JPH0719849A - Apparatus and method for reading position - Google Patents

Abstract

PURPOSE:To reduce the scale of a circuit and to make it possible to use an absolute encoder even when a motor is rotated by once or more. CONSTITUTION:A measuring means 11 generates the measured value for lower M bits among the position data of N bits of an object to be controlled, whose displacement amount at the specified measuring time interval is limited. A reading means 12 reads the measured value with the measuring means 11 at every specified time. A storage means 13 stores the previous measured value, which is read with the reading means 12. A position-data computing means 14 computes the difference between the present measured value, which is read with the reading means 12, and the previous measured value stored in the storage means 13, counts the upper (N-M) bits based on the above described difference value and computes the position data of N bits.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position reading device and a position reading method, and more particularly to a position reading device and a position reading method for reading the position of an object to be controlled by an XY table device, a robot or the like.

A position reading device in an XY table device, a robot, or the like reads the position of a controlled object that moves within a predetermined range and generates position information. This position reading device generates position information of a predetermined number of bits based on a signal from a displacement sensor that outputs a signal corresponding to the amount of movement of the controlled object.

In the above position reading device, it is necessary to reduce the scale of the circuit for generating the position information of the predetermined number of bits.

[0004]

2. Description of the Related Art FIG. 10 is an explanatory view of an XY table device to which a conventional position reading device is applied. In addition,
Here, only the portion for moving the movable table in the X direction is shown. The movable table 24 of the XY table device is the frame 2
As the ball screw 23 rotatably supported by 2 moves, it moves in the direction of arrow X in the figure. The moving range is indicated by an arrow m in the figure, and the moving base 24 moves from the left end P _{L of the} moving range to the right end P _R. The ball screw 23 is the frame 2
It is rotated by a motor 25 attached to the motor 2.
The incremental encoder 26 detects the rotation angle of the motor 25. That is, two rectangular wave signals of A phase and B phase having different phases corresponding to the rotation angle of the motor 25 are generated. The signal processing circuit 67 generates position data of a predetermined number of bits based on the A-phase and B-phase rectangular wave signals supplied from the incremental encoder 26. The microcomputer 68 reads the position data supplied from the signal processing circuit 67, and servo-controls the motor 25 based on this position data.

During servo control of the motor 25, the microcomputer 68 supplies the command value of the motor current to the servo amplifier 30, and the servo amplifier 30
A motor current is generated and supplied to the motor 25.

FIG. 11 is a block diagram of a conventional position reading device. Incremental encoder 26
Detects the rotation angle of the rotation shaft 34 connected to the rotation shaft of the motor 25 (that is, the rotation angle of the motor 25).

The incremental encoder 26 transmits the light emitted by an LED or the like through a rotating disc having slits printed at predetermined angles, detects the amount of the transmitted light by a phototransistor, etc., and detects the detected signal by a comparator. By binarizing, a one-phase rectangular wave signal is obtained. This one-phase rectangular wave signal has a waveform of one cycle while the motor 25 rotates and one slit of the rotating disk crosses the phototransistor and the next slit thereof. Since the slit is provided for each predetermined angle, the rotation angle of the motor 25 can be detected by this rectangular wave signal.

In the incremental encoder 26,
Actually, in order to detect the rotation direction, A with different phases is used.
Two rectangular wave signals of phase B and phase B are generated. The B-phase rectangular wave signal is obtained by arranging the mechanical position of the optical system including the LED and the phototransistor at a position deviated from the A-phase by 90 degrees. FIG. 12A shows an A-phase rectangular wave signal, and FIG. 12B shows a B-phase rectangular wave signal. As shown in FIGS. 12A and 12B, the A-phase and B-phase rectangular wave signals have a phase difference of 90 degrees.

As shown in FIG. 11, the signal processing circuit 67 includes a phase discriminator 32, a counter section 73 for generating N-bit position data covering the entire moving range of the moving table 24,
It comprises a clock generation circuit 31 for generating a clock signal. The phase discriminator 32 uses a clock signal to generate an UP pulse (up pulse) signal according to the rotation direction of the motor 25 based on the A-phase and B-phase rectangular wave signals supplied from the incremental encoder 26. Alternatively, a DN pulse (down pulse) signal is output.

FIG. 12C shows an UP pulse signal,
FIG. 12D shows a DN pulse signal. 12
As shown in (C) and (D), UP pulse signal or DN
The pulse signals are output one by one at the edge portion of the A-phase or B-phase rectangular wave signal. Therefore, the number of pulses that is four times the total number of slits of the rotating disk of the incremental encoder 26 is output per one rotation of the motor 25. The UP pulse and the DN pulse are supplied to the counter unit 73.

When one UP pulse is supplied, the counter section 73 increments the held count value by one. On the contrary, when one DN pulse is supplied, the held count value is decreased by 1.

The counter unit 73 needs to be able to count the number of pulses corresponding to the entire moving range of the moving table 24.
The maximum value of the range of values counted by the counter unit 73 is represented by the following formula.

Maximum value of the range of the count value = the number of slits of the incremental type encoder × 4 × the maximum number of rotations of the motor Here, for the moving range m of the moving table 24 shown in FIG. Therefore ball screw 2
3) (10 rotations), the entire moving range from the left end position P _L to the right end position P _R can be moved, and assuming that the number of slits of the incremental encoder 26 is 10000, the maximum count value of the counter unit 73 is , 40,000. At this time, the counter unit 73 needs to be able to count a value of 40000 or more.

Here, assuming that the counter unit 73 counts in binary for ease of processing in the microcomputer 68, the required number of bits N is 16 from log40000 / log2 = 15.29. It turns out that this is the end.

FIG. 13 shows a specific example of the conventional counter section 73. The counter section 73 shown in FIG. 13 counts 16-bit position data, and four counters connected in series are used.
Bit up / down (UP / DN) counters 81 to 8
It consists of four and two 8-bit data latches 85 and 86.

When reading the position data, the microcomputer 68 first causes the data latches 85 and 86 to latch the output data of the 4-bit UP / DN counters 81 to 84 by a latch command. After that, when reading the lower 8-bit position data, the data latch 86 is selected by the lower 8-bit selection signal, and the 8-bit output data of the data latch 86 is read. Also, the top 8
When reading the bit position data, the data latch 85 is selected by the selection signal of the upper 8 bits, and the 8-bit output data of the data latch 85 is read.

The microcomputer 86 uses the read value as it is as the count value of the rotation angle of the motor 25 (or the position data of the movable table 24), and performs the servo control of the motor 25 using this count value.

Further, as an encoder for detecting the rotation angle of the motor 25, there is an encoder called an absolute type. An absolute encoder is a rotary disc with a binary code of about 10 bits printed on it, which is illuminated with LED light to detect light and dark with a phototransistor, etc., and corresponds to a rotation angle within one rotation. The base code is output directly from the encoder. Since the Gray code is actually used, it is converted into a binary binary code by code conversion. Therefore, the absolute encoder is the incremental encoder 26 shown in FIG.
And the signal processing circuit 67 including the counter unit 73.

However, the angle data output from the azo-flut type encoder is the angle data for one rotation of the motor.

[0020]

In the conventional position reading apparatus, as shown in the example of FIG. 13, there is a problem that the circuit scale of the counter section 73 capable of counting the entire moving range of the moving table 24 becomes large. Further, if the number of slits of the incremental encoder 26 is further increased to increase the angle detection resolution, or if the ball screw 23 is lengthened to widen the moving range of the moving table 24, the number of bits of the counter unit 73 is further increased and the circuit scale is increased. Will grow accordingly.

Further, there is a problem that the absolute type encoder cannot be used when the motor 25 exceeds one rotation in the entire movement range of the movable table 24.

The present invention has been made in view of the above points, reduces the scale of a circuit for generating position data, and
It is an object of the present invention to provide a position reading device and a position reading method that can use an azo-fluted encoder even when the motor has more than one rotation.

[0023]

FIG. 1 is a block diagram showing the principle of the present invention. In the invention of claim 1, the measuring means 11 generates a measured value for the lower M bits of the N-bit position data of the controlled object.

The reading means 12 reads the measurement value of the measuring means 11 every predetermined time.

The storage means 13 stores the previous measurement value read by the reading means 12.

The position data calculation means 14 calculates the difference between the current measurement value read by the reading means 12 and the previous measurement value stored in the storage means 13,
Based on the difference value, the upper (NM) bits are counted and N-bit position data is calculated.

In the invention of claim 3, the measuring means 11
Is an absolute encoder.

[0028]

In the invention of claim 1, the measuring means may measure the lower M bits of the N-bit position data. Therefore, it is possible to reduce the circuit scale of the measuring means.

According to the third aspect of the invention, the position data calculating means counts the upper (NM) bits from the measured value of the lower M bits supplied from the absolute encoder. Therefore, the azo-fluted encoder can be used even when the motor has more than one rotation.

[0030]

FIG. 2 is an XY to which the first embodiment of the present invention is applied.
An explanatory view of a table device is shown. In addition, here, only a portion for moving the movable table in the X direction is shown. 2, the same components as those in FIG. 10 are designated by the same reference numerals, and the description thereof will be appropriately omitted.

The incremental encoder 26 detects the rotation angle of the motor 25 corresponding to the moving amount of the moving table 24. That is, two rectangular wave signals of A phase and B phase having different phases corresponding to the rotation angle of the motor 25 are generated.

The signal processing circuit 27 is based on the A-phase and B-phase rectangular wave signals supplied from the incremental encoder 26, and the lower order of the N-bit position data that can cover the entire moving range of the moving table 24. Generate an M-bit value.

The microcomputer 28 reads the lower M-bit position data supplied from the signal processing circuit 27 at a predetermined cycle determined by the timer signal generated by the timer signal oscillator 29, and based on this M-bit position data. Then, the upper NM bits are counted to generate N-bit position data.

The microcomputer 28 servo-controls the motor 25 using the generated N-bit position data.

FIG. 3 is a block diagram of the position reading device according to the first embodiment of the present invention. 3, the same components as those in FIG. 11 are designated by the same reference numerals, and the description thereof will be omitted as appropriate. The incremental encoder 26 detects the rotation angle of the motor 25.

As shown in FIGS. 12A and 12B, the incremental encoder 26 outputs A-phase and B-phase rectangular wave signals having a phase difference of 90 degrees.

The signal processing circuit 27, as shown in FIG.
Phase discriminator 32, lower M of N-bit position data
It is composed of a counter unit 33 that outputs bit position data and a clock generation circuit 31. The phase discriminator 32 uses a clock signal, based on the A-phase and B-phase rectangular wave signals supplied from the incremental encoder 26, in accordance with the rotation direction of the motor 25, as shown in FIG. As shown in D), the UP pulse signal or the DN pulse signal is output.

For one rotation of the motor 25, the total number of slits on the rotating disk of the incremental encoder 26 is four.
The UP pulse signal or the DN pulse signal having the doubled number of pulses is output. The UP pulse signal and the DN pulse signal are supplied to the counter unit 33.

When one UP pulse is supplied, the counter unit 33 increments the held count value by one. On the contrary, when one DN pulse is supplied, the held count value is decreased by 1.

The counter unit 33 counts the UP pulse or DN pulse for the lower M bits of the N-bit pulse number corresponding to the entire moving range of the moving table 24.
Therefore, the counter unit 33 outputs the lower M-bit position data of the N-bit position data that covers the entire movement range of the moving table 24.
The lower-order M-bit position data is read from the counter unit 33 at a predetermined cycle determined by the timer signal, and the upper-order NM bits are counted based on the M-bit position data to obtain the N-bit position data. To generate.

FIG. 4 is a flow chart showing a position data generating procedure in the first embodiment of the present invention. In the present embodiment, it is assumed that the speed of the movable table 24 is finite and that the amount of change in the position of the movable table 24 in a predetermined measurement cycle has an upper limit. Based on this premise, the bit number M of the counter unit 33 and the reading cycle T are appropriately set, and the carry of the count value is correctly detected from the magnitude of the change in the count value of the counter unit 33 in the reading cycle T. , The upper (NM) bits are counted.

In this embodiment, the lower bit number M, the cycle T for reading the output data of the counter section 33, and the reference value X1 for determining the occurrence of carry are determined as follows.

First, for all the number of bits N, M such that M <N is determined. Next, when the carry is not generated in the counter unit 33 in the reading cycle T, the maximum value of the increase or decrease of the count value, that is, the maximum value of the UP pulse number or the DN pulse number in T seconds is set as M _P , and the following expression is satisfied. The period T is determined within the range. The condition of the formula is a condition necessary for the reference value X1 to exist.

Maximum Number of Pulses in T Seconds M _P ≦ 2 ^M−1 −1 Next, a reference value X1 is determined within a range that satisfies the following formula. 2 ^M- (Maximum number of pulses in T seconds _MP )
Is the minimum increase / decrease value of the count value when a carry occurs in the counter unit 33 in the reading cycle T.

Maximum number of pulses for T seconds M _P ≦ X1 <2 ^M − (maximum number of pulses for T seconds M _P ) Using the reference value X1 set as described above, occurrence of carry in the reading cycle T seconds It is possible to determine the presence or absence of. That is, the counter unit 3 in the reading cycle T
If the absolute value of the increase / decrease of the count value of 3 (| ΔX |, which will be described later) is equal to or less than the reference value X1, it is determined that a carry has not occurred, and if it is larger than the reference value X1, it is determined that a carry has occurred. be able to.

In this embodiment, the position X of the movable table 24 is calculated by the following formula.

X = X _H × 2 ^M + X _LNEW Here, X _H is the value of the upper _NM bits, and X _LNEW
Is the value of the lower N bits. X _LNEW is a counter unit 3
3 is a count value read from 3, and X _H is a value calculated by the microcomputer 28 from the detected carry.

Further, X _LOLD for holding the count value of the counter section 33 read at the _immediately preceding read timing is provided. X, X _H , X _LNEW , and X _LOLD are stored at predetermined addresses in the memory in the microcomputer 28, for example.

Next, the flowchart of FIG. 4 will be described in detail. The XY stage apparatus includes an origin sensor for detecting the origin of the moving range of the moving table 24, and the moving table 24 is aligned with the origin of the moving range using this origin sensor as an initial setting. The origin of the moving table 24 is set, for example, at the center of the moving range (step 201).

After aligning the movable table 24 with the origin, X_H, X
_LOLD Set the initial value to the value of. X _HIs, for example, 0
Enter, X_LOLDIs the lower M bits of the current counter unit 33.
The count value of the printer is substituted (step 202).

In steps 203 to 213, which will be described below, the microcomputer 28 reads the count value of the counter section 33 every read cycle T seconds to calculate the position X of the movable table 24.

After step 202, it is judged whether or not the timer signal of the period T is supplied. When the timer signal of the period T is supplied, the process proceeds to step 204 (step 2
03).

When the timer signal of the period T is supplied in step 203, first, the count value of the lower M bits is read from the counter section 33 and substituted into X _LNEW (step 204).

Next, the difference ΔX = X _LNEW −X _LOLD between the previous count value and the present count value read from the counter section 33.
Is calculated (step 205).

Next, | ΔX | is compared with the reference value X1 to determine whether a carry has occurred (step 206). When | ΔX | ≦ X1 in step 206, since no carry has occurred, the upper (N−M) bit X _H is not changed and the process proceeds to step 210. If | ΔX |> X1 in step 206, a carry has occurred, so in steps 207 to 209, the upper rank (N
-M) changes the bit of X _H.

At step 207, the sign of ΔX is determined. When ΔX <0, a carry to 2 ^M has occurred, so the value of X _H is incremented by 1 (step 208). vice versa,
When ΔX> 0, a carry-down from 2 ^M has occurred, so the value of X _H is decremented by -1 (step 209).

Next, the current position X of the movable table 24 is calculated by X = X _H × 2 ^M + X _LNEW . When carry does not occur, only X _LNEW is updated,
When a carry occurs, X _H and X _LNEW have been updated (step 210).

Next, the count value X _LNEW of the counter 33 in the current reading is substituted into X _LOLD in order to calculate ΔX in the next reading of the count value from the counter section 33 (step 211).

Next, the microcomputer 28 uses the calculated value of the position X of the movable table 24 to perform necessary application processing such as servo control of the motor 25 (step 212).

Next, at step 213, it is judged whether or not there is an instruction to end the operation of the XY table device. If there is an instruction to end the operation, the processing is ended. If there is no command to end the operation, the process returns to step 203 to continue the calculation of the position data X and the process using the position data X.

Next, the number of bits N required to measure the entire moving range of the moving table 24 is set to N = 8, and the counter unit 33
An example will be described in which the number M of bits of M is set to M = 3. FIG. 5 is an explanatory diagram of a decimal number corresponding to an 8-bit binary number. The lower 2 bits 2 ² to 2 ⁰ shown in FIG. 5 are counted by the counter unit 33, read by the microcomputer 28, and substituted into X _LNEW or X _LOLD . The upper 5 bits of 2 ⁷ to 2 ³ are counted as X _H inside the microcomputer 28.

The decimal number in FIG. 5 corresponds to the value of the position X = X _H × 2 ^M + X _LNEW of the moving table 24 expressed in decimal number.

First, the reading cycle T is set so as to satisfy the above expression. That is, the maximum pulse number M _{P in} T seconds
The period T is set so that ≦ 2 ^3-1 −1 = 3.
Here, it is assumed that the maximum pulse number M _P = 3 for T seconds.

Next, the reference value X1 is determined within the range that satisfies the above expression. That is, under the condition of the maximum pulse number M _P ≦ X1 <2 ^M − for T seconds ((the maximum pulse number M _P for T seconds), from M _P = 3, M = 3, 3 ≦ X1 <2 ³ −
3 = 5 and X1 can be set to 3 or 4. Here, X1 = 4.

An example of reading the count value from the counter section 33 and calculating X will be described below. The origin of the moving table 24 is set at the center of the moving range, for example. With the initial setting after the movable table 24 is aligned with the origin, _XH = 0, X
_{It is assumed that LOLD} = 0 and X = 0. From this state, after T seconds, the _count value is read into X _LNEW and X _{LN
If EW} = 3, then | ΔX | = 3 and | ΔX | =
It becomes X1. In this case, since carry has not occurred, X _H remains as it is, X = 3, and a correct X value is generated.

[0066] In addition, from the state of _{X = 6, X H = 0} , X LOLD = 6, then, when you read the count value of the counter unit 33, when the UP pulse had entered three, X _LNEW =
It becomes 1. At this time, ΔX = 1-6 = -5, and | Δ
Since X |> X1 and ΔX <0, a carry to the upper digit occurs, so X _H is incremented by 1 and X _H = 1. Therefore, X = 1 × 2 ³ + 1 = 9, and a correct X value is generated.

If three DN pulses are present when the count value of the counter unit 33 is read next from the state of X = 18, X _H = 2, and X _LOLD = 2, X _LNEW
= 7. At this time, ΔX = 7−2 = 5, and | Δ
Since X│> X1 and ΔX> 0, and a carry down from the upper digit occurs, X _H is decremented by 1 and X _H = 1. Therefore, X = 1 × 2 ³ + 7 = 15, and the correct X value is generated.

If three DN pulses are _input when the count value of the counter unit 33 is read next from the state of X = 1, X _H = 0, and X _LOLD = 1, X _LNEW =
It becomes 6. At this time, ΔX = 6-1 = 5, and | ΔX
Since |> X1 and ΔX> 0, and a carry down from the upper digit occurs, X _H is decremented by 1 and X _H = -1. Therefore, X = −1 × 2 ³ + 6 = −2, and a correct X value is generated.

Further, X = -11, X _H = -2, X _LOLD =
Next, when the count value of the counter unit 33 is read from the state of 5, if there are three UP pulses, X
_LNEW = 0. At this time, ΔX = 0−5 = −5, and when | ΔX |> X1 and ΔX <0, a carry to the higher digit occurs, so X _H is incremented by 1 and X _H = −1. Become. Therefore, X = −1 × 2 ³ + 0 = −8, and a correct X value is generated.

The origin of the moving table 24 is not limited to the center of the moving range, but may be set at the left end of the moving range, for example.

As described above, in this embodiment, the position X of the movable table 24 can be correctly generated.

FIG. 6 shows a concrete example of the counter section of the first embodiment of the present invention. The counter unit 33 shown in FIG. 6 counts 8 bits of 16-bit position data.
4 serially connected 4-bit up / down (UP / D
N) Counters 41, 42 and one 8-bit data latch 43.

When reading the count value of the counter section 33, the microcomputer 28 first causes the data latch 43 to latch the output data of the 4-bit UP / DN counters 41 and 42 by a latch command. Thereafter, the data latch 43 is selected by the lower 8-bit selection signal, and the 8-bit output data of the data latch 43 is read.

As described above, the microcomputer 28 generates the position data X of the moving table 24 from the read count value and uses the position data X to drive the motor 25.
Servo control of.

As described above, in the present embodiment, the number of bits of the counter section 33 can be reduced to reduce the circuit scale.

FIG. 7 is a flow chart showing the position data generating procedure in the second embodiment of the present invention. In the second embodiment, in order to detect the speed abnormality of the moving table 24, the reference value X0 satisfying the following formula is provided. For the maximum number of pulses for T seconds M _P ≦ X0 <X1 <2 ^M − (maximum number of pulses for T seconds M _P ) | ΔX |
Despite carry has not occurred, because it exceeds the maximum number of pulses M _P of T seconds provisions, the speed of the movable table 24 is determined to have become too large due to some abnormality.

X0 <| ΔX | ≦ X1 Next, the flowchart of FIG. 7 will be described in detail.
It should be noted that in FIG. 7, description of portions that perform the same processing as in FIG. 4 will be appropriately omitted. As the initial setting, the moving table 2
Align 4 with the origin of the movement range. (Step 301).

After the movable table 24 is aligned with the origin, X_H, X
_LOLD Set the initial value to the value of. X _HIs, for example, 0
Enter, X_LOLDIs the lower M bits of the current counter unit 33.
Substitutes the count value (step 302).

In steps 303 to 314, the microcomputer 28 calculates the position X of the movable table 24 by reading the count value of the counter section 33 every read cycle T seconds.

In step 303, it is judged whether or not the timer signal of the period T is supplied, and when the timer signal of the period T is supplied, the process proceeds to step 304.

When the timer signal of the period T is supplied in step 303, first, the count value of the lower M bits is read from the counter section 33 and substituted into X _LNEW (step 304).

Next, the difference ΔX = X _LNEW −X _LOLD between the previous count value and the present count value read from the counter section 33.
Is calculated (step 305).

Next, | ΔX | is compared with the reference value X0, and it is determined whether or not it is less than or equal to the maximum pulse number M _{P in} the prescribed T seconds (step 306). In step 306,
When | ΔX | ≦ X0, since the maximum number of pulses M _{P in} the prescribed T seconds or less and no carry has occurred, X _H of the upper (NM) bits is not changed and step 31
Go to 1.

If | ΔX |> X0 at step 306, then | ΔX | and X1 are compared at step 307. In step 307, when | ΔX | ≦ X1, X0 <| ΔX
Since | ≦ X1 is satisfied and the carry has not occurred, the maximum pulse number M _P in the specified T seconds is exceeded, so it is determined that the speed of the movable table 24 has become excessive. . In this case, in step 315, processing is performed when speed is abnormal such as stopping the motor 25, and the processing ends.

When | ΔX |> X1 in step 307, since a carry has occurred, steps 308 to 3 are executed.
10, in the same manner as steps 207 to 209 of FIG.
X _H of the upper (NM) bits is changed according to the sign of ΔX.

Next, in step 311, X = X _H × 2
^The current position X of the movable table 24 is calculated by ^M + X _LNEW .

Next, in the next reading of the count value, in order to calculate ΔX, the count value X _LNEW of the counter 33 in the current read is substituted into X _LOLD (step 312).

Next, the microcomputer 28 uses the calculated value of the position X of the movable table 24 to perform necessary application processing such as servo control of the motor 25 (step 313).

Next, at step 314, it is judged whether or not there is a command to end the operation of the XY table device, and if there is a command to end the operation, the process ends. If there is no command to end the operation, the process returns to step 303 and the calculation of the position data X and the process using the position data X are continued.

As described above, in the second embodiment, the reference value X0 for determining the presence / absence of the speed abnormality is provided, and the speed abnormality of the moving table 24 can be monitored.

FIG. 8 shows a block diagram of the third embodiment of the present invention. In the third embodiment, the absolute type encoder 51 is used as the encoder. Further, it is provided with a microcomputer 28 and a timer oscillator 29 for generating a timer signal having a cycle T. Absolute encoder 51
Measures the absolute angle for one rotation of the motor 25 and outputs an M-bit binary count value. The rotation angle of the motor 25 is measured by the angle of the rotation shaft 34 connected to the rotation shaft of the motor 25.

With respect to the moving range of the moving table 24, the motor 2
5 rotates a plurality of times, and the position data X requires a bit number N such that N> M. Similar to the case where the N-bit position data X is calculated from the M-bit count value of the counter unit 33 in the first embodiment, in the third embodiment, the microcomputer 28 causes the absolute error to be calculated at every appropriate cycle T. It is possible to read the M-bit data of the type encoder 51, determine the presence or absence of a carry, and generate the N-bit position data X.

As described above, the absolute type encoder 51 cannot be used when the motor 25 multi-rotates, whereas in the third embodiment, the absolute type encoder 51 is used even when the motor 25 multi-rotates. Encoder 51
Can be used to generate the correct position data.

Further, with respect to the speed of the movable table 24, the period T
Since the high-order bits can be counted by the microcomputer 28 by properly setting, the signal lines for the total number of bits for one rotation of the absolute encoder 51 need not be connected to the microcomputer 28. Therefore, the number of signal lines can be reduced accordingly, and the circuit scale of the receiving circuit of the microcomputer 28 can also be reduced.

Further, the absolute encoder 51 itself is not limited to one rotation cycle but to a 1/2 rotation cycle or 1 / rotation cycle.
In the configuration in which the count value is output in a cycle of 10 revolutions, the higher-order bits can be counted by the microcomputer 28. In this case, without reducing the angular resolution,
The number of bits of the count value of the absolute encoder 51 can be reduced, and the number of optical sensors in the absolute encoder 51 can be reduced by the reduced number of bits. Also, the number of signal lines connecting the absolute encoder 51 and the microcomputer 28 can be reduced.

FIG. 9 shows a block diagram of the fourth embodiment of the present invention. The fourth embodiment is an example in which a resolver is used as the angle detector. Functionally, the resolver 55, R /
A combination of a D (resolver / digital) converter 57 and a resolver excitation oscillator 56 has the same function as an absolute encoder.

The resolver excitation oscillator 56 is V · sin ω
The signal t is supplied to the resolver 55 and the R / D converter 57. Here, the angle of the rotary shaft 34 connected to the rotary shaft of the motor 25 is θ.

The resolver 55 is a resolver for one-phase excitation and two-phase output, and is composed of one rotor and two stators. When a signal of V · sinωt is supplied to the rotor,
From the stator, K · V · sin ωt · sin θ si
The n signal and the cos signal K · V · sin ωt · cos θ are generated. Note that K is a fixed count determined by the resolver 55.

The R / D converter 57 is supplied from the resolver 55 and has si of K · V · sin ωt · sin θ.
n signal, cos signal of K · V · sin ωt · cos θ, and V · sin supplied from the resolver oscillator 56.
Based on the signal ωt, an M-bit count value corresponding to the angle θ for one rotation of the motor 25 is generated.

The R / D converter 57 is a follow-up comparison type R
/ D converter, equipped with M-bit counter,
The pulses of the internal oscillator are counted until the count value reaches a value corresponding to the angle θ. The count value of this counter is output as M-bit data.

With respect to the moving range of the moving table 24, the motor 2
5 rotates a plurality of times, and the position data X requires a bit number N such that N> M. Similar to the third embodiment,
In the fourth embodiment, the microcomputer 28 can read the M-bit data of the R / D converter 57 every appropriate period T, determine the presence or absence of a carry, and generate the N-bit position data X. .

Conventionally, when the resolver 55 is used in the case where the motor 25 is rotated many times, an external counter for counting the upper (NM) bits is provided and the R / D converter 5 is used.
It was necessary to count N-bit position data using the carry output from 7. On the other hand, in the fourth embodiment, an external counter is not required, and the number of circuits can be reduced.

In each of the above embodiments, an example of measuring the position of the moving base 24 that moves linearly has been described, but the present invention is similarly applied to the case of measuring the angular position of the arm or the like of the rotating robot. can do.

[0104]

As described above, according to the invention of claim 1,
Since the measuring means only needs to measure the lower M bits of the N-bit position data, it has a feature that the circuit scale of the measuring means can be reduced.

According to the third aspect of the invention, since the position data calculating means counts the upper (NM) bits from the measured value of the lower M bits supplied from the absolute encoder, the motor exceeds one rotation. You can also use an azo-fluted encoder.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is an explanatory diagram of an XY table device to which the first embodiment of the present invention is applied.

FIG. 3 is a configuration diagram of a first embodiment of the present invention.

FIG. 4 is a flowchart showing a position data generation procedure in the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a decimal number corresponding to an 8-bit binary number.

FIG. 6 is a diagram showing a specific example of a counter section according to the first embodiment of the present invention.

FIG. 7 is a flowchart showing a position data generation procedure in the second embodiment of the present invention.

FIG. 8 is a configuration diagram of a third embodiment of the present invention.

FIG. 9 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 10: X to which a conventional position reading device is applied
It is an explanatory view of a Y table device.

FIG. 11 is a configuration diagram of a conventional position reading device.

FIG. 12: A-phase and B-phase rectangular wave signals and UP pulse, D
It is explanatory drawing of N pulse.

FIG. 13 is a diagram showing a specific example of a conventional counter section.

[Explanation of symbols]

 11 measuring means 12 reading means 13 storage means 14 position data calculating means 23 ball screw 24 moving table 25 motor 26 incremental encoder 27 signal processing circuit 28 microcomputer 29 timer signal oscillator 30 servo amplifier 31 clock generation circuit 32 phase discriminator 33 counter section 41, 42 4-bit UP / DN counter 43 Data latch 51 Absolute encoder 55 Resolver 56 Resolver excitation oscillator 57 R / D converter

Claims (6)

[Claims] 1. A position reading device for reading the position of a controlled object to generate N-bit position data, wherein a lower M of the N-bit position data of the controlled object is detected.
Measuring means (11) for generating a measured value for a bit
A reading means (12) for reading the measured value of the measuring means (11) at a predetermined time interval; a storage means (13) for storing the previous measured value read by the reading means (12); The difference between the current measured value read by the means (12) and the previous measured value stored in the storage means (13) is calculated, and the higher order (N-
M) A position reading device characterized by comprising a position data calculating means (14) for counting bits and calculating N-bit position data. 2. The position reading device according to claim 1, wherein the measuring means (11) comprises an incremental encoder, a phase discriminator, and an M-bit up / down counter. 3. The position reading device according to claim 1, wherein the measuring means (11) is an absolute encoder. 4. The position reading device according to claim 1, wherein the measuring means (11) is a combination of a resolver and a resolver-digital converter. 5. The position data calculation means (11) uses a judgment reference value as a difference between a current count value read by the reading means (12) and a previous count value stored in the storage means. 2. The position reading device according to claim 1, wherein when it exceeds, it is determined that the moving speed of the controlled object is abnormal and the upper control means is notified of the occurrence of the abnormal moving speed. 6. A position reading method in a position reading apparatus for reading the position of a controlled object and generating N-bit position data, wherein a lower M of the N-bit position data of the controlled object.
The measured value of the bit is read at every predetermined time, the difference between the read current measured value and the previous measured value is calculated, and the upper (NM) bits are calculated based on the difference value. A position reading method characterized by counting and calculating N-bit position data.