JP5338110B2 - Motor drive device and control method thereof - Google Patents

Description

  The present invention relates to a motor drive device that PWM detects a current flowing through a motor and a rotational position (electrical angle) of the motor, and a control method thereof.

  As a device to detect the phase current flowing in the motor, the negative shunt resistor is inserted between the switch element that constitutes each negative arm of the inverter and the reference potential for the current flowing in each phase of the motor. A technique for detecting a current flowing through each phase due to a voltage drop of a resistor is known (for example, Patent Document 1).

  A resolver is used as a motor electrical angle detection device that detects the rotational position (electrical angle) of the motor. As a conversion means for obtaining the rotational position from the output signal of the resolver, an R / D converter-less configuration that does not use an R / D converter that performs conversion to a digital signal is used (for example, Patent Document 2).

  A method for detecting the motor electrical angle without an R / D converter will be briefly described. When a sinusoidal signal is applied to an excitation coil provided on a resolver rotor (rotor), a signal is induced in two detection coils (cosine coil, sine coil) formed on a stator (stator). Here, the signal induced in the detection coil is a signal in which the sine wave signal applied to the excitation signal is amplitude-modulated with a cosine wave and a sine wave, respectively, as the rotor rotates. That is, it can be described as follows.

Excitation coil input sin (ωt) ω is the angular velocity of the sine wave, t is the time detection coil output cosine coil sin (ωt) x Acosθ
The sine coil sin (ωt) × Asinθ θ is the motor electrical angle, A is the constant cosine coil output and the sine coil output, and the motor electrical angle θ is obtained by the following equation.

θ = tan-1 {(sin (ωt) × Asinθ) / (sin (ωt) × Acosθ)}
= Tan-1 (sinθ / cosθ)
However, the actual output of the detection coil includes a sine wave component of the excitation signal. Therefore, in order to detect the motor electrical angle, it is necessary to detect the amplitude of the envelope waveform of each output signal, and for this purpose, it is necessary to detect the output signal at the timing of the peak of each output signal.

Furthermore, when the motor is driven by PWM, a technique for changing the carrier frequency of PWM is known in order to reduce electromagnetic radiation noise (EMI) due to opening and closing of switch elements constituting the drive circuit (for example, Patent Document 3).
JP-A-6-351280 JP 2005-210839 A JP-A-7-99795

  In the case of the motor driving apparatus described in the prior art, that is, the configuration in which the motor current detection is performed using the negative shunt resistor and the motor electrical angle detection is performed without using the R / D converter using the resolver, EMI In order to suppress this, consider changing the PWM carrier frequency with time.

  In the motor current detection method using the negative shunt resistor, it is necessary to detect the current at the timing when the current flows through the negative arm of the switching circuit (for example, the timing of the valley of the carrier triangular wave (may be a peak)). is there. The fact that the carrier frequency changes with time means that the timing of the troughs of the carrier triangular wave does not become constant, but changes.

  On the other hand, the motor electrical angle must be detected at the timing of the peak of the sine wave that excites the exciting coil of the resolver. Since this sine wave signal has a constant period, the timing of the motor electrical angle detection is constant. .

  Therefore, when the carrier frequency is changed with time, it is impossible to always detect the motor current and the motor electrical angle at the same time.

In order to solve the above problems, the present invention provides a switching circuit for supplying a motor current PWM-modulated to a motor, a motor current detecting means for detecting a motor current using a negative shunt resistor provided in the switching circuit , Motor electrical angle detecting means for detecting the electrical angle of the motor using a resolver, excitation signal generating means for generating an excitation signal for exciting the resolver, and carrier frequency changing means for changing the carrier frequency of PWM modulation the motor drive device, excited磁信No. generating means, in accordance with the change of the carrier frequency, the timing at which the motor current is detected by the motor current detecting means, so as to match the timing of the peak of the excitation signal, the excitation signal phase The gist is to adjust.

  According to the present invention configured as described above, the phase of the excitation signal of the resolver can be adjusted in accordance with the timing of detecting the motor electrical angle, so that the detection timing of the motor current is limited and the detection of the motor electrical angle is performed. In the configuration in which the resolver is used to perform the R / D converter-less technique, there is an effect that the motor current detection and the motor electrical angle detection can be performed simultaneously when the carrier frequency is changed with time.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of a control device for a motor drive device according to the present invention. In this embodiment, the motor 2 driven by the motor driving device 1 will be described by taking a permanent magnet type three-phase synchronous motor as an example, but the driven motor is not limited to a permanent magnet type three-phase synchronous motor. Absent.

  In FIG. 1, a motor drive device 1 includes a microcomputer 3 that is a control device for the motor drive device, an inverter 4 that supplies three-phase power to the motor 2, and a resolver 5 that detects the rotational position (electrical angle) of the motor 2. And a low-pass filter (LPF) 6 that is a sine wave generation unit that generates a sine wave from a rectangular wave.

  The inverter 4 includes a negative shunt resistor for current detection between each negative switch element (also referred to as a negative arm) of the three-phase bridge circuit and a reference potential. The voltages of these negative shunt resistors are input to a motor current detection circuit 11 of the microcomputer 3 described later. As described above, in this embodiment, the motor current is detected using the negative shunt resistor, so that the current of each phase of the three-phase motor is directly measured using the current sensor that detects the current by the Hall effect. Compared to the case of detection, it can be realized at a low cost.

  The resolver 5 includes an excitation coil 20 and a detection coil 21. The excitation coil 20 is excited by a sinusoidal excitation signal provided from the low-pass filter 6. The exciting coil 20 is fixed to the rotor or the rotating shaft of the motor 2 and rotates integrally with the rotating shaft. The detection coil 21 includes a sine coil and a cosine coil (not shown), receives the magnetic field from the excitation coil 20, and outputs a sine signal and a cosine signal.

  The microcomputer 3 includes a gate signal generation unit 7 that supplies a drive signal to each switching element constituting the inverter 4, a resolver output signal detection unit 13 that detects a peak of a signal output from the detection coil 21 of the resolver 5, and a resolver A motor electrical angle calculation unit 14 that calculates a motor electrical angle based on the output of the output signal detection unit 13, a rectangular wave phase adjustment unit 15 that adjusts the rising and falling timings of the rectangular wave, and a source of a resolver excitation signal And a rectangular wave generator 16 for generating a rectangular wave.

  The gate signal generation unit 7 includes a carrier frequency change unit 8 that changes the carrier frequency of PWM modulation with time, a carrier waveform generation unit 9 that generates a carrier waveform at a frequency indicated by the carrier frequency change unit 8, and a carrier waveform. PWM comparison unit 10 that compares the command value to generate the gate signal of the inverter, motor current detection unit 11 that detects the motor current based on the negative shunt resistance voltage output from inverter 4, motor current and motor And a command value generation unit 12 that generates a command value based on the electrical angle.

  The gate signal generation unit 7 causes the carrier waveform generation unit 9 to generate a carrier triangular wave having a carrier frequency determined by the carrier frequency change unit 8. Further, the motor current is detected by the motor current detection unit 11 from the negative shunt resistance voltage output from the inverter 4. The command value generation unit 12 generates a command value by computing the motor current detection value and the motor electrical angle detection value. The command value and the carrier triangular wave are compared by the PWM comparator 10, and an on / off signal is applied to the gates of the six switch elements of the inverter 4 due to the magnitude relationship.

  On the other hand, the microcomputer 3 includes a resolver output signal detection unit 13, a motor electrical angle calculation unit 14, a rectangular wave phase adjustment unit 15, and a rectangular wave generation unit 16 as a configuration for detecting the motor electrical angle. Yes. The rectangular wave generator 16 generates a rectangular wave that is a source of the excitation signal of the resolver 5. By passing this signal through the low-pass filter 6, a sine wave signal is generated. This signal is applied as an excitation signal to the excitation coil 20 of the resolver 5. The output signal (cosine signal, sine signal) of the detection coil 21 of the resolver 5 is sampled by the resolver output signal detector 13 at the peak timing of the excitation signal.

  The sampling timing is instructed from the carrier waveform generation unit 9. At the same time, the carrier waveform generation unit 9 also instructs the motor current detection unit 11 to sample the voltage drop value at the negative shunt resistor. The motor current detection unit 11 includes, for example, a known sample and hold circuit and an A / D conversion circuit, and calculates a digital value of the motor current from the voltage of the negative shunt resistor.

  The motor electrical angle calculator 14 calculates the motor electrical angle from the sampling value obtained by the resolver output signal detector 13. The value of the motor electrical angle, which is the calculation result, is input to the command value generation unit 12 and used for calculation of the command value.

  Next, the rectangular wave phase adjustment unit 15 will be described. Now, the PWM carrier frequency is changed with time. At this time, in order to simultaneously detect the motor current and the motor electrical angle, it is necessary to make the timing of the valley of the carrier triangular wave coincide with the peak timing of the excitation signal. The rectangular wave phase adjustment unit 15 adjusts the rising and falling timings of the rectangular wave that is the source of the excitation signal so that the peak timing of the excitation signal matches the timing of the valley of the carrier triangular wave.

  In the present embodiment, the provision of the rectangular wave phase adjustment unit has an effect that the motor current detection and the motor electrical angle detection can be performed simultaneously even when the carrier frequency is changed with time.

  FIG. 2 is an example of a time change of (a) a carrier triangular wave, (b) a detection timing, (c) an excitation signal, and (d) a rectangular wave that is a source of the excitation signal. When the period of the carrier triangular wave changes, both the motor current detection timing and the motor electrical angle detection timing are not constant. In this example, the motor current and the motor electrical angle are detected every two carrier cycles.

  The detection timing is the valley timing of the carrier triangular wave, and the detection timing coincides with the peak timing of the excitation signal. This is because the rising and falling timings of the rectangular wave that is the source of the excitation signal are adjusted according to the change in the carrier period so as to match.

  In FIG. 2, each time indicated by Δt1d, Δt1u, Δt2d, Δt2u, Δt3d, and Δt3u is a time lag (adjustment time) between the rising and falling timings of the rectangular wave and the timing of the valley of the carrier triangular wave. . By determining this time corresponding to the change in the carrier frequency, the peak of the excitation signal can be made simultaneously with the valley of the carrier triangular wave. Note that these adjustment times are not in a one-to-one relationship with the carrier period, but are determined by the change in the carrier period before and after a certain carrier period.

  For example, if the carrier period changes from Tc1 → Tc1 → Tc2 → Tc2 → Tc3 → Tc3 (repetition) and Tc2 → Tc2 → Tc1 → Tc1 → Tc3 → Tc3 (repetition), the same carrier period Tc1 The adjustment times Δt1d and t1u are different. Therefore, in the present embodiment, this relationship, that is, the correspondence relationship between the time change of the carrier cycle and the adjustment time of the rising and falling of the rectangular wave is stored in advance in the control map built in the microcomputer 3.

  This control map is configured as part of the carrier frequency changing unit 8, for example. Thereby, when the method of changing the carrier frequency with time is arbitrarily determined, the control map can be read from the carrier frequency changing unit 8 and the adjustment time can be instructed to the rectangular wave phase adjusting unit 15. Thereby, there is an effect that the phase of the rectangular wave corresponding to the change of the carrier frequency can be easily set.

  Now, when the carrier frequency is changed with time as described above, and the rise and fall timing of the rectangular wave that is the source of the excitation signal is adjusted accordingly, the output of the low-pass filter 6 when the rectangular wave is input is Some excitation signals do not have a constant amplitude. Due to the change in the amplitude of the excitation signal for exciting the excitation coil 20, the amplitude of the sine signal and the cosine signal output from the detection coil 21 changes, and as a result, there is a concern that the accuracy of the motor electrical angle detection is deteriorated.

  FIG. 3 is a diagram illustrating a configuration including an amplitude correction unit 23 for supplying a sinusoidal excitation signal having a constant amplitude to the excitation coil 20 of the resolver 5.

  In FIG. 3, the rectangular wave generator 16 outputs a rectangular wave in which rising and falling timings are adjusted in accordance with changes in the carrier cycle. The low pass filter 6 generates a sine wave signal by allowing only the low frequency component of the rectangular wave to pass therethrough. Since the amplitude of this sinusoidal signal changes, this signal is input to the amplitude correction unit 23 to keep the amplitude constant. A sinusoidal signal having a constant amplitude is input to the excitation coil 20 of the resolver 5 as an excitation signal.

  With such a configuration, it is possible to prevent a decrease in accuracy when the motor electrical angle θ is obtained from the output waveform of the resolver.

  FIG. 4 is a block circuit diagram showing a configuration example in which the amplitude correction unit 23 is inserted between the low-pass filter 6 and the excitation coil 20 to make the amplitude of the sinusoidal excitation signal supplied to the excitation coil constant. The amplitude correction unit 23 is an application of auto gain control (AGC; automatic gain control) used in a radio receiver or the like.

  In FIG. 4, the amplitude correction unit 23 controls the gain of the amplifier 31 by the output of the amplifier 31 that is a variable gain amplification means, the detector 32 that detects the sinusoidal signal amplified by the amplifier 31, and the output of the detector 32. AGC circuit 33 is provided.

  The sine wave signal output from the low-pass filter 6 is input to the amplifier 31. The amplifier 31 amplifies the output of the low-pass filter 6 and outputs it to the excitation coil 20 and the detector 32. The detector 32 detects (rectifies) the output of the amplifier 31 and outputs a DC level. The AGC circuit 33 performs operations such as amplification, attenuation, and level shift so that the output of the detector 32 is suitable for the gain control of the amplifier 31, generates a gain control signal for the amplifier 31, and supplies this to the amplifier 31. To do. The amplifier 31 changes the gain (amplification degree) by this gain control signal.

  The change direction of the gain is such that when the DC level of the output of the detector 32 increases, the gain of the amplifier 31 decreases, and conversely, the DC level of the output of the detector 32 decreases. Are changed in the direction in which the gain of the amplifier 31 increases. As a result, the output amplitude of the sinusoidal signal from the amplifier 31 is constant.

  As described above, by providing the excitation signal amplitude correction unit, the value of Asinθ / Acosθ is obtained when the electrical angle θ is obtained from the output of the resolver, that is, in the relationship θ = tan-1 (Asinθ / Acosθ). Is close to 0, that is, even when θ is close to 0, it is possible to suppress a decrease in the detection accuracy of θ.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above configuration. For example, the detection of motor current is not always possible with the negative shunt resistance of each phase, but current detection is not always possible, such as a magnetic sensor that detects the magnetic field around the conductor of the negative arm, and at a limited timing. It is clear that all possible configurations are included.

1 is a system configuration diagram showing the configuration of an embodiment of a motor drive device according to the present invention. 4 is a timing chart showing (a) a carrier triangular wave, (b) a detection timing, (c) an excitation signal, and (d) a rectangular wave that is a source of the excitation signal in an embodiment of the present invention. It is a block diagram of the amplitude correction of the excitation signal in the Example of this invention. It is a block diagram which shows the structural example of the amplitude correction | amendment part of the excitation signal in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor drive device 2 Motor 3 Microcomputer (control device)
4 Inverter 5 Resolver 6 LPF (Sine wave generator)
7 Gate signal generation unit 8 Carrier frequency change unit 10 PWM comparison unit 11 Motor current detection unit 12 Command value generation unit 13 Resolver output signal detection unit 14 Motor electrical angle calculation unit 15 Rectangular wave phase adjustment unit 16 Rectangular wave generation unit 20 Excitation coil 21 Detection coil 23 Amplitude correction unit

Claims (6)

A switching circuit for supplying a motor current modulated by PWM to the motor;
Motor current detection means for detecting motor current using a negative shunt resistor provided in the switching circuit ;
Motor electrical angle detection means for detecting the electrical angle of the motor using a resolver;
Excitation signal generating means for generating an excitation signal for exciting the resolver;
The motor drive device having a carrier frequency changing means for changing the carrier frequency of the PWM modulation,
Before SL excitation signal generating means, in accordance with the change of the carrier frequency, the timing of the motor current by the motor current detecting means is detected, so as to match the timing of the peak of the excitation signal, the excitation signal phase Adjusting the motor. The excitation signal generating means includes a rectangular wave generating means for generating a rectangular wave and a sine wave generating means for generating a sine wave from the rectangular wave,
The rectangular wave generating means has a rectangular wave phase adjusting means for adjusting rising timing and falling timing of the rectangular wave,
The rectangular wave phase adjusting means adjusts the phase of the rectangular wave so that the timing of the peak of the sine wave coincides with the timing at which the motor current is detected by the motor current detecting means. The motor drive device according to 1.   3. The motor driving apparatus according to claim 1, wherein the motor current detecting unit samples and detects a voltage at a negative shunt resistor provided in the switching circuit at a current detection timing. 4.   3. The motor driving apparatus according to claim 1, wherein the carrier frequency changing unit includes a control map that defines rising and falling timings of the rectangular wave corresponding to a carrier frequency or a carrier period. . The sine wave generation means amplifies the sine wave generated from the rectangular wave and supplies it to the excitation coil, and a gain of the gain variable amplification means using a signal obtained by detecting the output of the variable gain amplification means Automatic gain control means for controlling
The motor driving apparatus according to claim 1, wherein the motor driving apparatus corrects the amplitude of the sine wave supplied to the exciting coil to be constant. A switching circuit for supplying the motor current in PWM modulated motor, said and makes the chromophore at the distal end over motor current detecting means to detect the motor current by using a negative shunt resistor provided in the switching circuit, electric of the motor by using the resolver Control of a motor drive device having motor electrical angle detection means for detecting an angle, excitation signal generation means for generating an excitation signal for exciting the resolver, and carrier frequency changing means for changing the carrier frequency of the PWM modulation In the method
Rectangular wave phase adjustment that adjusts the phase of the rectangular wave that is the source of the sine wave so that the timing of the peak of the sine wave that excites the resolver coincides with the timing at which the motor current is detected by the motor current detection means Process,
A rectangular wave generating process for generating the phase-adjusted rectangular wave;
A sine wave generation process of generating a sine wave from the rectangular wave and supplying the sine wave to the resolver;
A resolver output signal detection process for detecting a peak from the output signal of the resolver;
A method for controlling a motor driving device.

Images