JPH1164040A - Device for detecting abnormality in encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for surely detecting abnormalities in an encoder, when an abnormality occurs in its output signal. SOLUTION: In case where a motor 1 rotates continuously in one direction while a controller 5 outputs a unidirectional command signal, the level of up/ down signal according to the output pattern of A- and B-phase signals of an encode 2 so changed, and a counter 3 indicates the changing over of up-down counting operation. As a result, an abnormality detecting circuit 6 outputs an abnormality detection signal to the controller 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder abnormality detecting device for outputting pulse signals having phases different from each other by 90 degrees as an A-phase signal and a B-phase signal with a linear displacement or a rotational displacement of a displacement body.

[0002]

2. Description of the Related Art For example, an optical rotary encoder (hereinafter, referred to as an encoder) is provided with a disk-shaped scale having a plurality of slits on an outer peripheral portion thereof, for example, on a rotating shaft of a motor as a displacement body, and sandwiching the scale. A light emitting element and a light receiving element corresponding to the A, B, and Z phases are arranged.

When the scale rotates with the rotation of the motor, the light-receiving element receives the light emitted from the light-emitting element through the slit, and as shown in FIG. A B-phase signal and a Z-phase signal (origin signal) output only once each time the motor makes one rotation are output. By obtaining these A, B and Z phase signals, the rotation position and rotation direction of the rotor are detected,
Various controls related to the electric motor are performed.

In such an encoder, for example,
If dust adheres to the slit, light emission from the light emitting element is blocked, and a pulse signal that should be output from the light receiving element is missing or a pulse that is not an original signal due to superposition of electrical noise. A signal may be output. In such a case, an error occurs in counting the rotational position based on each output signal.

Conventionally, in order to solve such a problem, the difference between the count value at the time when the Z-phase signal is output between the current time and the previous time is obtained, and the difference value is compared with the resolution of the encoder. A method for detecting an abnormality has been proposed.

However, in such a conventional system, Z
For example, since the count value of the counter is latched at the rising edge of the phase signal, a detection error occurs between the forward rotation and the reverse rotation. Referring to FIG. 8, in this example, when the motor is rotating forward and the A-phase signal is in the advanced phase, the count value “3” is detected as the origin position, and the motor is rotating in the reverse direction and the B-phase signal Is a leading phase, the count value “7” is detected as the origin position. That is, the pulse width of the Z-phase signal with respect to the count timing is an error.

[0007]

In order to reduce this error, the pulse width of the Z-phase signal may be reduced as much as possible. However, considering the noise margin, it is limited to the same pulse width as the A- and B-phase signals. It is unavoidable that an error of two pulses occurs.

In this case, it is easy to correct an error corresponding to the pulse width of the Z-phase signal between the forward rotation and the reverse rotation. However, the encoder itself has a speed and a deviation of the mechanical system between the forward rotation and the reverse rotation. The Z-phase signal always displaces from the A- and B-phase signals due to, for example, temperature change, vibration, and variations in device characteristics in the detection system. In order to reduce the influence of the displacement, it is necessary to form the edge of the Z-phase signal so as to be located between the edges of the A and B-phase signals as shown in FIG. The higher the resolution, the more difficult it is to make.

As described above, conventionally, it has been difficult to reliably detect the abnormality of the encoder. Since the determination is made only by the difference between the count values at the time of outputting the Z-phase signal,
If an erroneous count occurs many times in a state where the abnormality is not correctly detected, the error is accumulated and the deviation of the detection position becomes large.

Conventionally, it is impossible to check for erroneous detection without outputting a Z-phase signal.
With a linear encoder, the Z-phase signal is 1
Since the output is performed only once, the chances of performing the check are reduced, and the possibility that errors are accumulated increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an encoder abnormality detection device capable of reliably detecting an abnormality in an encoder signal output. .

[0012]

In order to achieve the above object, an encoder abnormality detecting device according to the present invention provides an encoder for detecting a pulse signal having a phase difference of 90 degrees from an A-phase signal with a linear displacement or a rotational displacement of a displacement body. And an apparatus for detecting abnormality of an encoder provided with A-phase signal output means and B-phase signal output means for outputting as the B-phase signal, wherein the A-phase and B-phase signals output by the A-phase and B-phase signal output means are provided. The displacement position data of the displacement body is output by counting up or down the signal, and the A-phase and B-phase signals are output.
Position data output means for determining up / down of the count operation according to the displacement direction of the displacement body determined based on the phase signal, and outputting an up / down signal indicating up / down of the count operation currently being performed; Control means for outputting a displacement command to the displacement body and outputting a one-way command signal when the displacement direction of the displacement command is continuously constant; and And an abnormality detection means for outputting an abnormality detection signal when the counting operation indicated by the up / down signal output by the position data output means is switched between up and down. I do.

With this configuration, when the control means outputs the one-way command signal and the displacement body is continuously displaced in a fixed direction, the up / down signal output from the position data output means is output. Is either up or down, and when it changes, it clearly indicates that there is an abnormality in the output pattern of the A and B phase signals. Therefore, the abnormality detection means can reliably detect that there is an abnormality in the position detection by outputting an abnormality detection signal based on the above-mentioned event.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a functional block diagram showing an electrical configuration of the abnormality detection device for the encoder. An optical encoder 2 is attached to a rotor of the electric motor (displacement body) 1. Although not specifically shown, a disk-shaped scale having concentrically arranged slits corresponding to the A-phase, B-phase, and Z-phase signals of the encoder 2 is attached and fixed to the rotating shaft of the electric motor 1.

A light emitting element (not shown) made of, for example, an LED corresponding to each phase signal, and light receiving elements 2A, 2B and 2Z made of, for example, a photodiode (A phase, B phase and Z
Phase signal output means) are disposed so as to face each other across the slit of the scale. As in a general encoder, the A-phase signal and the B-phase signal are pulse signals output with a duty ratio of 50% and a phase difference of 90 degrees from each other, and the Z-phase signal rotates the rotating shaft of the electric motor 1 once. Every,
This is a pulse signal that is output only once when the reference point of the rotational displacement is reached.

Output terminals of the light receiving elements 2A and 2B are connected to different input terminals of a position data output means and an up / down counter (hereinafter referred to as a counter) 3, respectively. The clock signal CLK is supplied from the clock circuit 4 to the clock input terminal of the counter 3, and the counter 3 outputs the A phase and the B phase output from the light receiving elements 2A and 2B.
When the input state of the rising or falling edge of the phase signal changes, the up / down counting operation is performed in synchronization with the clock signal CLK.

The counter 3 determines whether the current counting operation is up or down (that is,
A U / D signal (up / down signal) indicating whether the rotation direction of the electric motor 1 is forward rotation or reverse rotation is output to an abnormality detector 6 described later. The U / D signal indicates that an up-count operation is performed at a high level and a down-count operation is performed at a low level.

The count value of the counter 3 returns from the maximum value to zero when the motor 1 makes one rotation (in the case of normal rotation). Note that the cycle of the clock signal CLK output from the clock circuit 4 is set to be sufficiently shorter than the output cycle of the A-phase and B-phase signals when the rotation speed of the electric motor 1 is maximized.

An output data bus BL from which the count value of the counter 3 is output is connected to an input port of a control device (control means) 5 composed of a microcomputer or the like. Although not specifically shown, the Z-phase signal output from the light receiving element 2Z is given as a latch signal to a latch circuit for latching the count value of the counter 3 at the origin position. The origin position latched by the latch circuit is provided to the control device 5 and used for detecting the rotational position of the electric motor 1 and the like.

The clock signal CLK is supplied from the clock circuit 4 to the clock input terminal of the abnormality detector 6. The abnormality detector 6 includes a flip-flop, a logic gate circuit, and the like, as described later, and outputs an abnormality detection signal to the control device 5 as a one-shot pulse signal when detecting an abnormality in the signal output of the encoder 2. It has become.

FIG. 2 is a diagram showing the electrical configuration of the up / down signal generation circuit 3a inside the counter 3. In FIG. 2, an A-phase signal and a B-phase signal are supplied to D input terminals of D flip-flops 7a and 7b, respectively, and a Q output terminal of these D flip-flops 7a and 7b is connected to a D output terminal of the next stage, respectively. The flip-flops 8a and 8b are connected to D input terminals. In addition, these D flip-flops 7a,
A clock signal CLK is commonly supplied from a clock circuit 4 to clock input terminals of 7b, 8a and 8b.

Here, Q of the D flip-flop 7a,
The signals output from the Q output terminal are A0 and / A0, respectively, and the signals output from the Q and / Q output terminals of the D flip-flop 8a are A1 and / A1, respectively. The signals output from the Q and / Q output terminals of the D flip-flop 7b are B0 and / B0, respectively, and the signals output from the Q and / Q output terminals of the D flip-flop 8b are B1 and / B, respectively.
Let it be 1.

That is, the signals A0 and B0 are signals obtained by synchronizing the A-phase and B-phase signals with the clock signal CLK.
1, B1 are the signals A0, B0 which are 1
The signal is delayed by the clock.

Four-input AND gate 9a forming a group of four
To 9d input terminals in the following combinations, respectively.
Signals from flip-flops 7a to 8b are provided. AND gate 9a: (/ B1, / A1, / B0, A0): 1 AND gate 9b: (B1, A1, B0, / A0): E AND gate 9c: (/ B1, A1, B0, A0): 7 AND gate 9d: (B1, / A1, / B0, / A0): 8 The output terminals of these four AND gates 9a to 9d are connected to the input terminals of a four-input OR gate 10a, respectively. The output terminal of the OR gate 10a is connected to the S input terminal of the RS flip-flop 11.
In addition, after the parentheses, B1 (MSB), A1,
This is a hexadecimal number representing a level pattern of "1, 0" represented by four bits B0 and A0 ("/" indicates negative logic, that is, "0").

Signals are provided to the input terminals of the four-input AND gates 12a to 12d, which form another group of four, in the following combinations, respectively. AND gate 12a: (B1, / A1, B0, A0): B AND gate 12b: (/ B1, A1, / B0, / A0): 4 AND gate 12c: (/ B1, / A1, B0, / A0) : 2 AND gate 12d: (B1, A1, / B0, A0): D And the output terminals of these four AND gates 12a to 12d are connected to the input terminals of a four-input OR gate 10b, respectively. The output terminal of the OR gate 10b is R
It is connected to the R input terminal of the S flip-flop 11. The U / D signal is output from the Q output terminal of the RS flip-flop 11.

The operation of the up-down signal generation circuit 3a is
This will be described with reference to the timing chart of FIG. When the motor 1 is rotating forward, the A-phase signal has a leading phase with respect to the B-phase signal. In this case, each signal A0, B0, A1,
When the combination of the levels of B1 is viewed as a hexadecimal number represented by 4 bits, the following pattern is repeated (FIG. 3).
(See (a) to (g)). 0, 1, 5, 7, F, E, A, 8, 0, 1, 5,... When the motor 1 is rotating in the reverse direction, the B-phase signal has a leading phase with respect to the A-phase signal. In this case, the hexadecimal pattern similarly represented by the combination of the levels of the signals A0, B0, A1, and B1 is as follows. 0,2, A, B, F, D, 5,4,0,2, A, ...

That is, “0, 5, A, F” is a hexadecimal number pattern that appears commonly during normal rotation and reverse rotation,
7, 8, and E "appear only during normal rotation and" 2, 4, B, D "appear only during reverse rotation, and therefore, during forward rotation," 1 "is set by AND gates 9a to 9d and OR gate 10a. , 7, 8, E "appear, the UP signal is output, the RS flip-flop 11 is set, and the U / D signal is set to the high level. In the case of reverse rotation, the AND gates 12a to 12d and the OR gate 10b By "2,
4, B, D "appears, the DOWN signal is output and R
The S flip-flop 11 is reset to set the U / D signal to low level (see FIGS. 3H to 3J).

FIG. 4 shows a detailed electrical configuration of the abnormality detector 6, and FIG. 5 shows signal waveforms at various parts of the abnormality detector 6. The U / D signal is supplied to the D input terminal of the D flip-flop 13a and one input terminal of the EXOR gate 14, and the other input terminal of the EXOR gate 14 is connected to the Q output terminal of the D flip-flop 13b. Have been. The output terminal of the EXOR gate 14 is connected to one input terminal of the AND gate 15.

The one-way command signal is supplied to the D input terminal of the D flip-flop 13b, and the Q output terminal of the D flip-flop 13b is connected to the other input terminal of the AND gate 15. The clock signal CLK is supplied to clock input terminals of the D flip-flops 13a and 13b. And AND gate 1
The output terminal 5 outputs an abnormality detection signal.

The operation of the abnormality detector will be described with reference to FIG. When the level of the U / D signal changes as shown in FIG. 5A, the clock signal C is output from the D flip-flop 13a.
A signal synchronized with the LK is output (see FIG. 5C). Then, the EXOR gate 14 takes an exclusive OR of the U / D signal and the signal, and outputs a one-shot pulse signal corresponding to the rising or falling of the U / D signal (FIG. 5D). reference).

On the other hand, when the one-way command signal is output as shown in FIG. 5E, a signal synchronized with the clock signal CLK is output from the D flip-flop 13b (FIG. 5).
(F)). Then, a logical AND with the signal is obtained in the AND gate 15. That is, if the level of the U / D signal changes while the one-way command signal is being output (is high), an abnormality detection signal is output.

Next, the operation of the present embodiment will be described with reference to FIGS. FIG.
6 is a timing chart when a phase and a B-phase signal are output normally. When started, the control device 5 gives a speed command to the electric motor 1 via a drive circuit (not shown) according to a control program stored in an internal ROM or the like, for example, as shown in FIG. .

When the speed command is "stop" (see FIG. 6 (a), time point A), the motor 1 alternately repeats normal rotation and reverse rotation within the range of the minimum displacement position, thereby obtaining the current rotational position. At this time, the level of the U / D signal alternates between high and low in accordance with the direction of displacement of the electric motor 1 (see FIG. 6D).

When the level of the U / D signal alternates between high and low, a signal is also output from the EXOR gate 14 of the abnormality detection circuit 6 (see FIG. 6 (e)). Since the one-way command signal is not output from the control device 5 (see FIG. 6C), no abnormality detection signal is output (see FIG. 6F).

Next, when a speed command (acceleration) in the forward direction is given from this state (see FIG. 6A, time point B),
The electric motor 1 starts normal rotation with a slight time delay after the speed command is given (see FIG. 6B, time point C). Then, the U / D signal becomes a high level indicating an up-count (see FIG. 6D, time point D). While continuously giving the forward or reverse speed command to motor 1, controller 5 outputs a one-way command signal indicating that the rotation direction of the speed command is constant (high level). I do.

At this time, since the response of the electric motor 1 has a following delay of the drive system, the controller 5 delays the output timing of the one-way command signal with respect to the speed command in anticipation of the following delay. (For example, when the delay time t1 has elapsed since the start in the normal rotation direction) (see FIG. 6C, time point E).

In a state where the electric motor 1 has reached a steady speed (FIG. 6)
(B), time point F) After the operation has been performed for a while, a speed command for instructing deceleration is output (see FIG. 6 (a), time point G).
When the speed command reaches zero (see time point H in FIG. 6A), the output of the one-way command in-progress signal is stopped at that time point H. Then, when the speed of the electric motor 1 gradually decreases from the steady speed and passes through the zero point (see time point I in FIG. 6B), the electric motor 1 starts to rotate in the reverse direction.

After passing through the zero point, the phase relationship between the A-phase and B-phase signals output from the encoder 2 changes (A-phase advance → B-phase advance), and the level of the U / D signal changes from high to low. I do. At that timing, the EXO of the abnormality detection circuit 6
A signal is also output from the R gate 14 (see FIG. 6).
(E), see time point I). At this time point I, the one-way command in-progress signal is not output from the control device 5 (see FIG. 6).
(See FIG. 6C), again, no abnormality detection signal is output (see FIG. 6F).

Thereafter, when a stop command is output after the operation has been performed for a while in a state where the motor 1 has reached the steady speed in the reverse direction, the speed of the motor 1 gradually decreases from the steady speed to reach the zero point. The electric motor 1 alternately repeats the normal rotation and the reverse rotation in the range of the minimum displacement position as in the first state.

Next, a case where the output pattern of the A-phase and B-phase signals from the encoder 2 is abnormal will be described with reference to the timing chart of FIG. In a state where the electric motor 1 is continuously rotating forward and the one-way command signal is being output from the control device 5 (see FIG. 7 (h)), as shown by a two-dot chain line in FIG. 7 (a). , A pulse of the A-phase signal is temporarily generated.

Prior to the occurrence of a missing pulse, the U / D signal is at a high level, indicating that the counter 3 is performing an up-count operation. The hexadecimal pattern represented by the combination of the levels of the signals A0, B0, A1, and B1 at the time of occurrence of the missing pulse is 0, 2, A, A, A,
8, 0, ....

Since the pattern "2" appears when the motor 1 rotates in the reverse direction (when the counter 3 counts down) as shown in FIG. 3, the AND gate 12c goes high at that time and the DOWN signal is output. Output (Fig. 7
(See (i)). Then, the RS flip-flop 11 is reset and the U / D signal goes to a low level. The abnormality detector 6 detects the falling of the U / D signal and outputs a signal. A detection signal is output (see FIGS. 7 (k) and 7 (l)).

Also, when the output pattern of the A-phase and B-phase signals returns to the normal state and the pattern "8" is output, the AND gate 9d is set to the high level and the UP signal is output. 7 (h)), the RS flip-flop 11 is set, the U / D signal changes from low level to high level, and since the one-way command signal is at high level, the abnormality detector 6 outputs an abnormality detection signal. .

The control device 5 to which the abnormality detection signal is given,
At that time, the operation of the electric motor 1 is stopped, or the fact that the abnormality of the encoder 2 is detected is displayed on a display device (not shown) to notify the user.

As described above, according to the present embodiment, when the control device 5 outputs a one-way command signal and the motor 1 is continuously rotating in a fixed direction, the counter 3 controls the encoder 2 When the level of the U / D signal output based on the output pattern of the A-phase and B-phase signals changes to indicate that the counting operation has been switched between up and down, the abnormality detection circuit 6
Output an abnormality detection signal to the control device 5.
Therefore, unlike the related art, it is possible to detect an abnormality in the signal output pattern of the encoder 2 without using the Z-phase signal of the encoder 2, and it is possible to reliably detect the abnormality.

The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications or extensions are possible. The pulse signal is output at a different timing than usual due to the superimposition of noise, not limited to the case where a pulse is missing in the A-phase and B-phase signals of the encoder 2, and the motor 1 is rotating forward or backward. Nevertheless, abnormality detection is possible even when a signal output pattern appears as if the B-phase and A-phase signals are advanced phases. The output of the one-way command in-progress signal may be stopped after the elapse of the delay time t2 from the time point H in FIG. 6A where the speed command changes from deceleration to “0”. With such a configuration, the time during which the abnormality can be detected can be set longer. However, the delay time t2 is set in a range where the output stop timing of the one-way command signal does not reach the time point I.

The delay time t from the start in the normal rotation direction
Instead of outputting the one-way command signal when 1 has elapsed, the rotational speed of the electric motor 1 is detected from the output signal of the encoder 2 and the rotational speed is reduced to, for example, 50% with respect to the given speed command. At this point, the one-way command signal may be output. Alternatively, the output may be made when the rotation speed reaches a predetermined value. In the case where the speed command is deceleration, the output of the one-way command signal may be stopped when the speed command reaches “0”.

The encoder is not limited to a rotary encoder, but can be applied to a linear encoder in the same manner. The encoder is not limited to an optical encoder, but may be a magnetic encoder or the like. Further, the encoder can be applied to an incremental encoder that does not output a Z-phase signal. The displacement body is not limited to the electric motor 1, but may be any one that can be rotated or linearly displaced.

[0049]

Since the present invention is as described above,
The following effects are obtained. According to the abnormality detection device for the encoder of the present invention, the abnormality detection means determines the position data output means based on the A-phase and B-phase signals of the encoder while the control means outputs the one-way command signal. An abnormality detection signal is output when the count operation is switched between up and down indicated by the up / down signal, which is determined and output according to the displacement direction of the displacement body. Even if the Z-phase signal of the encoder is not used, it is possible to detect that there is an abnormality in the signal output pattern of the encoder, and it is possible to reliably detect the abnormality.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an electrical configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing an electrical configuration of an up / down signal generation circuit inside a counter.

FIG. 3 is a timing chart illustrating an operation of an up-down signal generation circuit.

FIG. 4 is a diagram showing a detailed electrical configuration of the abnormality detector;

FIG. 5 is a timing chart showing signal waveforms at various parts of the abnormality detector.

FIG. 6 is a timing chart showing a normal signal output pattern.

FIG. 7 is a timing chart showing a signal output pattern at the time of abnormality.

FIG. 8 is a timing chart for explaining an example of detecting an abnormality of a conventional encoder.

[Explanation of symbols]

1 is an electric motor (displacement element), 2 is an encoder, 2A and 2B are light receiving elements (A-phase and B-phase signal output means), 3 is an up / down counter (position data output means), 5 is a control device (control means), Reference numeral 6 denotes an abnormality detector (abnormality detection means).

Claims (1)

[Claims] An A-phase signal output means and a B-phase signal output means for outputting pulse signals having phases different from each other by 90 degrees as an A-phase signal and a B-phase signal with a linear displacement or a rotational displacement of a displacement body. In an apparatus for detecting an abnormality of an encoder, while outputting the displacement position data of the displacement body by counting up or down the A-phase and B-phase signals output by the A-phase and B-phase signal output means, Said A
Position data output for determining up / down of the count operation according to the displacement direction of the displacement body determined based on the phase and B phase signals, and outputting an up / down signal indicating the up / down of the count operation currently being performed. Means, and a control means for outputting a displacement command to the displacement body, and outputting a one-way command-in-progress signal when the displacement direction of the displacement command is continuously constant, the control means comprising: An abnormality detection unit that outputs an abnormality detection signal when the counting operation indicated by the up / down signal output by the position data output unit is switched while outputting the in-command signal. An abnormality detection device for an encoder.