Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Reexamination Certificate
1999-03-01
2001-11-20
Fletcher, Marlon T. (Department: 2837)
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
C318S605000, C318S606000
Reexamination Certificate
active
06320344
ABSTRACT:
TECHNICAL FIELD
This invention relates to a position control device to feedback-control a position of a rotary shaft and a travel position of a movable part connected to the rotary shaft by detecting a rotational position of the rotary shaft. Particularly, the present invention relates to a position control device suitable to control a rotational position of a main spindle of a machine tool.
RELATED ART
As to a position sensor to detect a rotational position and speed of a rotary shaft, various position sensors to optically, magnetically or electrically detect a position and speed are well known. In these position sensors, an element to be detected in the position sensor is mounted to the rotary shaft so as to rotate the element to be detected together with the rotary shaft, and a rotational position of the rotary shaft is detected by optically, magnetically or electrically detecting a rotational position of the element to be detected.
When the element to be detected in the position sensor is mounted in an eccentric state or when an eccentric error caused by a mounting error occurs in case of mounting the element to be detected to the rotary shaft, the rotational position of the rotary shaft is made different from the rotational position detected by the position sensor, resulting in a reduction of detecting accuracy of the detected rotational position of the rotary shaft. For this reason, according to the prior art, an attempt has been made to mount the element to be detected to the rotary shaft exactly with precision so as to prevent any eccentric error from occurring. Also, the prior art has disregarded a position detection error caused by the eccentric error developed even if the element to be detected is mounted with precision.
When an attempt is made to control the position with high precision, there arises a problem that the position detection error caused by the eccentric error occurs in position control, and the position cannot be controlled with high precision. Further, it is restrictive and very difficult to mount the element to be detected in the sensor to the rotary shaft precisely without causing eccentricity.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a position control device which enables accurate position control through correction of the position detection error caused by the above eccentric error.
For attaining the above object, according to one aspect of a position control device of the present invention, there is provided a position control device which controls a position on the basis of a position feedback signal from a position sensor mounted on a rotary shaft to detect a rotational position of the rotary shaft, wherein, detection error data caused by the eccentricity or the mounting error of an element to be detected in the position sensor mounted on the rotary shaft is calculated on the basis of an output signal from the position sensor mounted on the rotary shaft and is stored in the position control device, whereby the detection error data is corrected in regard to a command rotational position for a motor which drives the rotary shaft, providing a corrected command rotational position for the motor.
Further, according to another aspect of a position control device of the present invention, there is provided a position control device which controls a position on the basis of a position feedback signal from a position sensor mounted on a rotary shaft to detect a rotational position io of the rotary shaft, wherein a program, for finding detection error data caused by the eccentricity or the mounting error of an element to be detected in the position sensor mounted on the rotary shaft is stored in the position control device, and the program is executed when a revolving speed exceeds a predetermined value so that the detection error data is automatically found on the basis of an output signal from the position sensor to be stored in a memory in the position control device, and a commanded rotational position is corrected on the basis of the stored detection error data, providing a corrected command rotational position for a motor.
According to the position control device of the present invention, even if a center of rotation of the element to be detected is made eccentric from a center of the rotary shaft due to the eccentricity of the element to be detected in the position sensor or the mounting error occurring in case of mounting the element to be detected on the rotary shaft, a command is issued to the motor which drives the rotary shaft, after correction of the eccentric error of the rotational position detected by the position sensor, whereby accurate position control is enabled.
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patent: 4827203 (1989-05-01), Sakano
patent: 5237509 (1993-08-01), Ueta et al.
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patent: 5525885 (1996-06-01), Sato
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patent: 1-270784 (1989-10-01), None
patent: 5-2214 (1993-01-01), None
patent: 6-327278 (1994-11-01), None
Okuda Kanamasa
Sakamoto Keiji
Taniguchi Mitsuyuki
Fanuc Ltd.
Fletcher Marlon T.
Staas & Halsey , LLP
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