JP4762779B2 - Three-phase motor control device - Google Patents

Description

  The present invention relates to a control device for a three-phase motor having three phase coils different from each other.

Conventionally, a three-phase motor having three different phase coils of a U-phase coil, a V-phase coil, and a W-phase coil has been used in various applications such as industrial robots. Various control devices for controlling the three-phase motor have been proposed.
For example, in the prior art described in Patent Document 1, position detection means for detecting the relative positional relationship between the phase coil of the stator and the magnetic pole of the rotor, and a current in a predetermined phase coil according to the output from the position detection means Current switching means for switching the supply current so as to flow, current control means connected in series to the phase coil to control the supply current to the phase coil to a predetermined value, and a voltage applied to the current control means is detected. Thus, there has been proposed a brushless motor drive circuit including applied voltage control means for controlling a voltage applied to a series circuit of a current control means and a phase coil so that the voltage becomes a predetermined voltage. This makes it possible to reduce electromagnetic noise and mechanical noise during motor rotation with low power consumption, which is optimal as a spindle motor drive circuit for hard disk drives, and to reduce the capacitor capacity value of the snubber circuit or the snubber circuit itself. A drive circuit for a brushless motor that can be omitted and is inexpensive and has a small mounting area has been proposed.
In the prior art described in Patent Document 2, a vector calculation unit for obtaining a primary current command value, a slip angular frequency, and a phase change amount of magnetic flux, a primary angular frequency calculation unit, a pulse signal generation unit, and a pulse signal generation A frequency dividing unit that divides the output pulse signal of the unit, a data table that stores data of U and V phase sine wave signals, a primary current waveform output unit, and a primary current command value of the U and V phases are obtained. There has been proposed a vector control device for an induction motor including a multiplication unit, a phase voltage calculation unit for obtaining a three-phase voltage command value, and a PWM control unit. As a result, a vector control device for an induction motor has been proposed in which high-speed torque response can be obtained and high-precision speed control can be performed in a wide frequency range.
JP-A-6-165576 Japanese Examined Patent Publication No. 7-59157

In the prior art described in Patent Document 1, a circuit that detects a back electromotive voltage in all three-phase coils of a U-phase coil, a V-phase coil, and a W-phase coil (diodes D1 to D3, OP in FIG. 1 of Patent Document 1). Amplifiers 5-7) are provided, which increases space and cost. Since “current iu flowing into the U-phase coil” + “current iv flowing into the V-phase coil” + “current iw flowing into the W-phase coil” = 0, in general, a detection circuit for the W-phase coil Is omitted.
In the prior art described in Patent Document 2, the W-phase coil detection circuit is omitted in FIG. 1 of Patent Document 2, and the current iu flowing into the U-phase coil and the current iv flowing into the V-phase coil are used. A configuration for calculating the current flowing into the W-phase coil is shown. In this case, if the current flowing into the W-phase coil is iw, it can be expressed as iw = − (iu + iv). Further, in FIG. 1 of Patent Document 2, the current control amplifier 29 to which the current iu is input converts the current to the voltage Vu, and the current control amplifier 30 to which the current iv is input converts the current to the voltage Vv. The inverting amplifier 32 calculates Vw indicating a voltage corresponding to the current of the W-phase coil as − (Vu + Vv). In the case of the circuit configuration shown in FIG. 1 of Patent Document 2, if there is a noise component superimposed in the path through which the current iu detected by the converter 26 is transmitted to the current control amplifier 29, the voltage Vu The actual voltage Vu ′ can be expressed as Vu ′ = Vu + Vn (Vn: voltage resulting from a noise component). Similarly, if there is a noise component superimposed in the path through which the current iv detected by the converter 28 is transmitted to the current control amplifier 30, the actual voltage Vv ′ of the voltage Vv can be expressed as Vv ′ = Vv + Vn. it can. When the actual voltage Vw ′ is calculated using these Vu ′ and Vv ′, Vw ′ = − (Vu ′ + Vv ′) = − Vu−Vn−Vv−Vn = − (Vu + Vv) −2Vn, and the noise component Vn. Is amplified twice and reflected in the voltage Vw of the W-phase coil, which greatly affects the control accuracy.
This state is shown in a voltage waveform using FIG. FIG. 2A shows ideal waveforms of the voltage Vu, the voltage Vv, and the voltage Vw.
On the other hand, FIG. 2B shows the voltage waveform of the actual voltage Vu ′ of the voltage Vu (result of converting the current detected from the U-phase coil into a voltage), and noise N is superimposed at a certain timing, A state in which a noise component + Vn is superimposed at the position is shown.
2C shows a voltage waveform of the actual voltage Vv ′ of the voltage Vv (result of converting the current detected from the V-phase coil into a voltage), which is the same as the noise N shown in FIG. The noise N is superimposed at the timing, and the noise component + Vn is superimposed at the position.
FIG. 2D shows a voltage waveform of the actual voltage Vw ′ of the voltage Vw. Since Vw ′ is obtained from the calculation result of − (Vu ′ + Vv ′), the noise component + Vn of Vu ′ and the noise component + Vn of Vv ′ are doubled and 2 * (− Vn) noise in the negative direction. Ingredients appear. This noise has a great influence on the control accuracy.

  The present invention was devised in view of such a point, and detects currents supplied to two phase coils in a three-phase motor having three phase coils, and detects the remaining one phase coil. It is an object of the present invention to provide a control device for a three-phase motor that can more accurately determine the current supplied to the remaining one phase coil when the supplied current is calculated.

As means for solving the above-mentioned problems, a first invention of the present invention is a control device for a three-phase motor as described in claim 1.
The control device for a three-phase motor according to claim 1 is a control device for a three-phase motor having three different phase coils.
The control device includes: a first current detection unit that detects a direction and a magnitude of a current flowing through any one of the phase coils; and a direction of a current that flows through any phase coil different from the first current detection unit. Second current detecting means for detecting the magnitude, first voltage converting means for converting the current detected by the first current detecting means into voltage, and current detected by the second current detecting means as voltage. Based on the second voltage conversion means for conversion, the added value of the voltage converted by the first voltage conversion means and the voltage converted by the second voltage conversion means, the first current detection means is also the above-mentioned And calculating means for calculating the voltage of the phase coil that is not detected by the second detecting means.
The current detected by one of the first current detection means and the second current detection means is configured so that the positive / negative polarity is reversed with respect to the current detected by the other, The voltage converted by either one of the 1 voltage conversion means and the second voltage conversion means is configured such that the positive and negative polarities are reversed with respect to the voltage converted by the other.

If the control device for a three-phase motor according to claim 1 is used, for example, as shown in FIGS. 1A and 1B, the current detected by the second current detecting means is detected by the first current detecting means. The positive and negative polarities are reversed with respect to the current so that the voltage converted by the second voltage converting means is opposite in polarity to the voltage converted by the first voltage converting means. (In this case, the configuration of the first voltage conversion means is the same as that shown in FIG. 6B).
In this case, as shown in the voltage waveform of FIG. 3, the actual voltage waveform Vu ′ of the U-phase coil [= Vu (ideal waveform) + Vn (noise component, pulsed noise N superimposed in the positive direction)] and actual Voltage waveform Vv ″ [= Vv (ideal waveform) −Vn (which is a noise component, and pulse noise N is superimposed in the negative direction)] obtained by inverting the voltage waveform Vv ′ of the V-phase coil.
The voltage waveform Vw ′ of the W-phase coil can be obtained from Vw ′ = − (Vu ′ + Vv ″) = − (Vu + Vn + Vv−Vn) = − (Vu + Vv), and the voltage waveform of the V-phase coil is inverted. The noise component Vn is canceled by making the polarity (reverse the positive and negative polarities).
Thereby, it is possible to more accurately obtain the current of one phase coil (convertible from the voltage) obtained by calculation based on the detected value from the other phase coil without detecting the actual current.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1A and 1B show an example of the configuration of an embodiment of the control device 1 of the present invention, and FIGS. 6A and 6B show an example of the configuration of a conventional control device 100. FIG. Is shown.
● [Configuration of control device 1 (Fig. 1)]
A control device 1 (a control device for a three-phase motor) of the present invention shown in FIG. 1A is a three-phase motor having three different phase coils (U-phase coil Cu, V-phase coil Cv, and W-phase coil Cw). A control device that controls M.
The control device 1 includes a calculation means 10 (for example, a CPU) for obtaining each current supplied to the three phase coils, and a current output means 20 for supplying each current to the three phase coils based on a signal from the calculation means 10. (For example, a PWM inverter), a first current detection means 30u (for example, a current sensor) for detecting the direction and magnitude of a current flowing through any one of the phase coils (in this case, the U-phase coil Cu), and a first current Second current detection means 30v (for example, a current sensor) for detecting the direction and magnitude of the current flowing in any of phase coils different from the detection means 30u (in this case, V-phase coil Cv), and first current detection means 30u. The first voltage conversion means Au (for example, an operational amplifier) that converts the current detected in Step 1 into voltage, and the second voltage conversion means Av that converts the current detected in the second current detection means 30v into voltage. And a (e.g. operational amplifiers).
In the example of FIG. 1A showing the control device 1 of the present invention and the example of FIG. 6A showing the conventional control device 100, the calculation means 10 is connected to the first voltage conversion means Au via the AD converter 40. The voltage Vu ′ output from the digital signal is converted into a digital value, and the voltage Vu ″ output from the second voltage conversion unit AvC (the voltage Vv ′ output from the voltage conversion unit Av in the example of FIG. 6A). However, the AD converter 40 may be included in the arithmetic means 10.
Further, the (control) command value may be obtained by the computing means 10, or the command value obtained by an external device may be inputted to the computing means 10 (not shown).

The arithmetic means 10 shown in FIG. 1A is based on the added value of the voltage Vu ′ converted by the first voltage conversion means Au and the voltage Vv ″ converted by the second voltage conversion means AvC. The voltage of the phase coil (in this case, the W-phase coil Cw) which is not detected by the first current detection means 30u and the second current detection means 30v is calculated.
Since the U-phase coil Cu, the V-phase coil Cv, and the W-phase coil Cw are connected at the point P, the current Iu supplied to the U-phase coil, the current Iv supplied to the V-phase coil, and the W-phase coil The sum total with the supplied current Iw becomes zero (Iu + Iv + Iw = 0). Therefore, when each current is converted into a voltage with a common coefficient A, the voltage Vu obtained from the current supplied to the U-phase coil can be expressed as A * Iu, and obtained from the current supplied to the V-phase coil. The voltage Vv can be expressed as A * Iv, and the voltage Vw obtained from the current supplied to the W-phase coil can be expressed as A * Iw. In this case, since Vu + Vv + Vw = 0, if Vu and Vv are detected, Vw can be obtained by calculation (Vw = − (Vu + Vv)).

The feature of the control device 1 of the present invention is that the polarity of one of the currents detected by the first current detection means 30u and the second current detection means 30v is reversed, and further the first voltage conversion means Au and the second The point is to obtain a voltage obtained by reversing the polarity of the positive and negative polarity again in one of the voltage conversion means AvC. 1A and 1B show the second voltage obtained by inverting the positive / negative polarity of the current detected by the second current converter 30u with respect to the current detected by the first current converter 30v. An example is shown in which the voltage converted by the converter AvC is inverted in polarity between the voltage converted by the first voltage converter Au. In this case, the voltage Vw of the W-phase coil Cw calculated by the calculation means 10 is − (Vu + Vv).
Note that the current detected by the second current detection means 30v may be inverted to invert the voltage converted by the first voltage conversion means Au instead of the second voltage conversion means AvC (not shown). In this case, since the polarities of both the voltage Vu and the voltage Vv are opposite to the above, the voltage Vw of the W-phase coil Cw calculated by the calculation means 10 is − (− Vu−Vv) = Vu + Vv.
In this way, the current detected by one of the first current detection means 30u and the second current detection means 30v is configured so that the positive / negative polarity is reversed with respect to the current detected by the other, The voltage converted by one of the first voltage conversion means Au and the second voltage conversion means AvC is configured such that the positive and negative polarities are opposite to the voltage converted by the other.

Moreover, in the control apparatus 1 of this Embodiment shown to FIG. 1 (A) and the conventional control apparatus 100 shown to FIG. 6 (A), the same code | symbol is provided to the same component.
In this example, the second current detection means 30v is the same in both cases, but in the present embodiment shown in FIG. 1A, the signal extraction wiring Liv is different from the conventional one shown in FIG. The polarity of the detection current is reversed by reversing the connection. Thus, in the prior art shown in FIG. 6 (A), the detection current iu of the second current detection means 30v flows toward the second voltage conversion means Av. In the present embodiment shown in FIG. The detection current iu of the two current detection means 30v is changed in the direction of flowing toward the second current detection means 30v (configured so that the positive and negative polarities are reversed).

In the present embodiment shown in FIG. 1A, the second voltage conversion means AvC inverts the positive / negative polarity of the current detected by the second current detection means 30v to convert it into a voltage, or the second voltage conversion. The polarity of the voltage converted by means AvC is inverted.
FIG. 6B shows an example of the configuration of the conventional second voltage conversion means Av. A resistor R is connected to the wiring Liv, and a voltage Vv ′ across the resistor R is taken out. This configuration is the same for the first voltage conversion means Au shown in FIGS. 6 (A) and 1 (A).
On the other hand, in the present embodiment shown in the left diagram of FIG. 1B, an example in which the polarity of the input current is inverted and converted into the voltage Vv ″ is shown, and the resistance R of the wiring Liv is shown. The connection destination is changed. As a result, the current iv with the positive and negative polarities reversed is restored by inverting the positive and negative polarities again.
1B shows an example in which the polarity of the voltage converted from the input current is inverted, and the output of the operational amplifier connected to the resistor R is inverted. I am letting. As a result, the voltage converted from the current iv in which the positive and negative polarities are inverted is restored by inverting the positive and negative polarities again.

[Effect 1 of the present invention (noise cancellation (FIGS. 2 and 3))]
FIG. 2 shows a U-phase coil voltage Vu ′ (FIG. 2B) based on the current detected by the first current detection means 30u by the conventional control device 100 (see FIG. 6A), a second The voltage Vv ′ of the V-phase coil (FIG. 2C) based on the current detected by the current detection means 30v, and the voltage Vw ′ of the W-phase coil calculated from the voltage Vu ′ and the voltage Vv ′ ( FIG. 2D shows an example of Vw ′ = − (Vu ′ + Vv ′)). FIG. 2A shows an example of ideal voltage waveforms of the voltage Vu, the voltage Vv, and the voltage Vw.
In this case, noise N (+ Vn noise) superimposed on both the wirings Liv and Liu of the control device 100 is superimposed on both the voltage Vu ′ and the voltage Vv ′. When the voltage Vw ′ is calculated using the voltage Vu ′ and the voltage Vv ′, the influence of the noise N is amplified (2 * (− Vn) noise appears).

FIG. 3 shows the voltage Vu ′ of the U-phase coil based on the current detected by the first current detection means 30u by the control device 1 (see FIG. 1A) in the present embodiment (FIG. 3B). And the V phase voltage Vv ″ (FIG. 3C) based on the current detected by the second current detection means 30v, and the W phase obtained by calculation from the voltage Vu ′ and the voltage Vv ″. An example of the coil voltage Vw ′ (FIG. 3D, Vw ′ = − (Vu ′ + Vv ″)) is shown. FIG. 3A shows an example of ideal voltage waveforms of the voltage Vu, the voltage Vv, and the voltage Vw.
In this case, the voltage Vu ′ (FIG. 3B) of the U-phase coil is the same as the conventional voltage (FIG. 2B), but the voltage Vv ″ (FIG. 3C) of the V-phase coil is By performing the inversion, the noise N appears in the reverse direction (−Vn). As a result, the noise N is canceled by Vu ′ + Vv ″, and the influence of the noise N does not appear on the voltage Vw ′ of the W-phase coil obtained by calculation.

[Effect 2 of the present invention (cancellation of voltage drift (FIGS. 4 and 5))]
FIG. 4 shows a U-phase coil voltage Vu ′ (FIG. 4B) based on the current detected by the first current detection means 30u by the conventional control device 100 (see FIG. 6A), a second The voltage Vv ′ of the V-phase coil (FIG. 4C) based on the current detected by the current detection means 30v and the voltage Vw ′ of the W-phase coil obtained by calculation from the voltage Vu ′ and the voltage Vv ′ ( FIG. 4D shows an example of Vw ′ = − (Vu ′ + Vv ′)). FIG. 4A shows an example of ideal voltage waveforms of the voltage Vu, the voltage Vv, and the voltage Vw.
In this case, voltage drift (+ ΔV drift) due to floating of the reference GND, offset error of the voltage conversion means, etc. occurs in both the voltage Vu ′ and the voltage Vv ′. When the voltage Vw ′ is calculated using the voltage Vu ′ and the voltage Vv ′, the influence of the voltage drift is amplified (2 * (− ΔV) drift appears).

FIG. 5 shows the voltage Vu ′ of the U-phase coil based on the current detected by the first current detection means 30u by the control device 1 (see FIG. 1A) in the present embodiment (FIG. 5B). And the V phase voltage Vv ″ (FIG. 5C) based on the current detected by the second current detecting means 30v and the W phase obtained by calculation from the voltage Vu ′ and the voltage Vv ″. An example of the coil voltage Vw ′ (FIG. 5D, Vw ′ = − (Vu ′ + Vv ″)) is shown. FIG. 5A shows an example of ideal voltage waveforms of the voltage Vu, the voltage Vv, and the voltage Vw.
In this case, the voltage Vu ′ (FIG. 5B) of the U-phase coil is the same as the conventional voltage (FIG. 4B), but the voltage Vv ″ (FIG. 5C) of the V-phase coil is By performing inversion, a voltage drift appears in the reverse direction (−ΔV). Thereby, the voltage drift is canceled by Vu ′ + Vv ″, and the influence of the voltage drift (ΔV) does not appear in the voltage Vw ′ of the W-phase coil obtained by the calculation.

  The control device 1 (a control device for a three-phase motor) of the present invention is not limited to the configuration, processing, connection, and the like described in the present embodiment, and various changes, additions, and deletions are possible without changing the gist of the present invention. Is possible.

  The control device 1 (control device for a three-phase motor) according to the present invention can be applied to various devices using a three-phase motor, such as an industrial robot, and control devices for a system.

It is a figure explaining the structure of one Embodiment of the control apparatus 1 of this invention. It is a figure explaining the waveform of voltage Vu ', voltage Vv', and voltage Vw 'by the conventional control apparatus 100. FIG. It is a figure explaining the waveform of voltage Vu ', voltage Vv ", and voltage Vw' by the control apparatus 1 of this invention. It is a figure explaining the waveform of voltage Vu ', voltage Vv', and voltage Vw 'by the conventional control apparatus 100. FIG. It is a figure explaining the waveform of voltage Vu ', voltage Vv ", and voltage Vw' by the control apparatus 1 of this invention. It is a figure explaining the structure of the conventional control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus 10 Calculation means 20 Current output means 30u 1st current detection means 30v 2nd current detection means Au 1st voltage conversion means AvC 2nd voltage conversion means Liu, Liv wiring M 3 phase motor Cu U phase coil Cv V phase coil Cw W phase coil R Resistance

Claims (1)

A control device for a three-phase motor having three different phase coils,
First current detection means for detecting a current flowing in any one of the phase coils;
Second current detection means for detecting a current flowing in any of phase coils different from the first current detection means;
First voltage conversion means for converting a current detected by the first current detection means into a voltage;
Second voltage conversion means for converting the current detected by the second current detection means into a voltage;
Neither the first current detection means nor the second detection means is detected based on the added value of the voltage converted by the first voltage conversion means and the voltage converted by the second voltage conversion means. Computing means for calculating the voltage of the phase coil,
The current detected by one of the first current detection means and the second current detection means is configured so that the positive and negative polarities are opposite to the current detected by the other,
The voltage converted by one of the first voltage conversion means and the second voltage conversion means is configured so that the positive and negative polarities are reversed with respect to the voltage converted by the other.
A control device for a three-phase motor.

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