JPH08322276A - Method for establishing origin of linear motor - Google Patents

Abstract

PURPOSE: To provide a method by which the origin of a linear motor can be established easily and accurately. CONSTITUTION: A reversible counter 10d finds the absolute position of the traveling member of a linear motor M by counting reversible pulses generated from a detecting section 10b on detected signals. In the case of establishing the origin of the absolute position, the traveling member is moved in a prescribed direction at a very slow speed after the traveling member is moved to a prescribed position and the counter 10d is reset at the position where the polarity of magnetic signals from a Hall element 12 changes by a set number of times (for example, one time).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for establishing an origin in a linear motor used as a drive source for machine tools, industrial machines and other moving mechanisms.

[0002]

2. Description of the Related Art When a linear motor is used as a drive source for a moving member, a linear encoder is generally used as means for detecting the moving position of the moving member of the linear motor. Further, a method of converting the linear motion of the moving member into a rotary motion and detecting the position of the moving member by a rotary encoder is also adopted. These encoders detect magnetic marks and optical marks that are equally spaced, integrate these marks, and further interpolate between the marks to detect the amount of movement of the moving member. . These encoders can detect the moving amount of the moving member, that is, the incremental amount, but cannot detect the absolute position (the position with respect to a certain coordinate origin). In order to obtain the absolute position, it is necessary to set a reference position for integrating the marks and integrating the interior signal. That is, it is necessary to establish the origin position of the moving member. Conventionally, as the origin establishing method, a method has been adopted in which a limit switch is provided, the moving member is moved from a predetermined direction, and a dog provided on the moving member is established as a starting point at a position detected by the limit switch.

[0003]

The above-described conventional origin establishing method has a problem that a limit switch and a dog are required, and the positions of the limit switch and the dog must be adjusted. Therefore, the purpose of the present invention is to
An object of the present invention is to provide a method for establishing an origin that can easily and accurately establish the origin.

[0004]

According to the present invention, first, the moving member of the linear motor is positioned at a predetermined position. After that, the moving member is moved from the position at a low speed in a predetermined direction. Then, when a predetermined number of changes in the polarity of the magnetic signal detected for controlling the drive current of the linear motor are detected, the position is set as the origin of the position detected by the position detector.

[0005]

In a linear motor using a permanent magnet, a Hall element or the like is used to control the current flowing through the coil, the change in the magnetic flux from the permanent magnet is detected, and the magnetic signal is extracted as a magnetic signal. Are in control.
The present invention uses this magnetic signal to position the moving member (runner side) at a predetermined position of the fixed support portion (stator side), and move the moving member from the position in a predetermined direction.
The change in the polarity of the magnetic signal is detected, and the position at the time when a predetermined number is detected is the origin position in the absolute coordinate position of this moving member.

[0006]

Embodiments of the method of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view for explaining the outline of a linear motor M that embodies the present invention, and FIG. 2 is a central sectional view of FIG. A stator 2 made of a permanent magnet or a coil of the linear motor M is fixedly mounted on a fixed support portion 1 which is a base of a machine tool or an industrial machine to which the linear motor is applied. A traveling element 5 composed of a coil of a linear motor M or a permanent magnet attached to a moving member 3 such as a table is arranged so as to face the body. Reference numeral 4 is a box that houses the runner 5. Linear motion guides 7, 7 are provided between the fixed support portion 1 and the moving member 3 so that the moving member 3 can move in the horizontal direction in FIG. 1 and in the direction perpendicular to the paper surface in FIG. The scale 10a of the linear encoder 10 used as the position detector of the present embodiment is attached to the side surface of the fixed support portion 1, and the moving member 3
A detector 10b of the linear encoder 10 is attached to the. In FIG. 1, the linear motion guide 7, the linear encoder scale 10a, and the detection unit 10b are shown.
Are not shown. The linear encoder 10 may be either an optical type in which a slit pattern is provided on the scale 10a or a magnetic type in which a magnetic pattern is provided, and one pitch of the pattern is set to 1 by the detecting unit 10b.
This is the same as the conventional linear encoder that detects the period.

Further, the fixed support portion 1 and the moving member 3 are
Marks 6a and 6b used when the origin of the linear motor M is set are attached, and when the origin is set, the marks 6a and 6b are used. In the above embodiment, the stator 2 is formed of a permanent magnet array and the runner 5 is formed of a coil.

FIG. 3 is a block diagram of a control system of such a linear motor M, mainly showing the linear encoder 10. Reference numeral 11 is a motor drive control device including a processor, a ROM, a RAM, an input / output circuit, a power amplifier, and the like. The motor drive control device 11 is attached to the runner 5 side of the linear motor M and is a stator. The linear motor M is drive-controlled while controlling the current flowing through the coil based on the magnetic signal from the Hall element 12 which detects the change in magnetic flux from the permanent magnet 2. The signal detected by the detection unit 10b of the linear encoder 10 is input to the signal processing circuit 10c, subjected to waveform processing, and further, the scale 10
One cycle of the signals detected from a is interpolated and divided, and forward and reverse pulses are output according to the moving direction of the moving member (driving direction of the linear motor M), and the pulses are reversible counter 10d. And the position of the moving member 3 is obtained. Then, the motor drive control device 11 uses the reversible counter 10
The absolute position of the moving member is detected based on the count value of d, and the position of the moving member 3 is controlled and the speed is controlled.

As described above, the position of the moving member 3 can be detected by the reversible counter.
When it is set to F, when the moving member 3 moves beyond the detection range of the position, when the moving member 3 is removed from the fixed support portion 1, and then the moving member 3 is attached to the fixed support portion 1, The reference position for detecting the absolute position of the moving member 3 by the reversible counter 10d is displaced. The reversible counter 10b cannot detect the absolute position of the moving member. Therefore, in such a case, the work for fixing the reference position must be performed again.

Therefore, in this embodiment, first, the moving member 3
When the moving member 3 is moved and positioned to a position where the mark 6b attached to the mark 6a matches the mark 6a attached to the fixed support part 1, and an origin search command is input from the operation panel provided in the motor drive control device 11, The processor of the motor drive control device 11 executes a preset origin finding sequence program, drives the linear motor M in a predetermined direction at a very low speed, and moves the moving member 3 in the predetermined direction. When a change in the polarity of the magnetic signal output from the Hall element 12 provided in the linear motor M is detected, a reset command is output to the reversible counter 10d and the reversible counter 10d is output.
Is reset and the origin search processing is completed. As a result, the reversible counter 10d is reset at the first polarity change position of the magnetic signal from the position where the mark 6b attached to the moving member 3 and the mark 6a attached to the fixed support portion 1 coincide, and this position is moved. It becomes the origin of the absolute position of 3. After that, as the linear motor M is driven and the operating member 3 moves, the reversible counter 10d counts up and down based on the signal detected by the detection unit 10b of the linear encoder 10, and the moving member 3 changes according to the value of the reversible counter 10d. The absolute position of will be required.

In the above embodiment, when the home search command is input and the linear motor M is driven to detect the first change in the polarity of the magnetic signal, the reversible counter 10d is reset to carry out the home search. However, the reversible counter 10d may be reset when a change in the polarity of a set number of magnetic signals is counted by inputting a home search command.

Further, in the above-described embodiment, by executing the origin finding sequence program preset and stored by the processor of the motor drive control device 11,
Although the home search is performed, the home search may be performed using a dedicated circuit. For example, a flip-flop that is set by a home search command and a circuit that shapes the magnetic signal from the Hall element 12 and generates a differential pulse at the polarity change are provided, and the differential pulse from the circuit and the flip-flop are set. The output and the AND circuit may be input, and the reversible counter may be reset and the flip-flop may be reset by the output of the AND circuit.

As described above, in this embodiment, the moving member 3
After the moving member 3 is moved in a predetermined direction from a position where the mark 6b attached to the mark 6a and the mark 6a attached to the fixed support portion 1 coincide with each other, at the first or a preset number of magnetic signal polarity change detection positions, Since the reversible counter 10d is reset to establish the origin (reference position) of the absolute position of the moving member 3, it is necessary to align the marks 6a and 6b attached to the first moving member 3 and the fixed support 1 with each other. The origin of the absolute position can be accurately established even with rough alignment. Further, since the origin is obtained by using the magnetic signal from the Hall element 12 or the like provided for controlling the drive current of the linear motor M, no means such as a limit switch and a dog is required, and special It is easy and easy to establish the origin of the absolute coordinate position (origin finding) automatically without any special adjustment.

[0014]

According to the present invention, the origin position of the linear motor is established by utilizing the change in the polarity of the magnetic signal indicating the change in the magnetic flux of the permanent magnet detected to control the drive current of the linear motor. Since it is not necessary to provide a special means for establishing the origin, the work for establishing the origin can be simplified. Further, when establishing the origin position, the origin position can be automatically and accurately established after roughly positioning the moving member, so that the origin can be easily established.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an outline of a linear motor that implements a method of the present invention.

FIG. 2 is a central sectional view of the linear motor in FIG.

FIG. 3 is a block diagram of a control system of the linear motor.

[Explanation of symbols]

 1 Fixed support part 2 Stator 3 Moving member 5 Traveler 6a, 6b Mark 7 Linear motion guide 10 Linear encoder 10a Scale 10b Detection part 12 Hall element M Linear motor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinya Okamoto 3580 Koshinoba, Oshinomura, Minamitsuru-gun, Yamanashi Prefecture FANUC Co., Ltd. Local FANUC Co., Ltd. (72) Inventor Hisao Ishii 3580 Kobaba, Oshinomura, Minamitsuru-gun, Yamanashi Prefecture

Claims (1)

[Claims] 1. A method of establishing an origin of a linear motor, comprising:
After the moving member of the linear motor is positioned at a predetermined position, the moving member is moved at a low speed in the predetermined direction from the position, and the magnetic signal detected to control the drive current of the linear motor A method for establishing the origin of a linear motor in which the position where a predetermined number of changes in polarity are detected is the origin of the position detected by the position detector.