AU767958B2 - A corner irrigation system including a GPS guidance system - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Valmont Industries Inc.

ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: A corner irrigation system including a GPS guidance system The following statement is a full description of this invention, including the best method of performing it known to me/us:p.

'r Background of the Invention 1. Field of the Invention This invention relates to a center pivot irrigation system having the ability to irrigate the comers of the field being irrigated. More particularly, this invention relates to an improved means for guiding the movement of the corner span with respect to the center pivot portion of the system which includes a GPS guidance 10 system.

2. Description of the Related Art ob oo Conventional center pivot irrigation systems comprise an elongated main boom pivotally connected at its inner end to a center pivot structure and extending outwardly therefrom. The main boom of the conventional center pivot irrigation S. 15 system is comprised of a plurality of pipes connected together in an end-to-end fashion which are supported upon a plurality of drive towers. In most conventional center pivot irrigation systems, the outermost drive tower is the master tower with *the other drive towers being selectively driven in response to angular displacement of the boom section adjacent thereto.

20 In the early 1970s, comer systems for center pivot irrigation systems were o developed to enable the comers of a square field to be irrigated. See, for example, U.S. Patent Nos. 3,797,517; 3,802,726; and 3,902,668. Comer systems usually consist of an extension boom or arm, sometimes referred to as a comer span, which is pivotally connected to the outer end of the main boom and which is supported on at least one steerable drive tower. A guidance system is provided for guiding or steering the extension tower, and extension boom, out into the comers of the field as the main arm travels around the field. Perhaps the most popular method of guiding the extension tower is the buried wire system described in U.S. Patent No. 3,902,668. However, many different types of systems for P:\OPER\DH2295349 spa.do-18/09/03 driving and steering the wheels of the extension tower have been previously provided. See, for example, U.S. Patent Nos. 4,508,269 and 4,674,681.

Although the prior art systems do perform generally satisfactorily to drive and steer the extension booms, it is believed that the instant invention, utilizing a GPS guidance system, is more reliable and is more accurate than the prior art systems.

Summary of the Invention In accordance with the invention, there is provided a self-propelled irrigation machine having an elongated main boom pivoted at one end to a center pivot apparatus and mounted on a plurality of self-propelled, non-steerable drive towers, an extension boom pivotally secured to the other end of the main boom for irrigating corner areas of the field, a steerable drive tower supporting said extension boom including a pair of steerable drive wheels, comprising: means for steering said steerable drive wheels for guiding said steerable drive tower along a preselected path thereby causing the pivotal extension of said extension boom into the corner areas of the field as said main boom approaches the same and pivotal retraction of said extension boom out of the corner areas of the field as said main boom departs the same; control means for controlling the operation of said means for steering said steerable drive wheels; said control means including a GPS receiver means and a computer means for receiving and processing GPS information as to the location of said main boom and for determining the optimal steer angle for said steerable drive wheels for the current position of said main boom and for positioning said steerable drive wheels in the optimal steer angle.

Brief Description of the Drawings Figure 1 is a perspective view illustrating the corner irrigation system of this invention; and Figure 2 is a block diagram of the GPS instrumented corner guidance system of this invention.

Description of the Preferred Embodiment 30 The self-propelled irrigation system or corner irrigation system of this invention is illustrated in Figure 1 and is generally designated by the reference numeral 10. System 10 includes a conventional center pivot structure 12 having a .$o P:\OPER\DH2295349 spal.doc-17/09/03 main boom 14 pivotally secured thereto and extending outwardly therefrom and which is supported by a plurality of non-steerable drive towers 16, 16A, and 16B which is the last regular drive unit (LRDU). Although only three drive towers 16 are illustrated, the main boom 14 could utilize any number of drive towers. The numeral 18 refers to an extension boom or corner span which is pivotally connected at its inner end to LRDU 16B and which is supported upon a steerable drive tower or unit 20 (SDU) having a pair or steerable wheels 22 and 24 which are steered by an electric motor in conventional fashion except for the control or guidance means. Normally, the current method for controlling the extension and retraction of the corner span or extension boom 18 relies on sensing the electric field generated by a cable buried along the desired path of the SDU 20, on a corner arm equipped center pivot irrigation system such as disclosed in U.S.

o* oooo Patent No. 3,902,668. With this approach, an oscillator at the pivot 12 is used to create a low frequency signal in a buried cable with an antenna and signal processing electronics being mounted on the SDU to detect the electric field radiated from the buried cable and determine the appropriate steer angle of the SDU wheels 22 and 24 which will keep the SDU 20 oyer the top of the buried cable. Cable and installation expenses as well as servicing cable breaks are disadvantages of this method. It is to this conventional comer arm equipped center pivot irrigation system that the GPS guidance system of this invention is utilized.

10 In this invention, a guidance and control system providing accurate navigation of a center pivot irrigation comer arm has been developed using GPS receivers as position sensors. The system is comprised of two GPS units (receiver and antenna), two microprocessor based "smart boxes", a communications link (typically hard-wired RS-485 differential bus running from pivot 12 to SDU 20), and an angle sensor to monitor the angle of the comer arm steerable wheels. More particularly, the numeral 26 refers to a GPS receiver located at the pivot structure 12 which is preferably a Canadian Marconi RTSTAR Reference RCVR while the GPS receiver 28 at the SDU 20 is preferably a Canadian Marconi RTSTAR Mobile RCVR. The computer 30 at the pivot 12 is 20 operatively interconnected to the GPS receiver 26 in conventional fashion.

.:eoei S Preferably, the GPS receiver 28 is interconnected to the smart tower box 38 which is connected to the steering angle sensor 36 of conventional design. Smart tower box 38 is optional and may be located at the LRDU 16B.

The stationary "base" GPS receiver 26 is programmed with approximate reference coordinates. Precise coordinates from a geodetic survey are not required, since all required position information is relative between the two GPS receivers 26 and 28 not absolute with the center of the earth as a reference. As the base GPS receiver 26 computes a new coordinate each second (using information provided by an orbiting GPS satellite), it compares the computed coordinates with the reference coordinates to determine the error in the immediate code and carrier phase GPS signals. This error is then transmitted to the smart box 32 at the corner arm steerable drive unit 20. The "smart box" 32 immediately sends this data to a communications port such as the auxiliary communications port of the "roving" GPS receiver 28. With this correction data, the roving GPS receiver 28 is able to determine the position of its antenna relative to the antenna of the base receiver 26 with the accuracy of 10-20 cm. Using this position information, the "roving" computer 32 translates the global coordinates to local coordinates and determines the relative distance and angle of the SDU 20 to the pivot 12. With this distance and angle information, the smart box 32 at the SDU 10 20 determines the appropriate steer angle of the steerable wheels 22 and 24 and controls them accordingly. Determining the appropriate steer angle involves a oO software look-up table containing ideal pivot-SDU distances based on pivot-SDU angles from 0.0 to 359.9. The difference between the computed pivot-SDU distance and the ideal pivot-SDU distance (corresponding to the current pivot- SDU angle) is used as an error term in a PI (proportional-integral) control loop used to steer the wheels 22 and 24.

The software look-up table is specific to each field and is determined during a single revolution of the system. During this revolution, the smart box 32 and the GPS unit 28 that are located at the SDU 20 in normal operation will be placed at 20 the LRDU 16B to determine the pivot-LRDU distance at each LRDU angle Slocation. This is important because field topology greatly affects the relative horizontal pivot-LRDU distance which is used in determining an ideal SDU path.

At the completion of the revolution, the "roving" smart box 32 or a personal computer will use the acquired position data to generate the software look-up table. This table is generated using the following information: pivot-LRDU distance at each .1 degree position; comer arm length dry no water in system); comer arm length wet; maximum north, south, east, west field dimensions; and maximum and minimum allowable comer angle. Further, position data for any obstacles in the field barn or house) would also need to be P:\OPER\DH2295349 spA. I.dc-17/09/03 provided. In some situations, it may be important to perform an initial revolution in the forward and reverse directions to adequately develop a software look-up table.

Thus, as the main boom moves through the field, the guidance system of this invention will adjust the steering angle of the SDU 20 to properly position the extension boom with respect to the main boom for every position of the main boom with respect to the field.

Thus it can be seen that the guidance system of this invention therefore achieves all of its stated objectives.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

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Claims (7)

1. A self-propelled irrigation machine having an elongated main boom pivoted at one end to a center pivot apparatus and mounted on a plurality of self- propelled, non-steerable drive towers, an extension boom pivotally secured to the other end of the main boom for irrigating corner areas of the field, a steerable drive tower supporting said extension boom including a pair of steerable drive wheels, comprising: means for steering said steerable drive wheels for guiding said steerable drive tower along a preselected path thereby causing the pivotal extension of said extension boom into the corner areas of the field as said main boom approaches the same and pivotal retraction of said extension boom out of the corner areas of the field as said main boom departs the same; control means for controlling the operation of said means for steering said steerable drive wheels; said control means including a GPS receiver means and a computer means for receiving and processing GPS information as to the location of said main boom and for determining the optimal steer angle for said steerable drive wheels for the current position of said main boom and for positioning said steerable drive wheels in the optimal steer angle. 20

2. The self-propelled irrigation machine of claim 1 wherein said GPS receiver means comprises a first GPS receiver located at the center pivot and a second GPS receiver located on said steerable drive tower.

3. The self-propelled irrigation machine of claim 2 wherein said computer means includes a software based look-up table containing the ideal steerable drive tower path.

4. The self-propelled irrigation machine of claim 3 wherein said computer means 0: is located at said center pivot.

5. The self-propelled irrigation machine of claim 3 wherein said computer means is located at said steerable drive tower. 00o @:.00 P:\OPER\DH\2295349 spa I.doc-17/09/03

6. The self-propelled irrigation machine of claim 3 wherein position information obtained from said GPS receiver means, which are located at said center pivot and said steerable drive tower, as said main boom pivots, is used by said computer means to determine an accurate steerable drive tower position relative to the pivot position of the main boom.

7. An irrigation machine substantially as hereinbefore describe with reference to the drawings and/or Examples. DATED this 17th day of September, 2003 VALMONT INDUSTRIES INC. By DAVIES COLLISON CAVE Patent Attorneys for the applicant 0