JPH01223311A - Pulse encoder - Google Patents

Abstract

PURPOSE:To rapidly detect the trouble of an encoder itself, by providing a deviation counter, a machine feed stand, the encoder and a deviation counter- over detection circuit. CONSTITUTION:When the order pulse corresponding to the feed speed order from a control apparatus 1 is applied to a deviation counter 2, the detection value corresponding to the moving quantity of a machine feed stand 7 is inputted to the counter 2 from an encoder 8 to operate the deviation between the speed order value and the detection value. The deviation value is converted to an analogue value by a D/A converter 3 to be inputted to a servo motor driving apparatus 4 to drive a servo motor 5. A deviation counter-over detection circuit 9 inputs the deviation value of the counter 2 and feeds back the same to the apparatus 1 as erroneous operation when said deviation value exceeds the max. value or the sum of transient response deviation and steady deviation in general or when said deviation value exceeds the limit value operated by the apparatus 1 corresponding to the speed of the feed stand 7 at each time. By this method, the trouble of the encoder 8 itself can be also rapidly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pulse encoder that detects rotation, movement, etc., and particularly relates to a pulse encoder that has a detection function that detects a failure of the encoder itself.

[Conventional technology]

A pulse encoder is a sensor that is attached to the shaft feed motor of an NC machine and used to detect position or rotation speed, and converts analog quantities such as position and speed into electrical digital quantities. Shaft encoders that detect numbers include incremental and absolute types, depending on their output format, and optical encoders and magnetic encoders, which differ depending on the detection method of the sensor section. The optical encoder will be explained with reference to FIGS. 3a and 3b. As shown in FIG. 3a, the encoder includes a disk (code plate) 1 directly connected to the rotating shaft 101 of the motor 100.
02 and this disk 102, it is composed of a light source section 103 and a light receiving section 104. The light emitted from the light source section 103 passes through an aperture made in the disk 102 and reaches the light receiving section 10.
4 extracts this passing light as a digital signal.The positional relationship between A and B of the light receiving section 104 is set so that the phase difference between A and B is 90 degrees, resulting in an output signal as shown in FIG. 3b. It is called an AB phase type encoder because it can detect forward or reverse rotation depending on whether pulse A leads or lags pulse B by 90 degrees. The output of this encoder is
It is usually input to a control device that controls the equipment detected by the encoder.

The output of the encoder consists of pulses that indicate rotational speed, etc., and a failure detection signal that detects a failure of the encoder. This failure detection signal is necessary so that when the pulse output stops, it can be determined whether the device to be detected by the encoder has stopped or whether the encoder has failed.

The fault detection circuit of the AB phase encoder is shown in FIG. 4b. The input of this fault detection circuit consists of the pulse shown in FIG. 3b and its inverted pulse, and the pulses A, A, and A shown in FIG.
B, B phase signal. The output of this failure detection circuit is input to the control device.

This failure detection circuit is usually provided in the control device, and detects A, A,
The B and B phase signals are input to the fault detection circuit through connecting conductors.

Let us consider a case where the above-mentioned connecting conductor is disconnected due to an encoder failure. Assuming that phase A is disconnected, until now phase A has been at H level, and when the bell was on, phase A was at L level, but due to the disconnection, phase A
The phase outputs only H level or L level.

Then, the output of EXORIO, which was outputting H level before the failure, will now output H level and L level.

If the B and B phases are normal, the output of EXORII is H level, and the output of AND12 was H level before the failure, but now H level and L level are output alternately, and a disconnection can be detected. If a break in either phase B or B occurs at the same time as phase A, the output of EXORII will also go to L level,
Since the output of AND12 is still at L level, a disconnection can be detected. Similarly, if at least one of the A, A, B, and B phases is disconnected, the output of AND12 will be L.
Since it becomes a level, it is possible to detect a disconnection.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, it is possible to detect a disconnection in the connecting conductor connecting the encoder detection section and the failure detection circuit, but the failure of the encoder itself, that is, the A, A phase or B, B phase signals are relative to each other (one is at H level). In the case of a failure in which a pulse is no longer generated while the other one remains at L level, the failure detection circuit cannot output a failure signal and cannot detect the failure.

SUMMARY OF THE INVENTION An object of the present invention is to provide an encoder that can quickly detect whether or not a pulse output is not generated from the encoder due to a malfunction of the encoder.

[Means to solve the problem]

The above-mentioned problem 1 includes a pulse output section that outputs three-phase pulses having a predetermined phase difference from each other in response to the movement of the detected section;
This problem is solved by a pulse encoder equipped with a detection means for detecting that either the high level or the low level of the three-phase pulses coincides with each other.

〔Example〕

An embodiment of the encoder according to the present invention is shown in FIGS. 1a to 1c.
This will be explained using figures.

Figure 1a shows each pulse waveform generated by the three-phase pulse encoder detection unit and the mutual phase difference. Each state is expressed as a numerical value from 1 to 6. For example, in state 1, phase A and phase C are at H level B.
The phase is at L level.

Figure 1b shows a state where the A phase has failed and no longer generates pulses while maintaining the H level AH or L level AL state. In this case, in the state indicated by the lower number 7, A, B , C phases are both at the H level, and in the state indicated by the numerical value 0, the A, B, and C phases are all at the L level, which does not occur in FIG. 1a.

FIG. 1c shows an example of a failure detection circuit for detecting an abnormal state indicated by the numerical value O or 7 in FIG. 1b. To explain its operation, in the normal state shown in Figure 1a, at least one of the A, B, and C phases is connected to the other two.
Since there are two phases and different levels i, the AND gate 1
3. Both NOR gates 14 become L level, and the output of OR gate 15 becomes L level, but when all three phases become H level, as shown by numerical value 7 in Fig. 1b, the output of AND gate 13 becomes H level, The output of the NOR gate 14 changes to the L level, and the output of the OR gate 15 changes to the H level. Also, as shown by the numerical value 0 in FIG. 1b, when all three phases become the L level, the output of the AND gate 13 changes to the L level, and the NOR gate The output of OR gate 14 becomes H level, and the output of OR gate 15 also becomes H level. This makes it possible to detect the abnormal state (numerical value 7.0) shown in FIG. 1b.

Next, consider a case where the A phase and B phase fail and no longer generate pulses while maintaining the H level or L level. In this case, it is possible that the A phase holds the H level and the B phase holds the L level, but normally A, B, C
Since the same phase logic gate elements are used, in the case of a failure, one of the levels is uniquely determined. If the A phase and the B phase both maintain the H level or the L level, and the C phase becomes the H level or the L level, the state shown by the numerical value 7 or 0 in FIG. 1b can be detected.

Similarly, if all three phases fail, all are at H level or L level.
Since the level is maintained, the abnormal state shown in FIG. 1b can be detected.

Furthermore, if, for example, the A-phase conductor is disconnected among the connecting conductors that connect the encoder detection section and the failure detection circuit, the A-phase will display only the H level or L level, so the failure can be detected in the same manner as described above. . This allows failure to be detected in the same manner as described above even if any two or three phases are disconnected at the same time.

Next, the case where this encoder is used in a malfunction detection device for a servo mechanism will be explained using FIG. 2.

This servo mechanism includes a control device 1, a deviation counter 2 that extracts the deviation between a command value of the control device 1 and a detected value of a controlled object, a D/A converter 3 that converts the output of the deviation counter 2 from D/A to
A servo motor drive device 4 controlled by the output of the D/A converter 3, a servo motor 5 driven by the servo motor drive device 4, a feed screw 6 moved by the servo motor 5, and a feed screw 6 moved by the feed screw 6. The mechanical feed table 71 is composed of an encoder 8 according to this embodiment which detects the amount of movement of the mechanical feed table 7, and a deviation counter over detection circuit 9 which feeds back the detected value of the deviation counter 2 to the plow control device.

Next, this operation will be explained. When a command pulse corresponding to the feed speed command from the control device 1 is given to the deviation counter 2, a detected value corresponding to the movement amount of the mechanical feed table 7 is inputted to the deviation counter 2 from the encoder 8, and the speed command value is input to the deviation counter 2. and calculates the deviation of the detected value. This deviation value is the D/A converter 3
The voltage signal is converted into a voltage signal and inputted to the servo motor drive device 4 to drive the servo motor 5. The deviation counter over-detection circuit 9 inputs the deviation value of the deviation counter 2, and
If this deviation value generally exceeds the maximum value of the sum of the transient response deviation and steady-state deviation, or if it exceeds the limit value calculated by the control device 1 according to the speed of the mechanical feed table 7 at that time, a malfunction will occur. It is fed back to the control device 1 as follows.

In this device, if the encoder 8 fails and, for example, the A-phase pulse is no longer generated, the A-phase is fixed at the H level or L level, indicating the numerical value 7 or O, as explained in Fig. 1b. Failures can be detected immediately. Also,
If the A phase of the encoder fails while the mechanical feed table 7 is stationary, the failure can be detected as the mechanical feed table 7 will move within a few pulses and indicate a numerical value of 7 or 0 when it starts moving. . The above is a failure in only one phase, but as described above, even if two or three phases fail simultaneously, the numerical value is 7 or 0, and the failure can be detected within a few pulses.

Note that in the case of the conventional AB phase system, the A phase failed;
When pulses are no longer generated while maintaining the phase relationship,
The logic gate shown in FIG. 3b does not allow fault detection.

〔Effect of the invention〕

According to the present invention, a pulse encoder equipped with a three-phase pulse output section having a predetermined phase difference and a detection means for detecting that the levels of the three phases match, can quickly detect a failure in the encoder itself. can do.

[Brief explanation of the drawing]

Figures 1a and 1b are explanatory diagrams of the operation of an embodiment of the present invention, Figure 1c is a logic gate diagram for detecting the failure state shown in Figure 1b, and Figure 2 is an illustration of Figures 1a to 1C. A block diagram of a servo mechanism equipped with the embodiment shown in FIG. 3a is a conventional AB
A perspective view of a phase encoder. Figure 3b shows the pulses generated by the AB phase encoder shown in Figure 3a, Figure 4a shows the pulses in Figure 3b and their inverted pulses, and Figure 4b detects abnormalities in the pulses in Figure 4a. FIG.

Claims (1)

[Claims] (1) A pulse output unit that outputs three-phase pulses having a predetermined phase difference from each other in response to the movement of the detected part, and the levels of either the high level or the low level of the three-phase pulses are the same for all three phases. 1. A pulse encoder comprising: detection means for detecting that