Electric motor control device

Abstract

An electric motor control device (100) comprises an angle computing unit (14). Said electric motor control device computes angle information (θ) of a rotor on the basis of the output of a magnetic rotation angle sensor (3), drives an inverter (1) using said angle information (θ), and controls an electric motor (M). The angle computing unit (14) acquires a sine signal and a cosine signal that are electric signals (S1, S2) based on the output of the rotation angle sensor (3), uses the electric signals (S1, S2) with the electric signals (S1, S2) alternately switched by 90° so as to remove an end region (β) of the electric signals (S1, S2), and computes the angle information (θ).

Description

Motor control device

[0001] The present disclosure relates to an electric motor control device.

[0002] The motor control device described in Patent Document 1 includes a magnetic rotation angle sensor provided coaxially with the motor's output shaft, and a control circuit. The rotation angle sensor generates an electric signal corresponding to the rotation of the output shaft. The electric signal includes a sine signal that changes sinusoidally with respect to the rotation of the motor, and a cosine signal that is 90° out of phase with the sine signal. The control circuit calculates the motor's rotation angle by calculating an arctangent value based on the sine signal and the cosine signal, and controls the motor using the rotation angle.

[0003] Japanese Patent Application Laid-Open No. 2023-136019

[0004] In conventional control circuits, electrical signals from a magnetic rotation angle sensor are AD-converted (analog-to-digital) and then input. When the amplitude of the electrical signal exceeds the AD conversion input range, the waveforms of the sine and cosine signals are partially missing and distorted, making it impossible to accurately calculate the rotation angle. Furthermore, the linearity of both the sine and cosine signals significantly decreases near their extreme values, limiting the accuracy of the angle information based on each signal. Therefore, it was difficult to accurately obtain the rotation angle using conventional technology that calculates the arctangent value based on the sine and cosine signals.

[0005] The present disclosure discloses a technology for solving the above-mentioned problems, and aims to provide an electric motor control device that can calculate rotor angle information with high precision based on the output from a magnetic rotation angle sensor provided in the electric motor, thereby improving the control performance of the electric motor.

[0006] The electric motor control device according to the present disclosure drives an inverter to control an electric motor, and includes an angle calculation unit that calculates rotor angle information based on the output of a magnetic rotation angle sensor provided in the electric motor. The angle calculation unit acquires two electrical signals, a sine signal and a cosine signal, based on the output of the rotation angle sensor, and calculates the angle information by alternately switching between the sine signal and the cosine signal in 90° increments so as to remove end regions including extreme values ​​in the sine signal and the cosine signal. The electric motor control device then calculates a control command for the inverter using the angle information.

[0007] The electric motor control device according to the present disclosure can improve the control performance of the electric motor by calculating rotor angle information with high precision based on the output from a magnetic rotation angle sensor provided in the electric motor.

[0008] 1 is a block diagram showing a schematic configuration of an electric motor control device according to embodiment 1. FIG. 2 is a perspective view of a rotation angle sensor according to embodiment 1. FIG. 3 is a diagram showing a hardware configuration including a circuit configuration of an inverter according to embodiment 1. FIG. 4 is a flowchart showing an operation by an angle calculation unit according to embodiment 1. FIG. 5 is a waveform diagram explaining an operation by an angle calculation unit according to embodiment 1. FIG. 6 is a waveform diagram explaining an operation by an angle calculation unit according to embodiment 1. FIG. 7 is a flowchart showing an operation by an angle calculation unit according to embodiment 2. FIG. 8 is a waveform diagram explaining an operation by an angle calculation unit according to embodiment 2. FIG. 9 is a waveform diagram explaining an operation by an angle calculation unit according to another example of embodiment 2. FIG. 10 is a diagram showing a hardware configuration of a control unit according to embodiments 1 and 2.

[0009] Embodiment 1. Fig. 1 is a block diagram showing a schematic configuration of an electric motor control device according to embodiment 1. As shown in the figure, an electric motor control device 100 controls an electric motor M. The electric motor control device 100 includes a three-phase inverter 1 (hereinafter referred to as the inverter) and a control unit 10. The control unit 10 drives the inverter 1, and the inverter 1 supplies AC power to the electric motor M, thereby controlling the electric motor M. The control unit 10 is a small processor, such as a microcomputer, that has an AD conversion function. The hardware configuration of the control unit 10 will be described later.

[0010] The electric motor M is a brushless motor (permanent magnet synchronous motor) driven by a sine wave drive system or a square wave drive system. The electric motor M is provided with a magnetic rotation angle sensor 3, which outputs electric signals Sa1 and Sa2, which are analog signals that detect the rotation angle θ of the rotor of the electric motor M. The electric signal Sa1 is a sine signal that changes sinusoidally with respect to the rotation angle θ of the rotor, and the electric signal Sa2 is a cosine signal that is 90° out of phase with respect to the electric signal Sa1.

[0011] The motor control device 100 receives the electric signals Sa1 and Sa2 from the rotation angle sensor 3, and also receives the detected output current I from the inverter 1 to the motor M. The motor control device 100 also includes a signal amplifier 2 that amplifies the input electric signals Sa1 and Sa2, and the amplified electric signals Sa1 and Sa2 are input to the control unit 10. The signal amplifier 2 is composed of electronic components such as an operational amplifier, and amplifies the input signal by a preset amplification factor.

[0012] The control unit 10 includes a speed control unit 11, a current control unit 12, a PWM (Pulse Width Modulation) circuit 13, an angle calculation unit 14, and a speed calculation unit 15. The output of the signal amplifier 2 is input to the control unit 10 and converted into digital form by the AD conversion function of the control unit 10. Two digital electric signals S1 and S2 are then input to the angle calculation unit 14. The electric signal S1 is a sine signal that changes sinusoidally with respect to the rotation angle θ of the rotor, and the electric signal S2 is a cosine signal whose phase is delayed by 90° relative to the electric signal S1.

[0013] The angle calculation unit 14 calculates the rotor rotation angle θ (°), which serves as angle information, based on the two electrical signals S1 and S2, and further calculates the electrical angle θe. The speed calculation unit 15 calculates the rotation speed ω by differentiating the rotation angle θ with respect to time. The speed control unit 11 calculates a current command Iref based on an externally applied rotation speed command ω* of the electric motor M and the rotation speed ω from the speed calculation unit 15, so that the rotation speed ω approaches the rotation speed command ω*. The current command Iref is composed of a d-axis current command and a q-axis current command.

[0014] The current control unit 12 receives the current command Iref, the detected output current I, and the rotation angle (electrical angle θe) from the angle calculation unit 14. The current control unit 12 converts the output current I, which is a three-phase current, into two-phase currents (d-axis current and q-axis current) based on the rotation angle (electrical angle θe). Then, two-phase voltage commands (d-axis voltage command and q-axis voltage command) are generated so that the two-phase currents approach the current command Iref. Furthermore, the two-phase voltage commands are converted into three-phase voltage commands Vref based on the rotation angle (electrical angle θe). In this way, the current control unit 12 calculates and outputs the voltage command Vref so that the output current I approaches the current command Iref. The PWM circuit 13 generates a duty ratio, which serves as a control command for PWM-controlling the inverter 1, based on the voltage command Vref from the current control unit 12.

[0015] FIG. 2 is a perspective view of the rotation angle sensor 3. The rotation angle sensor 3 is magnetic and includes a cylindrical bias magnet Mag and a magnetic sensor MR. The bias magnet Mag is a two-pole permanent magnet with a north pole and a south pole magnetized radially. In this case, a magnetoresistive sensor is used for the magnetic sensor MR. The magnetic sensor MR is disposed facing the bias magnet Mag at an axial distance. The bias magnet Mag applies a magnetic field to the magnetic sensor MR. That is, the bias magnet Mag rotates together with the output shaft 4, changing the direction of the bias magnetic field applied to the magnetic sensor MR, and the magnetic sensor MR generates electrical signals Sa1 and Sa2 according to the direction of the bias magnetic field. In this way, the rotation angle sensor 3 outputs electrical signals Sa1 and Sa2 according to the rotation angle θ of the rotor. Note that a bias magnet Mag with N poles, each consisting of a north-south pole pair, may be used, improving the resolution of the detected angle information by N times.

[0016] 3 is a diagram showing a hardware configuration including a circuit configuration of the inverter 1. As shown in the figure, the inverter 1 includes an inverter circuit 1A that converts DC power to AC power, a rectifier circuit 1B that converts AC power from a three-phase (R-phase, S-phase, T-phase) AC power source (not shown) into DC power, and a capacitor C. The rectifier circuit 1B is a three-phase bridge circuit formed of a plurality of diodes D, and the inverter circuit 1A is a three-phase bridge circuit formed of a plurality of switching elements Q, each of which has a diode connected in anti-parallel. The three-phase (R-phase, S-phase, T-phase) AC power is rectified by the rectifier circuit 1B and output to the capacitor C. In the inverter circuit 1A, the switching elements Q of each phase are switched based on a control command (duty ratio) from a control unit 10, and the DC power of the capacitor C is converted into three-phase (U-phase, V-phase, W-phase) AC power and supplied to the electric motor M.

[0017] Although FIG. 3 illustrates a case where the output current I to the motor M is detected for only two phases (U phase and W phase), the output current for the remaining V phase can be calculated based on the current values ​​of the two phases (U phase and W phase).

[0018] Next, the operation of the angle calculation unit 14 will be described in detail. FIG. 4 is a flowchart showing the operation of the angle calculation unit 14. FIGS. 5 and 6 are waveform diagrams explaining the operation of the angle calculation unit 14. As shown in FIG. 4, the angle calculation unit 14 first reads two electric signals S1 and S2 (step ST1). Each of the electric signals S1 and S2 is composed of a discretized digital value, and the angle calculation unit 14 periodically reads the two digital values ​​of the two electric signals S1 and S2. The reading period is set to the same period as the control period of the speed control unit 11 or the current control unit 12 so as not to burden the calculation load of the control unit 10.

[0019] As shown in Fig. 5, the electrical signal S1 is a sine signal (R sin θ) that changes sinusoidally with respect to the rotation angle θ of the rotor, and the electrical signal S2 is a cosine signal (R cos θ) that is delayed in phase by 90° relative to the electrical signal S1. R is the amplitude. Here, the electrical signals S1 and S2 are illustrated as being input to and read by the angle calculation unit 14 without any loss of waveform.

[0020] Next, the angle calculation unit 14 corrects the individual offset of the rotation angle sensor 3 for the electrical signals S1 and S2 (step ST2). Individual variations in the rotation angle sensor 3, variations in installation, and variations in magnetic flux due to magnetization of the magnet cause variations in the center voltage of the sine wave, resulting in an offset for the entire sine wave. This offset is measured in advance, or a moving average or an LPF (Low Pass Filter) with a large time constant is provided while the electric motor M is running to obtain the average value (center value) of the input electrical signal, and this center value is used as the offset of the rotation angle sensor 3. Then, in step ST2, the angle calculation unit 14 corrects the offset for the two electrical signals S1 and S2.

[0021] Next, the angle calculation unit 14 removes high-frequency noise from the electric signals S1 and S2 using an LPF (step ST3). The electric signals Sa1 and Sa2 output by the rotation angle sensor 3 are analog voltage signals, and are therefore susceptible to noise caused by switching due to PWM control of the inverter 1. Therefore, the electric signals S1 and S2 after AD conversion also contain high-frequency noise, and in step ST3, the angle calculation unit 14 removes the high-frequency noise.

[0022] Next, the angle calculation unit 14 calculates the rotor rotation angles AngS1 and AngS2 represented by the electrical signals S1 and S2, respectively, using an asin table (step ST4). Because the electrical signals S1 and S2 are sine waves, angle information can be calculated using asin calculations. However, in this example, the amount of calculations performed by the control unit 10 is reduced by pre-saving and using an asin table (asinTb), which is a conversion table. The rotation angle AngS1 is calculated by directly applying the asin table to the signal value of the electrical signal S1, i.e., by the formula AngS1 = asinTb(S1). Because the electrical signal S2 is a cosine signal, asinTb(S2), which the asin table associates with the signal value of S2, has a 90° phase lead, and AngS2 can be calculated using the following formula: AngS2 = asinTb(S2) - 90°

[0023] It is also possible to use only the asin table for 0° to 90°, in which case the amount of memory required for the asin table can be minimized. When using only the asin table for 0° to 90° (asinTb), the calculation is performed as follows for regions divided into 90° increments from 0° to 360°. Note that the region in which the electrical signals S1 and S2 are located is determined based on the polarity of S1 and S2.

[0024] From 0° to 90° (S1≧0, S2≧0), AngS1 = asinTb(S1), AngS2 = 90° - asinTb(S2). From 90° to 180° (S1≧0, S2<0), AngS1 = 180° - asinTb(S1), AngS2 = 90° + asinTb(-S2). From 180° to 270° (S1<0, S2<0), AngS1 = 180° + asinTb(-S1), AngS2 = 270° - asinTb(-S2). From 270° to 360° (S1<0, S2≧0), AngS1 = 360° - asinTb(-S1), AngS2 = 270° + asinTb(S2).

[0025] Although the memory capacity increases, it is also possible to store both an asin table and an acos table as conversion tables, and calculate the rotation angles AngS1 and AngS2 using the asin table for the electrical signal S1 and the acos table for the electrical signal S2.

[0026] Next, the angle calculation unit 14 determines whether the obtained rotation angle AngS1 satisfies the condition 45°<AngS1<135° or 225°<AngS1<315° (step ST5). If the condition is satisfied (Yes), the rotor rotation angle θ is set to θ=AngS2 (step ST6). If the rotation angle AngS1 does not satisfy the condition (No) in step ST5, the rotor rotation angle θ is set to θ=AngS1 (step ST7). Next, the angle calculation unit 14 calculates the electrical angle θe based on the obtained rotor rotation angle θ (mechanical angle) (step ST8).

[0027] As described above, the angle calculation unit 14 calculates the rotation angle θ, which is rotor angle information, based on the acquired electrical signals S1 and S2. As shown in FIG. 5 , the electrical signals S1 (R sin θ) and S2 (R cos θ) intersect at two intersections B1 and B2 during one 360° rotor rotation. The intersection B1 in the positive region has θ = 45° and a signal value A1 (= R / √2), while the intersection B2 in the negative region has θ = 225° and a signal value A2 (= -R / √2). Within the regions of the two electrical signals S1 and S2, the region sandwiched between the two signal values ​​A1 and A2 (< A1) at the two intersections B1 and B2 is defined as an inner region α, and the region outside of this is defined as an end region β.

[0028] As shown in steps ST5 to ST7 above, the angle calculation unit 14 uses AngS2 for θ when AngS1 is between 45° and 135° or between 225° and 315°, and uses AngS1 for θ in other cases, i.e., when AngS1 is between 0° and 45°, between 135° and 225°, or between 315° and 360°. The ranges 315° and 360° and the range 0° and 45° are continuous 90° intervals. In this way, the angle calculation unit 14 calculates the rotation angle θ by switching between the electrical signal S1 and the electrical signal S2 in increments of 90°.

[0029] 5, when θ is in the ranges of 315° to 45° and 135° to 225°, the electrical signal S1 is in the inner region α, and when θ is in the ranges of 45° to 135° and 225° to 315°, the electrical signal S2 is in the inner region α. ​​That is, the electrical signals S1 and S2 are switched in increments of 90° so as to eliminate the end region β. In this way, the angle calculation unit 14 calculates the rotation angle θ using only the inner region α, excluding the end region β of the electrical signals S1 and S2.

[0030] In this embodiment, as described in step ST5 of the operation description of the angle calculation unit 14, it determines whether one of the electrical signals S1 and S2, in this case the rotation angle AngS1 based on the electrical signal S1, is within an angle range corresponding to the end region β (45° to 135°, 225° to 315°). If the rotation angle AngS1 is within this angle range, the rotation angle AngS2 based on the electrical signal S2 is set as the rotor rotation angle θ. If the rotation angle AngS1 is outside this angle range, the rotation angle AngS1 is set as the rotor rotation angle θ. In this way, the rotation angle θ is calculated using only the inner region α of the electrical signals S1 and S2. Note that although the angle calculation unit 14 determines whether the rotation angle AngS1 is within the angle range corresponding to the end region β, it may also determine whether it is within the angle range corresponding to the inner region α. ​​In this case, when the rotation angle AngS1 is within this angle range, the rotation angle AngS1 becomes the rotor rotation angle θ. The determination may also be made using the rotation angle AngS2 based on the electrical signal S2.

[0031] In this way, the angle calculation unit 14 determines whether the rotor rotation angle AngS1 / AngS2 based on either the electrical signals S1 or S2 is within an angle range corresponding to either the inner region α or the end region β, and alternates between the electrical signals S1 and S2 in 90° increments based on the determination result. The waveforms of the electrical signals S1 and S2 are not ideal sinusoidal but contain some distortion or offset components due to factors such as the characteristics of the rotation angle sensor 3, manufacturing variations in the bias magnet Mag, or installation errors. If determination were made using both the rotation angles AngS1 and AngS2, it would be difficult to unify the determination results, and chattering would likely occur when switching between the electrical signals S1 and S2. In this embodiment, by determining using either the rotation angle AngS1 or the rotation angle AngS2, determination can be easily made using a single determination condition, and chattering when switching between the electrical signals S1 and S2 can be suppressed.

[0032] The end region β of the electrical signals S1 and S2 is a region that includes extreme values ​​and where linearity is significantly reduced. Therefore, the reliability of the values ​​of AngS1 and AngS2 is low in the end region β. As shown in FIG. 6 , AngS1 has a distortion portion Er1, such as a waveform break, in the end region β (45° to 135°, 225° to 315°). Similarly, AngS2 has a distortion portion Er2, such as a waveform break, in the end region β (0° to 45°, 135° to 225°, 315° to 360°). In this embodiment, by combining AngS1 and AngS2 outside the end region β, a rotation angle θ with a distortion-free waveform shape, as shown in the lower part of FIG. 6 , can be obtained.

[0033] Furthermore, in this embodiment, even if the electrical signals S1 and S2 before AD conversion exceed the AD conversion input range and there are gaps in the waveforms of the electrical signals S1 and S2 after AD conversion in the end regions β, the rotation angle θ is calculated excluding the end regions β, so the rotation angle θ can be calculated with high accuracy without any problems.

[0034] As described above, in this embodiment, the angle calculation unit 14 acquires the two electrical signals S1 and S2, that is, the sine signal and the cosine signal, based on the output of the rotation angle sensor 3, and calculates the rotation angle θ, which is angle information, by alternately switching between the sine signal S1 and the cosine signal S2 in increments of 90° so as to remove the end region β that includes extreme values ​​in the sine signal S1 and the cosine signal S2. This allows the motor control device 100 to acquire the rotation angle θ with high accuracy, thereby improving the control performance of the electric motor M.

[0035] The electrical signals S1 and S2 after AD conversion should be generated so as to include an inner region α sandwiched between two signal values ​​A1 and A2 (<A1) at the two intersections B1 and B2, i.e., the amplification factor of the signal amplifier 2 should be set so that the inner region α falls within the AD conversion input range. In this way, by expanding the inner region α, the angle Δdeg corresponding to the minimum resolution after AD conversion can be made finer, and angle information can be acquired more precisely.

[0036] In addition, to prevent the voltage amplified by the signal amplifier 2 from adversely affecting the control unit 10, a clamp diode may be installed at the output end of the signal amplifier 2 to limit the upper and lower limits of the voltage input to the control unit 10 to the allowable range of the input voltage of the control unit 10.

[0037] In addition, in the above embodiment, the rotation angle sensor 3 outputs two electrical signals Sa1 and Sa2, but the rotation angle sensor may output a total of four electrical signals, which are two pairs of differential signals. In this case, by using a differential amplifier circuit as the signal amplifier 2, the two electrical signals S1 and S2 are input to the angle calculation unit 14, as in the first embodiment.

[0038] Embodiment 2 Next, an electric motor control device according to embodiment 2 will be described. In this case, the calculation of angle information in the angle calculation unit is different, but other parts are the same as those in embodiment 1. Fig. 7 is a flowchart showing the operation of angle calculation unit 14A according to embodiment 2. Fig. 8 is a waveform diagram explaining the operation of angle calculation unit 14A.

[0039] As shown in FIG. 7, in the angle calculation unit 14A, as in the first embodiment, the two electrical signals S1 and S2 are read (step ST1), the individual offset of the rotation angle sensor 3 is corrected for the electrical signals S1 and S2 (step ST2), and high-frequency noise of the electrical signals S1 and S2 is removed using an LPF (step ST3).

[0040] The electrical signals S1 and S2 are the same as those in the first embodiment. As shown in FIG. 8 , the electrical signal S1 is a sine signal (R sin θ) and the electrical signal S2 is a cosine signal (R cos θ). The electrical signals S1 (R sin θ) and S2 (R cos θ) intersect at two intersections B1 and B2 during one 360° rotation of the rotor. The intersection B1 in the positive region has θ = 45° and a signal value A1 (= R / √2), while the intersection B2 in the negative region has θ = 225° and a signal value A2 (= -R / √2). Within the regions of the two electrical signals S1 and S2, the region sandwiched between the two signal values ​​A1 and A2 (< A1) at the two intersections B1 and B2 is defined as an inner region α, and the region outside of this is defined as an end region β.

[0041] Next, the angle calculation unit 14A divides one rotation (360°) of the rotor into four regions D1, D2, D3, and D4 of 90° each for each of the electrical signals S1 and S2 based on the set conditional equation, and calculates the rotation angle θ by switching between the electrical signal S1 and the electrical signal S2 for each region based on the set calculation equation (step SST4).

[0042] The conditional expressions for each of the regions D1, D2, D3, and D4 are as follows: D1: A2≦S1≦A1, S2>0 D2: A2≦S2≦A1, S1>0 D3: A2≦S1≦A1, S2<0 D4: A2≦S2≦A1, S1<0 315° to 360° and 0° to 45° are continuous 90° intervals, and in this case, are divided into region D1 (315° to 45°), region D2 (45° to 135°), region D3 (135° to 225°), and region D4 (225° to 315°).

[0043] Then, based on the calculation formula set for each of the regions D1, D2, D3, and D4, the rotation angle θ is calculated using an asinine calculation. Here, the asinine table for region D1 (315° to 45°) is used as the asinine table (asinTb), which is the conversion table. The calculation formulas for calculating the rotation angles for each of the regions D1, D2, D3, and D4 are shown below. D1: θ = asinTb (S1) D2: θ = 90° - asinTb (S2) D3: θ = 180° - asinTb (S1) D4: θ = 270° + asinTb (S2)

[0044] Based on the above calculation formula, the electrical signal S1 is used in regions D1 and D3, and the electrical signal S2 is used in regions D2 and D4. Referring to Fig. 8, the electrical signal S1 is in the inner region α in regions D1 and D3, and the electrical signal S2 is in the inner region α in regions D2 and D4. Next, as in the first embodiment, the angle calculation unit 14A calculates the electrical angle θe based on the determined rotational angle θ (mechanical angle) of the rotor (step ST8).

[0045] In this embodiment as well, the electric signals S1 and S2 are switched in increments of 90° so as to eliminate the end region β. This allows the motor control device 100 to obtain the rotation angle θ with high precision, improving the control performance of the electric motor M. Even if the electric signals S1 and S2 before AD conversion exceed the AD conversion input range and there are gaps in the waveforms of the electric signals S1 and S2 after AD conversion in the end region β, the rotation angle θ is calculated excluding the end region β, so the rotation angle θ can be calculated with high precision without any problems.

[0046] In addition, in this embodiment, the angle calculation unit 14A divides one rotation of the rotor (360°) into four regions D1, D2, D3, and D4 of 90° each, and stores and uses a calculation formula set for each region, thereby enabling the calculation of the rotation angle θ to be performed with high precision and high speed.

[0047] It is to be noted that a hysteresis width may be provided for the values ​​A1 and A2 (:±R / √2) used in the conditional expressions for determining the regions D1, D2, D3, and D4. In step ST3, high-frequency noise in the electrical signals S1 and S2 is removed using an LPF, but the remaining noise can prevent chattering when the electrical signals S1 and S2 are switched.

[0048] An example of providing hysteresis widths will be described below with reference to Fig. 9. As shown in Fig. 9, hysteresis widths h1 and h2 are provided for the signal value A1 at the intersection B1 in the positive region of two electrical signals S1 and S2, and the signal value A2 at the intersection B2 in the negative region. That is, hysteresis widths h1 and h2 are provided for the boundary values ​​(signal values ​​A1 and A2) of the inner region α, so that the two boundary values ​​in the positive region are A1 and A12 (= A1 + h1), and the two boundary values ​​in the negative region are A2 and A22 (= A2 - h2).

[0049] For example, when transitioning from region D1 using electrical signal S1 to region D2 using electrical signal S2, if S1≧A12 (:A1+h1) is satisfied, the transition to region D2 will occur. However, in the reverse direction, i.e., from region D2 to region D1, S1≦A1 must be satisfied. Thus, after transitioning from region D1 to region D2, returning to region D1 requires a numerical change in electrical signal S1 equivalent to the hysteresis width h1. This makes it possible to suppress chattering when switching between electrical signals S1 and S2.

[0050] The hysteresis widths h1 and h2 are set according to the magnitude of noise remaining in the electrical signals S1 and S2 or the magnitude of chattering when the electrical signals S1 and S2 are switched. The angle calculation unit 14A may also adjust the hysteresis widths h1 and h2 according to the magnitude of chattering when the electrical signals S1 and S2 are switched. In other words, by adjusting the hysteresis widths h1 and h2 so as to reduce chattering, the switching of the electrical signals S1 and S2 is controlled stably and reliably.

[0051] Considering the hysteresis widths h1 and h2, the conditional expressions for the transitions between the regions D1, D2, D3, and D4 are as follows: D1 → D2: S1 ≥ A12, S2 > 0 D2 → D3: S2 ≤ A22, S1 > 0 D3 → D4: S1 ≤ A22, S2 < 0 D4 → D1: S2 ≥ A12, S1 < 0 D2 → D1: S1 ≤ A1, S2 > 0 D3 → D2: S2 ≥ A2, S1 > 0 D4 → D3: S1 ≥ A2, S2 < 0 D1 → D4: S2 ≤ A1, S1 < 0

[0052] Next, the hardware configuration of the control unit 10 according to each of the first and second embodiments will be described below. FIG. 9 is a diagram showing the hardware configuration of the control unit 10. The control unit 10 is composed of a processor 20 and a storage device 21. The processor 20 has an AD conversion function. The storage device 21 includes a volatile storage device (not shown) such as a RAM (Random Access Memory) and a non-volatile auxiliary storage device (not shown) such as a HDD (Hard Disk Drive) or an SSD (Solid State Drive). Note that a flash memory may be used as the non-volatile auxiliary storage device instead of the HDD.

[0053] The processor 20 executes a control program input from the storage device 21. The storage device 21 includes an auxiliary storage device and a volatile storage device. A control program 22 is input to the processor 20 from the auxiliary storage device via the volatile storage device. The processor 20 outputs data 23 such as calculation results to the volatile storage device of the storage device 21, and stores this data 23 in the auxiliary storage device via the volatile storage device as necessary.

[0054] 9 shows the control unit 10 being configured only with the processor 20 and the storage device 21, but the present invention is not limited to this and may also include the processor 20 and the storage device 21, as well as a triangular wave generator and a PWM circuit, which are dedicated circuits for PWM control. Also, the processor 20 may not have an AD conversion function, but may be provided with a separate integrated circuit for AD conversion.

[0055] Although exemplary embodiments are described in the present disclosure, the various features, aspects, and functions described in the embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are anticipated within the scope of the technology of the present disclosure. For example, variations in, addition to, or omission of at least one component are included.

[0056] Various aspects of the present disclosure are summarized below as appendices.

[0057] (Supplementary Note 1) An electric motor control device that drives an inverter to control an electric motor, comprising: an angle calculation unit that calculates rotor angle information based on an output of a magnetic rotation angle sensor provided in the electric motor, wherein the angle calculation unit acquires two electric signals, a sine signal and a cosine signal, based on the output of the rotation angle sensor, and calculates the angle information by using the sine signal and the cosine signal, by alternately switching between the sine signal and the cosine signal in increments of 90° so as to remove end regions including extreme values ​​in the sine signal and the cosine signal, and calculates a control command for the inverter using the angle information. (Supplementary Note 2) The electric motor control device according to Supplementary Note 1, wherein the end regions are outside an inner region sandwiched between signal values ​​of two intersections where the sine signal and the cosine signal intersect within one 360° rotation of the rotor, and the angle calculation unit calculates the angle information using only the inner regions of the sine signal and the cosine signal by alternately switching between the sine signal and the cosine signal in increments of 90°. (Supplementary Note 3) The electric motor control device according to Supplementary Note 2, wherein the angle calculation unit determines whether the rotation angle of the rotor based on either the sine signal or the cosine signal is within an angle range corresponding to one of the inner region and the end region, and alternately switches between the sine signal and the cosine signal in increments of 90° based on the determination result. (Supplementary Note 4) The electric motor control device according to Supplementary Note 2, wherein the angle calculation unit divides one rotation of 360° of the rotor into four regions of 90° each, and calculates the angle information by switching between the sine signal and the cosine signal for each region. (Supplementary Note 5) The electric motor control device according to Supplementary Note 4, wherein a hysteresis width is set for a boundary value of the inner region, which is the signal value of the two intersections, to suppress chattering when switching between the sine signal and the cosine signal. (Supplementary Note 6) The electric motor control device according to Supplementary Note 5, wherein the angle calculation unit adjusts the hysteresis width according to the magnitude of the chattering. (Supplementary Note 7) The electric motor control device according to any one of Supplementary Note 4 to Supplementary Note 6, wherein the angle calculation unit holds a calculation formula set for each of the divided regions, and calculates the angle information using the calculation formula.(Supplementary Note 8) The electric motor control device according to any one of Supplementary Notes 1 to 7, wherein an analog signal output from the rotation angle sensor is amplified, converted to digital form, and input to the angle calculation unit. (Supplementary Note 9) The electric motor control device according to any one of Supplementary Notes 1 to 8, wherein the angle calculation unit calculates the angle information after performing offset correction and high-frequency noise removal on the sine signal and the cosine signal. (Supplementary Note 10) The electric motor control device according to any one of Supplementary Notes 1 to 9, wherein the angle calculation unit holds a conversion table and derives the angle information from the sine signal and the cosine signal using the conversion table. (Supplementary Note 11) The electric motor control device according to any one of Supplementary Notes 1 to 10, wherein speed information of the electric motor is calculated based on the calculated angle information, and wherein output from the inverter to the electric motor is controlled based on the angle information and the speed information.

[0058] 1 inverter, 2 signal amplifier, 3 rotation angle sensor, 14, 14A angle calculation unit, 100 motor control device, A1, A2 signal value, B1, B2 intersection, D1 to D4 area, h1, h2 hysteresis width, M electric motor, S1, S2 electrical signal, Sa1, Sa2 analog signal, α inner area, β end area, θ rotation angle, ω rotation speed.

Claims

1. An electric motor control device that drives an inverter to control an electric motor, comprising: an angle calculation unit that calculates rotor angle information based on the output of a magnetic rotation angle sensor provided in the electric motor; the angle calculation unit obtains two electrical signals, a sine signal and a cosine signal, based on the output of the rotation angle sensor, and calculates the angle information by alternately switching between the sine signal and the cosine signal in 90° increments so as to remove end regions including extreme values ​​in the sine signal and the cosine signal; and the electric motor control device that calculates a control command for the inverter using the angle information.

2. The motor control device according to claim 1, wherein the end region is defined as the area outside an inner region sandwiched between signal values ​​at two intersections where the sine signal and the cosine signal intersect within one 360° rotation of the rotor, and the angle calculation unit calculates the angle information using only the inner region of the sine signal and the cosine signal by alternately switching between the sine signal and the cosine signal in 90° increments.

3. An electric motor control device as described in claim 2, wherein the angle calculation unit determines whether the rotation angle of the rotor based on either the sine signal or the cosine signal is within an angle range corresponding to one of the inner region and the end region, and alternates between the sine signal and the cosine signal in increments of 90° based on the determination result.

4. The motor control device according to claim 2, wherein the angle calculation unit divides one rotation of the rotor (360°) into four regions of 90° each, and calculates the angle information by switching between the sine signal and the cosine signal for each region.

5. The motor control device according to claim 4, wherein a hysteresis width is provided for the boundary values ​​of the inner region, which are the signal values ​​at the two intersections, to suppress chattering when switching between the sine signal and the cosine signal.

6. The motor control device according to claim 5, wherein the angle calculation unit adjusts the hysteresis width in accordance with the magnitude of the chattering.

7. An electric motor control device according to any one of claims 4 to 6, wherein the angle calculation unit holds a calculation formula set for each of the divided regions, and calculates the angle information using the calculation formula.

8. An electric motor control device according to any one of claims 1 to 7, wherein an analog signal output from the rotation angle sensor is amplified, converted into a digital signal, and input to the angle calculation unit.

9. The motor control device according to any one of claims 1 to 8, wherein the angle calculation unit performs offset correction and high frequency noise removal on the sine signal and the cosine signal, and then calculates the angle information.

10. An electric motor control device according to any one of claims 1 to 9, wherein the angle calculation unit holds a conversion table and derives the angle information from the sine signal and the cosine signal using the conversion table.

11. An electric motor control device according to any one of claims 1 to 10, which calculates speed information of the electric motor based on the calculated angle information, and controls the output from the inverter to the electric motor based on the angle information and the speed information.

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