CN113228497B

CN113228497B - Drive control device, motor drive device, and power steering device

Info

Publication number: CN113228497B
Application number: CN201980086659.4A
Authority: CN
Inventors: 锅师香织; 北村高志
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2018-12-28
Filing date: 2019-12-10
Publication date: 2024-04-16
Anticipated expiration: 2039-12-10
Also published as: WO2020137511A1; JP7444075B2; CN113228497A; JPWO2020137511A1

Abstract

One embodiment of the drive control device is a drive control device that controls driving of a motor, including: a first inverter connected to one end of a winding of the motor; a second inverter connected to the other end opposite to the one end; a first control circuit that performs PWM control of the first inverter; and a second control circuit that performs PWM control of the second inverter, wherein the first control circuit and the second control circuit have a frequency difference of a carrier signal of PWM control that is equal to or greater than a product of a maximum rotation speed and a pole pair number of the motor.

Description

Drive control device, motor drive device, and power steering device

Technical Field

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

Background

Conventionally, a non-wired motor having n-phase windings (coils) and these coils are not wired to each other is known. As a driving method of such a motor without wiring, a driving system called a full bridge is known in which inverters are connected to both ends of coils of each phase. In the driving of a full-bridge, non-wired motor, normally, two inverters are driven, and when an abnormality occurs, one inverter is switched to a neutral point to perform three-phase control. Further, from the viewpoint of reducing the failure rate, a configuration is known in which two inverters are controlled by two control circuits. For example, in patent document 1, a first control unit controls driving of a first inverter, and a second control unit controls driving of a second inverter.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication 2016-073097

Disclosure of Invention

Technical problem to be solved by the invention

If from the viewpoint of reducing the failure rate, it is preferable that there is no independent driving of the circuit portions common to the control circuits with each other. However, in the case of the full-bridge drive system, if the synchronization of the frequencies in the PMW carrier signals of the respective control circuits is shifted, the torque ripple of the motor is deteriorated, and causes defects such as noise and vibration. Accordingly, an object of the present invention is to reduce the occurrence of a problem caused by torque ripple while ensuring the independence of each control circuit.

Technical proposal adopted for solving the technical problems

One embodiment of the drive control device of the present invention is a drive control device for controlling 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 opposite to the one end; a first control circuit that performs PWM control of the first inverter; and a second control circuit that performs PWM control of the second inverter, wherein the first control circuit and the second control circuit have a frequency difference of a carrier signal of PWM control that is equal to or greater than a product of a maximum rotation speed and a pole pair number of the motor. In addition, one embodiment of the motor driving device of the present invention includes the driving control device and a motor controlled and driven by the driving control device.

In addition, one embodiment of the power steering apparatus of the present invention includes: the drive control device; a motor controlled and driven by the drive control device; and a power steering mechanism driven by the motor.

Effects of the invention

According to the present invention, it is possible to reduce the occurrence of a defect caused by torque ripple while ensuring the independence of each control circuit.

Drawings

Fig. 1 is a diagram schematically showing a typical block structure of a motor drive unit of the present embodiment.

Fig. 2 is a diagram schematically showing a typical circuit configuration of the motor drive unit of the present embodiment.

Fig. 3 is a graph 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 PWM signals.

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 driving unit in a modification example in which circuit wiring is different.

Fig. 10 is a diagram schematically showing the structure of the electric power steering apparatus according to the present embodiment.

Detailed Description

Embodiments of a drive control device, a drive device, and a power steering device of the present disclosure are described in detail below with reference to the drawings. However, in order to avoid unnecessary redundancy of the following description, those skilled in the art will readily understand that the above detailed description may be omitted. For example, detailed descriptions of well-known matters or repeated descriptions of substantially the same structure may be omitted.

In this specification, embodiments of the present disclosure will be described taking as an example a drive control device that supplies electric 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"). However, a drive control device that supplies electric power from a power source to an n-phase motor having four-phase or five-equal n-phase windings (n is an integer of 4 or more) is also within the scope of the present invention.

(Structure of motor drive unit 1000)

Fig. 1 is a diagram schematically showing a block structure of a motor drive unit 1000 of the present embodiment. The motor driving unit 1000 includes inverters 101 and 102, a motor 200, and control circuits 301 and 302.

In this specification, a motor driving unit 1000 having a motor 200 as a constituent element will be described. The motor driving unit 1000 having the motor 200 corresponds to an example of the driving device of the present invention. However, the motor driving unit 1000 may be a device for driving the motor 200, the constituent elements of which are omitted from the motor 200. The motor driving unit 1000 without the motor 200 corresponds to an example of the driving control device of the present invention.

The motor driving unit 1000 converts electric power from a power source (403, 404 of fig. 2) into electric power supplied to the motor 200 through two inverters 101, 102. The inverters 101 and 102 can convert dc power into three-phase ac power, which is an analog sine wave of a U-phase, a V-phase, and a W-phase, for example. The two inverters 101, 102 comprise current sensors 401, 402, respectively.

The motor 200 is, for example, a three-phase ac motor. Motor 200 has coils of U-phase, V-phase and W-phase. The coil is wound in a concentrated or distributed manner, for example.

The first inverter 101 is connected to one end 210 of the coil of the motor 200, a driving voltage is applied to the one end 210, the second inverter 102 is connected to the other end 220 of the coil of the motor 200, and a driving voltage is applied to the other end 220. In the present specification, "connection" of members (constituent elements) to each other means electrical connection unless otherwise specified.

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

The motor driving unit 1000 is connected to the independent first power source 403 and the second power source 404, respectively. The power supplies 403 and 404 generate a predetermined power supply voltage (for example, 12V). As the power sources 403 and 404, for example, dc power sources are used. However, the power sources 403 and 404 may be AC-DC converters or DC-DC converters, or may be batteries (storage batteries). In fig. 2, the first power supply 403 for the first inverter 101 and the second power supply 404 for the second inverter 102 are shown as an example, but the motor driving unit 1000 may be connected to a single power supply common to the first inverter 101 and the second inverter 102. The motor driving unit 1000 may be provided with a power supply therein.

The motor driving 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 the second inverter 102 and the second control circuit 302. The inverter 101 and the control circuit 301 of the first system are powered by a first power supply 403. The inverter 102 and control circuit 302 of the second system are powered by a second power supply 404.

The first inverter 101 includes a bridge circuit having three branches. Each branch of the first inverter 101 includes a high-side switching element connected between the power supply and the motor 200, and a low-side switching element connected between the motor 200 and the ground. Specifically, the U-phase branch circuit includes a high-side switching element 113H and a low-side switching element 113L. The V-phase branch circuit includes a high-side switching element 114H and a low-side switching element 114L. The W-phase branch circuit includes a high-side switching element 115H and a low-side switching element 115L. As the switching element, for example, a field effect transistor (MOSFET or the like) or an insulated gate bipolar transistor (IGBT or the like) is used. In addition, when the switching element is an IGBT, a diode (flywheel) is connected in anti-parallel with the switching element.

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

The number of shunt resistors may not be three. For example, two shunt resistors 113R, 114R, V for U-phase and V-phase, two shunt resistors 114R, 115R for W-phase, or two shunt resistors 113R, 115R for U-phase and W-phase may be used. The number of shunt resistors used and the configuration of the shunt resistors can be appropriately determined in consideration of the product cost, design specifications, and the like.

The second inverter 102 includes a bridge circuit having three branches. Each branch of the second inverter 102 includes a high-side switching element connected between the power supply and the motor 200, and a low-side switching element connected between the motor 200 and the ground. Specifically, the U-phase branch circuit includes a high-side switching element 116H and a low-side switching element 116L. The V-phase branch circuit includes a high-side switching element 117H and a low-side switching element 117L. The W-phase branch circuit includes a high-side switching element 118H and a low-side switching element 118L. As in the first inverter 101, the second inverter 102 includes, for example, shunt resistors 116R, 117R, and 118R.

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

Referring again to fig. 1. 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. The control circuits 301, 302 are connected to the inverters 101, 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 control the position (rotation angle), rotation speed, current, and the like of the target rotor to realize closed-loop control. The rotational speed is obtained by differentiating the rotational angle (rad) with time, and is shown by the rotational speed (rpm) at which the rotor rotates in a unit time (for example, 1 minute). The control circuits 301 and 302 can control the target motor torque. The control circuits 301 and 302 may include torque sensors for torque control, but can perform torque control even if the torque sensors are omitted. In addition, a sensorless algorithm may be provided instead of the angle sensors 321 and 322. The power supply circuits 311 and 312 generate DC voltages (for example, 3V and 5V) required for the respective blocks 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 may also be implemented by a combination of a Magnetoresistive (MR) sensor having MR elements and a sensor magnet. The angle sensors 321, 322 detect the rotation angle of the rotor of the motor 200, and output rotation signals showing the detected rotation angle to the microcontrollers 341, 342. Depending on the motor control method (e.g., sensorless control), the angle sensors 321, 322 are sometimes omitted.

The input circuits 331 and 332 receive motor current values (hereinafter referred to as "actual current values") detected by the 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 needed, and output the actual current value to the microcontrollers 341 and 342. The input circuits 331, 332 are analog-to-digital conversion circuits.

The microcontrollers 341, 342 receive the rotation signals of the rotors detected by the angle sensors 321, 322, and receive the actual current values output from the input circuits 331, 332. The microcontrollers 341 and 342 generate PWM signals based on the actual current values and the rotation signals of the rotors, and output the generated PWM signals to the driving circuits 351 and 352. For example, the microcontrollers 341, 342 generate PWM signals for controlling switching operations (on or off) of the respective switching elements in the inverters 101, 102.

Each microcontroller 341, 342 has an internal clock 371, 372. The generation of the PWM signals in each microcontroller 341, 342 is performed in accordance with the clock signals from the internal clocks 371, 372. That is, each of the microcontrollers 341 and 342 frequency-converts the clock signal obtained from the oscillator of the internal clocks 371 and 372 to generate the PWM-controlled carrier signal.

The basic frequency of the PWM signal generated by each microcontroller 341, 342 (i.e. the frequency of the carrier signal in PWM control) has a frequency difference between the microcontrollers 341, 342 of, for example, 1 kHz. As a result, as will be described in detail later, torque pulsation due to the frequency difference occurs in a sufficiently high frequency range. Therefore, noise, vibration, and the like associated with torque pulsation deviate from a frequency region that can be perceived by a human, and unpleasant noise and vibration to the human are suppressed.

The drive circuits 351, 352 are typically gate drivers. The driving circuits 351 and 352 generate control signals (for example, gate control signals) for controlling switching operations of the switching elements in the first inverter 101 and the second inverter 102 based on the PWM signals, and supply the generated control signals to the switching elements. The microcontrollers 341, 342 may have the function of the drive circuits 351, 352. In this case, the driving circuits 351, 352 are omitted.

The ROM361, 362 is, for example, a writable memory (e.g., PROM), a rewritable memory (e.g., flash memory), or a read only memory. The ROMs 361, 362 store control programs including instruction sets for causing the microcontrollers 341, 342 to control the inverters 101, 102, and the like. For example, the control program is temporarily developed in a RAM (not shown) at the time of startup.

(action of motor drive Unit 1000)

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

The control circuits 301, 302 drive the motor 200 by performing three-phase energization control using both the first inverter 101 and the second inverter 102. Specifically, the control circuits 301 and 302 perform three-phase energization control by performing switching control on the switching elements of the first inverter 101 and the switching elements of the second inverter 102. Fig. 3 is a diagram showing the current values flowing through the coils of the respective phases of the motor 200.

Fig. 3 illustrates currents obtained by plotting current values of respective coils of U-phase, V-phase, and W-phase flowing through the motor 200 when the first inverter 101 and the second inverter 102 are controlled in accordance with three-phase energization controlWaveform (sine wave). The horizontal axis of fig. 3 shows the motor electrical angle (deg), and the vertical axis shows the current value (a). I _pk The maximum current value (peak current value) of each phase is shown. In addition to the sine wave illustrated in fig. 3, the inverters 101 and 102 may drive the motor 200 using, for example, a rectangular wave.

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

In fig. 4 and 5, a branch, for example, a U-phase, of the branches that the inverters 101, 102 have is shown. As described above, the high-side switching element 113H and the low-side switching element 113L on the first inverter 101 side, and the high-side switching element 116H and the low-side switching element 116L on the second inverter 102 side are included in the branch of the U-phase.

The high-side switching element 113H and the low-side switching element 113L on the first inverter 101 side are not simultaneously turned on, and when one is turned on, the other is turned off. Similarly, the high-side switching element 116H and the low-side switching 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, one of the two inverters 101 and 102 (the second inverter 102 in fig. 4) turns on the high-side switching elements 113H and 116H, and the other one (the first inverter 101 in fig. 4) turns on the low-side switching elements 113L and 116L. As a result, current flows from one side to the other side as indicated by an arrow in the figure.

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

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

The PWM signal is a pulse signal of 2 values, a first value showing the application of a voltage and a second value showing the stopping of the application are alternately generated. The pulse of the PWM signal is repeated with a period T0, and the period T0 is divided into a duration T1 of a first value and a duration T2 of a second value.

Since the PWM signal is a high-frequency signal such as 20kHz as described above, the period T0 is a short period such as 50 μsec. Accordingly, the effective voltage (effective voltage) applied to the motor 200 becomes a voltage averaged in the period T0, and the ratio (duty ratio) of the period T0 to the duration T1 of the first value is equal to the ratio of the power supply voltage to the effective voltage. The effective voltage is, for example, a voltage that changes with time according to a current value that changes as shown in the current waveform of fig. 3. This time variation of the effective voltage is achieved by controlling the duty cycle of the PWM signal by the microcontrollers 341, 342.

The two microcontrollers 341, 342 each generate a carrier signal of period T0 from which a PWM signal is generated, but as described above, the microcontrollers 341, 342 differ from each other in the frequency of the carrier signal. Thus, the period T0 is not consistent between the microcontrollers 341, 342, and the PWM signals are shifted in frequency from each other. Such synchronization deviation generates torque pulsation in the motor 200. Here, an analog test of torque ripple generated by the frequency difference between PWM signals will be described. Table 1 shows test conditions from the first test to the fourth test.

TABLE 1

Test number	Frequency difference	PWM frequency of first inverter	PWM frequency of the second inverter
				1	50Hz	20.0kHz	19.95kHz
2	5Hz	20.0kHZ	19.995kHz
				3	0.5Hz	20.0kHz	19.9995kHz
4	0.05Hz	20.0kHz	19.99995kHz

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

In the graph showing the results of the first test, there are many peaks in the frequency region of hundreds of Hz, and the peak at the 100Hz position corresponding to 2 times the frequency difference is particularly large. It is known that under the first test conditions, a large torque ripple corresponding to the large peak value is generated.

In the second to fourth tests, large peaks were not generated in the frequency region of hundreds of Hz. Therefore, it is found that torque ripple hardly occurs if the frequency difference is about 5Hz or less. However, for example, in the case of a clock element of a quartz resonator, a frequency difference of, for example, 10Hz or more is likely to occur due to individual differences of the quartz resonator, and it is difficult to suppress the frequency to about 5Hz or less between the independent microcontrollers 341, 342. Thus, an analog test of the spread spectrum is performed conversely. Table 2 shows the test conditions from the fifth test to the eleventh test.

TABLE 2

Test number	Frequency difference	First inversePWM frequency of a transformer	PWM frequency of the second inverter
				5	0Hz	20.0kHz	20.0kHz
6	+1000Hz	21.0kHz	20.0kHz
				7	-1000Hz	20.0kHz	19.0kHz
8	+500Hz	20.5kHz	20.0kHz
				9	-500Hz	20.0kHz	19.5kHz
10	+100Hz	20.1kHz	20.0kHz
				11	-100Hz	20.0kHz	19.9kHz

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

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

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

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

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

In test 10, the frequency of the first system was set to 20.1kHz with respect to the fundamental frequency of +100Hz, and the frequency of the second system was set to 20.0kHz.

In the eleventh test, the frequency of the first system was set to 20.0kHz, and the frequency of the second system was set to 19.9kHz at-100 Hz with respect to the fundamental frequency. Fig. 8 is a graph showing the results of the fifth to eleventh tests. Fig. 8 also shows a three-dimensional graph, in which the height axis shows torque intensity, the left-depth axis shows frequency, and the right-depth axis shows test number. In fig. 8, a large peak around 500Hz in the graph is a peak of a frequency component corresponding to the rotational speed of the motor, and is not torque ripple. In the graph showing the results of the fifth test, no particular peak was generated in the frequency region of several hundred Hz. Therefore, it is known that torque pulsation is not generated if the frequencies are synchronized.

In the graph showing the results of the tenth test and the eleventh test, there are many peaks in the frequency region of hundreds of Hz, and the peak at the 200Hz position corresponding to 2 times the frequency difference is particularly large. It is known that under the conditions of the tenth test and the eleventh test, a large torque ripple corresponding to the large peak value is generated.

In the sixth test to the ninth test, a large peak was not generated in a frequency region of several hundred Hz. In the eighth to ninth tests, the frequency difference was 2 times 1kHz, and a peak was generated to some extent at a position of 1kHz in the graph. Then, torque pulsation corresponding to the peak value is generated. However, since the vibration of 1kHz is a vibration exceeding the human feel area, it is possible to suppress the noise accompanying the torque pulsation and other drawbacks. In the sixth to seventh tests, the frequency difference was 2 times 2kHz, and noise and the like were further deviated from the human sensory area.

For example, in the case of use in a power steering apparatus or the like, the rotation speed of the motor 200 varies according to the situation. As a result of the change in the rotational speed of the motor, when the rotational speed of the motor 200 overlaps with the frequency of the torque ripple, a disturbance may occur in the drive control of the motor.

In the first system and the second system, when the frequency of the PWM-controlled carrier signal has a frequency difference of more than the product of the maximum rotation speed of the motor 200 and the pole pair number, the frequency of the torque ripple generated at 2n times (n is a natural number) of the frequency difference deviates from the rotation speed of the motor 200 and also deviates from the human feel area. As a result, it is possible to suppress noise, vibration, control disturbance, and other problems associated with torque pulsation.

The frequency difference of the PWM-controlled carrier signal is preferably a value obtained by removing 3n times the product (n is a natural number) from the mechanical angle. Even in the case where the frequencies of the carrier signals in the first system and the second system are completely synchronized, torque pulsation is generated 6n times in the motor 200. If the frequency difference of the carrier signals is 3n times the above product of the mechanical angles, it is possible to avoid that the torque ripple caused by the frequency difference overlaps with the torque ripple of 6n times. As a specific structure for obtaining the frequency difference between the carrier signals from each other, two structures can be considered.

The first configuration is a configuration in which clock elements whose frequencies of clock signals differ from each other by, for example, about 5% are used as the two internal clocks 371 and 372 shown in fig. 1. By using such a clock element, the same program can be used as a program for driving control (particularly, a program for generating a carrier signal and PWM control) in the two microcontrollers 341, 342.

The second configuration is a configuration in which the frequency conversion coefficients differ from each other by, for example, about 5% in the two microcontrollers 341, 342. The conversion coefficient is used when the two microcontrollers 341, 342 frequency-convert clock signals from the internal clocks 371, 372 to generate PWM-controlled carrier signals. 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.

In this configuration, the internal clocks 371 and 372 can be clock elements of the same frequency, and each carrier signal having a desired frequency difference can be easily obtained by the conversion coefficient. The clock elements with the same frequency are, for example, clock elements with crystals of the same specification built in, and increase in the kinds of components is avoided. In addition, the internal clocks 371, 372 may also have individual differences from each other. That is, although individual differences of about 50Hz can be generated in crystals of the same specification as described above, if the conversion coefficients differ by about 5%, frequency differences far exceeding such individual differences are generated, and therefore the presence of individual differences is not a problem.

As another configuration, the following configuration may be considered: the apparatus includes a circuit for confirming the synchronization state of the frequencies of the carrier signals, and the circuit obtains a desired frequency difference by changing the frequencies of the carrier signals according to the confirmed synchronization state. In this structure, there are the following advantages: for example, even when the same variable is erroneously set as the conversion coefficient, a desired frequency difference can be obtained. Next, a modification of the present embodiment will be described. Fig. 9 is a diagram showing a circuit configuration of the motor driving unit 1000 in a modification example in which circuit wiring is different. In the modification shown in fig. 9, the ground terminals of the first inverter 101 and the second inverter 102 are separated from each other. Even with such a separate structure, torque ripple occurs when the frequency of the carrier signal varies. Therefore, in the modification shown in fig. 9, in the first system and the second system, by setting the above-described difference in the frequency of the PWM-controlled carrier signal, the frequency of the torque ripple is deviated from the rotation speed of the motor 200 and also from the human feel area. As a result, it is possible to suppress noise, vibration, control disturbance, and other problems associated with torque pulsation.

(embodiment of Power steering device)

Vehicles such as automobiles generally include a power steering device. The power steering apparatus generates an assist torque for assisting a steering torque of a steering system generated by a driver operating a steering handle. The assist torque is generated by the assist torque mechanism, and the load of the operation of the driver can be reduced. For example, the assist torque mechanism is constituted by a steering torque sensor, an ECU, a motor, a speed reduction mechanism, and the like. The steering torque sensor detects a steering torque in the steering system. The ECU generates a drive signal based on a detection signal of the steering torque sensor. The motor generates an assist torque corresponding to the steering torque based on the drive signal, and transmits the assist torque to the steering system via the reduction mechanism.

The motor drive unit 1000 of the above embodiment is applied to a power steering device. Fig. 10 is a diagram schematically showing the structure of an electric power steering apparatus 2000 according to the present embodiment. The electric power steering apparatus 2000 includes a steering system 520 and an assist 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 shaft joints 523A, 523B, and a rotation shaft 524 (also referred to as a "pinion shaft" or an "input shaft").

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 steering wheels (e.g., left and right front wheels) 529A, 529B.

The steering handle 521 is connected to a rotation shaft 524 via a steering shaft 522 and universal joints 523A and 523B. A rack shaft 526 is connected to the rotation shaft 524 via a rack-and-pinion mechanism 525. The rack-and-pinion mechanism 525 has a pinion 531 provided on the rotation shaft 524 and a rack 532 provided on the rack shaft 526. The right steering 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 steering 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 the left side correspond to the right side and the left side, respectively, observed by a driver sitting in the seat.

According to the steering system 520, steering torque is generated by the driver operating the steering handle 521, and is transmitted to the left and right steering wheels 529A, 529B via the rack-and-pinion mechanism 525. Thus, the driver can operate the left and right steering wheels 529A and 529B.

The assist torque mechanism 540 includes, for example, a steering torque sensor 541, an ECU542, a motor 543, a reduction mechanism 544, and an electric power supply device 545. The assist torque mechanism 540 applies assist torque to the steering system 520 from the steering handle 521 to the left and right steering wheels 529A, 529B. In addition, the assist torque is sometimes referred to as "additional torque".

As the ECU542, for example, the control circuits 301 and 302 shown in fig. 1 and the like are used. As the power supply device 545, inverters 101 and 102 shown in fig. 1 and the like are used, for example. As the motor 543, for example, a motor 200 shown in fig. 1 or the like is used. The ECU542, the motor 543, and the power supply device 545 may constitute a unit commonly referred to as an "electromechanical motor". The mechanism constituted by the elements other than the ECU542, the motor 543, and the power supply device 545 among the elements shown in fig. 10 corresponds to an example of a power steering mechanism driven by the motor 543.

The steering torque sensor 541 detects a steering torque of the steering system 520 applied by the steering handle 521. The ECU542 generates a drive signal for driving the motor 543 based on a detection signal (hereinafter referred to as "torque signal") from the steering torque sensor 541. The motor 543 generates assist torque corresponding to steering torque based on the drive signal. The assist torque is transmitted to the rotating shaft 524 of the steering system 520 via the reduction mechanism 544. The reduction mechanism 544 is, for example, a worm gear mechanism. The assist torque is also transmitted from the rotation 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, and the like according to the portion where the assist torque is applied to the steering system 520. Fig. 10 shows a pinion-assisted power steering apparatus 2000. However, the power steering device 2000 is also applicable to a rack assist type, a column assist type, and the like.

Not only a torque signal, for example, a vehicle speed signal, but also an ECU542. The microcontroller of the ECU542 can PWM-control the motor 543 based on a torque signal, a vehicle speed signal, and the like.

The ECU542 sets a target current value based on at least the torque signal. Preferably, the ECU542 sets a target current value in consideration of a vehicle speed signal detected by a vehicle speed sensor and further in consideration of a rotation signal of the rotor detected by an angle sensor. The ECU542 can control a drive signal, that is, a drive current of the motor 543 so that an actual current value detected by a current sensor (see fig. 1) coincides with a target current value.

According to the power steering device 2000, the left and right steering wheels 529A and 529B can be operated by the rack shaft 526 using a combined torque obtained by adding the assist torque of the motor 543 to the steering torque of the driver. In particular, by using the motor drive unit 1000 according to the above embodiment, it is possible to reduce noise, vibration, and other defects caused by torque pulsation, and to realize smooth power assist.

In addition, although a power steering device is exemplified as an example of the method of using the drive control device and the drive device of the present invention, the method of using the drive control device and the drive device of the present invention is not limited to the above method, and the drive control device and the drive device of the present invention can be used in a wide range of applications such as pumps and compressors.

The above embodiments should be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the claims, not by the above-described embodiments, but by all changes within the meaning and range equivalent to the claims.

Symbol description

101. 102: an inverter; 200: a motor; 301. 302: a control circuit; 311. 312: a power supply circuit; 321. 322: an angle sensor; 331. 332: an input circuit; 341. 342: a microcontroller; 351. 352: a driving circuit; 361. 362: a ROM; 371. 372: an internal clock; 401. 402: a current sensor; 403. 404: a power supply; 1000: a motor driving unit; 2000: a power steering apparatus.

Claims

1. A drive control device for controlling the drive of a motor is provided with:

a first inverter connected to one end of a winding of the motor;

a second inverter connected to the other end opposite to the one end;

a first control circuit that performs PWM control of the first inverter; and

a second control circuit that performs PWM control on the second inverter,

in the first control circuit and the second control circuit, the frequency of the PWM-controlled carrier signal has a frequency difference of a product of a maximum rotation speed of the motor and a pole pair number or more.

2. The drive control apparatus according to claim 1, wherein,

the frequency difference is a value of 3n times the product removed from the mechanical angle, n being a natural number.

3. The drive control apparatus according to claim 1 or 2, wherein,

the first control circuit and the second control circuit frequency-convert a clock signal obtained from a vibrator and generate a PWM-controlled carrier signal,

the first control circuit performs frequency conversion by a first conversion ratio, and the second control circuit performs frequency conversion by a second conversion ratio different from the first conversion ratio.

4. A motor driving device is provided with:

a drive control apparatus according to any one of claims 1 to 3; and

and a motor, the driving of which is controlled by the driving control device.

5. A power steering device is provided with:

a drive control apparatus according to any one of claims 1 to 3;

a motor, the driving of which is controlled by the driving control device; and

and a power steering mechanism driven by the motor.