JPH08308287A - Motor driving circuit - Google Patents

Abstract

PURPOSE: To obtain the smooth torque having small pulsation of the torque of a motor by driving the motor based on the output signal of a phase waveform converter for converting a plurality of phases having different phases to the waveforms of an AC current and outputting the output signal. CONSTITUTION: Trapezoidal waveform data, for example, is stored in a data storage unit 8. The waveform data read from the unit 8 is used to match the rotation of a motor 5, converted to a plurality of phases of AC waveforms having different phases by a phase waveform converter 9, and the AC current based on the converted AC waveform is supplied to the motor 5. Then, the torque of the motor 5 is increased at the time of the maximum torque generated by the currents of the phases, the time from when the maximum torque of the one phase starts to be decreased to when the torque generated by the current of the other phase becomes maximum is shortened, and the pulsation of the generated torque is decreased. Thus, the torque of the motor 5 can be smoothened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit.

[0002]

2. Description of the Related Art A three-phase brushless motor is driven by a three-phase alternating current. Figure 6 shows a general electronic publishing company in 1987 3
FIG. 2 is a block diagram of a brushless servomotor system shown in FIG. 26, page 22, “Basics and Applications of Brushless Servo Motor” issued on 20th March. In this brushless servomotor system, a DC voltage obtained by rectifying the AC voltage of the AC power supply A by the rectification bridge B is input to the transistor bridge C to generate a 3-phase AC voltage, and the 3-phase AC voltage is supplied to the 3-phase brushless motor SM. Supply and drive the 3-phase brushless motor SM.

When the three-phase brushless motor SM is driven, the rotary encoder RE outputs a pulse for each predetermined rotation angle of the three-phase brushless motor SM, and the pulse is input to the speed detection circuit D and the rotor position detection circuit E. Then, the speed detection circuit D outputs the speed feedback signal SF corresponding to the rotation speed of the three-phase brushless motor SM by the input pulse, and determines the difference between this speed feedback signal SF and the reference speed signal SS that commands the rotation speed. The corresponding DC voltage is input to the DC-SIN conversion circuit F that converts the DC voltage into a sine wave. The rotor position detection circuit E also inputs a detection signal for detecting the rotor position of the three-phase brushless motor SM to the sine wave generation circuit G by the input pulse.

Then, the sine wave generating circuit G generates a sine wave having a phase corresponding to the detected rotor position, and inputs this sine wave to the DC-SIN conversion circuit F. The DC-SIN conversion circuit F converts into a sine wave that is phase-shifted according to the DC voltage input thereto. Converted sine wave and current feedback signal IF that detected the current of 3-phase brushless motor SM
A three-phase AC waveform of a sine wave is created by the difference between and. Comparing the created three-phase AC waveform with a triangular wave of a predetermined frequency output from the triangular wave generating circuit H, the comparators I _U , I _V ,
Comparing the magnitudes by inputting them to I _W , the comparators I _U , I
PWM of pulse width modulated from _V , I _W by triangular wave
The signal is output. If the transistor of the transistor bridge H is turned on and off by this PWM signal, it will be 3
The three-phase brushless motor SM is supplied with a three-phase alternating current according to the difference between the reference speed signal SS and the speed feedback signal SF, and the three-phase brushless motor SM is driven at the rotation speed based on the reference speed signal SS.

[0005]

The torque of the motor is determined by the product of the magnetic field of the motor and the motor current. Figure 7
As shown in the relationship between the torque amplitude on the vertical axis and the motor current phase angle on the horizontal axis, when a motor is driven by a sine wave three-phase motor current, it is generated by the motor current for each U, V, W phase. torque of the motor, the torque waveform W _U phase is shifted 120 ° from each other, W _V, varies sinusoidally as W _W.

The torque continuously obtained from the motor
Is the torque waveform W_U, W _V, W_WThe torque of
Synthesized synthetic torque waveform W_TRMake a change like. Shi
Therefore, the torque of the motor is the combined torque waveform W_TRNo
Pulsation, the torque pulsation (ripple) is large and smooth
There is a problem that it cannot obtain a proper torque. Is the present invention
In consideration of the problem that occurs,
Aiming to provide a motor drive circuit that can obtain
I do.

[0007]

A motor drive circuit according to a first aspect of the present invention is a motor drive circuit which supplies an alternating current to a motor to drive the motor, and a data storage section which stores non-sinusoidal waveform data. A phase waveform converter that converts the waveform data read from the data storage unit into a waveform signal of alternating current of a plurality of phases different from each other and outputs the waveform signal, based on the output signal of the phase waveform converter. It is characterized in that it is configured to drive a motor.

A motor drive circuit according to a second aspect of the present invention is characterized in that a data rewritable memory is used as the data storage section.

A motor drive circuit according to a third aspect of the present invention is a motor drive circuit which supplies an alternating current to a motor to drive the motor, and stores a formula storage section for storing a formula for obtaining a value of a waveform signal that does not cause the torque of the motor to pulsate. And a numerical value output section for outputting a numerical value based on the rotation speed of the motor so as to be substituted into the function of the formula, and alternating currents of a plurality of phases having different phases based on the value of the waveform signal obtained by calculating the formula. And a phase waveform conversion unit for converting the waveform signal into a waveform signal of 1., and is configured to drive the motor based on the output signal of the phase waveform conversion unit.

[0010]

In the first aspect of the present invention, the trapezoidal waveform data shown in FIG. 2, which is a non-sinusoidal wave that does not cause pulsation in the motor torque, is stored in the data storage unit in accordance with the characteristics of the motor to be driven. Using the waveform data read from the waveform data storage unit in accordance with the rotation of the motor, it is converted into AC waveforms of multiple phases with different phases, and the AC current based on the converted AC waveforms is supplied to the motor. As shown in FIG. 4, the time of maximum torque generated by the current of each phase becomes long, and the time from when the maximum torque of one phase begins to decrease until the torque generated by the current of the other phase becomes maximum. Is shortened, and the pulsation of the generated torque is reduced. As a result, the torque of the motor can be made smooth.

According to the second aspect of the invention, the waveform data in the memory is rewritten using a memory capable of rewriting data. An alternating current having a current waveform based on the rewritten waveform data is supplied to the motor. As a result, an alternating current having a current waveform in which the motor torque does not pulsate can be supplied to the motor, and the motor torque can be smoothed.

In the third aspect of the invention, the formula storage unit stores the formula of the waveform signal that does not cause the torque of the motor to pulsate. Substituting the numerical value based on the rotation speed of the motor into the function of the formula,
The value of the signal waveform is obtained in time series. When the alternating current waveform based on the converted alternating current waveform is supplied to the motor, the torque of the motor is generated by the current of each phase. The maximum torque time becomes long, the time from when the maximum torque of one phase starts to decrease until the torque generated by the current of the other phase becomes maximum, and the pulsation of the generated torque decreases. As a result, the torque of the motor can be made smooth.

[0013]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram showing the configuration of a motor drive circuit according to the present invention. The controller 1 outputs a pulse signal P ₁ having a cycle corresponding to the rotation speed of the three-phase motor 5 to be driven, and this pulse signal P ₁ is input to the deviation counter 2. This deviation counter 2 has 3
A pulse signal P ₂ output from the rotary encoder 6 interlocking with the phase motor 5 at each predetermined rotation angle of the three-phase motor 5.
Is entered. The rotation angle of the three-phase motor 5 corresponding to the pulse of one cycle of the pulse signal P _{2 and} the three-phase motor 5 in one cycle of the pulse signal P ₁ when the three-phase motor 5 rotates according to the setting of the pulse signal P _1. Is set equal to the rotation angle.

[0014] Deviation counter 2 is made up-down counter, the pulse signal P ₁ counts up, the pulse signal P ₂ is counting down, the deviation between the number of counts and the count number of the pulse signal P ₂ pulse signals P ₁ A deviation signal converted into a corresponding analog signal is output. This deviation signal is applied to the U-phase amplifier 3 _U , the V-phase amplifier 3 _V ,
Input to the W-phase amplifier 3 _W. The U-phase amplifier 3 _U , the V-phase amplifier 3 _V , and the W-phase amplifier 3 _W are supplied with the 3-phase waveform signal output from the phase waveform converter 9 as a gain control signal.

The U, V and W phase amplifiers 3 _U , 3 _V and 3 _W are respectively composed of a non-inverting amplifier and an inverting amplifier (not shown), and the deviation signal output from the deviation counter 2 is the non-inverting amplifier. And to the inverting amplifier as a torque control signal for the motor 5. The gains of these non-inverting amplifiers and inverting amplifiers are controlled by the three-phase waveform signals which are analog signals from the phase waveform converting section 9. When the polarity of the three-phase waveform signal is positive, the output signal of the non-inverting amplifier is selected by a selection switch (not shown) when it is negative.

The output signals of the U-phase amplifying section 3 _U , V-phase amplifying section 3 _V and W-phase amplifying section 3 _W generate U-phase current for generating an alternating current supplied to the 3-phase motor 5 based on the output signals. Part 4
Inputs to _U , V phase current generator 4 _V and W phase current generator 4 _W separately. The alternating current output from the U-phase current generator 4 _U , the V-phase current generator 4 _V , and the W-phase current generator 4 _W is supplied to the three-phase motor 5.

A pulse signal P ₂ output from the rotary encoder 6 every time the three-phase motor 5 rotates by a predetermined rotation angle.
Is input to the position counter 7 which generates an address signal for reading the data in the waveform data storage section 8. The address signal output from the position counter 7 after counting the pulses is input as a read address to the waveform data storage unit 8 including a PROM.

As shown in FIG. 2, the waveform data storage section 8 stores waveform data for one period of a trapezoidal waveform in association with addresses 0 to 255 in association with the addresses. The waveform data read from the waveform data storage unit 8 is input to the phase waveform conversion unit 9. The phase waveform converter 9 converts the time-series waveform data input thereto into an analog three-phase waveform signal having a phase difference of 120 °. The three-phase waveform signal output from the phase waveform converter 9 is input to the U-phase amplifier 3 _U , the V-phase amplifier 3 _V , and the W-phase amplifier 3 _W. The waveform data storage section 8 is provided with an external input terminal 8a so that the waveform data to be stored can be externally written.

Next, the operation of the motor drive circuit will be described with reference to the flow chart of FIG. 3 showing the conversion contents for converting the read waveform data into a three-phase waveform signal. Prior to driving the three-phase motor 5, the waveform data storage unit 8 does not pulsate the torque of the three-phase motor 5, for example, the non-sinusoidal waveform data shown in FIG. 2 is associated with the address of the waveform data storage unit 8. Store it. The rotary encoder 6 working in conjunction with the three-phase motor 5 outputs a pulse signal P ₂ each time the three-phase motor 5 rotates a predetermined rotation angle, and this pulse signal P ₂ is input to the deviation counter 2 and the position counter 7.

On the other hand, when the pulse signal P ₁ having a cycle corresponding to the rotation angle of the three-phase motor 5 is input from the controller 1 to the deviation counter 2, the deviation counter 2 receives the pulse signal P ₁
Is counted up and the pulse signal P ₂ is counted down, and the deviation signal of the analog signal corresponding to the deviation of both count values is output from the deviation counter 2, and the U, V, W phase amplifiers 3 _U , 3 _V , Input to 3 _W. In this way, the deviation signal output from the deviation counter 2 includes the rotation angle of the three-phase motor 5 corresponding to the pulse signal P ₁ within the same time and the rotation angle of the three-phase motor 5 detected by the rotary encoder 6. Corresponding to the difference, when the pulse number of the pulse signal P ₁ is larger (smaller) than the pulse number of the pulse signal P ₂ within the same time, the polarity of the deviation signal is positive (negative).

The position counter 7 counts the pulse signal P ₂ and outputs an address signal for reading the waveform data corresponding to the rotation angle of the three-phase motor 5 from the waveform data storage unit 2. For example, the U-phase start address signal A _S corresponding to address 0 in FIG. 2 is determined (S1), and then the waveform data is read from the waveform data storage unit 8 by the sequentially output address signal (S2), and the read waveform is read. The data is transferred to the phase waveform converter 9 (S3). Then the position counter 7
_{V = A U + (A E} -A S) / 3 ( where, A _U: U-phase address signal, A _V: V-phase address signal, A _S: start address signal of U-phase, A _E: U-phase end Address signal)
Outputs V-phase address signal A _V by (S4), reads the waveform data from the waveform data storage section 8 by the address signal A _V (S5), waveform data read out is transferred to the phase waveform converting section 9 (S6 ). The V-phase address signal A _V is offset from the U-phase address signal A _U by ( _AE- A _S ) / 3, and the waveform data is sequentially read from the address 85 shown in FIG.

Subsequently, A _W = A _U + 2 × (A _E −A _S ) /
3 (however, A _W : W-phase address signal) outputs the W-phase address signal A _W (S7), and the address signal A _W reads the waveform data from the waveform data storage unit 8 (S8). Is transferred to the phase waveform converter 9 (S9). This W-phase address signal A _W is 2 × the U-phase address signal A _U
Since (A _E -A _S ) / 3 is offset, the waveform data will be sequentially read from the address 170 shown in FIG.
When the three-phase motor 5 is rotating, the waveform data described above is read in time series.

As a result, the phase waveform converter 9 converts the time-series waveform data read by the U-phase address signal A _U into a U-phase waveform signal, and the time-series waveform data read by the V-phase address signal A _V. It is converted into a V-phase waveform signal and is converted into a W-phase waveform signal according to the time-series waveform data read by the W-phase address signal A _W. Then, the phase waveform converter 9 outputs analog three-phase waveform signals whose phases are shifted by 120 °.
The three-phase waveform signals are U, V, W phase amplifiers 3 _U , 3 _V , 3
_A gain control signal is input to a non-inverting amplifier and an inverting amplifier (not shown) forming _W to control the gains of the non-inverting amplifier and the inverting amplifier.

Here, the pulse signal P₁Count value and
Loose signal P₂If the count value of is equal, the deviation signal is
It becomes zero, and the U, V, and W phase amplifier 3_U, 3_V, 3_WSmell
The input of the non-inverting amplifier and the inverting amplifier becomes zero, and the output
The signal is zero. On the other hand, there is a difference in the count value and the deviation
If the signal is not zero, U, V, W phase amplifier 3_U, 3_V,
Three_WThe output signal is obtained from That is, the U, V, W phases
Amplifier 3_U, 3_V, 3 _WNon-inverting amplifier and inverting
The deviation signal is input to the amplifier and it responds to the three-phase waveform signal.
Amplified by the same gain, non-inverting amplifier and inverting amplifier
Output signal that is a deviation signal according to the gain controlled by
Be done.

When the polarity of the three-phase waveform signal is positive, the output signal of the non-inverting amplifier is selected, whereby the deviation signal is obtained by correcting the deviation signal with the value on the positive side of the three-phase waveform signal. When the polarity of the three-phase waveform signal is negative, the output signal of the inverting amplifier is selected, and the deviation signal is obtained by correcting the deviation signal with the negative value of the three-phase waveform signal. Thus U, V, W phase amplification unit 3 _U, 3 _V, 3 when the deviation signal is input to the _W, 3-phase one period the deviation signal based on the waveform data read out from the waveform data storage section 8 It will be corrected by the waveform signal. And it outputs the corrected deviation signals U, V, and W phase amplification unit _{3 U, 3 V, 3 W} .

Similarly, when the polarity of the deviation signal is negative
Will be corrected. If the detected speed is greater than the command speed,
On the contrary, when the polarity of the signal is positive, the detected speed is
The phase rotation direction of the deviation signal changes when it is small and negative
become. Therefore, U, V, W phase amplifier 3_U, 3_V, 3
_WOutput signal, that is, the polarity of the corrected deviation signal is positive
Contributes to the acceleration of the three-phase motor 5 and, on the contrary, in the case of negative
Changes by changing the phase rotation direction
Electromagnetic force is reduced, contributing to deceleration. And U, V, W phases
Amplifier 3_U, 3_V, 3_WOutput signal is U, V, W phase current
Generator 4_U, 4 _V, 4_WInput to U,
V, W phase current generator 4_U, 4_V, 4_WIs the input message
To generate three-phase AC current according to the
Then, the three-phase motor 5 is driven. And the polarity of the deviation signal
Is positive, the rotation speed of the three-phase motor 5 increases and negative
Decrease. The three-phase motor 5 has
When rotating in the opposite direction, the pole of the deviation signal
When the sex is positive, the rotation speed decreases, and when it is negative, the rotation speed increases.
It

In this way, when there is a difference between the count value of the pulse signal P _{1 and} the count value of the pulse signal P ₂ , the waveform data corresponding to the rotation angle of the three-phase motor 5 is used to determine 3 The current waveform of the 3-phase AC current supplied to the phase motor 5 is corrected to correct the torque of the 3-phase motor 5, and the pulsation of torque is suppressed to rotate the 3-phase motor 5. The count value of the pulse signals P _1, on the basis of the difference between the count value of the pulse signal P _2, resulting in stabilizing the rotational speed of the three-phase motor 5 from controlling the rotational speed of the three-phase motor 5. Further, since the non-sinusoidal waveform data in which the torque of the three-phase motor 5 does not pulsate is read from the waveform data storage unit 8, the pulsation of the torque of the driven three-phase motor 5 is suppressed and a smooth torque is obtained. be able to.

In this way, the three-phase motor 5 is driven,
When the relationship between the torque amplitude of the phase motor 5 and the phase angle of the three-phase alternating current was measured, the measurement results shown in FIG. 4 were obtained. The torque of the three-phase motor obtained from the motor currents of the U, V, and W phases is the torque waveform W _U ′, when the waveform data storage unit 8 stores the waveform data as shown in FIG.
It changes like a trapezoidal waveform like W _V ′ and W _W ′.
Then, the torque waveforms W _U ′, W _V ′, W _W ′ are combined,
The torque waveform W _TR continuously obtained from the three-phase motor 5 has an extremely small amplitude as apparent from FIG.
It was confirmed that smooth torque can be obtained from the three-phase motor 5. Since the external input terminal 8a is provided, the waveform data of the non-sinusoidal wave stored in the waveform data storage unit 8 is rewritten using the external input terminal 8a, for example, by a personal computer, so that the torque of the three-phase motor 5 is always smooth. You can also

On the other hand, as a method of obtaining a non-sinusoidal wave having an appropriate waveform, it is possible to use the formula storage section instead of the above-mentioned waveform data storage section 8. Then, in this formula storage unit, a formula f (θ) = A ₁ sin (θ) + A ₂ sin (3 ・ θ) + A ₃ sin (5 ・ θ) for calculating the waveform signal f (θ) that does not cause the motor torque to pulsate + (1) (A ₁ , A ₂ , A ₃ are natural numbers) is stored, and the address signal output from the position counter 7 is given to the formula storage unit so as to be substituted into the function θ.
When the formula is calculated, the waveform signal f (θ) corresponding to the address designated by the address signal is obtained, and the waveform signal f (θ) is obtained in time series according to the address signal. Therefore, by using such an equation, a waveform signal in which the motor torque does not pulsate is obtained, and a smooth torque can be obtained from the three-phase motor 5 as described above.

Generally, in a motor, when the current is constant, the electromagnetic force changes with a change in the magnetic field of the motor, and a torque constant proportional to the strength of the magnetic field of the motor can be obtained. Therefore, the pulsation of the torque increases due to the difference in the distribution of the magnetic field of the motor, that is, the combined torque that combines the torques generated by the motor currents of the respective phases is not zero due to the magnetic field characteristics of the motor. When a higher harmonic is superimposed on the non-sinusoidal waveform for determining the motor current waveform, the combined torque waveform W _TR shown in FIG.
As shown in, the torque ripple (ripple) is reduced.

FIG. 5 is a characteristic diagram in which the relationship between the amplitude ratio of the amplitude of the fundamental wave and the amplitude of the third harmonic and the torque ripple of the motor is measured. The vertical axis is the torque ripple and the horizontal axis is the amplitude ratio. I am trying. As is apparent from FIG. 5, when the amplitude of the fundamental wave is “1”, the torque ripple (pulsation) is reduced to about 2.8% when the amplitude of the third harmonic is set to “0.07”. Therefore, the torque pulsation of the motor can be reduced by selecting the amplitude of the third harmonic as such a value. Similarly, for other higher harmonics,
If a predetermined amplitude is selected for each, the pulsation of the torque of the motor can be further reduced. Therefore, if high-order harmonics are used, the pulsation of the motor torque can be reduced and smooth torque can be obtained even for motors having different magnetic field characteristics and different torque characteristics.

In this embodiment, the case where a three-phase motor is driven has been described, but it is not limited to a three-phase motor, and it goes without saying that other multi-phase motors or linear motors can be similarly driven. However, when applied to a linear motor, a position sensor (scale) that detects the amount of magnetic pole movement is used instead of a rotary encoder.

Further, in this embodiment, the deviation counter 2 and the phase waveform converter 9 output the analog signal, but a digital signal may be output. In that case, instead of the amplifier, a digital signal multiplier is used. use.

[0034]

As described in detail above, the first aspect of the present invention is provided with the data storage section for storing the data of the current waveform of the ratio sine wave in which the torque of the motor does not pulsate, and the waveform data of this data storage section is stored. By correcting the current waveform of the motor based on this, it is possible to suppress the pulsation of the torque of the motor. Since the second invention uses the PROM as the data storage unit, it is possible to rewrite the non-sinusoidal waveform data with a personal computer and suppress the pulsation of the motor torque by using the rewritten waveform data. The third invention corrects the current waveform of the motor by correcting the current waveform of the motor based on the value of the waveform signal obtained by substituting the numerical value based on the rotation speed of the motor into the function of the equation of the waveform signal that does not cause the torque of the motor to pulsate. The present invention has excellent effects such as suppression of torque pulsation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a motor drive circuit according to the present invention.

FIG. 2 is an explanatory diagram of waveform data stored in a waveform data storage unit.

FIG. 3 is a flowchart showing the content of conversion into a three-phase waveform signal based on the read waveform data.

FIG. 4 is a waveform chart of torque and torque amplitude of the motor.

FIG. 5 is a characteristic diagram showing the relationship between the amplitude ratio of the fundamental wave and the third harmonic and the torque ripple.

FIG. 6 is a block diagram showing a configuration of a conventional motor drive circuit.

FIG. 7 is a waveform diagram of torque amplitude and torque ripple.

[Explanation of symbols]

2 Deviation counter 3 _U U-phase amplifier 3 _V V-phase amplifier 3 _W W-phase amplifier 5 3-phase motor 7 Position counter 8 Waveform data storage 9 Phase waveform converter

Claims (3)

[Claims] 1. In a motor drive circuit for supplying an alternating current to a motor to drive the motor, a phase is determined based on a data storage unit storing non-sinusoidal waveform data and waveform data read from the data storage unit. And a phase waveform converter that converts and outputs AC current waveform signals of a plurality of different phases,
A motor drive circuit configured to drive a motor based on an output signal of the phase waveform converter. 2. The motor drive circuit according to claim 1, wherein a rewritable memory is used as the data storage unit. 3. In a motor drive circuit for supplying an alternating current to a motor to drive the motor, a formula storage unit storing a formula for obtaining a value of a waveform signal that does not cause the torque of the motor to pulsate, and a rotation speed of the motor. A numerical value output section for outputting a numerical value based on the formula to be substituted into the function of the formula, and a phase waveform for converting into a waveform signal of alternating current of a plurality of phases different in phase based on the value of the waveform signal obtained by calculating the formula. A motor drive circuit comprising a converter, and configured to drive a motor based on an output signal of the phase waveform converter.