JP3075839B2 - 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 accurately measuring an actual load torque while the motor is mounted.

[0002]

2. Description of the Related Art A stepping motor can digitally control a rotational position (angle) and a rotational speed with a predetermined pulse digitally and precisely, and this control can be performed by a microcomputer. It is used as a mechanism drive source. For example, in recent years, the market is expanding with rapid technological development, and its applications are OA equipment such as FDD, HDD, printer, electronic typewriter, facsimile, PPC copier, recorder plotter and FA equipment such as industrial robot. Are expanding rapidly. Although the measurement and management of the load torque of 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 gear meshing with this gear is made shallow, the load torque becomes 100 (g-cm). )
This is because the torque greatly fluctuates, for example, when it is deeper (when it is strongly pressed), it becomes 300 (g-cm). 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 of measuring the magnitude of the torque generated by 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
From (g), there is a method of obtaining the load torque T (g-cm) as T = F × r. Furthermore, there are 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.

In a method using a motor having the same specification as that of an actually used stepping motor, since the rotor of the motor has a magnet, it is necessary to measure the torque including the holding torque (detent torque) of the magnet. When the magnet is turned, power is generated in the stator coil by the rotation of the magnet. This generated current causes power generation braking (brake torque), and the inclination of the torque gauge becomes a side load of the motor bearing, which increases the load torque more than actual. Accurate measurements are not possible.

Further, in the method utilizing the current / torque characteristics of a 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.

As described above, in the conventional load 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 mechanical parts do not move, troubles such as whether the torque margin of the designer is insufficient or assembly adjustment failure at the manufacturing site are constant, and when investigating the cause, the motor is defective and the torque is too low. We had to take a long time to investigate the defective parts.

For the above reasons, it is difficult to measure the load torque when the motor and the load are assembled.
For this reason, for example, when mass production is performed, there is a problem that variation in load torque between individual products cannot be known.

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

[0010]

To solve the above-mentioned problems, a load torque measuring device for a stepping motor according to the present invention employs the following characteristic configuration. (1) Memory means for storing relation 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 an actual load applied to the stepping motor. Detection means for detecting the drive current when given, feature extraction means for extracting the feature information of the drive current obtained by the detection means, feature information extracted by the feature extraction means, and the memory Collation determination means for collating the relation data stored in the means and outputting the actual load;
When calibrating, the stepping motor drives the motor at a voltage set to a value obtained by multiplying a critical voltage at which the stepping motor does not lose synchronism by a predetermined count, and at the time of actual load measurement, driving the motor at the voltage determined at the time of calibration. Means for measuring the load torque of a stepping motor. (2) The torque applied to the stepping motor and the time between when the current starts flowing into an arbitrary phase of the stepping motor when the torque is applied and when the current starts flowing into another phase. A memory means for storing data relating to characteristic information defined by an integral value of the driving current flowing into the phase; and a current flowing into an arbitrary phase of the stepping motor when an actual load is applied to the stepping motor. From the start until the current starts flowing into another phase, a detecting means for detecting an integrated value of the driving current flowing into the phase, and the characteristic of the driving current obtained by the detecting means. Feature extracting means for extracting information; and matching determining means for comparing the feature information extracted by the feature extracting means with the relational data stored in the memory means and outputting the actual load. Load torque measuring device for a stepping motor comprising Te. (3) The load torque measuring device for a stepping motor according to (2), wherein the integration is performed within a predetermined time after the current starts flowing into an arbitrary phase. (4) The load torque measuring device for a stepping motor according to the above (2), wherein the integration is performed only when the current flowing into the phase has a predetermined polarity. (5) Data related to first characteristic information extracted by a predetermined means from a first drive current flowing through the stepping motor when a plurality of different torques and rotation speeds are given to the stepping motor is stored. Memory means, a detecting means for detecting a driving current when an actual load is applied to the stepping motor, a characteristic extracting means for extracting characteristic information of the driving current obtained by the detecting means, and a known means for the stepping motor. Using the second feature information extracted by the predetermined means, the second drive current when the rotation speed and the actual load are applied is compared with the relation data stored in the memory means. And a collation judging means for outputting the actual load, and a load torque measuring device for a stepping motor. (6) first characteristic information extracted by predetermined means from a first drive current flowing through the stepping motor when a plurality of different torques and rotation speeds are given to the stepping motor at a plurality of different temperatures; Memory means for storing the relationship data of, a detecting means for detecting a drive current when an actual load is applied to the stepping motor, a feature extracting means for extracting feature information of the drive current obtained by the detecting means, The second drive current of the stepping motor when the known temperature, the number of rotations and the actual load are given,
Using the second feature information extracted by the predetermined means, to check the relational data stored in the memory means, and to output the actual load;
A load torque measuring device for a stepping motor, comprising: (7) 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 an actual load applied to the stepping motor. Detection means for detecting the drive current when given, feature extraction means for extracting the feature information of the drive current obtained by the detection means, feature information extracted by the feature extraction means, and the memory Collation determination means for collating the relation data stored in the means and outputting the actual load;
A means for measuring a change over time of the characteristic information obtained by the characteristic extracting means. (8) memory means for storing relational data between the torque applied to the stepping motor and predetermined characteristic information of the drive current flowing through the stepping motor when the torque is applied; Detection means for detecting the drive current when given, feature extraction means for extracting the feature information of the drive current obtained by the detection means, feature information extracted by the feature extraction means, and the memory Collation determination means for collating the relation data stored in the means and outputting the actual load;
Means for measuring the transmission delay characteristic of the load by comparing the time at which the drive pulse is applied to the stepping motor with the time at which the load varies by the comparison and determination means, Torque measuring device. (9) Memory means for storing relational 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 an actual load applied to the stepping motor. Detection means for detecting the drive current when given, feature extraction means for extracting the feature information of the drive current obtained by the detection means, feature information extracted by the feature extraction means, and the memory Collation determination means for collating the relation data stored in the means and outputting the actual load;
A load torque measuring device for a stepping motor, comprising: means for comparing the change over time of both the load torque of the stepping motor and the drive pulse applied to the stepping motor divided by an arbitrary multiple.

[0011]

According to the present invention, when a stepping motor is driven, the torque characteristic is measured by comparing the characteristic of the waveform of the driving current flowing into an arbitrary phase with the characteristic of the waveform of the driving current when a known torque is applied. In doing so, the drive voltage of the motor is optimized, for example, so that the motor does not step out. In addition, the integrated value of the current of a specific portion related to the pulse application time in the waveform of the drive current flowing into an arbitrary phase is defined as the characteristic amount of the drive current. This integration section can be, for example, a section from when a current starts flowing to an arbitrary phase of the stepping motor to when a current starts flowing to another phase. Furthermore, an integrated value obtained by integrating only a portion of the drive current having a positive polarity with respect to time within a range not exceeding a predetermined time may be obtained as a feature amount of the drive current waveform.

[0012]

Next, an embodiment of a load torque measuring device for a stepping motor according to the present invention will be described in detail. The present invention focuses on the fact that the current (drive current) flowing in the coil of the stepping motor has a unique characteristic such as a unique waveform and a peak value corresponding to the load torque, and the actual load is measured based on this characteristic. Is what you 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 measured and stored, and the characteristics when the actual machine mechanism unit is coupled are obtained. The actual load is measured by measuring the drive current waveform under an arbitrary load condition and comparing the obtained coil current characteristics with the stored characteristics. At this time, in order to enable high-accuracy measurement of the load torque, a drive voltage that does not cause loss of synchronism is supplied to the stepping motor. In addition, the drive current flowing through the coil is integrated for a predetermined period to make the characteristic of the drive signal waveform remarkable.

Incidentally, 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.
Has been confirmed by experiments. In particular, it was confirmed that the change in the current waveform was remarkable in the unipolar and bipolar driving with 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,
Depending on the case, it is possible to select up to the maximum continuous response frequency at the time of load in which the frequency is increased. 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. Although the torque characteristics of the individual mass-produced motors vary, the variations are ± 10% or less for the PM type stepping motor and ± 5% or less for the HB type stepping motor. Put it to practical use. According to one experiment, 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 engaged in the spur gear reduction unit of the receiving unit mechanism of the mass-produced facsimile.
m), and it was 250 to 300 (g-cm) when the motor pinion gear was attached to the first gear and assembled. Thus, the variation in torque characteristics between individual motors is ± 5 ±±
In fact, 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 (bifile coil) ΦA, ΦA-, of the stepping motor 1 (in this example, a four-phase unipolar motor)
One end of .PHI.B, .PHI.B- is connected to an external power supply VM applied via a connector 5, and the other end is connected to a switching transistor Q1, Q3, Q corresponding to each winding via a connector 6.
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 includes an oscillating circuit for generating a clock serving as a reference for the pulse supply timing to the windings, a positioning circuit for determining the rotation angle (position) of the stepping motor, and the like. It generates a clockwise rotation clock CCW, an excitation mode signal, and the like. The distribution circuit 8 receives the clock CLK and the excitation mode signal, and supplies a pulse in the 2-2 phase excitation to each winding.

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,
In order to measure the coil current, a current detection unit 10 (in this example, inserted into the winding ΦB−) inserted into an arbitrary winding is provided to detect the coil current iB−. This coil current iB− is amplified by the amplifier 11 and
Is supplied to the feature extraction unit 13 through the terminal S1 of the first embodiment.

The feature extraction in the feature extraction unit 13 is, for example, to extract a feature of a torque-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 (drive current) i when it is changed to 0, 100, 200, 300 (g-cm) is shown. From this change (current waveform), it is not appropriate to express the drive circuit of the stepping motor by an equivalent circuit composed of a series circuit of an inductance and a resistor, as is generally known. As shown in FIG. It is clear that, in addition to R, the back electromotive force equivalently generated to pass 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 rising rapidly. In particular, when the PM-type motor is driven with an appropriate drive voltage, the current gradually rises slowly, and the maximum value i
After reaching P, it starts to decrease. 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 can be seen from the figure, the average value of the drive current does not change much even when the load torque is changed, but the change in the current from the time when the current starts flowing to the relevant phase until the current input point of the other phase is started. Is remarkable. For example, by focusing on the load torque and the maximum value iP of the current in FIG. 3 and performing data interpolation processing, 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 = approximately 60 (mA). During this period, 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 extracted in this manner (in this example, torque versus current maximum value information) is stored as a reference value in a reference value memory 14 such as a ROM or a floppy disk.

On the other hand, when the actual machine mechanism section 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 unit 17 calculates the maximum value iP information read from the measured value memory 16 in response to the synchronization signal from the controller 9 and the torque versus current stored in the reference value memory 14 as shown in FIG. The data is collated with the related data to determine and output the actual load torque. For example, feature extraction unit 1
If the maximum value iP obtained in Step 5 is 43 mA, it is determined that the actual load is 150 (g-cm) from the relationship shown 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.

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. In the present invention, the characteristics of the drive current waveform of the motor due to the torque fluctuation are extracted by using the above-mentioned ip-TL characteristics.

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

An embodiment of the present invention which makes the characteristics of the drive current waveform remarkable and improves the measurement sensitivity on the premise of the above will be described. FIG. 5 shows that the PM type stepping motor is driven at a constant frequency (200 PPS) and a constant load torque (300 g).
−cm), the driving voltage is 6 V, 7.5 V,
The change of the current waveform when it is changed to 10 V is shown. In the figure, the broken line indicates the current flowing when the voltage is applied to the L and R series circuits having the same L and R values as the motor.

FIG. 6 shows the ratio η of the motor drive current to the current flowing through the L and R series circuits at an intermediate point between the drive current input point of the self-phase and the drive current input point of the other phase in FIG. It is shown as a function of E. Since the stepping motor is originally an inefficient motor, when the drive voltage is high or the frequency is low, the equivalent circuit behaves like a generally known L and R series circuit. Therefore, the characteristics of the current waveform hardly appear. On the other hand, when the drive voltage is low or the frequency is high, a non-negligible amount of the power supplied to the windings of the motor must 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.

From this, the drive current flowing into the motor is smaller than the current flowing into the L and R series circuits having the same time constant as the motor. From the current input point of the own phase to the input point of the other phase current, the magnitude of the drive current of the motor is
The ratio of the magnitude of the current flowing into the L and R series circuits is
The lower the driving voltage, the greater. After the other-phase current input point, if the drive voltage is high, the drive current rapidly increases. It turns out that.

FIG. 7 shows the same motor at a frequency of 30.
0 and 300g load torque at pps and 100pps
The figure shows a comparison of current waveforms near the input point of self-phase current when driven at −cm. The following is clear from FIG. The change of the current waveform characteristic based on the change of the load torque is
It appears remarkably until a certain time elapses from the point at which the self-phase current is input. 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 section is relatively large even in the no-load state. This is because, in the case of low frequency, the next pulse is applied while the rotor of the motor is completely stationary, so that the torque required for accelerating the inertia moment of the rotor and the load system (in this case, the measurement system) is reduced. It is considered to be added.

In short, it can be seen that it is desirable to drive the motor with the lowest possible voltage in order to increase the change in the drive current waveform of the stepping motor due to the load torque (increase the current waveform characteristics). However, if the drive voltage is reduced too much, the motor loses synchronism and stops. FIG. 8 shows the voltage at which step-out occurs (step-out limit voltage) when the same motor is rotated with no load, as a function of the rotation frequency f. Naturally, the higher the frequency, the higher the step-out eye voltage.

FIG. 9 shows an HB type motor (PJ55-A1 manufactured by Nippon Pulse Motor Co., Ltd.) at 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 shows the same tendency as that of the PM type motor.

FIG. 10 shows that the same motor is driven at the same frequency, the driving voltage is fixed, and the load torque is set to 0, 1, 2, 3K.
The change of the drive current waveform when it is 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 of inputting the self-phase current to the point of inputting the other phase current. From this, it can be seen that the load torque of the motor can be correctly obtained for the HB type motor based on the characteristic amount of the drive current waveform obtained by the above method. Therefore,
In order to measure the load torque efficiently, it is necessary to adjust the drive 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. It is clear from FIG. 2 that the characteristics of the drive current are obtained by the above-described means also in the case of the PM type motor.

FIG. 12 shows a drive current waveform when the motor loses synchronism. In the drawing, current waveforms in a plurality of adjacent sections are shown in an overlapping manner. From this, it can be seen that when the motor loses synchronism, the current waveform is not constant but fluctuates alternately. By utilizing this fact, the step-out state of the motor can be easily determined. Therefore, in order to make the characteristics of the drive current waveform based on the change in the load torque of the stepping motor remarkable, the drive voltage of the motor to be measured is set to such an extent that the motor does not lose synchronization at the required load torque and the required frequency. It is good to lower. Specifically, at a required torque and frequency (and temperature), a limit voltage at which step-out occurs is obtained, and a value obtained by multiplying this voltage by an appropriate coefficient is used as a drive voltage. Further, the characteristic amount of the drive current waveform relates to the elapsed time of the drive current from the self-phase current input point to the other-phase current input point and within a certain time from the self-phase current input point. It can be seen that the integral value should be used. However, in the section where the drive current takes a negative value, the current accumulated in the coil is discharged before the self-phase current is supplied, so that the current characteristic does not appear remarkably. Therefore, this part is excluded from the integration interval. In particular, HB
It can be seen that in a type of motor, it is better to perform integration only in a section where the drive current is positive, as shown below.

Next, an apparatus for measuring the temperature characteristics of the stepping motor will be described. FIG. 13 shows an example showing the temperature characteristics of the stepping motor. The known drive frequency-output torque characteristics were measured using PF42-48105 manufactured by Nippon Pulse Motor Co., Ltd. when the jacket temperature of the motor was 25 ° C. and 48 ° C. From this, it can be seen that when the temperature change of the motor at the time of measurement is large, it is desirable to perform the correction on the temperature characteristic. In order to realize this, the characteristic amount of the drive current waveform of the motor described above 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 value in advance at a known torque and temperature. A specific embodiment 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 using a microcomputer will be described in detail. FIG.
4 shows an embodiment of the above system. Microcomputer (CPU) 113, ROM 11 on bus BUS
2. The RAM 111 is arranged in the same way as in a normal system. Also, an appropriate interface I / F 117
The LCD / software switch driving unit 115 is controlled via the interface I / F 118, and the LCD / software switch driving unit 114 is driven via the interface I / F 118.
A keyboard 116 is connected to form a man-machine interface. Thus, input of measurement conditions, instructions from the apparatus side, and display of measurement results are performed. Furthermore, GP-
Data can be exchanged with an external computer (personal computer) via the IB interface unit 122 or the RS232C interface 123. Also,
An FDD control unit 120 that controls the FDD 121 is provided on the bus.
Are connected, and the external interface 119 is connected.

The drive pulse generator 10 arranged on the bus
From 6, a drive timing to the motor to be measured 100 is generated according to an instruction from the CPU 113. The driving circuit 101 for the unipolar motor or the driving circuit 102 for the bipolar motor are selectively used as needed. The drive circuit supplies a power supply (0 to 48 V, 8 Am
ax), and can be configured by transistors Q1 to Q4 and the like as in the example shown in FIG. The motor to be measured 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 using a resistor or the like. The instantaneous value of the detected current is calculated by an A / D converter at an appropriate sampling interval.
After being converted into digital values, the digital values are sequentially stored in the RAM 111 under the control of the DMA control unit 108. The sampling is executed by starting A / D conversion in accordance with an instruction from a trigger generator arranged on the bus. Further, the trigger generator receives a synchronization pulse from the pulse generator in order to synchronize the timing of the sampling generated by the trigger generator with the timing of the motor drive pulse.

Prior to the measurement, the reference torque setting device control section 109 is controlled under the control of the CPU 113, and the driving circuit 104 drives the reference torque setting device 103.
In this embodiment, it is necessary to appropriately set the drive voltage of the motor to be measured in order to make the characteristics of the current waveform remarkable with respect to the fluctuation of the load torque. Therefore, an appropriately set voltage is supplied to the drive circuit from the voltage variable power supply 105 disposed on the bus.

Next, in the embodiment shown in FIG. 14, after the load torque-current waveform characteristic of the motor to be measured is calibrated, the motor to be measured is connected to the actual load mechanism to measure the load torque. It will be described using FIG.

FIGS. 15 to 19 are flowcharts showing a processing procedure in which a known load torque is applied to the motor to be measured, and a relation (reference value) between the load torque and the characteristic amount of the current waveform is obtained. First, as shown in FIG. 15, measurement conditions are given to the apparatus. The highest frequency fH, the lowest frequency fL,
The maximum reached 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 at the time of measurement are specified. In response to this, the apparatus of this embodiment first sets the measurement range by setting 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 (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
This is executed according to the procedure shown in FIG. First, an optimal drive voltage is determined (step S11). In this determination operation, 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 stepping out within the required measurement range (step S31). ). Next, the target value f0 of the measurement frequency is set to the lowest measured 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, a timing wait is performed, the drive current waveform is checked (steps S37, S38), and it is confirmed that the motor has not stepped out (step S39). If step-out occurs even when the drive voltage is set to EH,
Stop the motor as an error. In step S40, when it is confirmed that the predetermined frequency f0 has been reached,
In order to obtain the step-out limit of the drive voltage, the drive voltage E is gradually reduced while monitoring the drive current waveform (step S).
41), check the current waveform (step S42),
Step-out limit is measured by determining step-out (step S4)
3). Here, if a step-out occurs, the drive voltage at that time becomes
This is the step-out limit voltage.

Next, the temperature T of the motor is determined by
The measurement is performed by the resistance method (step S44). Then, the limit voltage is multiplied by (1 + α) using an appropriate coefficient α to obtain an optimum drive voltage. Then, it is stored in a file or a memory together with the parameters TQH, f, and T when the measurement was performed (step S45). Subsequently, after increasing the target frequency by Δf0 (step S46), the above measurement is repeated. In step S47, the measurement of the necessary 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 is terminated. When the optimum drive voltage is determined, the process returns to the process in 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). Subsequently, a reference torque TQ is given (step S13). To apply a known load torque, it is possible to use, for example, a permatorque manufactured by Koshin-Lasyn Corporation. In this method, a known torque is applied to a rotating shaft by using a hysteresis magnetic material and turning a dial to set a scale to a predetermined value. The setting of the dial can be performed manually, but the dial may be automatically rotated from the apparatus side using a stepping motor or the like. After setting the torque to the desired value, the lowest value within the range where the frequency f is to be measured, fL
(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).
To S17). The obtained feature quantity Q is used as the torque TQ, Ea,
f and T are stored as parameters (step S1).
8). Subsequently, after increasing the frequency by Δf0 (step S19), a time wait is performed by Δt (step S2).
0) The above measurement is repeated for the same torque until it is confirmed in step S21 that the frequency has reached the desired maximum value fH. Thus, 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, if necessary, the motor is stopped once (step S22), and the torque is changed. That is, after the torque TQ is decreased by ΔTQ (step S23), the above measurement is repeated. If it is determined in step S24 that the measurement for the entire range of torque has been completed, the storage of the reference value is completed.

Referring back to FIG. 15, if necessary, the temperature characteristics are measured and stored. That is, after increasing the target value T0 of the measured temperature by ΔT0 (step S3), the coil is energized while the motor is kept stationary (step S4), and the temperature of the motor is increased to a required value. While measuring the temperature TM (step S5), the energization is continued, and step S6 is performed.
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 the present embodiment, FIG.
It is easy to understand by referring to the embodiment related to the measurement of the current waveform of the motor shown in FIG. This example is an HB type stepping motor PJ55-A manufactured by Nippon Pulse Motor Co., Ltd.
1 was measured at a frequency of 700 pps with load torques of 0, 1, 2, and 3 Kg-cm, respectively. In FIG. 10, the 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 this embodiment, the characteristic amount is determined by changing the current waveform from t0 to t1.
The drive current is integrated with respect to time only when the drive current is positive. However, as described above, when the driving 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 integrated value (= current waveform feature) on the horizontal axis and the load torque TQ on the vertical axis. From this, it can be seen that the above-described logic can determine the current waveform characteristic amount versus load torque characteristic of the HB type stepping motor.
As described above, the current waveform characteristic can be obtained in the same manner for the PM type motor.

FIG. 18 shows a flowchart for extracting the above-mentioned current waveform characteristics. The integration is performed for a section starting from t0 and reaching an 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). Further, if tc exceeds the other-phase current input point t1, this is limited to t1 (steps S52 and S53). Next, in performing the integration of the drive current,
The time t at which the integration is performed is initialized to t0 (Step S
54). In addition, the integration value S is also initialized (step S5).
5) Measure drive current i (t) (step S5)
6). When it is determined that the time has reached the time t at which the 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 integral value S (step S5).
8). If i (t) is negative, no integration is performed. When the processing at the time t is completed, the next time t
Is increased by a predetermined increment Δt (step S59), and the process at the next time is performed. In step S60, when it is determined 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 used as the current waveform feature quantity 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 arrange the measured characteristic amounts in the subsequent measurement of the load torque.

FIG. 19 is a flowchart showing a processing procedure for organizing feature quantities. The optimum drive voltage Ea is measured as a function of the frequency and the temperature (step S71).
It is stored (step S72). In subsequent measurements,
The required values are easily obtained. 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, or the like, and the coefficient is obtained. Next, the coefficients obtained in this manner are similarly interpolated with respect to the temperature T, and the coefficients are obtained, whereby Ea can be arranged with respect to T and f. The results are organized as coefficients representing these functions. Next, the load torque is obtained as a function of the current waveform feature quantity,
It is arranged and stored (steps S73 and S74). At this time, it is convenient to make it dependent on the frequency and the temperature. With the above, the preparation for performing the load torque measurement is completed. Thereafter, the measurement can be performed with the motor to be measured mounted on the actual device to be tested.

The above-described effects of the present invention are remarkable in devices mass-produced using the same type of motor. First, by calibrating the relationship between the load torque and the current waveform characteristics for a typical motor, the load torque of the device can be easily measured within the range of the manufacturing error of the motor. Therefore, it is possible to quantitatively discuss the problems in the development, quality evaluation, mass-production prototype of the relevant equipment, inspection on the production line, and quantitative discussion on the load torque between the development and production departments. Extremely large.

FIG. 20 shows a procedure for measuring the load torque. First, the maximum fH, the minimum fL, and the variation width Δf of the measurement frequency are specified (step S101). After the frequency is initialized to the lowest value fL (step S102), the temperature is measured (step S103), and the optimum driving voltage (driving voltage) is measured.
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 S107).
108). Subsequently, the frequency is increased by Δf (step S109), and the load torque is measured again according to the above procedure. The above process is repeated until it is confirmed in step S110 that f becomes larger than fH, thereby obtaining the frequency characteristics of the load torque in a state where the actual motor is mounted on the device to be measured in a predetermined range. Can be done. When the measurement is completed, stop the motor (step S
111), the measurement result is displayed as a graph, a table, or the like as appropriate (step S112).

Next, an application device of the load torque measuring device for a stepping motor according to the present invention will be described. FIG.
Indicates a state in which the mechanical part of the product to which the motor is mounted has play and the state in which the load torque fluctuates with the rotation (as time elapses) is measured. Generally, power output from the output shaft of a motor is transmitted to each part of the mechanism via a number of pinions / gears. For this reason, the fluctuation of the load torque does not always coincide with the rotation to the motor simply and periodically. Thus, by dividing the frequency of the pulse applied to the motor as a marker and adjusting the frequency division ratio appropriately, it is possible to make the cycle of the variation of the load torque coincide with the repetition cycle of the marker. This makes it possible to estimate a defective portion in consideration of the gear configuration of the mechanism section and the like, and thus has a great industrial effect.

FIG. 22 shows an embodiment for generating the marker. Frequency divider 30 for inputting a motor driving pulse
By appropriately giving the frequency dividing ratio N, the marker shown in FIG. 21 is obtained.

FIG. 23 shows another embodiment for obtaining the marker. In this embodiment, the PLL method is adopted.
A phase comparator 32 compares a motor drive pulse (frequency f) obtained by dividing the frequency of the motor by N with a frequency divider 31 (f / N) and an amount proportional to the fluctuating load torque. If the phase of the fluctuation of the load torque is advanced, the frequency division ratio of the frequency divider 31 is reduced. Conversely, when the phase of the amount proportional to the load torque is delayed, the frequency 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 load torque measuring device for a stepping motor according to the present invention, it is possible to accurately measure the torque output from the motor while the stepping motor is mounted. Therefore, 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. .

[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 temporal change 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 a relationship between a maximum value iP of a drive current flowing through a winding obtained based on FIG. 2 and a load torque.

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

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

6 is a graph showing the ratio η of the motor drive current to the current flowing through the L and R series circuits at an intermediate point between the drive current input point and the other phase current supply point in the drive current shown in FIG. FIG.

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

FIG. 8 is a diagram showing, as a function of a rotation frequency f, a voltage at which step-out occurs (step-out limit voltage) when the same motor is rotated with no load.

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

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

FIG. 11 shows a value Q obtained by integrating a portion where the drive current flowing into the motor is positive from the point of inputting the self-phase current to the point of inputting the other phase current.
FIG. 6 is a diagram showing a relationship between the load torque and the load torque TQ.

FIG. 12 is a diagram showing a drive current waveform when a motor loses synchronism.

FIG. 13 is a diagram illustrating an example of a temperature characteristic 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 a motor to be measured and obtaining a relationship (reference value) between the load torque and a characteristic amount of a current waveform.

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

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 value of a current waveform of a reference value in FIG.

FIG. 19 is a flowchart showing a processing procedure for arranging feature amounts in FIG. 15;

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

FIG. 21 is a view showing a state in which a mechanical portion of a product equipped with a motor according to an embodiment of the present invention has a play and a load torque fluctuates with rotation.

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

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Stepping motor 2 Actual 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
Switches 13 and 15 Feature extraction unit 14
Reference value memory 16 Measurement value memory 17
Collation judgment unit 18 Display 19
Printer

Continuation of front page (56) References JP-A-6-43049 (JP, A) JP-A-55-71196 (JP, A) JP-A-2-246793 (JP, A) JP-A-2-155496 (JP) JP-A-50-31880 (JP, A) JP-A-54-123079 (JP, A) JP-A-55-71196 (JP, A) JP-A-2-60496 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01L 5/00 H02P 8/38

Claims (9)

(57) [Claims] A memory means for storing relationship data between a torque applied to a stepping motor and predetermined characteristic information of a drive current flowing through the stepping motor when the torque is applied, Detection means for detecting the drive current when a load is applied; feature extraction means for extracting the feature information of the drive current obtained by the detection means; feature information extracted by the feature extraction means; Collation judging means for collating the relational data stored in the memory means and outputting the actual load; and the stepping motor does not lose synchronization during calibration.
Driving means for driving the motor at a voltage set to a value obtained by multiplying a critical voltage by a predetermined count , and driving means for driving the motor at a voltage determined at the time of calibration when measuring an actual load, comprising: Torque measuring device for stepping motors. 2. The torque applied to a stepping motor, and the time between when the current starts flowing into an arbitrary phase of the stepping motor when the torque is applied and when the current starts flowing into another phase. A memory means for storing data relating to characteristic information defined by an integral value of the drive current flowing into the phase, and current flowing to an arbitrary phase of the stepping motor when an actual load is applied to the stepping motor. From when the inflow starts, until the current starts to flow into another phase, detecting means for detecting an integrated value of the driving current flowing into the phase, and a driving current of the driving current obtained by the detecting means. A feature extraction unit that extracts the feature information; a matching determination unit that compares the feature information extracted by the feature extraction unit with the relational data stored in the memory unit and outputs 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 flowing 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 a current flowing into the phase has a predetermined polarity. 5. A method according to claim 1, wherein a plurality of different torques and rotation speeds are applied to the stepping motor, and the first driving current flowing through the stepping motor is extracted by predetermined means.
Memory means for storing data relating to the output first characteristic information; and drive power when an actual load is applied to the stepping motor.
Detecting means for detecting the flow , characteristic extracting means for extracting characteristic information of the drive current obtained by the detecting means, and applying a known rotation speed and an actual load to the stepping motor.
Of the second drive current at the time of
Using the extracted second characteristic information, collating with the relational data stored in the memory means, and collating and judging means for outputting the actual load. Load torque measuring device. 6. Whether the first drive current flowing to the stepping motor when a different torque and rotational speed that is different to the stepping motor at a plurality of temperatures are given
A memory means for storing data relating to the first feature information extracted by predetermined means, and a drive power when a real load is applied to the stepping motor.
Detecting means for detecting the flow , characteristic extracting means for extracting characteristic information of the driving current obtained by the detecting means, and applying a known temperature, a rotation speed and an actual load to the stepping motor.
Of the second drive current when the
Using the extracted second characteristic information to collate the relational data stored in the memory means, and outputting the actual load. Load torque measuring device for motor. 7. A memory means for storing relationship data between a torque applied to a stepping motor and predetermined characteristic information of a drive current flowing through the stepping motor when the torque is applied. Detection means for detecting the drive current when a load is applied; feature extraction means for extracting the feature information of the drive current obtained by the detection means; feature information extracted by the feature extraction means; A comparison / judgment unit that collates the relational data stored in the memory unit and outputs the actual load; and a unit that measures a temporal change of the characteristic information obtained by the characteristic extraction unit. Characteristic load torque measuring device for stepping motors. 8. A memory means for storing relationship data between a torque applied to a stepping motor and predetermined characteristic information of a drive current flowing through the stepping motor when the torque is applied. Detection means for detecting the drive current when a load is applied; feature extraction means for extracting the feature information of the drive current obtained by the detection means; feature information extracted by the feature extraction means; A comparison / judgment unit that collates the relational data stored in the memory unit and outputs the actual load; a time at which a driving pulse is applied to the stepping motor; and a load obtained by the comparison / judgment unit. Means for measuring the transmission delay characteristic of the load by comparing the time with the time at which the load torque occurs. Measuring device. 9. A memory means for storing relationship data between a torque applied to a stepping motor and predetermined characteristic information of a drive current flowing through the stepping motor when the torque is applied. Detection means for detecting the drive current when a load is applied; feature extraction means for extracting the feature information of the drive current obtained by the detection means; feature information extracted by the feature extraction means; Collating and judging means for collating the relational data stored in the memory means and outputting the actual load; the load torque of the stepping motor and the driving pulse applied to the stepping motor divided by an arbitrary multiple Means for comparing changes over time of the two, and a load torque measuring device for a stepping motor.