JP4941259B2 - Absolute angle detection method and absolute angle detection device - Google Patents

Description

  The present invention relates to an absolute angle detection method and an absolute angle detection device in which an error of a rotation angle sensor is difficult to be reflected in an absolute angle.

  When the rotating body rotates a plurality of times, there is a case where it is desired to know an absolute angle that is a rotation angle for the plurality of rotations. For example, in the case of a rotating body that wants to know the absolute angle of 2 rotations (720 °) in the CW direction and 2 rotations (−720 °) in the CCW direction, the absolute angle is 1440 ° from −720 ° to + 720 ° as a whole. Since the width changes, it is necessary to be able to uniquely read the absolute angle within this width (referred to as an absolute angle detection range).

  On the other hand, known rotation angle sensors such as optical and magnetic sensors are configured to detect a half-rotation angle (0 ° to 180 °) or a single rotation angle (0 ° to 360 °). Even if the rotation exceeds the range, only the same value is repeated, and the absolute angle cannot be detected (this repeated angular width is called a sensor period).

  Therefore, as in Patent Documents 1 and 2, a plurality of rotation angle sensors are combined, and these rotation angle sensors are configured to rotate at different ratios relative to the rotation of the rotating body, and each rotation angle sensor detects. There has been proposed an absolute angle detection device capable of uniquely calculating the absolute angle of a rotating body from the difference in rotation angle. In these prior arts, a main gear is attached to the rotating body so that each rotation angle sensor rotates at a predetermined ratio with respect to the rotation of the rotating body, and a sensor gear meshing with the main gear is attached to each rotation angle sensor, The desired ratio is formed by the gear ratio of these gears.

  Further, as a main gear, an outer main gear having a predetermined number of teeth and an inner main gear having a smaller number of teeth are arranged on the rotating shaft of the rotating body, and a sensor gear meshed with the outer main gear and a sensor meshed with the inner main gear. It has been proposed to have the same number of gear teeth.

  It should be noted that the absolute angle detection device combined with such gears has a one-to-one correspondence with the combined state of the gears, so it is not necessary to save the data when the power is turned off in the memory. There is an advantage that the absolute angle can be detected immediately from the readings of the two rotation angle sensors at the time when the power is turned on, without supplementing information after the power is turned on.

Japanese Patent No. 3792718 (Japanese Patent Publication No. 11-500828) JP 2004-184264 A

  However, in the conventional absolute angle detection method, since the absolute angle is obtained by multiplying the difference between the rotation angles of the two sensor gears by a proportionality constant, the rotation angle detection error of the sensor gear is amplified and reflected in the absolute angle. . For example, if the rotation angle sensor attached to the sensor gear detects the rotation angle (A + γ) of the sensor gear, and A is the correct rotation angle and γ is an error, the detected rotation angle (A + γ) is greater than 1. When the rotation angle of the rotating body is calculated by multiplying by the proportionality constant, the error γ of the rotation angle sensor is also multiplied by the proportionality constant and reflected in the absolute angle of the rotating body.

  In addition, in the popular absolute angle detection device, the calculation for obtaining the absolute angle is performed by a very simple arithmetic device such as a microcomputer when compared with a personal computer. However, in this type of arithmetic device, the number of digits of numerical values handled is limited. ing. Therefore, the rotation angle detected by the rotation angle sensor has a small number of digits by A / D conversion, and is taken into a microcomputer or the like as a numerical value obtained by rounding (rounding off) the minimum digit, and is stored and used for calculation. Therefore, the rotation angle in the calculation is a numerical value with the minimum digit rounded. When the numerical value with the minimum digit rounded is multiplied, the rounding error is amplified. For this reason, when an absolute angle is obtained by multiplying the rotation angle by a proportional constant, a rounding error is greatly reflected in the absolute angle.

  Accordingly, an object of the present invention is to solve the above problems and provide an absolute angle detection method and an absolute angle detection device in which an error of a rotation angle sensor is less likely to be reflected in an absolute angle.

  Another object of the present invention is to provide an absolute angle detection method and an absolute angle detection device that can self-diagnose a failure of the absolute angle detection device.

  In order to achieve the above object, an absolute angle detection method of the present invention includes a first main gear having a number of teeth Za that is provided coaxially with a rotation shaft of a rotating body that is an absolute angle detection target and rotates integrally with the rotating body, A second main gear having a number of teeth smaller than that of the first main gear and provided coaxially with the rotation shaft of the rotating body and rotating integrally with the first main gear, and a number of teeth meshing with the first main gear. A first sensor gear of Zca, a second sensor gear of the number of teeth Zcb meshing with the second main gear, a first rotation angle sensor of sensor period Θ for detecting the rotation angle of the first sensor gear, and An absolute angle Φ of the rotating body from a second rotation angle sensor having a sensor period Θ for detecting the rotation angle of the second sensor gear, and rotation angle signals detected by the first rotation angle sensor and the second rotation angle sensor. Using an arithmetic unit for A sensor gear rotation angle detection step of detecting a rotation angle θca of the first sensor gear by the first rotation angle sensor and detecting a rotation angle θcb of the second sensor gear by the second rotation angle sensor; , Zb, Zca, Zcb and the absolute value calculated using the difference between the rotation angle θca detected by the first rotation angle sensor and the rotation angle θcb detected by the second rotation angle sensor. A temporary absolute angle calculating step for obtaining an angle KΦ, a first sensor cycle number detecting step for obtaining a repetition number Nca of the sensor cycle Θ in the first rotation angle sensor from the temporary absolute angle KΦ, and the first rotation angle sensor. An absolute angle calculation step for obtaining an absolute angle Φ from the detected rotation angle θca, the number of teeth Za, Zca, the sensor period Θ, and the number of repetitions Nca of the sensor period Θ. Is shall.

  A second sensor cycle number detection step for obtaining the number of repetitions Ncb of the sensor cycle Θ in the second rotation angle sensor from the temporary absolute angle KΦ, the rotation angle θcb and the number of teeth Zb, Zc detected by the second rotation angle sensor And calculating the difference between the absolute angle ΦR for reference and the absolute angle ΦR for reference, and the step of calculating the absolute angle for reference ΦR from the sensor cycle Θ and the number of repetitions Ncb of the sensor cycle Θ, A failure determination step of determining a failure when the difference exceeds a predetermined value.

  The absolute angle detection device according to the present invention includes a first main gear having a number of teeth Za that is provided coaxially with a rotation shaft of a rotating body that is an absolute angle detection target and rotates integrally with the rotating body, and the first main gear. A second main gear with the number of teeth Zb that is provided coaxially with the rotating shaft of the rotating body and rotates integrally with the first main gear, and a first sensor with the number of teeth Zca that meshes with the first main gear. A gear, a second sensor gear having the number of teeth Zcb meshing with the second main gear, a first rotation angle sensor having a sensor period Θ for detecting the rotation angle of the first sensor gear, and the second sensor gear. A second rotation angle sensor having a sensor period Θ for detecting a rotation angle, and an arithmetic device for obtaining an absolute angle Φ of the rotating body from rotation angle signals detected by the first rotation angle sensor and the second rotation angle sensor; The arithmetic device comprises: The rotation angle θca of the first sensor gear detected by the first rotation angle sensor is digitized and stored, and the rotation angle θcb of the second sensor gear detected by the second rotation angle sensor is digitized and stored. Sensor gear rotation angle storage means, first proportionality constant obtained from the number of teeth Za, Zb, Zca, Zcb, rotation angle θca detected by the first rotation angle sensor, and rotation angle θcb detected by the second rotation angle sensor And a temporary absolute angle calculation means for calculating a temporary absolute angle KΦ by using the difference between the first and second sensors, and a first sensor period for determining the number Nca of repetitions of the sensor period Θ in the first rotation angle sensor from the temporary absolute angle KΦ. The absolute angle Φ is obtained from the number-of-times detecting means, the rotation angle θca detected by the first rotation angle sensor, the number of teeth Za, Zca, the sensor period Θ, and the number Nca of repetitions of the sensor period Θ. Those having a diagonal calculation means.

  The arithmetic device includes a second sensor cycle number detection means for obtaining a number Ncb of repetitions of the sensor cycle Θ in the second rotation angle sensor from the temporary absolute angle KΦ, and a rotation angle θcb detected by the second rotation angle sensor. The reference absolute angle calculation means for making the reference absolute angle ΦR from the number of teeth Zb, Zc, the sensor period Θ, and the number of repetitions Ncb of the sensor period Θ, and the difference between the absolute angle Φ and the reference absolute angle ΦR And a failure determination means for determining a failure when the difference exceeds a predetermined value.

  The present invention exhibits the following excellent effects.

  (1) The error of the rotation angle sensor is not easily reflected in the absolute angle.

  (2) A failure of the absolute angle detection device can be self-diagnosed.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an absolute angle detector 1 as an embodiment of the present invention.

  As shown in the figure, the first main gear 2 with the number of teeth Za and the second main gear 3 with the number of teeth Zb (Za> Zb) are the rotation shafts (shafts) 100 of a rotating body (not shown) whose absolute angle is to be detected. Are provided so as to rotate integrally with the rotating body. The first main gear 2 is provided with a first sensor gear 4 having the number of teeth Zca that meshes with the first main gear 2. A magnet (not shown) is attached to the first sensor gear 4. A first rotation angle sensor 6 having a sensor period Θ for detecting the rotation angle θca of the first sensor gear 4 from the magnetic flux of the magnet is provided to face the first sensor gear 4. The second main gear 3 is provided with a second sensor gear 5 having the number of teeth Zcb that meshes with the second main gear 3. A magnet (not shown) is attached to the second sensor gear 5. A second rotation angle sensor 7 having a sensor period Θ for detecting the rotation angle θcb of the second sensor gear 5 from the magnetic flux of the magnet is provided to face the second sensor gear 5.

  In addition to the above configuration, the absolute angle detection device 1 includes an arithmetic device 8 that calculates the absolute angle of a rotating body that is an absolute angle detection target from the rotation angle signals detected by the first rotation angle sensor 6 and the second rotation angle sensor 7. .

  The first rotation angle sensor 6 and the second rotation angle sensor 7 have a magnetic detection element (not shown), and an arithmetic unit 8 provided with a microcomputer (not shown) for a rotation angle signal detected by the magnetic detection element. Configured to send to.

  The arithmetic unit 8 is composed of an A / D converter that converts the analog output of the first and second rotation angle sensors 6 and 7 into a digital output (numerical value), and a personal computer or microcomputer that stores the numerical value and performs arithmetic processing. Can do.

  As shown in FIG. 8, the arithmetic device 8 includes the following units.

  The sensor gear rotation angle storage means 81 digitizes and stores the rotation angle θca of the first sensor gear 4 detected by the first rotation angle sensor 6, and stores the second sensor gear 5 detected by the second rotation angle sensor 7. Is a means for numerically storing the rotation angle θcb.

  The temporary absolute angle calculation means 82 corrects the difference ΔθT between the stored rotation angle θca and the rotation angle θcb so as to fall within the range of the sensor cycle Θ, the first main gear tooth number Za, and the second main gear tooth number. This is a means for calculating a temporary absolute angle KΦ by calculating equation (1) using Zb, the first sensor gear tooth number Zca, and the first proportional constant obtained from the second sensor gear tooth number Zcb. Here, ΔθT correction means that in the case of sensor cycle Θ (−Θ / 2 to Θ / 2), when ΔθT is smaller than −Θ / 2, Θ is added to ΔθT, and when ΔθT is Θ / 2 or more. By subtracting Θ from ΔθT, Δθ falls within the sensor period Θ (−Θ / 2 to Θ / 2).

  The first sensor cycle number detection means 83 is a means for obtaining the number Nca of repetitions of the sensor cycle Θ in the first rotation angle sensor 6 from the temporary absolute angle KΦ by the equation (2). However, int in equation (2) is a function that returns an integer less than or equal to a given numerical value, for example, int (1.05) = 1, int (−1.05) = − 2.

  The absolute angle calculation means 84 includes the rotation angle θca detected by the first rotation angle sensor, the first main gear tooth number Za, the second proportional constant obtained from the first sensor gear tooth number Zca, the sensor cycle Θ, and this sensor. This is a means for obtaining the absolute angle Φ by the equation (3) using the number of repetitions Nca of the cycle Θ.

  The second sensor cycle number detection means 85 is a means for obtaining the number Ncb of repetitions of the sensor cycle Θ in the second rotation angle sensor 7 from the temporary absolute angle KΦ by the equation (4).

  The reference absolute angle calculation means 86 includes a rotation angle θcb detected by the second rotation angle sensor, a third proportional constant obtained from the second main gear tooth number Zb and the second sensor gear tooth number Zcb, a sensor cycle Θ, This is means for obtaining the reference absolute angle ΦR by the equation (5) using the number of repetitions Ncb of the sensor period Θ.

  The failure determination means 87 is a means for calculating a difference between the absolute angle Φ and the reference absolute angle ΦR and determining a failure when the difference exceeds a predetermined value.

  The arithmetic unit 8 includes the above-described units as software, and executes the steps described below based on the software to detect the absolute angle Φ and determine the failure of the absolute angle detection device 1.

  Hereinafter, the number of teeth Zca of the first sensor gear 4 and the number of teeth Zcb of the second sensor gear 5 are set to Zc = Za / 2 = Zca = Zcb, which is a half of the number of teeth Za of the first main gear 2. Consider a case where the cycle Θ of the first rotation angle sensor 6 and the second rotation angle sensor 7 is 180 °. In addition, this invention is not prescribed | regulated to each gear tooth number shown in figure. Moreover, by making the 1st sensor gear 4 and the 2nd sensor gear 5 into the same shape, one metal mold | die for manufacturing a sensor gear may be sufficient, and manufacturing cost can be held down.

  In order to carry out the absolute angle detection method of the present invention in the absolute angle detection device 1, the calculation device 8 executes the steps shown in FIG.

  As shown in FIG. 2, first, in the sensor gear rotation angle detection step S1, the rotation angle θca of the first sensor gear 4 is detected by the first rotation angle sensor 6, and the second sensor gear is detected by the second rotation angle sensor 7. 5 rotation angle θcb is detected. At this time, the sensor period of the first and second rotation angle sensors 6 and 7 is 180 °, but in this embodiment, it is assumed that from −90 ° to + 90 ° is detected. Therefore, every time the first sensor gear 4 makes one rotation, the first rotation angle sensor 6 repeatedly detects from −90 ° to + 90 ° twice. Since the number of teeth Zc of the first sensor gear 4 is ½ of the number of teeth Za of the first main gear 2, when the first main gear 2 rotates once, the first sensor gear 4 rotates twice, The rotation angle sensor 6 repeatedly detects from -90 ° to + 90 ° four times. Similarly, every second rotation of the second rotation angle sensor 7 in proportion to the gear ratio with the second main gear 2, the second rotation angle sensor 7 changes from -90 ° to + 90 ° by 2. XZb / Zc is repeatedly detected.

  The rotation angles θca and θcb detected by the rotation angle sensors 6 and 7 in this way are converted into numerical values of the number of digits that can be processed by the arithmetic device 8 by A / D conversion, and these numerical values are taken into the arithmetic device 8. Stored and used for computation in the following steps.

  In the provisional absolute angle calculation step S2, first, a difference ΔθT = θca−θcb between the rotation angle θca detected by the first rotation angle sensor 6 and the rotation angle θcb detected by the second rotation angle sensor 7 is calculated.

  Next, values outside the range are converted to set ΔθT to Δθ. Here, “out of range” means that ΔθT outside the period of the rotation angle sensors 6 and 7 is less than −90 ° or ΔθT exceeds 90 °. The conversion means adding 180 ° when ΔθT is smaller than −90 ° and subtracting 180 ° when larger than + 90 ° so that Δθ falls within the range of −90 ° to 90 °.

  Next, when the condition Zc = Za / 2 = Zca = Zcb is substituted into the first proportionality constant of the equation (1), the number of teeth Za of the first main gear 2 and the number of teeth Zb of the second main gear 3 are Is used as a denominator, and a first proportionality constant is obtained with the number of teeth Zc of the first rotation angle sensor 4 as a numerator. The first absolute constant is multiplied by Δθ to obtain a temporary absolute angle KΦ. That is,

Equation (6) expressed by Here, the temporary absolute angle KΦ is an absolute angle that is a final detection value in the prior art. As already mentioned, an error is inevitable in this absolute angle. In the present invention, this absolute angle is not used as a final detection value, but is used as a temporary absolute angle KΦ for detecting the number of sensor cycles.

  In the sensor cycle number detection step S3, the sensor cycle repetition number Nca in the first rotation angle sensor 6 is obtained from the temporary absolute angle KΦ. The number of repetitions refers to one end of the absolute angle detection range, for example, an absolute angle of −720 ° as a starting point (0 times), and the first rotation angle sensor 6 is a sensor as the first main gear 2 rotates only in the CW direction. It is equal to one added every time a cycle is completed. That is,

It is the integer part i of Formula (7) represented by these.

  Here, the characteristics of the rotation angle detected by the first rotation angle sensor 6 with respect to the rotation of the first sensor gear 4 and the rotation of the first main gear 2 (shaft) are shown in FIG.

  In FIG. 3A, the horizontal axis represents the rotation angle of the first sensor gear 4, and the vertical axis represents the rotation angle detected by the first rotation angle sensor 6. Each time the first sensor gear 4 makes one rotation, the rotation angle detected by the first rotation angle sensor 6 repeats for two cycles.

  In FIG. 3B, the horizontal axis represents the rotation angle of the first main gear 2, and the vertical axis represents the rotation angle detected by the first rotation angle sensor 6. Every time the first main gear 2 makes one rotation, the rotation angle detected by the first rotation angle sensor 6 repeats for four cycles.

  Finally, in the absolute angle calculation step S4, the rotation angle θca detected by the first rotation angle sensor 16 is added to the product of the sensor cycle repetition count Nca and the sensor cycle Θ = 180 ° in the first rotation angle sensor 6. The absolute angle Φca of the first sensor gear 4 is obtained, and the absolute angle Φca is multiplied by the gear ratio 1/2 of the first main gear 2 and the second sensor gear 4 = Zc / Za (second proportional constant) to obtain the absolute angle Φ Ask for. That is,

Equation (8) expressed by

  In the above arithmetic processing, the rotation angle θca detected by the first rotation angle sensor 6 is added to the product of the number of repetitions Nca of the sensor period in the first rotation angle sensor 6 and the sensor period Θ = 180 °, and the first sensor gear 4 Is obtained by multiplying the absolute angle Φca by the gear ratio 1/2 = Zc / Za between the first main gear 2 and the first sensor gear 4 to obtain the absolute angle Φ. Since the number of repetitions of the sensor cycle, the sensor cycle, and the number of teeth of the first main gear 2 and the first sensor gear 4 are not measured values with errors, no error in measurement occurs in these products. Further, since these products are products of integers, no rounding error occurs in the microcomputer. Therefore, the cause of the error is only the rotation angle θca detected by the first rotation angle sensor 6. For this reason, it is possible to perform detection with higher accuracy than in the conventional case in which the absolute angle is obtained by multiplying the difference between the rotation angles of the two sensor gears by a proportional constant.

  Here, the fact that the detection accuracy of the absolute angle is improved by the present invention will be verified.

  The absolute angle detection device 1 has the number of teeth Za of the first main gear 2 Za = 64, the number of teeth Zb = 58 of the second main gear 3, the number of teeth Zca = Zcb = 32 of the first sensor gear 4 and the second sensor gear 5, The sensor cycle Θ is 180 °, and the absolute angle detection range is ± 480 °. Further, it is assumed that the first rotation angle sensor 6 detects 0 ° and the second rotation angle sensor 7 also detects 0 ° at an absolute angle of 0 °. At this time, the first sensor gear 4 meshing with the first main gear 2 and the second sensor gear 5 meshing with the second main gear 3 rotate at different ratios with respect to increase / decrease in absolute angle (rotation of the first main gear 2). Detect corners.

  According to the principle of the absolute angle detection device 1, as shown in FIG. 4, the rotation angle (vertical axis) θca, θcb of each sensor gear detected with respect to the absolute angle (horizontal axis) given to the rotary shaft 100. The characteristics are different in slope and period. The absolute angle calculated based on Δθ obtained by converting the difference ΔθT between the rotation angle θca and the rotation angle θcb into the range of the sensor period 180 ° (−90 ° to + 90 °) is theoretically as shown in FIG. Is consistent with the given absolute angle.

  However, as described above, conventionally, since the absolute angle is obtained by multiplying Δθ by the first proportionality constant, the error is large. Specifically, as shown in FIG. 5, the absolute angle error by the conventional method exceeds ± 5 °. Therefore, the conventional method is unsuitable for applications in which the tolerance is narrower than ± 5 °.

  As shown in FIG. 6, the absolute angle Φz of the discrete first sensor gear 4 corresponding to the number of repetitions Nca of the sensor period of the first rotation angle sensor 6 starting from the absolute angle 0 ° is considered. That is, the absolute angle Φz = 0 ° when the number of repetitions Nca = 0, the absolute angle Φz = 180 ° of the first sensor gear 4 when the number of repetitions Nca = 1, and the absolute angle Φz = 2 × 180 when the number of repetitions Nca = 2. The absolute angle Φz of the staircase waveform is defined as °. When the rotation angle θca detected by the first rotation angle sensor 6 is superimposed on the flat portion of the staircase waveform, the absolute angle Φca of the continuous first sensor gear 4 to be obtained is obtained. The absolute angle Φca is obtained by multiplying the absolute angle Φca of the first sensor gear 4 by the gear ratio Zc / Za (second proportional constant) between the first main gear 2 and the first sensor gear 4. This figure is equivalent to the calculation performed in the absolute angle calculation step S4.

  Since the present invention performs the above calculation, the error is small. Specifically, as shown in FIG. 7, the absolute angle error according to the present invention is within ± 0.3 °. Therefore, the method of the present invention can be sufficiently applied to applications having an allowable error of about ± 0.3 °.

  Next, the failure determination method of the present invention will be described. The configuration of the absolute angle detection device 1 for this purpose is as shown in FIGS.

  In the embodiment of FIG. 1, the sensor cycle is multiplied by the number Nca of repetitions of the sensor cycle of the first rotation angle sensor 6 to obtain a discrete absolute angle Φz, and the rotation angle θca detected by the first rotation angle sensor 6 is added to this. Thus, the absolute angle Φca of the first sensor gear 4 was obtained. Further, the sensor cycle of the second rotation angle sensor 7 is multiplied by the number of repetitions Ncb of the sensor cycle of the second rotation angle sensor 7 to obtain a discrete absolute angle Φzb of the second sensor gear 5, and the second rotation is performed to this absolute angle Φzb. When the rotation angle θcb detected by the angle sensor 7 is added, the absolute angle Φcb of the second sensor gear 5 can be obtained.

  At this time, the rotation angle of the second main gear 3 obtained by multiplying the absolute angle Φcb of the second rotation angle sensor 7 by the gear ratio Zc / Zb (third proportionality constant) between the second main gear 3 and the second sensor gear 5. An absolute angle obtained by multiplying the absolute angle Φca of the first rotation angle sensor 6 by the gear ratio Zc / Za (second proportional constant) between the first main gear 2 and the first sensor gear 4 with Φ as a reference absolute angle ΦR. Compare with Φ. As long as the absolute angle detection device 1 operates normally, the absolute angle Φ and the reference absolute angle ΦR are substantially equal. However, if any failure occurs in the absolute angle detection device 1, a large difference appears between the absolute angle Φ and the reference absolute angle ΦR. Therefore, in the failure determination step, a difference between the absolute angle Φ and the reference absolute angle ΦR is calculated, and when the difference exceeds a predetermined value, it is determined as a failure.

  As shown in FIG. 9, the algorithm of the failure determination method is based on the second rotation angle sensor from the temporary absolute angle KΦ using the rotation angle θcb detected by the second rotation angle sensor 7 after the processing of FIG. The sensor cycle repetition count Ncb for obtaining the sensor cycle repeat count Ncb in step 7 and the sensor cycle repeat count Ncb in the second rotation angle sensor 7 are used to calculate the sensor cycle repeat count as shown in equation (9). Θcb detected by the second rotation angle sensor 7 is added to the product of Ncb and the sensor period Θ of 180 °, and the gear ratio Zc / Zb (second proportional constant) between the second main gear 3 and the second sensor gear 5 is added thereto. ) To calculate a reference absolute angle calculation step 93 to obtain a reference absolute angle ΦR, and to calculate a difference between the absolute angle Φ and the reference absolute angle ΦR, and to determine a failure when the difference exceeds a predetermined value Step 94.

  Here, the failure determination method of the present invention will be verified.

  The configuration of the absolute angle detection device 1 is the same as the verification of the detection accuracy of the absolute angle. When each step of the failure determination method is performed and the reference absolute angle ΦR is calculated, an error from the given absolute angle is within 0.3 °, and the measurement is performed in the same manner as the method for calculating the absolute angle Φ of the rotating body. The error was small. Therefore, failure determination can be performed with high accuracy. Next, the difference between the absolute angle Φ obtained above and the reference absolute angle ΦR was calculated, and a failure determination was performed. Here, since the error between the absolute angle Φ and the reference absolute angle ΦR was within ± 0.3 °, the predetermined value was ± 0.6 ° (± 0.3 ° × 2). When the difference between the absolute angle Φ obtained above and the reference absolute angle ΦR was calculated, the difference was within ± 0.6 ° and was within a predetermined value ± 0.6 °. Therefore, in the present embodiment, it is determined that the absolute angle detection device 1 is normal. The predetermined value is appropriately determined based on the measurement error of the absolute angle Φ and the reference absolute angle ΦR and the measurement accuracy required for the absolute angle detection device 1.

  According to such a failure determination method, the result from the rotation angle detection of the rotation angle sensor to the absolute angle calculation can be used as it is for failure determination, and no special measurement or calculation for failure determination is required, and it is accommodated in the microcomputer. This contributes to reducing the number of I / O ports to be used and the amount of programs.

  It goes without saying that each expression is not limited to the above-described embodiment, and the present invention includes a case where the function of the above-described embodiment is realized by a modified expression.

It is a block diagram of the absolute angle detection apparatus which implements the absolute angle detection method of this invention. It is the flowchart which showed the algorithm which an arithmetic unit performs in order to implement the absolute angle detection method of this invention. (A) is a rotation angle characteristic diagram showing the rotation angle detected by the first rotation angle sensor with respect to the rotation angle of the first sensor gear, and (b) is the first rotation angle with respect to the rotation angle of the first main gear. It is a rotation angle characteristic figure which showed the rotation angle which a sensor detects. It is a characteristic view of the detected rotation angle of each rotation angle sensor with respect to the absolute angle (horizontal axis) given to the rotation axis, and the theoretically obtained absolute angle (vertical axis). It is a characteristic view of the absolute angle (vertical axis) and error (vertical axis) detected by the conventional method with respect to the absolute angle (horizontal axis) given to the rotation axis. The rotation angle of the detected rotation angle sensor (vertical axis), the discrete absolute angle, and the continuous absolute angle (vertical axis) with respect to the absolute angle (horizontal axis) given to the rotation axis showing the absolute angle calculation principle of the present invention. FIG. It is a characteristic view of the absolute angle (vertical axis) and the error (vertical axis) detected by the present invention with respect to the absolute angle (horizontal axis) given to the rotation axis. It is a block block diagram of the arithmetic unit of the absolute angle detection apparatus of FIG. It is the flowchart which showed the algorithm which an arithmetic unit performs in order to implement the failure determination method of the absolute angle detection method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Absolute angle detection apparatus 2 1st main gear 3 2nd main gear 4 1st sensor gear 5 2nd sensor gear 6 1st rotation angle sensor 7 2nd rotation angle sensor 8 Arithmetic unit

Claims (4)

A first main gear having the number of teeth Za that is provided coaxially with the rotating shaft of the rotating body that is an absolute angle detection target and rotates integrally with the rotating body, and the rotating shaft of the rotating body that has fewer teeth than the first main gear. And a second main gear with the number of teeth Zb that rotates integrally with the first main gear, a first sensor gear with the number of teeth Zca that meshes with the first main gear, and a tooth that meshes with the second main gear A second sensor gear of several Zcb, a first rotation angle sensor of a sensor cycle Θ for detecting the rotation angle of the first sensor gear, and a sensor cycle Θ of detecting the rotation angle of the second sensor gear. Using a second rotation angle sensor, and an arithmetic device for obtaining an absolute angle Φ of the rotating body from rotation angle signals detected by the first rotation angle sensor and the second rotation angle sensor,
A sensor gear rotation angle detection step of detecting a rotation angle θca of the first sensor gear by the first rotation angle sensor and detecting a rotation angle θcb of the second sensor gear by the second rotation angle sensor;
It is calculated using the first proportionality constant obtained from the number of teeth Za, Zb, Zca, Zcb and the difference between the rotation angle θca detected by the first rotation angle sensor and the rotation angle θcb detected by the second rotation angle sensor. A provisional absolute angle calculating step for obtaining a provisional absolute angle KΦ;
A first sensor cycle number detection step for obtaining a repeat number Nca of the sensor cycle Θ in the first rotation angle sensor from the temporary absolute angle KΦ;
An absolute angle calculation step for obtaining an absolute angle Φ from the rotation angle θca detected by the first rotation angle sensor, the number of teeth Za, Zca, the sensor period Θ, and the number Nca of repetitions of the sensor period Θ. Absolute angle detection method. A second sensor cycle number detection step for obtaining the number of repetitions Ncb of the sensor cycle Θ in the second rotation angle sensor from the temporary absolute angle KΦ;
A reference absolute angle calculation step for setting a reference absolute angle ΦR from the rotation angle θcb detected by the second rotation angle sensor, the number of teeth Zb, Zc, the sensor period Θ, and the number of repetitions Ncb of the sensor period Θ;
A failure determination step of calculating a difference between the absolute angle Φ and the reference absolute angle ΦR and determining a failure when the difference exceeds a predetermined value;
The absolute angle detection method according to claim 1, further comprising: A first main gear having the number of teeth Za that is provided coaxially with the rotating shaft of the rotating body that is an absolute angle detection target and rotates integrally with the rotating body, and the rotating shaft of the rotating body that has fewer teeth than the first main gear. And a second main gear with the number of teeth Zb that rotates integrally with the first main gear, a first sensor gear with the number of teeth Zca that meshes with the first main gear, and a tooth that meshes with the second main gear A second sensor gear of several Zcb, a first rotation angle sensor of a sensor cycle Θ for detecting the rotation angle of the first sensor gear, and a sensor cycle Θ of detecting the rotation angle of the second sensor gear. A second rotation angle sensor; and an arithmetic device for obtaining an absolute angle Φ of the rotating body from a rotation angle signal detected by the first rotation angle sensor and the second rotation angle sensor,
The arithmetic unit is
The rotation angle θca of the first sensor gear detected by the first rotation angle sensor is digitized and stored, and the rotation angle θcb of the second sensor gear detected by the second rotation angle sensor is digitized and stored. Sensor gear rotation angle storage means for
It is calculated using the first proportionality constant obtained from the number of teeth Za, Zb, Zca, Zcb and the difference between the rotation angle θca detected by the first rotation angle sensor and the rotation angle θcb detected by the second rotation angle sensor. A provisional absolute angle calculating means for obtaining a provisional absolute angle KΦ;
First sensor cycle number detection means for obtaining the number of repetitions Nca of the sensor cycle Θ in the first rotation angle sensor from the temporary absolute angle KΦ;
An absolute angle calculation means for obtaining an absolute angle Φ from the rotation angle θca detected by the first rotation angle sensor, the number of teeth Za, Zca, the sensor period Θ, and the number Nca of repetitions of the sensor period Θ;
An absolute angle detection device comprising: The arithmetic unit is
Second sensor cycle number detection means for obtaining the number of repetitions Ncb of the sensor cycle Θ in the second rotation angle sensor from the temporary absolute angle KΦ;
A reference absolute angle calculating means for making a reference absolute angle ΦR from the rotation angle θcb detected by the second rotation angle sensor, the number of teeth Zb, Zc, the sensor period Θ, and the number of repetitions Ncb of the sensor period Θ,
A failure determination means for calculating a difference between the absolute angle Φ and the reference absolute angle ΦR, and determining a failure when the difference exceeds a predetermined value;
The absolute angle detection device according to claim 3, wherein:

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