JPH05332857A - Load-torque measuring apparatus for stepping motor - Google Patents

Abstract

PURPOSE:To measure a load torque in high accuracy by storing the relation data of a driving current for the given torque with respect to predetermined characteristic information, collating the data with the characteristic information from the driving current at the actual load, performing judgment, and outputting the actual load. CONSTITUTION:A reference-load-torque generator 3 is connected to a reference stepping motor 1, and the torque is changed. A coil current iB- is detected with a current detecting part 10. The current is inputted into characteristic extracting part 13 through an amplifier 11 and a switch 12. The extracting part 13 extracts the corresponding relation between the maximum value of the driving current in a rise-up change section and the load torque as the torque vs. current data and stores the data into a reference value memory 14. Meanwhile, a real-machine mechanism part 2 is connected to the motor 2, and the switch 12 is changed. The apparatus is driven under the same conditions. The detected current from the detecting part 10 is inputted into a characteristic extracting part 15. The maximum current value is extracted as the characteristic information by the same way. In a collating and judging part 17, the two pieces of the characteristic information are collated, and the actual load torque is judged and outputted. Thus, the output torque can be accurately measured under the mounted state of the motor.

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 which enables highly accurate actual load torque measurement in a motor mounted state.

[0002]

2. Description of the Related Art A stepping motor can digitally control a rotational position (angle) and a rotational speed with high precision by a predetermined pulse, and this control can be performed by a microcomputer. It is used as a mechanical drive source. For example, in recent years, with rapid technological development, the market is expanding, and its application is in OA equipment such as FDD, HDD, printer, electronic typewriter, facsimile, PPC copier, recorder plotter, and FA equipment such as industrial robot. Is expanding rapidly. Despite the importance of measuring and controlling the load torque of the motor shaft in the development, manufacturing, and quality control of these stepping motor-mounted devices, it has been extremely difficult to perform such measurement with high accuracy. This is because, for example, when a spur gear reduction mechanism is used in the mechanism section after the motor, if the meshing state of the pinion gear attached to the motor output shaft and the first stage gear meshing with this gear is made shallow, the load torque is 100 (g-cm )
This is because the torque fluctuates greatly, for example, when it is deeper (pressed harder), it becomes 300 (g-cm). Further, the meshing of the other reduction gears is a variable factor although the influence of the meshing of the reduction gears decreases as the distance from the first stage increases. In addition, there is a problem that the load torque may vary greatly depending on the roundness (eccentricity) of the mechanical parts, the accuracy of the distance between the shafts, the assembly accuracy such as the parallelism in mechanical assembly, the tension of the timing belt and the wire, etc. Because.

Conventionally, as a method of measuring the magnitude of the torque generated in such a stepping motor (the magnitude of the torque required by the load for the motor), the shape is the same as that of the actually used motor, and a coil, a magnet, etc. are used. There is a method of mounting a dummy motor that is not included in the system under measurement (mechanical part), connecting a torque gauge to the motor output shaft provided on the motor pinion via a collet chuck, etc., and rotating the motor manually for measurement. is there. In addition, a stepping motor with the same specifications as the stepping motor actually used is mounted on the mechanism section with a motor specially manufactured as a dual axis specification with a torque measurement axis on the opposite output shaft side, and the torque gauge collet chuck is used for torque measurement. There is also a method of measuring by connecting to an axis. Further, attach a pulley to the motor output shaft, pull the thread wound around the pulley to pull the pulley radius r (cm), and the spring force F force.
There is a method of obtaining the load torque T (g-cm) from (g) as T = F × r. Furthermore, there is also a method of using a torque meter that utilizes the current / torque characteristics of a DC motor, or interposing a torque gauge between the motor and the load.

[0004]

As described above, various methods have been conventionally used as a method for measuring the torque of a motor, but it is difficult to measure with sufficient accuracy. That is, it is difficult to give an arbitrary rotation speed to the load by the method using the dummy motor or the method using the pulley and the spring back, and in the former method, the load torque caused by the side load due to the tilt of the torque gauge is The increase is inevitable, and the latter method also makes it difficult to attach the pulleys stably, and the side load effect is also inevitable.

In the method of using a stepping motor having the same specifications as the stepping motor to be actually used, since the rotor of the motor has a magnet, the holding torque (detent torque) of the magnet must be measured and the rotor must be measured. When turned, magnet rotation causes power generation in the stator coil, and this generated current causes dynamic braking (brake torque), and the inclination of the torque gauge becomes the side load of the motor bearing, which increases the load torque from the actual value. Accurate measurement is impossible.

Further, in the method utilizing the current / torque characteristic of the DC motor, it is necessary to remove the motor each time measurement is performed. In addition, since the load torque changes subtly due to the engagement of the pinion and gear when installing the motor, it is necessary to know how much torque the motor actually generates in the assembled actual machine. I can't.

As described above, with the conventional load torque measuring method, it is impossible to measure the torque generated from the motor with a high accuracy while the motor and the load are assembled. In other words, you want to know what the load torque is due to the variation in the meshing of the motor pinion of the motor used for mass production with the first-stage gear, and the tension of the motor timing pulley and timing belt. There was no choice but to analogize the torque. Therefore, it is not possible to know the difference between the torque generated by the motor and the load torque and the torque margin, and in mass production, it takes a great deal of time and cost to market such as voltage fluctuation test, temperature test, aging test, and printing test. The reality is that the products are shipped after checking the reliability. For example, when the mechanism does not move, whether the cause is insufficient torque margin of the designer or defective assembly adjustment at the manufacturing site, etc., there are constant troubles. I had to spend a lot of time investigating the defective parts.

For the above reasons, it is difficult to measure the load torque when the motor and the load are assembled.
Therefore, for example, in mass production, there is a problem that it is not possible to know the variation in load torque among individual products.

Therefore, an object of the present invention is to perform stepping which enables highly accurate measurement of load torque even when the motor and the load are coupled, that is, even when the motor itself used in mass production is mounted in the actual machine mechanism. An object is to provide a load torque measuring device for a motor.

[0010]

In order to solve the above-mentioned problems, a load torque measuring device for a stepping motor according to an aspect of the present invention includes a torque applied to the stepping motor and the torque applied when the torque is applied. Memory means for storing relational data of drive current flowing through the stepping motor with predetermined characteristic information, detecting means for detecting the drive current when an actual load is applied to the stepping motor, and the detecting means. Characteristic extracting means for extracting the characteristic information of the driving current, the characteristic information extracted by the characteristic extracting means and the relational data stored in the memory means are collated to output the actual load. Judgment means and drive the motor at a voltage that does not cause step out of the stepping motor during calibration, and measure the actual load during calibration. A driving means for driving the motor with a predetermined voltage, and a load torque measuring device for a stepping motor according to another aspect of the present invention include a torque applied to the stepping motor, and the stepping when the torque is applied. The relational data with the characteristic information defined by the integral value of the drive current flowing into the phase from the time when the current starts to flow into any phase of the motor to the time when the current starts to flow into the other phase. The memory means for storing the phase and the current from the start of the flow of current to any phase of the stepping motor when a real load is applied to the stepping motor until the start of the flow of current to another phase. Detecting means for detecting an integrated value of the drive current flowing into the device, feature extracting means for extracting the characteristic information of the drive current obtained by the detecting means, and feature extracting means for extracting the feature information. And feature information, the collated with the relationship data stored in the memory means, configured and a matching determination means for outputting said actual load.

[0011]

In the present invention, when the stepping motor is driven, the characteristic of the waveform of the drive current flowing into any phase is compared with the characteristic of the waveform of the drive current when a known torque is applied to measure the torque. In doing so, the drive voltage of the motor is optimized, for example, so that the motor does not step out. Further, the integral value of the current of a specific portion of the waveform of the drive current flowing into an arbitrary phase with respect to the pulse application time is set as the characteristic amount of the drive current. This integration section can be, for example, a section from when a current starts flowing in an arbitrary phase of the stepping motor to when a current starts flowing in another phase. Further, it is also possible to obtain an integrated value obtained by integrating only a portion of the drive current having a positive polarity with respect to a range not exceeding a predetermined fixed time, and use it as the characteristic amount of the drive current waveform.

[0012]

EXAMPLE An example of the load torque measuring device for a stepping motor according to the present invention will be described in detail below. The present invention focuses on the fact that the current (driving current) flowing through the coil of the stepping motor has unique characteristics such as a unique waveform and peak value corresponding to the load torque, and the actual load is measured based on this characteristic. To do. 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 obtained by measurement and stored, and when the actual machine mechanism unit is connected. The actual load is measured by measuring the drive current waveform under an arbitrary load condition and comparing the obtained coil current characteristic with the stored characteristic. At this time, in order to enable highly accurate measurement of the load torque, the stepping motor is supplied with a drive voltage that does not cause step out. Further, the drive current flowing in the coil is integrated only for a predetermined section to make the characteristics of the drive signal waveform noticeable.

By the way, the coil structure of the stepping motor has a monofilar winding (single winding) and a bifilar winding (2 windings).
There are two types of double winding), the former is driven by a bi-polar drive circuit and the latter is driven by a unipolar drive circuit. In addition, as the types of the excitation circuit in which only the portion of the drive circuit in which the current flows is extracted, there are a constant voltage method in which the coil is excited with a constant voltage, a two-voltage method in which the coil is excited with two kinds of voltages, and a constant voltage method. There is a constant current chopping method that controls the excitation current so that it flows through the coil. In either method, the current waveform changes (changes in characteristic information) depending on the magnitude of the torque.
Has been confirmed by experiments. In particular, it was confirmed that the change of the current waveform was remarkable in the constant voltage excitation unipolar drive and bipolar drive.

The frequency at which the current waveform is measured is 10
(PPS) or other low frequency to the maximum self-start frequency under load,
In some cases, it is possible to select up to the maximum continuous response frequency under load with the frequency slowed up. In particular, it has been found that a frequency region where a stable current waveform can be obtained while avoiding the resonance and random frequency regions is desirable. Although there are variations in the torque characteristics of mass-produced motors, the variations are ± 10% or less for PM type stepping motors and ± 5% or less for HB type stepping motors, so the measuring device according to the present invention is sufficient. Put to practical use. According to one experiment, in the spur gear reduction section of the receiving section mechanism of a mass-produced facsimile, the load torque is 100 to 130 (g-c) when the pinion gear of the motor output shaft and the first stage gear are properly meshed.
m), and when the motor pinion gear was brought close to the first-stage gear to be assembled, it was 250 to 300 (g-cm). In this way, variations in torque characteristics between individual motors are ± 5 ±
In reality, the variation due to the assembly and adjustment of the mechanical part is ± 100% compared to 10%.

FIG. 1 is a basic overall configuration diagram showing an embodiment of a load torque measuring device for a stepping motor according to the present invention. Each winding (bi-file coil) ΦA, ΦA-, of the stepping motor 1 (four-phase unipolar motor in this example)
One ends of .PHI.B and .PHI.B- are connected to the external power supply VM applied via the connector 5, and the other ends thereof are connected via the connector 6 to the switching transistors Q1, Q3, Q corresponding to the respective windings.
2, Q4 are connected. By operating the switching transistors Q1 to Q4 at a predetermined timing, the pulse supply to each winding is controlled and the excitation is switched. The switching transistors Q1 to Q4 form a drive circuit 7 that drives a stepping motor.

The controller 9 includes an oscillation circuit that generates a clock that serves as a reference for the pulse supply timing to the windings, a positioning circuit that determines the rotation angle (position) of the stepping motor, and the like. Clockwise rotation clock CCW, excitation mode signal, etc. are generated. The distribution circuit 8 receives the clock CLK and the excitation mode signal, and supplies a pulse for 2-2 phase excitation to each winding.

First, the reference load torque generator 3 is connected to the output shaft of the stepping motor 1 as a master motor, which is a non-defective motor whose motor specifications are fixed, via the coupling 4 to change the torque. .. At this time, motor drive voltage, motor drive frequency, excitation mode,
The switching transistor for switching the coil excitation and the accompanying coil counter electromotive force absorption circuit (not shown) are specified. The coil current also changes according to the torque change.
In order to measure the coil current, a current detection unit 10 (in this example, inserted in the winding ΦB-) inserted in any of the windings is provided to detect the coil current iB-. This coil current iB- is amplified by the amplifier 11, and the switch 12
Is supplied to the feature extraction unit 13 via the terminal S1.

The feature extraction in the feature extraction unit 13 is, for example, to extract the feature of the torque vs. current waveform, and various information (parameters) are used as the feature. For example, in FIG. 2, the load torque TL is used as a parameter,
The change of the coil current (driving current) i when changing to 0, 100, 200, 300 (g-cm) is shown. From this change (current waveform), it is not appropriate for the drive circuit of the stepping motor to be represented by an equivalent circuit composed of a series circuit of an inductance and a resistance as is generally known. As shown in FIG. In addition to R, it is obvious that the counter electromotive force equivalently generated for passing the input power to the secondary side (rotor) should be considered.

Now, when an appropriate voltage is applied to the phase of interest (self-phase current input point), the current of the relevant phase starts to rise rapidly. In particular, when the PM type motor is driven with an appropriate drive voltage, the current rises slowly and the maximum value i
After reaching P, it begins to decline. Since the motor is excited in two phases, the voltage starts to be applied to the 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 relevant phase, which is not clearly shown in the figure. After that, although it depends on the magnitude of the load torque, the coil current continues to decrease for a while and reaches the minimum value. After that, the current rapidly rises, and when it reaches the maximum (maximum) value, the current to the relevant phase is interrupted by the drive circuit (self-phase current interruption point).

As is apparent from the figure, the average value of the drive current does not change so much even if the load torque is changed, but the current change from the start of the current flow to the corresponding phase current input point to the other phase. Is remarkable. For example, when the data interpolation processing is performed by paying attention to the maximum value iP of the load torque and the current in the figure, the relationship shown in FIG. 3 is obtained. When the load torque TL = 0 (g-cm), iP = 25 (mA), T
When L = 300 (g-cm), iP = 60 (mA), and during this period, it is found that the current smoothly increases as the load torque increases. Since the timing of occurrence of this maximum value is substantially constant, for example, the current value at the time when 30% of the cycle has elapsed from the rise of the current can be used as the characteristic information.

As described above, the feature extraction unit 13 of FIG.
The correspondence relationship between the maximum value and the load torque in the current rising change section of the drive current output from the amplifier 11 is extracted as torque-current data. The feature extraction unit 1
The characteristic extracted in 3 is not limited to the above maximum value, but 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, 0% of no-load torque when the stepping torque of the motor is 100%.
5 points of%, 40%, 60% and 80% can be set. The characteristic information (torque vs. current maximum value information in this example) extracted in this way is stored as a reference value in the reference value memory 14 such as a ROM or a floppy disk.

On the other hand, when the actual machine mechanism portion 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 side and the motor driving condition of the master motor is set. 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.
It is sent to the feature extraction unit 15 via 2. Feature extraction unit 1
Reference numeral 5 receives the coil current from the amplifier 11, extracts the maximum value iP of the current as the characteristic information, and temporarily stores it in the measurement value memory 16.

The collation judging unit 17 responds to the synchronization signal from the controller 9 by reading the maximum value iP information read from the measured value memory 16 and the torque vs. current as shown in FIG. The actual load torque is judged and output by collating with the related data. For example, the feature extraction unit 1
When the maximum value iP obtained in 5 is 43 mA, it is determined that the actual load is 150 (g-cm) from the relationship of FIG.
The load torque data thus obtained is displayed on the display 18 and printed by the printer 19. The feature extraction units 13 and 15 can be shared. Although the motor used for calibration and the motor used for the actual machine are of the same type, it goes without saying that they are separate bodies.

The above embodiment is a configuration for extracting the characteristics of the current waveform, but in the case of a device having a relatively high power source impedance, the power source voltage changes due to the change of the current, so the voltage waveform is used instead of the current waveform. Waveforms can also be used. In the present invention, the characteristics of the drive current waveform of the motor due to the fluctuation of the torque are extracted by utilizing the above ip-TL characteristic.

In the specific load torque measuring device described above, it is understood that the load torque can be measured more efficiently when the stepping motor to be measured is driven at a constant voltage. However, in an actual motor application product, a constant current drive is used. The method is often used. Even in such a case, by supplying current to the motor from the drive circuit incorporated in the measuring apparatus according to the present invention, without removing the motor incorporated in the measured motor application product from the mechanism section, It is possible to measure the load torque required by the mechanical unit.

Based on the above, an embodiment of the present invention will be described in which the characteristics of the drive current waveform are made remarkable and the measurement sensitivity is improved. FIG. 5 shows a PM type stepping motor having a constant frequency (200 PPS) and a constant load torque (300 g).
Driving voltage is 6V, 7.5V,
The change of a current waveform when changing to 10V is shown. In the same figure, the current flowing when the above voltage is applied to an L, R series circuit having the same L and R values as the above motor is indicated by a broken line.

FIG. 6 shows the ratio η of the motor drive current to the current flowing in the L and R series circuits at an intermediate point between the drive current supply point in FIG. 5 and the other phase current supply point. It is shown as a function of E. Since the stepping motor is originally a motor with low efficiency, when the driving voltage is high or the frequency is low, the equivalent circuit behaves like a generally known series circuit of L and R. Therefore, the characteristics of the current waveform are unlikely to appear. On the other hand, when the driving voltage is low or the frequency is high, a non-negligible amount of electric power supplied to the winding of the motor has to be consumed for mechanical work. Therefore, the current waveform changes from that determined by the series equivalent circuit of L and R, and becomes a characteristic waveform as shown in FIG.

Therefore, the drive current flowing into the motor is smaller than the current flowing into the L, R series circuit having the same time constant as the motor. From the current input point of own phase to the current input point of other phase,
The ratio of the amount of current flowing into the L and R series circuit is
The lower the driving voltage is, the larger the driving voltage is. When the drive voltage is high after the other-phase current input point, the drive current rapidly increases. It turns out.

Further, FIG. 7 shows that the same motor has a frequency of 30.
0 and 300g load torque at pps and 100pps
The figure shows a comparison of current waveforms near the self-phase current injection point when driven at -cm. The following is found from FIG. 7. The change of the current waveform feature based on the change of the load torque is
It appears remarkably from the point of applying the self-phase current until a certain time has elapsed. In the case of this motor, the time constant of the motor coil is 5
Concentrate on time within 10 times. When the driving frequency is low, the current in the above portion is relatively large even in the unloaded state. This is because at low frequencies, the next pulse is applied while the rotor of the motor is completely stationary, so the torque required to accelerate the moment of inertia of the rotor and load system (measurement system in this case) is It is considered to be added.

In summary, it can be seen that it is desirable to drive the motor at a voltage as low as possible in order to increase the change in the drive current waveform of the stepping motor due to the load torque (increase the characteristic of the current waveform). However, if the drive voltage is lowered too much, the motor will step out and stop. FIG. 8 shows a voltage (step-out limit voltage) that causes step-out when the same motor is rotated without load as a function of the rotation frequency f. As a matter of course, the higher the frequency, the higher the out-of-step eye field voltage.

FIG. 9 shows an HB type motor (PJ55-A1 manufactured by Nippon Pulse Motor Co., Ltd.) with a frequency of 700 p.
It shows how the drive current waveform changes depending on the drive voltage when rotated at ps and a load torque of 3 Kg-cm. It can be seen that the current waveform does not have a remarkable maximum value, but exhibits the same tendency as that of the PM type motor.

FIG. 10 shows that the same motor has the same frequency and the driving voltage is constant, and the load torque is 0, 1, 2, 3K.
The change of the drive current waveform when changed to g-cm is shown.

FIG. 11 shows the relationship between the load torque TQ and the value Q obtained by integrating the portion where the drive current flowing into the motor is positive from the point where the self-phase current is applied to the point where the other-phase current is applied. From this, it can be seen that the load torque of the motor can be correctly obtained for the HB type by the characteristic amount of the drive current waveform obtained by the above method. Therefore,
In order to efficiently measure the load torque, it is necessary to adjust the driving voltage according to the required measurement frequency so that the characteristics of the current waveform become remarkable. It can be seen that when the frequency is lower than the step-out limit voltage in FIG. 8, it is better to lower the drive voltage accordingly. Note that it is apparent from FIG. 2 that the characteristic of the drive current is obtained by the above-mentioned means even in the case of the PM type motor.

FIG. 12 shows a drive current waveform when the motor is out of step. In the figure, the current waveforms in a plurality of adjacent sections are shown in an overlapping manner. From this, it is understood that when the motor goes out of step, the current waveform is not constant but alternately fluctuates. By utilizing this fact, the step-out state of the motor can be easily determined. Therefore, in order to make the characteristic of the drive current waveform based on the change of the load torque of the stepping motor remarkable, the drive voltage of the measured motor is set to such an extent that the motor does not step out at the required load torque and the required frequency. It is better to lower it. Specifically, at a required torque and frequency (and temperature), a limit voltage that causes step-out is calculated, and this voltage is multiplied by an appropriate coefficient to obtain a driving voltage. Further, the characteristic amount of the drive current waveform relates to the elapsed time of the drive current between the self-phase current input point and the other-phase current input point and within a certain time from the self-phase current input point. It turns out that it is good to use an integrated value. However, in the section in which the drive current has a negative value, the current accumulated in the coil is discharged before the self-phase current is applied, so that the current characteristic does not appear prominently. Therefore, this part is excluded from the integration interval. Especially HB
It will be understood that, in the case of the motor of the type, as shown below, it is better to perform the integration only in the section where the drive current is positive.

Next, an apparatus for measuring the temperature characteristic of the stepping motor will be described. FIG. 13 shows an example showing the temperature characteristics of the stepping motor. Using a PF42-48105 manufactured by Nippon Pulse Motor Co., Ltd., known drive frequency-output torque characteristics were measured for a case where the motor jacket temperature was 25 ° C and a case where the motor temperature was 48 ° C. From this, it can be seen that it is desirable to correct the temperature characteristics when the temperature change of the motor during measurement is large. In order to realize this, the characteristic amount of the drive current waveform of the motor may be measured not only with respect to the rotation frequency and the load torque as described above, but also with the temperature as a parameter. In this case, it is necessary to calibrate the feature quantity in advance with known torque and temperature. A specific example for this will be described later.

Next, an embodiment in which the load torque measuring device for a stepping motor according to the present invention is realized as a system to which a microcomputer is applied will be described in detail. Figure 1
4 shows an embodiment of the above system. Microcomputer (CPU) 113, ROM 11 on the bus BUS
2. The RAM 111 is arranged as in the case of a normal system. In addition, an appropriate interface I / F 117
The LCD / software switch drive unit 115 is controlled via the, to drive the LCD / software switch unit 114, and the interface I / F 118.
A keyboard 116 is connected and constitutes a man-machine interface. As a result, the measurement conditions are input, the instruction from the device side and the measurement result are displayed. Furthermore, GP-
Data can be exchanged with an external computer (personal computer) via the IB interface unit 122 or the RS232C interface 123. Also,
The bus includes an FDD control unit 120 that controls the FDD 121.
And the external interface 119 are connected.

Drive pulse generator 10 arranged on the bus
From 6, the drive timing for the measured motor 100 is generated in response to an instruction from the CPU 113. The drive circuit 101 for the unipolar type motor or the drive circuit 102 for the bipolar motor is selectively used as necessary. The drive circuit includes a power source (0 to 48 V, 8 Am) from the voltage variable power source 105.
ax), it can be configured by transistors Q1 to Q4 and the like as in the example shown in FIG. The measured motor 100 is driven by the drive circuit. As in the case of FIG. 1, the drive circuit is provided with current / voltage detection means 107 such as a resistor. The instantaneous value of the detected current is determined by the A / D converter at an appropriate sampling interval,
After being converted into a digital value, it is sequentially stored in the RAM 111 under the control of the DMA control unit 108. The sampling is executed by starting the A / D conversion according to an instruction from the trigger generator arranged on the bus. Furthermore, in order to synchronize the timing of sampling generated by the trigger generator with the timing of the motor drive pulse, the trigger generator receives a synchronization pulse from the pulse generator.

Prior to the measurement, the reference torque setting machine control unit 109 is controlled under the control of the CPU 113, and the drive circuit 104 drives the reference torque setting machine 103.
In the present embodiment, the drive voltage of the motor to be measured needs to be set appropriately in order to make the characteristics of the current waveform noticeable with respect to changes in the load torque. Therefore, the appropriately set voltage is supplied to the drive circuit from the variable voltage power supply 105 arranged on the bus.

Next, in the embodiment of FIG. 14, after calibrating the load torque-current waveform characteristics of the motor to be measured, the motor to be measured is connected to the actual load mechanism section and the load torque is measured. It will be explained using.

FIGS. 15 to 19 are flowcharts showing a processing procedure for applying a known load torque to the motor to be measured and obtaining the relationship (reference value) between the load torque and the characteristic amount of the current waveform. First, as shown in FIG. 15, measurement conditions are given to the device. Maximum frequency fH and minimum frequency fL for measurement
The ultimate maximum temperature TH, the optimum drive voltage EH to the drive circuit, the maximum load torque TQH to be measured, the minimum torque TQL and their increments Δf, ΔT0, ΔE, ΔTQ during measurement are designated. In response to these, the apparatus of the present embodiment first sets the frequency to the minimum value fL, the load torque to the maximum value TQH, and the power supply voltage to the maximum value EH to specify the measurement range (step S1). The reference value is measured, and when the setting is completed, the reference value is stored (step S2). The memory of the reference value is
It is executed by the procedure shown in FIG. First, the optimum drive voltage is determined (step S11). In this determination work, as shown in FIG. 17, the load torque TQ to be applied to the motor is first set to the maximum value TQH in order to prevent the motor from being out of step within the required measurement range (step S31). ). Next, the target value f0 of the measurement frequency is set to the measured minimum value fL (step S32). From this state, the following processing is performed to determine the optimum driving voltage at each frequency.

First, the drive voltage E is set to the set maximum value EH (step S33), and the rotation speed of the motor is increased to the target frequency by the slow start method (steps S34 to S36). In the process of increasing the rotation speed, timing is waited, the drive current waveform is checked (steps S37 and S38), and it is confirmed that the motor is not out of step (step S39). If step-out occurs even when the drive voltage is set to EH,
Stop the motor as an error. In step S40, if it is confirmed that the predetermined frequency f0 is reached,
In order to obtain the step-out limit of the drive voltage, the drive voltage E is gradually lowered while monitoring the drive current waveform (step S
41), check the current waveform (step S42),
Step-out is judged and step-out limit is measured (step S4)
3). Here, if step out occurs, the drive voltage at that time is
This is the step-out limit voltage.

Next, the temperature T of the motor is determined by the coating method or
It is measured by the resistance method (step S44). Then, the limit voltage is multiplied by (1 + α) using an appropriate coefficient α to obtain the optimum drive voltage. Then, it is stored in a file or a memory together with the parameters TQH, f, T at the time of measurement (step S45). Then, after increasing the target frequency by Δf0 (step S46), the above measurement is repeated. In step S47, the measurement of the required frequency range is completed, and when f0 becomes larger than fH, the motor is stopped (step S48), and the determination of the optimum drive voltage ends. When the optimum drive voltage is determined, the process returns to FIG. 16 again, and the reference value is stored while changing the load torque applied to the motor.

First, the load torque is set to the maximum value TQH (step S12). Then, the reference torque TQ is applied (step S13). In order to give a known load torque, perm torque manufactured by Koshin Rashin Co., Ltd. or the like can be used. This is to apply a known torque to a rotating shaft by using a hysteresis magnetic material and turning a dial to set a scale to a predetermined value. The dial can be set manually, but the dial may be automatically rotated from the device side by using a stepping motor or the like. After setting the torque to the desired value, fL, the lowest value within the range where the frequency f should be measured
(Step S14), and the measurement of the characteristics of the current waveform is started. The characteristic Q of the current waveform is extracted while driving the motor at the frequency f with the optimum driving voltage (driving voltage) Ea in the predetermined parameters TQH, f, T (step S15).
~ S17). The calculated feature amount Q is torque TQ, Ea,
f and T are stored as parameters (step S1)
8). Then, after the frequency is increased by Δf0 (step S19), the time is waited for Δt (step S2).
0), in step S21, the above measurement is repeated for the same torque until it is confirmed that the frequency has reached the desired maximum value fH. As a result, if the frequency is gradually increased from the low frequency, the motor is slowed up.

When the measurement of the desired frequency range for the same torque is completed, the motor is once stopped (step S21) and the torque is changed if necessary. That is, the torque TQ is reduced by ΔTQ (step S22), and then the above measurement is repeated. If it is determined in step S23 that the measurement for the torque in the entire range has been completed, the storage of the reference value is completed.

Returning to FIG. 15, if necessary, the temperature characteristic is measured and stored. That is, after increasing the target value T0 of the measured temperature by ΔT0 (step S3), the coil is energized (step S4) while the motor is kept stationary to raise the temperature of the motor to a required value. While measuring the temperature TM (step S5), energization is continued, and step S6 is performed.
In step S7, when the temperature of the motor reaches (or exceeds) the target value T 0, the reference value is stored again in step S7 until the measurement of the maximum temperature TH is completed.

Next, an embodiment for extracting the characteristics of the current waveform will be described. In the description of this embodiment, FIG.
It is easy to understand with reference to the examples relating to the measurement of the motor current waveform shown in FIG. This example is an HB type stepping motor PJ55-A manufactured by Nippon Pulse Motor Co., Ltd.
1, the load torque was measured at 0, 1, 2, 3 Kg-cm at a frequency of 700 pps. In FIG. 10, measurement is performed up to the self-phase current input point t0, the other-phase current input point t1, and the self-phase current cutoff point t2. In the present embodiment, the characteristic amount is represented by a current waveform from t0 to t1.
The drive current is integrated with respect to time only while the drive current is positive. However, when the drive frequency is low, the integration interval should be limited to a predetermined time from t0 in addition to the above logic.

FIG. 11 is a plot of the result of the above integration, with the horizontal axis representing the integrated value (= current waveform characteristic amount) and the vertical axis representing the load torque TQ. From this, it is understood that the current waveform characteristic amount / load torque characteristic of the HB stepping motor can be obtained by the above logic.
As described above, the current waveform characteristics can be obtained by the same method for the PM type motor as well.

FIG. 18 shows a flow chart for performing the current waveform feature extraction. The integration starts from t0 and is performed for an interval up to the integration limit tc. First, tc
First, tc is limited to a value obtained by multiplying the time constant τ of the electric system of the motor by an appropriate coefficient k (step S51). Furthermore, when tc exceeds the entry point t1 of the other phase current, this is limited to t1 (steps S52 and S53). Next, in carrying out the integration of the drive current,
The time t at which integration is performed is initialized to t0 (step S
54). Further, the integrated value S is also initialized (step S5
5), the drive current i (t) is measured (step S5)
6). When it is determined that the time has reached the time t at which integration is performed, it is determined whether i (t) is positive (step S
57). If the drive current i (t) is positive in step S57, it is added to the integrated value S (step S5).
8). If i (t) is negative, integration is not performed. When the processing at time t is completed, the time t at which processing should be performed next
Is increased by a predetermined increment Δt (step S59), and the process at the next time is performed. When it is determined in step S60 that the time t at which the processing is performed has reached the integration limit tc, the integration is terminated. The integrated value S obtained as a result of the above processing is set as the current waveform characteristic amount Q to be obtained (step S61). After the measurement of the reference value for the motor to be measured in the desired range is completed, it is convenient to rearrange the measured characteristic amount in the subsequent measurement of the load torque.

FIG. 19 shows a flow chart of the processing procedure for organizing the feature quantities. The optimum driving voltage Ea is measured as a function of frequency and temperature (step S71), and arranged /
It is stored (step S72). In subsequent measurements,
You can easily get the required value. For example, the maximum drive voltage Ea at an arbitrary temperature T is expressed as a function of the frequency f by appropriately using spline interpolation, Bessel interpolation, etc., and the coefficient is obtained. Next, each coefficient thus obtained is similarly interpolated with respect to the temperature T, and Ea can be arranged with respect to T and f by obtaining the coefficient. The results are organized as coefficients that represent these functions. Next, the load torque is obtained as a function of the current waveform feature quantity,
It is organized and stored (steps S73 and S74). At this time, it is convenient to make the frequency and temperature dependent. With the above, the preparation for the load torque measurement was completed. After that, the measurement can be performed with the measured motor mounted on the actual device under test.

The above-described effects of the present invention are remarkable in equipment mass-produced using the same type of motor. First, by calibrating the relationship between the load torque-current waveform characteristics of a typical motor, the load torque of the device can be easily measured within the manufacturing error of the motor. Therefore, it is possible to develop the applicable equipment, evaluate the quality, quantify problems in mass-production trials, inspect the production line, and have quantitative discussions about load torque between both development and manufacturing departments. Extremely large.

FIG. 20 shows the procedure for measuring the load torque. First, the maximum fH, the minimum fL, and the change width Δf of the measurement frequency are designated (step S101). After the frequency is initialized to the minimum value fL (step S102), the temperature is measured (step S103), and the optimum drive voltage (drive voltage)
Is determined and applied (step S104). Next, the motor is rotated at the frequency f (step S105), the characteristics of the drive current waveform are extracted (step S106), the load torque is measured (step S107), and stored (step S).
108). Then, the frequency is increased by Δf (step S109), and the load torque is measured again by the above procedure. By repeating the above processing until it is confirmed in step S110 that f becomes larger than fH, the frequency characteristic of the load torque in a state where the actual motor is mounted on the device under test within a predetermined range is obtained. Can be done. When the measurement is completed, stop the motor (step S
111), and the measurement result is appropriately displayed in the form of a graph, a table or the like (step S112).

Next, an application device of the load torque measuring device for a stepping motor according to the present invention will be described. Figure 21
Shows a state in which there is looseness in the mechanical part of the product in which the motor is mounted, and the state in which the load torque fluctuates with the rotation (as time passes) is measured. In general, the power output from the output shaft of the motor is transmitted to each part of the mechanism via many pinions / gears. Therefore, the fluctuation of the load torque does not always coincide with the rotation of the motor in a simple manner. Therefore, by dividing the pulse applied to the motor by displaying it as a marker and appropriately adjusting the dividing ratio, it is possible to match the cycle of the load torque fluctuation and the repetition cycle of the marker. As a result, the defective portion can be estimated in consideration of the gear configuration of the mechanism portion and the like, which has a great industrial effect.

FIG. 22 shows an embodiment for generating the marker. Frequency divider 30 for inputting motor drive pulse
21 is obtained by appropriately giving the frequency division ratio N of.

FIG. 23 shows another embodiment for obtaining the marker. In this embodiment, the PLL system is adopted.
The phase comparator 32 compares the motor drive pulse (frequency f) divided by N by the frequency divider 31 (f / N) with the amount proportional to the varying load torque. If the phase of the variation of the load torque advances, the frequency division ratio of the frequency divider 31 is lowered. On the contrary, when the phase that is proportional to the load torque is delayed, the division ratio is increased. As a result, the value of N can be automatically obtained as the output of the phase comparator 32. Further, the marker can be obtained as an output of the frequency divider 31.

[0056]

As described above, by using the stepping motor load torque measuring device of the present invention, the torque output from the stepping motor can be accurately measured with the stepping motor mounted. Therefore, at 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 section of the motor and the quality of the coupling state between the load mechanism section and the motor. ..

[Brief description of 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 change over time of a drive current flowing through a winding with a load applied to a stepping motor as a parameter.

FIG. 3 is a diagram showing the relationship between the maximum value iP of the drive current flowing through the winding obtained based on FIG. 2 and the load torque.

FIG. 4 is an equivalent circuit diagram of a drive circuit of a stepping motor.

FIG. 5 is a diagram showing changes in drive current when the drive voltage of the stepping motor is used as a parameter.

6 is a function of the drive voltage E of a ratio η of the motor drive current to the current flowing in the L and R series circuits at an intermediate point between the drive current supply point in FIG. 5 and the other phase current supply point. FIG.

FIG. 7 is a diagram comparing current waveforms near a self-phase current injection point when the same motor is driven at different frequencies and load torques.

FIG. 8 is a diagram showing a voltage that causes step-out (step-out limit voltage) as a function of a rotation frequency f when the same motor is rotated without a load.

FIG. 9 is a diagram showing how a drive current waveform changes according to a drive voltage.

FIG. 10 is a diagram showing changes in the drive current waveform when the drive voltage is constant and the load torque is changed for the same motor at the same frequency.

FIG. 11 is a value Q obtained by integrating a positive drive current flowing into the motor from a self-phase current input point to another-phase current input point.
It is a figure which shows the relationship with the load torque TQ with respect to.

FIG. 12 is a diagram showing a drive current waveform when the motor is out of step.

FIG. 13 is a diagram showing an example of temperature characteristics of a stepping motor.

FIG. 14 is a system configuration diagram showing an embodiment of the present invention.

FIG. 15 is a flowchart showing a processing procedure for applying a known load torque to the motor to be measured and obtaining a relationship (reference value) between the load torque and the characteristic amount of the current waveform.

16 is a flowchart showing a processing procedure for storing a reference value in FIG.

17 is a flowchart showing a processing procedure for determining an optimum applied voltage in FIG.

18 is a flowchart showing a processing procedure for obtaining a characteristic amount of the current waveform of the reference value in FIG.

FIG. 19 is a flowchart showing a processing procedure for organizing the feature quantities in FIG.

FIG. 20 is a flowchart showing a processing procedure for measuring load torque in the example of the present invention.

FIG. 21 is a diagram showing a state in which the mechanical section of the product in which the motor is mounted in the embodiment of the present invention has a backlash, and the load torque varies with rotation.

FIG. 22 is a configuration diagram for generating the marker in FIG. 21.

23 is another configuration diagram for obtaining the marker in FIG. 21. FIG.

[Explanation of symbols]

1 Stepping motor 2 Real machine mechanism 3
Reference load torque generator 4 Coupling 5,6
Connector 7 Drive circuit 8
Distribution circuit 9 Controller 10
Current detector 11 Amplifier 12
Switch 13, 15 Feature extraction unit 14
Reference value memory 16 Measured value memory 17
Collation determination unit 18 Display 19
Printer

Claims (9)

[Claims] 1. A memory means for storing relationship data between a torque applied to a stepping motor and predetermined characteristic information of a driving current flowing through the stepping motor when the torque is applied, and a memory means for storing the relationship data in the stepping motor. Detecting means for detecting the drive current when a load is applied, feature extracting means for extracting the characteristic information of the drive current obtained by the detecting means, and feature information extracted by the feature extracting means, Collation judging means for collating the relational data stored in the memory means and outputting the actual load, and for calibrating, driving the motor with a voltage that does not cause stepping out of the stepping motor And a driving means for driving the motor at a voltage determined at the time of calibration at the time of measurement, and a load torque for a stepping motor. Measuring device. 2. A torque applied to a stepping motor and a period from when a current starts flowing into an arbitrary phase of the stepping motor when the torque is applied to when a current starts flowing into another phase. Memory means for storing relational data with the characteristic information defined by the integral value of the drive current flowing into the phase, and a current to an arbitrary phase of the stepping motor when an actual load is applied to the stepping motor. From the start of the inflow to the start of the inflow of current to the other phase, the detection means for detecting the integrated value of the drive current flowing into the phase, and the drive current obtained by the detection means. Feature extraction means for extracting the feature information, feature information extracted by the feature extraction means and the relational data stored in the memory means, and a collation determination means for outputting the actual load. , The load torque measurement apparatus for a stepping motor, characterized in that it comprises an. 3. The load torque measuring device for a stepping motor according to claim 2, wherein the integration is performed within a predetermined time after a current starts to flow into an arbitrary phase. 4. The load torque measuring device for a stepping motor according to claim 2, wherein the integration is performed only when the current flowing into the phase has a predetermined polarity. 5. A memory means for storing relational data with predetermined characteristic information of a driving current flowing through the stepping motor when a plurality of different torques and rotational speeds are applied to the stepping motor, and an actual load on the stepping motor. Detecting means for detecting the drive current when given, feature extracting means for extracting the characteristic information of the drive current obtained by the detecting means, feature information extracted by the feature extracting means, A stepping motor load torque measuring device, comprising: collation judging means for collating the relational data stored in the memory means and outputting the actual load. 6. Memory means for storing relationship data with predetermined characteristic information of drive current flowing through the stepping motor when different torques and rotational speeds are applied to the stepping motor at different temperatures. A detection unit that detects the drive current when an actual load is applied to the stepping motor, a feature extraction unit that extracts the feature information of the drive current obtained by the detection unit, and a feature extraction unit that extracts the feature information. A load torque measuring device for a stepping motor, comprising: characteristic information and the relational data stored in the memory means; and collation determining means for outputting the actual load. 7. A memory means for storing relationship data between a torque applied to the stepping motor and predetermined characteristic information of a drive current flowing through the stepping motor when the torque is applied, and a memory means for storing the relationship data in the stepping motor. Detecting means for detecting the drive current when a load is applied, feature extracting means for extracting the characteristic information of the drive current obtained by the detecting means, and feature information extracted by the feature extracting means, Collation determining means for collating the relational data stored in the memory means and outputting the actual load; and means for measuring a change with time of the characteristic information obtained by the characteristic extracting means. Characteristic load torque measuring device for stepping motors. 8. A memory means for storing relational data between a torque applied to the stepping motor and predetermined characteristic information of a driving current flowing through the stepping motor when the torque is applied, and a memory means for storing the relationship data in the stepping motor. Detecting means for detecting the drive current when a load is applied, feature extracting means for extracting the characteristic information of the drive current obtained by the detecting means, and feature information extracted by the feature extracting means, Collation determination means for collating the relational data stored in the memory means and outputting the actual load, time when a driving pulse is applied to the stepping motor, and load obtained by the collation determining means are varied. And means for measuring the transmission delay characteristic of the load by comparing with the time when the load torque for the stepping motor is provided. measuring device. 9. A memory means for storing relationship data between a torque applied to the stepping motor and predetermined characteristic information of a driving current flowing through the stepping motor when the torque is applied, and a memory means for storing the relationship data in the stepping motor. Detecting means for detecting the drive current when a load is applied, feature extracting means for extracting the characteristic information of the drive current obtained by the detecting means, and characteristic information extracted by the characteristic extracting means, Collation determining means for collating the relational data stored in the memory means and outputting the actual load, load torque of the stepping motor and driving pulse applied to the stepping motor are frequency-divided by an arbitrary multiple. A load torque measuring device for a stepping motor.