JP2005017000A - Encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove noise signals by noise from the outside of a rectangular signal, outputted according to the displacement of a movable object. <P>SOLUTION: A noise signal eliminating apparatus comprises a potential measurement circuit for measuring the potential of a bi-phase rectangular wave signal; a time deciding circuit for deciding the time for maintaining a fixed potential; and a displacement deciding circuit for deciding failures in the displacement of potential. A potential measurement circuit detects, in which of the two potential the rectangular signal that is a binary signal, is located. The time deciding circuit outputs the two rectangular waves, when the potential after the change is maintained at least for a specified time, after the potential of the two rectangular waves has changed. When the potential after the change varies within the specified time, the two rectangular waves, where the change in the potential is eliminated, are outputted. The displacement deciding circuit removes the change in the potential and outputs the two rectangular waves, when the potential of the two rectangular waves changes simultaneously. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an encoder.
[0002]
[Prior art]
A rotary encoder is a device that is fixed to a rotating shaft of an actuator such as a motor and detects a displacement amount, and has recently been used in industrial robots and the like. An optical rotary encoder uses a rotating disk with minute slits, and when the rotating disk rotates, the light is repeatedly transmitted through the slit and shielded from light. The displacement is detected by detecting by. Two pseudo sine waves having a phase difference of 90 degrees are output from the light receiving element, amplified by an amplifier circuit, and then the two pseudo sine waves are converted into a high voltage state (high level) and a low voltage state ( Converted into a rectangular wave having two states (low level) and output from the encoder. The output of the encoder is input to a counting circuit such as a measuring device, and position information such as a motor is calculated.
[0003]
The rectangular wave signal output from the encoder may be displaced to another state (voltage) in the middle of the rectangular wave due to external disturbances such as noise. For example, it may be temporarily displaced to a low level in the middle of a high level state, or conversely, it may be temporarily displaced to a high level in the middle of a low level. In this case, since the counting circuit calculates the position information based on the signal in which the displacement due to the noise occurs, incorrect position information is calculated. In order to prevent such malfunction due to disturbance, an analog or digital low-pass filter or the like is used. This filter outputs a signal when the same potential is maintained for a predetermined time or longer.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2003-148997
[Problems to be solved by the invention]
However, when the current used for the motor or the like increases, the two rectangular waves may be displaced simultaneously due to noise caused by the current. A signal due to such noise cannot be removed by the above-described conventional low-pass filter, and there is a problem that a two-phase rectangular wave signal having a phase difference of 90 degrees cannot be output.
[0006]
It is an object of the present invention to remove a rectangular wave noise signal caused by external noise.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is an encoder that converts two pseudo sine wave signals having a predetermined phase difference output according to displacement of a movable object into two rectangular waves and outputs them. And a potential measuring means for measuring the potentials of the two rectangular waves, and a potential determining means for removing the potential change and outputting the two rectangular waves when the potentials of the two rectangular waves change simultaneously. There is provided an encoder characterized by comprising noise removing means.
[0008]
According to a second aspect of the present invention, in the encoder according to the first aspect, when the noise removing unit maintains the changed potential for a predetermined time or more after the potential of the rectangular wave changes, the two rectangular waves When the potential after the change is not maintained for the predetermined time or longer, the encoder further comprises time determining means for removing the potential change and outputting the rectangular wave.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an encoder according to the present invention will be described with reference to the drawings.
[0010]
FIG. 1 shows a block configuration diagram of an encoder and a counting circuit of a measuring instrument according to an embodiment of the present invention.
[0011]
Two rectangular waves having a phase difference of 90 degrees are output from the encoder 10, and the measuring device 20 that measures the displacement of the motor that has received the output from the encoder measures the displacement (rotation amount) of the motor based on this signal. Is calculated.
[0012]
First, the configuration of the encoder 10 will be described. The encoder 10 includes a light emitting element 11, a rotating disk 12, a light receiving element 13, an amplifier circuit 14, and a binarization circuit (comparator) 15. Light emitted from the light emitting element 11 such as an LED is illuminated onto the rotating disk 12 by an illumination optical system (not shown). A plurality of slits 12-a are formed around the periphery of the rotating disk 12, and the center of the rotating disk 12 is fixed to a rotating shaft of a motor (not shown) that measures displacement. The light from the light emitting element 11 that has passed through the slit 12-a of the rotating disk 12 is detected by the light receiving element 13 such as a silicon photodiode.
[0013]
When the rotating disk 12 rotates, the light emitted from the light emitting element 11 repeats a state of being transmitted through the slit and a state of being blocked at a portion where there is no slit, and the light transmitted through the slit is detected by the light receiving element 13. By repeating the state of receiving light and the state of not receiving light, the light receiving element 13 outputs a signal corresponding to the fluctuation of the intensity of the light, and this signal is called a pseudo sine wave signal.
[0014]
The light receiving element 13 includes a fixed plate on which a plurality of slits having a predetermined shape are formed and a plurality of photodiodes. The light receiving element 13 receives a first pseudo sine wave signal (A phase signal) and an A phase. A second pseudo sine wave signal (B phase signal) having a phase difference of 90 degrees from the signal and an origin signal (Z signal) are output.
[0015]
The A-phase signal and B-phase signal output from the light receiving element 13 are amplified by the amplifier circuit 14. The amplified A-phase signal SA and B-phase signal SB are input to a binarization circuit (comparator) 15 and a rectangular wave that displaces two voltage states of high level (H) and low level (L), A It is converted into a phase rectangular wave signal CA and a B phase rectangular wave signal CB, respectively. These two rectangular waves are input to a noise signal removal device 16 described later, and are output from the encoder 10 after the noise signal is removed. The two rectangular waves output from the encoder 10 are input to the counting circuit 21 of the counting device 20, and the displacement (rotation amount) of the motor position is calculated.
[0016]
FIG. 2A shows the waveforms of the A-phase signal SA and the B-phase signal SB, which are two pseudo sine wave signals output from the amplifier circuit 14, and FIG. 2B shows the two pseudo sine wave signals in binary form. The waveforms of the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB, which are rectangular waves converted by the conversion circuit 15, are shown. The vertical axis is a voltage value, and the horizontal axis is time. As shown in FIG. 2A, the A-phase pseudo sine wave signal, which is the A-phase signal SA, varies with time by a sin function. The B-phase pseudo sine wave signal, which is the B-phase signal SB, is shifted by a quarter cycle from the A-phase signal SA, that is, the phase is delayed by 90 degrees and similarly fluctuates by the sin function. In this way, the rotation direction of the motor when the phase of the B phase signal SB is delayed by 90 degrees with respect to the A phase signal SA is defined as a positive direction. When the motor rotates in the direction opposite to this direction, or when rotating in the negative direction, the phase of the B phase signal SB is 90 degrees earlier than that of the A phase signal SA. That is, the rotational direction of the motor can be detected by detecting the phase difference between the A phase signal SA and the B phase signal SB.
[0017]
This pseudo sine wave signal is converted into a rectangular wave shown in FIG. When the pseudo sine wave signal in FIG. 2A fluctuates at a voltage higher than 0V, the binarization circuit 15 converts the pseudo sine wave signal to a constant voltage value of high level H and fluctuates at a voltage of 0V or less. Is converted to a constant voltage value of low level L. The phase A signal SA shown in FIG. 2 (a) fluctuates in the positive voltage range from the time 0 until the ½ cycle elapses, and fluctuates in the negative voltage range from the ½ cycle to the elapse of one cycle. Yes. When this A-phase signal SA is converted by the binarization circuit 15, the voltage is changed from the high level H to the low level L during the 1/2 cycle with the constant voltage of the high level H from the time 0 to the 1/2 cycle. In addition, a constant voltage value of low level L is shown from 1/2 cycle to 1 cycle. Similarly, the pseudo sine wave signal of the B phase signal SB is also converted into the B phase binarized signal CB. That is, the high level H is maintained from the 1/4 cycle to the 3/4 cycle, and the low level L is maintained from the 3/4 cycle to the 5/4 cycle.
[0018]
Next, the noise signal removal device 16 will be described. The noise signal removal device 16 is composed of a logic circuit. FIG. 3 is a block diagram showing the circuit configuration of the noise signal removal circuit 16. The A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB, which are two-phase rectangular wave signals output from the binarization circuit 15, are first input to the potential measuring circuit 31 of the noise signal removing device 16. The potential measuring circuit 31 determines whether the potential of the two-phase rectangular wave signal is at the high level H or the low level L. After the potential is determined by the potential measurement circuit 31, the time determination circuit 32 determines whether the A-phase rectangular wave signal CA or the B-phase rectangular wave signal CB remains at the same potential for a predetermined time or more. The predetermined time is set in advance in consideration of the rotational speed of the motor. When the A-phase rectangular wave signal CA or the B-phase rectangular wave signal CB remains at the same potential for a predetermined time or more, the time determination circuit 32 outputs the potential to the displacement determination circuit 33. When the displacement is not limited to the same potential for a predetermined time after the displacement, a rectangular wave signal is output to the displacement determination circuit 33 assuming that there is no displacement.
[0019]
The displacement determination circuit 33 determines an abnormal displacement due to disturbance of the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB, and when the displacement is abnormal, removes the displacement and outputs a rectangular wave signal. The signal output from the displacement determination circuit 33 is input to the measuring device 20 and the displacement (rotation amount) is calculated by the counting circuit 21.
[0020]
A flow of processing for removing a noise signal performed by the noise signal removing device 16 will be described with reference to a flowchart shown in FIG. In step S11 of FIG. 4, the motor starts rotating and input of two rectangular wave signals (two-phase rectangular wave signals) is started (S12). In step S13, the potential measurement circuit 31 determines whether each signal of the two-phase rectangular wave signal is in the high level H or low level L state, and the time determination circuit 32 determines the high level H or low level. It is determined whether or not the state of any voltage at level L continues for a predetermined time or more. When the time determination circuit 32 determines that the constant voltage state continues continuously for a predetermined time or longer, the process proceeds to step S13. On the other hand, if the constant voltage state does not continue for a predetermined time or longer, the process does not proceed to the next step S15, and the noise signal that does not continue for the predetermined time or longer is removed in step S14.
[0021]
After removing the noise signal in step S14, step S13 for determining the state of the two-phase rectangular wave signal is performed again. That is, in step S13, only the signal in which the potential of either the high level H or the low level L continues for a predetermined time or more among the input two-phase rectangular wave signals proceeds to the next step S13, and the predetermined time A signal that does not maintain a constant potential is blocked in step S13, removed in step S14, and does not proceed to step S13.
[0022]
For example, the A-phase rectangular wave signal CA is displaced from the low level L to the high level H, and is temporarily displaced to the low level L due to a disturbance before it remains at the high level H for a predetermined time. In this case, if the determination is made in step S13, the A-phase binarized signal CA does not maintain the high level H voltage for a predetermined time, so this signal is removed as a noise signal in step S14 without proceeding to step S13. Is done. In this case, the A-phase rectangular wave signal CB is not displaced from the low level L to the high level H, and proceeds to step S15 as a signal maintaining the low level L.
[0023]
When the determination in step S13 is not performed, a noise signal due to this disturbance is output from the encoder 10, and the potential of the rectangular wave signal is shifted from the high level H to the low level L by the counting circuit 21, and further to the high level H. The amount of movement (rotation amount) is recognized as being displaced. Therefore, an erroneous movement amount (rotation amount) is calculated by a noise signal due to disturbance. In step S13, calculation of this erroneous movement amount (rotation amount) can be prevented.
[0024]
In step S15, the displacement determination circuit 33 determines whether or not the displacement of each potential of the two-phase rectangular wave signal is normal. Here, the displacement of the potential of the two-phase rectangular wave signal will be described with reference to the state transition diagram of FIG. As shown in FIG. 2B, the phase of the B-phase rectangular wave signal CB of the two-phase rectangular wave signal is delayed by 90 degrees with respect to the A-phase rectangular wave signal CA when the motor rotates in the positive direction. Here, the potentials of the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB are expressed as (the level of the B-phase rectangular wave signal and the level of the A-phase rectangular wave signal). The high level H is 1 and the low level L is 0.
[0025]
In the state 51 before the motor starts rotating, the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB are at the low level L (the state 51 is represented by (00), and so on). When the motor starts to rotate, a pseudo sine wave signal is generated. First, the A-phase rectangular wave signal CA is shifted from the low level L to the high level H to enter the state 52 (01). Subsequently, with a 1/4 cycle delay, the B-phase rectangular wave signal CB is displaced from the low level L to the high level H, and enters the state 53 (11). When a further 1/4 cycle elapses, the A-phase rectangular wave signal CA is shifted from the high level H to the low level L to enter the state 54 (10), and when the 1/4 cycle elapses, the B-phase rectangular wave signal CB becomes the high level. Displacement from H to low level L returns to state 51 (0 0).
[0026]
In such a normal operation, the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB are displaced independently at a specific time, and both are not displaced simultaneously. That is, the displacement from state 51 (0 0) to state 53 (1 1), the displacement from state 53 (11) to state 51 (0 0), the displacement from state 52 (0 1) to state 54 (10), The displacement from the state 54 (10) to the state 52 (01) is an abnormal displacement that does not occur in a normal state. Such simultaneous displacement of the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB is a noise signal caused by a disturbance. In step S15, the displacement determination circuit 33 determines that an abnormal displacement in which the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB are simultaneously displaced is abnormal, and determines that other displacements are normal. .
[0027]
In step S15, the displacement from state 51 (0 0) to state 53 (1 1), displacement from state 53 (1 1) to state 51 (0 0), state 52 with respect to the signal that has passed step S12. In the case of a displacement from (0 1) to state 54 (1 0) and a displacement from state 54 (1 0) to state 52 (0 1), it is determined that there is an abnormality, and this displacement is blocked. That is, if it is determined in step S15 that the displacement is abnormal, the displacement (simultaneous displacement) is removed in step S16, and then the determination in step S15 is performed again.
[0028]
FIG. 5A shows examples of waveforms of the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB when simultaneous changes occur. In this example, the state 51 (0 0) is changed to the state 53 (1 1), the potential is maintained for a predetermined time, and then the state 53 (1 1) is changed to the state 51 (0 0). In this case, in step S13, since the potential is maintained at the same potential for a predetermined time or more, it is determined to be normal, and the process proceeds to step S15. In step S15, this simultaneous displacement is determined to be abnormal.
[0029]
If it is determined that there is an abnormality, this displacement (noise signal) is removed in step S16. That is, the signal is converted into a signal in which the state 51 (0 0) continues. FIG. 5B shows the A-phase rectangular wave signal CA and the B-phase rectangular wave signal CB after the noise signal is removed. The signal displaced from the state 51 (0 0) to the state 53 (1 1) by the disturbance and then displaced from the state 53 (1 1) to the state 51 (0 0) is removed, and the state 51 (0 0) is changed to the state 51 (0 0). It has been converted into the following signal.
[0030]
To summarize the processing in the noise signal removal device 16, the two-phase rectangular wave signal input to the noise signal removal device 16 is removed from the displacement that occurred before a predetermined time or more has passed in step S <b> 13. That is, a noise signal that is displaced due to a disturbance and that is immediately displaced to the original potential is removed. Next, in step S13, an abnormality in which the potentials of the two rectangular wave signals are simultaneously displaced due to a disturbance can be detected and removed. Such a noise signal cannot be removed by a noise removal circuit using a conventional low-pass filter.
[0031]
The output signal from the noise removing device 16 from which the noise signal due to such disturbance has been removed is input to the counting circuit 21 of the measuring device 20, and the displacement (rotation amount) of the motor is calculated.
[0032]
If the encoder 10 of this embodiment is used, a noise signal of a two-phase rectangular wave signal due to disturbance such as electrical noise can be removed, and an erroneous signal is not transmitted to the counting circuit 21. Since it is possible to prevent an erroneous movement amount (rotation amount) from being calculated, the accuracy of the encoder can be improved.
[0033]
In the present embodiment, a logic circuit is used as the noise signal removing device 16, but the process of the flowchart shown in FIG. 4 may be executed by software using a computer.
[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an encoder capable of removing a rectangular wave noise signal due to external noise.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram of an encoder and a measuring device according to an embodiment.
FIG. 2A is a diagram showing a time change of a pseudo sine wave signal;
(B) The figure which shows the time change of a rectangular wave signal.
FIG. 3 is a block configuration diagram of a circuit of a noise removing device.
FIG. 4 is a flowchart showing a process flow of the noise removal apparatus.
FIG. 5 is a state transition diagram of a two-phase rectangular wave. FIG. 6A is a diagram showing a waveform when two-phase rectangular waves are changed simultaneously.
(B) The figure which shows the waveform after removing the noise signal from which the two-phase rectangular wave changed simultaneously.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Encoder 11 Light emitting element 12 Rotating disk 13 Light receiving element 14 Amplifying circuit 15 Binarization circuit 16 Noise signal removal apparatus 20 Counting device 21 Counting circuit 31 Potential measurement circuit 32 Time determination circuit 33 Displacement determination circuit

Claims (2)

In an encoder that converts two pseudo sine wave signals having a predetermined phase difference that are output according to the displacement of a movable object into two rectangular waves and outputs them,
A potential measuring means for measuring the potentials of the two rectangular waves; and a potential determining means for removing the change in potential and outputting the two rectangular waves when the potentials of the two rectangular waves change simultaneously. An encoder characterized by comprising noise removing means. The noise removing means is
When the changed potential continues for a predetermined time or longer after the rectangular wave potential changes, the two rectangular waves are output, and when the changed potential is not maintained for the predetermined time or longer, the potential change is The encoder according to claim 1, further comprising time determination means for removing and outputting the rectangular wave.

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