JP3143620B2 - Load torque measuring device for stepping motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load torque measuring device for a stepping motor, and more particularly to a load torque measuring device for a stepping motor capable of measuring an actual load torque while the motor is mounted.

[0002]

2. Description of the Related Art A stepping motor can control a rotation position (angle) and a rotation speed digitally and precisely with a pulse, and can use a microcomputer. I have. For example, in recent years, technology has rapidly developed and the market is expanding, and FDDs, HDDs, printers, electronic typewriters,
The use of OA equipment such as facsimile machines, PPC copiers and recorder plotters and FA equipment such as industrial robots has been rapidly expanding. Although the measurement and management of the load torque on the motor shaft is important in the development, manufacture, and quality control of these stepping motor-equipped devices, it has conventionally been very difficult to perform the measurement with high accuracy. This is because, for example, when a flat gear reduction mechanism is used for a mechanism part after the motor, if the meshing state between the pinion gear attached to the motor output shaft and the first-stage gear meshing with this gear is made shallow, the load torque becomes 100 (g-g). This is because the torque greatly changes, for example, to 300 (g-cm) or deeply (when pressed strongly). Further, the meshing of the other reduction gears is a variable factor, although the effect is reduced as the distance from the first gear increases. In addition, there is a problem that the load torque greatly varies depending on the roundness (eccentricity) of the mechanical parts, the accuracy of the distance between the axes, the assembly accuracy such as the parallelism in the mechanical assembly, and the tension of the timing belt and the wire. Because.

Conventionally, as a method for measuring the magnitude of the torque generated in such a stepping motor (the magnitude of the torque required by the load by the motor), the shape is the same as that of an actually used motor, and the method has a coil, a magnet, and the like. No dummy motor is mounted on the system to be measured (mechanical unit), a torque gauge is connected to the motor output shaft provided on the motor pinion via a collet chuck, etc., and the motor is rotated manually to measure. is there. In addition, a motor that has the same specifications as the stepping motor actually used and has a torque measurement axis on the opposite side of the output shaft is also specially manufactured as a double-axis specification. There is also a method of measuring by connecting to an axis. Further, a pulley is attached to the motor output shaft, and the yarn wound on the pulley is pulled to pulley radius r (cm) and spring force F
There is a method of obtaining the load torque T (g-cm) as T = F × r from (g). There are also methods of using a torque meter utilizing the current / torque characteristics of a DC motor, and interposing a torque gauge or the like between the motor and the load.

[0004]

As described above, various methods have conventionally been used for measuring the torque of a motor, but it is difficult to measure the accuracy to a satisfactory degree. That is, it is difficult to apply an arbitrary number of rotations to the load using the method using the dummy motor or the method using the pulley and the spring burr, and in the former method, the load torque due to the side load effect due to the inclination of the torque gauge is reduced. The increase is unavoidable, and even in the latter method, it is difficult to install the pulley stably, and similarly, the influence of the side load is inevitable. Also, in a method using a motor having the same specification as the stepping motor to be actually used, the rotor of the motor has a magnet, so it is necessary to measure the magnet including holding torque (detent torque). Due to the rotation, power is generated in the stator coil, and the generated current causes power generation braking (brake torque), or the slope of the torque gauge becomes a side load of the motor bearing, causing the load torque to increase more than the actual value. Is impossible. Further, in the method using the current / torque characteristics of the DC motor, it is necessary to remove the motor every time measurement is performed. In addition, since the load torque varies slightly depending on the degree of engagement between the pinion and gear when installing the motor, it is actually necessary to know how much torque the motor generates in the assembled actual machine. Can not.

[0005] As described above, in the conventional torque measuring method, it is impossible to measure the torque generated from the motor with high accuracy when the motor and the load are assembled. In other words, if you want to know the variation in the engagement between the motor pinion and the first-stage gear of each motor used for mass production and the load torque due to the tension between the motor timing pulley and the timing belt, the load must be determined by means that deviates from the actual machine mounting by alternative means. There was no other way but to estimate the torque. Therefore, it is impossible to know the difference between the motor generated torque and the load torque and the torque margin.In mass production, it costs a great deal of time and money before shipping to the market, such as voltage fluctuation tests, temperature tests, aging tests, and printing tests. It is the fact that they are shipped after confirming their reliability. For example, when the mechanism does not move,
Whether the cause is insufficient torque margin of the designer or poor assembly adjustment at the manufacturing site, etc., troubles are constantly occurring, and even when investigating the cause, take time to find out whether the motor is defective and the torque is too low or the mechanical parts are defective. I had to investigate.

SUMMARY OF THE INVENTION It is an object of the present invention to measure a load torque for a stepping motor capable of measuring a load torque even when a motor itself used for mass production is mounted on an actual machine mechanism in which a motor and a load are coupled. It is to provide a device.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a load torque measuring device for a stepping motor according to the present invention controls a pulse supply to each winding, switches excitation, and drives the stepping motor to rotate. Means, a connector means to which each winding of the stepping motor is electrically connected, and current information flowing through at least one of the windings of the stepping motor to which a measuring load is applied is received and detected via the connector means. Current information detecting means,
A characteristic information extracting means for extracting predetermined characteristic information from the current information detected by the current information detecting means; and a reference value memory, wherein the current flows through at least one winding of a stepping motor to which a known load torque is applied. The characteristic information of the current is obtained via the connector means, the current information detecting means and the characteristic information extracting means, the relationship between the obtained characteristic information and the known torque is stored in the reference value memory, and is applied to a predetermined stepping motor. Based on the characteristic information of the current flowing through the at least one winding obtained through the connector means, the current information detecting means and the characteristic information extracting means when a measuring load is applied, the current value is stored in the reference value memory. An actual load is determined and output from the relationship between the load and the characteristic information.

[0008]

The present invention comprises a control means for rotatingly driving a stepping motor, and a structure for obtaining characteristic information of a current flowing through at least one winding of the stepping motor obtained via a connector means. The relationship between the characteristic information of the current flowing through the one winding of the stepping motor and the known torque is stored in a reference value memory, and the predetermined winding is obtained when a measured load is applied to the stepping motor. An actual load is determined and output from the relationship between the load and the characteristic information stored in the reference value memory based on the characteristic information of the flowing current.

[0009]

Next, the present invention will be described with reference to the drawings. According to the present invention, the current (drive current) flowing through the coil of the stepping motor has unique characteristics such as a unique waveform and a peak value corresponding to the load torque, and the actual load is measured based on these features. Therefore, as described above, the characteristics of the coil current obtained when the load torque generated from the reference load torque generator is applied to the stepping motor in advance are measured and stored, and the characteristics when the actual machine mechanism unit is coupled are obtained. The actual load can be measured by measuring the drive current waveform in an arbitrary load state and comparing the obtained coil current characteristics with the stored characteristics.

The coil structure of the stepping motor includes a monofilar winding (single winding) and a bifilar winding (2 winding).
The former is driven by a bibolar drive circuit, and the latter is driven by a unipolar drive circuit. In addition, the types of the excitation circuit in which only the portion of the drive circuit through which the current flows are extracted include a constant voltage method in which the coil is excited at a constant voltage, a two-voltage method in which the coil is excited at two different voltages, and a constant voltage method. There is a constant current chopping method that controls the excitation current to flow through the coil. In either method, the current waveform changes (changes in characteristic information) depending on the magnitude of the torque.
Was confirmed by experiments. In particular, it was confirmed that the change of the current waveform was remarkable in the unipolar and bipolar driving of the constant voltage excitation.

The frequency for measuring the current waveform is 10
(PPS) and other low frequencies to the highest self-start frequency under load,
In some cases, it is possible to achieve a maximum continuous response frequency under load in which the frequency is slowed up. In particular, it has been found that a frequency region in which a stable current waveform avoiding the resonance and tuned frequency regions is obtained is desirable. The torque characteristics of mass-produced motors vary, but the variation is
Since it is ± 10% or less for a mold stepping motor and ± 5% or less for an HB type stepping motor, the measuring apparatus according to the present invention is sufficiently practical. According to one experiment, the load torque is 100 to 130 (g-cm) when the pinion gear of the motor output shaft and the first stage gear are properly engaged in the spur gear reduction unit of the receiving unit mechanism of the mass-produced facsimile. In this case, when the motor pinion gear was assembled close to the first gear, the weight became 250 to 300 (g-cm). Thus, the variation in torque characteristics between individual motors is ± 5 to ± 10
± 1% variation due to assembly and adjustment of mechanical parts
The fact is that there is as much as 00%. That is, the variation in the torque characteristics between the individual motors between the stepping motor used to obtain the relationship between the known torque and the characteristic information and the actual stepping motor actually assembled in a device such as a facsimile etc. It is smaller than the variation due to assembly and adjustment, and does not cause a substantial problem of measurement accuracy even when measurement is performed using a separate motor.

FIG. 1 is an overall configuration diagram showing an embodiment of a load torque measuring device for a stepping motor according to the present invention. Each winding (bifile coil) ΦA, ΦA-, Φ of stepping motor 1 (four-phase unipolar motor in this example)
B, .PHI.B- are connected at one end to an external power supply VM applied via a connector 5, and at the other end to switching transistors Q1, Q3, Q
2 and Q4 are connected. The pulse supply to each winding is controlled by operating the switching transistors Q1 to Q4 at a predetermined timing, and the excitation is switched. The switching transistors Q1 to Q4 constitute a drive circuit 7 for driving a stepping motor.

The controller 9 controls a clock (CLO shown in FIG. 2) as a reference of a pulse supply timing to the winding.
CK), a clock circuit for clockwise rotation CW, a clock circuit for counterclockwise rotation CC including a positioning circuit for determining the rotation angle (position) of the stepping motor, etc.
W, generates an excitation mode signal. The distribution circuit 8 receives the clock CLK and the excitation mode signal, and supplies pulses SΦA, SΦB, S in the 2-2 phase excitation to each winding as shown in FIG.
Switching transistor Q to supply ΦA- and SΦB-
1 to Q4 are controlled. The general currents iA, iB, iA- and iB- flowing through the windings .PHI.A, .PHI.B, .PHI.A- and .PHI.B- by the pulses thus supplied are shown in FIG.

First, the reference load torque generator 3 is coupled via the coupling 4 to the output shaft of the stepping motor 1 as a master motor, which is a non-defective motor whose motor specifications have been determined, to change the torque. . At this time, the motor drive voltage, motor drive frequency, excitation mode,
A switching transistor for coil excitation switching and an accompanying coil back electromotive force absorption circuit (not shown) are specified. The coil current also changes in response to the torque change,
For the measurement of the coil current, a current detection unit 10 (in this example, inserted into the winding ΦB-) inserted into an arbitrary winding of each winding is provided to detect the coil current iB-. This coil current iB- is amplified by the amplifier 11 and supplied to the feature extraction unit 13 via the terminal S1 of the switch 12. The feature extraction in the feature extraction unit 13 is for extracting the features of the torque-current waveform, and the features include various information (parameters). For example, FIG. 3 shows that the load torque TL is used as a parameter and 0, 100, 200, 300 (g−c).
m) and the change of the coil current (drive current) when it is changed. From this change (current waveform), it is not appropriate to express the drive current of the stepping motor by an equivalent circuit composed of a series circuit of inductance and resistance, as is generally known. It is clear that the equivalent back electromotive force to pass to the secondary side (rotor) should be considered.

Now, when an appropriate voltage is applied to the phase of interest (the current-phase current input point), the current of the relevant phase starts to rise rapidly. Eventually, the current rises slowly, reaches a maximum value iP, and then starts decreasing. Since the motor is excited in two phases, the voltage starts to be applied to other phases in the middle of the period in which the voltage is applied to the corresponding phase (the other-phase current input point). At this point, a slight constriction occurs in the current waveform of the corresponding phase, although not explicitly shown in the figure. Thereafter, although depending on the magnitude of the load torque, the coil current continues to decrease for a while and reaches a minimum value. Thereafter, the current rapidly increases, and when the current reaches a maximum (maximum) value, the current to the corresponding phase is interrupted by the drive circuit (the current-phase current interrupt point). As is clear from the figure, the average value of the drive current is
Even if the load torque is changed, the current does not change much, but the current change from the start of the current flow to the relevant phase to the input point of the other phase current is remarkable. For example, when the data interpolation processing is performed while paying attention to the maximum value iP of the load torque and the current in the drawing, the relationship shown in FIG. 4 is obtained. Load torque TL
= 0 (g-cm), iP = 25 (mA), TL =
When it is 300 (g-cm), iP is about 60 (mA), and during this time, it is found that the current increases smoothly as the load torque increases. Since the timing at which the maximum value occurs is substantially constant, for example, a current value at the time when 30% of the period elapses from the rise of the current can be used as the characteristic information.

As described above, the feature extraction unit 13 in FIG.
The correspondence between the maximum value and the load torque in the current rise change section of the drive current output from the amplifier 11 is extracted as torque-current data. The feature extraction unit 1
The feature extracted in 3 is not limited to the above-mentioned maximum value, and characteristic information can be arbitrarily selected and used in relation to the load torque. The load torque generated from the reference load torque generator 3 is, for example, assuming that the motor out-of-step torque is 100%, the no-load torque is 0%, and the load torque is 20%.
%, 40%, 60%, and 80%. The characteristic information (torque-current maximum value information in this example) thus extracted is stored in a reference value memory 14 such as a ROM or a floppy disk as a reference value.

On the other hand, when the actual machine mechanism 2 is coupled to the stepping motor 1 by the coupling 4 to measure the actual load, the switch 12 is switched to connect to the terminal S2, and the motor driving conditions of the master motor are determined. Set the same conditions. The drive current detected by the current detector 10 is amplified by the amplifier 11 and then amplified by the terminal S of the switch 12.
2 to the feature extraction unit 15. Feature extraction unit 1
5 receives the coil current from the amplifier 11, extracts the local maximum value iP of the current as the characteristic information, and temporarily stores it in the measured value memory 16. The collation judging section 17 compares the maximum value iP information read from the measured value memory 16 in response to the synchronization signal from the controller 9 with the torque-current relation data as shown in FIG. Are compared, and the actual load torque is determined and output. For example,
If the maximum value iP obtained by the feature extraction unit 15 is 43 mA, it is determined that the actual load is 150 (g-cm) from the relationship in FIG. The load torque data thus obtained is displayed on the display 18 and printed by the printer 19. Note that the feature extraction units 13 and 15 can be shared. Further, although the motor used for calibration and the motor used for the actual machine are of the same type, they are, of course, separate bodies. That is, the stepping motor 1 used for calibration in which the reference torque generator 3 is coupled via the coupling 4 and the stepping motor 1 in which the actual machine mechanism 2 to be measured is coupled have the same specifications. Is another stepping motor, and as described above, the stepping motor used to obtain the relationship between the known torque and the characteristic information is the same as the actual stepping motor actually assembled in a device such as a facsimile. In the case of the specification, the variation in the sensor characteristics among the individual motors is smaller than the variation due to the assembling and adjustment of the mechanical unit, and there is no substantial problem of the measurement accuracy even when the measurement is performed by a separate motor.

The above embodiment is directed to the extraction of the characteristics of the current waveform. However, in the case of a device having a relatively high power supply impedance, the power supply voltage changes due to a change in the current. Waveforms can also be used.

FIG. 5 is a block diagram showing one configuration example of the feature extraction units 13 and 15 in the embodiment of FIG. In this example, the current from the amplifier 11 through the buffer amplifier 51 in response to the operation of the switch S1 that is closed momentarily after a certain time (about 3 ms in this example) from the “self-phase current input point” via the diode D The capacitor C is charged,
The approximate value of the maximum value iP is held. The capacitor C is periodically discharged by the switch S2 (at the input of the self-phase current) in preparation for the measurement in the next period. The potential of the capacitor C is buffered by the buffer amplifier 52 and output as a drive current holding value (maximum value information). FIG. 6 shows the relationship between these signal waveforms and timing. In FIG. 5, the switch S2 is closed momentarily at the self-phase current input point, the capacitor C is discharged, and the switch S1 is closed from the self-phase current input point to the other-phase current input point, so that in this section, The capacitor C is charged to the maximum value of the drive current by the diode D, and can maintain the maximum value iP. This relationship is shown in FIG.

FIG. 8 shows an example in which a load torque measuring device for a stepping motor according to the present invention is configured based on computer control. A control signal and a data signal from the CPU 111 are transmitted via the bus BUS, and conversely, a signal is transmitted to the CPU 111 via the bus. The ROM 110 stores a program for controlling the main measurement processing procedure.
The CPU 111 supplies a control signal to each unit based on this program. Power from a variable voltage power supply 103 controlled by the CPU 111 is supplied to the drive circuit 102, and drive pulses are supplied to the motor 101. The driving pulse is supplied to the driving circuit 102 from the pulse generator 104 whose driving timing is controlled by the CPU 111.
The drive current flowing through the drive circuit 102 is
(Corresponding to the current detection unit 10 in FIG. 1),
The signal is converted into a digital signal by the D converter 106, and is sequentially stored in the RAM 109 via the bus under the control of the DMA control unit 108. The operation timing of the A / D converter 106 is controlled by a trigger signal generated from a trigger generator 107 in response to a synchronization signal from the pulse generator 104. That is, the timing of the sampling generated from the trigger generator 107 is synchronized with the timing of the motor drive pulse. Instruction information from the outside is input from the keyboard 116, and the interface (I / F) 1
15 to constitute a man-machine interface. Similarly, the CRT 114 is connected via the interface 113.
Is connected, and data is exchanged with an external computer via the GP-IB interface 112.

FIG. 9 shows an example in which the feature extraction units 13 and 15 in the embodiment of FIG. 1 are realized by a neural network. In FIG. 9, a sample value of the drive current and a temperature condition are given to an input layer having an appropriate number of elements. Each output of the input layer is coupled to an intermediate layer of the appropriate number of elements.
The output of the middle layer is further coupled to an output layer of an appropriate number of elements. A bias from a bias element is supplied to each of the intermediate layer and the output layer. As we all know,
In a neural network, an appropriate teacher signal is given and learning is repeated, so that when a similar pattern is given to an input layer, an appropriate output is made according to the result of learning. The algorithm used for learning is
A back propagation method or the like can be used.
In this embodiment, in the learning stage, a plurality of sample values of the drive current when a known torque is applied to the motor to be measured are given to the input layer, and the temperature of the motor to be measured is given. The output from the output layer is compared with the known torque given as a teacher signal.If the learning is repeated for a plurality of torques, the neural network calculates the output torque of the motor to be measured, that is, the load torque from the drive current waveform. Be able to measure. Similarly, by additionally adding a power supply voltage or the like to the input layer (not shown), learning and measurement can be performed on the efficiency of the motor including the measured motor or the device including the drive circuit. According to the present embodiment, even when the characteristics of the current waveform do not appear so remarkably as seen when, for example, the motor is driven in a one- or two-phase drive or fine step drive, from the characteristics of the neural network, It is effective.

As described above, according to the present invention, for example, in the carriage mechanism of the printer, not all the strokes of the carriage have a uniform load torque, but there are heavy portions and light portions such as during dot printing. Therefore, if a synchronization signal similar to the motor drive pulse train is used, it is possible to measure the load torque change curve for all the strokes in which part of the entire stroke is in what kind of load torque state by sampling processing. Further, by providing the load current waveform peak hold function, it is possible to know the load torque at the heaviest point in the entire stroke of the carriage. Further, when the apparatus according to the present invention is used as a production inspection and quality control machine,
For each serial number of the actual machine under production, it can also be used as a lot management recorder of the load torque level of each machine produced. In addition, the matching determination unit 17
If the GO / NG function is provided, it can also be used as a determination device for the adjustment state of the equipment assembly including the motor.

[0023]

As described above, the load torque measuring device for a stepping motor according to the present invention measures the torque and the characteristic parameters of the stepping motor driving current or voltage in advance and determines the relationship between the torque and the driving current / voltage characteristic information. The torque vs. characteristic information relation data indicating that is obtained, the characteristic parameters when an actual load is applied to the stepping motor mounted on the actual machine mechanism are measured, and the obtained characteristic parameters are compared with the torque versus characteristic information relation data. Since the actual load is measured by collation, it is possible to measure the load torque required by the mechanism equipped with the stepping motor without disassembling the mechanism. As a result, in each stage from the development stage of the stepping motor application device to the mass production, it is possible to objectively grasp the characteristics of the load mechanism of the motor and the quality of the connection between the load mechanism and the motor. .

That is, according to the present invention, the motor itself to be mounted by the actual machine under development or the actual machine under mass production does not require a specially manufactured motor and does not add a special jig. The load torque on the motor output shaft can be quantified and measured numerically. As a result, the following effects are obtained. (1) Although the torque generated by the motor was quantified, the load torque can be quantified in addition to this, making it possible to clarify the difference in the torque margin and to enable stable mass production of stepping motor applied equipment without torque trouble. Becomes (2) By specifying the minimum and optimal torque margin,
Eliminating over-spec of the motor makes it possible to reduce the size of the motor, the size of the equipment, and the cost. (3) Factors affecting the load torque of each part of the equipment (part accuracy,
Factors such as backlash, timing belt and wire tension, roller pressing, etc. can be analyzed and rational design, production, and adjustment can be performed. (4) The effect on the load torque and the load torque distribution of the mechanism that drives the stepping motor and the part that operates in synchronization with the stepper motor can be analyzed, so that a rational design is possible.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a load torque measuring device for a stepping motor according to the present invention.

FIG. 2 is a diagram showing a pulse applied to each winding of a stepping motor and a drive current flowing through each winding in the embodiment of FIG. 1;

FIG. 3 is a diagram showing a temporal change of a drive current flowing through a winding with a load applied to a stepping motor as a parameter.

FIG. 4 is a diagram showing a relationship between a maximum value iP of a drive current flowing through a winding obtained based on FIG. 3 and a load torque.

FIG. 5 is a circuit diagram showing a configuration example of feature extraction units 13 and 15 in the embodiment of FIG. 1;

6 is a diagram for explaining the operation of the configuration example circuit diagram of FIG. 5;

FIG. 7 is a diagram for explaining another operation of the circuit diagram of the configuration example of FIG. 5;

FIG. 8 is a configuration diagram of an example in which a load torque measuring device for a stepping motor according to the present invention is controlled by a computer.

9 is a configuration diagram in which the feature extraction units 13 and 15 in the embodiment of FIG. 1 are realized by a neural network.

[Explanation of symbols]

1,101 Stepping motor 2 Actual machine mechanism 3
Reference load torque generator 4 Coupling 5, 6
Connector 7, 102 Drive circuit 8
Distribution circuit 9 Controller 10, 105
Current detector 11 Amplifier 12
Switches 13 and 15 Feature extraction unit 14
Reference value memory 16 Measurement value memory 17
Collation judgment unit 18 Display 19
Printer 103 Variable voltage power supply 104
Pulse generator 106 A / D converter 107
Trigger generator 108 DMA controller 109
RAM 110 ROM 111
CPU 112 GP-IB interface 113, 115 Interface 114 CRT 116 Keyboard

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-55-71196 (JP, A) JP-A-61-17923 (JP, A) JP-A-61-256218 (JP, A) JP-A-61-256 155826 (JP, A) JP-A-2-246793 (JP, A) JP-A-2-181624 (JP, A)

Claims (5)

(57) [Claims] 1. A control means for controlling a pulse supply to each winding and switching excitation to drive a stepping motor to rotate, a connector means for electrically connecting each winding of the stepping motor, and a measuring load. Current information flowing through at least one of the windings of the stepping motor is received via the connector means, and current information detecting means for detecting, and predetermined characteristic information from the current information detected by the current information detecting means. The connector means, the current information detecting means, and the characteristic information extracting means, comprising: characteristic information extracting means for extracting; and a reference value memory, wherein characteristic information of a current flowing through at least one winding of the stepping motor to which a known load torque is applied is obtained. The relationship between the obtained characteristic information and the known torque is stored in the reference value memory, and a predetermined stepping mode is obtained. The characteristic value of the current flowing through the at least one winding obtained through the connector means, the current information detecting means and the characteristic information extracting means when a load to be measured is applied to the reference value memory is stored in the reference value memory. A load torque measuring device for a stepping motor, wherein an actual load is determined and output from a relationship between a set load and characteristic information. 2. The data stored in the reference value memory is characteristic information of the drive current when a plurality of known torques are applied, and is relational data converted into continuous data by interpolation processing. The load torque measuring device for a stepping motor according to claim 1, wherein: 3. The method according to claim 1, wherein the characteristic information is a maximum value of a current rise change section of the drive current.
4. A load torque measuring device for a stepping motor according to claim 1. 4. The feature extracting means comprises: an input layer to which the drive current is applied; an intermediate layer to which each output of the input layer is supplied; and an output layer in which outputs of the intermediate layer are combined.
In the learning step, a plurality of sample values of the drive current when a torque of a known torque is given to the motor to be measured is given to the input layer, and the output of the output layer is compared with the known torque given as a teacher signal. The load torque measuring device for a stepping motor according to claim 1, comprising a neural network configured as described above. 5. The load torque measuring device for a stepping motor according to claim 1, wherein the stepping motor is driven by a unipolar drive circuit or a bipolar drive circuit of a constant voltage excitation.