Articulation covering complete range of steering angles in automatic articulation feature

• US 9,428,884 B2
• Filed: 03/17/2014
• Issued: 08/30/2016
• Est. Priority Date: 03/17/2014
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Sharma, Amit, Budde, Steven C., Maas, Curtis, Moul, Matt I.
• Primary Examiner(s): Jabr, Fadey
• Assistant Examiner(s): Jos, Basil T
• Application Number:
  US14/216,368
• Publication Number:
  US 20150259882A1
• Time in Patent Office: 897 Days
• US Class Current: 1/1
• CPC Class Codes: B62D 12/00 Steering specially adapted for vehicles operating in tandem or having pivotally connected frames steering endless tracks or the like B62D11/00; steering specially adapted for trailers B62D13/00
• CPC Class Codes: B62D 9/00 Steering deflectable wheels not otherwise provided for steering positon indicators B62D15/02
• CPC Class Codes: E02F 3/7659 with the vertical centre-line of the scraper blade disposed laterally relative to the central axis of the chassis
• CPC Class Codes: E02F 9/0841 Articulated frame, i.e. having at least one pivot point between two travelling gear units tractor-trailer combinations B62D53/00
• CPC Class Codes: E02F 9/2087 Control of vehicle steering for steering with hydraulic or pneumatic drives E02F9/225
• CPC Class Codes: E02F 9/225 Control of steering, e.g. for hydraulic motors driving the vehicle tracks steering in general B62D
• CPC Class Codes: G05B 13/02 electric

Abstract

An controller uses one of several transfer curves to map steering angle of an articulated machine to articulation angle. Because an articulated machine may have a range of steering angles that is much greater than the range of articulation angles, the controller uses one of several techniques to map the full range of steering angles to the full range of articulation angles. One technique involves multiple non-zero slope regions, another technique uses a less than one-to-one linear transfer function of steering angle to articulation angle.

Claims

1. A method of managing articulation in a motor grader having front wheels that are steerable, the front wheels attached to a front frame, the front frame and a rear frame pivotally connected at an articulation joint, the method comprising:

determining, at a controller, a steering angle of the front wheels; and

adjusting, via the controller, an articulation angle at the articulation joint at a first ratio of more than one degree of the steering angle to one degree of articulation angle for steering angles in a first range, and at a second ratio less than the first ratio for steering angles in a second range.

2. The method of claim 1, wherein the second ratio is about 1 degree of steering angle to 1 degree of articulation angle.

3. The method of claim 1, wherein the first range is defined as the steering angle of the front wheels being greater than or equal to a threshold percentage of a maximum steering angle and the second range defined as the steering angle of the front wheels being less than the threshold percentage of the maximum steering angle of the front wheels.

4. The method of claim 3, wherein the maximum steering angle of the front wheels is in a range of 45-55 degrees.

5. The method of claim 3, wherein the threshold percentage is in a range between 45% and 55% of the maximum steering angle.

6. The method of claim 3, wherein the threshold percentage is in a range between 10% and 30% of the maximum steering angle.

7. A method of managing articulation in a motor grader, the method comprising:

receiving, via a steering angle sensor, a steering angle of front wheels of the motor grader;

setting, via a controller, an articulation angle between the front frame and the rear frame corresponding to a first ratio that is greater than 1;

1 ratio steering angle to articulation angle when the steering angle is in a first range; and

setting, via the controller, the articulation angle corresponding to a second ratio that is less than the first ratio and greater than zero when the steering angle is in a second range.

8. The method of claim 7, wherein the transfer function is a non-linear transfer function.

9. The method of claim 7, wherein the first ratio is 2.0 and the second ratio is 1.0.

10. A system for adjusting an articulation angle in a motor grader, the system comprising:

a front frame and a rear frame pivotally connected at an articulation joint;

front wheels attached to the front frame, the front wheels steerable over a steering angle range;

a steering angle sensor that reports a steering angle of the front wheels;

an articulation actuator that adjusts the articulation angle between the front frame and the rear frame over an articulation angle range, the steering angle range greater than the articulation angle range;

a controller coupled to the steering sensor and the articulation actuator, the controller using a transfer function to determine mapping of the steering angle range to the articulation angle range, the controller defining a first sub-range of the steering angle range and a second sub-range of the steering angle range, the first sub-range of the steering angle range and the second sub-range of the steering angle range containing no common steering angle values;

wherein a first portion of the transfer function with a first non-zero slope maps the first sub-range of the steering angle range to a first sub-range of the articulation angle range, and

wherein a second portion of the transfer function with a second non-zero slope maps a second sub-range of the steering angle range to a second sub-range of the articulation angle with a second non-zero slope, the first and second non-zero slopes having different slope values.

11. The system of claim 10, wherein the first non-zero slope is in a range from 0.8 to 1.2.

12. The system of claim 10, wherein the first sub-range of the steering angle range is zero degrees to about 25 degrees and the second sub-range of the steering angle range is about 25 degrees to about 50 degrees.

13. The system of claim 10, wherein the first sub-range of the steering angle range is zero degrees to about 12 degrees.

14. The system of claim 13, wherein the second sub-range of the steering angle range is from about 12 degrees to about 50 degrees.

15. A method of managing a relationship between a steering angle of front steerable wheels of an articulated machine and an articulation angle between a front frame and a rear frame in the articulated machine, the method comprising:

receiving an operator-initiated signal indicating a desired steering path; and

adjusting a relationship between the steering angle of the steerable front wheels and the articulation angle according to a first ratio of more than one degree of steering angle to one degree of articulation angle for steering angles in a first range, and a second ratio less than the first ratio for steering angles in a second range.

16. The method of claim 15,

wherein receiving the operator-initiated signal comprises receiving an operator-initiated signal to change the articulation angle of the articulation machine, and

wherein adjusting the relationship between the steering angle and the articulation angle comprises adjusting the steering angle responsive to a change in the articulation angle according to the signal to change the articulation angle.

17. The method of claim 16, wherein receiving an operator-initiated signal to change articulation angle further comprises receiving the operator-initiated signal that changes steering angle relative to articulation angle only while operating the articulated machine in reverse.

18. The method of claim 15, wherein receiving the operator-initiated signal indicating a desired steering path comprises receiving an operator initiated signal to change the steering angle of the steerable front wheels while operating in a forward direction.