Electricity: motive power systems – Positional servo systems – With particular 'error-detecting' means
Patent
1987-11-04
1989-05-02
Miska, Vit W.
Electricity: motive power systems
Positional servo systems
With particular 'error-detecting' means
318601, 318602, G05B 106
Patent
active
048272035
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a detector for detecting the rotational position of a rotor of a motor, and more particularly to a rotational position detector capable of detecting the absolute rotational position of a rotor shaft of a motor, and at the same time detecting the magnetic pole position of the rotor controlling the motor drive.
BACKGROUND ART
To drive an AC servo motor or a stepping motor, it is necessary to control an electric current passing through the stator of the motor in accordance with the rotational position of a predetermined magnetic pole of the rotor (hereinafter referred to as "the magnetic pole position") relative to the stator of the motor. In this connection, a detector is required, which is capable of detecting the magnetic pole position of the rotor to generate a signal representative of the detected magnetic pole position of the rotor. Conventionally, the detection of magnetic pole position of the rotor has been carried out by: the rotor; of the rotor at intervals of a period equal to a value calculated by dividing a rotational period of a motor by a number of poles of the rotor or half the number of the rotor poles so that a detected absolute data indicates the magnetic pole position of the rotor; and way of gears or the like so as to rotate a number of revolutions equal to a number of rotor poles or half the number of the rotor poles per one revolution of the motor to output an absolute detection data in one revolution of the detector as a rotor magnetic pole position data.
However, none of the above-mentioned conventional methods can carry out absolute detection for one revolution of a motor, so that they require another detector to effect this kind of absolute detection. Moreover, to detect a rotor magnetic pole position, these methods use a detector constructed in conformity with a number of rotor poles. That is, they have to use different detectors for motors which have a different number of poles, resulting in the necessity of preparing many kinds of detectors for the magnetic pole position detection. Accordingly, problems such as increased complexity in both designing and manufacturing occur. Furthermore, in the above-mentioned method (3) using gears, abration of the gears and backlash can occur, which adversely affects detection accuracy.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a rotational position detector which is capable of carrying out absolute detection for one revolution of a motor, and is adaptable to a variety of motors having different numbers of rotor poles, requiring only minor modification of electrical parts.
To achieve the above-mentioned object, in a first embodiment, the present invention comprises an absolute type position detector coupled to a rotor shaft of a motor for detecting an absolute position of the rotor shaft in one revolution of the rotor shaft, and for outputting a coded signal indicative of the detected position. A code converting means for converting the coded signal from the absolute type position detector into a coded rotor magnetic pole position signal for controlling of the motor drive, and for the outputting same, is also provided.
According to a second embodiment, the present invention comprises a position detector coupled to a rotor shaft of a motor for outputting a coded signal representative of an absolute position of the rotor shaft in one revolution of the rotor shaft and for sequentially outputting increment pulses corresponding to the revolution of the rotor shaft. A code converting means for converting the coded signal from the position detector into a second coded signal representative of a rotor magnetic pole position for controlling the motor drive, and for outputting the second coded signal is provided. A counter is arranged to be reset to a predetermined value every time the counter counts pulses which equal the increment pulses generated during one cycle of the magnetic pole position detector. When a power supply is turned on, an output from the c
REFERENCES:
patent: 4507590 (1985-03-01), Miyazaki
Bergmann Saul M.
Fanuc Ltd
Miska Vit W.
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