Reference position determination method for industrial robot

• US 5,714,674 A
• Filed: 05/10/1996
• Issued: 02/03/1998
• Est. Priority Date: 09/19/1994
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Yaskawa Denki
• Original Assignee: Kabushiki Kaisha Yaskawa Denki
• Inventors: Nakako, Toru, Tsukuda, Kouji
• Primary Examiner(s): NOLAND, THOMAS
• Application Number:
  US08/640,959
• Time in Patent Office: 634 Days
• Field of Search: 73/1 J, 73/1.79, 33/502
• US Class Current: 73/1.79
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G05B 2219/39048 Closed loop kinematic self calibration, grip part of robot with hand

Abstract

In an industrial robot including a fixed base, a first arm rotatably attached to the fixed base, a second arm rotatably attached to the front end portion of the first arm, and a wrist portion provided with a wrist base and a movable flange attached to the front end portion of the second arm, determination of the reference position of the wrist portion is carried out individually or independently between the wrist portion and the second arm, and determinations of reference positions of the first and second arms, with respect to the fixed base are carried out by way of a positioning jig attached to the fixed base. Since an approach is employed to individually or independently carry out determination of a reference position or positions of one axis or plural axes including the front end axis of the wrist portion of the industrial robot, determination of reference positions can be carried out in the state where the tool is attached to the wrist front end portion.

Claims

1. A reference position determination method for an industrial robot comprising a fixed base, a first arm rotatably attached to the fixed base, a second arm rotatably attached to the front end portion of the first arm, and a wrist portion provided with a wrist base and a movable flange, which is attached to the front end portion of the second arm, the method comprising the steps of:

determining a reference position of the wrist portion with respect to the second arm utilizing a set of positioning means formed on said wrist portion itself and on said second arm itself,

determining reference positions of the first and second arms with respect to the fixed base utilizing a positioning jig attached to the fixed base, and

effecting said step of determining the reference position of the wrist portion with respect to the second arm independently of effecting said step of determining the reference positions of the first and second arm with respect to the fixed base.

2. A reference position determination method for an industrial robot as set forth in claim 1, further comprising:

providing positioning grooves on said wrist base itself and on the movable flange itself and effecting alignment of the said positioning grooves when the movable flange is located at a reference position with respect to the wrist base,

said step of utilizing a set of positioning means formed on said wrist portion itself and on said second arm itself including providing positioning grooves on said wrist portion and on second said arm and effecting alignment of the last said positioning grooves when the wrist portion is located at a reference position with respect to the second arm,

providing reference surfaces in X, Y and Z directions on the wrist base,

providing a positioning jig attached to the fixed base with reference surfaces in the X, Y and Z directions corresponding to the reference surfaces in the X, Y and Z directions of the wrist base, and

effecting firm contact of the reference surfaces in the X, Y and Z directions on the wrist base with the reference surfaces in the X, Y and X directions on the positioning jig respectively to thereby carry out determinations of the reference positions of the first arm and the second arm with respect to the fixed base.

3. A reference position determining method as set forth in claim 2, comprising

providing the positioning jig with a jig body and a positioning piece, and effecting pressing of the positioning piece on the jig body by an elastic body to absorb impact when the wrist base collides with the positioning piece.

4. A method for determining the reference positions of industrial robots of the type having a fixed based, a first arm rotatably attached to the fixed base, a second arm rotatably attached to the first arm, and a wrist means rotatably attached to the second arm comprising the steps of:

determining the reference position of the wrist means with respect to the second arm utilizing alignment devices on said wrist means and on said second arm which align with one another when said wrist means and said second arm are in said reference position;

determining the reference position of the first and second arms with respect to the fixed base;

utilizing a positioning jig attached to the said fixed base for determining the reference position of the first and second arms with respect to the fixed base; and

carrying out said step of determining the reference position of the wrist means with respect to the second arm utilizing said alignment devices independently of determining the reference position of the first and second arms with respect to the fixed base utilizing said positioning jig.

5. A method according to claim 4 comprising:

providing said alignment devices in the form of a first groove in the wrist means and a second groove in the second arm;

aligning said first and second grooves to thereby determine that said wrist means is in said reference position with respect to the second arm;

providing mutually perpendicular surfaces on the wrist means disposed in the X, Y and Z directions;

providing mutually perpendicular surfaces on the positioning jig disposed in the X, Y and Z directions; and

positioning said mutually perpendicular surfaces on the wrist means firmly into contact with the respective mutually perpendicular surfaces on said positioning jig such that the mutually perpendicular surfaces on said wrist means extending in the X, Y and Z directions are firmly in contact respectively with the mutually perpendicular surfaces on said positioning jig extending in the X, Y and Z direction to thereby determine the reference position of the first and second arm with respect to the fixed base.

6. A method according to claim 5 wherein said wrist means includes a wrist base and a movable flange and further comprising:

determining the reference position of the movable flange with respect to the wrist base by providing further alignment devices on said movable flange and on said wrist base which align with one another when said movable flange and said wrist base are in their reference position.

7. A method according to claim 6 further comprising:

providing said further alignment devices in the form of a third groove in the movable flange and a fourth groove in the wrist base; and

aligning said third and fourth grooves to thereby determine that said movable flange is at said reference position with respect to the wrist base.

8. A method according to claim 4 further comprising providing the positioning jig with a jig body and a positioning piece, and effecting an elastic connection between said positioning jig and said jig body to absorb impact when the wrist base body collides with the positioning piece.