Method for developing an algorithm to efficiently control an autonomous excavating linkage

• US 6,691,010 B1
• Filed: 11/15/2000
• Issued: 02/10/2004
• Est. Priority Date: 11/15/2000
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Gay, John R.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Broadhead, Brian J.
• Application Number:
  US09/713,591
• Time in Patent Office: 1,182 Days
• Field of Search: 701/50, 701/27, 701/44, 374/14, 414/699, 172/2, 700/245, 700/246, 700/250, 700/251, 700/252, 700/253, 700/257, 700/261, 700/262
• US Class Current: 701/50
• CPC Class Codes: E02F 3/437 providing automatic sequences of movements, e.g. linear excavation, keeping dipper angle constant
• CPC Class Codes: E02F 9/2025 Particular purposes of control systems not otherwise provided for E02F3/16, E02F3/26, sub-groups of E02F3/43, E02F3/651, sub-groups of E02F3/84, E02F3/907, E02F5/145 take precedence
• CPC Class Codes: G05B 13/0275 using fuzzy logic only

Abstract

The present invention is a control system for controlling movement of a work implement from a dig location to a dump location. The work implement has at least four degrees of freedom defined by a swing joint angle θ_swing, a boom joint angle θ_boom, a stick joint angle θ_stick, and a bucket joint angle θ_bucket. In one embodiment, the control system comprises a central processing unit and a memory device. The control system further comprises an initialization module stored on the memory device and adapted to determine specified initial and final joint angles for an initial cycle of the work implement indicative of the specified dig and dump locations, respectively. The control system further comprises a hydraulic valve connected to the central processing unit and to the work implement. The control system further comprises a fuzzy control module stored on the memory device. The fuzzy control module comprises a fuzzy-logic swing valve control module, a fuzzy-logic boom valve control module and a fuzzy-logic stick valve control module each adapted to instruct the central processing unit in a finite state manner to output at least one control signal to the hydraulic valve to cause the work implement to smoothly move from the dig location to the dump location while minimizing energy requirements.

Claims

1. A control system for movement of a work implement from a dig location to a dump location, the work implement having a boom defined by a boom joint angle θ

_boom and controllably moved by actuation of a boom hydraulic cylinder, a stick defined by a stick joint angle θ

_stick and controllably moved by actuation of a stick hydraulic cylinder, a bucket defined by a bucket joint angle θ

_bucket and controllably moved by a bucket hydraulic cylinder, and a swing casting defined by a swing joint angle θ

_swing, the control system comprises;

(a) a central processing unit and a memory device;

(b) an initialization module stored on said memory device and adapted to determine initial and final joint angles for an initial cycle of the work implement indicative of the dig and dump locations, respectively;

(c) a hydraulic valve connected to said central processing unit and to the work implement;

(d) a fuzzy control module stored on said memory device, said fuzzy control module comprising a first fuzzy controller adapted to instruct the central processing unit in a finite state manner to output a first de-fuzzified control signal to said hydraulic valve to cause the work implement to smoothly move from the dig location to the dump location while minimizing energy requirements; and

(e) wherein said first fuzzy controller comprises a second fuzzifier adapted to generate a first fuzzified delta linkage inertia value in response to a change between initial and final linkage inertia values.

2. The control system of claim 1, wherein said first fuzzy controller comprises a fuzzy-logic swing valve control module, a fuzzy-logic boom control module, and a fuzzy-logic stick valve control module each adapted to generate said first de-fuzzified control signal for output to said hydraulic valve for each initial and final joint angles value corresponding to the swing joint angle θ

_swing, the boom joint angle θ

_boom, and the stick joint angle θ

_stick.

3. The control system of claim 1, wherein said first fuzzy controller comprises a first fuzzifier adapted to generate a first fuzzified delta joint angle value in response to a change between the said initial and final joint angles.

4. The control system of claim 3, wherein said first fuzzy controller further comprises a first rule base adapted to infer a first fuzzified control signal in response to said first fuzzified delta joint angle value and said first fuzzified delta linkage inertia value.

5. The control system of claim 4, wherein said first fuzzy controller further comprises a defuzzifier adapted to output said first de-fuzzified control signal to said hydraulic valve in response to said first fuzzified control signal.

6. The control system of claim 5, wherein said first and second fuzzifiers each comprise fuzzy logic to infer said first fuzzified delta joint angle value based upon the difference between said initial and final joint angles.

7. The control system of claim 6, wherein said rule base comprises a plurality of rules adapted to output said first fuzzified control signal to said defuzzifier in response to said first fuzzified delta joint angle value and said first fuzzified delta linkage inertia value, said plurality of rules being adapted to conserve energy necessary to move the work element from the dig location to the dump location.

8. The control system of claim 7, wherein said fuzzy-logic boom valve control module and said fuzzy-logic stick valve control module each comprise a second fuzzy controller.

9. The control system of claim 8, wherein said plurality of rules are configured in a rule matrix bounded by a plurality of fuzzified delta linkage inertia values stored in said rule matrix and a plurality of fuzzified delta joint angle values stored in said rule matrix.

10. The control system of claim 9, wherein said first fuzzified delta linkage inertia value and said first fuzzified delta joint angle value correspond to one of said plurality of fuzzified delta linkage inertia values stored in said rule matrix and one of said plurality of fuzzified delta joint angle values stored in said rule matrix, respectively, to thereby infer one of said plurality of rules.

11. The control system of claim 10, wherein each of said fuzzy-logic swing valve control module, said fuzzy-logic boom control module, and said fuzzy-logic stick valve control module comprise a plurality of computer instructions.

12. The control system of claim 11, wherein said plurality of computer instructions has a source code written in C natural computer language.

13. The control system of claim 12, wherein said memory device is a programmable memory.

14. A method for controlling movement of a work implement having at least one hydraulic valve from a specified dig location to a specified dump location, the method comprising the steps of:

(a) determining specified initial and final joint angles for an initial cycle of the work implement indicative of the specified dig and dump locations, respectively;

(b) entering a delta joint angle value into a first fuzzifier;

(c) entering a delta linkage inertia value into a second fuzzifier;

(d) generating a fuzzified delta joint angle value;

(e) generating a fuzzified delta linkage inertia value;

(f) inferring from a rule base a first fuzzified hydraulic valve control signal based upon said fuzzified delta joint angle value and said fuzzified delta linkage inertia value;

(g) generating a de-fuzzified hydraulic valve control signal; and

(h) outputting said de-fuzzified hydraulic valve control signal to the hydraulic valve to control movement of the work implement.