JP2011107060A - Rotation angle detector and method of detecting rotation angle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for more accurate detection of the rotation angle of a rotor. <P>SOLUTION: A rotation angle detector includes first and second followers rotating in linking with rotation of a rotor; first and second rotation angle sensors detecting the respective rotation angles of the first and second followers; and a rotation angle calculating unit for calculating the rotation angle of the rotor, based on the detection results input by the first and second rotation angle sensors. The rotation angle calculation unit calculates a detection rotation angle, namely a rotation angle when the first and second rotation angle sensors detect the rotation angle of the first or second follower, based on detected results of the first and second rotation angle sensors (S506), estimates the amount of change in the angle of the rotor from a point in time when the first and second angle sensors detect the rotation angle to a point in time when the detected results are input (S508), and calculates the rotation angle of the rotor, based on the detected rotation angle and the amount of change (S509). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotation angle detection device and a rotation angle detection method.

Conventionally, an apparatus for detecting the rotation angle of a rotating body that can rotate over 360 degrees has been proposed.
For example, Patent Document 1 describes a rotation angle detection device configured as follows. That is, the rotatable rotating body has a gear having n teeth. This gear is engaged with a gear having m teeth and two gears having m + 1 teeth. The angles ψ and θ of these two gears are measured using two periodic angle sensors. This measurement is performed in a contact or non-contact manner. Each of these angle sensors is connected to an electronic evaluation circuit, and this evaluation circuit performs a calculation necessary for detecting the rotation angle φ of the rotating body. In the rotation angle detection device configured as described above, the two angle sensors, which are so-called absolute value sensors, supply the rotation angles ψ and θ of the two gears at the time of switch-on immediately after the rotation angle detection device is switched on. . The angle φ of the rotating body is detected from these angle values, the angle marks or the number of teeth of the gears of the rotating body, and the angle marks or the number of teeth of the two gears.

Japanese Patent No. 3792718

  As an angle sensor that measures the angle of a gear or a rotating body to which the gear is attached, it is conceivable to use a sensor that outputs a pulse width modulation signal having a duty ratio corresponding to the measured rotation angle at a predetermined period. In such a sensor, there is a delay of at least one cycle of the pulse width modulation signal until the data is transmitted to a calculation unit that calculates the rotation angle of the rotating body after measuring the angle of the gear or the like. Therefore, in order to detect the rotation angle of the rotating body with higher accuracy, it is important to calculate the rotation angle of the rotating body in consideration of the delay.

  For this purpose, the present invention is a rotation angle detection device for detecting the rotation angle of a rotating body, the first driven body and the second driven body rotating in conjunction with the rotation of the rotating body, First detection means for detecting the rotation angle of the first follower, second detection means for detecting the rotation angle of the second follower, the first detection means, and the second detection Rotation angle calculation means for calculating a rotation angle of the rotating body based on a detection result input by the means, wherein the rotation angle calculation means includes the first detection means and the second detection means. Detection that calculates a detected rotation angle that is a rotation angle at the time of detecting the rotation angle of the first follower or the second follower based on the detection results of the first detection means and the second detection means. An angle calculation means, the first detection means, and An estimation means for estimating the amount of change in the rotation angle of the rotating body from the time point detected by the second detection means to the input time point of the detection result, and the detected rotation calculated by the detection angle calculation means The rotation angle detection device calculates a rotation angle of the rotating body based on the angle and the amount of change estimated by the estimation means.

Here, the rotation angle calculation means calculates the rotation angle of the rotating body at a predetermined cycle, and the estimation means calculates the detected rotation angle at the current calculation time calculated by the detection angle calculation means. It is preferable to estimate the amount of change in the rotation angle of the rotating body based on the rotation angle difference from the detected rotation angle at the previous calculation time.
Moreover, it is preferable that the said estimation means estimates the variation | change_quantity of the rotation angle of the said rotary body by multiplying the predetermined coefficient to the said rotation angle difference.

The first detection unit and the second detection unit output a pulse width modulation signal having a duty ratio corresponding to the detected rotation angle at a predetermined cycle, and the predetermined coefficient is: It is preferable that the coefficient is dependent on a cycle in which the first detection unit and the second detection unit output the pulse width modulation signal and a cycle in which the rotation angle of the rotating body is calculated.
The rotating body includes a gear, the first driven body includes a first driven gear, and the second driven body has a number of teeth different from the number of teeth of the first driven gear. The first driven body and the second driven body have a second driven gear, and the first driven gear and the second driven gear are applied with a rotational force by the gear. It is preferable to rotate in conjunction with the rotation of the rotating body.

  From another point of view, the present invention provides a first driven body and a second driven body that rotate in conjunction with the rotation of the rotating body, and a first angle for detecting the rotation angle of the first driven body. A rotation angle detection method for the rotating body in a rotation angle detecting device comprising: a detecting means for detecting the rotation angle of the second driven body; and a second detecting means for detecting a rotation angle of the second driven body. The detected rotation angle, which is the rotation angle at the time when the second detection means detects the rotation angle of the first follower or the second follower, is determined by the first detection means and the second detection means. Calculate based on the detection result, estimate the amount of change in the rotation angle of the rotating body from the time point detected by the first detection means and the second detection means to the time point when the detection result is input, Based on the detected rotation angle and the amount of change, the rotation A rotation angle detection method characterized by calculating a rotation angle of the body.

Here, a rotation angle of the rotating body is calculated at a predetermined cycle, and the rotating body is based on a rotation angle difference between the detected rotation angle at the current calculation time and the detected rotation angle at the previous calculation time. It is preferable to estimate the amount of change in the rotation angle.
It is preferable that the amount of change in the rotation angle of the rotating body is estimated by multiplying the rotation angle difference by a predetermined coefficient.
The first detection unit and the second detection unit output a pulse width modulation signal having a duty ratio corresponding to the detected rotation angle at a predetermined cycle, and the predetermined coefficient is: It is preferable that the coefficient is dependent on a cycle in which the first detection unit and the second detection unit output the pulse width modulation signal and a cycle in which the rotation angle of the rotating body is calculated.

  According to the present invention, the rotation angle of the rotating body can be detected with higher accuracy than when the present invention is not employed.

It is a schematic block diagram of the rotation angle detection apparatus which concerns on this Embodiment. It is a figure which shows the relationship between the rotation angle of a rotary body, and the rotation angle of a 1st driven gear and a 2nd driven gear. It is a figure which shows the relationship between the rotation angle of a 1st driven gear and a 2nd driven gear, and the duty ratio of a pulse width modulation signal. It is a figure which shows the relationship between the rotation angle of a 1st driven gear and a 2nd driven gear, and the pulse width modulation signal which a 1st rotation angle sensor and a 2nd rotation angle sensor output. It is a flowchart which shows the procedure of the rotation angle calculation process of the rotary body which a rotation angle calculation part performs.

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a rotation angle detection device 1 according to the present embodiment.
The rotation angle detection device 1 is a device that detects the rotation angle of a rotating body 100 that is rotatably supported by a body frame of a vehicle such as an automobile.
The rotating body 100 is a rotating shaft to which, for example, a steering wheel is connected, and is rotatably supported by the housing via a bearing such as a ball bearing fixed to a housing (not shown) that is a member fixed to the main body frame. ing.

  By detecting the rotation angle of the rotating body 100 by the rotation angle detecting device 1, it is possible to detect the rotation angle of the steering wheel connected to the rotating body 100, and thus to grasp the traveling direction of the vehicle on which the steering wheel is mounted. It becomes possible. The detection result of the rotation angle detection device 1 is used in various control devices such as a device that performs route guidance and a device that changes the hardness of the suspension according to the steering angle.

Below, the rotation angle detection apparatus 1 is explained in full detail.
The rotation angle detection device 1 includes a gear 101 that is an example of a gear attached to the rotating body 100, a first driven gear 111 that is an example of a first driven gear that meshes with the gear 101, and a second that meshes with the gear 101. And a second driven gear 121 as an example of the driven gear. For example, the first driven gear 111 is rotatable with respect to the housing by being attached to the first rotation shaft 110 that is rotatably supported by the housing. The second driven gear 121 is also rotatable with respect to the housing, for example, by being attached to the second rotating shaft 120 that is rotatably supported by the housing. The first driven gear 111 and the first rotating shaft 110 constitute an example of a first driven body, and the second driven gear 121 and the second rotating shaft 120 constitute an example of a second driven body. Constitute.

FIG. 2 is a diagram illustrating the relationship between the rotation angle of the rotating body 100 and the rotation angles of the first driven gear 111 and the second driven gear 121.
The number of teeth of the gear 101 is n, the number of teeth of the first driven gear 111 is m, and the number of teeth of the second driven gear 121 is (m + 1). Then, the relationship between the number of teeth of the gear 101 and the number of teeth of the first driven gear 111 and the relationship between the number of teeth of the gear 101 and the number of teeth of the second driven gear 121 are taken into account, and the first driven gear 111 is taken into consideration. 2 and the number of teeth of the second driven gear 121 is (m + 1), the rotation angle of the rotating body 100 and the first driven gear 111, as shown in FIG. The figure which shows the relationship with the rotation angle of the 2nd driven gear 121 can be obtained. It can be exemplified that n is 81 and m is 21.

Further, the rotation angle detection device 1 includes a first rotation angle sensor 112 as an example of first detection means for detecting the rotation angle of the first driven gear 111. The first rotation angle sensor 112 is arranged outside the first driven gear 111 in the radial direction of rotation, and a plurality of first rotation angle sensors 112 are formed in the teeth of the first driven gear 111 or in the circumferential direction of the first rotary shaft 110. Based on the angle mark, the rotation angle of the first driven gear 111 is detected.
Similarly, the rotation angle detection device 1 has a second rotation angle sensor 122 as an example of second detection means for detecting the rotation angle of the second driven gear 121. The second rotation angle sensor 122 is disposed outside the second driven gear 121 in the rotation radial direction, and a plurality of second rotation angle sensors 122 are formed in the circumferential direction of the second driven gear 121 or the second rotation shaft 120. Based on the angle mark, the rotation angle of the second driven gear 121 is detected.
Then, the rotation angle detection device 1 is based on the output values from the first rotation angle sensor 112 and the second rotation angle sensor 122, in other words, by the first rotation angle sensor 112 and the second rotation angle sensor 122. A rotation angle calculation unit 150 (see FIG. 1) is provided as an example of a rotation angle calculation unit that calculates the rotation angle of the rotating body 100 based on the input detection result.

The first rotation angle sensor 112 and the second rotation angle sensor 122 respectively generate a pulse width modulation signal PWM having a duty ratio corresponding to the detected rotation angle of the first driven gear 111 or the second driven gear 121. Output at a predetermined cycle.
FIG. 3 is a diagram showing the relationship between the rotation angles of the first driven gear 111 and the second driven gear 121 and the duty ratio of the pulse width modulation signal PWM.
As shown in FIG. 3, the first rotation angle sensor 112 and the second rotation angle sensor 122 respectively set the rotation angles 0 to 360 degrees of the first driven gear 111 or the second driven gear 121 as duty cycles. It is converted into a pulse width modulation signal PWM having a ratio of 5% to 95% and output.

FIG. 4 shows the relationship between the rotation angle of the first driven gear 111 and the second driven gear 121 and the pulse width modulation signal PWM output from the first rotation angle sensor 112 and the second rotation angle sensor 122. FIG.
As shown in FIG. 4, the first rotation angle sensor 112 generates a pulse width modulation signal PWMA having a PWM signal ON (High) time PWMA_ON corresponding to the rotation angle of the first driven gear 111 at a predetermined cycle. The second rotation angle sensor 122 outputs a pulse width modulation signal PWMB having a PWM signal ON (High) time PWMB_ON corresponding to the rotation angle of the second driven gear 121, with a predetermined period PWMB_T. To output.

  The rotation angle calculation unit 150 is an arithmetic logic operation circuit including a CPU, a ROM, a RAM, and the like. The rotation angle calculation unit 150 receives the pulse width modulation signals PWMA and PWMB output from the first rotation angle sensor 112 and the second rotation angle sensor 122, and turns ON (High) pulses of the pulse width modulation signals PWMA and PWMB. Recognize the time. More specifically, the rotation angle calculation unit 150 includes two timer counters for measuring the time of ON (High) pulses of the pulse width modulation signals PWMA and PWMB. Each timer counter starts at the rising edge of the pulse width modulation signal PWMA or PWMB, stops at the falling edge, captures the value of the counter during that time into the capture register, and clears the counter. Then, the rotation angle calculation unit 150 reads the latest ON pulse times of the pulse width modulation signals PWMA and PWMB captured in the capture register at a predetermined cycle T (see FIG. 4), and based on this time Then, a calculation process for calculating the rotation angle φ of the rotating body 100 is performed. FIG. 4 illustrates the period (PWMA_T and PWMB_T) and timing at which the first rotation angle sensor 112 and the second rotation angle sensor 122 detect the rotation angle.

  As shown in FIG. 4, the first rotation angle sensor 112 and the second rotation angle sensor 122 detect the rotation angle of the first driven gear 111 or the second driven gear 121, and the detection result is subjected to pulse width modulation. When the signals PWMA and PWMB are used for output, the first rotation angle sensor 112 and the second rotation angle sensor 122 detect the rotation angle, and the detection result (counter value) is captured and recognized by the rotation angle calculation unit 150. Until then, there is a delay of at least one period of the pulse width modulation signal. Therefore, even if the rotation angle calculation unit 150 calculates the rotation angle of the rotating body 100 based on the latest rotation angle data, the calculation result is the first rotation angle sensor 112 and the second rotation angle. This is the rotation angle when the sensor 122 detects the rotation angle. Therefore, the rotation angle calculation unit 150 according to the present embodiment calculates the rotation angle of the rotating body 100 as follows in consideration of such points.

Hereinafter, the rotation angle calculation process of the rotating body 100 performed by the rotation angle calculation unit 150 will be described using a flowchart.
FIG. 5 is a flowchart showing the procedure of the rotation angle calculation process of the rotating body 100 performed by the rotation angle calculation unit 150. The rotation angle calculation unit 150 performs this rotation angle calculation process at the above-described period T.
First, the rotation angle calculation unit 150 calculates the rotation angle θA of the first driven gear 111 (step 501). This is a process of calculating by reading the PWM signal ON time PWMA_ON corresponding to the latest rotation angle of the first driven gear 111 taken into the capture register and substituting it into the following equation (1).
θA = (PWMA_ON−PWMA_T × 0.05) / (PWMA_T × 0.9) × K1 (1)
Here, K1 is a coefficient for converting the pulse width modulation signal PWMA into the rotation angle θA, and is a coefficient depending on the width of the duty ratio used for the pulse width modulation signal PWMA and the maximum rotation angle of 360 degrees. For the period PWMA_T, a value stored in advance in the ROM is read and substituted into the equation (1).

Next, the rotation angle calculation unit 150 calculates the rotation angle θB of the second driven gear 121 (step 502). This is a process of calculating by reading the PWM signal ON time PWMB_ON corresponding to the latest rotation angle of the second driven gear 121 captured in the capture register and substituting it into the following equation (2).
θB = (PWMB_ON−PWMB_T × 0.05) / (PWMB_T × 0.9) × K2 (2)
Here, K2 is a coefficient for converting the pulse width modulation signal PWMB into the rotation angle θB, and is a coefficient depending on the width of the duty ratio used for the pulse width modulation signal PWMB and the maximum rotation angle of 360 degrees. For the period PWMB_T, a value stored in advance in the ROM is read and substituted into the equation (2).
In the present embodiment, the relationship between the width of the duty ratio used for pulse width modulation signal PWMB and the maximum rotation angle 360 degrees is the relationship between the width of the duty ratio used for pulse width modulation signal PWMA and the maximum rotation angle 360 degrees. Since the relationship is the same, it is preferable that K2 = K1.

Next, the rotation angle calculation unit 150 calculates an angle difference ΔθAB between the rotation angle θA of the first driven gear 111 and the rotation angle θB of the second driven gear 121 (step 503). This is a process of calculating by subtracting the rotation angle θB calculated in step 502 from the rotation angle θA calculated in step 501 (ΔθAB = θA−θB).
Thereafter, the rotation angle calculation unit 150 determines whether or not the angle difference ΔθAB calculated in step 503 is smaller than 0 degrees (deg) (step 504). If the determination in step 504 is affirmative, the value obtained by adding 360 degrees to the angle difference ΔθAB calculated in step 503 is replaced with ΔθAB (ΔθAB = ΔθAB + 360) (step 505), and the process proceeds to step 506. On the other hand, if a negative determination is made in step 504, the process proceeds to step 506.

In step 506, the rotator 100 before correction is calculated from the latest pulse width modulation signal PWMA output from the first rotation angle sensor 112 and the latest pulse width modulation signal PWMB output from the second rotation angle sensor 122. The rotation angle φ ′ is calculated. This is a process of calculating by the following equation (3).
φ ′ = ΔθAB × K3 (3)
Here, K3 is a coefficient for converting the angle difference ΔθAB between the rotation angle θA of the first driven gear 111 and the rotation angle θB of the second driven gear 121 into the rotation angle φ ′ of the rotating body 100. , The number of teeth of the first driven gear 111, the number of teeth of the second driven gear 121, and the coefficient depending on 360 degrees that is the detection angle of the first rotation angle sensor 112 and the second rotation angle sensor 122 It is.

  Thereafter, the rotation angle calculation unit 150 calculates the amount of change Δφ in the rotation angle of the rotating body 100 for one cycle of the calculation process (step 507). This is from the rotation angle φ ′ (n) of the rotating body 100 before correction calculated in step 506 in the current (n-th) flow before the correction calculated in step 506 in the previous (n−1) -th flow. Is calculated by subtracting the rotation angle φ ′ (n−1) of the rotating body 100 (Δφ = φ ′ (n) −φ ′ (n−1)).

After that, the rotation angle calculation unit 150 detects the rotation angle after the first rotation angle sensor 112 and the second rotation angle sensor 122 detect the rotation angle until the data is taken into the rotation angle calculation unit 150 (from the detection time point) The rotation angle of the rotating body 100 that changes until the detection result is input is calculated, and the amount of change is set as the delay correction amount α (step 508). This is a process calculated by the following equation (4).
α = Δφ × K4 (4)
Here, K4 is a coefficient for converting the amount of change in the rotation angle of the rotator 100 into the delay correction amount α, the processing interval (cycle T) of the rotation angle calculation process, the first rotation angle sensor 112 and the first rotation angle. 2 is a coefficient depending on the period (PWMA_T and PWMB_T) in which the rotation angle sensor 122 detects the rotation angle. For example, when the cycle T of the calculation process performed by the rotation angle calculation unit 150 is n times the detection cycle (PWMA_T and PWMB_T) of the first rotation angle sensor 112 and the second rotation angle sensor 122, The value is 1 / n. More specifically, the period T of the calculation process performed by the rotation angle calculation unit 150 is 10 ms, that is, the amount of change in the rotation angle of the rotating body 100 for 10 ms is calculated in step 507, and the first rotation angle sensor 112 and When the detection period (PWMA_T and PWMB_T) of the second rotation angle sensor 122 is 1 ms, the value of the coefficient K4 is set to 1/10.

  Thereafter, the rotation angle calculation unit 150 calculates the corrected rotation angle φ of the rotating body 100 (step 509). This is a process of calculating by adding the delay correction amount α calculated in step 508 to the rotation angle φ ′ of the rotating body 100 before correction calculated in step 506 (φ = φ ′ + α). And the rotation angle calculation part 150 calculates rotation angle (phi) of the rotary body 100 at the time of a calculation by this rotation angle calculation process.

  As described above, in the rotation angle detection device 1 according to the present embodiment, after the first rotation angle sensor 112 and the second rotation angle sensor 122 detect the rotation angle, the data is the rotation angle calculation unit 150. The rotation angle φ of the rotating body 100 is calculated in consideration of the delay until the rotation is taken in, so that the rotation angle φ of the rotating body 100 can be detected with high accuracy.

In the embodiment described above, the delay correction amount α is calculated in step 508 based on the amount of change Δφ in the rotation angle of the rotating body 100 for one cycle of the calculation process calculated in step 507. However, when the angular velocity ω (deg / s) of the rotating body 100 can be grasped, the delay correction amount α may be calculated by the following equation (5).
α = ω × PWMA_T (or PWMB_T) (5)
That is, when the angular velocity ω of the rotating body 100 is 100 deg / s and the detection periods (PWMA_T and PWMB_T) of the first rotation angle sensor 112 and the second rotation angle sensor 122 are 1 ms, α = 100 × 0. .001 = 0.1 (deg).
Even in such a case, the rotation angle φ of the rotating body 100 can be detected with high accuracy.

DESCRIPTION OF SYMBOLS 1 ... Rotation angle detection apparatus, 100 ... Rotating body, 101 ... Gear, 110 ... 1st rotating shaft, 111 ... 1st driven gear, 112 ... 1st rotating angle sensor, 120 ... 2nd rotating shaft, 121 ... second driven gear, 122 ... second rotation angle sensor, 150 ... rotation angle calculator

Claims (9)

A rotation angle detection device for detecting a rotation angle of a rotating body,
A first driven body and a second driven body that rotate in conjunction with the rotation of the rotating body;
First detection means for detecting a rotation angle of the first follower;
Second detection means for detecting a rotation angle of the second follower;
A rotation angle calculation means for calculating a rotation angle of the rotating body based on the detection result input by the first detection means and the second detection means;
With
The rotation angle calculation means includes
A detected rotation angle that is a rotation angle at the time when the first detection means and the second detection means detect the rotation angle of the first follower or the second follower, and the first detection means and the second detection means. Detection angle calculation means for calculating based on the detection result of the second detection means;
An estimation means for estimating a change amount of the rotation angle of the rotating body from the time point detected by the first detection means and the second detection means to the input time point of the detection result;
Have
A rotation angle detection device that calculates a rotation angle of the rotating body based on the detected rotation angle calculated by the detection angle calculation means and the change amount estimated by the estimation means. The rotation angle calculation means calculates the rotation angle of the rotating body at a predetermined cycle,
The estimation means calculates a change in the rotation angle of the rotating body based on a rotation angle difference between the detected rotation angle at the current calculation time calculated by the detection angle calculation means and the detected rotation angle at the previous calculation time. The rotation angle detection device according to claim 1, wherein the amount is estimated.   The rotation angle detection device according to claim 2, wherein the estimation unit estimates the amount of change in the rotation angle of the rotating body by multiplying the rotation angle difference by a predetermined coefficient. The first detection means and the second detection means output a pulse width modulation signal having a duty ratio corresponding to the detected rotation angle at a predetermined period,
The predetermined coefficient is a coefficient depending on a cycle in which the first detection unit and the second detection unit output the pulse width modulation signal and a cycle in which the rotation angle of the rotating body is calculated. The rotation angle detection device according to claim 3. The rotating body has a gear;
The first driven body has a first driven gear;
The second driven body has a second driven gear having a number of teeth different from the number of teeth of the first driven gear;
The first driven body and the second driven body rotate in conjunction with the rotation of the rotating body by applying a rotational force to the first driven gear and the second driven gear by the gear. The rotation angle detection device according to claim 1, wherein the rotation angle detection device is a rotation angle detection device. A first driven body and a second driven body that rotate in conjunction with the rotation of the rotating body;
First detection means for detecting a rotation angle of the first follower;
Second detection means for detecting a rotation angle of the second follower;
A rotation angle detection method for the rotating body in a rotation angle detection device comprising:
A detected rotation angle that is a rotation angle at the time when the first detection means and the second detection means detect the rotation angle of the first follower or the second follower, and the first detection means and the second detection means. Calculation based on the detection result of the second detection means,
Estimating the amount of change in the rotation angle of the rotating body from the time point detected by the first detection means and the second detection means until the time when the detection result is input,
A rotation angle detection method, comprising: calculating a rotation angle of the rotating body based on the detected rotation angle and the amount of change.   The rotation angle of the rotating body is calculated at a predetermined cycle, and the rotation angle of the rotating body is based on the rotation angle difference between the detected rotation angle at the current calculation time point and the detected rotation angle at the previous calculation time point. The rotation angle detection method according to claim 6, wherein the amount of change is estimated.   The rotation angle detection method according to claim 7, wherein the amount of change in the rotation angle of the rotating body is estimated by multiplying the rotation angle difference by a predetermined coefficient. The first detection means and the second detection means output a pulse width modulation signal having a duty ratio corresponding to the detected rotation angle at a predetermined period,
The predetermined coefficient is a coefficient depending on a cycle in which the first detection unit and the second detection unit output the pulse width modulation signal and a cycle in which the rotation angle of the rotating body is calculated. The rotation angle detection method according to claim 8.

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