments
can be utilized and changes can be made without departing from the scope of the claims. The
following detailed description is, therefore, not to be taken in a limiting sense. The scope of the
present invention is defined only by the appended claims, along with the full scope of equivalents
to which such claims are entitled.
In this description, references to Aone embodiment@, Aan embodiment@, or
Aembodiments@ mean that the feature or features being referred to are included in at least one
embodiment of the technology. Separate references to Aone embodiment@, Aan embodiment@, or
Aembodiments@ in this description do not necessarily refer to the same embodiment and are also
not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled
in the art from the description. For example, a feature, structure, act, etc. described in one
embodiment may also be included in other embodiments, but is not necessarily included. Thus,
the present technology can include a variety of combinations and/or integrations of the
embodiments described herein.
Turning now to the drawing figures, and initially Fig. 1, an exemplary irrigation system
on which principles of the present invention may be implemented is illustrated. The
illustrated irrigation system 10 is a central pivot irrigation system, but it may also be a linear
move or lateral type irrigation system or any other type of automated irrigation system. The
illustrated irrigation system 10 broadly comprises a fixed central pivot 12, a main section 14
pivotally connected to the central pivot, and a control system 100 (Fig. 2) for controlling
operation of the irrigation system and for implementing the calibration features of the present
invention.
The fixed central pivot 12 may be a tower or any other support structure about which the
main section 14 pivots. The central pivot has access to a well, water tank, or other source of
water and may also be coupled with a tank or other source of agricultural products to inject
fertilizers, pesticides and/or other chemicals into the water for application during irrigation.
The main section 14 pivots or rotates about the central pivot 12 and includes a number of
mobile support towers 16A-D, the outermost 16D of which is referred to herein as an end tower.
The mobile towers are connected to the fixed central pivot 12 and to one another by truss
sections 18A-D or other supports to form a number of interconnected spans. The illustrated
irrigation system 10 has four mobile support towers, and thus four spans, however, it may
comprise any number of towers and spans without departing from the scope of the invention
The mobile towers have wheels 20A-D driven by drive motors 22A-D. Each motor 22A-
D turns at least one of the wheels 22A-D through a drive shaft to move its mobile tower and thus
the main section 14 in a circle or semi-circle about the central pivot 12. The motors 22A-D may
include integral or external relays so they may be turned on, off, and reversed by the control
system 100 as described below. The motors may also have several speeds or be equipped with
variable speed drives.
Although not required, some or all of the towers 16A-D may be equipped with steerable
wheels pivoted about upright axes by suitable steering motors so that the towers can follow a
predetermined track. U.S. Patent 4,508,269 in the name of Davis et al. is hereby incorporated by
reference in its entirety into the present specification for a disclosure of ground drive motors and
steering motors associated with an irrigation machine. As is also well known, the drive motors
for the towers are controlled by a suitable safety system such that they may be slowed or
completely shut down in the event of the detection of an adverse circumstance.
Each of the truss sections 18A-D carries or otherwise supports a conduit section 24A-D
or other fluid distribution mechanism that is connected in fluid communication with all other
conduit sections and to a source of fluids from the central pivot. A plurality of sprinkler heads,
spray guns, drop nozzles, or other water emitters 26A-P are spaced along the conduit sections
24A-D to apply water and/or other fluids to land underneath the irrigation system.
At least one valve is disposed between the conduit sections 24A-D and the water emitters
26A-P to control the flow of water through the water emitters. In some embodiments, the
irrigation system includes several valves, and each valve controls the flow of water through a
single water emitter such that each water emitter can be individually opened, closed, pulsed, etc.
to emit any amount of water. In an embodiment illustrated in Fig. 2, the irrigation system 10
includes several valves 28A-D that each control the flow of water through a group of water
emitters such that the group of water emitters is controlled to emit a specific amount of water.
For example, each span of the irrigation system may include four water emitters, and one valve
may control the water flow through all four water emitters such that all of the water emitters on a
span operate in unison. The valves may be magnetic latching solenoid valves that are normally
biased to an off/closed state such that the valves only switch to an on/open state when powered,
but they may be any type of valve.
In accordance with one aspect of the invention, the irrigation system 10 also includes at
least one flow meter 30 (Fig. 2) that measures water flow rates through the system. Outputs from
the flow meter are provided to the control system 100 to calibrate the irrigation system as
described in more detail below. In one embodiment, a single flow meter measures flow rates
through the entire irrigation system and provides an indication of this aggregate flow rate to the
control system. In other embodiments, multiple flow meters provide flow-rate measurements
through different portions of the irrigation system, such as through each span of the irrigation
system or even each water emitter. However, because equipping an irrigation system with
multiple flow meters is costly and complicated, embodiments of the present invention permit
calibration of the irrigation system with a single flow meter as discussed below.
Embodiments of the irrigation system may also include a pressure regulator for regulating
the pressure of water through to the irrigation system. Pumps that provide water to the irrigation
system may be configured to provide a minimum water pressure, and the pressure regulator then
reduces the pump water pressure to a selected maximum pressure level such that the pumps and
pressure regulator together provide a relatively constant water pressure through the irrigation
system. However, as described above and below, the water pressure of the irrigation system
may still fluctuate as the irrigation system moves about a field and/or over time as the pressure
regulator ages.
The irrigation system 10 may also comprise other components such as an extension arm
(also commonly referred to as a Aswing arm@ or Acorner arm@) pivotally connected to the free
end of the main section and/or one or more high pressure sprayers or end guns 32 mounted to the
end tower 16D or to the end of the extension arm. The end guns are activated at the corners of a
field or other designated areas to increase the amount of land that can be irrigated.
The control system 100 and its operation will now be described in more detail. The
control system 100 controls operation of the irrigation system and implements some of the
calibration steps as described in more detail below. The control system and can be implemented
with hardware, software, firmware, or a combination thereof. One embodiment of the control
system 100 is illustrated in Fig. 2 and comprises a controller or other computing device 102,
memory 104, and a location-determining component 106. The control system 100 may also
include conventional input devices such as knobs, buttons, switches, dials, etc.; inputs for
receiving programs and data from external devices; one or more displays; a cellular or other radio
transceiver for wirelessly receiving and transmitting data from and to remote devices; a bluetooth
transceiver; a wifi transceiver; and/or other electronic components.
The computing device 102 may comprise or include any number or combination of
processors, controllers, ASICs, computers or other control circuitry. As illustrated, the
computing device includes data inputs for receiving data from the flow-meter 30 and the
location-determining component 106 and outputs connected to the relay-controlled valves 28A-B
and the relay-controlled drive motors 22A-D. The illustrated control system 100 is shown
controlling four drive motors 22A-D and four valves 28A-D, but it may control any number of
motors and valves and other components of the irrigation system.
Some of the control functions described herein may be implemented with one or more
computer programs executed by the computing device 100. Each computer program comprises
an ordered listing of executable instructions for implementing logical functions in the computing
device 102 and can be embodied in any computer-readable medium for use by or in connection
with an instruction execution system, apparatus, or device, such as a computer-based system,
processor-containing system, or other system that can fetch the instructions from the instruction
execution system, apparatus, or device, and execute the instructions. In the context of this
application, a Acomputer-readable medium@ can be any means that can contain, store,
communicate, propagate or transport the program for use by or in connection with the instruction
execution system, apparatus, or device including, but not limited to, the memory 104. The
computer-readable medium can be, for example, but not limited to, an electronic, magnetic,
optical, electro-magnetic, infrared, or semi-conductor system, apparatus, device, or propagation
medium. More specific, although not inclusive, examples of the computer-readable medium
would include the following: an electrical connection having one or more wires, a random
access memory (RAM), a read-only memory (ROM), an erasable, programmable, read-only
memory (EPROM or Flash memory), an optical fiber, and a portable compact disk read-only
memory (CDROM).
The memory 104 may be any electronic memory that can be accessed by the computing
device 102 and operable for storing instructions or data. The memory 104 may be integral with
the computing device 102 or may be external memory accessible by the computing device. The
memory may be a single component or may be a combination of components that provide the
requisite functionality. The memory may include various types of volatile or non-volatile
memory such as flash memory, optical discs, magnetic storage devices, SRAM, DRAM, or other
memory devices capable of storing data and instructions. The memory may communicate
directly with the computing device or may communicate over a bus or other mechanism that
facilitates direct or indirect communication. The memory may optionally be structured with a
file system to provide organized access to data existing thereon.
The location-determining component 106 may be any device capable of determining
positions of the irrigation system. The location-determining component may comprise, for
example, an angle encoder positioned at the central pivot and the joint of each span of the
irrigation system for sensing an angle between the central pivot 12 and the main section 14 and
between each span of the irrigation system. In some embodiments, the angle encoders may be
incorporated in existing articulating joints positioned between the spans so that the control
system does not require its own dedicated angle encoders. The location-determining component
106 may also comprise one or more modified cam switches, proximity switches, optical
encoders, potentiometers, light bar sensors, etc. at each span joint.
The location-determining component 106 may also be a global navigation satellite system
(GNSS) receiver such as a GPS receiver, Glonass receiver, Galileo receiver, or compass system
receiver attached to or near one or more of the mobile towers and operable to receive
navigational signals from satellites to calculate positions of the mobile towers as a function of
the signals. Each GNSS receiver may include one or more processors, controllers, or other
computing devices and memory for storing information accessed and/or generated by the
processors or other computing devices. In some embodiments, a single GNSS receiver receives
satellite signals from separate antennas mounted to each mobile tower so that a receiver is not
required at each tower. The GNSS receiver or receivers may be incorporated in the main control
system so that the control system does not require its own dedicated GNSS receivers or may be
stand-alone devices. Each GNSS receiver may be coupled with a patch antenna, helical antenna,
or any other type of antenna.
The location-determining component 106 may also comprise other type of receiving
devices capable of receiving location information from at least three transmitting locations and
performing basic triangulation calculations to determine the relative position of the receiving
device with respect to the transmitting locations. For example, cellular towers or any customized
transmitting radio frequency towers can be used instead of satellites. With such a configuration,
any standard geometric triangulation algorithm can be used to determine the exact location of the
receiving unit.
Some or all of the components of the control system 100 may be enclosed in or supported
on a weatherproof housing for protection from moisture, vibration, and impact. The housing
may be positioned anywhere on or near the irrigation system and may be constructed from a
suitable vibration- and impact-resistant material such as, for example, plastic, nylon, aluminum,
or any combination thereof and may include one or more appropriate gaskets or seals to make it
substantially waterproof or resistant.
The above-described components of the control system 100 need not be physically
connected to one another since wireless communication among the various depicted components
is permissible and intended to fall within the scope of the present invention. Thus, portions of
the control system 100 may be located remotely from the irrigation system and from each other.
Certain operational aspects of the control system 100 will now be described. The control
system 100 controls operational aspects of the irrigation system such as the speed and direction
of the mobile towers, and hence the speed of the irrigation system, via control signals provided to
the relays connected to the motors 22A-D of the mobile towers 11A-D. Likewise, the control
system 100 controls the water flow through the water emitters 26A-P via control signals provided
to the relays connected to the valves 28A-D. The control system may also control other
operational aspects such as a fertilizer application rate, a pesticide application rate, end gun
operation, mobile tower direction (forward or reverse), and/or system start-up and/or shut-down
procedures.
The control system 100 may control some of the above-described operational aspects of
the irrigation system in accordance with an irrigation plan (also sometimes referred to as a
Asprinkler chart@ or Awatering plan@). An irrigation plan specifies how much water to apply to
a field, and sometimes to different portions of a field, based on various different criteria such as
the types of crops to be irrigated; the soil conditions in various parts of the field; the existence of
slopes, valleys, etc. in the field; the existence of roads, buildings, ponds, and boundaries that
require no irrigations; crop growth cycles; etc. One or more irrigation plans may be created then
stored in the memory 104 or otherwise be accessible by the computing device 102.
An exemplary irrigation plan will now be described with reference to Fig. 3, which shows
a circular field 300 or portion of a field divided into a number of wedge-shaped sections 302-
316. The field is shown divided into 8 equal-sized sections, but it may be divided into any
number of sections of any size. The figure also depicts a four-span irrigation system 10
operating in the field. Each of the wedge-shaped sections may require different amounts of
irrigation for the reasons discussed above.
An irrigation plan that corresponds to the field shown in Fig. 3 indicates how much water
is desired in each of the wedge-shaped sections 302-316. For example, the irrigation plan may
call for 10 G.P.M. in section 302, 20 G.P.M. in section 304, 0 G.P.M. in section 306, etc. This
particular irrigation plan is likely for an irrigation system in which all the water emitters are
turned on or off together (only one valve for the entire irrigation system) because each wedge-
shaped section is not further sub-divided into smaller sections served by just some of the water
emitters.
Another exemplary irrigation plan will now be described with reference to Fig. 4, which
shows a circular field 400 or portion of a field divided into a number of wedge-shaped sections
402-416, with each wedge-shaped section further sub-divided into a number of annulus sectors
identified by the letters A-D. The field is shown divided into 8 equal-sized wedge-shaped
sections, and each wedge is subdivided into 4 annulus sectors, each corresponding to one span of
the irrigation system in a particular position in the field. However, the field may be divided into
any number of sections and sectors of any size. At least some of the sections and/or annulus
sectors may require different amounts of irrigation for the reasons discussed above.
An irrigation plan that corresponds to the field shown in Fig. 4 indicates how much water
is desired in each of the annulus sectors. This irrigation plan is likely for an irrigation system
that has a separate valve for each span of the irrigation system such that the water emitters on
each span may be controlled separately from the water emitters on other spans. For example,
annulus sector 402B may receive a different amount of water than annulus sector 402D even
through both sectors are within the same wedge-shaped section 402.
The irrigation plans described above and/or other irrigation plans may be stored in the
memory 104 or may otherwise be accessible by the computing device 102. Each irrigation plan
includes data that represents the geographical boundaries of each of its sections and sectors and
data that represents the desired fluid amount or flow rate in the sections and sectors. For
example, an irrigation plan may include data that represents the boundaries or position of annulus
section 402D and a desired water flow rate of 15GPM in this sector. When the irrigation system
is operating, the control system 100 adjusts the speed of the mobile towers, the positions of the
valves, and/or other operational aspects of the irrigation system to achieve the amount of
irrigation prescribed by one of the irrigation plans in the sections and sectors.
Those skilled in the art will appreciate that these are merely examples of irrigation plans
and that a nearly endless number of irrigation plans may be created for the irrigation system 10.
A more detailed explanation of irrigation plans is provided in U.S. Patent No. 8,739,830, which
is incorporated by reference into the present applicant in its entirety.
Even when controlled by an irrigation plan, the irrigation system 10 may fail to deliver
the prescribed amounts of water for the reasons discussed above. The present invention solves
this problem by providing a system and method for calibrating the irrigation system 10 to
account for variations in flow rates caused by field elevation changes, pipe friction losses, water
emitter nozzle wear, pressure-regulator inaccuracies, and other factors. In general, the invention
first creates a calibration map to assess and record the above-described flow rate variations and
then controls operation of the irrigation system 10 in accordance with the calibration map.
To create a calibration map, actual flow rates through the irrigation system 10, or portions
of the irrigation system, are periodically or continuously measured and recorded as the irrigation
system 10 moves across a field. These measured flow rates are then compared to expected flow
rates through the irrigation system, or portions of the irrigation system, based on the original
design or configuration of the irrigation system. Correction factors that account for the
differences between the measured flow rates and the expected flow rates are then created for
different portions or sections of the field. For example, if the measured flow rate in a first
section is 5% less than expected, a correction factor of +5% is assigned to that section to indicate
% more water is required in that section. Similarly, if the measured flow rate in a second
section is 10% more than expected, a correction factor of -10% is assigned to that section to
indicate 10% less water is required in that section. The correction factors and geographic
coordinates or other positional information for the corresponding field sections are then stored in
the calibration map.
The calibration map may be created while the irrigation system is operating in a
calibration mode or Aon-the-fly@ while the irrigation system is irrigating a field. The calibration
map may be created when the irrigation system is first placed into service and may be
periodically or continuously updated to account for changing conditions such as degradation of
the valves, water emitters, pressure regulator and/or other components of the irrigation system.
Creation of exemplary calibration maps will now be described in more detail with
reference to the exemplary irrigation plans described above. Although each calibration map may
correspond to a particular irrigation plan, the calibration maps are not necessarily linked to
particular irrigation plans and may be used to calibrate any number of irrigation plans or even an
irrigation system that is not operating under the direction of an irrigation plan.
A first exemplary calibration map is graphically represented in Fig. 5 and may correspond
to the field represented in Fig. 3 and the irrigation plan created for this field. As depicted, the
calibration map has correction factors for each pie-shaped section 302-316 of the irrigation plan.
The correction factors are shown as percentages but may be in other forms such as fractions,
decimals, or other data. This calibration map corresponds to an irrigation system that does not
control individual water emitters or banks of water emitters but instead controls all of the water
emitters with a single valve.
The calibration map represented in Fig. 5 is created by measuring and recording actual
flow rates through the irrigation system, or portions of the irrigation system, while it operates in
each of the sections 302-316. These measured flow rates are then compared to expected flow
rates through the irrigation system, or portions of the irrigation system, for the same sections.
Differences between the measured flow rates and the expected flow rates for the sections are then
calculated to create correction factors for each section of the field. For example, section 302
shows a correction factor of +10%, which indicates the measured flow rates for section 302 are
% below the expected flow rates and therefore 10% more water is required for that section.
Similarly, section 310 shows a correction factor of -15%, which indicates the measured flow
rates for that section are 15% above the expected flow rates and therefore 15% less water is
required for that section.
Fig. 5 is just a graphical representation of the first calibration map. In actual
implementation, the calibration map is likely stored as a table, database, or other data structure,
with data corresponding to the geographical coordinates of the sections 302-316 and the
correction factors for each section.
A second exemplary calibration map is graphically represented in Fig. 6 and may
correspond to the field represented in Fig. 4 and the irrigation plan created for this field. The
calibration map has correction factors for at least some of the annulus sectors, and preferably all
the sectors, but the figure only includes a few representative correction factors. This calibration
map likely corresponds to an irrigation system that has a separate valve for each span of the
irrigation system such that the water emitters on each span may be controlled separately from the
water emitters on other spans.
The second calibration map is created in a similar manner as the first calibration map but
requires extra steps to account for the annulus sectors. This calibration map is created by
measuring and recording actual flow rates through each span of the irrigation system while it
operates. During a calibration pass, the control system toggles or otherwise controls individual
water emitters, or banks of water emitters, on and off by operating the valves 28A-D. The
control system determines how much water is actually being emitted from individual water
emitters, or banks of water emitters, by comparing changes in the overall flow rate through the
irrigation system as the water emitters are toggled. For example, the control system may close
the water emitters on the outermost span of the irrigation system, but leave all other water
emitters fully open, and then note how much the total water flow through the irrigation system
dropped. Because the pressure regulator maintains a relatively constant water pressure in the
irrigation system even as valves are opened and closed, the water flow reduction approximates
the amount of water flow through the water emitters on the outermost span of the irrigation
system when they are fully open. These steps may be repeated for every group of water emitters,
and even for individual water emitters, for each annulus sector of the field.
These measured flow rates are then compared to expected flow rates through the spans
for the sectors. Differences between the measured flow rates and the expected flow rates for the
sectors are then determined to create correction factors for each annulus sector of the field. For
example, sector 402D shows a correction factor of +10%, which indicates the measured flow
rates for that sector are 10% below the expected flow rates for that sector and therefore 10%
more water is required for that sector. Similarly, sector 408C shows a correction factor of -15%,
which indicates the actual flow rates for that sector are 15% above the expected flow rates and
therefore 15% less water is required for that sector.
Once a calibration map is created, the control system 100 consults the calibration map
during operation of the irrigation system to adjust at least one operational aspect of the irrigation
system in accordance with the correction factors. For example, if an irrigation plan or an initial
setting of the irrigation system calls for 10 gallons per minute (G.P.M.) of water in a section or
sector of the field, but the calibration map indicates a +10% correction factor for the section or
sector, the control system adjusts an operational aspect of the irrigation system so as to apply
% more water than it would have without the calibration map. The operational aspect that is
adjusted may be the speed of the irrigation system=s mobile towers, a duty cycle of the irrigation
system=s water emitters, a water flow rate of individual water emitters or banks of water
emitters, or anything else that controls the rate of fluid flow of the irrigation system to adjust
water flow rates in accordance with the correction factors. For example, the control system may
operate the mobile towers 10% slower than called for by the irrigation plan or the initial setting
of the irrigation system so as to apply 10% more water.
The above-described calibration maps can also be used to detect faults in an irrigation
system such as leaks, valves stuck open, end guns stuck open, abnormally high system water
pressures, blocked water emitter nozzles, valves stuck closed, end guns stuck closed, and
abnormally low system water pressures. For example, if a calibration map indicates measured
water flow rates are much higher than expected for multiple sections or sectors of a field, this
may indicate a leak, valve stuck open, or end gun stuck open. By successively toggling different
valves or banks of valves, the control system can isolate which water emitters or banks of water
emitters that are stuck open or closed.
When a calibration map is updated, the control system may compare the most current
version of the calibration map to one or more previous versions of the calibration map to detect
changes in the correction factors. These changes, if gradual, may indicate normal and expected
water flow variations, but if significant, may indicate problems such as stuck valves, leaks,
and/or other defects.
The flow chart of Fig. 7 shows the functionality and operation of an exemplary method
700 of the present technology. Some of the blocks of the flow chart may represent a step in the
method 700 and/or a module section or portion of code of computer programs the operate the
control system 100. In some alternative implementations, the functions noted in the various
blocks may occur out of the order depicted in Fig. 7. For example, two blocks shown in
succession in Fig. 7 may in fact be executed substantially concurrently, or the block may
sometimes be executed in the reverse order depending upon the functionality involved.
The method 700 begins in step 702 where the control system operates the mobile towers
to move the irrigation system over a ground surface. The control system may operate the mobile
towers and water emitters in accordance with an irrigation plan or initial settings of the irrigation
system.
In step 704, the control system receives position or orientation information for the mobile
towers 16A-D. The position or orientation information may be obtained from the location-
determining component 106 or a similar device. This step, and all other steps of the method,
may be performed in a different order. For example, the position of the irrigation system may be
determined after and/or during steps 706 and 708.
In step 706, the control system 100 toggles the water emitters as the irrigation system
moves over the ground surface. In step 708, the control system 100 measures flow rates through
the irrigation system as the irrigation system moves over the ground surface and as the water
emitters are toggled. Steps 706 and 708 allow the control system to determine actual flow rates
through specific water emitters or banks of water emitters as described above. The toggling step
is not required for an irrigation system with a single valve that controls water delivery to all the
water emitters.
In step 710, the control system 100 compares the measured flow rates to expected flow
rates. This step and other steps may be repeated for every section and sector of the field as
described above.
In step 712, the control system 100 creates a calibration map that reflects differences
between the measured flow rates and the expected flow rates in the sections and sectors. As
discussed above, the calibration map includes correction factors for different sections and/or
sectors. These correction factors account for the differences between the measured flow rates
and the expected flow rates in the sections or sectors and are used to adjust operational aspects of
the irrigation system.
In step 714, the control system 100 calibrates operation of the irrigation system 10 with
the calibration map by adjusting at least one operational aspect of the irrigation system to account
for the differences between the measured flow rates and the expected flow rates. The operational
aspects of the irrigation system that can be adjusted may be a speed of the mobile towers, a duty
cycle of the water emitters, a water flow rate of the water emitters, or anything else that controls
the rate of fluid flow of the irrigation system.
Some of the above-described steps may be performed by the control system 100 and/or an
external computing device not located on the irrigation system. The external computing device
may communicate with the control system 100 or directly with the drive motors 22A-D and/or
the valves 28A-D via wireless communication channels.
Although the invention has been described with reference to the embodiments illustrated
in the attached drawing figures, it is noted that equivalents may be employed and substitutions
made herein without departing from the scope of the invention as recited in the claims. For
example, the principles of the present invention are not limited to the illustrated central pivot
irrigation systems but may be implemented in any type of irrigation system including linear move
irrigation systems.
Having thus described the preferred embodiment of the invention, what is claimed as new
and desired to be protected by Letters Patent includes the following:
Claims (16)
1. A method of calibrating an irrigation system having a plurality of mobile towers and a plurality of water emitters supported by the mobile towers, the method comprising: operating the mobile towers in accordance with an irrigation plan to move the irrigation system over a ground surface and to apply selected and different amounts of fluids to a plurality of sections of the ground surface; determining positions of the irrigation system as it moves; measuring flow rates through the irrigation system for each of the sections as the irrigation system moves over the ground surface; comparing the measured flow rates to expected flow rates for each of the sections; creating a calibration map that reflects differences between the measured flow rates and the expected flow rates for each of the sections, the calibration map including a separate correction factor for each of the sections, wherein each of the correction factors accounts for differences between the measured flow rate and the expected flow rate for its respective section and not any of the other sections; and calibrating operation of the irrigation system with the calibration map by adjusting an operational aspect of the irrigation system for each of the sections in accordance with the separate correction factors for the sections to account for the differences between the measured flow rates and the expected flow rates for each of the sections so that each of the sections is calibrated independently.
2. The method as set forth in claim 1, wherein the operational aspect of the irrigation system is selected from the group consisting of a speed of the mobile towers, a duty cycle of the water emitters, and a water flow rate of the water emitters.
3. The method as set forth in claim 1, wherein the steps are performed during a calibration run of the irrigation system or while the irrigation system is irrigating the ground surface.
4. The method as set forth in claim 1, further including the step of toggling the water emitters as the irrigation system moves over the ground surface.
5. The method as set forth in claim 4, wherein the toggling step comprises turning a set of the water emitters off, and wherein the measuring step determines the measured flow rates for the set of water emitters by measuring a reduction in flow rates through the irrigation system when the set of water emitters are turned off.
6. The method as set forth in claim 5, wherein the measuring step is performed with a single flow rate sensor that senses flow rates through the entire irrigation system.
7. The method as set forth in claim 1, further including the steps of: toggling the water emitters as the irrigation system moves over the ground surface; determining positions of the irrigation system as the irrigation system moves over the ground surface and as the water emitters are toggled to determine which section is being traversed; and measuring flow rates through the irrigation system for each of the sections as the irrigation system moves over the ground surface and as the water emitters are toggled.
8. The method as set forth in claim 7, wherein the operational aspect of the irrigation system is selected from the group consisting of a speed of the mobile towers, a duty cycle of the water emitters, and a water flow rate of the water emitters.
9. The method as set forth in claim 7, wherein the toggling step comprises turning a set of the water emitters off while leaving other water emitters on.
10. The method as set forth in claim 7, wherein the measuring step measures a flow rate reduction as the set of water emitters are turned off, and wherein the comparing step compares the flow rate reduction to expected flow rates for the set of water emitters, and wherein the calibration map reflects differences between the measured flow rate reduction and the expected flow rates for the set of water emitters.
11. An irrigation system comprising: a series of mobile towers each having wheels and a motor for driving the wheels; support structure for connecting the mobile towers to each other; a water-carrying conduit supported by the support structure; a plurality of water emitters connected to the conduit for delivering water to a ground surface; a plurality of valves for controlling water flow to the water emitters; and a control system for controlling operation of the mobile tower motors and the valves, the control system programmed to: operate the mobile towers in accordance with an irrigation plan to move the irrigation system over a ground surface and to apply selected amounts of fluids to a plurality of sections of the ground surface; toggle the valves as the irrigation system moves over the ground surface; determine positions of the irrigation system as the irrigation system moves over the ground surface and as the valves are toggled to determine which section is being traversed; measure fluid flow rates through the irrigation system for each of the sections as the irrigation system moves over the ground surface and as the valves are toggled; compare the measured flow rates to expected flow rates for the determined positions of the irrigation system for each of the sections; create a calibration map that reflects differences between the measured flow rates and the expected flow rates for each of the sections, the calibration map including a separate correction factor for each of the sections, wherein each of the correction factors accounts for differences between the measured flow rate and the expected flow rate for its respective section and not any of the other sections; and calibrate operation of the irrigation system with the calibration map by adjusting an operational aspect of the irrigation system for each of the sections in accordance with the separate correction factors for the sections to account for the differences between the measured flow rates and the expected flow rates for each of the sections.
12. The irrigation system as set forth in claim 11, wherein the operational aspect of the irrigation system is selected from the group consisting of a speed of the mobile towers, a duty cycle of the water emitters, and a water flow rate of the water emitters.
13. The irrigation system as set forth in claim 11, further comprising a central pivot to which the support structure is attached.
14. The irrigation system as set forth in claim 11, wherein the control system is positioned on the irrigation system.
15. The irrigation system as set forth in claim 11, wherein the control system is positioned remotely from the irrigation system.
16. The irrigation system as set forth in claim 11, wherein some components of the control system are positioned on the irrigation system and other components of the control system are positioned remotely from the irrigation system.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US15/891,977 US10827692B2 (en) | 2018-02-08 | 2018-02-08 | System and method for calibrating an irrigation system |
US15/891,977 | 2018-02-08 |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ750501A NZ750501A (en) | 2021-07-30 |
NZ750501B2 true NZ750501B2 (en) | 2021-11-02 |
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