JPH1032997A - Method for driving stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the rotational position of a stepping motor with infinitesimal resolution by controlling the position of the rotating shaft of the motor within the angle range which is four times as large as the basic step angle of the motor by respectively giving two electric signals having a 90degree phase- deviated trigonometric functional relation between them to two coils. SOLUTION: When one cycle of a stepping motor having two coils is set at the quadruple of the basic step angle of the motor, electric signals which shift the signals to be given to the A- and B-phases by a 1/4 period, namely, having trigonometric functional relations in both the A- and Bphases by controlling the position of the shaft of the motor are given. Specifically, a current proportional to cosθ is given to the A-phase and another current proportional to sinθ is given the the B-phase. Accordingly, the arbitrary rotational position of the motor can be controlled within the angle range which is quadruple as large as the basic step angle of the motor. Therefore, the rotation of the motor can be controlled precisely while making the best use of the characteristics 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 driving method for a stepping motor, and more particularly to a driving method capable of controlling a rotation position more finely than a basic step angle.

[0002]

2. Description of the Related Art Conventionally, two-phase (or four-phase), three-phase or five-phase stepping motors have been widely used as industrial motors. A stepping motor is generally characterized by a large rotational torque compared to inertia, and a precise movement according to an input pulse signal without feedback control.

FIG. 1 shows a general driving method of a two-phase stepping motor. A phase, B
Two sets of windings called phases are wound around the stator, and when electric signals as shown in FIG. 1 are applied to the A phase and the B phase, the windings rotate by P degrees. P is referred to as a basic step angle of the stepping motor, and is designed to have various angles of 1.8 degrees, 3.75 degrees, or 7.5 degrees depending on purposes.

In FIG. 1, when a current is applied to the phase A and the phase B is kept unexcited, the motor rotates P degrees from the previous position and stops. Next, if the B phase is also excited while the A phase is excited, the motor further rotates by P degrees and stops. As described above, when the A-phase and the B-phase are excited in the procedure shown in FIG. 1, the stepping motor continues to rotate with P degrees as the basic step angle. As is clear from FIG. 1, the same operation is repeated when the position advances by 4P degrees.

[0005]

Here, attention is paid to a region within a rotation angle of 4P. When the relationship between the electric signals given to the A-phase and the B-phase has two stages of ON and OFF as described above, the resolution is only P degrees. However, when a stepping motor is applied to a rotary type pressure control valve in which the output pressure changes greatly due to minute rotation,
At a resolution of about the basic step angle P, fine pressure control may not be possible.

An object of the present invention is to provide a method of driving a stepping motor capable of controlling a rotational position with infinitesimal resolution by inputting a special signal to a coil.

[0007]

According to a first aspect of the present invention, there is provided a stepping motor having two coils.
The position of the rotary shaft is controlled within an angle range four times the basic step angle P by giving electric signals having a trigonometric relationship shifted by 0 degrees.

According to a second aspect of the present invention, in a stepping motor having three coils, an electric signal having a trigonometric function relationship with a phase shift of 120 degrees is given to each of the three coils to rotate the motor. The position of the shaft is controlled within an angle range that is six times the basic step angle P.

Taking a stepping motor having two coils as an example, if 4P is one cycle, the signals to be applied to the A and B phases are shifted by 1/4 cycle, in other words, the A and B phases are shifted. , An arbitrary rotation position within a rotation angle of 4P can be controlled with an infinitesimal resolution. More specifically, if a current proportional to cos θ is applied to the A phase and sin θ is applied to the B phase, an arbitrary rotation position within the rotation angle 4P can be controlled as described above. here,
θ indicates an arbitrary value of 0 to 2π.

In the case of a stepping motor having three coils, since 6P is one cycle, the signals to be applied to the three coils are shifted by ３ cycle, that is, sin θ, sin (θ− 240 °), sin
If an electric signal having a trigonometric function relationship such as (θ−120 °) can be given, an arbitrary rotation position within a rotation angle of 6P can be controlled with infinite resolution.

[0011] In addition to those having two or three coils, there are also stepping motors having five or more coils. These stepping motors have a large structure and a circuit. The complexity makes the control difficult. In contrast, 2
The phase and three-phase stepping motors have a simple structure and a simple circuit, so that the control is simple.

[0012]

2 and 3 show one embodiment of a fluid pressure control device to which the present invention is applied. 2 phase (or 4
Phase) A three-phase or five-phase stepping motor 12 is attached to a valve body 13 with bolts 14. If the electric signal can be converted into a mechanical rotational force, besides the stepping motor 12, for example, a rotary torque motor, D
Although a C motor or a DC servo motor can be used, in this embodiment, a stepping motor having a relatively small rotor inertia and a relatively large generated torque (that is, a high response can be expected) is mainly used for the input stage. . Therefore, a motor other than the stepping motor is not excluded.

The rotating shaft 1 of the stepping motor 12
5 is firmly connected to a shaft 17 fixed to a rotary valve 16 via a flexible coupling 18. In this embodiment, a method in which the flexible coupling 18 is fixed to the shafts 15 and 17 with the set screw 19 is illustrated.
5 and 17 are integrated into a flexible coupling 18
May be omitted. The shafts 17 and 20 of the rotary valve 16 are supported by bearings 21 and 22, and the rotary valve 16 and these bearings 21 and 22 are rotatably inserted into the inner periphery of the sleeve 23. The sleeve 23 is fixed to the valve main body 13, and these components constitute a valve body of the present invention.

The sleeve 23 has three through holes provided radially, that is, variable orifice holes 24 and 25 and a drain hole 27 for returning pressurized fluid to the reservoir tank 26.
Are provided. Channel 3 communicating with holes 24 and 25
Output ports 28 and 29 are provided in the middle of 6 and 37 so that the pressures P ₁ and P ₂ of the output ports 28 and 29 can be taken out. Fixed orifices 32, 33 are provided between the output ports 28, 29 and the supply ports 30, 31 for pressurized fluid.

The rotary valve 16 has flat notches 34, 35 in the cylindrical portion facing the holes 24, 25. Note that the one cutout surface 35 may not be provided, but is provided to improve the rotational balance of the rotary valve 16. FIG. 3 shows a neutral state, that is, a state in which the holes 24, 25 are closed by the cylindrical portion of the rotary valve 16, and at this time, the output ports 28, 2
The pressure at 9 is P ₁ = P ₂ = Ps. Ps is the original pressure.

FIG. 4 shows a state in which the rotary valve 16 has been rotated clockwise from the neutral position. The hole 25 closed in the neutral position is opened by a cutout surface 34 provided in the rotary valve 16, and the pressurized fluid flowing through the supply port 31 and the fixed orifice 33 passes through this opening and passes through the hole 2.
7. Return to the reservoir tank 26 via the flow path 38. Accordingly, the pressure P ₂ of output port 29 becomes lower than the original pressure Ps. On the other hand, since the hole 24 remains closed by the cylindrical portion of the rotary valve 16, the pressure at the output port 28 becomes P ₁ = Ps
It is. That is, the pressure at the output ports 28 and 29 is P
_1> a relation of P _2. If the direction of rotation of the rotary valve 16 is counterclockwise, then P ₁ <P ₂ . In this manner, in the present invention, the pressures P ₁ and P ₂ of the output ports 28 and 29 can be arbitrarily controlled according to the rotation direction and the rotation angle of the rotary valve 16.

In FIG. 2, the plug 39 has bearings 21 and
The rotary valve 16 supported by 2 is provided to prevent the rotary valve 16 from moving in the axial direction of the shafts 17 and 20, and a seal 40 prevents leakage of fluid to the outside. A rotary seal 41 is provided on the outer periphery of the shaft 17, which also prevents leakage of fluid to the outside.

The operation and effect obtained by the configuration of the pressure control valve will be described below. As is clear from FIG. 3, the holes 24 and 25 constituting the variable orifices are completely closed when the valve is in the neutral position, and there is no power loss when the valve is in the neutral position. Regarding clogging caused by dust mixed in the fluid, the opening can be made large as shown in FIG. 4, so that even if dust is mixed, the dust itself flows away, so that a self-cleaning effect can be expected. For example, even if dust stays, it can be easily removed because the rotational driving force of the rotary valve 16 is large.

Further, in the present invention, the movable part is the rotary valve 1.
6, the output pressures P ₁ and P ₂ do not fluctuate and do not malfunction unless an external impact acts, unless an impact in the rotational direction (actually impossible) acts. . In addition, since the driving force of the stepping motor 12 is directly transmitted to the rotary valve 16 without any intervention of a gear mechanism or the like, there is no reduction in responsiveness due to inertia or reduction in accuracy due to backlash.

In the above embodiment, two variable orifice holes 24 and 25 and one drain hole 38 are formed in the middle of the valve body. However, the present invention is not limited to this.
One variable orifice hole and two drain holes may be formed. In this case, when one of the variable orifice holes communicates with one of the drain holes, the other variable orifice hole needs to be formed so as not to communicate with the other drain. Further, the structure of the pressure control valve is the same as that of the above-described embodiment.
By selectively communicating the ports 4 and 25 with the drain port 27, not only the output pressures P ₁ and P ₂ are controlled, but also
Other known valve structures, such as providing one supply port, two output ports, and two drain ports in a valve body, and connecting a supply port and one output port by a rotary valve, A structure that allows the drain port to communicate with the other output port may be used.

Next, a method of driving the stepping motor 12 for operating the rotary valve 16 will be described. Here, in order to make it easier to understand the gist of the present invention, a case of a two-phase stepping motor will be described in detail. If the electric signals given to the A phase and the B phase of the stepping motor 12 are controlled by the procedure shown in FIG. 1, the resolution is only the basic step angle P. That is, the minimum angle is 1.8 degrees. However, FIG.
4, when the output pressure greatly changes only by rotating the rotary valve 16 by a small angle, there is a case where fine pressure control cannot be performed at the basic step angle P = 1.8 degrees. is there. Therefore, if the following control is performed, the specific rotation position of the rotary valve 16 can be controlled with an infinitesimal resolution, and the pressure can be controlled with high precision. That is, when 4P in FIG. 1 is defined as one cycle, the signals to be applied to the A phase and the B phase are shifted by 周期 cycle, in other words, the electric power having the trigonometric function relationship of cos and sin respectively in the A phase and the B phase. If a signal can be given, any rotational position within a rotational angle of 4P can be controlled with an infinitesimal resolution. More specifically, when a current proportional to cos θ is applied to phase A and sin θ is applied to phase B, an arbitrary rotational position within a rotation angle 4P can be controlled as described above. Here, θ indicates an arbitrary value of 0 to 2π.

The above trigonometric function is a microprocessor,
Alternatively, the relationship between the trigonometric functions can be easily obtained by a method of storing the relationship in a ROM or the like in advance. However, in order to convert the electric signals to be applied to the A and B phases of the stepping motor, D / A conversion is added. Required and not economical. Therefore, an example of an optimal control method of the stepping motor will be specifically described below with reference to FIGS.

Reference numeral 39 denotes an oscillator whose voltage changes in a trigonometric function according to time. For example, a quadrature oscillation circuit disclosed in Japanese Patent Publication No. 6-66587 can be used. A voltage that changes in a sin state at the output terminal 40, and the output terminal 4
1 are output in the form of cos-like voltages.
A and B have a period of T seconds.

The sine-shaped voltage signal is applied to the positive input of the comparator 42, and the output 43 obtains a rectangular wave shown in FIG. This waveform C is differentiated by a capacitor 44 and a resistor 45, and a waveform D is obtained at an output terminal 46 thereof. The waveform D is compared with the voltage V _2, the output waveform of the comparator 47 in FIG. 6
The analog switch 48 is turned ON-OF.
F. A constant current determined by the voltage V ₀ flows through the resistor 50 to the negative input of the operational amplifier 49. Since the integrating capacitor 51 is connected between the output and the negative input of the operational amplifier 49, a voltage F that changes at a constant gradient is obtained at the output 53 of the operational amplifier 49 as shown in FIG. As described above, the analog switch 48 is turned ON by the signal E in FIG.
reset to v. The resistor 52 is a protection resistor for the analog switch 48.

In this manner, a saw-toothed voltage signal F is obtained as shown in FIG.
Is connected to the positive input, it is compared with the voltages V ₁ applied to the negative input. Therefore, the output of the comparator 54 is
A gate signal having a time width corresponding to V ₁ as shown by G in FIG. This gate signal is differentiated by the capacitor 55 and the resistor 56 to obtain the waveform H of FIG. This waveform is compared with the voltage V _{3 by the} comparator 57 to obtain a signal I shown in FIG. This signal sets the analog switches 59 and 60 to O
N-OFF.

The analog switch 59 is connected to a circuit composed of a sin-shaped voltage signal circuit 40 and an operational amplifier 65, and the analog switch 60 is connected to a circuit composed of a cos-shaped voltage signal circuit 41 and an operational amplifier 66. Resistance 6
1 and 63 are protection resistors for the analog switches 59 and 60, and the capacitors 62 and 64 serve as charge capacitors. Since the operational amplifiers 65 and 66 are voltage followers, the voltages of A and B in FIG. 6 at the time when the pulse shown by I in FIG. 6 falls are held. Is cos2πt
/ T are obtained, which are good to apply to the B and A phases of the stepping motor.

As is clear from the above description, if the analog voltage V ₁ is changed, t is changed arbitrarily (except strictly except for the reset time indicated by E in FIG. 6) within the range of the period T. Can be done. Therefore, an electric signal having a necessary trigonometric function relationship can be given to the A phase and the B phase of the stepping motor, and as a result, the rotation angle position of the stepping motor can be arbitrarily controlled within an angle of about 4P by the analog voltage signal. You can do it.

Now, regarding the period T shown in FIG. 6, specifically, the circuit of FIG. 5 easily operates even at 0.1 msec (10 KHz) or a shorter period. The pressure control device described in the present invention controls the pressure of the fluid,
For example, even if hydraulic pressure is assumed to be an incompressible fluid, it is sufficient to consider a response of about 200 Hz. Accordingly, 10 KHz used in the driving method of the stepping motor proposed in the present invention is quite negligible, between the practical rotation position of the analog voltage V ₁ and the stepping motor described above, the stepping motor rotor inertia, A Phase And B
It can be considered that there is no delay other than the response delay caused by the inductance of the phase coil.

Although the description has been given of the case of the two-phase stepping motor, the basic step angle P of the two-phase stepping motor which has been frequently used recently is 1.8 degrees, and the rotation angle 4P is 7.
Only twice. That is, the rotary valve 16 as shown in FIG.
, It can rotate only 3.6 degrees left and right. While this angle (7.2 degrees) may be sufficient for certain applications, larger angles of rotation may be required for other applications. Although it is possible to select a two-phase stepping motor having a large basic step angle, the output torque and the response are inferior. On the other hand, in the case of a three-phase stepping motor, the basic step angle P is 3.75 degrees,
Those having excellent output torque and responsiveness are commercially available, and have a feature that they can be applied to a wide range of fields because the rotation angle is 6P, that is, 22.5 degrees. For example,
When applied to a rotary valve 16 as shown in FIG.
Since the rotation can be performed by 1.25 degrees, the change in the opening degree of the variable orifice holes 24 and 25 can be increased, and the control range of the output pressures P ₁ and P ₂ can be expanded.

The case of a three-phase stepping motor will be described below. FIG. 7 shows a conventional driving method of a general three-phase stepping motor. When three electric signals as shown in FIG. 7 are applied to three (U, V and W phase) coils of the stepping motor, a two-phase coil is formed. Like the stepping motor, the motor rotates by the basic step angle P degrees. In FIG. 7, when a positive current is applied to the U phase, a non-excitation is applied to the V phase, and a negative current is applied to the W phase, the motor rotates P degrees from the previous position and stops. Next, when a negative current is applied to the V phase while a positive current is applied to the U phase and the W phase is de-energized, the motor further rotates by P degrees and stops. As described above, when the U, V, and W phases are excited by the procedure shown in FIG.
The stepping motor keeps rotating with P degrees as the basic step angle. As is clear from FIG. 7, the same operation is repeated after 6P.

Here, focusing on the region within the rotation angle of 6P, if the electric signals applied to the U, V and W phases are set to three levels of positive, no, and negative, the resolution is only P degrees. By using the following method, a specific rotational position can be controlled with infinitesimal resolution. That is, if 6P in FIG. 7 is one cycle,
The signals to be applied to the U, V, and W phases are shifted by 周期 cycle, that is, sin θ, s are applied to the U, V, and W phases, respectively.
If an electric signal having a trigonometric function relationship of in (θ-240 °) and sin (θ-120 °) can be given, an arbitrary rotation position within a rotation angle of 6P can be controlled with infinite resolution.

In the case of three phases, since sin θ + sin (θ−240 °) + sin (θ−120 °) = 0 holds, the electric signals to be applied to the U, V and W phases can be easily obtained. Can be. That is, if an electric signal to be applied to the U-phase and the W-phase can be obtained, since U + W + V = 0 from the equation (1), V can be obtained in a relationship of V = −U−W (2).

In FIG. 8, U is sin θ, and W is sin
(Θ-120 °). The waveforms of C to I in FIG. 6 are completely the same even in the case of the three-phase stepping motor, and thus are omitted here.

FIG. 9 shows an example of a drive circuit for a three-phase stepping motor. Components having the same functions as those in FIG. 5 are denoted by the same reference numerals. One of the differences between FIG. 5 and FIG. 9 is that in FIG.
Output two signals of sin θ and sin (θ−120 °). Of course, sin θ and sin (θ−24
0 °), and the most economical combination may be selected. Another difference is that in FIG.
That is, an adder circuit including 4, 75, 76 and an operational amplifier 77 is added. In the case of this example, a method of obtaining V by addition is shown.

In the above embodiment, an example is shown in which the stepping motor is applied to a rotary type pressure control valve. However, the present invention is not limited to this, and the present invention can be applied to an apparatus that needs to control a minute rotation angle. is there.

[0036]

As is apparent from the above description, according to the present invention, in a stepping motor having two or three coils, a triangular function relationship having a phase shift of 90 degrees or 120 degrees is applied to these coils. By giving an electric signal having the same, the position of the rotary shaft is controlled within an angle range of 4 times or 6P of the basic step angle P, so that any rotational position within the rotational angle of 4P or 6P can be adjusted to an infinite resolution. Can be controlled by Therefore, extremely fine rotation control can be performed while utilizing the characteristics of the stepping motor.

[Brief description of the drawings]

FIG. 1 is a signal waveform diagram showing a general driving method of a two-phase stepping motor.

FIG. 2 is a longitudinal sectional view of an example of a fluid pressure control device to which the present invention is applied.

FIG. 3 is a sectional view taken along line NN of FIG. 2;

FIG. 4 is a partial cross-sectional view showing a state where a rotary valve is rotated.

FIG. 5 is a circuit diagram of a control circuit of the two-phase stepping motor.

6 is a signal waveform diagram of each part of the control circuit of FIG.

FIG. 7 is a signal waveform diagram showing a general driving method of a three-phase stepping motor.

FIG. 8 is a signal waveform diagram illustrating a method for driving a three-phase stepping motor according to the present invention.

FIG. 9 is a circuit diagram of a control circuit of the three-phase stepping motor.

[Description of Signs] 12 Stepping motor 15 Rotary shaft 16 Rotary valve 27 Drain hole 28, 29 Output port 30, 31 Supply port

Claims (4)

[Claims] 1. A stepping motor having two coils, wherein an electric signal having a trigonometric function relationship with a phase shift of 90 degrees is given to each of the two coils, so that the position of the rotary shaft is changed to a basic step angle P. A method for driving a stepping motor, characterized in that control is performed within an angle range four times as large as the above. 2. A stepping motor having three coils, wherein an electric signal having a trigonometric function relationship with a phase shift of 120 degrees is given to each of the three coils to thereby determine the position of the rotary shaft and the basic step angle P. A method for driving a stepping motor, characterized in that control is performed within an angle range of six times as large as the above. 3. The method of driving a stepping motor according to claim 1, wherein the two sinusoidal electric signals whose phases are shifted by 90 degrees are transmitted for one cycle T.
By holding the sample at time t within time t
Sin (2πt / T) and cos (2πt /
T) and a voltage proportional to
A method for driving a stepping motor, wherein the method is applied to each of a plurality of coils. 4. The stepping motor driving method according to claim 2, wherein two sinusoidal electric signals whose phases are shifted by 120 degrees are sampled and held at a time t within one cycle T to correspond to the time t. sin (2πt / T) and sin (2πt /
T-2π / 3) or sin (2πt / T-4π / 3)
And two voltages proportional to the following are obtained, and by adding these voltages, the remaining sin (2πt / T−4π /
3) A method of driving a stepping motor, which obtains voltages proportional to sin (2πt / T−2π / 3) and applies these voltages to three coils, respectively.