AB Curves allow an operator to drive a curved line with two end points (beginning and end). Passes that are parallel to the track in either direction are generated based on the original driven track. Each pass is generated from the original driven pass to ensure that steering errors are not propagated through entire field. Passes are not identical copies of the original pass. Curvature of each pass changes to maintain pass-to-pass error.
Once an AB Curve (Track 0) is recorded, five tracks are generated on each side of Track 0.
NOTE: When using AutoTrac Turn Automation, AB Curves generates ten tracks on each side of the current track.
When the machine drives past the last generated track from Track 0, ten additional tracks are generated in that direction. The system continues to generate additional passes when the machine drives past the last pass displayed on the screen. When the system is generating additional passes, AutoTrac does not work on any paths.
NOTE: Skip pass is available in AB Curves mode. Skip pass is driving past or skipping over tracks next to the current track.
Lines are projected according to Generation Limits. Skip pass is not available in Adaptive Curve mode.
AB Curve Generation Limits - The initially recorded AB Curve must be at least 3 m (10 ft) in length to be a valid AB Curve for guidance. Machine must be within 400 m (0.25 mi) of the last generated track for the system to generate curve paths. If the machine is at the outer limit, it can take several minutes for a generated path to show up on the screen.
Multiple AB Curves - A field can contain multiple AB Curve paths. Each AB Curve for a field must be recorded and uniquely named.
Track Numbering and Direction - Track number and track direction away from Track 0 is indicated directly below the heading. The number indicates lines away from Track 0, followed by direction relative to the heading of Track 0.
Recorded Extensions - AB Curve paths are generated with a 91 m (300 ft) recorded extension attached to the end of the actual recorded path. This recorded extension allows the operator to line up the machine on the path before entering the field. The recorded extensions are useful where the recorded path is shorter than the field boundary.
NOTE: Ensure that the AB curve track is generated across the entire field. Gaps in the guidance track may cause issues with AutoTrac Turn Automation functionality.
Projected Extensions - If a second 91 m (300 ft) line extension is needed, it is projected before getting to the end of the Recorded Extension. Projected Extensions are not saved to the line.
Shift Track - When shift track is selected, the current track is adjusted and five passes on both sides of the track are regenerated. AB Curve can be used after initial tracks are generated. Additional tracks are generated while operating.
The display shifts AB Curves using different logic than other guidance methods. Instead of straight, lateral shifts, AB Curves uses radial shifts. Radial shifts support directional movement perpendicular to the tangent of the curve at each point along the track. Each point along the curve is shifted during regeneration. The shape and geometry of the curve change with the shift.
When an AB Curve is shifted, the new AB Curve is shifted radially at the point of the shift. The radial shift is propagated along the length of the line. The track spacing and heading of the new AB Curve are based on the original AB Curve.
NOTE: Smoothing of curves is applied to each new pass. Smoothing can cause small gaps in coverage. If necessary, smoothing of line segments can be turned off in the guidance settings.
When using AutoTrac Turn Automation, shifting the track regenerates all of the guidance tracks. Shift track is disabled within headlands.
NOTE: If the AB curve track is shifted close to an upcoming turn, the turn may not be generated.
Importing and Exporting AB Curve Shifts
If importing AB Curves with shifts from a GreenStar 3 2630 Display, the shifted lines import. If any dimensions or applications change, the AB Curves do not regenerate based on those changes. To account for those changes, the AB Curve must be recreated using the original AB Curve.
Radial shifts from a G5 Display or a Generation 4 Display are not compatible with GreenStar Displays.
AB Curves exported to GreenStar 2 Displays, GreenStar 3 Displays, or John Deere Operations Center retain their radial shifts when imported back to a G5 Display or a Generation 4 Display only if the AB Curve is not modified while on other display types.
NOTE: Sharp Curve and End of Path messages can appear when in AB Curve track.