JP7444075B2 - Drive control device, motor drive device and power steering device - Google Patents

Description

The present invention relates to a drive control device, a motor drive device, and a power steering device.

Conventionally, wireless motors are known that have n-phase windings (coils) and have no wires between the coils. Furthermore, as a method for driving such a wireless motor, a drive system called a full bridge in which an inverter is connected to both ends of a coil of each phase is known. When driving a wireless motor using a full bridge, it is normally driven by two inverters, and in the event of an abnormality, one inverter can be switched to the neutral point to perform three-phase control. From the viewpoint of reducing the failure rate, a structure is known in which two inverters are controlled by two control circuits. For example, in Patent Document 1, a first control section controls driving of a first inverter, and a second control section controls driving of a second inverter.

Japanese Patent Application Publication No. 2016-073097

From the viewpoint of reducing the failure rate, it is preferable to use independent drive in which there are no shared circuit parts between the control circuits. However, in the case of a full-bridge drive system, if the frequencies of the PMW carrier signals in each control circuit are out of synchronization, the torque ripple of the motor worsens, causing problems such as noise and vibration. Therefore, one of the objects of the present invention is to reduce the problems caused by torque ripple while ensuring the independence of each control circuit.

One aspect of the drive control device according to the present invention is a drive control device that controls the drive of a motor, and includes a first inverter connected to one end of the winding of the motor, and a first inverter connected to the other end of the winding of the motor. a second inverter; a first control circuit that performs PWM control on the first inverter; and a second control circuit that performs PWM control on the second inverter; In the two control circuits, the frequency of the PWM control carrier signal has a frequency difference that is greater than or equal to the product of the maximum rotation speed of the motor and the number of pole pairs. Moreover, one aspect of the motor drive device according to the present invention includes the drive control device described above and a motor whose drive is controlled by the drive control device.

Moreover, one aspect of the power steering device according to the present invention includes the drive control device, a motor whose drive is controlled by the drive control device, and a power steering mechanism driven by the motor.

According to the present invention, the independence of each control circuit is ensured, and problems caused by torque ripple can be reduced.

FIG. 1 is a diagram schematically showing a typical block configuration of a motor drive unit according to this embodiment. FIG. 2 is a diagram schematically showing a typical circuit configuration of the motor drive unit according to this embodiment. FIG. 3 is a diagram showing the current values flowing through each coil of each phase of the motor. FIG. 4 is a diagram schematically showing a state of voltage application in a switching operation under PWM control. FIG. 5 is a diagram schematically showing a state in which application is stopped in a switching operation under PWM control. FIG. 6 is a diagram showing a PWM signal. FIG. 7 is a graph showing the results of the first to fourth tests. FIG. 8 is a graph showing the results of the fifth to eleventh tests. FIG. 9 is a diagram showing a circuit configuration of a motor drive unit in a modified example with different circuit wiring. FIG. 10 is a diagram schematically showing the configuration of the electric power steering device according to this embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a drive control device, a drive device, and a power steering device of the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid the following explanation from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art, more detailed explanation than necessary may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially the same configurations may be omitted.

In this specification, a drive control device that supplies power from a power source to a three-phase motor having three-phase (U-phase, V-phase, W-phase) windings (sometimes referred to as "coils") is referred to as By way of example, embodiments of the present disclosure will be described. However, the scope of the present disclosure also includes a drive control device that supplies power from a power source to an n-phase motor having n-phase (n is an integer of 4 or more) windings, such as four-phase or five-phase windings.

(Structure of motor drive unit 1000)

FIG. 1 is a diagram schematically showing a block configuration of a motor drive unit 1000 according to this embodiment. Motor drive unit 1000 includes inverters 101 and 102, motor 200, and control circuits 301 and 302.

In this specification, a motor drive unit 1000 including a motor 200 as a component will be described. A motor drive unit 1000 including a motor 200 corresponds to an example of a drive device of the present invention. However, the motor drive unit 1000 may be a device for driving the motor 200 without the motor 200 as a component. The motor drive unit 1000 without the motor 200 corresponds to an example of the drive control device of the present invention.

Motor drive unit 1000 uses two inverters 101 and 102 to convert power from a power source (403 and 404 in FIG. 2) into power that is supplied to motor 200. The inverters 101 and 102 can convert, for example, DC power into three-phase AC power that is a pseudo sine wave of U-phase, V-phase, and W-phase. The two inverters 101 and 102 include current sensors 401 and 402, respectively.

Motor 200 is, for example, a three-phase AC motor. Motor 200 has U-phase, V-phase, and W-phase coils. The winding method of the coil is, for example, concentrated winding or distributed winding.

The first inverter 101 is connected to one end 210 of the coil of the motor 200 and applies a driving voltage to the one end 210, and the second inverter 102 is connected to the other end 220 of the coil of the motor 200 and applies a driving voltage to the other end 220. Apply driving voltage. In this specification, "connection" between parts (components) means electrical connection unless otherwise specified.

The control circuits 301, 302 include microcontrollers 341, 342, etc., as will be detailed later. Control circuits 301 and 302 control drive voltages of inverters 101 and 102 based on input signals from current sensors 401 and 402 and angle sensors 321 and 322. As a control method for the inverters 101 and 102 by the control circuits 301 and 302, for example, a control method selected from vector control and direct torque control (DTC) is used. A specific circuit configuration of motor drive unit 1000 will be described with reference to FIG. 2. FIG. 2 is a diagram schematically showing the circuit configuration of the motor drive unit 1000 according to this embodiment.

Motor drive unit 1000 is connected to independent first power source 403 and second power source 404, respectively. Power supplies 403 and 404 generate a predetermined power supply voltage (for example, 12V). As the power supplies 403 and 404, for example, a DC power supply is used. However, the power supplies 403 and 404 may be AC-DC converters or DC-DC converters, or may be batteries (storage batteries). In FIG. 2, a first power source 403 for the first inverter 101 and a second power source 404 for the second inverter 102 are shown as an example, but the motor drive unit 1000 is common to the first inverter 101 and the second inverter 102. may be connected to a single power source. Further, the motor drive unit 1000 may include an internal power source.

The motor drive unit 1000 includes a first system corresponding to one end 210 side of the motor 200 and a second system corresponding to the other end 220 side of the motor 200. The first system includes a first inverter 101 and a first control circuit 301. The second system includes a second inverter 102 and a second control circuit 302. The first system inverter 101 and control circuit 301 are supplied with power from a first power supply 403 . The second system inverter 102 and control circuit 302 are supplied with power from a second power supply 404.

The first inverter 101 includes a bridge circuit having three legs. Each leg of the first inverter 101 includes a high-side switch element connected between the power source and the motor 200 and a low-side switch element connected between the motor 200 and ground. Specifically, the U-phase leg includes a high-side switch element 113H and a low-side switch element 113L. The V-phase leg includes a high-side switch element 114H and a low-side switch element 114L. The W-phase leg includes a high-side switch element 115H and a low-side switch element 115L. As the switch element, for example, a field effect transistor (MOSFET or the like) or an insulated gate bipolar transistor (IGBT or the like) is used. Note that when the switch element is an IGBT, a diode (freewheel) is connected antiparallel to the switch element.

For example, the first inverter 101 uses shunt resistors 113R, 114R, and 115R as current sensors 401 (see FIG. 1) for detecting the current flowing through the windings of each of the U-phase, V-phase, and W-phase. Prepare for each leg. The current sensor 401 includes a current detection circuit (not shown) that detects the current flowing through each shunt resistor. For example, a shunt resistor may be connected between low-side switch elements 113L, 114L, and 115L and ground. The resistance value of the shunt resistor is, for example, about 0.5 mΩ to 1.0 mΩ.

The number of shunt resistors may be other than three. For example, two shunt resistors 113R and 114R for U phase and V phase, two shunt resistors 114R and 115R for V phase and W phase, or two shunt resistors 113R and 115R for U phase and W phase are used. It's okay to be hit. The number of shunt resistors to be used and the arrangement of the shunt resistors are appropriately determined in consideration of product cost, design specifications, and the like.

The second inverter 102 includes a bridge circuit having three legs. Each leg of the second inverter 102 includes a high-side switch element connected between the power source and the motor 200 and a low-side switch element connected between the motor 200 and ground. Specifically, the U-phase leg includes a high-side switch element 116H and a low-side switch element 116L. The V-phase leg includes a high side switch element 117H and a low side switch element 117L. The W-phase leg includes a high-side switch element 118H and a low-side switch element 118L. Similar to the first inverter 101, the second inverter 102 includes, for example, shunt resistors 116R, 117R, and 118R.

Motor drive unit 1000 includes capacitors 105 and 106. The capacitors 105 and 106 are so-called smoothing capacitors, and absorb the circulating current generated by the motor 200 to stabilize the power supply voltage and suppress torque ripple. The capacitors 105 and 106 are, for example, electrolytic capacitors, and the capacity and number of capacitors to be used are appropriately determined based on design specifications and the like.

Referring again to FIG. The control circuits 301 and 302 include, for example, power supply circuits 311 and 312, angle sensors 321 and 322, input circuits 331 and 332, microcontrollers 341 and 342, drive circuits 351 and 352, and ROMs 361 and 362. . Control circuits 301 and 302 are connected to inverters 101 and 102. The first control circuit 301 controls the first inverter 101 and the second control circuit 302 controls the second inverter 102.

The control circuits 301 and 302 can realize closed-loop control by controlling the target rotor position (rotation angle), rotation speed, current, and the like. The rotation speed is obtained, for example, by differentiating the rotation angle (rad) with respect to time, and is expressed by the number of rotations (rpm) at which the rotor rotates per unit time (for example, one minute). The control circuits 301 and 302 can also control the target motor torque. The control circuits 301 and 302 may be provided with a torque sensor for torque control, but torque control is possible even if the torque sensor is omitted. Further, instead of the angle sensors 321 and 322, a sensorless algorithm may be provided. The power supply circuits 311 and 312 generate DC voltages (for example, 3V and 5V) necessary for each block in the control circuits 301 and 302.

The angle sensors 321 and 322 are, for example, resolvers or Hall ICs. The angle sensors 321, 322 are also realized by a combination of a magnetoresistive (MR) sensor having an MR element and a sensor magnet. The angle sensors 321 and 322 detect the rotation angle of the rotor of the motor 200 and output rotation signals representing the detected rotation angle to the microcontrollers 341 and 342. Depending on the motor control method (for example, sensorless control), the angle sensors 321 and 322 may be omitted.

Input circuits 331 and 332 receive motor current values (hereinafter referred to as "actual current values") detected by current sensors 401 and 402. The input circuits 331 and 332 convert the level of the actual current value to the input level of the microcontrollers 341 and 342 as necessary, and output the actual current value to the microcontrollers 341 and 342. Input circuits 331 and 332 are analog-to-digital conversion circuits.

The microcontrollers 341 and 342 receive the rotor rotation signals detected by the angle sensors 321 and 322, and also receive the actual current values output from the input circuits 331 and 332. The microcontrollers 341 and 342 set a target current value according to the actual current value and the rotor rotation signal, generate a PWM signal, and output the generated PWM signal to the drive circuits 351 and 352. For example, the microcontrollers 341 and 342 generate PWM signals for controlling the switching operation (turn-on or turn-off) of each switch element in the inverters 101 and 102.

Each microcontroller 341, 342 is provided with an internal clock 371, 372. Generation of PWM signals in each microcontroller 341, 342 is performed according to clock signals from internal clocks 371, 372. That is, each microcontroller 341, 342 converts the frequency of the clock signal obtained from the oscillator of the internal clock 371, 372 to generate a carrier signal for PWM control.

The fundamental frequency of the PWM signal (that is, the frequency of the carrier signal in PWM control) generated by each microcontroller 341, 342 has a frequency difference of, for example, 1 kHz between the microcontrollers 341, 342. As a result, as will be described in detail later, even if torque ripple occurs due to the frequency difference, it occurs in a sufficiently high frequency range. Therefore, the noise and vibrations associated with the torque ripple are out of the frequency range that humans can sense, and the noise and vibrations that are unpleasant to humans are suppressed.

Drive circuits 351 and 352 are typically gate drivers. The drive circuits 351 and 352 generate a control signal (for example, a gate control signal) that controls the switching operation of each switch element in the first inverter 101 and the second inverter 102 according to the PWM signal, and apply the generated control signal to each switch element. give to The microcontrollers 341 and 342 may have the function of drive circuits 351 and 352. In that case, drive circuits 351 and 352 are omitted.

The ROMs 361 and 362 are, for example, writable memory (for example, PROM), rewritable memory (for example, flash memory), or read-only memory. The ROMs 361 and 362 store control programs including a group of instructions for causing the microcontrollers 341 and 342 to control the inverters 101 and 102. For example, the control program is once expanded into a RAM (not shown) at boot time.

(Operation of motor drive unit 1000)

Hereinafter, a specific example of the operation of the motor drive unit 1000 will be explained, and a specific example of the operation of the inverters 101 and 102 will be mainly explained.

The control circuits 301 and 302 drive the motor 200 by controlling three-phase energization using both the first inverter 101 and the second inverter 102. Specifically, the control circuits 301 and 302 perform three-phase energization control by controlling switching of the switch elements of the first inverter 101 and the switch elements of the second inverter 102. FIG. 3 is a diagram showing current values flowing through each coil of each phase of the motor 200.

FIG. 3 shows a current obtained by plotting the current values flowing through the U-phase, V-phase, and W-phase coils of the motor 200 when the first inverter 101 and the second inverter 102 are controlled according to the three-phase energization control. A waveform (sine wave) is illustrated. The horizontal axis in FIG. 3 indicates the motor electrical angle (deg), and the vertical axis indicates the current value (A). Ipk represents the maximum current value (peak current value) of each phase. Note that the inverters 101 and 102 can also drive the motor 200 using, for example, a rectangular wave in addition to the sine wave illustrated in FIG. 3 .

The current waveform as illustrated in FIG. 3 is generated by applying a voltage having a waveform corresponding to such a current waveform to the motor 200. Such a voltage is generated by switching the switch elements of the first inverter 101 and the second inverter 102 at a high speed of, for example, 20 kHz under PWM control. 4 and 5 are diagrams schematically showing switching operations under PWM control, with FIG. 4 showing a state of voltage application, and FIG. 5 showing a state of stopped application.

4 and 5 show, for example, a U-phase leg among the legs of the inverters 101 and 102. As described above, the U-phase leg includes the high-side switch element 113H and low-side switch element 113L on the first inverter 101 side, and the high-side switch element 116H and low-side switch element 116L on the second inverter 102 side.

The high-side switching element 113H and the low-side switching element 113L on the first inverter 101 side are not turned on at the same time, and when one is turned on, the other is turned off. Similarly, the high-side switch element 116H and the low-side switch element 116L on the second inverter 102 side are not turned on at the same time.

When a voltage is applied to the windings of the motor 200, the high side switch elements 113H and 116H are turned on in one of the two inverters 101 and 102 (the second inverter 102 in the case of FIG. In the case of 4, the low side switch elements 113L and 116L of the first inverter 101) are turned on. As a result, current flows from the one side to the other side as indicated by the arrow in the figure.

When the application is stopped, all switch elements are in the off state. Immediately after the capacitor is turned off, a circulating current from the motor 200 flows through the capacitors (105 and 106 in FIG. 2), but no current flows thereafter. Further, the circulating current does not contribute to the torque of the motor 200.

In the two inverters 101 and 102, the voltage application state shown in FIG. 4 and the voltage application stop state shown in FIG. 5 are repeated at high speed. The repetition of applying and stopping voltage application to the inverters 101 and 102 is performed according to PWM signals generated by the microcontrollers 341 and 342 of the control circuits 301 and 302. FIG. 6 is a diagram showing a PWM signal.

The PWM signal is a binary pulse signal, and a first value indicating voltage application and a second value indicating stopping of voltage application occur alternately. The pulses of the PWM signal are repeated with a period T0, and the period T0 is divided into a duration T1 of the first value and a duration T2 of the second value.

As described above, the PWM signal is a high frequency signal of, for example, 20 kHz, so the period T0 is a short period of, for example, 50 μsec. Therefore, the effective voltage (effective voltage) applied to the motor 200 is a voltage equalized by the period T0, and the ratio (duty) between the period T0 and the duration T1 of the first value is equal to the power supply voltage and the effective voltage. is equal to the ratio of The effective voltage is a voltage that changes over time in response to a changing current value, such as the current waveform shown in FIG. 3, for example. Such a temporal change in the effective voltage is realized by controlling the duty of the PWM signal by the microcontrollers 341 and 342.

Each of the two microcontrollers 341 and 342 generates a carrier signal with a period T0 and generates a PWM signal based on the carrier signal, but as described above, there is a difference in the frequency of the carrier signal between the microcontrollers 341 and 342. . Therefore, the cycles T0 of the microcontrollers 341 and 342 do not match, and the frequencies of the PWM signals become out of synchronization. Such a synchronization difference causes torque ripple in the motor 200. Here, a simulation test of torque ripple caused by a frequency difference between PWM signals will be explained. Table 1 shows test conditions from the first test to the fourth test.

In the first to fourth tests, the frequency of the PWM signal (first system frequency) generated by the microcontroller 341 of the first control circuit 301 to drive the first inverter 101 is fixed at 20 kHz. Then, in order to drive the second inverter 102, the frequency of the PWM signal (second system frequency) generated by the microcontroller 342 of the second control circuit 302 is changed. In the first test, the frequency of the second system is set to 19.95 kHz, and the frequency difference between the first system and the second system is 50 Hz. In the second test, the frequency of the second system is set to 19.995 kHz, and the frequency difference between the first system and the second system is 5 Hz. In the third test, the frequency of the second system is set to 19.9995 kHz, and the frequency difference between the first system and the second system is 0.5 Hz. In the fourth test, the frequency of the second system is set to 19.99995 kHz, and the frequency difference between the first system and the second system is 0.05 Hz. FIG. 7 is a graph showing the results of the first to fourth tests. A three-dimensional graph is shown in FIG. 7, in which the height axis represents torque intensity, the axis toward the left represents frequency, and the axis toward the rear right represents test number. The large peak near 500 Hz in the graph is a peak of a frequency component corresponding to the rotation speed of the motor, and is not a torque ripple.

The graph representing the results of the first test has many peaks in the frequency range of several hundred Hz, and the peak at a position of 100 Hz, which corresponds to twice the frequency difference, is particularly large. It can be seen that under the conditions of the first test, a large torque ripple corresponding to this large peak occurs.

In the second to fourth tests, no large peaks occur in the frequency range of several hundred Hz. Therefore, it can be seen that torque ripple hardly occurs when the frequency difference is about 5 Hz or less. However, in the case of a clock element using a crystal oscillator, for example, a frequency difference of 10 Hz or more easily occurs due to individual differences in the crystal oscillators, and it is difficult to suppress the frequency between the independent microcontrollers 341 and 342 to about 5 Hz or less. . Therefore, we conducted a simulation test in which the frequency difference was widened. Table 2 shows test conditions from the 5th test to the 11th test.

In the fifth test, the frequency of the first system and the frequency of the second system are both set to the fundamental frequency of 20.0 kHz, and the frequency difference between the first system and the second system is 0 Hz. That is, the frequencies of the PWM signals in the first system and the second system are completely synchronized.

In the sixth test, the frequency of the first system is set to 21.0 kHz, which is +1000 Hz with respect to the fundamental frequency, and the frequency of the second system is set to 20.0 kHz, which is the fundamental frequency.

In the seventh test, the frequency of the first system is set to 20.0 kHz, which is the fundamental frequency, and the frequency of the second system is set to 19.0 kHz, which is -1000 Hz with respect to the fundamental frequency.

In the eighth test, the frequency of the first system is set to 20.5 kHz, which is +500 Hz with respect to the fundamental frequency, and the frequency of the second system is set to 20.0 kHz, which is the fundamental frequency.

In the ninth test, the frequency of the first system is set to the fundamental frequency of 20.0 kHz, and the frequency of the second system is set to 19.5 kHz, which is -500 Hz with respect to the fundamental frequency.

In the tenth test, the frequency of the first system is set to 20.1 kHz, which is +100 Hz with respect to the fundamental frequency, and the frequency of the second system is set to 20.0 kHz, which is the fundamental frequency.

In the 11th test, the frequency of the first system is set to the fundamental frequency of 20.0 kHz, and the frequency of the second system is set to 19.9 kHz, which is -100 Hz with respect to the fundamental frequency. FIG. 8 is a graph showing the results of the fifth to eleventh tests. A three-dimensional graph is also shown in FIG. 8, in which the height axis represents the torque intensity, the axis toward the far left represents the frequency, and the axis toward the far right represents the test number. Also in FIG. 8, the large peak near 500 Hz in the graph is a peak of a frequency component corresponding to the rotational speed of the motor, and is not a torque ripple. In the graph representing the results of the fifth test, no particular peak occurs in the frequency range of several hundred Hz. Therefore, it can be seen that torque ripple does not occur if the frequencies are synchronized.

The graphs representing the results of the 10th test and the 11th test have many peaks in the frequency range of several hundred Hz, and the peak at a position of 200 Hz, which corresponds to twice the frequency difference, is particularly large. It can be seen that under the conditions of the 10th test and the 11th test, a large torque ripple corresponding to this large peak occurs.

In the 6th to 9th tests, no large peaks occur in the frequency range of several hundred Hz. In the case of the eighth to ninth tests, twice the frequency difference is 1 kHz, and a somewhat large peak appears at the 1 kHz position in the graph. Then, a torque ripple corresponding to this peak will occur. However, since 1 kHz vibration is outside the range of human senses, problems such as noise associated with torque ripple can be suppressed. In the 6th and 7th tests, twice the frequency difference is 2kHz, and noise is further out of the human sense range.

For example, when used in a power steering device, the rotation speed of the motor 200 changes depending on the situation. As a result of the change in the rotation speed of the motor, if the rotation speed of the motor 200 and the frequency of the torque ripple overlap, there is a possibility that the drive control of the motor will be disturbed.

If the frequency of the PWM-controlled carrier signal between the first system and the second system has a frequency difference that is greater than or equal to the product of the maximum rotation speed of the motor 200 and the number of pole pairs, the frequency difference will be 2n times the frequency difference (n is a natural number). The frequency of the generated torque ripple is outside the rotational speed of the motor 200 and also outside the human sensory range. As a result, problems such as noise, vibration, and control disturbance caused by torque ripple are suppressed.

Further, it is preferable that the frequency difference between the carrier signals for PWM control is a value excluding 3n times the above product (n is a natural number) in mechanical angle. Even if the frequencies of the carrier signals in the first system and the second system are completely synchronized, a 6nth-order torque ripple occurs in the motor 200. If the frequency difference between the carrier signals is 3n times the above product in mechanical angle, it is possible to avoid the torque ripple due to the frequency difference from being superimposed on the 6nth order torque ripple. Two configurations can be considered as specific configurations for obtaining the frequency difference between carrier signals.

The first configuration uses clock elements whose clock signal frequencies differ from each other by, for example, about 5% as the two internal clocks 371 and 372 shown in FIG. By using such a clock element, the same program can be used as a drive control program (particularly a carrier signal generation and PWM control program) in the two microcontrollers 341 and 342.

The second configuration uses a microcontroller 341, 3 with two frequency conversion coefficients.
42, which differ from each other by, for example, about 5%. These conversion coefficients are used when the two microcontrollers 341 and 342 frequency convert the clock signals from the internal clocks 371 and 372 to generate carrier signals for PWM control. The microcontroller 341 of the first control circuit 301 performs frequency conversion at a first conversion ratio, and the microcontroller 342 of the second control circuit 302 performs frequency conversion at a second conversion ratio different from the first conversion ratio. do.

With this configuration, clock elements having the same frequency can be used as the internal clocks 371 and 372, and carrier signals having a desired frequency difference can be easily obtained using conversion coefficients. The clock elements having the same frequency are, for example, clock elements incorporating a crystalline lens of the same standard, thereby avoiding an increase in the number of types of parts. Further, there may be individual differences between the internal clocks 371 and 372. In other words, as mentioned above, individual differences of about 50 Hz can occur between crystalline lenses of the same standard, but if the conversion coefficients differ by about 5%, a frequency difference that far exceeds such individual differences will occur, so the existence of individual differences is unlikely. Not a problem.

Furthermore, as another configuration, a configuration may be considered in which a circuit is provided to check the frequency synchronization state of carrier signals, and the frequency of the carrier signals is changed based on the confirmed synchronization state to obtain a desired frequency difference. . This configuration has the advantage that a desired frequency difference can be obtained even if, for example, the same variable is erroneously set as the conversion coefficient. Next, a modification of this embodiment will be described. FIG. 9 is a diagram showing a circuit configuration of a motor drive unit 1000 in a modified example with different circuit wiring. In the modification shown in FIG. 9, the ground ends of the first inverter 101 and the second inverter 102 are separated from each other. Even with such a separated configuration, torque ripple will occur if a shift occurs in the frequency of the carrier signal. Therefore, in the modified example shown in FIG. 9 as well, the frequency of the torque ripple deviates from the rotation speed of the motor 200 by providing the above-mentioned difference in the frequency of the carrier signal of PWM control between the first system and the second system. At the same time, the range of human senses is also out of bounds. As a result, problems such as noise, vibration, and control disturbance caused by torque ripple are suppressed.

(Embodiment of power steering device)

Vehicles such as automobiles are generally equipped with a power steering device. A power steering device generates an auxiliary torque to assist the steering torque of a steering system generated when a driver operates a steering wheel. The auxiliary torque is generated by an auxiliary torque mechanism, and can reduce the operational burden on the driver. For example, the auxiliary torque mechanism includes a steering torque sensor, an ECU, a motor, a speed reduction mechanism, and the like. The steering torque sensor detects steering torque in a steering system. The ECU generates a drive signal based on a detection signal from the steering torque sensor. The motor generates an auxiliary torque corresponding to the steering torque based on the drive signal, and transmits the auxiliary torque to the steering system via the reduction mechanism.

The motor drive unit 1000 of the above embodiment is suitably used in a power steering device. FIG. 10 is a diagram schematically showing the configuration of an electric power steering device 2000 according to this embodiment. Electric power steering device 2000 includes a steering system 520 and an auxiliary torque mechanism 540.

The steering system 520 includes, for example, a steering handle 521, a steering shaft 522 (also referred to as a "steering column"), universal joints 523A, 523B, and a rotating shaft 524 (also referred to as a "pinion shaft" or "input shaft"). ).

Further, the steering system 520 includes, for example, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A, 552B, tie rods 527A, 527B, knuckles 528A, 528B, and left and right steered wheels (for example, left and right front wheels) 529A, 529B.

Steering handle 521 is connected to rotating shaft 524 via steering shaft 522 and universal joints 523A and 523B. A rack shaft 526 is connected to the rotating shaft 524 via a rack and pinion mechanism 525. The rack and pinion mechanism 525 includes a pinion 531 provided on the rotating shaft 524 and a rack 532 provided on the rack shaft 526. A right steered wheel 529A is connected to the right end of the rack shaft 526 via a ball joint 552A, a tie rod 527A, and a knuckle 528A in this order. Similarly to the right side, a left steered wheel 529B is connected to the left end of the rack shaft 526 via a ball joint 552B, a tie rod 527B, and a knuckle 528B in this order. Here, the right side and left side correspond to the right side and left side, respectively, as seen from the driver sitting in the seat.

According to the steering system 520, steering torque is generated when the driver operates the steering handle 521, and is transmitted to the left and right steering wheels 529A and 529B via the rack and pinion mechanism 525. This allows the driver to operate the left and right steering wheels 529A, 529B.

The auxiliary torque mechanism 540 includes, for example, a steering torque sensor 541, an ECU 542, a motor 543, a speed reduction mechanism 544, and a power supply device 545. The auxiliary torque mechanism 540 applies an auxiliary torque to the steering system 520 extending from the steering handle 521 to the left and right steering wheels 529A and 529B. Note that the auxiliary torque is sometimes referred to as "additional torque."

As the ECU 542, for example, the control circuits 301 and 302 shown in FIG. 1 and the like are used. Further, as the power supply device 545, for example, the inverters 101 and 102 shown in FIG. 1 etc. are used. Moreover, as the motor 543, the motor 200 shown in FIG. 1 etc. is used, for example. The ECU 542, motor 543, and power supply device 545 may constitute a unit generally referred to as a "mechanical and electrical integrated motor." Among the elements shown in FIG. 10, a mechanism configured with the elements excluding the ECU 542, the motor 543, and the power supply device 545 corresponds to an example of a power steering mechanism driven by the motor 543.

Steering torque sensor 541 detects the steering torque of steering system 520 applied by steering handle 521. ECU 542 generates a drive signal for driving motor 543 based on a detection signal (hereinafter referred to as "torque signal") from steering torque sensor 541. The motor 543 generates an auxiliary torque corresponding to the steering torque based on the drive signal. The auxiliary torque is transmitted to the rotating shaft 524 of the steering system 520 via the speed reduction mechanism 544. The speed reduction mechanism 544 is, for example, a worm gear mechanism. The auxiliary torque is further transmitted from the rotating shaft 524 to the rack and pinion mechanism 525.

The power steering device 2000 is classified into a pinion assist type, a rack assist type, a column assist type, etc. depending on the location where the auxiliary torque is applied to the steering system 520. FIG. 10 shows a pinion assist type power steering device 2000. However, the power steering device 2000 is also applicable to rack assist type, column assist type, etc.

In addition to the torque signal, for example, a vehicle speed signal can also be input to the ECU 542. The microcontroller of the ECU 542 can perform PWM control of the motor 543 based on a torque signal, a vehicle speed signal, and the like.

ECU 542 sets a target current value based on at least the torque signal. Preferably, the ECU 542 sets the target current value by considering the vehicle speed signal detected by the vehicle speed sensor and further by considering the rotor rotation signal detected by the angle sensor. The ECU 542 can control the drive signal of the motor 543, that is, the drive current, so that the actual current value detected by the current sensor (see FIG. 1) matches the target current value.

According to the power steering device 2000, the left and right steered wheels 529A and 529B can be operated by the rack shaft 526 using a composite torque obtained by adding the auxiliary torque of the motor 543 to the driver's steering torque. In particular, by using the motor drive unit 1000 of the above embodiment, problems such as noise and vibration caused by torque ripple are reduced, and smooth power assist is realized.

Here, a power steering device is mentioned as an example of how to use the drive control device and drive device of the present invention, but the method of using the drive control device and drive device of the present invention is not limited to the above, and can be applied to pumps, compressors, etc. It can be used in a wide range of ways.

The embodiments described above should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments described above, and it is intended that all changes within the meaning and range equivalent to the claims are included.

101, 102: Inverter 200: Motor 301, 302: Control circuit 311, 312: Power supply circuit 321, 322: Angle sensor 331, 332: Input circuit 341, 342: Microcontroller 351, 352: Drive circuit 361, 362: ROM 371 , 372: Internal clock 401, 402: Current sensor 403, 404: Power supply 1000: Motor drive unit 2000: Power steering device

Claims (5)

A drive control device that controls driving of a motor, comprising: a first inverter connected to one end of a winding of the motor; a second inverter connected to the other end of the motor; and a second inverter connected to the other end of the winding of the motor. A first control circuit that performs PWM control; and a second control circuit that performs PWM control on the second inverter, and the first control circuit and the second control circuit control the carrier signal of the PWM control. A drive control device in which the frequency has a frequency difference that is greater than or equal to the product of the maximum rotational speed of the motor and the number of pole pairs. The drive control device according to claim 1, wherein the frequency difference is a value excluding 3n times (n is a natural number) the product in mechanical angle. The first control circuit and the second control circuit convert the frequency of a clock signal obtained from a vibrator to generate a carrier signal for PWM control, and the first control circuit converts the frequency at a first conversion ratio. 3. The drive control device according to claim 1, wherein the second control circuit converts the frequency at a second conversion ratio different from the first conversion ratio. A motor drive device comprising: the drive control device according to any one of claims 1 to 3; and a motor whose drive is controlled by the drive control device. A power steering device comprising: the drive control device according to claim 1; a motor whose drive is controlled by the drive control device; and a power steering mechanism driven by the motor.

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