JPH095115A - Position detection circuit - Google Patents

Abstract

PURPOSE: To provide a position detection circuit which is constituted at low costs, by which a position can be detected with high accuracy and which enhances the degree of freedom regarding the installation of the driving mechanism of a servomotor. CONSTITUTION: A pulse signal which is outputted from an incremental encoder 1 is counted by a counter 2, and a counted value is outputted to a frequency divider 3 as angle information on a motor. Then, the angle information on the motor is converted into angle information on a load by the frequency divider 3. Then, in an instruction generator 4, detection position information, on a load,, which is outputted from the outside is made to correspond to the angle information on the motor on the basis of the angle information on the load by the frequency divider 3 and on the basis of the counted value which is outputted from the counter 2. After that, in a comparator 5, the detection position information is compared with the counted value by the counter 2. When they become an identical value, a position detection signal is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting circuit suitable for controlling a servomotor.

[0002]

2. Description of the Related Art Conventionally, position control of a load by a servo motor has been performed by detecting the position or rotation angle of the load. FIG. 4 shows a conventional servomotor drive mechanism. In this figure, reference numeral 20 is a servo motor which controls the position of a table 23 which is a load. Also,
Reference numeral 20a is a drive shaft of the servomotor 20. Reference numeral 1 denotes an incremental encoder which is a component of the servo motor 20, and outputs a pulse signal at equal angular intervals according to the rotation of the drive shaft 20a. Reference numeral 21 denotes a drive gear having a number of teeth P (P is an integer), which is attached to the drive shaft 20a.

Reference numeral 22 denotes a driven gear having a number of teeth of Q (Q is an integer), which is attached to a rotary shaft of a table 23 and is a driving gear
Engage with 1. Therefore, the rotation of the drive shaft 20 a of the servo motor 20 is transmitted to the table 23 via the drive gear 21 and the driven gear 22. Further, the gear ratio at this time is Q / P. 24 is a sensor, the table 23
The marker attached to the edge of the is detected, and when the marker is detected, a detection signal is output.

In the servo motor drive mechanism described above, the speed control of the servo motor 20 and the table 23 are performed based on the pulse signal output from the incremental encoder 1 and the position detection signal output from the sensor 24.
Position control. Further, in this type of drive mechanism, an absolute encoder 25 that outputs a rotation angle as an absolute value is attached to the rotation shaft of the table 23 instead of the sensor 24. In such a drive mechanism, the angle information output from the absolute encoder 25 is used as the absolute position information of the table 23, and the position control of the table 23 is performed based on this.

[0005]

By the way, the sensor 24
In the drive mechanism of the servomotor that controls the position of the table 23 based on the position detection signal output from the table 23, the position detection accuracy of the table 23 is low, and when it is necessary to detect a plurality of positions, the sensor is adjusted accordingly. However, there are problems such as an increase in cost and the mounting position of the sensor.

Further, in the drive mechanism of the servo motor using the absolute encoder 25 instead of the sensor 24, the absolute encoder itself is expensive,
Further, there is a problem that the absolute encoder may not be attached to the rotating shaft on the load side due to the installation position of the drive mechanism.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a position detection circuit which enables highly accurate position detection with an inexpensive structure.

[0008]

According to the first aspect of the present invention,
In a position detection circuit that detects a predetermined position of a load that is rotationally controlled by a motor through a predetermined gear ratio, an angle information output unit that sequentially outputs angle information of the motor according to the rotation of the motor, and an input this time. Change amount detecting means for detecting a change amount between the motor angle information and the previously input motor angle information, and a change amount for converting the change amount output by the change amount detecting means into the load angle change amount. Based on the load angle change amount output from the amount conversion unit, the change amount conversion unit, and the load angle information obtained last time, the load angle information with respect to the motor angle information input this time is displayed. Load angle output means for outputting, cycle processing means for processing so that the load angle information outputted from the load angle output means is outputted in accordance with a preset cycle, and the cycle processing means. A position detecting circuit, characterized by comprising a position detecting means for detecting a predetermined position of the load based on the angle information of al the outputted loads.

According to a second aspect of the present invention, the predetermined position detecting means is preliminarily inputted with load angle information corresponding to the predetermined position, and is sequentially outputted from the motor angle information and the cycle processing means. Load angle information of the load, the angle information of the load corresponding to the predetermined position, the detection angle conversion unit that corresponds to the angle information of the motor, and the angle information of the motor output from the detection angle conversion unit, 2. A position detection signal output unit for comparing the angle information of the motor sequentially output from the angle information output unit and outputting a position detection signal when both angle information match. It is the described position detection circuit.

According to a third aspect of the present invention, the detected angle conversion means obtains a difference between the load angle information corresponding to the predetermined position and the current load angle information output from the cycle processing means, and The position of the load angle information corresponding to the predetermined position within the range between the minimum value and the maximum value of the load angle information output from the cycle processing means is determined, and the determined difference is determined according to the position. It is determined whether the value of the preset cycle is added or subtracted, or the addition or subtraction is not performed, and the value obtained as a result is converted into angle information of the motor based on the gear ratio. 3. The position detection circuit according to claim 2, wherein the load angle information corresponding to the predetermined position is made to correspond to the motor angle information by adding the conversion result to the current motor angle information.

According to a fourth aspect of the present invention, a load of which rotation is controlled via a predetermined gear ratio by a servo motor having a built-in incremental encoder that outputs a pulse signal at equal angular intervals according to the rotation of the drive shaft. In a position detection circuit that detects a predetermined position, a counter that sequentially counts and outputs pulse signals output from the incremental encoder, and a count value output from the counter,
A frequency divider that outputs load angle information corresponding to the angle of the load rotated by the servo motor based on the gear ratio in accordance with a preset cycle, and a counter that sequentially outputs from the counter. Based on the numerical value and the angle information of the load output from the frequency divider, the angle information corresponding to the predetermined position of the preset load is converted according to the count value sequentially output from the counter, A command generator that outputs angle information of the predetermined position according to the count value as detection command information, and a value of the detection command information output from the command generator and a count value sequentially output from the counter And a comparator that outputs a position detection signal when the values become the same, a position detection circuit.

[0012]

In the position detecting circuit according to the first aspect of the present invention, the amount of change in the angle information of the motor is obtained, converted into an angle change of the load, and based on the conversion result and the previous angle information of the load, The load angle information corresponding to the angle change amount of the motor is obtained, and the obtained load angle information is output according to a preset cycle. Therefore, the load angle information can be generated at an arbitrary cycle. Therefore, not only the position or angle of the load side can be directly detected but also the predetermined position of the load can be detected, and the angle information of the load can be generated at a desired cycle.

In the position detecting circuit according to the second aspect of the present invention, the angle information corresponding to the predetermined position of the load is made to correspond to the angle information of the motor, and the angle information of the motor corresponding to the predetermined position of the load is sequentially output. A position detection signal is output based on the motor angle information. As a result, the predetermined position in the load is determined based on the angle information of the motor that is the basis of the angle information of the load, so that accurate position detection can be performed.

The position detecting circuit according to the third aspect of the present invention determines the position of the load angle information corresponding to a predetermined position within the output range of the load angle information that is sequentially output,
Depending on the determined position, addition or subtraction of a preset cycle value to the difference between the load angle information corresponding to the predetermined position and the load angle information sequentially output, or non-execution of this addition or subtraction is performed. The angle information of the load corresponding to the predetermined position is made to correspond to the angle information of the motor by converting the result into the angle information of the motor and adding it to the current motor angle information. This makes it possible to accurately associate the load angle information corresponding to the predetermined position with the motor angle information regardless of where the load angle information corresponding to the predetermined position is within the output range of the load angle information. Becomes

According to the fourth aspect of the present invention, the position detection circuit counts the pulses sequentially output from the incremental encoder built in the servo motor, calculates the rotation angle of the load based on the counted value, and calculates the load rotation angle. The angle information corresponding to the predetermined position of the load is converted according to the angle information of the motor based on the rotation angle and the above-mentioned count value, which is compared with the above-mentioned count value, and when they match, a position detection signal is output. Therefore, highly accurate position detection can be performed with an inexpensive configuration.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the position detection circuit in this embodiment. Further, the position detection circuit in this embodiment will be described as being applied to the drive mechanism of the servo motor shown in FIG. 4 (excluding the sensor 24 and the absolute encoder 25).

In FIG. 1, reference numeral 1 denotes an incremental encoder (pulse generator), which outputs pulse signals at equal angular intervals according to the rotation of the drive shaft 20a of the servomotor, as described above. Here, the drive shaft 20a is 1
A pulse signal shall be output each time it rotates. Reference numeral 2 denotes a counter, which counts the pulses output from the incremental encoder 1 and uses this count value as the drive axis 2
Angle information of 0a (hereinafter referred to as drive axis angle information) θ
Output as _m (k).

In this embodiment, a 16-bit binary counter is used as the counter 2. Therefore, the drive shaft angle information is sequentially output in the range of 0000 to FFFF, and the drive shaft makes one rotation for each count up.

Reference numeral 3 is a frequency divider (angle information conversion means),
The count value output from the counter 2 is used as the drive gear 21.
Number of teeth P of the driven gear 22, the number of teeth Q of the driven gear 22 (where P <Q), and the total number T of angle detection points per rotation of the table 23.
Based on (hereinafter, referred to as cycle T), the number of points corresponding to the rotation of the table 23 is counted, and this is calculated as the table 2
Angle information of 3 (hereinafter referred to as load angle information) θ _L (k)
Output as

In this embodiment, the number of teeth P of the drive gear 21 is 10, and the number of teeth Q of the driven gear 22 is 100, so that the gear ratio is 10. Further, the total number T of angle detection points per rotation of the table 23 is set to 360, and the frequency divider 3 outputs a numerical value from 0 to 359 as load angle information θ _L (k) according to the rotation angle of the table 23. And

Reference numeral 4 denotes a command generator, which detects detected position information θ _L ^* and load angle information θ in which the detected position of the table 23 is represented by a value (fixed value) corresponding to the output value of the frequency divider 3.
_L (k), gear ratio P / Q, and drive axis angle information θ
_{Based on m} (k), the detection position information on the drive shaft 20a side corresponding to the detection position information θ _L ^* (hereinafter referred to as drive side position detection information) θ _m ^* (k) is output.

That is, when the detection position of the table 23 is defined as a position rotated 90 ° from the origin, the detection position information θ _L ^* becomes 90 in this embodiment, and the command generator 4
Since the detected position information θ _L ^* corresponds to the drive axis angle information, the drive side position detection information θ _m ^* (k) changes to 1194, 1FA4, 2DB4, ... Every time the table 23 makes one rotation. Go.

Further, θ ₀ input to the command generator 4 is
It is a value required when the detected position information θ _L ^{* is associated} with the drive axis angle information, which will be described in detail later.

Reference numeral 5 denotes a comparator, which is drive side position detection information θ.
_The drive axis angle information θ _m (k) is compared with _m ^* (k), and when the two values are equal, a position detection signal is output. 6
Is a switch, which is turned off when an output inhibit signal (described later) is output from the command generator 4, and forcibly turns off the position detection signal output from the comparator 5.

Next, the configuration of the frequency divider 3 of the position detection circuit described above will be described with reference to FIG. In FIG.
Reference numeral 10 denotes a memory, which is the previously input drive side position information θ.
Store _m (k-1). A subtracter 11 outputs a difference Δθ _m (k) between the input drive axis angle information θ _m (k) and the previously input drive axis angle information θ _m (k−1). In addition, for example, the counter 2 may display the full count value (FFF
F) is counted up to 0000, subtracter 1
1 outputs the difference from the previous value (FFFF) as 1.

Reference numeral 12 denotes an electronic gear, which determines a gear ratio from the number P of teeth of the driving gear 21 and the number Q of teeth of the driven gear 22 which are input from the outside, and based on this, a difference Δθ _m output from the subtractor 11 Angle change amount Δθ of load corresponding to (k)
Output _L (k). Therefore, the load angle change Δ
θ _L (k) is Δθ _L (k) = P / Q · Δθm (k). In the present embodiment, the gear ratio is 10, and the counter 2 counts up each time the drive shaft 20a makes one rotation. Therefore, if the difference Δθ _m (k) is 10, the electronic gear 12 rotates the load. 1 is output as the amount of change Δθ _L (k).

Reference numeral 13 denotes an adder, which stores the load angle change amount Δθ _L (k) output from the electronic gear 12 into the memory 15
The previous load side position information θ _L (k−1) stored in is added and the position information θ (k) is output. Reference numeral 14 denotes a periodic function generator, which is the position information θ output from the adder 13.
(K) is adjusted so as to be output in the cycle T, and output as the load angle information θ _L (k). For example, in the case of this embodiment,
The position information θ (k) is 359 based on the addition result of the adder 13.
When the value exceeds, the load angle information θ _L (k) is adjusted to be output from 0 again according to the value that has exceeded.

The operation of the above-mentioned position detection circuit will be described below with reference to FIGS. Here, FIG. 3 is a graph showing the relationship between the count values output from the counter 2 and the frequency divider 3. First, when the position detection circuit of this embodiment is activated, a reset signal is supplied to the counter 2 and the frequency divider 3, and the count value of each is set to zero.
As a result, the origins of the drive shaft 20a and the table 23 are set. Further, the reset signal is sent to the memory 10, 1
It is also output to 5, and the stored contents of each memory are cleared.

Next, when the servo motor 20 rotates and a pulse signal is output from the incremental encoder 1 in response to the rotation, the pulse signal is counted by the counter 2 and divided as drive axis angle information θ _m (k). Output to the container 3. Then, the frequency divider 3 converts the drive axis angle information θ _m (k) into load angle information θ _L (k) by performing the following processing, and outputs the load angle information θ _L (k).

In FIG. 2, first, the drive axis angle information θ _m
When (k) is input to the frequency divider 3, the subtracter 11 takes the difference from the previously input drive axis angle information θ _m (k−1), and the drive axis angle change amount Δθ _m ( k) is calculated. Further, the memory 10 stores the previous drive axis angle information θ _m.
After outputting (k-1), the drive axis angle information θ input this time
Remember _m (k). Next, in the electronic gear 12, the angle change amount Δθ _m (k) of the drive shaft is converted into the position change amount Δθ _L (k) of the table 23, and the load angle information θ _L (k (k) previously output in the adder 13 is converted. -1) is added.

As a result, position information θ (k) is obtained, and this position information θ (k) is output to the periodic function generator 14. The periodic function generator 14 performs the following conditional processing on the position information θ (k) based on the value of the period T set from the outside. That is, when the position information θ (k) is larger than T−1, θ
(K) -T is output as the load angle information θ _L (k). If the position information θ (k) is smaller than 0, θ (k) +
Output T as load angle information θ _L (k). When the position information θ (k) is 0 or more and T−1 or less, θ (k) is output as it is as the load angle information θ _L (k).

Next, in the command generator 4, the load angle information θ _L (k) output from the frequency divider 3 and the drive axis angle information θ _m (k) output from the counter 2 are input from the outside. The detected position information θ _L ^*
Convert to _m ^* (k). The procedure will be described below with reference to FIG.

First, prior to the above-mentioned conversion, in order to set a certain range for the detected position information θ _L ^* as an initial setting, range information θ o input from the outside (where θ o <T /
Based on 2), the following condition processing is performed to calculate the upper limit value θ _P ^* and the lower limit value θ _N ^* of the above range. When θ _L ^* + θ o is larger than T−1, the upper limit value θ _P ^{* is set} to θ _L ^* + θ o −T. When θ _L ^* + θ o is T−1 or less, the upper limit value θ _{P is set} to θ _L ^* + θ o. When θ _L ^* −θ o is smaller than 0, the lower limit value θ _{N is set} to θ _L ^* −
Let θo + T. When θ _L ^* -θo is 0 or more, the lower limit value θ _N ^{* is set} to θ _L ^* -θ o.

The range is set by the upper limit value θ _P ^* and the lower limit value θ _N ^* obtained by the above-mentioned condition judgment, according to the positional relationship of the detected position with respect to the origin of the table 23 and the cycle T.
_It is needed to convert _L ^* to θ _m ^* (k). And
After performing this initial setting, the following condition processing is further performed to convert θ _L ^* into θ _m ^* (k).

Θ _N ^* <θ _P ^* and θ _N ^* <θ _L (k) <
When θ _P ^* , θ _m ^* = θ _m (k) + (P / Q) {θ _L ^* −θ _L (k)} θ _N ^* > θ _P ^* , and T / 2 <θ _L ^* , And θ _N ^* <θ _L
When (k), θ _m ^* = θ _m (k) + (P / Q) {θ _L ^* −θ _L (k)} θ _N ^* > θ _P ^* , and T / 2 <θ _L ^* , And θ _P ^* > θ _L
When (k), θ _m ^* = θ _m (k) + (P / Q) {θ _L ^* -θ _L (k) -T} θ _N ^* > θ _P ^* and T / 2> θ _L ^{* And} θ _N ^* <θ _L
When (k), θ _m ^* = θ _m (k) + (P / Q) {θ _L ^* −θ _L (k) + T} θ _N ^* > θ _P ^* and T / 2> θ _L ^* , And θ _P ^* > θ _L
At the time of (k), θ _m ^* = θ _m (k) + (P / Q) {θ _L ^* −θ _L (k)} Further, when none of the above-mentioned conditions 1 to 3 is satisfied, θ _m ^{* *} Outputs the output stop signal without changing the previous value.

For example, in the case where the above-mentioned respective values have the relationship shown in FIG. 3, among the above conditions (1) to (4), the driving side position detection information θ _m ^* (k) is:
A value obtained by adding the value obtained by subtracting the load angle information from the detected position information and multiplying it by the reciprocal of the gear ratio is added to the drive shaft angle information output from the counter 2.

The drive side position detection information θ _m ^* (k) output from the command generator 4 is used by the comparator 5 as drive axis angle information θ.
_The position detection signal is output when compared with _m (k) and when they have the same value. Then, in the switch 6, when the output prohibition signal is not output from the command generator 4, the switch 6 is turned on, and the position detection signal is output from the comparator 5 to the outside.

As the counter 2, a counter that counts up when the servomotor rotates forward and counts down when the servomotor rotates in reverse is used, and the electronic gear 12 in the frequency divider 3 is used.
Is the rotation change amount Δθ of the positive sign during normal rotation
_{If a device} that outputs _L (k) and outputs the rotation change amount Δθ _L (k) of the load with a negative sign during reverse rotation is used, a position detection circuit that can detect the desired load position even during reverse rotation should be configured. You can

As described above, the position detection circuit in this embodiment is indispensable for the control of the servomotor, and the desired load is determined based on the pulse signal output from the incremental encoder normally built in the servomotor. Since the position is detected, inexpensive and highly accurate position detection can be performed.

[0040]

As described above, according to the first aspect of the invention, in the position detection circuit for detecting the predetermined position of the load whose rotation is controlled by the motor through the predetermined gear ratio, the rotation of the motor Angle information output means for sequentially outputting angle information of the motor according to, and change amount detection means for detecting a change amount between the angle information of the motor input this time and the angle information of the motor input last time, A change amount conversion means for converting the change amount output by the change amount detection means into the load angle change amount, the load angle change amount output from the change amount conversion means, and the load angle obtained last time. Load angle output means for outputting the angle information of the load with respect to the angle information of the motor input this time based on the information,
The load angle information output from the load angle output means is
Since it comprises a cycle processing means for processing so as to output according to a preset cycle, and a predetermined position detecting means for detecting a predetermined position of the load based on angle information of the load output from the cycle processing means, Not only the predetermined position of the load can be detected without directly detecting the position or the angle on the load side, but also the angle information of the load can be generated at a desired cycle. The degree of freedom regarding installation is improved.

According to the second aspect of the present invention, the predetermined position detecting means is preliminarily inputted with the load angle information corresponding to the predetermined position, and the sequentially output motor angle information and the cycle processing means are used. Based on the output load angle information, load angle information corresponding to the predetermined position,
A detected angle converting means corresponding to the angle information of the motor, and motor angle information output from the detected angle converting means,
The position detection signal output unit that compares the angle information of the motor sequentially output from the angle information output unit and outputs a position detection signal when the two pieces of angle information match, thus determining the predetermined position in the load. However, since it is performed based on the angle information of the motor that is the basis of the angle information of the load, accurate position detection can be performed.

According to the third aspect of the invention, the detected angle conversion means obtains the difference between the load angle information corresponding to the predetermined position and the current load angle information output from the cycle processing means. At the same time, the position of the load angle information corresponding to the predetermined position within the range between the minimum value and the maximum value of the load angle information output from the cycle processing means is determined, and the position is determined according to the position. It is determined whether the value of the preset period is added to or subtracted from the difference or whether the addition or subtraction is not performed, and the resulting value is converted into angle information of the motor based on the gear ratio. The load angle information corresponding to the predetermined position is negative because the load angle information corresponding to the predetermined position is made to correspond to the motor angle information by adding the conversion result to the current motor angle information. Even anywhere within the output range of the angular information, it becomes possible to accurately correspond to the load angle information the angle information of the motor corresponding to the predetermined position.

According to the fourth aspect of the invention, the rotation is controlled through a predetermined gear ratio by the servo motor having the built-in incremental encoder that outputs a pulse signal at regular angular intervals according to the rotation of the drive shaft. In a position detection circuit that detects a predetermined position of the load, a counter that sequentially counts and outputs pulse signals output from the incremental encoder, a count value output from the counter, and the gear ratio based on the A frequency divider that outputs load angle information corresponding to the angle of the load rotated by a servo motor in accordance with a preset cycle, a count value that is sequentially output from the counter, and an output from the frequency divider. The angle information corresponding to the predetermined position of the load set in advance based on the load angle information Converted in accordance with the force is the count value,
A command generator that outputs angle information of the predetermined position according to the count value as detection command information, and a value of the detection command information output from the command generator and a count value sequentially output from the counter However, since it is equipped with a comparator that outputs a position detection signal when it becomes the same value, not only can it perform highly accurate position detection with an inexpensive configuration, but it can also be installed directly by installing a sensor or absolute encoder. Since it is not necessary to detect the position or angle of the load, the degree of freedom regarding the installation of the drive mechanism of the servo motor is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a position detection circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a measurement counter of the position detection circuit.

FIG. 3 is a graph for explaining the configuration of the position detection circuit in the second embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining a configuration of a conventional servo motor drive mechanism.

[Explanation of symbols]

1 ... Incremental encoder, 2 ... Counter,
3 ... Frequency divider, 4 ... Command generator, 5 ... Comparator, 6 ... Switch, 10, 15 ... Memory, 11 ...
Subtractor, 12 ... Electronic gear, 13 ... Adder, 14 ...
Periodic function generator

Claims (4)

[Claims] 1. A position detection circuit for detecting a predetermined position of a load whose rotation is controlled by a motor through a predetermined gear ratio, wherein angle information output means for sequentially outputting angle information of the motor according to rotation of the motor. And a change amount detecting means for detecting a change amount between the motor angle information inputted this time and the motor angle information inputted last time, and the change amount outputted by the change amount detecting means, to the angle change of the load. Based on the load angle change amount output from the change amount conversion unit, and the load angle information obtained last time, with respect to the motor angle information input this time. Load angle output means for outputting load angle information, and load angle information output from the load angle output means,
A cycle processing means for processing so that the load is outputted in accordance with a preset cycle; and a predetermined position detecting means for detecting a predetermined position of the load based on angle information of the load outputted from the cycle processing means. Characteristic position detection circuit. 2. The predetermined position detecting means is preliminarily input with load angle information corresponding to the predetermined position, and sequentially outputs the motor angle information and the load angle information output from the cycle processing means. The angle information of the load corresponding to the predetermined position to the angle information of the motor, the angle information of the motor output from the detection angle conversion unit, and the angle information output unit 2. The position detection circuit according to claim 1, further comprising position detection signal output means for comparing the angle information of the sequentially output motors and outputting a position detection signal when both angle information match. 3. The detected angle converting means obtains a difference between load angle information corresponding to the predetermined position and current load angle information output from the cycle processing means, and corresponds to the predetermined position. The position of the load angle information within the range between the minimum value and the maximum value of the load angle information output from the cycle processing means is determined,
It is determined whether the value of the preset period is added to or subtracted from the calculated difference according to the position, or whether the addition or subtraction is not performed, and the resulting value is determined based on the gear ratio. 3. The load angle information corresponding to the predetermined position is made to correspond to the motor angle information by converting the motor angle information and adding the conversion result to the current motor angle information. The position detection circuit described. 4. A position for detecting a predetermined position of a load which is rotationally controlled via a predetermined gear ratio by a servomotor having a built-in incremental encoder which outputs a pulse signal at equal angular intervals according to the rotation of a drive shaft. In the detection circuit, a counter that sequentially counts and outputs the pulse signals output from the incremental encoder, a count value output from the counter, and the gear ratio based on the gear ratio, and A load divider that outputs load angle information corresponding to a load angle according to a preset cycle, a count value that is sequentially output from the counter, and a load angle information that is output from the divider. Based on this, the angle information corresponding to the predetermined position of the preset load is changed according to the count value sequentially output from the counter. In other words, a command generator that outputs angle information of the predetermined position according to the count value as detection command information, a value of the detection command information output from the command generator, and a counter that sequentially outputs from the counter. A position detecting circuit comprising: a comparator that compares a numerical value and outputs a position detecting signal when the values are the same.