Metal working – Means to assemble or disassemble – With control means energized in response to activator...
Patent
1998-06-24
2000-11-07
Cuda, Irene
Metal working
Means to assemble or disassemble
With control means energized in response to activator...
29718, 29720, B23P 2100
Patent
active
061418633
DESCRIPTION:
BRIEF SUMMARY
TITLE OF THE INVENTION
FORCE-CONTROLLED ROBOT SYSTEM WITH VISUAL SENSOR FOR PERFORMING FITTING
OPERATION
1. Field of the Invention
The present invention relates to a technology of automating a fitting operation required in an assembling process of parts and the like, and more specifically to a force-controlled robot system with a visual sensor in which function of the visual sensor is utilized before and after an inserting action of the force-controlled robot.
2. Description of the Related Art
Fitting operation is one of the basic operations involved in most of assembling processes, and automation of the fitting operation using a robot is already carried out. In the fitting operation with a robot, one workpiece (fit-in workpiece) is held by the robot and inserted into a predetermined portion (normally a concave portion) of the other workpiece (receiving workpiece). A force-controlled robot is often adopted as the robot for holding the fit-in workpiece.
A force-controlled robot is preferably adopted for the fitting operation since it has a function of absorbing fluctuation in relative position and orientation between a fit-in workpiece and a receiving workpiece, and controlling force or moment acting between the workpieces on predetermined conditions. However, even when the force-controlled robot is used for automation of the fitting operation, the following items (1) and (2) have to be settled for performing the fitting operation with high reliability.
(1) Determination of relative position and orientation between a fit-in workpiece and a receiving workpiece (e.g., assembling parts)
Generally, fitting operation with a force-controlled robot is performed through the steps of (i) holding a fit-in workpiece, which has been positioned at a predetermined holding position, by a robot hand fixed to a force sensor, (ii) moving the robot to a predetermined approach position (an inserting action start position) and positioning it at the position, (iii) making the robot perform a force-controlled inserting action, and (iv) releasing the holding of the fit-in workpiece by the robot hand and making the robot retreat.
The relative position and orientation between the fit-in workpiece and the receiving workpiece after the completion of approaching action in step (ii) is important. At that time, if the relative position and orientation between the workpieces is not suitable for starting the inserting action, it is difficult to smoothly perform the inserting action in step (iii). In particular, when an insert portion (convex portion) of the fit-in workpiece and a receiving portion (concave portion) of the receiving workpiece are in tight relation in size and shape, the relative position and orientation need to be adjusted at a high degree. Further, when the holding state of the workpiece in step (i) (the position and orientation of the workpiece relative to the robot hand which is fixed to the force sensor) is not normal, the performance of the force control based on an output of the force sensor drops so that the inserting action is not performed smoothly.
Conventionally, the following measures are taken against the above problems: with high reproducibility. sensor.
Even when the above measure a) is adopted, a workpiece may not be positioned with high precision if the workpiece has a casting surface of low shaping precision. Further, even when the above measure b) is adopted, a fit-in workpiece is apt to be held with an inexact orientation if the shaping precision of the workpiece is low. The above measure c) of correcting the position and orientation of a robot using a visual sensor is known as a general technique. However, such technique is not known that the relative position/orientation between an object held by a robot and an object placed apart from the robot is detected and adjustment of the relative position/orientation of the objects is assured prior to a force-controlled fitting action which requires the positioning with high precision.
(2) Confirmation of the fitting operation after it has done
Even if prec
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Ban Kazunori
Hara Ryuichi
Cuda Irene
Fanuc Ltd.
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