JP2001037284A - Method and apparatus for measuring electrical angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance measurement accuracy of electric angle of an electrical motor while shortening the measuring time. SOLUTION: A pulse voltage is applied to the coil of an electric motor and variation of current induced in the coil is measured. The measured variation of current is compensated based on the applied pulse voltage in order to estimate variation of current (reference variation of current) being induced upon application of a reference pulse voltage and then the electrical angle is determined based on the estimated reference variation of current. Even if the level of applied pulse voltage is varied, it is compensated and the electrical angle can be measured accurately. Since a process for generating a reference pulse voltage is eliminated, measuring time of the electrical angle can be shortened correspondingly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring an electric angle which is a rotation angle of a rotor in an electric motor.

[0002]

2. Description of the Related Art Electric motors are widely used as power sources for industrial machines, transportation equipment, home electric appliances and the like.
In recent years, AC motors have also been widely used as these power sources. AC motors have the advantages of simple structure, high reliability and easy maintenance, but they have the disadvantage that it is difficult to control the rotation speed and generated torque with high accuracy. These drawbacks have been overcome and are now widely used as reliable power sources. Also, with the advance of semiconductor technology, a so-called brushless DC motor that does not use a commutator and a brush has been put into practical use and is widely used as a power source.

[0003] A general configuration of these electric motors is, for example, a rotor having a permanent magnet attached thereto and a stator having a multi-phase coil wound in a Y-connection or a delta connection.
It is driven via an inverter that switches the voltage applied to each phase coil. Such an electric motor detects an electrical rotation position (electrical angle) of a rotor of the motor, and generates a rotating magnetic field by sequentially switching voltages applied to the respective phase coils according to the electrical angle. Torque is generated by an electromagnetic interaction between the rotor and the rotor. Although the electrical angle can be detected using a Hall element, a so-called sensorless method of calculating the electrical angle without using a dedicated sensor such as a Hall element has been proposed (for example, Japanese Patent Application Laid-Open No. 177788). If the electrical angle is detected by a sensorless method, there is an advantage that the reliability against a failure is increased by the amount of no use of the sensor, and the durability of the electric motor is further improved.

The outline of the principle of measuring the electrical angle by a typical sensorless method is as follows. When a step-like voltage is applied to the coil of the electric motor, a current that changes with time is generated in the coil, and this change in current is
It is determined by the applied voltage value and the impedance and inductance on the coil side. Here, in an electric motor, it is known that a certain correspondence is established between the inductance and the electrical angle. Therefore, the amount of change in the current is analyzed to determine the inductance of each phase coil, and the electrical angle is calculated from the inductance using the correspondence between the inductance and the electrical angle.

[0005] In order to operate the electric motor at a desired rotational speed and generated torque, it is necessary to switch the voltage applied to each coil one after another according to the detected electrical angle. For this reason, the electrical angle needs to be calculated accurately and quickly.

For these reasons, in the conventional sensorless system, the electrical angle is calculated by the following method. First, one reference pulse voltage having a predetermined voltage value and a time width is determined, and this reference pulse voltage is always applied to the coil. The value of the current generated in the coil is measured when a predetermined time has elapsed after the application of the pulse. If the pulse voltage value to be applied and the measurement timing are kept constant in this way, the difference in the measured current value will be the difference in inductance, so refer to the correspondence table between the current value and the inductance determined in advance. Accordingly, the electrical angle can be calculated quickly and accurately. As a reference pulse voltage to be applied, an accurate reference pulse voltage is generated by detecting a voltage value supplied from a power supply and stepping down the power supply voltage at a predetermined ratio using a known method such as PWM control.

[0007]

However, in the conventional sensorless system, a pulse having an accurate voltage value cannot be generated when the power supply voltage decreases, and the electrical angle detection accuracy in such a case decreases. There is a problem.

Further, since a time for calculating the electrical angle is required, there is a problem that it is difficult to further increase the rotation speed of the motor and to increase the accuracy of the control.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to accurately measure an electrical angle without a sensor even when a power supply voltage is reduced, and to further reduce the time required for electrical angle measurement. The purpose is to provide a technology that can.

[0010]

Means for Solving the Problems and Their Functions and Effects In order to solve at least a part of the above problems, the electric angle measuring device of the present invention has the following configuration. That is, an electric angle measuring device for measuring an electric angle between a rotor and a stator of an electric motor, wherein a pulse voltage applying means for applying a pulse voltage to a coil of the electric motor; Actual current change amount measuring means for measuring the amount of the current change that has occurred, and a reference current corresponding to the application of the pulse voltage of the reference voltage value, the current change amount being compensated based on the voltage value of the applied pulse voltage. The gist is to include reference current change amount estimating means for estimating the change amount, and electric angle determining means for determining the electric angle based on the estimated reference current change amount.

An electric angle measuring method of the present invention corresponding to the electric angle measuring device described above is an electric angle measuring method for measuring an electric angle between a rotor and a stator of an electric motor, A pulse of a reference voltage value is applied by applying a pulse voltage to a coil of a motor, measuring a current change amount generated in the coil by applying the pulse voltage, and compensating the current change amount based on the applied pulse voltage. The gist is to estimate a reference current change amount corresponding to the application of the voltage, and to measure the electrical angle based on the estimated reference current change amount.

In the electric angle measuring device and the electric angle measuring method, the pulse voltage of the reference voltage value is obtained from the voltage value of the pulse voltage applied to the coil of the electric motor and the amount of current change caused by the application of the pulse voltage. A reference current change amount caused by the application is estimated, and an electrical angle is measured based on the estimated reference current change amount. Therefore, since it is not necessary to generate a pulse of the reference voltage, the electrical angle can be measured quickly as much as the trouble can be saved. In addition, since the reference current change amount can be estimated even when a pulse voltage having a voltage value different from the reference voltage value is applied, the electrical angle can be accurately detected even under conditions where it is difficult to generate the reference voltage. Can be.

In this electrical angle measuring device, the correspondence between the value of the pulse voltage applied to the coil and the amount of compensation for converting the measured current change into the reference current change is stored in advance. The reference current change amount may be estimated from the measured current change amount based on this correspondence.

As described above, if the amount of compensation for the amount of change in the current is obtained based on the correspondence stored in advance, the amount of change in the reference current can be accurately estimated from the amount of change in the measured current. It is preferable that the electrical angle can be accurately measured.

In this electric angle measuring device, a pulse voltage having a voltage value that increases and decreases with the DC voltage supplied from the power supply is applied, and the value of the DC voltage supplied from the power supply is measured, thereby obtaining the coil. May be determined.

This makes it possible to accurately determine the applied pulse voltage. Therefore, it is preferable because the electrical angle measurement accuracy is improved. Further, since the DC voltage value supplied from the power supply can be measured relatively easily, the applied pulse voltage can be easily obtained. This is preferable because the electrical angle can be easily measured.

Further, the electric angle measuring device may be an electric angle detecting device for measuring an electric angle of a synchronous motor. Since the control of the synchronous motor is performed based on the electrical angle of the rotor, it is preferable to measure the electrical angle using the electrical angle measuring device of the present invention, since the synchronous motor can be quickly and accurately controlled. .

The electrical angle measuring device described above may measure the electrical angle as follows. A DC voltage value supplied from a power supply is measured, and when the DC voltage value is equal to or more than a predetermined value, a pulse voltage having a reference voltage value is applied, and a reference current change amount generated by the pulse voltage is measured. When the DC voltage value is equal to or less than a predetermined value, a pulse voltage having a voltage value proportional to the DC voltage value is applied to measure a current change amount generated in the coil, and the voltage value of the applied pulse voltage and the measured current are measured. The reference current change amount is estimated based on the change amount. In this way, when the power supply supplies a DC voltage with a sufficient voltage value, the reference current change amount is measured, and when the power supply does not supply a DC voltage with a sufficient voltage value, the reference current change amount is estimated. The electrical angle may be obtained based on the measured reference current change amount or the estimated reference current change amount.

It is preferable to measure the electrical angle in this manner because the electrical angle can be accurately measured irrespective of the value of the DC voltage supplied from the power supply.

In this electric angle measuring device, when the DC voltage value supplied by the power supply is larger than the reference voltage value,
When a pulse voltage having a reference voltage value is applied and the DC voltage value is smaller than the reference voltage value, a pulse voltage having a voltage equal to the DC voltage value may be applied.

In this way, when the value of the DC voltage supplied from the power supply is low, the supplied DC voltage is applied to the coil without stepping down. If the DC voltage is stepped down and then applied to the coil, the amount of change in current generated in the coil will also be small, but if the voltage is applied without stepping down, the detection accuracy will be improved by the amount of the large amount of change in current This is preferable because it also makes it possible to improve the measurement accuracy of the electrical angle.

The present invention can be embodied as a control device or a control method for controlling an electric motor using the above-described electric angle measuring device. That is, the electric motor control device of the present invention is an electric motor control device that measures an electric angle between a rotor and a stator of the electric motor and controls the electric motor based on the measured electric angle. Pulse voltage applying means for applying a pulse voltage to the coil of the electric motor, actual current change amount measuring means for measuring the current change amount generated in the coil by the pulse voltage, and a voltage of the applied pulse voltage. The reference current change amount estimating means for compensating the current change amount based on the value, and estimating the reference current change amount corresponding to the application of the pulse voltage of the reference voltage value, based on the estimated reference current change amount. The gist of the present invention is to include an electrical angle determining means for determining an electrical angle and a current control means for controlling a current supplied to the coil based on the determined electrical angle.

Further, the electric motor control method of the present invention corresponding to the electric motor control device described above measures an electric angle between a rotor and a stator of the electric motor, and based on the measured electric angle. Controlling the electric motor by applying a pulse voltage to a coil of the electric motor, measuring a current change amount generated in the coil by applying the pulse voltage, and based on the applied pulse voltage, By compensating the current change amount, the reference current change amount corresponding to the application of the pulse voltage of the reference voltage value is estimated, and the electrical angle is determined based on the estimated reference current change amount, and the determined electrical angle is determined. The gist of the present invention is to control the current supplied to the coil based on the electrical angle.

In the electric motor control device and the electric motor control method, the reference current change amount is estimated based on the voltage value of the pulse voltage applied to the coil, and the electric angle is measured based on the estimated reference current change amount. Then, the electric motor is controlled. Therefore, the electrical angle can be measured quickly and accurately. For this reason, it is preferable because the rotation speed of the electric motor can be further increased or the control accuracy can be increased.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, embodiments of the present invention will be described below based on examples.

A. Device Configuration: (1) Outline of Motor Control: FIG. 1 is a functional block diagram showing a schematic configuration of a motor control device 10 including an electric angle detection device as one embodiment of the present invention. Motor control device 1
In order to explain the outline of the role of the electrical angle detecting device of the present embodiment at 0, first, the outline of the control of the rotation of the motor by the motor control device 10 of FIG. 1 will be briefly described.

The motor control device 10 illustrated in FIG. 1 includes a three-phase synchronous motor 60 and an inverter 30 that functions to switch the current flowing through each phase coil of the three-phase synchronous motor 60.
A power supply 80 for supplying power to the inverter 30; a control unit 20 for controlling the inverter 30; an electric angle detection unit 40 for detecting an electric angle of the synchronous motor 60;
And the like.

The three-phase synchronous motor 60 has a structure in which three coils are arranged around a rotor made of a permanent magnet, and can be considered by electrically replacing each coil with an equivalent circuit in which the coils are Y-connected. . Assuming that the u-phase terminal connected to the U-phase coil is connected to the minus terminal of the power supply, the v-phase terminal connected to the V-phase coil and the w-phase terminal connected to the W-phase coil are connected to the positive terminal. When connected, a magnetic field in the direction shown in FIG. 1 is formed in each coil. At the center position of the three coils, the magnetic fields of the respective coils are combined to form a magnetic field that goes up and down on the paper. Next, the u-phase terminal and the w-phase terminal are connected to the minus terminal, and the v-phase terminal is connected to the plus terminal. Then, the directions of the magnetic fields of the U-phase coil and the V-phase coil are reversed, and as a result, the direction of the magnetic field at the center position of the three-phase coil rotates clockwise by 60 degrees on the paper. Then, connect the u-phase terminal and the v-phase terminal to the minus terminal, and
When the phase terminal is connected to the plus terminal, the direction of the magnetic field rotates further 60 degrees clockwise. By sequentially switching the voltages applied to the terminals of the u, v, and w phases, a rotating magnetic field can be applied to the rotor located at the center position of the three-phase coil. If a permanent magnet is attached to the rotor, the rotor rotates with the movement of the magnetic field.

The above is the basic operation principle of the synchronous motor, and the inverter 30 has a function of switching the voltage applied to the terminal of each phase coil one after another. Control unit 2
0 controls the inverter 30. Electrical angle detector 40
The torque detector 50 detects the electrical angle and the generated torque of the motor from the current values of the coils of the respective phases detected by the current detectors 12 and 14, and outputs them to the controller 20. The control unit 20 controls the switching timing of the voltage applied to each phase coil based on the electric angle received from the electric angle detection unit 40, and controls the generated torque received from the torque detection unit 50 to match the torque command value. The feedback control of the generated torque is performed.

In the control of the synchronous motor, it is necessary to smoothly switch the voltage applied to each phase coil together with the rotation of the rotor.
It detects the electrical rotation position (electric angle) of the motor and supplies it to the control unit.

(2) Outline of Electric Angle Detecting Device: FIG. 2 is an explanatory diagram showing an outline of a hardware configuration of the motor control device 10 described above. The motor control device 10 is a device that drives the three-phase synchronous motor 60, and is an electronic control unit (hereinafter, referred to as an ECU) 20 that performs various calculations for performing control.
0, a power supply 80 for supplying electric power, an inverter 30 for switching a voltage applied to the three-phase synchronous motor 60 under the control of the ECU 200, current detectors 12 and 14 for detecting a current flowing in a coil of the motor, Filters 102 and 104 for removing unnecessary frequency components from the obtained current, an analog-to-digital converter (hereinafter referred to as ADC) for converting the current value after the filtering into digital data, and the like.

The ECU 200 includes a CPU 202 and a ROM
204, a RAM 206, an input port 208 for receiving data from the outside, an output port 210 for outputting data to the outside, and the like, and is configured as a well-known arithmetic and logic operation circuit. And it is possible to exchange data.

The inverter 30 of the present embodiment is a so-called power transistor type inverter composed of a power control semiconductor such as a power transistor and a diode. Of course, another type of inverter using a thyristor or the like can be applied. The voltage applied to the three terminals of the three-phase synchronous motor 60 is switched at appropriate timing by controlling the switching operation of the transistor based on the control signal from the ECU 200.

The current detectors 12 and 14 detect the current flowing through the U-phase coil and the V-phase coil of the motor, respectively, by utilizing the electromagnetic induction. The detected current is used for detecting an electrical angle (details will be described later), detecting a torque generated by the motor (described later), and the like. The current flowing through each phase coil of the motor fluctuates with time. Frequency components within a predetermined range of the fluctuating current are extracted and used for detecting an electrical angle and torque. The filters 102 and 104 are the current detector 1
It is provided in order to remove unnecessary frequency components from the currents detected in 2 and 14. ADCs 106 and 108
The analog outputs of the filters 102 and 104 are converted into digital data that can be handled by a computer. A
Outputs of DCs 106 and 108 are taken into ECU 200 via input port 208. A power supply 80 for supplying power to the motor control device 10 shown in FIG. 2 uses a DC power supply to which a plurality of batteries are connected. Of course, the present invention is not limited to this. For example, a converter that generates a DC voltage from a commercial AC power supply may be used, or a power supply device that generates a DC voltage using a fuel cell may be used.

In this embodiment, the electric angle is detected by the ECU 200 used for motor control, the inverter 30, the current detectors 12, 14, the filters 102, 104, the ADC 1
This is performed using the functions 06 and 108. That is, the electrical angle detection device 100 of the present embodiment is
It exists in a form that is included in.

(3) Outline of structure of synchronous motor: FIGS. 3 and 4 show a three-phase synchronous motor 60 used in this embodiment.
FIG. 3 is an explanatory diagram showing an outline of the structure. FIG. 3 is a cross-sectional view in a cross section including the rotation axis of the motor, and FIG. 4 is a cross-sectional view in a cross section orthogonal to the rotation axis. As shown in FIG. 3, the three-phase synchronous motor 60 includes a stator 61, a rotor 62, and a case 63 accommodating them. Rotor 62
Are provided with permanent magnets 64a to 64d affixed to the outer periphery, and the rotating shaft 65 is mounted on a bearing 66 provided on the case 63.
a, 66b rotatably held.

The rotor 62 is formed by laminating a plurality of plate-shaped rotors 67 formed by stamping out electromagnetic steel sheets. As shown in FIG. 4, the plate-shaped rotor 67 has four salient poles 68a to 68d at orthogonal positions. Permanent magnets 64a to 64d are affixed to the outer peripheral surface of the rotor 62 at intermediate positions between the salient poles 68a to 68d along the rotation axis direction. The permanent magnets 64a to 64d are magnetized in the radial direction of the rotor 62, and the polarity of adjacent magnets is different from each other. For example,
The outer peripheral surface of the permanent magnet 64a has an N pole, and the outer peripheral surface of the adjacent permanent magnet 64b has an S pole. This permanent magnet 6
4a and 64b form a magnetic path Md penetrating the plate-shaped rotor 67 and the plate-shaped stator 69 when assembled to the rotor 62 (see FIG. 4).

The stator 61 is formed by laminating plate-like stators 69 formed by punching a thin sheet of electromagnetic steel sheet.
The plate-shaped rotator 67 includes twelve teeth 70 as shown in FIG. A coil 72 for generating a rotating magnetic field in the stator 61 is wound around a slot 71 formed between the teeth 70. In addition, a bolt hole through which the fixing bolt 73 is passed is provided on the outer edge of the plate-shaped stator 69, but is not shown in FIG.

The stator 61 is assembled to the case 63, a fixing bolt 73 is passed through a bolt hole, and the whole is fixed by tightening the bolt. The three-phase synchronous motor 60 is completed by rotatably assembling the rotor 62 with the bearings 66a and 66b in the stator 61 thus formed.

When a current is applied to the coil 72 of the stator 61,
As shown in FIG. 4, the adjacent salient poles and plate rotor 67
A magnetic path Mq penetrating through the plate-shaped stator 69 is formed. still,
An axis through which the magnetic flux formed by the above-described permanent magnet 64a passes through the rotor 62 in the radial direction through the center of the rotation axis thereof is referred to as a d-axis, and is electrically orthogonal to the d-axis in the rotation plane of the rotor 62. The axis used is called the q-axis. That is, the d axis and the q axis are axes that rotate with the rotation of the rotor 62. In the three-phase synchronous motor 60 of the present embodiment, the outer peripheral surfaces of the permanent magnets 64a and 64c attached to the rotor 62 have N poles, and the outer peripheral surfaces of the permanent magnets 64b and 64d have S poles. As shown in FIG. 4,
Geometrically, the axis in the direction of 45 degrees from the d axis is the q axis.

B. Outline of Motor Control Process: FIG. 5 is a flowchart showing a flow of a process in which the motor control device 10 of the present embodiment controls the operation of the three-phase synchronous motor 60.
The electric angle detection process is performed by the CPU 202 in the ECU 200 as a part of the motor control process shown in FIG. As a preparation for describing the detection of the electrical angle, an outline of the motor control process will be described below with reference to the flowchart of FIG.

When the motor control process is started, the CPU 202 first performs an electrical angle detection process (step S10).
0). As described above, in the control of the three-phase synchronous motor 60, the motor is operated while sequentially switching the voltage applied to each terminal of the U, V, and W phases in accordance with the rotation of the rotor 62. First, an electrical angle, which is a basic variable of the process, is detected. Details of the electrical angle detection processing will be described later.

When the electric angle is detected, the CPU 202 determines the direction of the rotating magnetic field formed in the stator 61 from the detected electric angle, and determines the direction of the rotating magnetic field to be formed in the determined direction.
The voltage state of each terminal of the V and W phases, that is, whether to connect to the high voltage side or the low voltage side of the voltage supplied from the power supply 80 is determined. This processing is the terminal voltage determination processing (step S102).

When the terminal voltage determination processing is completed, the CPU 2
02 starts the torque control process (step S10).
4). Since the torque generated by the motor is proportional to the current flowing through the coil of each phase, the torque generated by the motor can be detected by detecting the current flowing through the coil of each phase by the current detectors 12 and 14. The generated torque is compared with the torque command value. If the generated torque is small, the current flowing through the coil is increased, and if the generated torque is small, the current is decreased. Thus, the process of controlling the torque generated by the motor so as to match the torque command value is the torque control process (step S104). In this embodiment, the so-called PWM
By performing the control, the value of the current flowing through the coil is controlled. Note that there is a relationship that the sum of the current values flowing through the coils of each phase always becomes zero. Therefore, in the present embodiment, the currents Iu and Iv flowing through the two coils of the U-phase coil and the V-phase coil
And the current Iw flowing through the W-phase coil is obtained by calculation using this relationship. Of course, three current detectors may be provided to directly detect the current flowing in the U, V, and W phase coils.

Since the rotor 62 is continuously rotating,
When the torque control process S104 ends, the process returns to step S104.
Returning to the process at 100, the electrical angle is detected, and a series of subsequent processes are repeated based on the newly detected electrical angle. That is, the motor control device 10 used in the present embodiment constantly executes the motor control process shown in FIG. 5 as a main routine, and performs other necessary processes by generating an interrupt when performing other processes. Thereafter, the process returns to the main routine again to continue the motor control. In the motor control device 10 of the present embodiment, the time required for the main routine to go around once is about 200 μsec on average.

If the time required to execute the main routine once becomes longer, smooth control may not be possible when the motor is rotated at a high speed. Therefore, it is desirable that the processing time of the main routine be as short as possible. For that purpose, the electrical angle detection process also needs to detect the electrical angle in as short a time as possible. Therefore, the electrical angle detection device 100 of the present embodiment detects the electrical angle as follows.

C. Electric angle detection processing: (1) Electric angle detection principle: For example, when a high voltage is applied to the u-phase terminal and a low voltage is applied to the v-phase terminal and the w-phase terminal of a three-phase motor, a current flows through the U-phase coil. . U phase -V at this time
It is known that the inductance L of the circuit between the W phases changes depending on the angle (electric angle) between the d axis of the rotor 62 and the q axis of the rotating magnetic field. FIG. 6 is an explanatory diagram showing a state in which the inductance L between the phases changes according to the electrical angle. In FIG. 6, L1 indicates the inductance of the circuit between the U-phase and VW-phase, and L2 indicates the inductance of the V-phase.
5 shows the inductance of the circuit between the WU phases. As shown in FIG. 6, the inductance L1 and the inductance L
2 has a phase difference of 120 degrees. This relationship is easy to understand when considered as follows. Since the orientations of the U-phase coil and the V-phase coil are different from each other by 120 degrees, the state of the V-phase coil at the moment when the magnetic field is directed to a certain direction and the U-phase coil whose electrical angle is advanced by 120 degrees from that moment The state becomes the same. Therefore, the inductance L between the V phase and the WU phase
2 has a relationship in which the phase is advanced by 120 electrical degrees with respect to the inductance L1 between the U-phase and the VW-phase.

The electrical angle can be obtained from the inductances L1 and L2 based on the relationship shown in FIG.
That is, when the value of the inductance L1 is obtained, the electrical angle corresponding to such an inductance becomes α1 shown in FIG.
Or α4. Although it is not possible to determine which of the four is based on the inductance L1 alone, if the inductance L2 is further obtained, L
From the relationship with 2, it is possible to determine which of the electrical angles is α1 to α4.

The inductance can be obtained from the transient current change when a step-like voltage is applied to the electric circuit as follows. Assuming that the impedance of the circuit is R, the inductance is L, and the voltage value of the applied step-like voltage is E1, the current value I (t) is obtained by the following equation. I (t) = {1-exp (-Rt / L)} E1 / R (1) where exp () represents an exponential function.

FIG. 7 is an explanatory diagram showing a change in the current value I (t) with respect to the inductance L. FIG. 7A and FIG.
(B) is a comparison of the case where the value of the voltage value E1 is changed. The current value increases linearly immediately after the application of the voltage, but gradually decreases after a while, and eventually changes to a steady state at the current value E1 / R when the voltage E1 is applied. When the inductance has a particularly small value, as shown in FIG. 7, the waveform slightly oscillates immediately after the application of the voltage, and eventually shows a waveform which stabilizes to a steady value.
As is clear from FIG. 7, if the voltage value to be applied is fixed, the current value I (t0) when a predetermined time t0 has elapsed from the voltage application is determined by the value of the inductance L (see the above (( 1) See equation). Therefore, if the relationship between the current value I (t0) and the inductance L under the conditions of the applied voltage E1 and the time t0 is a constant value and the relationship between the current value I (t0) and the inductance L is obtained in advance from the equation (1), only the measurement of the current value The inductance L can be obtained immediately.

As described above, in the electrical angle measurement process, it is necessary to measure the electrical angle in as short a time as possible. Therefore, the timing t0 at which the current is measured and the voltage E1 to be applied are set to constant values, and a correspondence table between the current value and the inductance under the conditions is calculated in advance, and the correspondence table is referred to from the detected current value. A method for obtaining the inductance immediately has been adopted. However, as will be described later, in the electrical angle detection processing of the present embodiment, the applied voltage is variable in order to measure the electrical angle in a shorter time than in the conventional method. There are various aspects in the electrical angle detection method of the present embodiment, and these aspects will be described below.

(2) Electric angle detection processing (first embodiment): The electric angle detection processing of the first embodiment of the present embodiment will be described. First, the specific processing content of the present processing will be described, and then the effect obtained by employing the electrical angle detection processing of the first embodiment will be compared with the conventionally performed electrical angle detection processing. Will be described.

FIG. 8 is a flowchart showing the flow of the electrical angle detection process in the first embodiment of the present embodiment.
This process is a process executed by CPU 202 of ECU 200 in the main routine shown in FIG.

When starting the electrical angle detection process, the CPU 202 first detects an initial current value I0 (step S20).
0). That is, the current value flowing through the coil before application of the pulse voltage is detected as the initial current value I0 using the current detector 12.

When detecting the initial current value I0, the CPU 202 applies a pulse voltage to the coil by controlling the inverter 30 (step S202). The applied voltage is generated by lowering the voltage supplied from the power supply 80 at a predetermined rate. In this embodiment, the power supply 80 is normally 400 V
Before and after the voltage is supplied, this voltage is reduced to about 250 V and applied, so that the voltage is reduced to about 60%. Various well-known methods can be applied as the step-down method. For example, if two resistors are connected in series to the power supply 80 and a voltage at an intermediate position of the resistors is used, a voltage stepped down by a ratio determined by a ratio of the two resistance values can be obtained. Further, if a circuit called a DC chopper is used, or a technique such as PWM control is used, the voltage reduction ratio can be freely changed. In this embodiment, the voltage is lowered using a DC chopper.

When the pulse voltage is applied, it waits for a predetermined time t0 to elapse (step S20).
4) The current value I1 of the coil after a predetermined time t0 has elapsed is detected (step S206). The current detectors 12 and 14 are used for detecting the current value.

In the electrical angle detection process of this embodiment, the current value I1
Immediately after the detection, the actual pulse voltage is detected (step S2).
08). Here, the actual pulse voltage is a pulse voltage value actually applied to the coil. In the present embodiment, as described above, the voltage of the power supply 80 is reduced at a predetermined ratio to generate a pulse voltage.
The actual pulse voltage was calculated by multiplying the detected voltage by a predetermined coefficient (a value smaller than 1). The voltage supplied by the power supply 80 was detected using a voltage sensor (not shown) built in the motor control device 10. Although the actual pulse voltage has been described as being calculated here, the pulse voltage applied to the coil may be measured directly by a known method such as using a voltage sensor.

The timing of detecting the actual pulse voltage is preferably as close as possible to the timing of applying the pulse voltage or detecting the current value. In this sense, it is desirable to detect the actual pulse voltage immediately after the application of the pulse voltage (step S202), but in this embodiment, the time from application of the pulse voltage to current detection is short (for example, several tens of seconds). μse
c), the actual pulse voltage is detected after detecting the current value I1. Of course, the actual pulse voltage may be detected immediately before the application of the pulse voltage. When the actual pulse voltage is directly measured using a voltage sensor, the maximum value of the pulse voltage may be held.

When detecting the actual pulse voltage, the CPU 202 calculates the actual current change amount (step S210). The current change amount (actual current change amount) actually generated in the coil by applying the pulse voltage is calculated by subtracting the initial current value I0 from the current value I1 detected in step S206.

After calculating the actual current change, step S2
08 and the actual pulse voltage detected in step S21
A reference current change is estimated from the actual current change calculated at 0 (step S212). The reference current change amount is a current generated in a coil by applying a pulse voltage of a reference voltage (250 V in the present embodiment), and is a virtual current flowing through the coil at a point in time when a predetermined time t0 elapses from the application of the pulse voltage. Value. The reference current change amount is estimated using the principle described below.

FIG. 9 is an explanatory diagram conceptually showing the relationship between the electrical angle and the current change amount. As described above, the amount of change in current when a pulse voltage is applied and the inductance L of the circuit have a correspondence relationship as shown in Expression (1), and the inductance L and the electrical angle are shown in FIG. It is known that there is such a correspondence. Therefore, when the pulse voltage is constant, there is a certain correspondence between the electrical angle and the current change via the inductance L. The thick solid line in FIG. 9 conceptually shows the relationship between the current change amount obtained when a reference voltage (250 V) pulse voltage is applied and the electrical angle. Further, each broken line shown in FIG. 9 indicates the relationship between the current change amount and the electrical angle when a pulse having a voltage offset from the reference voltage by a different value is applied.

As shown in FIG. 9, as the value of the pulse voltage applied to the coil is offset from the reference voltage, the value of the current change is also offset. That is, the curve indicating the amount of change in current at a certain electrical angle moves up and down in FIG. 9 as the applied voltage increases and decreases. For example, when the applied voltage is higher than the reference voltage, the curve indicating the current change amount is offset upward. Conversely, when the applied voltage is smaller than the reference voltage, the curve indicating the current change amount is offset downward. Therefore, even when a pulse of a voltage smaller than the reference voltage is applied, if the offset of the current change is known, the current change when the pulse of the reference voltage is applied can be estimated. As shown in FIG. 9, since the offset of the current change increases and decreases with the offset of the applied voltage, in order to know the offset of the current change, the offset (actual pulse voltage) actually applied to the coil must be determined. A voltage difference dV from the reference voltage (hereinafter referred to as a voltage offset amount) and an offset amount dI of the current change amount
(Hereinafter referred to as a current offset amount).

FIG. 10 shows the result of examining the average value of the current change by applying various values of pulse voltage in order to obtain the relationship between the voltage offset dV and the current offset dI. is there. The average value of the current change amount is a value obtained by averaging the current change amounts in a range from 0 electrical degrees to 360 electrical degrees. The offset of the average value of the current change amount matches the offset of the current change amount itself, that is, the current offset amount dI (see FIG. 9). As shown in FIG. 10, since the current offset dI has a substantially proportional relationship with the voltage offset dV, the current offset dI can be obtained by multiplying the voltage offset dV by a predetermined coefficient. . Needless to say, a correspondence table between the voltage offset amount dV and the current offset amount dI may be created from the results in FIG. 10 and the current offset amount dI with respect to the voltage offset amount dV may be obtained by referring to the correspondence table. . As an example, FIG. 11 conceptually shows an example of a correspondence table between dV and dI. By estimating the reference current change amount using the correspondence table as shown in FIG. 11, even if the relationship between dV and dI is nonlinear, it is possible to improve the calculation accuracy of dI, and to calculate the reference current change amount. The estimation accuracy can be improved.

As is clear from the above description, in step S212 of the electrical angle detection process shown in FIG. 8, the reference current change amount is estimated as follows. First, step S20
The voltage difference dV between the actual pulse voltage detected in step 8 and the reference voltage is obtained, and the current offset dI is calculated by multiplying the offset dV of the applied voltage by a predetermined coefficient. Or Figure 1
The current offset dI is calculated with reference to the correspondence table shown in FIG. Next, the reference current change amount is estimated by adding the current offset amount dI to the actual current change amount detected in step S210.

When the reference current change amount is estimated in this way,
Using this estimated value, an electrical angle is calculated by a method similar to the conventional method (step S214). In brief, referring to FIG. 9, four electrical angles β1 to β4 are obtained as possible electrical angles for the estimated reference current change Ir. Although it is not possible to specify any of the four electrical angles from the current flowing through the U-phase coil alone, if the electrical angle is calculated by the same method for the current flowing through the other phase (V-phase) coil, An electrical angle that satisfies both conditions of the U-phase coil and the V-phase coil can be specified.

When the electrical angle detecting process is completed as described above, the process returns to the motor control process shown in FIG. 5, and the processes after the terminal voltage determining process S102 are executed.

The electrical angle detection process of the first embodiment has the effect of not only speeding up the calculation of the electrical angle but also improving the calculation accuracy. Hereinafter, the reason why such an effect is obtained by the electrical angle detection process of the first embodiment will be described in comparison with a conventional electrical angle detection process.

FIG. 12 is a flow chart showing the flow of the electric angle detection processing conventionally performed. The conventional electrical angle detection process shown in FIG. 12 will be briefly described in comparison with the electrical angle detection process of the first embodiment shown in FIG. In the electrical angle detection processing that has been performed conventionally, the power supply voltage Vb is first detected, and the voltage correction coefficient K is calculated based on the detected power supply voltage (steps S300 and S30).
2). The voltage correction coefficient K is obtained by equation (2). K = α × Vs / Vb (2) Here, Vs is a reference voltage applied to the coil. Further, α is a coefficient used to secure the resolution of the voltage correction coefficient K for the sake of calculation processing. That is, since the CPU used for motor control cannot handle a very small number, the resolution of the voltage correction coefficient K is ensured by multiplying by a predetermined coefficient α. Reference voltage Vs
Is set to a value lower than the power supply voltage Vb, the voltage correction coefficient K takes a value smaller than α. As is clear from the equation (2), the voltage correction coefficient K is a value indicating how much the voltage supplied from the power supply is reduced to obtain the reference voltage Vs.

After calculating the voltage correction coefficient K, a pulse voltage of the reference voltage Vs is applied after detecting the initial current value I0 flowing through the coil in advance (steps S304 and S3).
06). The pulse of the reference voltage is generated by lowering the power supply voltage according to the voltage correction coefficient K obtained in step S302.

After a lapse of a predetermined time from the application of the pulse voltage of the reference voltage, the current value I1 flowing through the coil is detected, and the difference from the initial current value I0 is calculated to calculate the reference current change amount (step S1). S308, S310, S3
12). An electrical angle is calculated from the reference current change thus obtained (step S314).

The conventional electrical angle detection processing shown in FIG.
When compared with the electrical angle detection processing of the first embodiment shown in FIG. 8, the two points are different in the following points. In the conventional method, a pulse of the reference voltage is applied to the coil, and the amount of current change at that time is detected. Therefore, the power supply voltage is detected before applying a pulse to the coil, and the voltage correction coefficient K is calculated using the equation (2).
, It was necessary to lower the power supply voltage. On the other hand, in the electrical angle detection process of the first embodiment, the power supply voltage is stepped down at a fixed ratio and applied to the coil, and the detected current change is corrected to estimate the reference current change.
The reference current change amount can be estimated by adding the current offset amount dI to the actually detected current change amount, and the current offset amount dI is obtained by multiplying the voltage offset amount dV by a predetermined coefficient, or It can be obtained by referring to a correspondence table between the voltage offset amount dV and the current offset amount dI (see FIGS. 10 and 11).

Because of such a difference, the electrical angle detecting process in the first embodiment of the present embodiment can be performed more quickly than the conventional processing method. The reason will be described below.

In the electrical angle detection process according to the conventional method, it is necessary to calculate the voltage correction coefficient K. In the equation (2) used for calculating the voltage correction coefficient K, the power supply voltage Vb is included in the denominator. Since the power supply voltage Vb is a measured value and is not usually a simple value, a long calculation time is required for the division as in the equation (2). As a result, it takes time to calculate the voltage correction coefficient K.

On the other hand, in the method of the first embodiment,
The voltage offset dV is obtained, multiplied by a predetermined coefficient to calculate a current offset dI, and this current offset dI is added to the detected current change to obtain a reference current change. That is, since only the operations of subtraction, multiplication and addition are included, quick calculation is possible. Therefore,
The electrical angle detection processing according to the first embodiment can be performed more quickly than the conventional electrical angle detection processing.

As shown in the flowchart of FIG. 12, in the conventional electrical angle detection process, the voltage of the power supply is corrected by calculating the voltage correction coefficient K at the beginning of the process (step of FIG. 12). S302). If there is an error in this correction, the error may accumulate as the subsequent processing proceeds. On the other hand, in the electrical angle detection method according to the first embodiment, the current change amount is corrected at the end of the processing (S212 in FIG. 8). Therefore, even if an error is included in the correction, the error does not accumulate as the process proceeds, so that the electrical angle can be detected with high accuracy.

The electrical angle detection processing of the first embodiment has the advantage that even if the power supply voltage is greatly reduced, the detection accuracy is not reduced unlike the conventional electrical angle detection method. That is, in the conventional electrical angle detection method, in order to apply a pulse of a preset reference voltage, the voltage supplied from the power supply is reduced at an appropriate rate and then applied to the coil. . Therefore, when the power supply voltage becomes lower than the reference voltage, it becomes impossible to apply the pulse of the set reference voltage, so that the electrical angle detection accuracy is reduced.
The step-down ratio (voltage correction coefficient K) is calculated by the CPU using equation (2), and is stored as 1-byte or 2-byte information. Therefore, when the power supply voltage becomes too small, the voltage correction coefficient K exceeds the upper limit value that can be expressed by 1 byte or 2 bytes, and sticks to the upper limit value, so that a so-called overflow occurs. When an overflow occurs, a pulse of the set reference voltage cannot be generated, so that the electrical angle detection accuracy is reduced.

On the other hand, in the first electrical angle detection process of this embodiment, the voltage applied to the coil is detected (step S208 in FIG. 8), and the amount of change in current caused by the pulse voltage is corrected. Detect electrical angle. Therefore, even if the power supply voltage is significantly reduced, the detection accuracy of the electrical angle does not decrease. The current offset amount dI used for correcting the current change amount is calculated by multiplying the voltage offset amount dV by a predetermined coefficient, or is calculated in a correspondence table between the voltage offset amount dV and the current offset amount dI as shown in FIG. Calculated based on Therefore, there is no possibility that an overflow will occur when correcting the current change amount, and there is no possibility that the detection accuracy is reduced by the overflow.

For the above reasons, according to the electrical angle detection processing of the first embodiment of the present embodiment, it is possible to quickly detect the electrical angle and to improve the detection accuracy.

(3) Electric angle detection processing (second embodiment): In the electric angle detection processing of the first embodiment described above,
Regardless of the voltage value supplied from the power supply, a pulse voltage stepped down at a predetermined ratio is applied. For this reason, it is possible to accurately detect the electrical angle even in a low power supply voltage region where the detection accuracy is likely to be reduced by the electrical angle detection method. However, in order to improve the detection accuracy of the electrical angle, the detection accuracy can be improved only by improving the detection method under the condition where the power supply voltage is low. That is,
A threshold voltage may be set in advance, and the electrical angle may be detected only when the power supply voltage becomes lower than the threshold voltage according to the above-described first embodiment. The electrical angle detection process in the second embodiment of the present embodiment detects an electrical angle based on such a concept.

FIG. 13 is a flowchart showing the flow of the electrical angle detection process in the second embodiment of the present embodiment. This processing is performed by the CPU 202 of the ECU 200 in FIG.
In the main routine of Hereinafter, the details of the electrical angle detection processing in the second embodiment will be described with reference to FIG.

When the electric angle detection process according to the second embodiment is started, first, the CPU 202 detects the initial current I0 flowing through the coil and the power supply voltage Vb (step S400,
S402). Next, the detected power supply voltage Vb is compared with a predetermined threshold voltage Vth (step S404). As the value of the threshold voltage Vth, a substantially lower limit voltage value capable of generating a pulse of the reference voltage with high accuracy is selected.

When the power supply voltage Vb is higher than the threshold voltage Vth, the electrical angle is detected by a method similar to the conventional method (see FIG. 12 for details). That is, the voltage correction coefficient K is calculated by the equation (2) (step S406), the power supply voltage is reduced according to the obtained voltage correction coefficient K, and a pulse of the reference voltage is applied (step S408). The detected current value I1 is detected at a predetermined timing (steps S410 and S412). Detected current value I1
Is subtracted from the initial current value I0 to calculate the reference current change amount (step S414). As described with reference to FIG. 9, the electrical angle is calculated using the correspondence between the reference current change amount and the electrical angle. It is calculated (step S416).

On the other hand, when the power supply voltage Vb is smaller than the threshold voltage Vth, the electrical angle is detected by using the same method as in the first embodiment. That is, the value of the voltage correction coefficient K is fixed to Klmt (step S418), and a voltage pulse generated by stepping down the power supply voltage according to the fixed voltage correction coefficient Klmt is applied (step S420).
The value of Klmt is the voltage correction coefficient K calculated in step S406 when power supply voltage Vb is equal to threshold voltage Vth.
Is the value of Since Klmt is set to such a value,
Even if the value Vb of the power supply voltage fluctuates in the vicinity of the threshold voltage Vth, the electrical angle detection method can be switched smoothly and unnaturally. Also, since Klmt corresponds to the case where the step-down ratio of the power supply voltage is the smallest, if the voltage correction coefficient K is fixed to such a value, the applied pulse voltage is set to the highest voltage value that can be applied stably. Can be. As the applied voltage increases, the amount of change in the current generated in the coil also increases, so that the accuracy of detecting the amount of change in the current can be improved, and the accuracy of detecting the electrical angle can be improved. In the example shown in FIG. 13, the value of the pulse voltage actually applied to the coil is calculated from the detected value of the power supply voltage. However, the pulse voltage applied to the coil may be directly detected.

After a predetermined time has elapsed from the application of the pulse voltage (step S422), the coil current value I1 is detected (step S424), and the initial current value I is calculated based on the detected current value I1.
The actual current change amount is calculated by subtracting 0 (step S42).
6).

From the actual current change thus obtained, a reference current change is estimated as follows (step S42).
8). First, the difference between the actual voltage of the pulse applied to the coil and the reference voltage is determined, and the current offset dI is calculated based on the voltage offset dV. The voltage offset amount dV can be obtained as a value obtained by lowering the voltage difference between the power supply voltage Vb and the threshold voltage Vth detected in step S402 at a rate determined by Klmt. The current offset dI can be obtained by referring to the correspondence table shown in FIG. 11 for the voltage offset dV thus obtained. Alternatively, it is also possible to calculate the current offset dI by utilizing the fact that the voltage offset dV and the current offset dI are substantially proportional to each other.

In the reference current change estimation process in step S428, the reference current change is estimated by adding the current offset dI obtained by the above-described method to the current change detected in step S424. I have. The electrical angle is detected based on the correspondence between the reference current change amount and the electrical angle thus estimated (step S416).

FIG. 14 shows the power supply voltage Vb and the voltage correction coefficient K in the electrical angle detection processing of the second embodiment.
FIG. 5 is an explanatory diagram showing a relationship between the pulse voltage and an applied pulse voltage. As shown, the region where the power supply voltage Vb is high (FIG. 14)
In the middle region B), the value of the voltage correction coefficient K increases as the power supply voltage Vb decreases, and as a result, the value of the pulse voltage applied to the coil is maintained at the reference voltage Vs. In a region where the power supply voltage Vb is lower than the threshold voltage Vth (region A in the figure), the voltage correction coefficient K keeps a constant value Klmt, so that the pulse voltage value decreases as the power supply voltage Vb decreases. According to the electric angle detection processing that has been performed conventionally, since the pulse of the reference voltage Vs cannot be applied to the region A, the detection accuracy of the electric angle has been reduced. On the other hand, according to the electrical angle detection process of the second embodiment, when the electrical angle is detected in the region A, the reference current change amount is estimated from the detected value of the current change amount. It is possible to accurately detect the electrical angle. Further, since it is not necessary to calculate the voltage correction coefficient in the area A, the electric angle measurement time in this area can be reduced. Therefore, by using the electrical angle detection process of the second aspect of the present embodiment, it is possible to accurately detect the electrical angle regardless of the value of the power supply voltage and to shorten the electrical angle calculation time.

Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the gist of the invention. For example, in the above description,
Although the motor is an AC synchronous motor, it is not limited to this, and can be applied to other motors such as a brushless DC motor. Also, the case where the electric angle detecting device is used for motor control has been described. However, the electric angle detecting device is not limited to motor control and may be used for other purposes as long as it detects an electric angle.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a configuration of a motor control device using an electric angle detection device according to an embodiment.

FIG. 2 is an explanatory diagram showing a device configuration of a motor control device using the electric angle detection device of the present embodiment.

FIG. 3 is a longitudinal sectional view showing a structure of a three-phase synchronous motor controlled by using the electric angle detecting device of the embodiment.

FIG. 4 is a cross-sectional view showing the structure of a three-phase synchronous motor controlled using the electrical angle detection device of the embodiment.

FIG. 5 is a flowchart illustrating a flow of a motor control process performed using the electrical angle detection device according to the embodiment.

FIG. 6 is an explanatory diagram for explaining that an electrical angle and an inductance have a predetermined correspondence relationship in a synchronous motor.

FIG. 7 is an explanatory diagram showing a state where a transient current fluctuation occurs in a coil when a step-like voltage is applied.

FIG. 8 is a flowchart illustrating a flow of an electrical angle detection process according to the first embodiment.

FIG. 9 is an explanatory diagram conceptually showing how a current change amount is offset with an offset of an applied voltage.

FIG. 10 is an explanatory diagram conceptually showing a relationship between a pulse voltage and an average value of a current change amount.

FIG. 11 is an explanatory diagram conceptually illustrating a correspondence table showing a correspondence relationship between a voltage offset and a current offset.

FIG. 12 is a flowchart showing a flow of an electric angle detection process conventionally performed.

FIG. 13 is a flowchart illustrating a flow of an electrical angle detection process according to the second embodiment.

FIG. 14 is an explanatory diagram showing changes in a voltage correction coefficient and a pulse voltage when an electrical angle detection process according to the second embodiment is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Motor control device 12, 14 ... Current detector 20 ... Control part 30 ... Inverter 40 ... Electric angle detection part 50 ... Torque detection part 60 ... Three-phase synchronous motor 61 ... Stator 62 ... Rotor 63 ... Case 64a-64d ... permanent magnet 65 ... rotating shaft 66a, 66b ... bearing 67 ... plate-like rotor 68a to 68d ... salient pole 69 ... plate-like stator 70 ... teeth 71 ... slot 72 ... coil 73 ... bolt 80 ... power supply 100 ... electric angle detection Devices 102, 104 Filter 106, 108 ADC 200 ECU 202 CPU 204 ROM 206 RAM 208 Input port 210 Output port 212 Bus

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Eiji Yamada 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 5H560 BB04 BB12 DA13 DC12 EB01 GG04 TT11 UA02 XA02 XA03

Claims (9)

[Claims] 1. An electric angle measuring device for measuring an electric angle between a rotor and a stator of an electric motor, comprising: pulse voltage applying means for applying a pulse voltage to a coil of the electric motor; Means for measuring the amount of change in the current generated in the coil, and compensating the amount of change in the current based on the voltage value of the applied pulse voltage, corresponding to the application of the pulse voltage of the reference voltage value An electrical angle measuring device comprising: a reference current change amount estimating means for estimating the obtained reference current change amount; and an electrical angle determining means for determining the electrical angle based on the estimated reference current change amount. 2. The electrical angle measuring device according to claim 1, wherein a voltage value of a pulse voltage applied to the coil and a compensation for converting the measured current change amount into the reference current change amount. And a compensation amount storage unit that stores a correspondence relationship with the amount. The reference current change amount estimation unit refers to the stored correspondence relationship based on a voltage value of the applied pulse voltage, and refers to the compensation amount. The electrical angle measuring device is means for estimating the reference current change amount by calculating the reference current change amount by compensating the current change amount using the compensation amount. 3. The electrical angle measuring device according to claim 1, wherein the pulse voltage applying unit is a unit that applies the pulse voltage having a voltage value that increases and decreases with a DC voltage supplied from a power supply. An electrical angle measurement device comprising pulse voltage measurement means for measuring a voltage value to obtain a voltage value of the applied pulse voltage. 4. The electric angle measuring device according to claim 1, wherein the electric motor is a synchronous motor. 5. The electrical angle measuring device according to claim 1, further comprising: a power supply voltage measuring unit for measuring a DC voltage value supplied from a power supply, and wherein the pulse voltage applying unit includes the measured DC voltage. When the value is equal to or more than a predetermined value, a pulse voltage having a predetermined reference voltage value is applied to the coil, and when the DC voltage value is equal to or less than a predetermined value, a pulse voltage having a voltage value proportional to the DC voltage value is applied. Means, the compensation amount storage means, the reference current change amount estimation means,
When the measured DC voltage value is equal to or less than the predetermined value,
The electric angle determination means, which performs each function, the electrical angle determination means, the reference current change amount estimated when the DC voltage value is less than the predetermined value, or when the DC voltage value is more than the predetermined value An electrical angle measuring device, which is means for determining the electrical angle based on a measured reference current change amount. 6. The electrical angle measuring device according to claim 5, wherein the pulse voltage applying unit applies a pulse voltage of the reference voltage value when the DC voltage value is equal to or more than the reference voltage value. An electrical angle measuring device which is means for applying a pulse voltage of the DC voltage value when the DC voltage value is equal to or less than the reference voltage value. 7. An electric motor control device that measures an electric angle between a rotor and a stator of an electric motor and controls the electric motor based on the measured electric angle, Pulse voltage applying means for applying a pulse voltage to the coil; actual current change amount measuring means for measuring the current change amount generated in the coil by the pulse voltage; and the current based on a voltage value of the applied pulse voltage. A reference current change estimating means for compensating the change amount and estimating a reference current change amount corresponding to the application of the pulse voltage of the reference voltage value; and an electric device for determining the electric angle based on the estimated reference current change amount. An electric motor control device comprising: an angle determination unit; and a current control unit that controls a current supplied to the coil based on the determined electrical angle. 8. An electric angle measuring method for measuring an electric angle between a rotor and a stator of an electric motor, comprising applying a pulse voltage to a coil of the electric motor, and applying the pulse voltage to the coil. The amount of current change occurring in the reference voltage value is measured, and the current change amount is compensated based on the applied pulse voltage, thereby estimating the reference current change amount corresponding to the application of the pulse voltage of the reference voltage value. An electrical angle measuring method for measuring the electrical angle based on a current change amount. 9. A method of measuring an electric angle between a rotor and a stator of an electric motor and controlling the electric motor based on the measured electric angle, wherein a pulse voltage is applied to a coil of the electric motor. By measuring the amount of change in current generated in the coil due to the application of the pulse voltage, and compensating for the amount of change in current based on the applied pulse voltage, the application of the pulse voltage of the reference voltage value was supported. An electric motor control method for estimating a reference current change amount, determining the electric angle based on the estimated reference current change amount, and controlling a current supplied to the coil based on the determined electric angle. .