Implement guidance
Efficient towed implement guidance to a desired path is achieved by guiding a towing vehicle toward a path on the opposite side of a desired path, then guiding the vehicle back to the desired path. Efficient forward implement guidance to a desired path is achieved by guiding a pushing vehicle along a tractrix. A vehicle leaves a straight line along a tractrix to keep a rear implement on the line as long as possible.
1. A method for guiding a forward implement on a desired path comprising:
a path-planning autopilot first guiding a vehicle, to which the forward implement is attached, toward the desired path at an approach angle to the desired path less than or equal to a pre-defined maximum angle; and,
once the implement reaches the desired path, the autopilot then guiding a vehicle control point along a tractrix parameterized by a distance, F, wherein the distance F is the distance of the implement ahead of the vehicle control point.
2. The method of claim 1 further comprising:
the path-planning autopilot planning a vehicle path from an initial vehicle configuration to a point where the implement is on the desired path and the vehicle heading does not exceed a maximum angle away from the desired path.
3. The method of claim 2 where curvature of the planned vehicle path at the point is determined by the maximum angle and the tractrix.
4. The method of claim 1 wherein the vehicle has a wheelbase, B, and F is greater than B.
5. The method of claim 1 wherein the vehicle has a wheelbase, B, and F equals B.
6. The method of claim 1 wherein the vehicle has a wheelbase, B and F is less than B.
7. The method of claim 1 further comprising: once the vehicle is established on the desired path, the autopilot then resuming normal vehicle guidance along the desired path.
8. The method of claim 1 , the autopilot offering direct control over maximum permitted vehicle steering angle.
9. The method of claim 1 , the autopilot offering direct control over maximum permitted vehicle steering angle rate.
10. A vehicle autopilot comprising:
a microprocessor and memory;
a GNSS receiver that provides vehicle position, velocity and time estimates to the microprocessor;
a feedback controller and a feed-forward controller that generate vehicle curvature commands to guide the vehicle; and,
a vehicle steering actuator; wherein,
the autopilot guides a vehicle control point along a tractrix parameterized by a characteristic of an implement attached to the vehicle, the implement being a forward implement and the tractrix parameterized by a distance, F, wherein the distance F is the distance of the implement ahead of the vehicle control point.
11. The autopilot of claim 10 wherein the autopilot is a path planning autopilot.
12. The autopilot of claim 10 wherein the vehicle has a wheelbase, B, and F is greater than B.
13. The autopilot of claim 10 wherein the vehicle has a wheelbase, B, and F equals B.
14. The autopilot of claim 10 wherein the vehicle has a wheelbase, B, and F is less than B.
15. The autopilot of claim 10 , the autopilot offering direct control over maximum permitted vehicle steering angle.
16. The autopilot of claim 10 , the autopilot offering direct control over maximum permitted vehicle steering angle rate.
17. The autopilot of claim 10 , the GNSS receiver using differential corrections provided by the Wide Area Augmentation System.
18. The autopilot of claim 10 , the GNSS receiver using real-time kinematic positioning techniques.