Automatic control of passive, towed implements

• US 8,116,977 B2
• Filed: 08/25/2010
• Issued: 02/14/2012
• Est. Priority Date: 10/02/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Aral, Gurcan, Peake, John W, Stronger, Brad A
• Primary Examiner(s): Trammell, James
• Assistant Examiner(s): Do, Truc M
• Application Number:
  US12/868,626
• Publication Number:
  US 20100324772A1
• Time in Patent Office: 538 Days
• Field of Search: 701/50, 701/54, 701/214
• US Class Current: 701/214
• CPC Class Codes: A01B 69/004 automatic
• CPC Class Codes: G05D 1/0278 using satellite positioning signals, e.g. GPS

Abstract

An automatic control system for passive, towed implements is described. The system provides a strategy for optimal control of a towed implement using a nudge input to an autopilot-controlled tractor. Implement path-tracking error, as measured by a GNSS receiver, is consistently corrected to zero.

Claims

1. A method for guiding a passive implement along a desired path comprising:

providing a tractor guided by an autopilot having a nudge input;

introducing a test input to the tractor autopilot;

providing a GNSS receiver fixed to the passive implement;

towing the passive implement behind the tractor via a hitch;

using a model of the tractor-hitch-implement system to provide feedback to a control system that provides nudge inputs to the autopilot-controlled tractor and to the model;

wherein,

the model estimates the immediate passive implement offset from the path;

tractor, hitch and implement elements within the model are arranged such that nudge inputs from the control system are applied to the implement element directly;

the tractor element of the model includes information obtained from measurements of the motion of the tractor in response to the test input; and

,

the control system nudge inputs cause the difference between the actual implement path and the desired path to be minimized.

2. The method of claim 1 wherein the test input is a step offset and the information obtained from measurements of the motion of the tractor is the time, t_1/2, required for the tractor to achieve half the step offset.

3. The method of claim 1 wherein the test input is a step, a pulse, or a sinusoid and the information obtained from measurements of the motion of the tractor is a set of parameters that best fit the motion to a transfer function.

4. The method of claim 1 wherein the test input is a pseudorandom sequence and measurements of the motion of the tractor are cross-correlated with the pseudorandom sequence to determine a tractor response function.

5. The method of claim 1 wherein measurements of the motion of the tractor are obtained using a GNSS receiver fixed to the tractor.

6. The method of claim 1 wherein the hitch element of the model includes the distance from the hitch to the midpoint of the tractor'"'"'s rear axle.

7. The method of claim 1 wherein the implement element of the model includes the distance from the implement'"'"'s control point to the hitch.

8. The method of claim 1 wherein the GNSS receiver is a GPS receiver employing SBAS corrections.

9. The method of claim 8 wherein the SBAS corrections are obtained from the FAA WAAS.

10. The method of claim 1 wherein the GNSS receiver is a GPS receiver employing RTK positioning.