GNSS navigation for a mechanized irrigation corner system

A GNSS based steering control system for a mechanized irrigation corner arm utilizing waypoint navigation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to mechanized center-pivot irrigation systems, having a corner system attached thereto to provide water to the corners of a field. More specifically, this invention relates to a system for path following using global navigation satellite system (GNSS) control for waypoint navigation of the corner system.

2. Description of the Related Art

Mechanized center-pivot irrigation systems have been used to apply water to large sections of land in an efficient manner to greatly improve crop production. To overcome the limitation of irrigating only a circular pattern, a corner system can be added to the end of a center pivot to irrigate additional areas of a square, rectangular or irregular-shaped field.

Corner systems were first introduced in the 1970s and utilized a guidance system for guiding or steering the corner system along a path. The most popular method for guiding a corner system has been through the use of a buried wire which emits an electromagnetic field that can be detected by sensors on the corner system. See U.S. Pat. No. 3,902,668, Daugherty, et al. Drawbacks to this system include obstacles to burying the typical 9500 feet of wire for instance where rocks are present, difficulty in repairing damage to the buried cable and difficulty in changing the path to be followed.

Global navigation satellite systems (GNSS) have recently been used for corner system guidance, utilizing GPS satellites. U.S. Pat. No. 6,095,439, Segal, et al. disclosed a method for determining optimum steer angle based on the error between a computed pivot-SDU distance and an ideal pivot-SDU distance. U.S. Pat. No. 6,290,151 B1, Barker, et al. also disclosed a method of steering the corner based on the error between the actual rover distance from the pivot point versus an intended distance from the pivot point and additionally a method of projecting a virtual position at a selected length of travel to determine steering. U.S. Pat. No. 6,923,390 B1 Barker, et al. disclosed a method of using two antennas that rotate with steering movement, with the antenna leading in the direction of travel used to determine the distance from a point midway between two selected points on the path of travel. U.S. Pat. No. 8,401,704 B2 Pollock, et al. disclosed a method of using two GNSS antennas to compute a vector orientation to control the corner system, with one antenna located at the hinged connection of the pivot to the corner system (last regular drive unit) and one antenna located on the corner system boom.

In US Patent Application Publication No. 2011/0153161 A1 published Jun. 23, 2011, applicants John Grabow, et al describe a corner guidance control system using two antennas attached by a rail system at a right angle to a corner system wheel, with the two antennas used to calculate current position of the wheel for steering purposes and to calculate a tilt angle from the altitude of the two antennas.

In US Patent Publication No. 2012/0010782 A1 published Jan. 12, 2012) applicant John Grabow describes a corner guidance control system using one antenna that is located along a vertical axis through a center of a wheel of the corner unit to acquire current position of the center of the wheel and a wheel angle sensor used to determine the current heading of the wheel. A point is calculated along the corner travel path that is a radial distance from the current position and a future heading is determined to steer the wheel versus the current heading.

The present invention provides an improved system for corner path following that employs global navigation satellite system (GLASS) sensors which utilizes waypoint navigation.

SUMMARY OF THE INVENTION

This invention relates to a mechanized corner irrigation system, which is part of a center pivot irrigation system, for irrigating a field having navigation waypoints which correspond to the correct position of the steerable drive unit of the corner irrigation system as the center pivot irrigation system and the corner irrigation system move around the field. The center pivot irrigation system includes a center pivot structure, a main arm extending outwardly from the center pivot structure with the main arm being supported upon and driven in either a forwardly or rearwardly direction around the field by a plurality of non-steerable drive units. The corner irrigation system includes an elongated corner arm pivotally secured to the outer end of the main arm of the center pivot irrigation system and which is supported upon and driven by a steerable drive unit.

The steerable drive unit includes a horizontally disposed main beam, having first and second ends, which are positioned below the corner arm and which is disposed transversely with respect to the corner arm. A first drive wheel support is positioned at the first end of the main beam and is rotatable with respect thereto about a vertical axis. A second drive wheel support is positioned at the second end of the main beam and is rotatable with respect thereto about a vertical axis. The first and second drive wheels are mounted on the first and second drive wheel supports respectively. The steerable drive unit also includes first and second horizontally disposed crank arms which have inner and outer ends. The inner end of the first crank arm is affixed to the first drive wheel support and extends therefrom. The inner end of the second crank arm is affixed to the second drive wheel support and extends therefrom. An elongated connecting rod has one end thereof pivotally secured to the outer end of the first crank arm and has its other end pivotally secured to the outer end of the second crank arm. The steerable drive unit also includes a steering actuator which is mounted thereon and which is operatively connected to one of the first and second crank arms for pivotally moving the first and second drive wheel supports and the drive wheels thereon in a right direction or a left direction to steer the steerable drive unit as the corner irrigation system is moved around the field.

A rover navigation box is positioned on the steerable drive unit and includes a GNSS receiver mounted on a printed circuit board. A rover GNSS antenna is mounted on the steerable drive unit which is in communication with the GNSS receiver in the rover navigation box. The navigation waypoints are loaded and stored in the printed circuit board of the rover navigation box. The rover navigation box is operatively connected to the steering actuator to control the operation of the steering actuator.

A base navigation box is positioned on the center pivot irrigation system at the center pivot structure. The base navigation box includes a GNSS receiver mounted on a printed circuit board. A base GNSS antenna is mounted on the center pivot irrigation system at the center pivot structure with the base GNSS antenna being in communication with the GNSS receiver in the base navigation box. The base navigation box is configured to compute its position using RTK to send corrections to the rover navigation box with the rover navigation box continuously computing its corrected position as the steerable drive unit moves around the field with the corrected position of the steerable drive unit being compared to the two closest navigation waypoints to determine the steering direction of the steering actuator and the amount of steering time to ensure that the steerable drive unit stays on its intended path.

It is therefore a principal object of the invention to provide a GNSS path following system for mechanized irrigation corner systems utilizing waypoint navigation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The numeral10refers to a mechanized irrigation system which is commonly referred to as a corner pivot irrigation system. System10includes a center pivot structure12having a main arm14extending outwardly from the pivot structure12. The main arm14comprises a water conduit or pipeline18supported upon a plurality of non-steerable drive units or towers20. Corner arm22is pivotally connected to the last regular drive unit (LRDU)20A at24in conventional fashion and comprises a water conduit or pipe26which is supported upon a steerable drive unit (SDU) or tower28.

SDU28includes a main beam30having opposite ends32and34. Beam30may be disposed at a right angle to the longitudinal axis of pipe26or at some other angle with respect thereto as is common in most corner pivot irrigation machines or systems. Beam30is secured to pipe26by a truss36. A pair of tubular supports38and40are secured to ends32and34of beam30respectively and extend downwardly therefrom. The lower ends of supports38and40receive vertically disposed tubes42and44respectively of drive wheel supports46and48respectively. Drive wheels50and52are rotatably mounted on the lower ends of drive wheel supports46and48respectively. Drive wheels50and52may be driven by hydraulic motors or electric motors in conventional fashion.

One end of a crank arm54is fixed to the upper end of tube42and extends horizontally therefrom. One end of a crank arm56is fixed to the upper end of tube44and extends horizontally therefrom. An elongated tie rod or link58has one end pivotally connected to the outer end of crank arm54at60and has its other end pivotally connected to the outer end of crank arm56at62.

In the embodiment shown in the drawings, a hydraulic steering cylinder64has its base end pivotally operatively connected to beam30at65and has its rod end pivotally connected to crank arm56at66. The hydraulic cylinder64is employed when the drive wheels of the system are driven hydrostatically such as those systems manufactured by the assignee of this invention. If the drive wheels of this system are electrically driven, an electric motor and gearbox structure will replace the hydraulic steering cylinder64. In this system, extension of the cylinder rod of hydraulic cylinder64will cause tubes42and44and the drive wheels50and52to be rotated in a first (right) direction (FIG. 7). The retracting of the cylinder rod of hydraulic cylinder64will cause tubes42and44and the drive wheels50and52to be rotated in a second (left) direction opposite to the first (right) direction (FIG. 6).

The numeral67refers to a hydraulic steering solenoid valve which is fluidly connected to a source of hydraulic fluid under pressure. Valve67includes two coils, with one energized to “steer right” and the other energized to “steer left.” To steer right, the steering cylinder64extends. To steer left, the steering cylinder64retracts. The tie rod58allows wheels50and52to steer at the same time. Valve67is fluidly connected to hydraulic steering cylinder64. The numeral68refers to a GNSS antenna which extends upwardly from pipe26above main beam30, as seen in the drawings. The numeral70refers to a rover navigation box mounted on pipe26. The numeral72refers to a GNSS antenna which is mounted on the center pivot structure12. A base navigation box74is mounted on the inner end of main arm14.

The GNSS antenna68is connected to a GNSS receiver located inside the rover navigation box70(FIG. 13). The GNSS receiver is mounted on a printed circuit board (PCB) inside the rover navigation box70(FIG. 13) and the PCB has the means to store the navigation waypoints76as will be described hereinafter. The GNSS antennas68and72and the receivers associated therewith have the capability of receiving GPS and Glonass satellite signals and can be expanded to other constellations as they become available.

FIG. 8illustrates the method of generating the navigation waypoints76ofFIG. 9using a CAD program to draw a corner system array78. The corner system array78represents the location of the corner system22and the SDU28at numerous different points in the field80. The SDU locations are then used to generate specific latitude and longitudinal waypoints76as seen inFIG. 9that will be stored as a file and transferred to the rover navigation box70. The method of generating the navigation waypoints could also be through a simulation program or mapping program.

FIG. 9illustrates the navigation waypoints76generated from the corner system array78to be used for path following by the navigation system. The series of waypoints is exported to a file that is transferred to the PCB in the rover navigation box70as stated above.

FIGS. 10 and 11illustrate a generalized top view of the SDU28and the nearby navigation waypoints (r2, r1, f1, f2) as contained in a file loaded onto the PCB in the rover navigation box70. Each waypoint has a specific x, y coordinate or latitude, longitude associated with it. The steerable drive unit (SDU)28also has a certain x, y (latitude, longitude) associated with it, as determined by the GNSS system. As shown in the example ofFIG. 11, if the system is moving in Reverse, then the SDU28will be navigating from waypoint “f1” to waypoint “r1”. If system moving in Forward, then the SDU28will be navigating from way point “r1” to waypoint “f1.”

To summarize somewhat, the SDU position (latitude, longitude) is determined to centimeter accuracy through an RTK technique of the GNSS system. With RTK, the base navigation box74computes its position and sends corrections to the rover navigation box70via a communication cable or wireless radio. The rover navigation box70then continuously computes its corrected position as the SDU28moves. This corrected SDU position is then compared to the two closest navigation waypoints, one on either side of the SDU28, and through a steering formula based on two parameters of cross-track error and heading error, the steering direction and the amount of steering time is determined. The steering solenoid valve67directs oil to the hydraulic steering cylinder64to steer the SDU28and is energized to steer in the correct direction and for the amount of steering time to ensure the SDU28stays on the intended path. Steering systems could consist of an electric motor and gear box arrangement rather than the hydraulic steering cylinder64. After steering, the corner system22is allowed to move for a specified period of time and then the formula is computed again to determine steering. This loop occurs continuously as the corner system navigates through the waypoints around the field.

FIG. 12illustrates an example of two parameters used in the steering formula. Cross-track error is calculated as the distance the SDU28is from the intended path. Heading error is calculated by finding the difference between the intended heading angle and the actual heading angle in degrees.