feat: loop turn

Add headland turn maneuver to make corners with a 270 turn.
This is good for rigs that can't reverse but there is plenty of
room on the field to make a 270 loop. Examples are seed drills
with a seed cart. The first headland should be round, the second
and the rest can have a corner and there, this 270 will be used.

Such rigs are currently auto-detected but we can also make it
an option.

#737

Author: Peter Vaiko

scripts/ai/turns/AITurn.lua

@@ -744,14 +744,16 @@ function CourseTurn:generateCalculatedTurn()
     if self.turnContext:isHeadlandCorner() then
         self:debug('This is a headland turn')
         if self.hasChainedAttachments then
+            -- do a 270° turn forward only
             turnManeuver = LoopTurnManeuver(self.vehicle, self.turnContext, self.vehicle:getAIDirectionNode(),
                     self.turningRadius, self.workWidth, self.steeringLength)
+            self.enableTightTurnOffset = true
         else
             turnManeuver = HeadlandCornerTurnManeuver(self.vehicle, self.turnContext, self.vehicle:getAIDirectionNode(),
                 self.turningRadius, self.workWidth, self.reversingImplement, self.steeringLength)
+            -- adjust turn course for tight turns only for headland corners by default
+            self.forceTightTurnOffset = self.steeringLength > 0
         end
-        -- adjust turn course for tight turns only for headland corners by default
-        self.forceTightTurnOffset = self.steeringLength > 0
     else
         local distanceToFieldEdge = self.turnContext:getDistanceToFieldEdge(self.vehicle:getAIDirectionNode())
         local turnOnField = self.driveStrategy:isTurnOnFieldActive()

scripts/ai/turns/TurnManeuver.lua

@@ -459,6 +459,9 @@ function DubinsTurnManeuver:findAnalyticPath(startNode, startXOffset, startZOffs
     return Course.createFromAnalyticPath(self.vehicle, path, true)
 end
 
+--- Headland turn maneuver to make corners with a 270 turn. This is good for rigs that can't reverse but there is
+--- plenty of room on the field to make a 270 loop. Examples are seed drills with a seed cart. The first headland
+--- should be round, the second and the rest can have a corner and there, this 270 will be used.
 ---@class LoopTurnManeuver : TurnManeuver
 LoopTurnManeuver = CpObject(DubinsTurnManeuver)
 function LoopTurnManeuver:init(vehicle, turnContext, vehicleDirectionNode, turningRadius,
@@ -468,14 +471,18 @@ function LoopTurnManeuver:init(vehicle, turnContext, vehicleDirectionNode, turni
             workWidth, steeringLength)
     local turnEndNode, endZOffset = self.turnContext:getTurnEndNodeAndOffsets(steeringLength)
     self:debug('r=%.1f, w=%.1f, steeringLength=%.1f, endZOffset=%.1f', turningRadius, workWidth, steeringLength, endZOffset)
+    -- pull forward a bit to have the implement reach at least the middle of the outgoing edge, so the 270 is
+    -- easier to turn into the target direction. May need to increase it depending on user feedback.
     local pullForward = 0.5 * workWidth
     self.course = Course.createFromNode(self.vehicle, vehicleDirectionNode,
             0, 0, pullForward, 1, false)
     local path = PathfinderUtil.findAnalyticPath(PathfinderUtil.dubinsSolver,
             vehicleDirectionNode, 0, pullForward + 0.5, turnEndNode, 0, -steeringLength, turningRadius)
     self.course:append(Course.createFromAnalyticPath(self.vehicle, path, true))
+    TurnManeuver.setLowerImplements(self.course, steeringLength, true)
+    self:applyTightTurnOffsetToAnalyticPath(self.course)
     local endingTurnLength = self.turnContext:appendEndingTurnCourse(self.course, steeringLength)
-    self:applyTightTurnOffset(endingTurnLength)
+    TurnManeuver.setLowerImplements(self.course, endingTurnLength, true)
 end
 
 -- This is an experiment to create turns with towed implements that better align with the next row.