JP2017169381A - Drive unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a voltage of a first power line (a high-voltage system power line) into a proper voltage.SOLUTION: Using a modulation degree Rm1 of a first motor, drive system loss Loss 1 determined for each drive point of the first motor as a relationship between the modulation degree Rm1 and loss and based on a loss map, a modulation degree of a second motor and drive system loss determined for each drive point of the second motor as a relationship between the modulation degree Rm of the second motor and loss and based on a loss map, a target voltage is set so that a sum of drive system loss in a drive system including each of the motors becomes minimum and a step-up converter is controlled so that a voltage of a high-voltage side power line of the step-up converter becomes a target voltage. Thus, a voltage of a high-voltage system power line can be set properly.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a drive device, and more particularly to a drive device including a plurality of motors, a plurality of inverters, and a converter.

  2. Description of the Related Art Conventionally, as this type of drive device, a device including two motors, two inverters, a battery, and a converter has been proposed (for example, see Patent Document 1). Two inverters drive two motors, respectively. The converter is connected to a first power line to which two inverters are connected and a second power line to which a battery is connected, and converts a voltage between the first power line and the second power line. . In this apparatus, the relationship between the voltage of the first power line and the loss of the motor and the inverter is determined and stored in advance as a predetermined relationship for each motor and each driving point of the motor. Then, using such a relationship, the system voltage command is set so that the sum of the losses of the respective motors is minimized, and the converter is controlled so that the voltage of the first power line becomes the system voltage command. Thereby, the loss of the whole apparatus is reduced.

JP 2010-35386 A

  In the above drive device, when the temperature of each motor changes, the back electromotive voltage of each motor changes, and the voltage of the first power line that minimizes the loss changes. Therefore, even if the system voltage command is set so that the loss is minimized by using the predetermined relationship between the voltage of the first power line and the loss, the system voltage command is actually set to a voltage at which the loss is minimized. In other words, the voltage of the first power line may not be an appropriate voltage.

  The drive device of the present invention is mainly intended to set the voltage of the first power line to an appropriate voltage.

  The drive device of the present invention employs the following means in order to achieve the main object described above.

The drive device of the present invention is
Multiple motors,
A plurality of inverters for driving the plurality of motors;
Battery,
A converter connected to a first power line to which the plurality of inverters are connected and a second power line to which the battery is connected, and for converting a voltage between the first power line and the second power line;
Control means for controlling the plurality of inverters so that the plurality of motors are driven by a torque command set for each motor and controlling the converter so that the voltage of the first power line becomes a target voltage. ,
In a drive device comprising:
The control means has a relationship between a modulation degree based on the torque command and the voltage of the first power line, and a drive system loss obtained by adding a loss of the inverter that drives the motor to the modulation degree and the loss of the motor. Based on a predetermined relationship determined for each motor and for each driving point of the motor, the target voltage is set so that the sum of drive system losses of the plurality of motors is minimized.
This is the gist.

  In the drive device of the present invention, the plurality of inverters are controlled so that the plurality of motors are driven by a torque command set for each motor, and the converter is controlled so that the voltage of the first power line becomes the target voltage. To do. The degree of modulation based on the torque command and the voltage of the first power line, and the relationship between the degree of modulation and the loss of the motor plus the loss of the inverter that drives the motor, for each motor and each motor drive point. And the target voltage is set so that the sum of the drive system losses of the plurality of motors is minimized. It is considered that the degree of modulation that minimizes the drive system loss does not change even if the back electromotive force changes with the change in the motor temperature. Therefore, the voltage of the first power line can be made more appropriate by setting the target voltage so that the sum of the drive system losses of the plurality of motors based on the modulation degree and the predetermined relationship is minimized.

  In such a driving apparatus of the present invention, the control means is configured to calculate the driving system loss of the plurality of motors calculated based on the modulation degree and a slope of the driving system loss with respect to the modulation degree in the predetermined relationship. The target voltage may be set so that the sum of the slopes becomes 0.

It is a block diagram which shows the outline of a structure of the drive device 20 as one Example of this invention. It is explanatory drawing which shows an example of the relationship between modulation degree Rm1 and drive system loss Loss1 when the target drive point of motor MG1 is a certain drive point. It is explanatory drawing which shows an example of the relationship between modulation degree Rm2 and drive system loss Loss2 when the target drive of motor MG2 is a certain drive point. It is a control block diagram which shows an example of the process which sets target voltage VH * using inclination (DELTA) Loss. It is explanatory drawing which shows an example of the tangent in a loss map. It is explanatory drawing which shows an example of the relationship between the modulation degree Rm1 and the inclination | tilt inclination (DELTA) Loss1 in a certain drive point of motor MG1.

  Next, the form for implementing this invention is demonstrated using an Example.

  FIG. 1 is a configuration diagram showing an outline of a configuration of a drive device 20 as an embodiment of the present invention. As shown in FIG. 1, drive device 20 includes motors MG 1 and MG 2, inverters 22 and 24, battery 30, boost converter 34, and electronic control unit (hereinafter referred to as “ECU”) 50.

  The motors MG1 and MG2 are configured as synchronous generator motors, for example.

  The inverters 22 and 24 are composed of six transistors T11 to T16 and T21 to 26 and six diodes D11 to D16 and D21 to D26 connected in parallel to the transistors T11 to T16 and T21 to T26 in the reverse direction. Yes. Two transistors T11 to T16 and T21 to T26 are arranged in pairs so as to be on the source side and the sink side with respect to the positive and negative buses of the high voltage power line 40, respectively. The three-phase coils (U-phase, V-phase, W-phase) of the motors MG1, MG2 are connected to the connection points. Therefore, by adjusting the on-time ratios of the transistors T11 to T16 and T21 to T26 that make a pair while the voltage is applied to the inverters 22 and 24, a rotating magnetic field can be formed in the three-phase coil, and the motors MG1, The MG2 can be driven to rotate. Since the inverters 22 and 24 share the positive and negative buses of the high voltage system power line 40, the power generated by either the motor MG1 or MG2 can be supplied to another motor. A smoothing capacitor 42 is connected to the positive and negative buses of the high voltage system power line 40.

  The battery 30 is configured as a lithium ion secondary battery or a nickel hydride secondary battery, and is connected to the low voltage system power line 44. A smoothing capacitor 46 is connected to the positive and negative buses of the low voltage system power line 44.

  Boost converter 34 is connected to high voltage power line 40 to which inverters 22 and 24 are connected, and low voltage power line 44 to which battery 30 is connected. Boost converter 34 includes two transistors T31 and T32, two diodes D31 and D32, and a reactor L. The transistor T31 is connected to the positive line of the high voltage system power line 40. The transistor T32 is connected to the transistor T31 and the negative electrodes of the high voltage system power line 40 and the low voltage system power line 44. The two diodes D31 and D32 are respectively connected in parallel to the transistors T31 and T32 in the reverse direction. The reactor L is connected to a connection point between the transistors T31 and T32 and a positive line of the low voltage system power line 44. The step-up converter 34 adjusts the ratio of the on-time of the transistors T31 and T32 by the ECU 50 to boost the power of the low voltage system power line 44 and supply it to the high voltage system power line 40 or the high voltage system. The power of the power line 40 is stepped down and supplied to the low voltage system power line 44.

  The ECU 50 is configured as a microprocessor centered on a CPU, and includes a ROM for storing a processing program, a RAM for temporarily storing data, and an input / output port in addition to the CPU. Note that the CPU, ROM, RAM, and input / output ports are not shown.

  Signals from various sensors are input to the ECU 50 via input ports. The signals input to the ECU 50 include the rotation positions θm1 and θm2 from the rotation position detection sensor that detects the rotation positions of the rotors of the motors MG1 and MG2, and the phase from the current sensor that detects the current flowing in each phase of the motor MG1. Current, voltage Vb1 from the voltage sensor installed between the terminals of the battery 30, current Ib1 from the current sensor attached to the output terminal of the battery 30 (positive value when discharging from the battery 30), attached to the battery 30 The temperature Tb1 from the selected temperature sensor, the voltage VH of the capacitor 42 (high voltage system power line 40) from the voltage sensor 42a attached between the terminals of the capacitor 42, and the voltage sensor 46a attached between the terminals of the capacitor 46. The voltage VL of the capacitor 46 (low voltage system power line 44) of the low voltage system power line 44 is positive For example, the current IL of the reactor L from a current sensor attached to the step-up converter 34 side with respect to the capacitor 46 of the polar line can be mentioned.

  Various control signals are output from the ECU 50 via an output port. Examples of signals output from the ECU 50 include switching control signals to the transistors T11 to T16 and T21 to T26 of the inverters 22 and 24, switching control signals to the transistors T31 and T32 of the boost converter 34, and the like.

  The ECU 50 calculates the rotational speeds Nm1 and Nm2 of the motors MG1 and MG2 based on the rotational positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from the rotational position detection sensor.

  In the drive device 20 of the embodiment thus configured, the ECU 50 performs switching control of the transistors T11 to T16 and T21 to T26 of the inverters 22 and 24 so that the motors MG1 and MG2 are driven by the torque commands Tm1 * and Tm2 *. .

  Here, control of the inverters 22 and 24 will be described. First, control of the inverter 22 will be described. In the embodiment, the inverter 22 is switching-controlled by selecting the pulse width modulation control (PWM control) mode or the rectangular wave control mode based on the rotation speed Nm1 of the motor MG1 and the torque command Tm1 *. The PWM control mode is a control mode in which the on-time ratio of the transistors T11 to T16 is adjusted by comparing the voltage command of the motor MG1 and the carrier wave (triangular wave) voltage. The PWM control mode includes a sine wave control mode and an overmodulation control mode. The sine wave control mode is a control mode in which, in the PWM control mode, a pseudo three-phase AC voltage obtained by converting a sine wave voltage command having an amplitude equal to or smaller than the amplitude of the carrier wave is supplied to the motor MG1. The overmodulation control mode is a control mode in which an overmodulation voltage obtained by converting a sinusoidal voltage command having an amplitude larger than the amplitude of the carrier wave is supplied to the motor MG1 in the PWM control mode. The rectangular wave control mode is a control mode for supplying a rectangular wave voltage to the motor MG1.

  In the PWM control mode, the ECU 50 first sets the sum of the phase currents Iu, Iv, Iw flowing in the U-phase, V-phase, and W-phase of the three-phase coil of the motor MG1 to 0 and uses the electrical angle θe of the motor MG1. , U-phase and V-phase phase currents Iu and Iv are coordinate-converted into d-axis and q-axis currents Id and Iq (three-phase to two-phase conversion). Here, the d-axis is the direction of the magnetic flux formed by the permanent magnet embedded in the rotor of the motor MG1. The q axis is a direction in which the electrical angle θe is advanced by π / 2 in the positive rotation direction of the motor MG1 with respect to the d axis.

  Based on the torque command Tm * of the motor MG1, d-axis and q-axis current commands Id * and Iq * are set. In this embodiment, the d-axis and q-axis current commands Id * and Iq * are determined in advance in accordance with a relationship between the torque command Tm * of the motor MG1 and the d-axis and q-axis current commands Id * and Iq *. It is stored in a ROM (not shown) as a current command setting map, and when a torque command Tm * of the motor MG1 is given, the corresponding d-axis and q-axis current commands Id * and Iq * are derived from the stored map. To be set. The current command setting map is determined so that, for example, torque corresponding to the torque command Tm1 * can be output from the motor MG1, and the magnitude Ir of the current command is minimized. The magnitude Ir of the current command is defined as the square root of the sum of the square of the current command Id * and the square of the current command Iq *.

  Next, using the d-axis and q-axis currents Id and Iq and the current commands Id * and Iq *, the difference between the d-axis and q-axis currents Id and Iq and the current commands Id * and Iq * is canceled out. In this way, the d-axis and q-axis voltage commands Vd * and Vq * are set. Subsequently, using the electrical angle θe of the motor MG1, the d-axis and q-axis voltage commands Vd * and Vq * are converted into U-phase, V-phase, and W-phase voltage commands Vu *, Vv *, and Vw * ( 2-phase to 3-phase conversion). The U-phase, V-phase, and W-phase voltage commands Vu *, Vv *, and Vw * are converted into PWM signals for switching the transistors T11 to T16 of the inverter 22. Then, by switching the PWM signal to the inverter 22, the switching control of the transistors T11 to T16 of the inverter 22 is performed. Here, the magnitude Vr of the voltage command is used as the amplitude of the sinusoidal voltage command used for the conversion of the PWM signal. The magnitude Vr of the voltage command is defined as the square root of the sum of the square of the voltage command Vd * and the square of the voltage flow command Vq *. The magnitude Vr of the voltage command is used for calculating the modulation degree Rm1 as the amplitude of the above-described sinusoidal voltage command. In the embodiment, the voltage command magnitude Vr and the modulation degree Rm1 are constantly calculated regardless of the control mode of the inverter 22.

  In the rectangular wave control mode, the ECU 50 first uses the electrical angle θe of the current sensor to convert the U-phase and V-phase currents Iu and Iv into the d-axis and q-axis currents Id and Iq, as in the PWM control mode. To coordinate conversion (3-phase-2 phase conversion). Subsequently, an output torque Tmest that is estimated to be output from the motor MG1 is set based on the d-axis and q-axis currents Id and Iq. Here, in the embodiment, the output torque Tmest is stored in a ROM (not shown) as an output torque estimation map in which the relationship between the d-axis and q-axis currents Id and Iq and the output torque Tmest is determined in advance through experiments and analysis. If the d-axis and q-axis currents Id and Iq are given, the corresponding output torque Tmest is derived and set from the stored map.

  The voltage phase command θs * (the angle of the vector of the voltage to be applied to the motor MG1 with respect to the q-axis direction (by the torque feedback control so that the difference between the estimated torque Tmest of the motor MG1 and the torque command Tm * is canceled) (Phase) command value) is calculated (and a rectangular wave signal based on the calculated voltage phase command θs * is applied to the motor 32, and a rectangular wave signal is output to the transistors T11 to T16 of the inverter 22 to thereby generate a transistor T11. -T16 is subjected to switching control.

  Control of the inverter 24 is performed in the same manner as the inverter 22. In the embodiment, regardless of the control mode of the inverter 24, the voltage command magnitude Vr and the modulation factor Rm2 set in the control of the inverter 24 are always calculated.

  Based on torque commands Tm1 * and Tm2 * of motors MG1 and MG2 and the rotational speeds Nm1 and Nm2 of motors MG1 and MG2, ECU 50 uses target voltage VH required to drive motors MG1 and MG2 by a method described later. * Is set, and the transistors T31 and T32 of the boost converter 34 are subjected to switching control so that the voltage VH of the high voltage system power line 40 becomes the target voltage VH *.

  In the embodiment, as described above, the magnitude Vr of the voltage command and the modulation degrees Rm1 and Rm2 are constantly calculated. When the inverter 22 is controlled in the PWM control mode, when the modulation degree Rm1 becomes the value Rref2 (about 0.78), the control mode of the inverter 22 is switched from the PWM control mode to the rectangular wave control mode. Further, when the inverter 22 is controlled in the rectangular wave control mode, when the modulation degree Rm1 becomes less than the value Rref2, the control mode of the inverter 22 is switched from the rectangular wave control mode to the PWM control mode. Similarly to the inverter 22, the inverter 24 switches the control mode according to the modulation degree Rm2.

  Next, the operation of the driving apparatus 20 of the embodiment configured as described above, particularly the operation when setting the target voltage VH * will be described. The target voltage VH * is set to the minimum loss voltage VHlmin of the high voltage system power line 40. Here, the minimum loss voltage VHlmin is the sum of the drive system loss Loss1 obtained by adding the loss of the inverter 22 to the loss of the motor MG1 and the drive system loss Loss2 obtained by adding the loss of the inverter 24 to the loss of the motor MG2. This is the voltage of the high voltage system power line 40. In the embodiment, the minimum loss voltage VHlmin is a loss map for each motor determined in advance as a relationship between the modulation degree Rm1 of the motor MG1 and the drive system loss Loss1, and a relationship between the modulation degree Rm2 of the motor MG2 and the drive system loss Loss2. Is set using.

  FIG. 2 is an explanatory diagram showing an example of the relationship between the degree of modulation Rm1 and the drive system loss Loss1 when the target drive point of the motor MG1 is a drive point. FIG. 3 is an explanatory diagram showing an example of the relationship between the modulation degree Rm2 and the drive system loss Loss2 when the target drive point of the motor MG2 is a drive point. The loss map can be determined using such a relationship for each target drive point of the motors MG1, MG2. As shown in FIGS. 2 and 3, the drive loss Loss1 and Loss2 change so as to draw a downward convex curve with respect to the modulation degrees Rm1 and Rm2, and the modulation degrees Rm1 and Rm2 have a value of 0.78. Sometimes it is minimal. 2 and 3, the voltage VH of the high voltage system power line 40 is changed with the voltage command magnitude Vr of the motors MG1 and MG2 constant, and the modulation degrees Rm1 and Rm2 are changed. The voltage VH when the sum of the drive system loss Loss1 and the drive system loss Loss2 derived from the loss map is minimized is defined as the minimum loss voltage VHlmin. When the temperatures of motors MG1 and MG2 change, the back electromotive voltages of motors MG1 and MG2 change. With respect to such a change in the back electromotive force, in the above-described loss map, the magnitudes of the drive system losses Loss1 and Loss2 change, but are minimum when the degree of modulation Rm1 and Rm2 is 0.78. The shape is maintained. Accordingly, the target voltage VH * is set to the minimum loss voltage VHlmin based on the modulation degrees Rm1, Rm2 and the loss map, and the transistor T31 of the boost converter 34 is set so that the voltage VH of the high voltage system power line 40 becomes the target voltage VH *. , T32 can be subjected to switching control, so that the loss of the entire drive system including the motors MG1, MG2 and the inverters 22, 24 can be reduced. Thereby, the voltage VH of the high voltage system electric power line 40 can be made into an appropriate voltage.

  According to the driving apparatus 20 of the embodiment described above, the motor MG1 has the relationship between the modulation degrees Rm1 and Rm2 of the motors MG1 and MG2 and the drive system loss obtained by adding the loss of the inverter driving the motor to the loss of the motor and the motor. , MG2 and a loss map determined for each driving point of the motors MG1 and MG2, and setting the target voltage VH * so that the sum of the driving system loss Loss1 and the driving system loss Loss2 is minimized. The voltage VH of the high voltage system power line 40 can be set appropriately.

  In the driving device 20 of the embodiment, the target voltage VH * is set using a loss map that is a relationship between the modulation degrees Rm1 and Rm2 and the drive system losses Loss1 and Loss2. The target voltage VH * may be set based on the slopes ΔLoss1, ΔLoss2 of the tangents of the curves in the loss map of the motors MG1, MG2.

  FIG. 4 is a control block diagram illustrating an example of processing for setting the target voltage VH * using the slope ΔLoss. The control block includes an FF term operation unit 110, a system control unit 112, a slope sum operation unit 114, an FB term operation unit 116, and an adder 118.

  The FF term calculation unit 110 receives the target driving points of the motors MG1 and MG2 (the torque commands Tm1 * and Tm2 * of the motor MG1 and the rotational speeds Nm1 and Nm2 of the motors MG1 and MG2), and the motors MG1 and MG2 at the target driving point. The feedforward term Vhff of the target voltage VH * is calculated and output so as to drive. The feedforward term Vhff is stored in a ROM (not shown) as a FF term setting map by predetermining the relationship between the target drive points of the motors MG1 and MG2 and the feedforward term Vhff of the high voltage system power line 40. , MG2 target drive points are given, the corresponding feedforward term Vhff is derived from the stored map and set.

  The system control unit 112 controls the boost converter 34 so that the voltage VH of the high voltage system power line 40 becomes a target voltage VH * input from an adder 118 described later, and the torque commands Tm1 * and Tm2 * described above. Inverters 22 and 24 are controlled so that motors MG1 and MG2 are driven. The system control unit 112 outputs the above-described modulation degrees Rm1 and Rm2.

  The slope sum calculation unit 114 receives the modulation degrees Rm1, Rm2 input from the system control unit 112, the target driving points of the motors MG1, MG2 (torque commands Tm1 *, Tm2 * and the rotational speeds Nm1, Nm2), and the loss map of each motor. From the above, the sum ΔLoss of the curve tangent slope ΔLoss1 in the motor MG1 loss map and the curve tangent slope ΔLoss2 in the motor MG2 loss map is calculated and output. FIG. 5 is an explanatory diagram showing an example of a tangent line in the relationship between the degree of modulation Rm1 and the loss Loss1 at a certain driving point of the motor MG1. FIG. 6 is an explanatory diagram showing an example of the relationship between the degree of modulation Rm1 and the tangential slope loss ΔLoss1 at a certain driving point of the motor MG1. As shown in FIG. 6, the slope ΔLoss1 of the loss map curve has a value of 0 at the minimum loss modulation factor Rmmin (value 0.78), and is a positive value when the modulation factor Rm1 is greater than 0.78. When the modulation degree Rm1 is smaller than 0.78, the value is negative. Although not shown, the slope ΔLoss2 of the tangent in the loss map of the motor MG2 is 0 when the minimum loss modulation factor Rmmin (value 0.78) is similar to the gradient ΔLoss1, and when the modulation factor Rm2 is greater than 0.78. A positive value is obtained, and a negative value is obtained when the degree of modulation Rm2 is smaller than 0.78. Therefore, the sum ΔLoss is 0 with the minimum loss modulation factor Rmmin (value 0.78).

  The FB term calculation unit 116 uses the sum ΔLoss input from the slope sum calculation unit 114 to obtain a feedback term Vhfb for feedback control of the voltage VH of the high voltage power line 40 so that the sum ΔLoss becomes 0. Calculated by the following equation (1) and output. In Expression (1), Kp is a proportional term gain, and Ki is an integral term gain.

  Vhfb = Kp / ΔLoss + Σ (Ki / ΔLoss) (1)

  The adder 118 outputs a value obtained by adding the feedback term Vhfb from the slope sum calculation unit 114 to the feedforward term Vhff from the FF term calculation unit 110 as the target voltage VH *. The target voltage VH * output in this way is input to the system control unit 112. The system control unit 112 controls the boost converter 34 so that the voltage VH of the high voltage system power line 40 becomes the target voltage VH *. Thus, by controlling the boost converter 34, the sum of the drive system loss Loss1 and the drive system loss Loss2 can be reduced. Thereby, the voltage VH of the high voltage system power line 40 can be set appropriately.

  In the embodiment, the present invention is applied to a drive device including two motors MG1 and MG2, but may be applied to a drive device including three or more motors.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the motors MG1 and MG2 correspond to “plural motors”, the inverters 22 and 24 correspond to “plural inverters”, the battery 30 corresponds to “battery”, and the boost converter 34 corresponds to “converter”. The ECU 50 corresponds to “control means”.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the column of means for solving the problem. Therefore, the elements of the invention described in the column of means for solving the problems are not limited. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description of the column, and the examples are those of the invention described in the column of means for solving the problems. It is only a specific example.

  As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention can be used in the manufacturing industry of drive devices.

  20 drive device, 22, 24 inverter, 30 battery, 34 boost converter, 40 high voltage system power line, 42, 46 capacitor, 42a, 46a voltage sensor, 44 low voltage system power line, 50 electronic control unit (ECU), 110 FF term computing unit, 112 system control unit, 114 slope sum computing unit, 116 FB term computing unit, 118 adder, D11-D16, D21-D26, D31, D32 diode, L reactor, MG1, MG2 motor, T11- T16, T21 to T26, T31, T32 transistors.

Claims (1)

Multiple motors,
A plurality of inverters for driving the plurality of motors;
Battery,
A converter connected to a first power line to which the plurality of inverters are connected and a second power line to which the battery is connected, and for converting a voltage between the first power line and the second power line;
Control means for controlling the plurality of inverters so that the plurality of motors are driven by a torque command set for each motor and controlling the converter so that the voltage of the first power line becomes a target voltage. ,
In a drive device comprising:
The control means has a relationship between a modulation degree based on the torque command and the voltage of the first power line, and a drive system loss obtained by adding a loss of the inverter that drives the motor to the modulation degree and the loss of the motor. Based on a predetermined relationship determined for each motor and for each driving point of the motor, the target voltage is set so that the sum of drive system losses of the plurality of motors is minimized.
Drive device.

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