Positioning system using robot

• US 10,525,598 B2
• Filed: 03/23/2017
• Issued: 01/07/2020
• Est. Priority Date: 03/25/2016
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Takahashi, Yuutarou, Takizawa, Shouta, Warashina, Fumikazu
• Primary Examiner(s): Patton, Spencer D
• Application Number:
  US15/467,434
• Publication Number:
  US 20170274534A1
• Time in Patent Office: 1,020 Days
• CPC Class Codes: B25J 19/023 including video camera means
• CPC Class Codes: B25J 9/1641 compensation for backlash, friction, compliance, elasticity in the joints
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: G05B 2219/39008 Fixed camera detects reference pattern held by end effector
• CPC Class Codes: G05B 2219/39024 Calibration of manipulator
• CPC Class Codes: G05B 2219/39039 Two cameras detect same reference on workpiece to define its position in space
• CPC Class Codes: G05B 2219/39045 Camera on end effector detects reference pattern
• CPC Class Codes: G05B 2219/39192 Compensate thermal effects, expansion of links

Abstract

A positioning system using a robot, capable of eliminating an error factor of the robot such as thermal expansion or backlash can be eliminated, and carrying out positioning of the robot with accuracy higher than inherent positioning accuracy of the robot. The positioning system has a robot with a movable arm, visual feature portions provided to a robot hand, and vision sensors positioned at a fixed position outside the robot and configured to capture the feature portions. The hand is configured to grip an object on which the feature portions are formed, and the vision sensors are positioned and configured to capture the respective feature portions.

Claims

1. A positioning system comprising:

a robot having a movable arm;

a visual feature portion provided to one of a front end of the arm or a fixed position outside the robot;

a plurality of vision sensors provided to the other of the front end of the arm or the fixed position outside the robot, and configured to capture the visual feature portion; and

a processor configured to;

detect a parameter of a feature including at least one of a position, a posture and a size of the visual feature portion, on an image captured by the plurality of vision sensors;

store the parameter of the feature, as a first parameter of the feature, while the front end of the arm is positioned at a predetermined commanded position;

capture the feature portion by using the vision sensors, at a time point different from when the first parameter of the feature is detected, while the front end of the arm is positioned at or near the predetermined commanded position, so as to obtain a second parameter of the feature;

calculate a first commanded amount of movement of the robot, so that the second parameter of the feature coincides with the first parameter of the feature with respect to all of the vision sensors, based on a difference between the second parameter of the feature and the first parameter of the feature stored;

calculate a second commanded amount of movement, based on the first commanded amount of movement and a mechanical parameter determined from mechanical characteristics of the robot; and

drive the front end of the arm based on the second commanded amount of movement,

wherein the processor is further configured to repeat the calculation of the second commanded amount of movement and the driving of the front end of the arm based on the second commanded amount of movement, until the first commanded amount of movement is equal to or lower than a predetermined threshold, so that the front end of the arm gradually approaches a determined position, and is positioned at the determined position with an accuracy higher than an inherent positioning accuracy of the robot, and

wherein the processor is further configured to;

set the first commanded amount of movement as the second commanded amount of movement when the first commanded amount of movement is equal to or higher than the parameter determined from the mechanical characteristics of the robot, and

set the second commanded amount of movement as a value obtained by multiplying the first commanded amount of movement by a coefficient lower than one when the first commanded amount of movement is lower than the parameter determined from mechanical characteristics of the robot.

2. The positioning system as set forth in claim 1, wherein the processor is further configured to:

calculate an amount of motion of each movable part of the robot generated by the movement of the robot based on the first commanded amount of movement; and

calculate the second commanded amount of movement based on the amount of motion of each movable part.

3. The positioning system as set forth in claim 1, wherein the processor is further configured to:

estimate performance deterioration of the robot due to a temporal change from a working situation of the robot;

adjust the parameter determined from the mechanical characteristics of the robot based on the estimation; and

calculate the second commanded amount of movement based on the first commanded amount of movement and the adjusted parameter.

4. The positioning system as set forth in claim 1, wherein the plurality of vision sensors capture one feature portion.

5. The positioning system as set forth in claim 1, wherein the plurality of vision sensors capture a plurality of feature portions, respectively.