JP5440383B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device.

  Conventionally, a motor has been used as a power source for fuel cell vehicles and so-called hybrid vehicles. It is known that noise called electromagnetic noise (or magnetic noise) is generated from this motor.

  An alternating current is supplied to the motor, and along with this, an alternating magnetic field (alternating magnetic field) is generated in the motor. This alternating magnetic field vibrates the motor. Such electromagnetic vibration is called electromagnetic excitation force, and noise resulting from the electromagnetic excitation force is called electromagnetic noise.

The frequency of the alternating magnetic field varies depending on the frequency of the AC voltage applied to the motor. The frequency of electromagnetic noise also changes with the change in frequency of the alternating magnetic field. When the frequency of the electromagnetic noise changes, the volume of the electromagnetic noise also changes. FIG. 9 shows a change in sound pressure level [dB] accompanying a change in frequency of electromagnetic noise. Note that the sound pressure level refers to a physical quantity of sound intensity, and a change in pressure (sound pressure) of a medium (such as the atmosphere) when sound waves pass is defined as a reference sound pressure (for example, 2 × 10 ⁻⁵ Pa). It is a value compared. As shown in Figure 9, motor resonance when the frequency of the electromagnetic noise is equal to the resonant frequency f _m of the motor (resonance) to electromagnetic noise sound pressure level [dB] is locally increased.

Here, comparing the sound pressure level and other cabin noise sound pressure level when the frequency of the electromagnetic noise is resonance frequency f _m. The following will be an electromagnetic noise when the frequency is the resonance frequency f _m is referred to as "electromagnetic noise at resonance." FIG. 10 shows frequency spectra of electromagnetic noise at resonance and other in-vehicle noise. In general, noise other than the noise of interest is called background noise, and therefore, in-vehicle noise other than electromagnetic noise at resonance is collectively expressed as background noise in FIG. As shown in FIG. 10, the sound pressure level of the electromagnetic noise at the time of resonance is more prominent than the sound pressure level of the background noise in the surrounding band. Therefore, electromagnetic noise is noticeable to the driver and passengers of the vehicle. As a result, the driver or the like is worried about the electromagnetic noise and feels uncomfortable.

  Therefore, a technique for reducing the protrusion of the sound pressure level of electromagnetic noise during resonance has been conventionally known. In Patent Document 1, the surface mode resonance vibration of the rotor is suppressed by supplying the motor with an alternating current in which a harmonic component having an odd multiple of the frequency of the command signal for the motor is superimposed on the command signal. . Thereby, the sound pressure level of the electromagnetic noise at the time of resonance is reduced.

  In Patent Document 2, the vibration of the motor is suppressed by supplying an alternating current in which a sine wave having a phase opposite to that of the vibration component is superimposed on the fundamental wave component. Thereby, the sound pressure level of the electromagnetic noise at the time of resonance is reduced.

  In Patent Document 3, when the frequency of the alternating magnetic field that vibrates the motor approaches the resonance frequency of the motor, the frequency of the alternating magnetic field is shifted to a value larger than the resonance frequency, and the frequency of the alternating magnetic field matches the resonance frequency. Is avoiding.

JP 2009-5502 A Japanese Patent Laid-Open No. 2003-189692 JP 2009-284719 A

  By the way, as a process for reducing the protrusion of the sound pressure level of the noise of the specific frequency, in addition to reducing the sound pressure level of the noise of the frequency or avoiding the generation of noise of the frequency, there is an acoustic process called masking. Are known. Masking is a process of adding a so-called masking sound to the peripheral band of noise of a specific frequency. This process reduces the protruding sound pressure level of the noise, and makes it easier to hear the noise of a specific frequency. .

  The present invention provides a method for reducing the sound pressure level of electromagnetic noise by masking instead of the conventional means for reducing the sound pressure level of electromagnetic noise by reducing the sound pressure level of electromagnetic noise or avoiding the generation of electromagnetic noise. An object of the present invention is to provide a means for reducing the protrusion of the.

  The present invention relates to a motor control device. The control device generates a masking sound having a masking frequency that does not coincide with the resonance frequency within a critical band determined by the resonance frequency of the motor.

  In the above invention, the control device outputs a switching signal that is generated based on an inverter circuit including a switching element that controls a current supplied to the motor, a carrier wave, and a command signal for the motor, and controls the switching element. And a noise control unit that adjusts the frequency of the carrier wave so that the frequency of the sideband component that is included in the switching signal and is generated by superimposing the command signal and the carrier wave becomes the masking frequency. It is.

  In the above invention, the noise control unit preferably modulates the frequency of the carrier wave with a predetermined modulation width.

  In the above invention, it is preferable that the noise control unit obtains the frequency of the carrier wave having the resonance frequency of the sideband component and modulates the frequency of the carrier wave with the modulation width in the frequency band including the obtained frequency. is there.

  According to the present invention, the protrusion of the sound pressure level of electromagnetic noise can be reduced by masking.

It is a figure which illustrates the motor control device concerning this embodiment, and its peripheral equipment. It is a figure explaining a fundamental wave component and a sideband component. It is a figure explaining a fundamental wave component and a sideband component. It is a figure explaining the masking of the fundamental wave component by a sideband component. It is a conceptual diagram of the frequency spectrum of the vehicle interior noise when masking is performed. It is a figure explaining the masking of the fundamental wave component by a sideband component. It is a figure explaining the masking of the fundamental wave component by a sideband component. It is a conceptual diagram of the frequency spectrum of the vehicle interior noise when masking is performed. It is a conceptual diagram of the change of the sound pressure level with respect to the frequency change of electromagnetic noise. It is a conceptual diagram of the frequency spectrum of electromagnetic noise and other vehicle interior noise.

  FIG. 1 shows a motor control device and its peripheral devices according to an embodiment of the present invention. The motor control device 10 is connected to the inverter 12. The inverter 12 is connected between the DC power supply 14 and the motor 16. These devices are mounted in a vehicle (not shown).

  The motor control device 10 performs drive control of the motor 16 by PWM (Pulse Width Modulation) control. Further, as will be described later, a masking process for reducing the protrusion of electromagnetic noise generated in the motor 16 is performed. The motor control device 10 includes an arithmetic circuit such as a CPU, storage means such as a semiconductor memory and a hard disk, an input / output device, and the like.

  The motor control device 10 includes a noise control unit 30, a storage unit 32, a carrier wave generation unit 34, and a switching signal generation unit 36. The storage unit 32 stores a resonance frequency of the motor 16, a critical band for masking, and the like. The noise control unit 30 can refer to these pieces of information stored in the storage unit 32. The carrier wave generation unit 34 is provided with an oscillation circuit (not shown), and can generate and output a carrier wave having a triangular wave or sawtooth waveform. As will be described later, the noise control unit 30 sends a command for adjusting the frequency of the carrier wave to the carrier wave generation unit 34. In addition, the switching signal generation unit 36 receives a command signal from an electronic control device (not shown), receives a carrier wave from the carrier wave generation unit 34, and generates a switching signal by comparing the two. The switching signal is generated as a square wave (rectangular wave) that is turned on when the value of the command signal is higher than the carrier wave and turned off when the value is lower. The command signal (also referred to as a modulated wave) is a drive command for the motor 16 and has an AC voltage waveform (sine wave) to be applied to the motor 16. The command signal is determined by an electronic control unit (not shown) based on a motor current detected by a current sensor (not shown) and a torque command value based on an accelerator opening degree (not shown). In addition to being transmitted to the switching signal generator 36, the command signal is also transmitted to the noise controller 30.

  The switching signal is transmitted from the switching signal generator 36 to the inverter 12. Inverter 12 includes a U-phase arm 20, a V-phase arm 22, and a W-phase arm 24. U-phase arm 20, V-phase arm 22, and W-phase arm 24 are connected in parallel between output lines of DC power supply 14.

  U-phase arm 20 includes IGBT elements Q1 and Q2 connected in series, and diodes D1 and D2 connected in parallel with IGBT elements Q1 and Q2, respectively. The cathode of diode D1 is connected to the collector of IGBT element Q1, and the anode of diode D1 is connected to the emitter of IGBT element Q1. The cathode of diode D2 is connected to the collector of IGBT element Q2, and the anode of diode D2 is connected to the emitter of IGBT element Q2.

  V-phase arm 22 includes IGBT elements Q3 and Q4 connected in series, and diodes D3 and D4 connected in parallel with IGBT elements Q3 and Q4, respectively. The cathode of diode D3 is connected to the collector of IGBT element Q3, and the anode of diode D3 is connected to the emitter of IGBT element Q3. The cathode of diode D4 is connected to the collector of IGBT element Q4, and the anode of diode D4 is connected to the emitter of IGBT element Q4.

  W-phase arm 24 includes IGBT elements Q5 and Q6 connected in series, and diodes D5 and D6 connected in parallel with IGBT elements Q5 and Q6, respectively. The cathode of diode D5 is connected to the collector of IGBT element Q5, and the anode of diode D5 is connected to the emitter of IGBT element Q5. The cathode of diode D6 is connected to the collector of IGBT element Q6, and the anode of diode D6 is connected to the emitter of IGBT element Q6.

  Further, the intermediate point of each U, V, W phase arm is connected to each phase end of each phase coil of the motor 16 via a U, V, W phase power cable. That is, the motor 16 is a three-phase AC motor, and one end of each of the three coils of the U, V, and W phases is connected to the neutral point. The other end of the U-phase coil is connected to a connection node of IGBT elements Q1 and Q2 via a U-phase power cable. The other end of the V-phase coil is connected to a connection node of IGBT elements Q3 and Q4 via a V-phase power cable. The other end of the W-phase coil is connected to a connection node of IGBT elements Q5 and Q6 via a W-phase power cable.

  The inverter 12 functions as a power converter that converts DC power from the DC power source 14 into AC power. The inverter 12 converts a DC voltage from the DC power source 14 into an AC voltage and outputs it to a motor 16 that drives wheels of, for example, a hybrid vehicle or an electric vehicle. The motor 16 generates driving torque for the vehicle or the like by the three-phase AC voltage received from the inverter 12. The motor 16 generates a three-phase AC voltage and outputs it to the inverter 12 during regenerative braking of the vehicle or the like. The inverter 12 converts the AC voltage generated by the motor 16 into a DC voltage and charges the DC power supply 14. May be. That is, inverter 12 is provided as a power converter that performs power conversion between DC power supplied from DC power supply 14, AC power for driving and controlling the motor, and AC power generated by the generator. The inverter 12 may return the electric power generated by the motor 16 to the boost converter or the like with regenerative braking. At this time, the boost converter is controlled by a control device or the like so as to operate as a step-down circuit.

  A switching signal is sent to the inverter 12 from the switching signal generation unit 36 of the motor control device 10, and switching elements such as the IGBT elements Q1 to Q6 of the inverter 12 are turned on / off based on the switching signal. When the switching element is turned on / off, the DC voltage supplied from the DC power supply 14 is chopped (chopped) and converted into a square wave AC voltage having a different pulse width. This square wave is also called a PWM wave. When the output voltage of the PWM wave is averaged, it becomes a sine wave proportional to the command signal. As will be described later, the PWM wave includes a fundamental wave component having the same frequency as the command signal and a sideband wave in which the fundamental wave component and the carrier wave are combined.

  The DC power source 14 is, for example, a battery, and examples thereof include secondary batteries such as nickel metal hydride or lithium ion, and fuel cells. The DC power supply 14 may supply a DC voltage to the inverter 12 and be charged by the DC voltage from the inverter 12.

  A capacitor 18 for smoothing the DC voltage supplied from the DC power supply 14 may be provided between the DC power supply 14 and the inverter 12. Further, a boost converter or the like may be provided between the capacitor 18 and the inverter 12.

  The motor 16 is composed of, for example, a three-phase AC synchronous motor generator. For example, the motor 16 may be incorporated in a hybrid vehicle or the like so as to operate as a generator driven by an engine or the like, or may be incorporated in a hybrid vehicle or the like as an electric motor that drives the drive wheels of the hybrid vehicle. It may be. The motor 16 includes a stator (stator) and a rotor (rotor), and the stator and the rotor electromagnetically interact to rotate the rotor and generate a driving force.

  Next, electromagnetic noise generated from the motor 16 will be described. When an alternating current flows through the motor 16, an alternating magnetic field is generated in the motor 16, and an excitation force (electromagnetic excitation force) caused by the alternating magnetic field is generated. This electromagnetic excitation force is applied to the motor 16 to generate vibration in the motor 16. Noise is generated by the propagation of this vibration to the surrounding air. This noise is called electromagnetic noise.

  The frequency of electromagnetic noise is determined according to the frequency of the AC voltage applied to the motor 16. The AC voltage applied to the motor 16 has the same waveform as the switching signal described above. The switching signal is a rectangular wave, and a fundamental wave component having the same frequency as the command signal that is a sine wave and a harmonic component of the fundamental wave are superimposed. The harmonic component is also called a sideband component, and is generated by combining the command signal and the carrier wave. Electromagnetic noise (and alternating magnetic field and electromagnetic excitation force causing electromagnetic noise) can be divided into a component having a fundamental frequency and a component having a sideband frequency.

  The frequency of the sideband can be expressed by the following formula 1.

Here, f _s is the frequency of the sideband, f _c is the frequency of the carrier wave, f ₀ denotes the frequency of the fundamental wave (and the command signal). N is an integer of 1 or more, and k is an integer determined by n.

The frequency f ₀ of the fundamental wave is proportional to the motor speed, the frequency f ₀ of the fundamental wave with the increase of the motor speed also increases. Accordingly, as shown in FIG. 2, the frequency f _{s of} the sideband wave represented by nf _c −kf ₀ decreases as the motor speed increases, and the sideband wave represented by nf _c + kf _0. The frequency f _s increases as the motor speed increases.

Furthermore, as shown in FIG. 3, if any of the frequency of the electromagnetic noise derived from the electromagnetic noise or sideband component, derived from the fundamental wave component matches the resonant frequency f _m of the motor 16, the motor 16 is resonant (resonant ) Electromagnetic noise increases locally. Since the resonant frequency f _m of the motor 16 is a frequency specified the structure of the motor, it is determined in advance by measurement and stored in the storage unit 32 of the motor controller 10.

Next, electromagnetic noise masking processing by the motor control device 10 will be described. Masking is the process of making certain sounds difficult to hear due to the presence of other sounds so that conversations under noisy are difficult to hear. By superimposing the masking sound on the peripheral band of the frequency of the sound to be masked (hereinafter referred to as a maskee), the protrusion of the sound pressure level [dB] of the maskee is reduced. As a result, the hearing of the musky is reduced audibly. In other words, this phenomenon can be expressed in terms of loudness [phon] representing the loudness of the auditory sound. When the masking sound is superimposed on the maskee, the physical sound pressure level [dB] of the maskee does not change. This reduces the loudness of Muskie. In the present embodiment, among the electromagnetic noise generated from the motor 16, the resonance frequency component of the motor 16 is a maskee, and a masking sound for the maskee is generated. Specifically cause oscillation frequencies in a predetermined band around the resonance frequency f _m of the motor 16 to the motor 16, by superimposing the noise due to the vibration in the resonance frequency component f _m of the electromagnetic noise, the resonance frequency component f _{m to mute} the sound pressure level.

Here, the band of the frequency (masking frequency) that can be used as the masking sound changes according to the frequency of the maskee. A frequency band that functions effectively as a masking sound for a maskee is called a critical band. Experiments have shown that the masking effect cannot be obtained even if the sound with a frequency exceeding the critical band is superimposed on the maskee. In this embodiment, advance obtained in advance by actual measurement or the like the resonant frequency f _m of the motor 16, previously obtained further critical band corresponding to the resonance frequency f _m also advance. Thus the resonance frequency f _m and the critical band was determined previously stored in the storage unit 32 of the motor controller 10.

Further, in the present embodiment, the electromagnetic noise derived from the fundamental wave component described above is masked by the electromagnetic noise derived from the sideband wave component. As shown in FIG. 4, when the fundamental frequency f ₀ matches the motor resonance frequency f _m (f ₀ = f _m ), the noise control unit 30 performs the sideband frequency as shown in FIG. f _s is the resonant frequency _{f m} masking frequency _{f s} in the critical band of _{'(f m -1 / 2Δf ≦} f s' ≦ f m + 1 / 2Δf, however _{f s'} ≠ _{f m)} and so as to frequency of the carrier It sends a command to adjust the f _c the carrier wave generating unit 34.

A carrier wave f _c ′ for setting the sideband frequency to f _s ′ is obtained based on Equation 2 below. As masking sound of the fundamental wave in Fig. 4, it is used sideband represented by _{n × f c -k × f 0} .

In FIG. 4, when the frequency f ₀ of the fundamental wave becomes equal to the resonance frequency f _m , the frequency of the sideband whose carrier frequency is set to f _c ′ becomes the frequency f _s ′ within the masking critical band. While electromagnetic noise derived from the fundamental wave to resonate motor 16, by electromagnetic noise from sidebands overlap the electromagnetic noise of the resonance frequency f _m acts as a masking sound, the resonant frequency as shown in FIG. 5 f _m The projection of the sound pressure level of electromagnetic noise is reduced. By projecting the sound pressure level is reduced, the auditory so electromagnetic noise of the resonance frequency f _m is felt less.

Furthermore, the fundamental wave can also mask the sideband wave depending on the slope (FIG. 4) indicating the frequency change of the fundamental wave and the sideband wave. That is, as shown in FIG. 4, the frequency f _s of the sideband wave becomes the resonance frequency f _m of the motor 16 after the fundamental frequency f ₀ exceeds the resonance frequency f _m of the motor 16 by increasing the motor rotation speed. If the fundamental wave frequency f ₀ is present in the critical band when it reaches, the noise derived from the fundamental wave functions as a masking sound for the noise derived from the sideband wave.

Note that unlike the slope indicating the frequency change of the fundamental and sidebands and 4, when the frequency of the sideband reaches the resonant frequency f _m, the frequency of the fundamental wave is sometimes missing from the critical zone. Then, the noise due to the fundamental wave cannot mask the noise due to the sideband. On the other hand, if the frequency of the fundamental wave is changed so that the fundamental wave component can mask the sideband component, the frequency of the fundamental wave is different from the frequency of the command signal, and the torque of the motor 16 according to the command can be obtained. become unable. Therefore, in such a case, the frequency of the fundamental wave is not changed, and the noise caused by the sideband wave is masked by the sideband wave itself. Specifically, the noise control unit 30 for the carrier generating unit 34, and sends a command to the modulation frequency f _c of the carrier wave with a predetermined bandwidth. Thus, as shown in FIG. 6, even when the frequency of the sideband is equal to the resonant frequency f _m, the frequency of the sideband wave with a bandwidth of around resonant frequency f _m at its front and rear is modulated , by the electromagnetic noise of the peripheral band, the protrusion of the sound pressure level of electromagnetic noise is reduced in the resonant frequency f _m. Since the masking effect cannot be obtained beyond the critical band, it is desirable that the modulation width of the frequency of the carrier wave (and sideband) be within the critical band.

  It is also known that the masking sound has a higher masking effect when it has a bandwidth than a single frequency (single sound). Therefore, by using a sideband wave that is frequency-modulated with a predetermined bandwidth as a masking sound of electromagnetic noise derived from the fundamental wave, a higher masking effect can be obtained as compared with the case where modulation is not performed (FIG. 4).

Further, as shown in FIG. 7, when the noise control unit 30 sets the resonance frequency f _m to the carrier wave generation unit 34, the frequency f _s of the sideband is changed to the resonance frequency f _m when the fundamental frequency f ₀ becomes the resonance frequency f _m . A command for modulation as the center frequency may be sent. Thus, as shown in FIG. 8, when the frequency f ₀ of the electromagnetic noise due to the fundamental wave is equal to the resonant frequency f _m, functional electromagnetic noise due sideband modulated around the band around the resonance frequency as a masking sound In addition, a high masking effect can be obtained.

  In the motor control device 10 described above, instead of generating the masking sound by the sideband component, a sound output means such as a speaker is provided around the motor 16 so that the masking sound including the frequency component within the critical band with respect to the resonance frequency is provided. May be generated by the audio output means.

  DESCRIPTION OF SYMBOLS 10 Motor control apparatus, 12 Inverter, 14 DC power supply, 16 Motor, 18 Capacitor, 30 Noise control part, 32 Storage part, 34 Carrier wave generation part, 36 Switching signal generation part

Claims (1)

A motor control device,
An inverter circuit including a switching element for controlling a current supplied to the motor;
A switching signal generator that is generated based on a carrier wave and a command signal for the motor and outputs a switching signal for controlling the switching element;
The frequency of the carrier wave that is included in the switching signal and is generated by superimposing the command signal and the carrier wave so that the frequency of the sideband component matches the resonance frequency of the motor is obtained. A noise control unit that modulates the frequency of the carrier wave with a predetermined modulation width in a frequency band including:
With
A control device that generates a masking sound having a masking frequency that is within a critical band determined by a resonance frequency of the motor and does not coincide with the resonance frequency.

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