JP2918183B2 - Stepping motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor control device having a stepping motor operating angle correcting means used for, for example, driving a carriage of a serial printer.

[0003]

2. Description of the Related Art Generally, a stepping motor is widely used for driving a carriage of a serial printer. The drive control of this stepping motor includes, for example, a micro step method described in Japanese Patent Application Laid-Open No. 1-152996. This micro-step method drives the excitation current supplied to each phase of the stepping motor with a predetermined phase difference in a stepwise manner with a predetermined number of steps and approximates a sine curve. As compared with the case where the motor is driven by the exciting current, there is an advantage that the resolution of the basic step angle of the motor is improved, torque ripple is suppressed, and vibration and noise can be reduced.

FIG. 8 shows a micro-step operation when one phase is divided into two, and a four-phase stepping motor is operated by 360 degrees in electrical angle for four steps. Here, the four phases of the stepping motor (not shown), that is, the A phase, the B phase, the C phase, and the D phase are 90 electrical degrees relative to each other.
A phase, B phase, C
When the phase and the D phase are excited by the current having the phase and the waveform as shown in the drawing, a torque as shown by a solid arrow is generated.

For example, when the A-phase excitation current has the maximum step value, a torque is generated in the direction of 0 electrical angle, and when the A-phase excitation current and the B-phase excitation current are both intermediate step values, both 0 degree and 90 degrees are generated. , A torque is generated in the direction of 45 degrees by these combined vectors indicated by broken arrows. Hereinafter, each time the exciting current is sequentially switched, a drive torque of 45 degrees in electrical angle is generated.

Since the microstep drive is controlled by an open loop, the phases A, B, C, and D must be separated by exactly 90 degrees in electrical angle. Largely depends on the accuracy of the motor itself.

For this reason, a motor that can be used for microstep driving is generally an expensive motor with good angular accuracy, and is inexpensive but has a large variation in angular accuracy.
When a (permanent magnet) type motor is used,
Vibration and noise occur, and the expected microstep drive effect cannot be obtained. That is, in order to achieve the original effect of the micro-step driving, an expensive motor with good angular accuracy must be used, which leads to an increase in cost.

Further, such a motor having a good angle accuracy has a larger volume than that of the PM type, and cannot be applied to a small device. For this reason, the PM type has to be used for small-sized devices, but only the motor having good angular accuracy must be selected from many PM type motors, which lowers the yield and eventually increases the cost.

Although the above description is directed to a four-phase PM type motor, it is also applicable to a VR type or hybrid type motor.
If the angle accuracy is poor for the three-phase, three-phase,... Motors as well, the originally expected effect of microstep driving cannot be obtained.

[0010]

As described above, in order to obtain the original effects of the micro-step driving, there is a problem that the angular accuracy of each phase must be good and the usable motors are limited. Was.

An object of the present invention is to provide a stepping motor control device which performs control so that a desired microstep driving effect can be obtained even if the angular accuracy of each phase is somewhat low.

[Structure of the Invention]

[0013]

SUMMARY OF THE INVENTION The present invention relates to a stepping motor control device for sequentially switching each phase of a stepping motor having a plurality of exciting windings, and supplying and driving an exciting current while maintaining a predetermined phase difference. , a micro-step control means for varying the excitation current of each of the phases to a predetermined number of steps of the staircase shape, a plurality of each of said stepping motor
For each of a plurality of ranks set in advance in accordance with the electrical angle error amount between the phases, the stepping storage means, from the storage means, to be controlled with an electrical angle corresponding to the electrical angle error amount as a correction value A correction means for reading a correction value corresponding to the rank of the motor, correcting the switching timing of each phase by the correction value, and adjusting the phase of each phase excitation current.

[0014]

According to the present invention, a plurality of stepping motors are provided.
Rank based on the electrical angle error amount between each phase determined in advance, reads a correction value which is stored in advance in the storage means corresponding to the rank of the stepping motor to be controlled, switching of the correction value each phase The timing is corrected to adjust the phase of each phase excitation current. For this reason, the desired micro-step driving effect can be obtained even with a motor in which the angular accuracy of each phase is somewhat low.

[0015]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 11 denotes a stepping motor, which is used for driving a carriage of a serial printer (not shown). As is well known, the stepping motor 11 has excitation windings 11a and 11b, and a connection point between the excitation windings 11a and 11b is connected to an excitation power supply V.
h are supplied. Both ends of the exciting windings 11a and 11b are connected to corresponding NPN transistors of the transistor array 12.

That is, one end of one excitation winding 11a is
Through the collector and emitter of the phase transistor 12A,
The other end is connected in common after passing between the collector and the emitter of the C-phase transistor 12C, and further connected to the ground via a current detecting resistor 13AC. One end of the other excitation winding 11b passes through the collector and emitter of the B-phase transistor 12B, the other end passes through the collector and emitter of the D-phase transistor 12D, and is commonly connected.
Connected to ground via

The base of each transistor 12A, 12B, 12C, 12D of the transistor array 12 has an enable gate 14
The output terminals of the corresponding AND gates 14A, 14B, 14C, 14D are connected, and these AND gates 14A, 14B, 14C, 14D
An excitation phase switching signal is input via the.

Here, the AND gates 14A, 14B, 14C, 14
To each one input terminal of D, corresponding phase data for excitation phase switching is input from the microcomputer 15 of one chip. In addition, each other input terminal has a comparator 16A
Output signal from C, 16BD is input.

For the comparator 16AC, the terminal voltage of the current detection resistor 13AC is input to the inverting input terminal,
A reference voltage corresponding to a reference value of an exciting current described later is input to the non-inverting terminal. Therefore, the comparator 16AC
Indicates that when the A-phase or C-phase current value rises to the reference value of the exciting current and the input voltage to the inverting input terminal becomes higher than the reference voltage applied to the non-inverting terminal, the output is inverted to L level. Then, the other input terminal of the AND gate 14A or 14C is set to L level. For this reason, if these AND gates 14A or 14C are on, they are turned off and the corresponding transistors 12A or 12C are turned on.
Is turned off, and the phase current is cut off.

The function of the comparator 16BD is the same as that of the comparator 16AC. When the B-phase or D-phase current value rises to the reference value of the exciting current, the output is inverted to L level, and the other one of the corresponding AND gates 14B or 14D is turned off. Is turned to an L level, and if these AND gates 14B or 14D are on, they are turned off, and the corresponding transistors 12B or 12D are turned off to shut off the phase current.

That is, when the value of the exciting current flowing through each phase reaches a reference voltage from the D / A converter 23, which will be described later, that is, the reference value of the exciting current set in the microcomputer 15, this is cut off. I do.

The microcomputer 15 has a storage means.
An internal ROM 21 serving as 21 is provided in which a timing table for driving the stepping motor 11 and a current value table are set.

The timing table contains the excitation phase data A, B, C, and D shown in FIGS. 3 to 7 for driving the stepping motor 11, and the switching timing of the excitation phases (ie, the switching timing of the excitation current). Is set. In the current value table, an exciting current value for obtaining an appropriate driving torque is set according to the microstep phase.

Here, in the present embodiment, one phase is divided into 8
Exciting current value for each step is 8-bit digital signal so that micro-step driving is performed in 6 steps.
It is set in the current value table. The microcomputer 15 outputs, to the D / A converter 23, an exciting current value that matches the phase of each microstep, that is, an 8-bit digital signal set in the current value table, based on the clock signal. D / A converter 23
Converts the digital signal into an analog signal (voltage value) and uses the comparator 16 as a reference value of the exciting current.
Output to the non-inverting terminal of AC, 16BD.

When driving the stepping motor 11, the microcomputer 15 generates excitation phase data A, B, C,
D is sequentially output with a predetermined phase difference, and the reference value of the exciting current for each microstep is output to the D / A converter 23. Therefore, the excitation phase and the excitation current are sequentially switched by the enable gate 14 and the transistor array 12, and the comparator is operated according to the reference value signal corresponding to each micro step from the D / A converter 23.
16, the enable gate 14, and the transistor array 12 make the exciting current of each phase a step-like waveform approximating a sine curve, and drive the stepping motor 11 by microstepping. That is, each circuit such as the D / A converter 23, the comparator 16, the enable gate 14, the transistor array 12, and the like functions as a micro-step control unit.

In the EE-PROM 24, a rank corresponding to the angular accuracy of the stepping motor 11, which will be described later, is set. The angle accuracy will be described below with reference to FIG.

FIG. 2 shows a four-phase PM type stepping motor 11.
The structure of the coils 11a and 11b of FIG.
1a and the coil 11b for the BD phase, as shown in FIG.
It is configured in stages. In this case, between phase A, phase C and B
Since the phase and the D phase are common coils 11a and 11b, respectively, the angle accuracy is good and they are arranged at an electrical angle of almost 180 °. On the other hand, two coils for the AC phase and the BD phase
It is difficult to keep these built-in accuracy high between 11a and 11b, and the BD-phase axis is not orthogonal to the AC-phase axis with high accuracy in electrical angle. That is, A in FIG.
This means that the positional relationship between the C-phase coil 11a and the BD-phase coil 11b is shifted left and right, which means that the angular accuracy is poor.

Since the angle accuracy, that is, the inclination of the BD phase axis with respect to the AC phase axis differs for each motor, this inclination is measured in advance using a tester or the like for each stepping motor 11 and the inclination is measured for each amount of inclination. Rank it. For example, as shown in Table 1, five ranks from -2 to +2 are set in accordance with the shift amount θ ° (inclination amount), and the rank is determined according to the shift amount.

[0030]

[Table 1]

In this embodiment, the stepping motor 11 is
For example, when the stepping motor 11 is incorporated in a carriage driving device of a serial printer or the like, the rank data of the stepping motor 11 to be incorporated (also controlled) is shown in a command form by an interface connector (not shown) connected to the microcomputer 15. Not entered from host computer etc. Microcomputer 15
Interprets the command and converts the rank data to EE-PRO
Write to M24. This rank data is retained even after the power is turned off.

When driving the stepping motor 11, the microcomputer 15 advances the phase of the BD phase sine curve with respect to the AC phase sine curve according to the rank data read from the EE-PROM 24, as shown in FIG. Or delay it. For this purpose, a correction amount (electrical angle) corresponding to the rank is set in the storage means 21 in advance. In this example, since the rank is divided into five levels, the electrical angle (1
(1.25 °) as a reference, a multiple of the electrical angle corresponding to this rank is used as a correction value. That is, rank "normal"
In FIG. 3, the correction value is “0” as shown in FIG. 3, and in the case of rank “−1”, the correction value is “+1 microstep (+1)” as shown in FIG.
1.25 °), the correction value is “−1 microstep (−11.25 °) for rank“ +1 ”as shown in FIG. 5, and the correction value is“ +2 microstep ”as shown in FIG. 6 for rank“ −2 ”. (+ 22.5 °), and at the rank “+2”, the correction value is “−2 microsteps (−22.5 °)” as shown in FIG.

Further, the microcomputer 15 comprises a correcting means for adjusting the phase of each phase exciting current in accordance with the correction value.
With 22. The correction means 22 reads a correction value corresponding to the rank of the stepping motor 11 to be controlled from the storage means 21 and corrects the switching timing of the A, B, C, and D phase data by the correction value. The phase of each phase excitation current is adjusted.

Here, in general, when microstep driving is performed, digital data set in the microcomputer 15 as described above is used to drive the stepping motor 11 by chopper. If the angular errors of the stepping motors 11 are ranked as described above, the error characteristics of each motor become digital data.

The present invention has been made in view of such a point, and the driving data of the stepping motor 11, that is, A, B, C, D corresponding to the rank data of the error angle.
By adjusting the timing of each phase data, the error unique to each motor is absorbed.

In the above configuration, the stepping motor 11
Microcomputer 15 sequentially outputs the A, B, C, and D phase data with a predetermined phase difference, and outputs the current value data set for each microstep via the D / A converter 23. Then, the stepping motor 11 is microstep-driven by setting each phase excitation current to a step-like waveform approximating a sine curve.

Here, the stepping motor 11 to be controlled is
If the coil shift amount is small and the rank is “normal” shown in Table 1, the correction amount is “0”, and as shown in FIG. 3, the switching timing of the A, B, C, and D phase data is As standard, their phase difference does not change. On the other hand, when the coil displacement is within the range of -16.875 ≦ -5.625 , the rank is “−1” as shown in Table 1, and as shown in FIG. The switching timing of the A, B, C, and D phase data is corrected so that the phase of the exciting current advances by 1 microstep (11.25 °). Conversely, when the rank is “+1”, as shown in FIG. 5, A, B, and B are set so that the phase of the BD phase excitation current is delayed by one microstep (11.25 °) with respect to the AC phase excitation current. The switching timing of the C and D phase data is corrected. Hereinafter, similarly, when the rank is “−2”, as shown in FIG. 6, the phase of the BD phase excitation current is advanced by 2 microsteps (22.5 °) with respect to the AC phase excitation current, and When the rank is “+2”, as shown in FIG. 7, the phase of the BD phase excitation current is 2 with respect to the AC phase excitation current.
The switching timing of each of the A, B, C, and D phase data is corrected so as to be delayed by a microstep (22.5 °).

As described above, since the phase of the microstep excitation current is changed in accordance with the rank (shift amount) of the stepping motor 11, the microstep effect can be obtained even if a motor having poor angular accuracy is used. For this reason, it is not necessary to select only motors having good angular accuracy as in the related art, and the yield does not decrease.
That is, micro-step driving can be performed without increasing the cost.

An EE-PROM 24 is used for storing ranks.
Is used, when the stepping motor 11 is replaced, the rank can be easily reset to the value of the replaced stepping motor, and the maintainability is good.

In the above embodiment, the rank of the shift amount is divided into five stages. However, when the stepping motor 11 having a large shift amount is used, the number of ranks may be increased and the correction amount may be increased. Further, as the correction amount, the correction is performed based on the electrical angle of 11.25 ° as a basic multiple. However, if a finer correction is required, the number of microstep in-phase divisions is increased and the number of steps is increased. do it.

[0041]

According to the present invention, for each stepping motor, a rank based on the electrical angle error between a plurality of phases is obtained in advance, and a storage means is provided in advance corresponding to the rank of the stepping motor to be controlled. It reads out the correction value which is stored in, so to adjust the correction value the phase of the correction to the phase excitation current switching timing of each phase, the micro step drive, albeit at a low cost compact, angular accuracy is since it became possible to apply the stepping motor inferior, it is possible to maintain low manufacturing cost, since not require much space, the stepping motor is Ru can miniaturize the entire apparatus to be used.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a stepping motor control device according to the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration example of an excitation coil of a stepping motor.

FIG. 3 is a waveform diagram showing a correction state in which a phase is changed in accordance with a normal rank of angular accuracy.

FIG. 4 is a waveform diagram showing a correction state in which a phase is changed corresponding to −1 rank of angle accuracy.

FIG. 5 is a waveform diagram showing a correction state in which a phase is changed corresponding to +1 rank of angle accuracy.

FIG. 6 is a waveform diagram showing a correction state in which a phase is changed corresponding to -2 ranks of angle accuracy.

FIG. 7 is a waveform diagram showing a correction state in which a phase is changed corresponding to +2 ranks of angle accuracy.

FIG. 8 shows the switching timing of the phase current by the conventional device,
It is a figure showing relation with generated torque.

[Explanation of symbols]

11 Stepping motors 11a, 11b Excitation windings 12, 14, 16, 23 Transistor array, enable gate, comparator and D / A converter which are the main components of micro-step control means 21 Storage means 22 Correction means

Claims (1)

(57) [Claims] 1. A stepping motor control device for sequentially switching each phase of a stepping motor having a plurality of excitation windings and supplying and driving an excitation current while maintaining a predetermined phase difference, wherein the excitation current for each phase is controlled by a predetermined value. Micro-step control means for changing the number of steps in a stepwise manner; and for each of a plurality of ranks set in advance in accordance with the electrical angle error between the plurality of phases of the stepping motor, the electric power corresponding to the electrical angle error A storage unit having an angle as a correction value; reading out a correction value corresponding to the rank of the stepping motor to be controlled from the storage unit; correcting the switching timing of each phase by the correction value; A stepping motor control device comprising: a correction unit that adjusts a phase of a current.