JPH08178693A - Encoder diagnostic device - Google Patents

Abstract

PURPOSE: To provide an encoder diagnostic device in which an absolute value encoder or incremental encoder can be easily diagnosed. CONSTITUTION: The absolute value data transmitted from an absolute value encoder 12 when a power source is OFF is stored in a nonvolatile memory 25. When the power source is then ON, the above absolute value data stored in the nonvolatile memory 25 is compared with the absolute valve data transmitted from the absolute value encoder at that time, and when the difference is out of a predetermined allowable range, an alarm is displayed on an indicator 26. The data stored in the nonvolatile memory 25 may be the count value stored in an INC counter 23. In operation, the absolute value data provided from the absolute value encoder 12 is compared with the count value of the INC counter 23 when the rotating speed of a motor 6 is less than a fixed value, and the alarm is displayed on the indicator 26 when the different is out of the predetermined allowable range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for an encoder provided in a moving part of a machine tool, for example, a mechanical part that moves at high speed such as a grindstone in a grinder.

[0002]

2. Description of the Related Art In a mechanism such as a grinding wheel head of a grinder that is controlled to move in one direction at high speed by using a servomotor, an encoder is attached to a motor or a rotary shaft rotated by the motor, and a servo system is based on the output of the encoder. The position is controlled by.

Usually, in such a device, when the power is turned on, a moving part such as a grinding wheel head to be controlled to move is moved to a predetermined origin position, and the moving part such as the grinding wheel position is position-controlled based on the origin position. To do.

Conventionally, for the above control, an incremental encoder that outputs an increase / decrease pulse according to the rotation is attached to a rotary shaft that is rotated by a motor, and a counter that counts the output pulse is provided to cut the power when the power is turned on. In the initial state of starting machining, the moving part such as the grinding stone head is returned to the origin position and the counter is reset, or the initial value is preset, or the value of the counter is set by the mechanical limit switch. A so-called origin return (ZRN) operation is performed to make the position correspond to the position of a moving part such as a grindstone.

However, in the above-mentioned configuration, when the power of the apparatus is turned on, an operation (ZRN operation) of resetting the counter by using the mechanical limit switch to return the moving portion such as the grindstone to the origin position is necessary. There are problems that it takes a long time to start up when the power is turned on and that the mechanical limit switch is easily damaged. Therefore, in addition to the incremental encoder and the counter, an absolute value encoder (absolute encoder) that directly outputs the absolute value with respect to the origin of the moving part such as a grindstone is provided, and by taking in the output of this absolute value encoder when the power is turned on, An apparatus has been proposed in which the mechanical limit switch is removed and the ZRN operation is omitted.

[0006]

However, when the incremental encoder and the absolute value encoder are used together as described above, the value sent from the absolute value encoder when the power is turned on is correct in order to perform the subsequent control. However, there is a problem that this absolute value encoder malfunctions if the adjustment is mechanically or electrically incorrect. In particular, the machine tool is often turned off at the end of the day and turned on the next morning, but the machine tool and encoder are adjusted during this power-off period, so that the rotary shaft and encoder There was a case that the reference value did not match due to the displacement of the mounting position of the above, and grinding failure occurred.

An object of the present invention is to provide an encoder diagnostic device which can easily diagnose the absolute value encoder and the incremental encoder.

[0008]

According to the present invention, there is provided an incremental encoder which is connected to a rotary shaft of a drive motor for driving a moving part of a machine tool and which outputs an incremental pulse according to the movement of the moving part, and the drive. In a diagnostic device for an encoder unit configured with an absolute value encoder that is connected to the same rotary shaft as a motor and outputs absolute value data indicating the absolute position of the moving unit, serial communication is performed from the absolute value encoder when the power is off. A non-volatile memory that stores the absolute value data of the moving unit sent via a path when the power is turned off, and the absolute value data sent from the absolute value encoder when the power is turned on and the non-volatile memory Means for making an alarm notification when the difference is not within a predetermined allowable range. That. A counter that counts the output pulses of the incremental encoder; a non-volatile memory that stores the count value of the counter when the power is off;
Means for comparing the absolute value data sent from the absolute value encoder when the power is turned on with the position data stored in the non-volatile memory, and issuing an alarm when the difference is not within a predetermined allowable range. It is characterized by comprising and.

Further, the counter for counting the output pulses of the incremental encoder is compared with the count value of the counter and the absolute value data sent from the absolute encoder when the moving speed of the moving part is below a certain level. Then
Means for giving an alarm when the difference is not within a predetermined allowable range.

[0010]

In the present invention, when the power is turned on, the value of the absolute encoder is taken in to detect the current position of the moving part. At this time, since the current position of the machine can be known by knowing the value of the absolute value encoder, the ZRN operation of resetting the counter connected to the incremental encoder by returning the moving unit to the origin is unnecessary. Therefore,
Immediately after the power is turned on, it will be in a movable state immediately. Incidentally, a counter that counts the output pulse thereof is usually connected to the incremental encoder. Since the count value of this counter corresponds to the position of the moving part, the value of the absolute encoder read when the power is turned on is set in this counter. In the operating state, the servo system controls the movement of the moving unit based on the value of the counter, that is, the output pulse of the incremental encoder. The output of the absolute value encoder is the same as the value of the above counter, but the output of the absolute value encoder is not the increase / decrease pulse like the incremental encoder but the position data itself. Take in through. Therefore, when the moving unit moves at high speed, it takes too much time to capture the position data of the high-speed moving unit through the communication port, and it is not possible to deal with it. Therefore, when the machine tool enters the operating state, position control is performed based on the output pulse of this incremental encoder.

According to the present invention, when the power is turned off, the absolute value data of the moving part sent from the absolute value encoder via the serial communication path is stored in the non-volatile memory, and is stored at the next power on. The absolute value data stored in the non-volatile memory is compared with the absolute value data sent from the absolute value encoder at that time. Then, when the difference is not within a predetermined allowable range, an alarm is issued. Therefore, if there is any failure in the absolute encoder between the time the power is turned off and the next time it is turned on, for example, if the absolute encoder is readjusted or the mounting position is changed due to external force, this By the operation, it can be known that the output of the absolute encoder when the power is turned on is not correct.

Further, in the present invention, since two encoders of the incremental encoder and the absolute value encoder are used, the value of the counter for storing the count value of the incremental encoder and the output value of the absolute value encoder are used. It is also possible to diagnose the encoder by comparing. That is, in the present invention, the count value of the counter that counts the output pulses of the incremental encoder is stored in the nonvolatile memory when the power is turned off, and the value of the nonvolatile memory and the absolute value encoder are sent when the power is turned on next time. The received value is compared, and when the value is not within the predetermined allowable range, an alarm is notified. In this operation, if one of the two encoders is misaligned when the power is off, it is possible to know that the adjustment is incorrect when the power is next turned on.

Further, according to the present invention, both encoders can be diagnosed while the machine tool is in operation. As described above, since it takes time to fetch the position information from the absolute encoder, the position of the moving unit cannot be controlled by the output of the absolute encoder when the moving unit is operating at high speed. When the moving unit is stopped or operating at a low speed, the value of the absolute encoder sent via the communication port sufficiently follows the change in the position of the moving unit. Therefore, when such a state is detected, the output of the absolute value encoder is compared with the value of the counter connected to the incremental encoder to check whether any of the encoders is in an abnormal state.

[0014]

1 is a plan view of a main part of a grinding machine to which an encoder diagnostic apparatus according to an embodiment of the present invention is applied.

On the bed 1, a grindstone 2, a spindle head 3, etc. are arranged. On the grindstone 2, a grinding wheel 4 and this grinding wheel 4 are arranged.
Is provided with a motor 5 for driving, and a servo motor 6 for controlling the movement of the grindstone base 2 in the X-axis direction (vertical direction in the drawing). Further, a spindle motor 7 that drives a spindle 8 is provided on the spindle stock 3, and a work 9 is attached to the spindle 8 via a dresser. Further, a servo motor 10 is provided to control the movement of the headstock 3 in the Z-axis direction (left-right direction in the drawing).

In the above structure, incremental encoders 11 and 13 and absolute value encoders 12 and 14 are further attached to the rotary shafts of the servomotors 6 and 10, respectively. The drive signal lines of the servomotors 6 and 10 and the signal lines of the encoders 11 to 14 are guided to a numerical control device (not shown), and the numerical control device controls the servomotors 6 and 10 based on the information from these encoders. .

FIG. 2 shows the structure of the drive control unit of the servomotor 6 shown in FIG. The drive control unit is provided in the numerical control device.

The incremental encoder 11 connected to the rotating shaft of the motor 6 is provided with a known disk including a disk having equally divided marks or slits formed around it and an optical sensor or a magnetic sensor arranged so as to face the disk. It is composed of an encoder and generates one pulse each time the rotating shaft rotates by a certain angle. In the present embodiment, a motor 6 capable of rotating in the forward and reverse directions is used, and the incremental encoder 11 uses the output encoder 4 in order to know the rotation direction of the motor 6.
Two sensors arranged with their phases shifted by one-half cycle and output terminals of each sensor are provided. The rotation direction is this 2
It can be detected by a known method from the difference in the timing of the output pulses of the two output terminals. The rotation speed can be calculated from the pulse period. On the other hand, the absolute value encoder 12 itself stores the rotation angle as well as the rotation angle of the rotating shaft of the motor 6, and can externally directly output the position data with respect to the reference value as absolute value data.

The output terminal of the incremental encoder 11 is connected to the pulse input port 21 in the drive control unit 20, and the output terminal of the absolute value encoder 12 is a serial communication line in the serial communication port 2 in the control unit 20.
Connected to 2. A detection pulse is directly input from the incremental encoder 11 to the pulse input port 21, but the absolute value encoder 12 sends absolute value position data to the serial communication port 22 via a serial communication line. Therefore, the former is extremely fast,
The latter is relatively slow. For example, the pulse output from the incremental encoder 11 is 500k.
Although the frequency is higher than Hz, the communication speed between the absolute encoder 12 and the serial communication port 22 is about 9600 bps.

The pulse input to the pulse input port 21 is an INC counter 2 including an up / down counter.
Enter in 3. As described above, since the rotation direction of the rotation shaft of the motor 6 can be known from the phase difference between the output pulses of the two output terminals of the incremental encoder 11, the INC counter 23 determines the rotation direction from this phase difference and inputs the rotation direction. The pulse determines whether the counter count value is to be incremented or decremented. As will be described later, since the INC counter 23 is designed to preset the absolute value data obtained from the absolute value encoder 12 when the power is turned on, the INC counter 23 counts the pulses input from the pulse input port 21 momentarily. After all, the count value of this counter 23 stores the absolute value data of the grinding wheel head 2.

On the other hand, the absolute value data obtained by the absolute value encoder 12 is fetched by the control section 24 through the serial communication port 22 when it is not in the operating state when the power is turned on. Further, when the power is turned off, the control unit 24 takes in the absolute value data indicated by the absolute value encoder 12 via the serial communication port 22 and stores it in the nonvolatile memory 25 until the power supply is completely stopped. . The non-volatile memory 25 is most typically composed of a battery backed-up RAM, and the EEPRO.
M or the like can also be used.

In the control section 24, the INC counter 23
A motor drive control signal is output to the motor drive unit 27 based on the count value of the above and the absolute value data obtained via the serial communication port 22, and the motor drive unit 27 drives and controls the motor M6 based on this signal. . Further, as described above, the absolute value data indicated by the absolute value encoder 12 is stored in the non-volatile memory 25 before the power supply to the control unit 24 is completely stopped when the power is turned off, and the next power supply is turned on. Sometimes, the absolute value data stored in the nonvolatile memory 25 and the absolute value encoder 1 at that time are stored.
2 is compared with the absolute value data. When the difference is not within the preset allowable range, an alarm is given to the display 26.

3 and 4 are flow charts showing the operation of the control unit 24 when the power is turned on and when the power is turned off.

In FIG. 3, when the power is turned on, the absolute value data at that time indicated by the absolute value encoder 12 is read through the serial communication port 22 (ST1). Let this value be A. Next, the absolute value data stored in the non-volatile memory 25 is read (ST2). Let this value be B. As will be described later, the non-volatile memory 25 stores absolute value data when the power is turned off. ST3
In, the above values A and B are compared. Then, if the difference is within a predetermined allowable range, the operating state is regarded as normal. If the difference exceeds the permissible range, the process proceeds to ST4 to notify the display 26 of an alarm and shift to error processing. In the error processing, the operator must redo the adjustment of the absolute encoder.

On the other hand, when the power is turned off, as shown in FIG. 4, in ST10, the absolute value data A indicated by the absolute value encoder 12 at that time is read and stored in the nonvolatile memory 25 in ST11. This operation is performed until the power supply is completely stopped. Therefore, when the power is turned on next time, in ST2 shown in FIG. 3, the absolute value data stored in ST11 is read for comparison.

With the above operation, if the encoder section is misaligned for some reason between the time when the power is turned off and the time when the power is next turned on, the power is turned on next and the machining operation is started. The abnormal state of the encoder can be known in advance.

FIG. 5 shows another embodiment of the present invention.
In the above embodiment, the absolute value encoder 12 is used when the power is off.
The absolute value data read out from the non-volatile memory 25 is stored in the non-volatile memory 25. However, here, as shown in FIG. 5, the count value indicated by the INC counter 23 is read when the power is off (ST20), and the value is stored in the non-volatile memory. It is stored in the memory 25 (ST21). This is possible because the INC counter 23 also indicates the position data of the grinding wheel head 2 at that time. Therefore, this count value is stored in the non-volatile memory 25, and the next time the power is turned on, the count value shown in FIG.
Is read in ST2 and compared with the value indicated by the absolute encoder in ST3.

In this case, if the difference between the two in ST3 is outside the allowable range, it means that either or both of the absolute value encoder 12 and the incremental encoder 11 are not normal.

FIG. 6 shows the operation of another embodiment of the present invention. In this embodiment, if the control speed of the grinding wheel head 2 is very low even if the power is turned on, the position data obtained via the serial communication port 22 has a high accuracy that sufficiently follows the movement of the grinding wheel head 2. Because it will be something
By comparing this value with the count value of the INC counter 23, it is checked whether or not either or both encoders are operating normally.

That is, first, in ST30, INC
The rotation speed, that is, the moving speed of the wheel head 2 is detected by looking at the cycle of the pulse input to the counter 23. If the speed V is 0, the absolute value encoder 1 at that time is detected.
The absolute value data of 2 and the count value of the INC counter 23 are read, and both are compared (ST34). If the difference between the two is out of the allowable range, an alarm is issued and error processing is performed. When the speed V is equal to or lower than a predetermined constant speed, the absolute value data of the absolute value encoder 12 and IN
The count value of the C counter 23 may be read and the two may be compared. This embodiment has the advantage that the encoder can be diagnosed during operation of the device.

[0031]

According to the present invention, even if the absolute value encoder is misaligned when the power is turned off, it can be diagnosed at the next power-on device startup. It can be prevented. Further, the abnormal state of the encoder can be detected even when the machine is stopped.

[Brief description of drawings]

FIG. 1 is a plan view of a main part of a grinding machine to which an encoder diagnostic device according to an embodiment of the present invention is applied.

FIG. 2 is a configuration diagram of a drive control unit of the grinding machine.

FIG. 3

FIG. 6 is a flowchart showing the operation of the control unit.

Claims (3)

[Claims] 1. An incremental encoder, which is connected to a rotary shaft of a drive motor for driving a moving part of a machine tool, and which outputs an increase / decrease pulse according to a moving amount of the moving part, and a rotary shaft of the drive motor. In a diagnostic device for a machine tool encoder unit, which is connected to a rotary shaft and is configured with an absolute value encoder that outputs absolute value data indicating the absolute position of the moving unit, when the power is off, from the absolute value encoder via a serial communication path. A non-volatile memory that stores the absolute value data of the moving unit that is sent when the power is turned off, and the absolute value data that is sent from the absolute value encoder when the power is turned on and the absolute value data that is stored in the non-volatile memory. And a means for issuing an alarm when the difference is not within a predetermined allowable range. 2. An incremental encoder, which is connected to a rotary shaft of a drive motor for driving a moving part of a machine tool, and which outputs an increase / decrease pulse according to the moving amount of the moving part, and an absolute position of the moving part when the power is turned on. In a diagnostic device for a machine tool encoder unit configured with an absolute value encoder that outputs absolute value data indicating, a counter for counting output pulses of the incremental encoder, and a non-volatile memory for storing the count value of the counter when the power is turned off. When the power is turned on, the absolute value data sent from the absolute value encoder is compared with the position data stored in the non-volatile memory, and when the difference is not within the predetermined allowable range, an alarm is notified. An encoder diagnostic device comprising: means for performing. 3. An incremental encoder, which is connected to a rotary shaft of a drive motor for driving a moving part of a machine tool, and which outputs an increase / decrease pulse according to the moving amount of the moving part, and an absolute position of the moving part when the power is turned on. In a diagnostic device for a machine tool encoder unit configured with an absolute value encoder that outputs absolute value data indicating, a counter that counts output pulses of the incremental encoder, and the counter when the moving speed of the moving unit is equal to or less than a certain value. Of the absolute value data sent from the absolute value encoder and means for issuing an alarm when the difference is not within a predetermined allowable range.