JP2006284520A - System for monitoring encoder and encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prompt replacement of an encoder, prior to resulting in incapable measurement by predicting abnormality due to degradation of the encoder. <P>SOLUTION: The encoder 50 includes a measuring section 10 having a light-emitting device 2, a rotating disk 1 with a pattern composed of a light-transmitting section and a light-shielding section, and a light-receiving device 3 for receiving light from the light-emitting device 2 via the rotary disk 1; and is configured so as to output a light-receiving signal, in response to the movement position of the rotating disk 1. The encoder 50 includes a time series monitoring circuit 63 for calculating the moving-average value of light-receiving signals, a current monitor circuit 61 for monitoring whether the moving average value becomes lower than the determination value that has been set for the signal level of the light-receiving signal output, when the measuring section 10 results in incapable of measurement, by lowering the light-receiving intensity of the light-receiving device 3, and a replacement alarm generating circuit 66 for providing a notice, when the average value becomes lower than the determination value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an encoder and an encoder monitoring system.

  A driving device that drives a driven body by a motor has been widely used for controlling electronic devices and industrial robots in various fields. For example, in an industrial robot, the arm is bent and extended and swiveled. In an optical apparatus such as a camera, the present invention is also applied to an automatic focus adjustment device that moves and stops a photographing lens driven by a motor to an in-focus position. In such a drive device, a rotary encoder is often used as a position sensor for detecting a movement amount and a movement speed of a robot arm and a lens necessary for control.

A rotary encoder is a device that is fixed to a rotating shaft of an actuator such as a motor and detects its rotational position. There are optical and magnetic types, and an optical rotary encoder is also described in Patent Document 1, for example. As shown, a rotating disk having minute slits formed at equal intervals and attached to a motor is used. A light emitting element (LED) as a light source is disposed on one side of the rotating disk, and a light receiving element (photodiode) is disposed on the other side so as to face the light emitting element, and light emitted from the light emitting element is received by the light receiving element. Thus, an analog signal having an output level corresponding to the amount of received light can be output. In the optical rotary encoder configured as described above, when the rotating disk rotates with the rotation of the motor, the light reaching the light receiving element from the light emitting element through the slit of the rotating disk is periodically blocked, and the change of this light is detected. The displacement can be detected by detecting with the light receiving element. At this time, for example, two pseudo sine waves having a phase difference of 90 degrees are output from the light receiving element, and after being amplified by the amplifier circuit, the two pseudo sine waves are in a high voltage state (by a comparator in the A / D conversion circuit). It is converted into a digital signal (pulse signal) that takes two states, a high voltage level and a low voltage level (low level). This pulse signal is input to a counting circuit such as a measuring instrument so that motor position information is calculated.
Japanese Patent Application Laid-Open No. 2000-234942

  By the way, in the optical encoder as described above, when the light emitting element or the light receiving element deteriorates over time, for example, when the amount of light emitted from the light emitting element decreases, the measurement accuracy of the displacement of the measurement object is accordingly accompanied. However, in the conventional encoder, the encoder has been used at the time when the deterioration has progressed to some extent and the reliability of the measurement accuracy is lost, or until the position information of the measurement object cannot be detected. Then, when such detection by the encoder becomes impossible, an alarm for prompting replacement of the encoder is output, and then the drive device equipped with the encoder is stopped one by one. When light-emitting elements and light-receiving elements deteriorate over time, there are variations in the period until they occur, so it is often impossible to predict when the drive will stop, making it difficult to replace encoders. There is a problem that it tends to be inefficient.

  In view of the problems as described above, an object of the present invention is to provide an encoder and an encoder monitoring system that can predict an abnormality due to deterioration of the encoder.

  In order to solve the above problems, an encoder according to the present invention receives a light source, a pattern composed of a light transmission part and a light shielding part, and light from the light source through the pattern, and outputs a signal corresponding to the movement position of the pattern. And a monitoring means for monitoring whether or not the signal level is lower than a determination value set to a value higher than the signal level at which the received light intensity of the light receiving unit decreases and the movement of the pattern becomes unmeasurable Warning means for giving a warning when the signal falls below the determination value.

  Further, in the encoder having the above configuration, the encoder has a registration means for registering a periodic inspection interval at which the encoder for which the warning has been issued is replaced, and the determination value cannot be measured after the warning is given by the warning means. It is preferable that the period until the signal level is reduced to be equal to or longer than the periodic inspection interval is set.

  Furthermore, it is preferable that the encoder having the above-described configuration has a calculating means for calculating a moving average value of the signal, and the monitoring means monitors whether or not the moving average value is lower than the determination value.

  In order to solve the above problems, an encoder according to the present invention receives a light source, a pattern including a light transmission part and a light shielding part, and light from the light source through the pattern, and a signal corresponding to the movement position of the pattern. A light receiving unit that outputs a light source, a light source control device that changes the current value flowing through the light source so that the amount of light received by the light receiving unit is constant, and the current value that flows through the light source makes it impossible to measure the light amount of the light source when the pattern moves Monitoring means that monitors whether the current value that is smaller than the current value that results in a light quantity that is higher than the judgment value set, and a warning that warns when the current value flowing through the light source exceeds the judgment value Means.

  Further, in the encoder having the above configuration, the encoder has a registration means for registering a periodic inspection interval at which the encoder for which the warning has been issued is replaced, and the determination value cannot be measured after the warning is given by the warning means. It is preferable that the period until the current value rises to be equal to or longer than the periodic inspection interval is set.

  In order to solve the above problems, an encoder monitoring system according to the present invention receives a light source, a pattern composed of a light transmission part and a light shielding part, and light from the light source through the pattern, and responds to the movement position of the pattern. An encoder having a light receiving unit that outputs a received signal, a calculation means for calculating a moving average value of the signal based on the signal from the encoder, and a signal that makes it impossible to measure the movement of the pattern due to a decrease in the light receiving intensity of the light receiving unit Monitoring means for monitoring whether or not the signal level is lower than a determination value set to a value higher than the level; and warning means for outputting a warning when the moving average value is lower than the determination value.

  According to the encoder and the encoder monitoring system according to the present invention, it is possible to predict an abnormality due to deterioration of the encoder.

  Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. FIG. 1 shows an encoder 50 according to the present invention and a controller 100 that drives and controls a motor (AC servo motor) equipped with the encoder 50. The encoder 50 detects the rotational position of a motor (not shown) equipped with the encoder 50 using an optical encoder 50 composed of the light emitting element 2 and the like, and is roughly divided into a measuring unit 10 and a data processing unit 5. The

  The measurement unit 10 generates a pseudo sine wave signal for detecting the displacement of the motor. On the other hand, the data processing unit 5 detects the rotational position of the motor using the pseudo sine wave signal generated by the measurement unit 10 and determines whether the pseudo sine wave signal is abnormal. Further, the external controller 100 as an external device is capable of half-duplex serial communication with the encoder 50, and the displacement detection value from the encoder 50 and the presence or absence of signal abnormality are transmitted from the data processing unit 5 to the external controller 100. Is possible. The controller 100 drives and controls the motor according to the detected value of the motor displacement by the encoder 50, and takes a predetermined measure when the encoder 50 determines that the pseudo sine wave signal is abnormal.

  The measurement unit 10 includes a light emitting element 2 (light source) such as an LED, a rotating disk 1 (scale), a light receiving element 3 such as a silicon photodiode, an amplifier circuit 4 and an alarm circuit 6. A plurality of slits (patterns) are formed in the circumferential direction of the rotating disk 1 at predetermined intervals, and the center of the rotating disk 1 is fixed to a rotating shaft of a motor (not shown) that is a target for measuring displacement. .

  Further, the light emitting element 2 and the light receiving element 3 are respectively disposed so as to face each other with the rotating disk 1 provided therebetween. The light emitted from the light emitting element 2 is irradiated to the rotating disk 1 by an illumination optical system (not shown), and the light transmitted through the slit of the rotating disk 1 is detected by the light receiving element 3. The light receiving element 3 outputs a detection signal according to the intensity of the received light.

  The alarm circuit 6 has a current monitor circuit 61 therein, and, as will be described later, by monitoring the output signal from the light receiving element 3 (the amount of light from the light emitting element 2), the deterioration of the light emitting element 2 over time is prevented. Even if it occurs, the current flowing toward the light emitting element 2 is adjusted in order to suppress a decrease in the output signal from the light receiving element 3.

  In the data processing unit 5, the displacement (rotational position) of the motor is calculated based on the digital data after the A-phase and B-phase analog signal conversion of the absolute pattern or incremental pattern, and the calculated data is half-duplex as position data. The data is transmitted to the external controller 100 by serial communication. In the controller 100, position displacement of an actuator or the like driven by the motor is calculated based on the calculated rotation position of the motor, and the motor is controlled so that the actuator or the like is displaced to a desired position.

  Here, with reference to FIG. 2, an alarm circuit 6 that monitors and adjusts the current flowing through the light emitting element 2 of the encoder 50 according to the present invention, detects the aging deterioration of the light emitting element 2 and notifies this as a warning. Will be described.

  The alarm circuit 6 includes a current monitor circuit 61, a first comparator 62, a time series monitor circuit 63, a second comparator 64, an alarm generation circuit 65, and a replacement alarm generation circuit 66.

  The current monitor circuit 61 constantly monitors the current flowing through the light emitting element 2 and controls the current flowing through the light emitting element 2 so as to cancel the decrease in the output from the light receiving element 3 due to the aging that occurs in the light emitting element 2. It is. Specifically, the light flows to the light emitting element 2 in accordance with an amplified signal obtained by amplifying output signals (A phase signal and B phase signal) output from the plurality of detection elements of the light receiving element 3 with the phases shifted from each other by 90 degrees. By controlling the current, control is performed so that the amount of light received by the light receiving element 3 does not decrease (automatic light control).

  FIG. 3 shows how the current monitor circuit 61 controls the current value in the light emitting element 2. The horizontal axis in FIG. 3 is time, and the vertical axis is the value of current flowing through the light source (light emitting element 2). As shown in FIG. 3, since the current is controlled so as to eliminate the influence of the deterioration of the light emitting element 2 that progresses with time, the current flowing through the light emitting element 2 increases with time.

  Lines L2 and L3 in FIG. 3 are cases where the progress of deterioration of the light emitting element 2 is relatively slow, and the current value is controlled to increase gradually. On the other hand, although the progress of the deterioration is slow at the initial stage, when the deterioration suddenly progresses from a certain point in time, the current value increases gradually as shown by the line L1, but after the point P, the deterioration continues. The time increase rate of the current value increases with rapid progress.

  The threshold level Th1 in FIG. 3 is set to generate an alarm for warning the deterioration of the light emitting element 2, and the value cannot be made constant even if the current value is increased further. Is the current value of the light-emitting element 2 in a state where measurement is impossible and in which the measurement accuracy is not reliable. The first comparator 62 (see FIG. 4) of the alarm circuit 6 constantly monitors whether or not the current value of the light emitting element 2 exceeds the threshold level Th1, and if this value exceeds the threshold level Th1, an alarm is generated. This is output to the generation circuit 65, and the alarm generation circuit 65 generates a warning that the current value has exceeded the threshold level Th1.

  When such an alarm is issued by the alarm generation circuit 65, the warning information is once input to the data processing unit 5 and then transmitted to the controller 100 by serial communication, and the motor drive control by the controller 100 is stopped. To do. Further, a notification that a predetermined warning flag is set is issued in the controller 100, and an operator who recognizes the notification replaces the encoder 50 with one that has not deteriorated, so that the drive control of the motor can be performed again.

  Incidentally, the deterioration pattern as indicated by the line L1 in FIG. 3 is that the current value of the light-emitting element 2 suddenly increases (is controlled to increase) at a certain time point P, and therefore the current value is the threshold level Th1. It is difficult to predict in advance. On the other hand, in the case of the degradation pattern as shown by the line L2 or the line L3 in FIG. 3, it is possible to predict that the current value will eventually reach the threshold level Th1.

  For this reason, in the present invention, measurement by the encoder 50 is performed by newly setting the threshold level Th2 at a current value lower than the threshold level Th1 at which measurement by the encoder 50 becomes impossible and motor drive control by the controller 100 stops. It is possible to predict in advance that the impossibility is approaching and to prompt the user to replace the encoder 50 before the encoder 50 stops.

  Further, the threshold level Th2 can be arbitrarily set. However, in the case of the deterioration pattern as shown by the line L2, the threshold level Th2 reaches the threshold level Th1 after the threshold level Th2 is reached and the measurement by the encoder becomes impossible. In the meantime, it is preferable to set the encoder to a level at which it is possible to receive a periodic inspection for periodically checking and replacing an encoder whose performance has deteriorated (warning is issued).

  In this case, the alarm circuit 6 is connected to an input device 67 for registering a period (interval) of periodic inspection. For example, the threshold level Th2 is preferably set to a level that takes about 2 to 4 weeks to reach the threshold level Th1. Assuming that the period of the periodic inspection is 3 weeks, the current value level obtained by subtracting the current value increasing in 3 weeks from the threshold level Th1 after calculating the slope of the line L2 and increasing in 3 weeks is the threshold level Th2. Set as If the time to reach the threshold level Th1 from the threshold level Th2 is the same as or longer than the periodic inspection, the threshold level Th2 is reached and a warning is issued. Then, the periodic inspection is performed within 3 weeks, and measurement is impossible. It becomes possible to replace the encoder before reaching the threshold level Th1.

  Next, FIG. 4 shows a change in the amount of light when the current value flowing through the light emitting element 2 is constant. Also in FIG. 4, similarly to FIG. 3, the threshold level Th <b> 1 of the light amount at which measurement by the encoder 50 is impossible and the threshold level Th <b> 2 indicating that the encoder 50 cannot measure at a higher light amount are approaching. .

  The line L4 in FIG. 4 is actual light amount data, and the amount of light received varies depending on the rotational position of the rotary disk 1. Therefore, the value of the line L4 changes so as to decrease as time passes while fluctuating. Due to such a behavior of the light amount, the light amount may decrease until reaching the threshold level Th2 at an earlier time point than predicted. In such a case, when it is determined whether or not the light quantity has reached the threshold level Th2 based on the actual light quantity data, the threshold level Th2 is reached at the point Q when the actual data drops until it exceeds the threshold level Th2 for the first time. It is judged that

  In order to avoid this and reach the threshold level Th2 when the amount of light is predicted, in the present invention, the current value output from the current monitor circuit 61 (that is, the amount of light received by the light receiving element 3) is A moving average of the amount of light that is once input to the time series monitor circuit 63 (see FIG. 4) in the alarm circuit 6 and input to the time series monitor circuit 63 at a predetermined time (preset in the time series monitor circuit 63). Is calculated by the time series monitor circuit 63.

  The moving average of the light amount calculated by the time series monitor circuit 63 in this way is indicated by a line L5 in FIG. As shown in the figure, the line L5 changes so as not to fluctuate, and this line L5 decreases until reaching the threshold level Th2 at the point R, which is a time later than the point Q.

  The second comparator 64 (see FIG. 2) of the alarm circuit 6 constantly monitors whether or not the amount of light received by the light receiving element 3 has fallen below the threshold level Th2, and when this value falls below the threshold level Th2. The fact that the threshold level Th2 has been reached is output to the replacement alarm generation circuit 66, and the replacement alarm generation circuit 66 generates a warning prompting the replacement of the encoder 50.

  The threshold level Th2 can be arbitrarily set as in the case of the current value. However, the threshold level Th2 is, as in the case of the current value, until reaching the threshold level Th1 at which the encoder cannot measure. It is preferable that the encoder whose performance is deteriorated (warning is issued) is set to a level at which periodic inspection can be performed.

  When such an alarm is issued by the replacement alarm generation circuit 66, the warning information is once input to the data processing unit 5 and then transmitted to the controller 100 by serial communication, and a warning flag is set in the controller 100. Then, a predetermined notification that prompts replacement of the encoder 50 is performed. As a specific notification method, a method for displaying the encoder 50 that needs to be replaced on the monitor screen of a personal computer that constitutes the controller 100 so that the encoder 50 that needs to be replaced can be seen, and the personal computer so that it can recognize which encoder 50 needs to be replaced. There is a way to emit a warning sound from a computer. Then, the operator who performs the maintenance of the encoder replaces the encoder that has been informed of the replacement by the above method among the plurality of encoders, and the measurement by the encoder becomes possible again.

  Although the preferred embodiments of the present invention have been described so far, the scope of the present invention is not limited to the above-described embodiments. For example, in the above embodiment, the cause of the necessity of replacement of the encoder is that the light emitting element 2 is deteriorated over time. This is monitored, but the deterioration of the light receiving element 3 is monitored. 2 and the light receiving element 3 may be monitored for contamination of the lens disposed between them.

  Further, the alarm circuit 6 constituting the current monitor circuit 61, the time series monitor circuit 63 and the like may be provided in the controller 100 capable of serial communication with the encoder 50 instead of the encoder 50. With this configuration, the controller 100 always monitors whether or not the light reception signal (the amount of light received by the light receiving element 3) transmitted via the data processing unit 5 exceeds the threshold level Th2, and the amount of light is the threshold level Th2. Can be notified on the monitor screen of the personal computer when the encoder 50 is reached. That is, the alarm circuit 6 including the current monitor circuit 61 and the like is not necessarily provided in the encoder 50 assembly.

  In the above embodiments, a rotary encoder capable of detecting the rotation amount of an actuator such as a motor has been described as an example. However, an abnormality in a measurement system due to deterioration over time is applied to an optical linear encoder. Also good.

It is a block diagram which shows the structure of the encoder which concerns on this invention. It is a block diagram which shows the alarm circuit provided in the said encoder. It is a figure which shows the time change of the electric current value which flows into the light emitting element controlled by the current monitor circuit provided in the said alarm circuit. It is a figure which shows the time change of the magnitude | size of the light reception signal output from a light receiving element, ie, light quantity.

Explanation of symbols

1 Rotating disc (pattern)
2 Light emitting element (light source)
3 Light receiving element (light receiving part)
4 Amplifying circuit 5 Data processing unit 5a A / D converter (signal converting means)
6 Alarm circuit 10 Measuring unit 50 Encoder 61 Current monitor circuit (light source control device)
62 1st comparator 63 Time series monitor circuit (calculation means)
64 Second comparator (monitoring means)
65 Alarm generation circuit 66 Replacement alarm generation circuit (warning means)
67 Input device (registration means)
100 Controller Th1 Threshold level (alarm generated)
Th2 threshold level (exchange alarm occurred)

Claims (6)

A light source;
A pattern composed of a light transmitting portion and a light shielding portion;
A light receiving unit that receives light from the light source through the pattern and outputs a signal according to a movement position of the pattern;
Monitoring means for monitoring whether or not the signal level is lower than a determination value set to a value higher than a signal level at which the received light intensity of the light receiving unit decreases and the movement of the pattern becomes unmeasurable;
An encoder comprising warning means for giving a warning when the signal falls below the determination value. The encoder has a registration means for registering an interval of a periodic inspection in which the encoder for which the warning has been issued is replaced;
The determination value is set to a level in which a period from when a warning is given by the warning means until the signal level is lowered to the signal level at which measurement is impossible is equal to or longer than the interval of the regular inspection. The encoder according to claim 1. Computation means for computing a moving average value of the signal,
The encoder according to claim 1, wherein the monitoring unit monitors whether or not the moving average value has decreased below the determination value. A light source;
A pattern composed of a light transmitting portion and a light shielding portion;
A light receiving unit that receives light from the light source through the pattern and outputs a signal according to a movement position of the pattern;
A light source control device that changes a current value flowing through the light source so that the amount of light received by the light receiving unit is constant;
Monitoring that monitors whether the value of the current flowing through the light source has risen above a determination value set to a current value smaller than the current value at which the amount of light of the light source becomes a light amount at which movement of the pattern cannot be measured Means,
An encoder comprising warning means for giving a warning when a current value flowing through the light source becomes equal to or greater than the determination value. The encoder has a registration means for registering an interval of a periodic inspection in which the encoder for which the warning has been issued is replaced;
The determination value is set to a current value in which a period from when a warning is given by the warning means to when the current value becomes unmeasurable is set to be equal to or longer than the periodic inspection interval. The encoder according to claim 4, characterized in that: An encoder having a light source, a pattern composed of a light transmission part and a light shielding part, and a light receiving part that receives light from the light source through the pattern and outputs a signal corresponding to the movement position of the pattern;
A computing means for computing a moving average value of the signal based on a signal from the encoder;
Monitoring means for monitoring whether or not the signal level is lower than a determination value set to a value higher than a signal level at which the received light intensity of the light receiving unit decreases and the movement of the pattern becomes unmeasurable;
An encoder monitoring system comprising: warning means for outputting a warning when the moving average value is lower than the determination value.

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