Motor Control Device

Abstract

To enhance correction accuracy of an origin position of a rotation axis of a motor.SOLUTION: At the time of correction of an origin position of a rotation axis of a motor M, offset values Vo1 and Vo2 of amplitudes of AC voltages V1 and V2 from the origin position before correction to a predetermined rotation angle are calculated respectively based on the AC voltages V1 and V2 so that a medium value of each of the amplitudes of the AC voltages V1 and V2 may be coincide with a predetermined medium value, and a rotation angle calculated by AC voltages V1' and V2' whose amplitudes are offset by the offset values Vo1 and Vo2 when an operation of the motor M is controlled so that the rotation axis may be fixed at a predetermined position is made an origin position after correction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric motor control device that controls the operation of an electric motor. [Background technology]

[0002] There is a motor control device that calculates the rotation angle of the rotating shaft of the motor based on two-phase AC voltages with different phases output from a position detection unit such as a resolver attached to the motor, and controls the operation of the motor using the calculated rotation angle.

[0003] However, when the position detection unit is attached to the electric motor, if the position detection unit is not attached to a predetermined position on the electric motor, the origin position of the rotation angle calculated from the two-phase AC voltage will deviate from the origin position of the rotating shaft, reducing the accuracy of the calculation of the rotation angle, which may result in reduced efficiency of the electric motor or unstable operation of the electric motor.

[0004] In view of this, there is another motor control device that performs correction (calibration) of the origin position by setting the rotation angle calculated from the two-phase AC voltage output from a position detection unit when controlling the operation of the motor so that the rotating shaft is fixed at a predetermined position as the origin position (zero degrees) of the rotation angle calculated from the two-phase AC voltage.

[0005] However, when a two-phase AC voltage is obtained by multiple coils provided in the position detection unit, due to variations in the characteristics of each coil, the median amplitude of at least one of the two-phase AC voltages output from the position detection unit may differ from the median amplitude of the AC voltage that has been determined in advance by experiments, simulations, etc.

[0006] Therefore, in the other motor control devices described above, when the rotation angle of the rotating shaft is calculated using the correspondence between the predetermined two-phase AC voltages and the rotation angle of the rotating shaft, if the median value of the amplitude of at least one of the two-phase AC voltages output from the position detection unit differs from the median value of the amplitude of the AC voltages obtained in advance, there is a risk that the calculation accuracy of the rotation angle and the calculation accuracy of the origin position will decrease. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-81253 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object according to one aspect of the present invention is to improve the accuracy of correcting the origin position of the rotating shaft of an electric motor. [Means for solving the problem]

[0009] One embodiment of the motor control device according to the present invention includes a position detection unit that outputs two-phase AC voltages of different phases corresponding to a rotation angle of a rotating shaft of an electric motor, and a control unit that corrects an origin position of the rotation angle calculated from the two-phase AC voltages, and then controls operation of the electric motor using the rotation angle calculated from the two-phase AC voltages, with the corrected origin position set to zero degrees.

[0010] The control unit calculates offset values ​​for the amplitudes of each of the two-phase AC voltages based on the two-phase AC voltages from the origin position to a predetermined rotation angle before correction so that a median value of the amplitudes of each of the two-phase AC voltages coincides with a predetermined median value when correcting the origin position, and sets the rotation angle calculated by the two-phase AC voltages whose amplitudes have been offset by the offset values ​​as the origin position after correction when controlling the operation of the electric motor so that the rotating shaft is fixed at a predetermined position.

[0011] This makes it possible to improve the accuracy of correcting the origin position compared to a case in which the origin position is corrected using a two-phase AC voltage whose amplitude is not offset.

[0012] Furthermore, the control unit may be configured to set, when correcting the origin position, a rotation angle calculated using the two-phase AC voltages when controlling operation of the electric motor so that the rotating shaft is fixed at the predetermined position as a temporary origin position of the rotating shaft, calculate offset values ​​of the amplitudes of each of the two-phase AC voltages based on the two-phase AC voltages from the temporary origin position to the predetermined rotation angle so that a median value of the amplitudes of each of the two-phase AC voltages coincides with a predetermined median value, and set the rotation angle calculated using the two-phase AC voltages whose amplitudes have been offset by the offset values ​​as the corrected origin position when controlling operation of the electric motor so that the rotating shaft is fixed at the predetermined position.

[0013] This makes it possible to correct the origin position before calculating the offset value, thereby enabling the offset values ​​for the amplitudes of each of the two-phase AC voltages to be calculated with high accuracy, thereby further improving the accuracy of correcting the origin position.

[0014] The electric motor may be a motor provided in an air compressor that supplies oxidant gas to the fuel cell, and the control unit may be configured to correct the origin position when the fuel cell system is started up.

[0015] This allows the origin position to be corrected when the fuel cell system is started up before the fuel cell starts generating electricity, thereby preventing a decrease in the accuracy of the origin position correction when the fuel cell starts generating electricity.

[0016] The control unit may also be configured to: when the time required for diluting the fuel gas that has leaked from the anode side to the cathode side of the fuel cell with the oxidant gas is shorter than the time required for correcting the origin position, diluting the fuel gas and correcting the origin position simultaneously during the time required for correcting the origin position; and when the time required for diluting the fuel gas is longer than the time required for correcting the origin position, diluting the fuel gas and correcting the origin position simultaneously during the time required for diluting the fuel gas.

[0017] This allows dilution of the fuel gas and correction of the origin position to be performed simultaneously when the fuel cell system is started, thereby reducing the time required to start up the fuel cell system compared to when dilution of the fuel gas and correction of the origin position are performed sequentially. Effect of the Invention

[0018] According to the present invention, the accuracy of correcting the origin position of the rotating shaft of an electric motor is improved. [Brief description of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating an example of a fuel cell system including a motor control device according to an embodiment; [Diagram 2] 10 is a flowchart showing an example of an operation of a control unit when correcting an origin position. [Diagram 3] FIG. 2 is a diagram showing an example of a two-phase AC voltage. [Figure 4] 10 is a flowchart showing another example of the operation of the control unit when correcting the origin position. [Diagram 5] 5 is a flowchart showing an example of the operation of a control unit when the fuel cell system is started up. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0021] FIG. 1 is a diagram showing an example of a fuel cell system including a motor control device according to an embodiment.

[0022] The fuel cell system FCS shown in FIG. 1 includes a fuel cell FC, a DCDC converter CNV, a hydrogen tank HT, an injector INJ, an air compressor ACP, an inverter circuit INV, and a control unit CNT, and supplies power to an external load Lo.

[0023] When the fuel cell system FCS is mounted on a vehicle such as a forklift or an electric car, the load Lo is an inverter circuit for driving a travel motor, electrical equipment, or the like.

[0024] The fuel cell system FCS may also be configured as a stationary power generator.

[0025] A fuel cell FC is a fuel cell stack composed of multiple fuel cell units connected in series with each other, and generates electricity through an electrochemical reaction between hydrogen contained in a fuel gas (such as hydrogen gas) and oxygen contained in an oxidant gas (such as air).

[0026] The DC-DC converter CNV converts the voltage output from the fuel cell FC to a predetermined voltage. The power output from the DC-DC converter CNV is supplied to the load Lo, auxiliary devices such as the inverter circuit INV and the injector, and the power storage device B.

[0027] The power storage device B is composed of a capacitor or the like, and supplies power to the load Lo. That is, when the supply power corresponding to the difference between the power output from the DCDC converter CNV and the power supplied to the auxiliary equipment is greater than the required power requested from the outside of the fuel cell system FCS (for example, a driving control unit mounted on a vehicle), the required power of the supply power is supplied to the load Lo, and the remaining power is supplied to the power storage device B. When power is supplied from the DCDC converter CNV to the power storage device B, the power storage device B is charged and the charge amount of the power storage device B increases. Also, when the supply power corresponding to the difference between the power output from the DCDC converter CNV and the power supplied to the auxiliary equipment is smaller than the required power requested from the outside of the fuel cell system FCS, the supply power is supplied to the load Lo, and the insufficient power is supplied from the power storage device B to the load Lo. When power is supplied from the power storage device B to the load Lo, the power storage device B is discharged and the charge amount of the power storage device B decreases. The charge amount refers to the charge rate [%] of storage device B (the ratio of remaining capacity to the fully charged capacity of storage device B), or the open circuit voltage [V] of storage device B when no current is flowing to storage device B, or the closed circuit voltage [V] of storage device B when current is flowing to storage device B, or the integrated value [Ah] of current flowing to storage device B, etc.

[0028] The hydrogen tank HT is a storage container for fuel gas. The fuel gas stored in the hydrogen tank HT is supplied to the fuel cell FC via the injector INJ.

[0029] The injector INJ adjusts the flow rate of the fuel gas supplied to the fuel cell FC.

[0030] The air compressor ACP compresses the oxidant gas present around the fuel cell system FCS and supplies it to the fuel cell FC. The air compressor ACP also includes an electric motor M and a position detector R. The electric motor control device of the embodiment is configured to include the position detector R and the controller CNT.

[0031] The electric motor M is a motor including a stator, a rotor, etc., and compresses the oxidant gas by the power generated by the rotation of the rotor.

[0032] The position detection unit R outputs two-phase AC voltages V1 and V2 with different phases corresponding to the rotation angle of the rotating shaft of the electric motor M. For example, when the position detection unit R is configured using a resolver, a primary coil is provided on the rotor of the position detection unit R, and two secondary coils spaced 90 degrees apart are provided on the stator of the position detection unit R, and when an AC voltage is applied to the primary coil, two-phase AC voltages (sine wave, cosine wave) with phases different by 90 degrees are generated in each secondary coil, one of the AC voltages (sine wave) is AC voltage V1, and the other AC voltage (cosine wave) is AC voltage V2.

[0033] The inverter circuit INV drives the motor M with the power supplied from the DCDC converter CNV, and includes a capacitor C and switching elements SW1 to SW6 (for example, PNP bipolar transistors). That is, one terminal of the capacitor C is connected to the positive terminal of the DCDC converter CNV and the collector terminals of the switching elements SW1, SW3, and SW5, and the other terminal of the capacitor C is connected to the negative terminal of the DCDC converter CNV and the emitter terminals of the switching elements SW2, SW4, and SW6. The connection point between the emitter terminal of the switching element SW1 and the collector terminal of the switching element SW2 is connected to the U-phase input terminal of the motor M. The connection point between the emitter terminal of the switching element SW3 and the collector terminal of the switching element SW4 is connected to the V-phase input terminal of the motor M. The connection point between the emitter terminal of the switching element SW5 and the collector terminal of the switching element SW6 is connected to the W-phase input terminal of the motor M.

[0034] The capacitor C smoothes the voltage output from the DC-DC converter CNV and input to the inverter circuit INV.

[0035] The switching elements SW1 to SW6 are turned on or off based on the drive signals S1 to S6 output from the control unit CNT. By turning on or off the switching elements SW1 to SW6, respectively, the DC voltage output from the DC-DC converter CNV is converted into three AC voltages whose phases differ from each other by 120 degrees, and these AC voltages are applied to the input terminals of the U phase, V phase, and W phase of the electric motor M, causing the rotor of the electric motor M to rotate.

[0036] The control unit CNT is constituted by a microcomputer or the like, and changes the target generated power stepwise according to the charge amount of the power storage device B.

[0037] Furthermore, the control unit CNT controls the operation of the electric motor M (inverter circuit INV) and the injector INJ so that the power output from the fuel cell FC follows the target generated power.

[0038] Furthermore, during operation control of the electric motor M, the control unit CNT calculates the rotation angle of the rotating shaft of the electric motor M with reference to the origin position (zero degrees) for each control period, and calculates the drive signals S1 to S6 using the calculated rotation angle. For example, the control unit CNT refers to information indicating the correspondence between the AC voltages V1, V2 and the rotation angle obtained in advance through experiments, simulations, etc., and calculates the rotation angle corresponding to the offset AC voltages V1', V2' (described later) as the rotation angle of the rotating shaft.

[0039] Furthermore, the control unit CNT corrects (calibrates) the origin position at a predetermined timing.

[0040] FIG. 2 is a flowchart showing an example of the operation of the control unit CNT when correcting the origin position.

[0041] First, in step S11, as an offset value calculation process, the control unit CNT calculates an offset value Vo1 of the amplitude of the AC voltage V1 based on the AC voltage V1 from the origin position θ to a predetermined rotation angle before correction, and calculates an offset value Vo2 of the amplitude of the AC voltage V2 based on the AC voltage V2 from the origin position to a predetermined rotation angle before correction, so that the median values ​​of the amplitudes of the AC voltages V1 and V2 output from the position detection unit R match a predetermined median value.

[0042] For example, as shown in Fig. 3(a), assume that the amplitude of AC voltage V1 from the origin position (zero degrees) to 360 degrees before correction is shifted to the positive side by an offset value Vo1 from a predetermined median, and the amplitude of AC voltage V2 from the origin position θ (zero degrees) to 360 degrees before correction is shifted to the negative side by an offset value Vo2 from a predetermined median. Note that the above-mentioned predetermined median is the median of the amplitudes of AC voltages V1 and V2 obtained in advance by an experiment, a simulation, or the like.

[0043] In this case, the control unit CNT calculates the amplitude of the AC voltage V1 for each control period for the AC voltage V1 from the origin position θ (zero degrees) to 360 degrees, and subtracts a predetermined median value from the sum of all the calculated amplitudes divided by the number of times the amplitude is calculated (the number of times the control is performed), and sets the offset value Vo1 corresponding to the AC voltage V1. Similarly, the control unit CNT calculates the amplitude of the AC voltage V2 for each control period for the AC voltage V2 from the origin position (zero degrees) to 360 degrees, and subtracts a predetermined median value from the sum of all the calculated amplitudes divided by the number of times the amplitude is calculated (the number of times the control is performed), and sets the offset value Vo2 corresponding to the AC voltage V2. Note that if the median value of the AC voltage V1 output from the position detection unit R does not deviate from the predetermined median value, the offset value Vo1 becomes zero. Also, if the median value of the AC voltage V2 output from the position detection unit R does not deviate from the predetermined median value, the offset value Vo2 becomes zero. In addition, the offset values ​​Vo1 and Vo2 may be calculated multiple times until the fluctuation ranges of the offset values ​​Vo1 and Vo2 are within a predetermined range, and the average values ​​of the offset values ​​Vo1 and Vo2 calculated multiple times may be used as the offset values ​​Vo1 and Vo2 calculated in step S11.

[0044] Next, in step S12 of FIG. 2, the control unit CNT, as an origin position correction process, sets the rotation angle calculated by the AC voltages V1', V2' whose amplitudes are offset by the offset values ​​Vo1, Vo2 calculated in step S11 when controlling the operation of the motor M so that the rotating shaft is fixed at a predetermined position as the origin position θ' (zero degrees) after correction. For example, when the control unit CNT fixes the rotating shaft at a predetermined position by outputting the drive signals S1 to S6 that turn on the switching elements SW1, SW4, SW6 and turn off the switching elements SW2, SW3, SW5, as shown in FIG. 3(b), the rotation angle corresponding to the AC voltages V1', V2' whose amplitudes are offset by the offset values ​​Vo1, Vo2 is set as the origin position θ' (zero degrees) after correction. Note that the value obtained by subtracting the offset value Vo1 from the AC voltage V1 is set as the AC voltage V1', and the value obtained by subtracting the offset value Vo2 from the AC voltage V2 is set as the AC voltage V2'.

[0045] As a result, even if the median value of the amplitude of at least one of the AC voltages V1, V2 output from the position detection unit R differs from the median value of the amplitude of the AC voltage previously obtained by an experiment, a simulation, or the like due to variations in the characteristics of the multiple coils provided in the position detection unit R, the median value of the amplitude of each of the AC voltages V1, V2 output from the position detection unit R can be made to match the median value of the amplitude of the AC voltage previously obtained by offsetting the AC voltages V1, V2 with the offset values ​​Vo1, Vo2. Therefore, since the offset AC voltages V1', V2' can be made to approach the previously obtained AC voltages V1, V2, when the rotation angle (zero degrees to 360 degrees) corresponding to the AC voltages V1', V2' is calculated with reference to information indicating the correspondence between the previously obtained AC voltages V1, V2 and the rotation angle, the calculation accuracy of the rotation angle can be improved.

[0046] In this way, the control unit CNT that performs the operation shown in Fig. 2 calculates offset values ​​Vo1 and Vo2 based on the AC voltages V1 and V2 from the origin position to a predetermined rotation angle so that the median value of each amplitude of the AC voltages V1 and V2 coincides with a predetermined median value when correcting the origin position, and then sets the rotation angle calculated by the AC voltages V1' and V2' whose amplitudes are offset by the offset values ​​Vo1 and Vo2 when controlling the operation of the electric motor M so that the rotating shaft is fixed at a predetermined position as the origin position after correction. That is, the control unit CNT that performs the operation shown in Fig. 2 calculates the offset values ​​Vo1 and Vo2 before correcting the origin position, and corrects the origin position using the AC voltages V1' and V2' whose amplitudes are offset by the calculated offset values ​​Vo1 and Vo2.

[0047] This allows the origin position calculated using the offset AC voltages V1', V2' to be closer to the origin position of the information referenced for calculating the rotation angle during operational control of the electric motor M, improving the accuracy of correcting the origin position compared to correcting the origin position using AC voltages V1, V2 whose amplitudes are not offset. This makes it possible to suppress a decrease in the calculation accuracy of the rotation angle of the rotating shaft, and to suppress a decrease in the efficiency of the electric motor M and an unstable operation of the electric motor M.

[0048] FIG. 4 is a flowchart showing another example of the operation of the control unit CNT when correcting the origin position.

[0049] First, in step S21, the control unit CNT sets the rotation angle corresponding to the AC voltages V1 and V2 as a temporary origin position (zero degrees) while controlling the operation of the electric motor M so that the rotating shaft is fixed at a predetermined position as a first origin position correction process.

[0050] For example, when the control unit CNT fixes the rotating shaft at a predetermined position by outputting drive signals S1 to S6 that turn on switching elements SW1, SW4, and SW6 and turn off switching elements SW2, SW3, and SW5, the rotation angle corresponding to the AC voltages V1 and V2 output from the position detection unit R is set as the temporary origin position.

[0051] Next, in step S22, as an offset value calculation process, the control unit CNT calculates an offset value Vo1 of the amplitude of the AC voltage V1 based on the AC voltage V1 from the temporary origin position corrected in step S21 to a predetermined rotation angle so that the median values ​​of the amplitudes of the AC voltages V1 and V2 output from the position detection unit R match a predetermined median value, and calculates an offset value Vo2 of the amplitude of the AC voltage V2 based on the AC voltage V2 from the temporary origin position corrected in step S21 to a predetermined rotation angle.

[0052] Then, in step S23, the control unit CNT sets the rotation angle calculated from the AC voltages V1 and V2 whose amplitudes are offset by the offset values ​​Vo1 and Vo2 calculated in step S22 while controlling the operation of the electric motor M so that the rotating shaft is fixed at a predetermined position as the corrected origin position (zero degrees) as the second origin position correction process.

[0053] In this way, the control unit CNT that performs the operation shown in Fig. 4 sets the rotation angle calculated by the AC voltages V1 and V2 when controlling the operation of the motor M so that the rotating shaft is fixed at a predetermined position as the temporary origin position of the rotating shaft, calculates offset values ​​Vo1 and Vo2 based on the AC voltages V1 and V2 from the temporary origin position to a predetermined rotation angle so that the median value of each of the amplitudes of the AC voltages V1 and V2 coincides with a predetermined median value, and sets the rotation angle calculated by the AC voltages V1 and V2 whose amplitudes are offset by the offset values ​​Vo1 and Vo2 when controlling the operation of the motor M so that the rotating shaft is fixed at a predetermined position as the corrected origin position. That is, the control unit CNT that performs the operation shown in Fig. 4 corrects the origin position before calculating the offset values ​​Vo1 and Vo2.

[0054] In this way, since the origin position is corrected before calculating the offset values ​​Vo1 and Vo2, the offset values ​​Vo1 and Vo2 can be calculated with high accuracy, and the origin position correction accuracy can be further improved. Therefore, a decrease in the calculation accuracy of the rotation angle of the rotating shaft can be further suppressed, and a decrease in the efficiency of the electric motor M and an unstable operation of the electric motor M can be further suppressed.

[0055] Furthermore, the control unit CNT executes various processes required for the fuel cell FC to generate power when the fuel cell system FCS is started. For example, the control unit CNT corrects the origin position when the fuel cell system FCS is started, as shown in FIG. 2 or FIG. 4. This allows the origin position to be corrected when the fuel cell system FCS is started, prior to the power generation of the fuel cell FC, and therefore reduces the accuracy of the origin position correction when the fuel cell FC generates power. This makes it possible to prevent the efficiency of the electric motor M from decreasing and the operation of the electric motor M from becoming unstable when the fuel cell FC generates power.

[0056] FIG. 5 is a flowchart showing an example of the operation of the control unit CNT when the fuel cell system FCS is started up.

[0057] First, in step S31, the control unit CNT judges whether or not to start up the fuel cell system FCS. For example, when the control unit CNT receives a notification from the vehicle's traveling control unit that the ignition key of the vehicle is turned on, or when a predetermined time has elapsed since the control unit CNT shifted from the power generation control mode to the sleep mode, the control unit CNT judges to start up the fuel cell system FCS.

[0058] Next, when the control unit CNT starts the fuel cell system FCS (step S31: Yes), it calculates the time T1 required to dilute the fuel gas leaked from the anode side to the cathode side in the fuel cell FC with the oxidant gas (step S32). Note that the longer the power generation stop time from the previous power generation stop of the fuel cell FC to the current start of the fuel cell system FCS, the longer the time required to dilute the fuel gas. For example, the control unit CNT refers to information indicating the correspondence between the power generation stop time and the time T1 stored in a storage unit (not shown), and sets the time T1 corresponding to the power generation stop time acquired this time as the time T1 calculated in step S32. Also, steps S32 and S33 may be interchanged.

[0059] Next, the control unit CNT acquires a time T2 required for correcting the origin position (step S33). For example, the control unit CNT sets the time T2 acquired in step S33 to the time T2 previously obtained by an experiment or a simulation and stored in a storage unit (not shown).

[0060] Next, if the time T1 is shorter than the time T2 (step S34: Yes), the control unit CNT simultaneously dilutes the fuel gas and corrects the origin position at the time T2 (step S35).

[0061] On the other hand, if the time T1 is longer than the time T2 (step S34: No), the control unit CNT simultaneously dilutes the fuel gas and corrects the origin position at the time T1 (step S36).

[0062] Thus, in the fuel cell system FCS of the embodiment, when the fuel cell system FCS is started, if the time T1 required to dilute the fuel gas is shorter than the time T2 required to correct the origin position, then during the time T2 required to correct the origin position, dilution of the fuel gas and correction of the origin position are performed simultaneously, and if the time T1 required to dilute the fuel gas is longer than the time T2 required to correct the origin position, then dilution of the fuel gas and correction of the origin position are performed simultaneously during the time T1 required to dilute the fuel gas.

[0063] This allows fuel gas dilution and origin position correction to be performed simultaneously when starting up the fuel cell system FCS, thereby reducing the time required to start up the fuel cell system FCS compared to when fuel gas dilution and origin position correction are performed sequentially.

[0064] The present invention is not limited to the above-described embodiment, and various improvements and modifications are possible without departing from the gist of the present invention.

[0065] <Modification> In the above embodiment, the power generation control of the fuel cell FC and the operation control of the electric motor M (inverter circuit INV) are collectively performed by the control unit CNT, but the power generation control of the fuel cell FC and the operation control of the electric motor M may be performed by separate control units. In such a configuration, the control unit that controls the operation of the electric motor M performs the operation shown in Fig. 2 or 4. The control unit that controls the operation of the electric motor M performs the operation shown in Fig. 5, and also receives a start-up request for the fuel cell system FCS and a time T1 required to dilute the fuel gas from the control unit that controls the power generation of the fuel cell FC. [Explanation of symbols]

[0066] FCS Fuel Cell System CNT control section INV Inverter circuit C Capacitor SW1~SW6 Switching elements FC fuel cell HT Hydrogen Tank INJ Injector ACP Air Compressor M electric motor R Position detection section CNV DC / DC Converter B Energy storage device Lo load

Claims

1. a position detection unit that outputs two-phase AC voltages having different phases from each other, the two-phase voltages corresponding to a rotation angle of a rotary shaft of the electric motor; a control unit that corrects an origin position of the rotation angle calculated based on the two-phase AC voltage, and then controls an operation of the electric motor using the rotation angle calculated based on the two-phase AC voltage with the origin position after correction set to zero degrees; Equipped with When correcting the origin position, the control unit calculating an offset value of the amplitude of each of the two-phase AC voltages based on the two-phase AC voltages from the origin position to a predetermined rotation angle before correction such that a median value of the amplitude of each of the two-phase AC voltages coincides with a predetermined median value; a rotation angle calculated based on the two-phase AC voltage whose amplitude is offset by each of the offset values ​​when the operation of the electric motor is controlled so that the rotation shaft is fixed at a predetermined position is set as the corrected origin position; the electric motor is a motor provided in an air compressor that supplies an oxidant gas to a fuel cell, The control unit, when starting up the fuel cell system, when a time required for diluting the fuel gas leaked from the anode side to the cathode side of the fuel cell with the oxidant gas is shorter than a time required for correcting the origin position, diluting the fuel gas and correcting the origin position are performed simultaneously during the time required for correcting the origin position; When the time required for diluting the fuel gas is longer than the time required for correcting the origin position, the dilution of the fuel gas and the correction of the origin position are performed simultaneously during the time required for diluting the fuel gas. An electric motor control device comprising:

2. 2. The motor control device according to claim 1, When correcting the origin position, the control unit a rotation angle calculated based on the two-phase AC voltage when controlling the operation of the electric motor so that the rotation shaft is fixed at the predetermined position is set as a temporary origin position of the rotation shaft; calculating an offset value of the amplitude of each of the two-phase AC voltages based on the two-phase AC voltages from the temporary origin position to the predetermined rotation angle such that a median value of the amplitude of each of the two-phase AC voltages coincides with a predetermined median value; When the operation of the electric motor is controlled so that the rotating shaft is fixed at the predetermined position, the rotation angle calculated from the two-phase AC voltage whose amplitude is offset by each offset value is set as the corrected origin position. An electric motor control device comprising:

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