Patent Description:
The present invention relates generally to a system and method for providing correction and position signals to various powered elements within an irrigation machine to achieve a variety of objectives, including alignment control of irrigation spans, guidance of irrigation machines (e.g. corners and linears) and to provide positional information to a variety of remote monitoring and control devices.

Modern center pivot and linear irrigation systems generally include interconnected spans (e.g., irrigation spans) supported by one or more tower structures to support the conduits (e.g., water pipe sections). In turn, the conduits are further attached to sprinkler/nozzle systems which spray water (or other applicants) in a desired pattern. In these modern irrigation systems, a significant number of powered elements are used to control various aspects of irrigation. These often include a variety of sensors, sprayers, drive control systems, motors and transducers.

In the past, irrigation machines have utilized a variety of approaches to communicate data between system processors. These approaches have included dedicated hard-wired systems (e.g. RS485, TCP/IP, RS232, etc.) and wireless systems (e.g. cellular, Wi-Fi, VHF/UHF radios, spread spectrum radios and the like). Both of these solutions are costly and prone to communication errors. Hard-wired systems require the installation of significant lengths cable and wireless systems often require repeater stations to boost the radio signals over long distances. Further, wireless systems have poor reliability due to distance, weather changes, obstacles, induced RF noise and long latencies, particularly with cellular communications. Both systems have caused errors in position reporting and have caused system delays due to failed communications. The end result of these errors has been poor water application uniformity, delays in application and other problems which have reduced yields and profitability for growers.

To overcome the limitations of the prior art, a reliable and effective communication and control system is needed to control and align irrigation spans and drive towers within a mechanized irrigation system. Further, a system is needed to provide guidance to steerable elements of the irrigation machine and to provide locational awareness of the machine (positional information) to a machine control system and to remote operators. <CIT>), <CIT> and <CIT> (Beusch G. et al) illustrate such a prior systems.

To address the shortcomings presented in the prior art, the present invention provides a system for providing improved communications and locational awareness within an irrigation system having at least one span and a drive system for moving the spans.

The present invention is defined by the attached independent claims. Other preferred embodiments may be found in the dependent claims. The present application discloses a method (<NUM>, <NUM>) for aligning spans (<NUM>, <NUM>), wherein the method is for a system (<NUM>, <NUM>) comprises a plurality of connected spans (<NUM>, <NUM>) and a plurality of drive towers (<NUM>, <NUM>, <NUM>, <NUM>) for moving the connected span around a center pivot having a pivot controller (<NUM>); wherein each drive tower is comprised of a power line (<NUM>, <NUM>) carrier node; further wherein the drive towers include intermediate drive towers and a last drive tower, further wherein the system comprises a fixed reference station (<NUM>, <NUM>) storing reference location data; the method characterised in using real-time kinetics (RTK) data communicated through a power line carrier system and wherein the method comprises: receiving a first set of GPS location data (320d: <NUM>, <NUM>); comparing the first set of GPS location data with the reference location data stored in the fixed reference station; calculating RTK error correction data; creating an RTK error correction data signal (<NUM>, <NUM>); modulating the RTK error correction data signal for transmission on a power line carrier; wherein the power-line carrier is comprised of a plurality of electrically conductive elements which are configured to connect and deliver signals to and from a power-line BUS (<NUM>, <NUM>); transmitting the RTK error correction data signal (<NUM>, <NUM>) through the power line BUS onto the power line to the power line carrier node of each drive tower; de-modulating the RTK error correction data signal; calculating the location of the last drive tower using the RTK error correction data; calculating (<NUM>) a center line between the pivot and the last drive unit; calculating the relative distances between each intermediate drive tower and the calculated (<NUM>) center line; wherein the distance calculation is made using a linear regression algorithm; and controlling the speed of each intermediate drive tower to reduce distance between their current locations and the calculated center line. The present application discloses a system (<NUM>; <NUM>) comprising a plurality of connected spans (<NUM>, <NUM>) and a plurality of drive towers (<NUM>, <NUM>, <NUM>, <NUM>) for moving the connected span around a center pivot having a pivot controller (<NUM>); wherein the plurality of drive towers includes a first drive tower, a last drive tower and a corner drive tower; wherein each of the plurality of drive towers comprises a tower controller (<NUM>, <NUM>, <NUM>, <NUM>) and power line (<NUM>, <NUM>) carrier node; further wherein the system comprises a fixed reference station for storing reference location data, the system operated in accordance with any of claims <NUM> to <NUM> comprising: receiving a first set of GPS location data; comparing the first set of GPS location data (<NUM>, <NUM>) with reference location data stored in the fixed reference station (<NUM>, <NUM>); calculating RTK error correction data (<NUM>); wherein the RTK error correction data is calculated using at least the first set of GPS location data and the reference location data; creating an RTK error correction data signal, wherein the RTK error correction data signal comprises RTK error correction data; modulating the RTK error correction data signal for transmission on a power line carrier; wherein the power-line carrier is comprised of a plurality of electrically conductive elements which are configured to connect and deliver signals to and from a power-line BUS via a power line; transmitting the RTK error correction data signal through the power line BUS onto the power line to the power line carrier node of each drive tower; demodulating the RTK error correction data signal at the corner drive tower; calculating the location of the corner drive tower using the RTK error correction data; comparing the calculated location of the corner drive tower to a target location for the corner drive tower; wherein the step of comparing comprises calculating a distance between the calculated location of the corner drive tower and the target location of the corner drive tower; wherein the distance calculation is made using a linear regression algorithm; and controlling the speed of the corner drive unit to reduce the distance between the calculated location and the target location of the corner drive unit.

For the purposes of promoting an understanding of the principles of the present invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the present invention is hereby intended and such alterations and further modifications in the illustrated devices are contemplated as would normally occur to one skilled in the art.

In accordance with preferred embodiments of the present invention, it should be understood that the term "drive unit" may preferably include a number of sub-components including: a motor, a controller, a communication device (such as a PLC or the like) and an alignment device. Further, while the invention is discussed below with respect to four exemplary towers, the number of towers used may be expanded or reduced (i.e. <NUM>-<NUM> towers) as needed without departing from the spirit of the present invention. Further, the term "motor" as used herein may refer to any suitable motor for providing torque to a drive wheel. Accordingly, the term "motor" as used herein may preferably include motors such as switch reluctance motors, induction motors and the like.

The terms "program, "computer program, "software application, "module," firmware" and the like as used herein, are defined as a sequence of instructions designed for execution on a computer system. The term "solid state" should be understood to refer to a range of solid state electronic devices which preferably include circuits or devices built from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material. Exemplary solid-state components/materials may include crystalline, polycrystalline and amorphous solids, electrical conductors and semiconductors. Common solid-state devices may include transistors, microprocessor chips, and RAM.

A program, computer program, module or software application may include a subroutine, a function, a procedure, an object implementation, an executable application, an applet, a servlet, a source code, an object code, a shared library, a dynamic load library and/or other sequence of instructions designed for execution on a computer system. A data storage means, as defined herein, includes many different types of computer readable media that allow a computer to read data therefrom and that maintain the data stored for the computer to be able to read the data again. Such data storage means can include, for example, non volatile memory, such as ROM, Flash memory, battery backed-up RAM, Disk drive memory, CD-ROM, DVD, and other permanent storage media. However, even volatile storage such a RAM, buffers, cache memory, and network circuits are contemplated to serve as such data storage means according to different embodiments of the present invention.

Aspects of the systems and methods described herein may be implemented as functionality programmed into any of a variety of circuitry, including programmable logic devices (PLDs), such as field programmable gate arrays (FPGAs), programmable array logic (PAF) devices, electrically programmable logic and memory devices and standard cell-based devices, as well as application specific integrated circuits (ASICs). Some other possibilities for implementing aspects of the systems and methods includes: microcontrollers with memory, embedded microprocessors, firmware, software, etc. Furthermore, aspects of the systems and methods may be embodied in microprocessors having software-based circuit emulation, discrete logic (sequential and combinatorial), custom devices, fuzzy (neutral network) logic, quantum devices, and hybrids of any of the above device types. Of course, the underlying device technologies may be provided in a variety of component types, e.g., metal-oxide semiconductor field-effect transistor (MOSFET) technologies like complementary metal-oxide semiconductor (CMOS), bipolar technologies like emitter - coupled logic (ECF), polymer technologies (e.g., silicon-conjugated polymer and metal- conjugated polymer-metal structure), bidirectional triode thyristors (TRIAC), mixed analog and digital, and the like.

As shown in <FIG> , the exemplary system <NUM> shown includes a span <NUM> which preferably includes a series of connected span sections which may be pressurized to facilitate the transfer of water from a water source through the irrigation system <NUM>. The fluid source may be coupled to a repository or other source of agricultural products to inject fertilizers, pesticides, and/or other chemicals into the fluids to create an applicant for application during irrigation. Thus, the applicant may be water, fertilizer, herbicide, pesticide, combinations thereof, or the like. The exemplary system <NUM> may further include a main control panel <NUM> which may control transducers, sensors and valves (not shown) to control and regulate water pressure to sprinklers (not shown) including an end gun <NUM> and other sprinkler heads (not shown).

As further shown, the system may include drive towers <NUM>, <NUM>, <NUM>, <NUM> having respective tower control boxes <NUM>, <NUM>, <NUM>, <NUM>. As further shown, these tower control boxes may be interfaced with respective alignment sensors <NUM>, <NUM>, <NUM>, <NUM> and control respective drive unit motors <NUM>, <NUM>, <NUM>, <NUM>. As discussed above, the system of the present invention may include any motor suitable for providing torque to a drive wheel or wheels. According to a preferred embodiment, the system of the present invention may preferably include motors such as switch reluctance motors, induction motors and the like.

With reference now to <FIG>, an exemplary control device <NUM> which represents functionality to control one or more operational aspects of the irrigation system <NUM> will now be discussed. As shown, an exemplary control device <NUM> preferably includes a processor <NUM>, a memory <NUM>, a data storage module <NUM> and a network interface <NUM>. The processor <NUM> provides processing functionality for the control device <NUM> and may include any number of processors, micro-controllers, or other processing systems. The processor <NUM> may execute one or more software programs that implement techniques described herein. The memory <NUM> is an example of tangible computer-readable media that provides storage functionality to store various data associated with the operation of the control device <NUM>, such as the software program and code segments mentioned above, or other data to instruct the processor <NUM> and other elements of the control device <NUM> to perform the steps described herein. The memory <NUM> may include, for example, removable and non- removable memory elements such as RAM, ROM, Flash (e.g., SD Card, mini-SD card, micro-SD Card), magnetic, optical, USB memory devices, and so forth. The network interface <NUM> provides functionality to enable the control device <NUM> to communicate with one or more networks <NUM> through a variety of components such as wireless access points, transceivers and so forth, and any associated software employed by these components (e.g., drivers, configuration software, and so on). As shown, a preferred system of the present invention may include a satellite transceiver <NUM> or the like for receiving direct satellite communications.

In implementations, exemplary control device <NUM> preferably further includes a power control system <NUM>, a power line control (PLC) board <NUM> and a power-line BUS <NUM>. According to a preferred embodiment of the present invention, the power-line BUS <NUM> preferably may include conductive transmission lines, circuits and the like for controlling and routing electric power, controlling its quality, and controlling the devices attached to a power line carrier system as discussed further below. According to further preferred embodiments, the PLC board <NUM> preferably routes and converts power and data signals which are transmitted through the power- line BUS <NUM> as discussed further below.

Further, the system of the present invention preferably may further include an irrigation position-determining module <NUM> which may further include a global positioning system (GPS) receiver <NUM> or the like to calculate a location of the irrigation system <NUM>. In accordance with a further preferred embodiment of the present invention, the irrigation position determining module <NUM> preferably further includes a real-time kinematics (RTK) Error Calculation Module <NUM> as discussed further below. According to preferred embodiments, the processing of RTK signals as discussed herein may preferably be conducted using a single frequency or dual frequencies without limitation.

As further shown, control device <NUM> may be coupled to a guidance device or similar system <NUM> of the irrigation system <NUM> (e.g., steering assembly or steering mechanism) to control movement of the irrigation system <NUM> and to assist in controlling the movement and locational awareness of the system. Further, the control device <NUM> may preferably further include multiple inputs and outputs to receive data from sensors <NUM> and monitoring devices as discussed further below.

According to a preferred embodiment, the RTK Error Calculation Module <NUM> preferably functions to perform RTK error calculations to enhance the precision of position data derived from the GPS system <NUM>. Although the present invention is discussed with respect to GPS, the present invention applies to data received from other positioning systems such as LORAN, GLONASS, Galileo, BeiDou and the like, as well as any combination of those like systems. Additionally, RTK can utilize a single frequency (commonly known as the LI band) for corrections or can utilize dual frequencies (commonly known as the LI and L2 bands). Further like correction technologies (such as WAAS, or Differential GPS) that enhance positional accuracy may be used. Preferably, any such systems would be compatible with the like positioning systems discussed above and provide positional accuracy better than <NUM> meter.

With reference now to <FIG>, an exemplary system <NUM> incorporating aspects of the present invention shall now be further discussed. As further shown, an exemplary irrigation system <NUM> may include transducers (not shown) which are provided to control and regulate water pressure to sprinklers including the end gun <NUM> and other sprinkler heads <NUM>.

Further the system may preferably include solid state tower boxes <NUM>, <NUM>, <NUM> (including the PLC boards, solid-state motor controllers, non-contact alignment devices and other components as discussed above and further with respect to <FIG> below) which are preferably interconnected to respective drive unit motors <NUM>, <NUM>, <NUM>. As further shown, the respective drive unit motors <NUM>, <NUM>, <NUM> preferably provide torque and braking to respective sets of drive wheels <NUM>, <NUM>, <NUM>. As discussed above, the system of the present invention may include any suitable motor for providing torque to a drive wheel. According to a preferred embodiment, the system of the present invention may preferably include motors such switch reluctance motors, induction motors and the like.

Further, the system <NUM> of the present invention may preferably further include a control/pivot panel <NUM> as well as elements such as a GPS receivers 320a-d for receiving positional data. Still further, a system of the present invention may further include indirect crop sensors <NUM>, <NUM> which preferably may include optional moisture sensors to determine the moisture levels in a given area of soil. Additionally, the sensors <NUM>, <NUM> may further include optics to allow for the detection of crop type, stage of grown, health, presence of disease, rate of growth and the like. Still further, the system may include ground sensors. Still further, the detection system may further receive data from a connected or remote weather station or the like which is able to measure weather features such as humidity, wind speed, wind direction, pressure, precipitation, temperature and the like. Further, the preferred system of the present invention may alternatively further include additional elements mounted to the span <NUM> such as additional sensors and the like.

As further shown in <FIG> and as discussed further below, a preferred system of the present invention may further include a Real Time Kinematic (RTK) reference station <NUM> for providing error correction data to a GPS roving receiver which may be attached to a corner drive tower <NUM> or the like as discussed further below. Preferably, the RTK reference station <NUM> is positioned on a very accurately surveyed point. Still further, the RTK reference station <NUM> preferably receives GPS signals and calculates error correction data based on the location differences between the surveyed location and the location data indicated by the measured GPS signals. According to a further preferred embodiment, a last regular drive unit (LRDU), corner drive tower or cart may preferably include a GPS receiving unit 320d which preferably acts as a roving GPS unit.

With reference now to <FIG>, once the RTK reference station <NUM> (alone and/or in combination with the pivot controller <NUM> and the RTK Error Calculation Module <NUM>), creates error correction data, the error correction data is then preferably transmitted by the pivot controller <NUM> as an error correction data signal to the pivot point PLC board <NUM>. The pivot point PLC board <NUM> then preferably modulates the error correction data signal and transmits the signal through the power line BUS <NUM> and PLC system to one or more downstream GPS units/controllers <NUM>, <NUM>, <NUM>. In this way, each receiving GPS unit/controller of the present invention receives enhanced RTK guidance. According to a further preferred embodiment, the GPS units/controllers <NUM>, <NUM>, <NUM> of the present invention may further transmit GPS location data to the pivot controller <NUM> to provide additional locational awareness.

According to a further preferred embodiment, the RTK reference station <NUM> may preferably be located within a collector ring/slip ring device <NUM> attached to the center pivot point. According to alternative preferred embodiments, the location (longitude, latitude) of the RTK reference station may be set by any method known in the art. For example, the RTK reference station location may be manually set by user input from data gathered outside the system. Alternatively, the RTK reference station location may be set via a "survey mode" where the location of the unit is determined using known algorithms to time-average GPS positional data gathered by the receiver.

With further reference now to <FIG>, the power/control system of the present invention <NUM> may preferably include a control/pivot panel box <NUM> which preferably provides control signals and power to a series of intermediate solid-state tower boxes <NUM>, <NUM> and a last regular drive unit (LRDU)/cart/rover tower box <NUM>. As shown, each solid- state tower box <NUM>, <NUM>, <NUM> preferably further includes a GPS sensor/input <NUM>, <NUM>, <NUM>. It should be understood that solid-state tower boxes are provided as an example and the present invention is not intended to be limited to the use of solid-state tower boxes. For example, electro - mechanical tower boxes may be used with the PLC system of the present invention in place of the solid-state tower boxes without departing from the scope of the present invention.

As further shown, the control/ pivot panel box <NUM> of the present invention may preferably include a main pivot controller <NUM> connected to a pivot point PLC board <NUM> which controls and directs power to downstream intermediate solid-state tower boxes <NUM>, <NUM> and corner drive tower/cart/rover tower box <NUM>. According to a preferred embodiment, the pivot controller <NUM> may be directly wired to the pivot point PLC board <NUM> or connected via a serial communication connection <NUM> (i.e. RS-<NUM>) or the like. According to preferred embodiments, the pivot panel box <NUM> preferably provides power and control signals through the pivot point PLC board <NUM> to the downstream solid-state tower boxes <NUM>, <NUM>, <NUM> via a power-line BUS <NUM>.

According to preferred embodiments, the power-line BUS <NUM> of the present invention may provide and direct power at any of a variety of different voltages and amps. For example, the power-line BUS <NUM> of the present invention may provide power over a range of voltages (such as between <NUM>-<NUM> volts) and over a range of currents (such as. <NUM> to <NUM> amps) as desired without limitation. According to a further preferred embodiment, the power may be provided at <NUM>-<NUM> volts with a current anywhere between <NUM>-<NUM> amps. For instance, the power- line BUS <NUM> may provide <NUM> volts AC at <NUM> amps. According to a further preferred embodiment, the power-line BUS <NUM> may preferably provide power at <NUM> volts AC at <NUM> amps. According to a further preferred embodiment, the power-line carrier of present invention may preferably operate as a one or two-way system.

As further shown in <FIG>, the RTK data is preferably first received by the RTK reference station <NUM> which may be located within a collector ring <NUM> attached to the riser. Thereafter, the data is provided to the RTK Error Calculation Module <NUM> to calculate and produce GPS error correction data. Thereafter, the RTK Error Calculation module <NUM> preferably transmits the RTK error correction data to the pivot point PLC board <NUM> where the signal is modulated and transmitted (along with power and control signals provided by the power-line box <NUM>) to the downstream solid-state tower boxes <NUM>, <NUM>, <NUM> and pivot controller <NUM> via a power- line BUS <NUM>.

The error correction data signal is preferably first received by a first intermediate solid-state tower box <NUM> which preferably receives, processes and thereafter directs the received power to a center drive motor <NUM>. Further, the RTK error correction data is preferably further processed by the intermediate solid-state tower box <NUM> and used to correct/adjust the GPS location data received from the GPS module <NUM>. Thereafter, the power and control signals may be further transmitted to one or more downstream tower boxes <NUM> which likewise process the received signals. Although not shown, any number of additional intermediate solid-state our boxes may be incorporated as needed depending on the size of the irrigation system. Regardless of the number of intermediate solid-state tower boxes, the RTK error correction data and the power from the power-line bus <NUM> are preferably finally received at a corner drive tower box <NUM> which preferably likewise receives and processes the received RTK error correction data as well as directs the received power to a center drive motor <NUM>.

As further shown in <FIG>, the corner drive tower box <NUM> may preferably further include a GPS guidance control (GC) panel <NUM> for receiving and processing guidance control signals. Still further, the corner drive tower box <NUM> may preferably further include a PLC board <NUM> for receiving/transmitting and translating control and power signals between the tower box control panel <NUM> and the other systems communicating through the power- line BUS <NUM> as discussed further below. Further, each tower box <NUM>, <NUM> may preferably further include similar PLC boards (not shown) to provide similar functions.

In operation, the GC system <NUM> mounted on the end of the irrigation machine may preferably receive signals from GPS satellites via a GPS sensor <NUM> or the like and calculate the position of the unit. As discussed above, such calculations may include data from a Wide Area Augmentation System (WAAS) or the like. This data may then be transmitted to the PLC board <NUM> via a conventional wired connection of any type (including being integrated onto the same circuit board as the GPS receiver). Thereafter, the PLC board <NUM> may then preferably transmit the GPS position data to the pivot point PLC board <NUM> which may demodulate and send the signals to the main pivot controller <NUM> where the data may be used to indicate the position (i.e. distance, compass angle etc.) of the irrigation machine relative to the pivot point. The pivot controller <NUM> may then further report the position data via a communications system to a cloud-based remote monitoring and control system to allow a remote operator to know the position of the irrigation machine within the field. Further, the pivot controller <NUM> may use the positional data to activate or deactivate auxiliary sprinklers based on the location of the irrigation machine. Still further, the pivot controller <NUM> may use the positional data to adjust the speed of the machine and/or pulsing rate of sprinklers to comply with a variable rate irrigation prescription as discussed further below. Still further, the pivot controller <NUM> may use the positional data to make further calculations such as calculating slip rate or the like to detect a stuck machine.

With reference now to <FIG> and <FIG>, a preferred method <NUM> in accordance with preferred embodiments of the present invention shall now be discussed. According to a first preferred embodiment, at a first step <NUM>, GPS position data are preferably first received by the fixed (reference) station <NUM>. Alternatively, this data may be input from memory or received from an outside network. According to a preferred embodiment, the GPS data are compared to the reference geographic location stored in the fixed (reference) station. Thereafter, at a next step <NUM>, stored geographic data and GPS data are then preferably processed by the RTK Error Calculation Module <NUM> of the PLC board <NUM> to create RTK error correction data. At a next step <NUM>, the pivot point PLC board <NUM> then preferably modulates the error correction data into a data signal that can be transmitted through the power line BUS <NUM>.

At a next step <NUM>, the RTK error correction data is preferably transmitted to each downstream drive tower controller <NUM>, <NUM>, and <NUM>. Preferably, the data signals are transmitted through the power- line BUS <NUM> to one or more receiving PLC boards within the downstream tower boxes <NUM>, <NUM>, <NUM>. According to a preferred embodiment, an LRDU PLC board <NUM> may receive the correction data and demodulate the received data signal. Thereafter, the PLC board <NUM> may preferably forward the correction data to the corner drive tower box controller <NUM> and/or GC panel <NUM> to use in location refinement and other calculations. According to a preferred embodiment, the frequency of the corrected data transmission may be once per second. Alternatively, the corrected data may be transmitted at faster or slower intervals.

At a next step <NUM>, the location of the corner drive tower <NUM> may preferably be calculated using GPS data and RTK error correction data. At a next step <NUM>, the corner drive tower <NUM> may preferably calculate distance adjustments (preferably using a deviation error or path projection algorithm or the like) and make adjustments to drive speed and/or directions to correct the drive tower location relative to the prescribed drive tower location. For example, the controllers for each drive tower may control their drive wheels to reduce distance between their current locations and a desired guidance path. This may preferably be accomplished by adjusting the duty cycle of a start-stop motor, by increasing or reducing the RPM of a variable speed motor (such as a switch reluctance motor or an induction motor driven by a variable frequency drive) or by like methods.

According to an alternative preferred embodiment, each individual drive tower may increase or reduce its speed to reduce the distance between itself and a center line calculated between the pivot point to the last drive tower in order to maintain substantially straight alignment of the non-corner irrigation spans. Preferably, any such the calculations and/or adjustments by the drive towers of the present invention may be continually performed in real time to maintain alignment during irrigation. Additionally, the RTK correction signal may preferably be sent out in real-time to allow each tower controller to correct GPS errors in real time.

According to an alternative preferred embodiment, the speed of a drive wheel may be controlled by adjusting or changing the programmed average speed of the drive wheel. The present invention may thus continually update the programmed average speed of each tower as necessary and may continually cycle between location detection and updating of programmed average speeds of each tower to minimize the misalignment of towers.

According to further preferred embodiments, the alignment algorithms of the present invention may operate when the machine is still or during the running of the irrigation system. Further, the algorithms and systems of the present invention may be used to initially align the towers every time the machine is started (i.e., at the beginning of the machine movement) rather than during machine movement. According to a further preferred embodiment, the algorithm of the present invention may preferably include a margin error so that only towers located more than a set distance (i.e. two inches) from a given centerline are instructed to reduce detected alignment errors. According to a further preferred embodiment, the order of alignment may be determined in the order of the outermost tower to the innermost tower. Further, the instructions for realigning the towers may be prioritized from the outermost tower to the innermost tower.

With reference now to <FIG> and <FIG>, an alternative alignment method <NUM> for use with the present invention shall now be discussed. According to an exemplary alternative algorithm, at a preferred first step <NUM>, the pivot controller <NUM> of the present invention preferably receives a first set of GPS location data. According to a preferred embodiment, the GPS data may be received directly by GPS satellite receivers. Alternatively, this data may be input from memory or received from an outside network.

At a next step <NUM>, the pivot controller <NUM> preferably compares the GPS location data with the reference geographic location stored in the fixed (reference) station. At a next step <NUM>, the pivot controller <NUM> preferably calculates RTK error correction data. At a next step <NUM>, the RTK error correction data is preferably transmitted to each downstream drive tower controller <NUM>, <NUM>, <NUM> via the power line carrier network.

At next step <NUM>, each tower control unit may preferably broadcast corrected position data to adjacent drive tower controllers. According to a preferred embodiment, each tower control unit may transmit corrected position data via a connected PLC board. According to alternative preferred embodiments, the corrected position data may be transmitted directly between drive tower controllers or may first be transmitted to the central pivot point controller <NUM> which may then store and transmit location data to each drive controller through the PLC BUS <NUM>. At a next step <NUM>, each pair of adjacent towers may preferably calculate a straight, center line between themselves using the corrected position data. At a next step <NUM>, the drive towers may calculate their relative distances to the calculated center line. At a next step <NUM>, the controller for each drive tower may then control a set of drive wheels to reduce distance between their current location and the calculated center line. For example, a motor may preferably be controlled to increase its speed so that the distance between itself and the center line is reduced while the irrigation machine travels in a given direction thus reducing the angular offset between drive towers.

Preferably, multiple groups of towers may act simultaneously to align themselves and to continually updated center lines. For example, the system may preferably analyze and align multiple three tower groups at the same time. Further, the "three-tower alignment" may preferably be run at every tower along the machine, beginning with the tower closest to the end tower and proceeding inward. The alignment may preferably be run simultaneously amongst all the towers. Additionally, the pivot controller <NUM> may preferably continually send out real-time kinematics (RTK) signals to all of the downstream towers to allow each tower controller to correct GPS errors and calculate correction location data.

According to a further preferred embodiment, all the towers may be continuously aligned until all the "delta" lengths are within a certain threshold for alignment. During the alignment process, the end tower may preferably be moving to minimize stress on the span. According to further aspects of the present invention, it should be understood that the use of groups of three towers as discussed above is provided as a preferred example only. Alternatively, any other number of towers may be used as a group as well.

According to alternative embodiments, the present invention may utilize analog sensors on each tower. For example, a LORAN device could be located on each tower and the system may then, for example, utilize the three-tower alignment algorithm in conjunction with the triangulation data from the LORAN devices. Further, LORAN could also be utilized as a backup to the GPS sensors, in case the GPS sensors failed or became unavailable.

According to a further preferred embodiment, the GPS sensor of the present invention may preferably be placed as low to the ground as possible. Further, where a GPS sensor needs to be placed higher on a tower, any resulting terrain-caused tracking error may preferably be corrected or compensated for by utilizing an inclinometer and/or gyroscope sensor data for the GPS sensor at the tower. In this case, the GPS coordinates reported by the sensor may be adjusted based on the amount of tilt in the tower (due to terrain slopes) as measured by a co mounted inclinometer and/or gyroscope sensor. Alternatively, if the GPS sensor is mounted closer to the pipe on the tower, then there is no need to compensate for terrain-induced tilt.

Claim 1:
A method (<NUM>, <NUM>) for aligning spans (<NUM>, <NUM>), wherein the method is for a system (<NUM>, <NUM>) comprises a plurality of connected spans (<NUM>, <NUM>) and a plurality of drive towers (<NUM>, <NUM>, <NUM>, <NUM>) for moving the connected span around a center pivot having a pivot controller (<NUM>); wherein each drive tower is comprised of a power line (<NUM>, <NUM>) carrier node; further wherein the drive towers include intermediate drive towers and a last drive tower, further wherein the system comprises a fixed reference station (<NUM>, <NUM>) storing reference location data; the method characterised in using real-time kinetics,RTK, data communicated through a power line carrier system and wherein the method comprises: receiving a first set of GPS location data (320d: <NUM>, <NUM>); comparing the first set of GPS location data with the reference location data stored in the fixed reference station; calculating RTK error correction data; creating an RTK error correction data signal (<NUM>, <NUM>); modulating the RTK error correction data signal for transmission on a power line carrier; wherein the power-line carrier is comprised of a plurality of electrically conductive elements which are configured to connect and deliver signals to and from a power-line BUS (<NUM>, <NUM>); transmitting the RTK error correction data signal (<NUM>, <NUM>) through the power line BUS onto the power line to the power line carrier node of each drive tower; de-modulating the RTK error correction data signal; calculating the location of the last drive tower using the RTK error correction data; calculating (<NUM>) a center line between the pivot and the last drive unit; calculating the relative distances between each intermediate drive tower and the calculated (<NUM>) center line; wherein the distance calculation is made using a linear regression algorithm; and controlling the speed of each intermediate drive tower to reduce distance between their current locations and the calculated center line.