JPS59110594A - Method of detecting origin of machine in shaft control - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting a machine origin in an axis-controlled machine such as a robot.

In axis-controlled machines such as robots and NC devices, a machine origin is determined for each axis, and position control is performed using this machine origin as the origin. When using an absolute encoder that can determine the absolute position as a position detector, the zero position can be determined to be the machine origin, but in the case of an incremental encoder that detects the position by integrating the pulses generated according to the travel distance. Since the absolute position is no longer known once the power is turned off,
A means to separately detect the machine origin is required.

Conventionally, the mechanical origin has been detected by detecting the movement of the final output shaft of a driven part (a part moved by a drive source) using a limit switch, a proximity switch, or the like. That is, for example, in an axis-controlled robot 2 as shown in FIG.
A limit switch 33 for detecting the mechanical origin of the swivel section 26 is disposed at the connecting portion 27 between the swivel section 26 and the second arm 28, and a limit switch 34 for detecting the mechanical origin of the second arm 28 is disposed at the connecting section 29 between the swivel section 26 and the second arm 28. A limit switch 35 for detecting the mechanical origin of the second arm 30 is provided at the connecting portion 31 between the second arm 28 and the second arm 30, and a limit switch 35 for detecting the mechanical origin of the second arm 30 is provided at the connecting portion 31 between the second arm 28 and the second arm 30. A limit switch 36 for detecting the mechanical origin in the wrist swing direction and a limit switch 37 for detecting the mechanical origin in the twisting direction are respectively arranged to detect the mechanical origin. However, arranging the mechanical origin detector on the final output shaft of the driven part in this way is particularly important in the swing direction (arrow A) at the wrist portion 32 of the rosette as shown in FIG.

The mechanism operates in the A' direction) and the twisting direction (arrow B).

Since it has a complicated mechanism for operating in the B' direction), it is extremely difficult and disadvantageous in terms of design. Furthermore, since the wiring from the limit switch and the proximity switch must be led from the wrist portion 32, the wiring often becomes long.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a method for detecting a mechanical origin in axis control in which a mechanical origin detector does not interfere with the configuration of a driven part.

According to the present invention, by interlocking two incremental encoders, for example, with gears having slightly different numbers of teeth, the zero signals emitted from these incremental encoders are emitted simultaneously only once within the operating range of the driven part. The simultaneously transmitted position @ is determined as the machine origin, and the machine origin is detected by detecting that position.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows an example of the internal structure of an incremental encoder used in the present invention.

In FIG. 2, the rotating shaft 21 rotates as a position detection target (not shown) moves. A rotating slit plate 15 is attached to the rotating shaft 21. Rotating slit plate 1
5, a circular pattern 23 is formed concentrically with the rotating shaft 21. The pattern 23 is a portion 15a through which light passes.
and a light blocking portion 15b, and each of these portions 15a and 15b is continuously arranged at a predetermined pitch. In the rotating slit plate 15, one slit 19 is formed inside the pattern 23. This slit 19 is for transmitting a zero signal. A fixed slit plate 1 is located behind the rotating slit plate 15.
6 are arranged.

The fixed slit plate 16 has no.e of the rotating slit plate 15.
Pattern 24 with the same pitch as p y 23 and (j
A slit 19' corresponding to the zero signal slit 19
is formed.

By sandwiching the rotating slit plate 15 and the fixed slit plate 16,
On both sides of these are a photo wig consisting of a light emitting diode 17 and a photo diode 18, and a light emitting diode 2.
0 and a photodiode 22 are respectively arranged. Light emitted from the light emitting diode 17 passes through the patterns 23 and 24 and is received by the photodiode 18. Light emitted from the light emitting diode 20 passes through zero signal slits 19 and 19' and is received by the photodiode 22.

Now, when the rotating slit plate 15 rotates via the rotating shaft 21 as the position detection target moves, the light emitting diode 1
The light emitted from the rotary slit plate 15 is blocked by the pattern 23 of the rotary slit plate 15 a number of times corresponding to the amount of movement of the position detection object. Therefore.

ξ of the pulse signal output from the photodiode 18
By counting the number of pulses, the position of the object to be detected can be detected. Further, the light emitted from the light emitting diode 20 passes through the zero signal slits 19 and 19' every rotation of the rotating slit plate 15 and is received by the photodiode 22. The signal from the photodiode 22 is used for positioning the object to be detected at the time of activation or for correcting a counting error.

FIG. 3 shows an embodiment of the present invention using the above-mentioned incremental encoder.

In FIG. 3, a reduction gear 2 is attached to one of the rotating shafts 6 of the drive motor 1. As shown in FIG.

A gear 3 is attached to the reducer 2, and a chain attached to the gear 3 transmits the driving force of the drive motor 1 to a driven part (not shown) VC. A gear 5 is attached to the other end of the rotating shaft 6 of the drive motor l.

The interior of the incremental encoders 7 and 11 is constructed as shown in FIG. The position detection incremental encoder 7 is for detecting the position of the driven part, and has a gear 9 attached to its rotating shaft 8, which meshes with the gear 5 of the drive motor. Also,
A gear lO is attached to the rotating shaft 8. The incremental encoder 11 is used in combination with the above-mentioned incremental encoder 7 for position detection to detect the machine origin, and a gear 12 is attached to the rotating shaft 13.
They are interlocked. Gear 1° and gear 12 are set to have slightly different numbers of teeth. The ξ pulse train according to the pattern 23 outputted from the incremental encoder 7 is counted and used for position detection. Also.

Zero signals output from the incremental encoders 7 and 11 are used to detect the machine origin.

When the drive motor 1 is rotated, this rotation is transmitted from the rotation shaft 6 to the rotation shaft 8 via the gears 5 and 9, and the position detection incremental encoder 7 is rotated. Also,
The rotation of the rotating shaft 8 is caused by the rotation of the rotating shaft 1 through the gears 1° and 12.
3, and the incremental encoder 11 is rotated.

At this time, since the number of teeth of the gear 10 and the number of teeth of the gear 12 are set to be different, a difference occurs in the amount of rotation between the rotating shaft 8 and the rotating shaft 13. Therefore, the incremental encoder 7
The zero signal transmitted from 1 and 11 gradually shifts.

For example, as in the example shown in FIG. 3, the number of teeth of gear 12 is 10.
, the zero signal of the incremental encoder 11 gradually lags behind the zero signal of the incremental encoder 7, as shown in FIG. Therefore, if the relationship between the number of teeth of gear 10 and gear 12 is set so that the zero signals transmitted from incremental encoders 7 and 11 are transmitted simultaneously only once within the operating range of the driven part, the zero signal will be The position transmitted at the same time can be used as the machine origin.

In order to ensure that the zero signals are emitted only once within the operating range of the driven part, the interval at which the zero signals are emitted at the same time is set to be equal to or longer than the length of the operating range of the driven part. All you have to do is set the number of teeth of each gear so that it satisfies the following formula.

Here, Mll is the rotation amount I Zn 1z of the drive motor 1 when the driven part moves from one end to the other in its operating range.
E 1 e zh t l Z E O are the numbers of teeth of gears 5, 9, and 10°12, respectively. Using this formula,
For example, when M n =80 + "El"z" binding s ZKz is set to 79, it is understood that the value of ZEo should be set to 8o.

Note that the formula shown in the above embodiment is such that no matter where in the operating range the positions where the zero signals are simultaneously transmitted are set, the zero signals are simultaneously transmitted only once within the operating range. This is for when you do. Therefore, if you set the position where the zero signals are simultaneously transmitted to the center of the operating range.

If the interval at which the zero signals are simultaneously transmitted is shorter than the length of the operating range, but at least as long as that length, it is possible to simultaneously transmit the zero signals only once within the operating range circle.

Further, in the above embodiment, a gear is used to transmit the rotation of the drive motor 1 to the incremental encoder, but the transmission is not limited to this, and the transmission may be performed by a transmission means such as a chain or a toothed belt. Good too.

Further, in the above embodiment, the present invention is applied to a rodet, but the present invention is not limited thereto, and can be applied to other axis-controlled machines such as an NC device.

As explained above, according to the present invention, two incremental encoders are interlocked using gears with slightly different numbers of teeth, and the zero signal transmitted from these incremental encoders is within the operating range of the driven part. Since the signals are transmitted only once at the same time, and the position where the signals are transmitted at the same time is determined as the mechanical origin, the mechanical origin is detected by detecting that position.
It is not necessary to arrange a mechanical origin detector such as a limit switch or a proximity switch on the final output shaft of the driven part, and the design of the driven part can be advantageously carried out. Further, it is no longer necessary to lead the wiring of the mechanical origin detector from the driven part, and the wiring can be shortened, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an arrangement row of mechanical origin detectors in a conventional industrial rosette, and FIG. 2 is a perspective view showing an example of the internal structure of an incremental encoder. Fig. 3 is a plan view showing one embodiment of the present invention, and Fig. 4 is a plan view showing an embodiment of the present invention.
FIG. 6 is a waveform diagram showing zero signals respectively emitted from the incremental encoders 7.11 in the figure; l... Drive motor, 5, 9, 10.12... Gear, 6.8, 13.21... Rotating shaft, 7, 11... Incremental encoder, 15... Rotating slit plate. 16...Fixed slit plate, 17.20...Light emitting diode, 18.22...Photodiode, 33,3
4゜35.36,37...Mechanical origin detector. Figure 1 2)'2/1 l. Fig. 3 2 δ 4 Fig. j/Tomoe

Claims (1)

[Claims] Incremental encoder installed to detect the position of the driven part Interlocks a separate incremental encoder,
The ratio for interlocking both incremental encoders is set so that the zero signals transmitted from both of the above-mentioned incremental encoders are within the operating range of the driven section and are simultaneously transmitted only once. A method for detecting a machine origin in axis control in which the transmitted position is detected as the machine origin.