Electricity: motive power systems – Positional servo systems – Multiple mode systems
Patent
1989-08-14
1991-07-09
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Multiple mode systems
318561, 318569, 318653, 32420722, G05B 1118
Patent
active
050309005
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a spindle orientation control apparatus for controlling a spindle motor to stop the motor at a fixed position.
BACKGROUND ART
In a numerically controlled (NC) machine tool, it is necessary to stop a spindle at an arbitrary position with high precision in accordance with a particular purpose. For example, to carry out tapping machining at a predetermined rotational angular position on a workpiece by means of a lathe, it is required that a spindle be stopped at the predetermined rotational position (this is referred to as "spindle orientation").
FIG. 6 is a block diagram illustrating a conventional spindle orientation control apparatus. This spindle orientation control apparatus is such that a spindle A is coupled via a gear d to a servomotor M, acting as a spindle motor, with spindle orientation control being performed by an NC unit a. In FIG. 6, SW denotes a switch for transmitting a command from the NC unit a to a velocity control circuit b and a position control circuit c in a switching fashion. A tachogenerator TG detects an average velocity AV of the servomotor M. Magnetic sensor S detects the rotatioal position of the spindle.
The operation of this orientation control apparatus will now be described with reference to a characteristic diagram of motor velocity shown in FIG. 7. When stop-control is performed while detecting the rotating state of the spindle by the magnetic sensor S, the spindle A is subjected to control at a fixed velocity until an orientation command (ORCM) is outputted from the NC unit a to the velocity control circuit b, or position control circuit c, in accordance with a velocity pattern at the time of orientation control. The rotational velocity of the motor is controlled by a velocity command VCMD from the NC unit a when time t.sub.0 arrives, in response to which the velocity declines at a fixed slope. At time t.sub.1, the rotational velocity of the servomotor M has dropped to a predetermined velocity, from which moment onward there is a transition to rotation at a fixed velocity based on the commanded orientation velocity. At this time, the contact of switch SW is changed over so that the connection of NC unit a is changed from the velocity control circuit b to the position control circuit c. As a result, the spindle A is controlled in accordance with the rotational position signal from the magnetic sensor S from time t.sub.2 onward, so that it is possible to stop the spindle at a target position.
In this conventional spindle orientation control apparatus, spindle velocity attains the orientation velocity owing to input of the velocity AV of servomotor M to the position control circuit c, after which a signal indicative of one revolution of the spindle A is detected, based on the orientation command, and fixed position-stop control becomes possible. This means that the spindle A can be stopped at the fixed position only upon making at least one revolution after the spindle has attained the orientation velocity.
DISCLOSURE OF THE INVENTION
The present invention has been devised in order to solve the foregoing problem and its object is to provide a spindle orientation control apparatus in which position is monitored by velocity pulses at orientation time and at other times as well, wherein a spindle can be stopped at a fixed position in a short period of time.
In accordance with the invention, there can be provided a spindle orientation control apparatus in which a spindle for which there are extracted a spindle stopping-position proximity (LS) signal and a stopping position determination (MS) signal is coupled via coupling means to a spindle motor. The spindle is controlled to stop at a fixed position based on a velocity command conforming to velocity of the spindle. The control apparatus comprises setting means for setting position gain of the spindle, arithmetic means for deciding a first orientation velocity conforming to the position gain and a gear ratio of the coupling means, and a second orientation velocity clamped at a leve
REFERENCES:
patent: 4450393 (1984-05-01), Kohzai et al.
patent: 4703262 (1987-10-01), Fujioka et al.
Kono Shinichi
Takahashi Hironobu
Bergmann Saul M.
Fanuc Ltd.
Shoop Jr. William M.
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