Steering logic for self-propelled mower

• US 20070260370A1
• Filed: 05/08/2006
• Published: 11/08/2007
• Est. Priority Date: 05/08/2006
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Romig, Bernard
• Granted Patent: US 7,418,328 B2
• Time in Patent Office: Days
• US Class Current: 701/23
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: B62D 11/001 control systems B62D11/183 takes precedence
• CPC Class Codes: B62D 7/026 characterised by comprising more than one bogie, e.g. situated in more than one plane transversal to the longitudinal centre line of the vehicle
• CPC Class Codes: B62D 7/1509 with different steering modes, e.g. crab-steering, or steering specially adapted for reversing of the vehicle

Abstract

Steering logic for a self-propelled vehicle having a plurality of wheels includes the steps of receiving translational velocity and angular velocity commands, determining the resultant velocity and steer angle of each wheel, and determining the wheel offset correction for each wheel based on the scrub radius of each wheel and the angular velocity command.

Claims

1. Steering logic for a self-propelled vehicle having a plurality of wheels, each wheel having a steer axis and scrub radius, comprising the steps of:

inputting commands for a desired translation velocity and a desired angular velocity of the center of the vehicle;

for each wheel, calculating a rotational velocity as the vector cross product of the desired angular velocity and the steer axis for the wheel;

for each wheel, adding the rotational velocity and the translational velocity to obtain a resultant velocity and steer axis for the wheel;

for each wheel, calculating the wheel offset correction as the product of the scrub radius and the desired angular velocity of the vehicle; and

calculating and providing the actual speed and actual steer angle set points to each wheel.

2. The steering logic of claim 1 further comprising the step of obtaining a current heading for each wheel, determining if the input commands require each wheel to be steered more than 90 degrees from the wheel'"'"'s current heading, and if so, reversing the direction of rotation and setting the steering command at 180 degrees from the calculated actual steer angle.

3. The steering logic of claim 1 further comprising the step of applying a toe in correction to modify the actual steer angle set point for each wheel.

4. The steering logic of claim 1 wherein the step of inputting commands is done with an operator input device.

5. The steering logic of claim 1 wherein the step of inputting commands is done with a mission control computer.

6. The steering logic of claim 1 wherein the self-propelled vehicle is riderless.

7. The steering logic of claim 1 wherein the self-propelled vehicle has a rotatable coordinate system, and further comprising the step of transforming the desired translational velocity from the rotatable coordinate system.

8. Steering logic for a self-propelled vehicle having a plurality of wheels, comprising the steps of:

receiving translational velocity and angular velocity commands for the self-propelled vehicle;

determining the resultant velocity and steer angle of each wheel; and

determining the wheel offset correction for each wheel based on the scrub radius of each wheel and the angular velocity command.

9. The steering logic of claim 8 wherein the self-propelled vehicle is riderless.

10. The steering logic of claim 8 further comprising the step of reversing the direction of rotation of a wheel if the commands require the wheel to be steered more than 90 degrees.

11. The steering logic of claim 8 wherein the vehicle has a rotatable coordinate system and a platform coordinate system, and comprising the step of transforming the translational velocity command to the platform coordinate system.

12. The steering logic of claim 8 wherein the wheel offset correction is the product of the scrub radius and the angular velocity of the vehicle.

13. The steering logic of claim 8 further comprising the step of providing an actual speed and actual steer angle set point to a servo for each wheel.

14. Steering logic for a self-propelled vehicle having three steerable wheels, comprising the steps of:

obtaining the actual steer angle of each wheel;

determining a new velocity and steer angle of each wheel based on commands received relating to the desired movement of the vehicle;

for each wheel, calculating a wheel offset correction as a product of a scrub radius for each wheel and a desired angular velocity of the vehicle; and

providing a new actual speed and actual steer angle set point to a servo for each wheel.

15. The steering logic of claim 14 further comprising the step of reversing direction of rotation of a wheel if the commands received require the wheel to be steered more than 90 degrees from its actual steer angle.

16. The steering logic of claim 14 wherein the vehicle has a rotatable coordinate system, and further comprising the step of transforming the translational velocity command from the rotatable coordinate system.