Motor control device

Abstract

The invention provides a motor control device, which can improve the detection precision of the rotating motor angle of a motor through the AD value correction of converting an analog signal output by a rotation angle sensor for detecting the phase of the motor into a digital signal. The motor control device includes a rotational position detection unit having: a recording unit that records a plurality of sets of data composed of sine wave signals and cosine wave signals in phases of a motor included in digital signals; a correction necessity determination unit that determines whether or not the phase of the motor needs to be corrected on the basis of the plurality of group data; an ellipse approximation unit that performs ellipse approximation on the basis of the plurality of sets of data and calculates an ellipse constant when correction of the phase of the motor is required; a correction unit that corrects the sine wave signal and the cosine wave signal on the basis of elliptic constants; and a phase calculation unit that calculates a phase on the basis of the sine wave signal and the cosine wave signal corrected by the correction unit, and the plurality of sets of data are each allocated to a prescribed number of regions divided within a range of one or more electrical angles.

Description

Technical Field

[0001] The present invention relates to a motor control device. Background Art

[0002] In recent years, with the electrification of automobiles, vehicles using motors (electric motors) for main engines and auxiliary engines (such as brakes and power steering) have become increasingly common. In order to accurately control the motors, high-precision detection of the rotation angle is required.

[0003] Patent Document 1 describes a bearing equipped with a rotation sensor capable of detecting an absolute angle.

[0004] According to the technology described in Patent Document 1, error correction data can be measured in advance during bearing manufacture, recorded in a component with a correction data recording unit, and the absolute angle can be detected without calibration work after assembling the bearing.

[0005] Furthermore, Patent Document 2 describes a motor drive device that reduces speed fluctuation while maintaining the reproducibility of position information of a moving member of the motor drive device.

[0006] According to the technology described in Patent Document 2, ellipse parameters representing an ellipse approximating a Lissajous curve are calculated based on two phase-shifted sinusoidal signals output from a moving member of a motor drive device. The two sinusoidal signals are then corrected to make the ellipse a perfect circle. The motor drive device is controlled based on speed information representing the moving member's speed, which is obtained from the Lissajous curves of the corrected two sinusoidal signals. Prior art literature Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-353683 Patent Document 2: Japanese Patent Application Laid-Open No. 2011-125073 Summary of the Invention Problems to be solved by the invention

[0008] Here, in order to reduce costs, the motor angle sensor is required to detect the phase via a general-purpose ADC (Analog to Digital Converter).

[0009] General-purpose ADCs have temperature characteristics, and the AD value distorts over time. To address this AD value distortion, consider using a correction function for each channel of the ADC's AD value.

[0010] However, since correction of the AD value requires a certain amount of time, correction can be performed when the motor is powered on, but it is difficult to perform correction while the motor is being driven.

[0011] Patent Documents 1 and 2 do not describe a technique for correcting the AD value of a general-purpose ADC even during motor driving.

[0012] An object of the present invention is to realize a motor control device capable of correcting an AD value of a general-purpose ADC even during motor driving, thereby improving the detection accuracy of the rotational electrical angle of the motor. Technical means to solve the problem

[0013] In order to achieve the above-mentioned object, the present invention is constructed as follows.

[0014] A motor control device includes: a power conversion unit that converts direct current (DC) power into three-phase alternating current (AC) power and outputs the converted three-phase AC power to a motor; a rotation angle sensor that detects the phase of the motor; and an AD converter that converts an analog signal output from the rotation angle sensor into a digital signal. The motor control device also includes a rotation position detection unit having: a recording unit that records a plurality of sets of data consisting of a sine wave signal and a cosine wave signal in the phase of the motor included in the digital signal; a correction necessity determination unit that determines whether correction of the motor phase is necessary based on the plurality of sets of data; an ellipse approximation unit that, if correction of the motor phase is necessary, performs ellipse approximation based on the plurality of sets of data and calculates an ellipse constant; a correction unit that corrects the sine wave signal and the cosine wave signal based on the ellipse constant; and a phase calculation unit that calculates the phase based on the sine wave signal and the cosine wave signal corrected by the correction unit. The plurality of sets of data are each allocated to a predetermined number of regions within a range of at least one electrical angle revolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram showing the overall structure of the motor control device of the first embodiment. Figure 2 FIG. 4 is a diagram showing the internal structure of the rotation position detection unit 400 of the motor control device according to the first embodiment. Figure 3A This is a diagram illustrating the internal structure of the array buffer. Figure 3B This is a diagram illustrating the internal structure of the array buffer. Figure 3C This is a diagram illustrating the internal structure of the array buffer. Figure 3D This is a diagram illustrating the internal structure of the array buffer. Figure 4 This is a diagram illustrating the internal structure of the array buffer. Figure 5A This is a diagram showing an ellipse when the origin is not offset. Figure 5B This is a diagram showing a perfect circle when the origin is offset. Figure 6 This is a diagram showing the memory of the origin distance. Figure 7 This is a diagram of the internal structure of the calibration unit. Figure 8 This is a diagram showing the internal structure of the rotation position detection unit in the second embodiment. Figure 9 This is a diagram showing the array structure of stored data in the array buffer unit in the second embodiment. Figure 10 It is a diagram for explaining the operation of the ellipse approximation unit in the second embodiment. Figure 11A It is a diagram showing a line (wavy line) connecting the constant a'. Figure 11B It is a diagram showing a line (wavy line) connecting the constant b'. Figure 12 This is a functional block diagram of the ellipse approximation unit 430 in the second embodiment. Figure 13 This diagram shows ideal sine wave signals and cosine wave signals of an ADC (analog-to-digital converter). Figure 14 This is a schematic diagram showing sine wave signals and cosine wave signals when the median value is fixed but the amplitudes of the sine wave signals and cosine wave signals vary. Figure 15 This is an illustration of an elliptical orbit. DETAILED DESCRIPTION

[0016] Before describing the embodiments of the present invention, the principle of the present invention is first described.

[0017] Figure 13 This diagram shows ideal sine wave signals and cosine wave signals for an ADC (Analog-to-Digital Converter). There are three electrical angle error factors in detecting the electrical angle of the motor.

[0018] The first error factor is conversion error caused by the ADC's temperature characteristics. Although the ADC has an error correction function, it cannot be used for motor driving due to the processing time required.

[0019] The second error factor is the error caused by the performance deviation of the I / F (interface) of the ADC input circuit.

[0020] The third error factor is the error from the machining accuracy of the resolver.

[0021] While the values ​​of the first and second error factors are constant, the amplitudes of the sine and cosine wave signals fluctuate, causing distortion. This causes repeated fluctuations in the electrical angle within each cycle. This is defined as "distortion." Figure 14 This is a diagram showing a sine wave signal and a cosine wave signal when the median value is fixed but the amplitude of the sine wave signal and the cosine wave signal fluctuates. However, for ease of understanding, Figure 14 Emphasized.

[0022] The third error factor is the change in amplitude and median value within one cycle of the mechanical angle. Figure 14 In addition to the fluctuations in the amplitude shown, the median value also fluctuates, and both occur simultaneously. Therefore, the waveform of the fluctuating amplitude fluctuates as a whole. This is defined as "fluctuation."

[0023] The distortion caused by the aforementioned "distortion" and "ripple" is directly related to the generation of an error in the rotation angle, and causes torque fluctuation.

[0024] The present invention can eliminate the above-mentioned distortion, suppress torque fluctuation, and achieve stable control.

[0025] In summary, a distorted sine wave signal (distorted sine wave signal) can be expressed as y = a·sin(θ) + c, and a distorted cosine wave signal (distorted cosine wave signal) can be expressed as x = b·cos(θ) + d. a and b represent the fluctuation in amplitude, and c and d represent the fluctuation in median value.

[0026] Here, we know that if cos 2 θ+sin 2 θ = 1, then the distorted sine wave signal y and the distorted cosine wave signal x can be described as follows Figure 15 As shown by (xc) 2 / a 2 +(yd) 2 / b 2 = 1 represents an elliptical orbit. The major and minor axes of the ellipse are parallel to the x-axis and y-axis.

[0027] Therefore, we can collect multiple sets of (xi, yi) and perform elliptic approximation using the least squares method to determine the elliptic constants (a, b, c, d). Subtracting c from the cosine wave signal y results in a correction to a·cosθ. Dividing a·cosθ by a returns it to cosθ. The same applies to the sine wave signal y.

[0028] By performing the above-described processing, (cosθ, sinθ) that describes a perfect circle can be obtained, and distortion can be eliminated.

[0029] For a set of (xi, yi) corresponding to one mechanical angle rotation, the correlation of the ellipticity constants can be captured by repeating the ellipticity approximation, and the distortion can be eliminated by performing the same correction as for the distortion.

[0030] According to the principle of the present invention, it is possible to eliminate the error in the rotation angle, thereby eliminating the speed fluctuation, suppressing the torque variation, and achieving stable control.

[0031] Hereinafter, embodiments of the motor control device of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, the same elements are denoted by the same reference numerals, and their repeated descriptions will be omitted. Example

[0032] (Example 1) Figure 1 1 is a diagram showing the configuration of a motor control device 500 according to the first embodiment of the present invention.

[0033] Figure 1 The motor control device 500 shown is configured to correct distortion of AD values ​​caused by the temperature of the ADC 330 and to correct errors in the I / F circuit.

[0034] The motor control device 500 includes a motor 300, a motor drive device 100, and a rotational position detector 400. The motor drive device 100 includes a current control unit 110, an inverter (power converter) 130, a rotational position detector 400, an excitation unit 160, and an ADC 330. The battery 200 is the DC voltage source for the motor drive device 100. The DC power stored in the battery 200 is converted into three-phase AC power with variable voltage and frequency by the inverter 130 of the motor drive device 100. The inverter 130 supplies this three-phase AC power to the motor 300.

[0035] The motor 300 is a synchronous motor that is rotationally driven by a supply of three-phase AC power. In order to control the phase of the three-phase AC voltage according to the phase of the induced voltage of the motor 300, a resolver 320 as a rotation angle sensor is mounted on the motor 300.

[0036] Resolver 320 receives an excitation signal (sinωt) from excitation unit 160 and outputs two-phase signals Sn1 and Cn1, whose phases are shifted by 90° after amplitude modulation, to ADC (Analog-to-Digital Converter) 330 (where θ is the motor's rotation angle). ADC 330 converts the analog signal output from resolver (rotation angle sensor) 320 into a digital signal. Current control unit 110 calculates three-phase motor voltage command values ​​corresponding to the motor's rotation angle θ detected by rotational position detection unit 150, described later, so that the motor current values ​​(Iu, Iv, Iw) detected by current sensor 140 follow the current command values ​​generated by the host controller (not shown). Current control unit 110 then generates a drive signal using pulse width modulation (PWM) and outputs it to inverter 130.

[0037] The semiconductor switching elements constituting the main circuit of inverter 130 are turned on / off by a drive signal output from current control unit 110. Inverter 130 outputs three-phase voltages (Vu, Vv, Vw) to motor 300 according to a motor voltage command value.

[0038] ADC 330, an analog-to-digital converter, detects the excitation signal (sinωt) based on the two output signals (Sn1 (sinθsinωt) and Cn1 (cosθsinωt)) from resolver 320. ADC 330 then outputs a pair of a sine wave signal (sine wave component) Sn2 and a cosine wave signal (cosine wave component) Cn2, which are digital values ​​representing (sinθ, cosθ), to rotational position detection unit 400.

[0039] The combination of the sine wave signal Sn2 and the cosine wave signal Cn2 is actually distorted as (a·sinθ+c, b·cosθ+d). As described later, the rotation position detection unit 400 corrects the sine wave signal Sn2 and the cosine wave signal Cn2 to calculate the motor rotation angle θ.

[0040] Figure 2 FIG. 4 is an internal structure diagram of the rotation position detection unit 400. Figure 2 Array buffer (recording unit) 410 stores (records) multiple sets of data consisting of sine wave signal Sn2 and cosine wave signal Cn2 from ADC 330. Correction necessity determination unit 420 determines the data stored in array buffer 410 (determines whether the phase of motor 300 needs to be corrected based on the multiple sets of data) and transmits a necessity determination signal Sig1 to ellipse approximation unit 430.

[0041] When the necessity result signal Sig1 indicates that correction is necessary, the ellipse approximation unit 430 performs ellipse approximation based on the data stored in the array buffer 410 and calculates a set of ellipse constants (a, b, c, d).

[0042] The correction unit 440 corrects the sine wave signal Sn2 and the cosine wave signal Cn2 output from the ADC 330 so that they draw a perfect circular trajectory using the set of ellipticity constants (a, b, c, d) output from the ellipticity approximation unit 430. The correction unit 440 then outputs the perfect circular sine wave signal Sn3 and the cosine wave signal Cn3 to the motor rotation angle calculation unit 450. Figure 2 In FIG. 4 , the motor rotation angle calculation unit 450 is represented as atan2. The motor rotation angle calculation unit (phase calculation unit) 450 calculates the motor rotation angle θ based on the sine wave signal Sn3 and the cosine wave signal Cn3 output from the correction unit 440 (calculates the phase based on the sine wave component Sn2 and the cosine wave component Cn2 corrected by the correction unit 440).

[0043] Figures 3A to 3D 、 Figure 4 4 is a diagram illustrating the internal structure of the array buffer unit 410 .

[0044] At least four sets of sine wave signals Sn2 and cosine wave signals Cn2 are required to perform ellipse approximation, which are hereinafter referred to as set data.

[0045] Therefore, the motor rotation angle range of 0° to 360° is divided into 8 regions, and group data is collected. Let each region zi be z1, z2, ..., z8. Figure 3A This is a graph showing the situation when the sine wave signal Sn2 is used as the y coordinate and the cosine wave signal Cn2 is used as the x coordinate in the region zi. Figure 3A As shown, if group data is collected, then Figure 3B As shown, even if data overlap occurs at four locations, two on the x-axis and two on the y-axis, at least four valid data points can be guaranteed. Therefore, it is only necessary to determine whether data from eight regions is sufficient, making it easier to determine when data collection is complete. In other words, data can be prepared for groups that are appropriately dispersed across the angular range of 0 to 360°.

[0046] in addition, Figure 3C This is an example where group data accidentally overlaps at the boundary ends of area z1 and area z2, the boundary ends of area z3 and area z4, the boundary ends of area z5 and area z6, and the boundary ends of area z7 and area z8. Figure 3C As shown, since two ellipses can be assumed based on these set data, the ellipse cannot be determined.

[0047] Therefore, if Figure 3D As shown, it is preferable to tilt the boundary line (indicated by a dotted line) of each region zi at an appropriate angle βx, and intentionally shift the x-coordinate and y-coordinate of the boundary end.

[0048] Specifically, the ellipse approximation unit 430 extracts a plurality of consecutive sets of data from the set data spanning the mechanical angle, performs local ellipse approximation, calculates local ellipse constants, and then slides the local ellipse approximation to perform ellipse approximation across the entire mechanical angle, thereby calculating the correlation of ellipse constants across the entire mechanical angle. Ellipse approximation is achieved by making the boundary points of the dividing lines of each region zi inconsistent.

[0049] As described above, in the array buffer unit 410 , for region determination, group data corresponding to the determined region zi is collected in the array buffer unit 410 .

[0050] In addition, the following describes an example of dividing the motor rotation angle range of 0° to 360° into 8 areas, but the motor rotation angle range of 0° to 360° can also be equally divided into more than 8 areas (at least into 8 areas, for example, into 8 to 32 areas).

[0051] Figure 4 : is a diagram showing the data array in the array buffer 410. For regions z1 to z8, data ((y1, x1) to (y8, x8)) of the sine wave signal Sn2i and the cosine wave signal Cn2i are arrayed.

[0052] Next, the correction necessity determination unit 420 will be described.

[0053] The correction necessity determination unit 420 uses the data ((y1, x1) to (y8, x8)) of the sine wave signal Sn2i and the cosine wave signal Cn2i to determine whether correction is necessary by examining the difference between the maximum and minimum values ​​of the distance from the origin (origin distance) Ri, i.e., the amplitude. The origin distance Ri is calculated by (xi 2 +yi 2 ). In addition, i is a variable and is a number from 1 to 8 in the first embodiment.

[0054] like Figure 6 As shown, the calculated origin distance Ri may be stored in an appropriate memory (eg, a memory within the correction necessity determination unit 420 ) to determine the amplitude.

[0055] First, when the circle is a perfect circle and there is no deviation in the origin, the distance Ri between the origins is a fixed value of the circle radius, there is no fixed difference between the maximum and minimum values, and the amplitude is zero.

[0056] Second, in the case of an ellipse but no offset from the origin ( Figure 5A In the case of the ellipse shown in FIG, due to the existence of the major axis and the minor axis, the origin distance Ri fluctuates twice between the angle 0 and 360°, and an amplitude is generated at the maximum and minimum values ​​of the origin distance Ri. Third, in the case of a perfect circle but with an origin offset ( Figure 5B As shown in the case), the origin distance Ri fluctuates once between 0 and 360 degrees. Figure 5A As in the example shown, the amplitude is generated at the maximum and minimum values ​​of the origin distance Ri.

[0057] In this way, whether correction is necessary can be determined based on the amplitude of the origin distance Ri.

[0058] That is, when the amplitude of the origin distance Ri exceeds a predetermined value, it can be determined that correction is necessary, and when the amplitude of the origin distance Ri does not exceed the predetermined value, it can be determined that correction is not necessary.

[0059] The correction necessity determination unit 420 outputs the correction necessity determination result as a necessity result signal Sig1 to the ellipse approximation unit 430 .

[0060] Next, the operation of the ellipse approximation unit 430 will be described.

[0061] Ellipse approximation using multiple data (x k ,y k ) data and determine the constants (a, b, c, d) by the least squares method.

[0062] Regarding the ellipse approximation, the ellipse equations are organized into the following equations (1) to (4).

[0063] [Formula 1]

[0064] [Formula 2]

[0065] [Formula 3]

[0066] [Formula 4] x 2 +A·y 2 +B·x+C·t+D=0…(4)

[0067] The parameters are determined according to the general minimum approximation steps Step 1 to Step 3 shown below.

[0068] Step 1. Establish an evaluation formula using the following formula (5).

[0069] [Formula 5] G=∑ k {x 2 +A·y 2 +B·x+C·y+D} 2 =0…(5)

[0070] Step 2. Based on the parameters (A, B, C, D) you want to find, use the following formula (6 (6-1 to 6-4)) to partially differentiate the evaluation formula.

[0071] [Formula 6]

[0072] Step 3. Matrix the equation (7) to determine the parameters.

[0073] [Formula 7]

[0074] Then, the parameters (A, B, C, D) are obtained by the following formula (8), and the ellipticity constants (a', b', c', d') are determined by the following formulas (9-1) to (9-4).

[0075] [Formula 8]

[0076] [Formula 9] c'=-B / 2…(9-1) d'=-C / A / 2…(9-2) a' 2 =-D+c' 2 +d' 2 *A…(9-3) b' 2 =a' 2 / A…(9-4)

[0077] Elliptic constants are given a prime sign because they are approximate values.

[0078] The above-described processing is executed when the necessity result signal Sig1 indicates that correction is necessary, and nothing is executed when correction is not necessary.

[0079] Next, the correction unit 440 will be described.

[0080] Figure 7 This is a diagram showing the internal structure of the correction unit 440. Distortion occurs in the sine wave signals Sn2 and Cn2 output from the ADC 330. That is, as shown in the following equations (10) and (11), they can be expressed as signals x and y containing distortion.

[0081] [Equation 10] x=a·cosθ+c…(10)

[0082] [Equation 11] y=b·sinθ+d…(11)

[0083] The offset of the signal x is removed by the subtractor 440c, and the offset of the signal y is removed by the subtractor 440d of the correction unit 440. These are expressed by the following equations (12) and (13).

[0084] [Equation 12] x-c'=a·cosθ(c-c')…(12)

[0085] [Equation 13] y-d'=b·sinθ+(d-d')…(13)

[0086] Here, it can be regarded as c-c'=0 and d-d'=0, which can be expressed as the following equations (14) and (15).

[0087] [Equation 14] x-c'=a·cosθ…(14)

[0088] [Equation 15] y-d'=b·sinθ…(15)

[0089] Next, the amplitude is eliminated by multiplication and division calculators 440a and 440b. That is, the following equations (16) and (17) are performed.

[0090] [Equation 16] 1 / a'·(x-c')=(a / a')·cosθ...(16)

[0091] [Equation 17] 1 / b'·(y-d')=(b / b')·sinθ...(17)

[0092] Here, since a / a'=1 and b / b'=1 can be regarded, the following equations (18) and (19) can be obtained.

[0093] [Equation 18] 1 / a'·(x-c')=cosθ…(189)

[0094] [Equation 19] 1 / b'·(y-d')=sinθ…(19)

[0095] Equations (18) and (19) represent perfect circular orbits. That is, the distortion of the cosine wave and the sine wave can be corrected, and the correction unit 440 can obtain the distortion-corrected cosine wave signal Cn3 (cosθ) and the sine wave signal Sn3 (sinθ).

[0096] According to the first embodiment, the temperature characteristics of the ADC 330 can be eliminated, the accuracy of detecting the rotation angle can be improved, and the speed fluctuation can be reduced.

[0097] By capturing the trajectory of the sine and cosine wave signals, which have distortion caused by the temperature characteristics of ADC 330, as an ellipse, the constant of the ellipse can be extracted. By correcting the two signals based on the extracted constant, so-called inverse correction, the distortion caused by the temperature characteristics of ADC 330 can be negated.

[0098] Since the embodiment of the present invention is configured as described above, it is possible to realize a motor control device that can correct the AD value of a general-purpose ADC even during motor driving and improve the detection accuracy of the motor's rotational electrical angle.

[0099] (Example 2) Next, a second embodiment of the present invention will be described.

[0100] Figure 8 1 is a diagram showing the internal structure of the rotation position detector 400 in the second embodiment. The overall structure of the motor control device 500 in the second embodiment is the same as that in the first embodiment, so the diagram and detailed description are omitted.

[0101] The rotational position detector 400 of the second embodiment differs from the rotational position detector 40 of the first embodiment in the internal structures of the buffer 410 and the ellipse approximation unit 430. Furthermore, the ellipse approximation unit 430 of the second embodiment receives inputs of the sine wave signal Sn2 and the cosine wave signal Cn2, in addition to the data stored in the array buffer 410 and the necessity result signal Sig1 from the correction necessity determination unit 420.

[0102] Figure 9 1 is a diagram showing the array structure of stored data in the array buffer unit 410 in the second embodiment. In the second embodiment, a case where the number of pole pairs of the rotation sensor is 4 is taken as an example.

[0103] Ellipse approximation unit 430 collects group data over a range of one mechanical angle, distinguishing the pole pair numbers of the rotation sensor. (Specified pole pair numbers are assigned to each mechanical angle range, and group data is collected.) Furthermore, the electrical angle range of each pole pair is divided into eight. Because motor 300 may rotate while motor control device 500 is powered off, the pole pair number when powered on is set to 1st, and the numbers are assigned to 2nd, 3rd, and 4th in the forward direction.

[0104] The pole pair number is identified as follows: if x is near its maximum value and y changes from negative to positive, it is determined to be the next pole pair number. Conversely, if x is near its maximum value and y changes from positive to negative, it is determined to be the previous pole pair number.

[0105] From an electrical perspective, the sine wave signal Sn2 and the cosine wave signal Cn2 overlap on the same track, making it impossible to identify the pole pair number. However, the signal must pass through an electrical angle of 360°E before transitioning to the next pole pair number. By applying the condition of passing through 360°E, the pole pair number can be identified.

[0106] As described above, while dividing the pole pair numbers, group data (xi, yi) are collected in the same manner as in Example 1. The pole pair number at each moment is used as pole pair information Np.

[0107] Reference Figure 10 The operation of the ellipse approximation unit 430 in the second embodiment will be described.

[0108] Assuming the number of pole pairs is P, the relationship between the mechanical angle and the electrical angle is expressed by the following formula (20).

[0109] Electrical angle = mechanical angle × P…(20) Select data of a 360° amplitude region of continuous electrical angle to perform ellipse approximation to determine constants (a', b', c', d'). For example, Figure 10 This shows eight sets of data ((x3, y3) to (x10, y10)) selected, spanning pole pair number 1 and pole pair number 2. These sets of data have a width of 360° in electrical angle, allowing for elliptical approximation. While eight sets of data are shown as an example, this is not limited to eight; for example, any appropriate value between 8 and 16 can be selected.

[0110] The mechanical angle information is given to the constants (a′, b′, c′, d′) obtained here, and then the electrical angle θ is obtained by the motor rotation angle calculation unit 450 via the correction unit 440 .

[0111] Furthermore, add 360° to the electrical angle of the second pole pair, double the electrical angle of the third pole pair, and triple the electrical angle of the fourth pole pair. First, calculate the average value θi of each electrical angle θ and divide it by the number of pole pairs P to determine the mechanical angle θmi as the ellipticity constants (a', b', c', d').

[0112] In order to emphasize the position, it is assumed to be (a'(θmi), b'(θmi), c'(θmi), d'(θmi)).

[0113] The width of the electrical angle is continuously switched to 360 degrees, and the above-mentioned ellipticity constant is extracted over the range of one electrical angle cycle.

[0114] That is, (a'(θm1), b'(θm1), c'(θm1), d'(θm1)) are determined by (x1, y1)-(x8, y8), (a'(θm2), b'(θm2), c'(θm2), d'(θm2)) are determined by (x2, y2)-(x9, y9), and (a'(θm3), b'(θm3), c'(θm3), d'(θm3)) are determined by (x3, y3)-(x10, y10). Similarly, (a'(θm32), b'(θm32), c'(θm32), d'(θm32)) are determined by (x32, y32)-(x7, y7).

[0115] This allows the connection line of the ellipticity constants (a', b', c', d') corresponding to the mechanical angle θm to be understood.

[0116] Ellipse approximation unit 430 can also perform local ellipse approximation and calculate local ellipse constants by using the ellipse constant angle information as the average of the mechanical angles used in the ellipse approximation. By determining each mechanical angle of the local ellipse constant, a line connecting the constants corresponding to the mechanical angle is defined. Thus, by determining the mechanical angle at each point, the constants can be connected and converted into a waveform.

[0117] Figure 11A The dotted line L2 represents the line connecting the constant a' (wavy line). The solid line L1 is the line connecting the constant a assumed at this time. The wavy line L3 is formed by harmonic processing of the dotted line L2. The wavy line L3 after harmonic processing is roughly equal to the solid line L1 representing the fluctuation.

[0118] Figure 11B The solid line L1 represents the constant b assumed at this time.

[0119] The constants a and b are both assumed to have a 2% fluctuation. Although not shown, the constants c' and d' are also approximately the same.

[0120] As shown in the figure, higher harmonics are added to constants a' and b'. This is because the gain and offset will also move when the amplitude of the electrical angle moves 360 degrees, for example, because the starting point and the end point are inconsistent.

[0121] Since the lower-order waves are known, only higher-order harmonic processing is required. Since the period of the higher-order harmonic processing, which is related to the constant, is known, a sinusoidal approximation (sine wave approximation) is possible. By removing the higher-order harmonic signal and converting it into an easily processable approximate function, the mechanical angle at each point can be determined, and the elliptical constants can be connected to form a waveform.

[0122] By executing the processing so far, constants aa, bb, cc, dd, α, β, γ, and η shown in the following equations (21) to (24) can be determined.

[0123] a'=aa·sin(θm+α)+1···(21) b'=bb·sin(θm+β)+1···(22) c'=cc·sin(θm+γ)···(23) d'=dd·sin(θm+η)···(24) Figure 12 This is a functional block diagram of the ellipse approximation unit 430 in the second embodiment.

[0124] exist Figure 12 In the example, atan processing unit (inverse tangent processing unit) 431 calculates the electrical angle θ based on the sine wave signal Sn2 and the cosine wave signal Cn2. The calculated electrical angle θ is output to the adder 432. Based on the pole pair information Np from the array buffer 410, the offset θofst is output from the offset table 435 to the adder 432.

[0125] Adder 432 then adds electrical angle θ and offset θofst, providing the result to divider 433, which divides by the number of pole pairs p to calculate mechanical angle θm. Approximation processor 434 then applies equations (21) to (24) and outputs the instantaneous constants (a', b', c', d') to corrector 440.

[0126] According to the second embodiment, in addition to achieving the same effects as those of the first embodiment, fluctuations in the mechanical angle caused by eccentricity and inclination of the stator and rotor of the sensor can be corrected. Explanation of symbols

[0127] 100…motor drive device, 110…current control unit, 130…inverter, 140…current sensor, 160…excitation unit, 200…battery, 300…electric motor, 320…resolver, 330…ADC, 400…rotational position detection unit, 410…array buffer unit, 420…correction necessity determination unit, 430…ellipse approximation unit, 431…ATAN processing unit, 432…addition unit, 433…division unit, 434…approximation processing unit, 435…bias table, 440…correction unit, 440a, 440b…multiplication and division calculators, 440c, 440d…subtractor, 450…motor rotation angle calculation unit (phase calculation unit), 500…motor control device.

Claims

1. A motor control device comprising: a power conversion unit that converts direct current into three-phase alternating current and outputs the converted three-phase alternating current to the motor; a rotation angle sensor that detects a phase of the motor; and An AD converter converts an analog signal output from the rotation angle sensor into a digital signal. The motor control device is characterized in that it further includes a rotation position detection unit having: a recording unit that records a plurality of sets of data consisting of a sine wave signal and a cosine wave signal in the phase of the motor included in the digital signal; a correction necessity determination unit configured to determine whether correction of the phase of the motor is required based on the plurality of sets of data; an ellipse approximation unit for performing ellipse approximation based on the plurality of sets of data and calculating an ellipse constant when correction of the phase of the motor is required; a correction unit that corrects the sine wave signal and the cosine wave signal based on the ellipticity constant; and a phase calculation unit that calculates a phase based on the sine wave signal and the cosine wave signal corrected by the correction unit, The plurality of group data are respectively allocated to regions divided into a predetermined number within a range of one electrical angle or more.

2. The motor control device according to claim 1, wherein: The plurality of group data divides one electrical angle cycle into at least 8 regions.

3. The motor control device according to claim 2, wherein: In the plurality of sets of data, the dividing lines for dividing one electrical angle circle into at least 8 regions are offset from the x-axis and the y-axis by a predetermined angle.

4. The motor control device according to claim 3, wherein: The correction necessity determination unit calculates the distance from the origin for each of the plurality of data sets, and determines that correction is necessary when a difference between a maximum value and a minimum value of the distance from the origin exceeds a predetermined value.

5. The motor control device according to claim 4, wherein: The plurality of group data are respectively assigned predetermined pole pair numbers within a range of one mechanical angle. The ellipse approximation identifies the pole pair numbers, Take out multiple consecutive groups of data from the group data across the mechanical angle, perform local ellipse approximation to find the local ellipse constant, performing an elliptical approximation across the entire mechanical angle by sliding the local elliptical approximation, The correlation of the ellipticity constants in the entire range of the mechanical angle is obtained.

6. The motor control device according to claim 5, wherein: The ellipse approximation performs identification of the pole pair numbers as follows: When the cosine wave signal is positive, As the polarity of the sine wave signal changes from negative to positive, the pole pair numbering moves toward the positive rotation side. Conversely, as the sine wave signal changes from a positive value to a negative value, the pole pair number advances toward the reverse side.

7. The motor control device according to claim 5, wherein: In the ellipse approximation part, the number of the plurality of consecutive groups of data taken out is at least 8.

8. The motor control device according to claim 5, wherein: The ellipse approximation unit performs the local ellipse approximation to obtain the local ellipse constant as the average value of the mechanical angle using the angle information of the ellipse constant for ellipse approximation.

9. The motor control device according to claim 7, wherein: The ellipse approximation unit performs a sine wave approximation on the correlation of the ellipse constants.

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