Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1992-10-16
1994-06-07
Evans, F. L.
Optics: measuring and testing
By polarized light examination
With light attenuation
901 47, G01B 1100
Patent
active
053194438
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a detected position correcting method for use in the detection by a sensor of the position of an object, and more particularly to a detected position correcting method for use in the detection of the position of an object by a visual sensor mounted on a robot hand.
2. Background Art
Some practical robotic systems incorporate a vision system for recognizing the position of objects during the process of assembling, palletizing, or otherwise processing the objects. One typical vision system comprises a visual sensor, e.g., a camera, mounted on a robot hand for imaging the objects. To detect the position of an object in such a robotic system, it is necessary for the robotic system to have predetermined information, i.e., calibration data, indicative of the position from which the visual sensor is viewing the object.
The calibration data is effective only with respect to the position and attitude of the visual sensor at the time the visual sensor is calibrated. Therefore, in use, the visual sensor is required to be completely fixed to the position in which it has been calibrated. Detection of the position of an object by a visual sensor mounted on a movable component such as a robot hand requires that the position and attitude of the visual sensor at the time of its calibration be reproduced and employed for accurate positional detection. As a result, the visual sensor is limited as to its position, and can detect objects only within a small range of view. When the position of an object to be detected by the visual sensor is shifted out of the visual range of the visual sensor, for example, the visual sensor can no longer detect the object.
Certain applications need the detection of a plurality of positions by a single visual sensor mounted on a robot hand. Since there are required as many calibration data as the number of positions to be detected, the process of calibrating the visual sensor involves many steps and requires a long period of time.
DISCLOSURE OF THE INVENTION
In view of the aforesaid difficulties of the conventional visual sensor calibration process, it is an object of the present invention to provide a detected position correcting method which can detect the position of the object in a wide range. Another object of the present invention is to provide a detected position correcting method which, after having calibrating a sensor once with respect to a certain position, can detect objects in other positions.
According to the present invention, there is provided a method of correcting data of an object detected by a sensor to determine a position of the object, comprising the steps of determining first calibration data according to a calibration process carried out between the coordinate system of a movable component and the coordinate system of a sensor mounted on the movable component, recognizing the position and attitude of the sensor before the sensor moves, when the calibration process is carried out, recognizing the position and attitude of the sensor after the sensor is moved by the movable component, determining a distance by which the position and attitude of the sensor has moved, from the positions and attitudes of the sensor before and after the sensor moves, determining second calibration data for the sensor after the sensor is moved, based on the distance and the first calibration data, and determining the position of the object based on the second calibration data and data of the object detected by the sensor after the sensor is moved.
The calibration process is carried out to determine first calibration data between the coordinate system of the movable component and the coordinate system of the sensor, The distance by which the position and attitude of the sensor has moved is determined based on the position and attitude of the sensor in the calibration process before the sensor moves, and also on the position and attitude of the sensor after the sensor is moved. The second calibration data for the sensor after it
Arimatsu Taro
Warashina Fumikazu
Watanabe Atsushi
Evans F. L.
Fanuc Ltd
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