JP3126843B2 - Rotation angle detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation angle detecting device for detecting a mechanical rotation angle of a rotating body such as a motor.

[0002]

2. Description of the Related Art In a conventional apparatus of this kind, a plurality of position sensors are arranged at regular intervals along the rotation direction of a rotating body such as a motor, and a plurality of bits are rotated based on output signals from the respective position sensors. One that generates an angle signal is known. FIGS. 4 and 5 are a circuit diagram and a timing chart, respectively, for generating a rotation angle signal when three position sensors are used, wherein # 1 to # 3 are output signals from the respective position sensors and A _{6 to} A. Reference numeral ₄ denotes a 3-bit rotation angle signal (however, A _{4 is the} least significant bit).

In FIG. 4, 1 to 6 are inverter gates, 7 to 10 are 3-input NAND gates, 11 and 12 are 2-input NOR gates, and when any two of # 1 to # 3 are at H level, the NAND gate 10 When the output (A ₄ ) is at the H level, and when # 1 is at the H level and # 3 is at the H level, the output (A ₅ ) of the NOR gate 11 is at the H level. The logical configuration is such that the output (A ₆ ) of the NOR gate 12 becomes H level when 3 is at L level.

Now, assuming that one cycle of # 1 to # 3 coincides with 180 degrees of a rotating body such as a motor (however, a mechanical angle in which one rotation is 360 degrees), upper two bits A ₆ and A _5. one cycle is 180 degrees (where the phase is different), and one cycle of the least significant bits a ₄ becomes 180 ° ÷ 3 = 60 degrees. That is, since the resolution (accuracy) of the rotation angle signal is given by the least significant bit (A ₄ ) of the rotation angle signal, the resolution when the number of position sensors is three is “60 degrees”.

[0005]

However, in such a conventional rotation angle detecting device, the resolution obtained by the three position sensors is at most "60 degrees". The number of sensors must be significantly increased, but this not only increases the cost but also makes it difficult to apply to a relatively small rotating body because a large number of position sensors must be mounted on the rotating body. There is such a problem. [Purpose] Accordingly, an object of the present invention is to provide a rotation angle detection device that can obtain high resolution without increasing the number of position sensors.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for generating a plurality of rectangular waves which are arranged at regular intervals along the rotation direction of a rotating body and generate rectangular waves synchronized with the rotation of the rotating body. A position sensor, signal generation means for generating a plurality of bits of a rotation angle signal based on output signals from the plurality of position sensors, and a reset signal for generating a reset signal every half cycle of the least significant bit of the rotation angle signal Generating means; delay means for delaying the reset signal; first and second counting means for counting a clock signal of a predetermined frequency and resetting the count value at least at the output of the delay means; Holding means for receiving and holding a count value excluding lower n bits of the first counting means in response to an output of the generating means; and the second counting means Comparing means for comparing the count value with the content held by the holding means and outputting a predetermined pulse signal when the two coincide with each other; and a third count for counting the pulse signal and outputting a multi-bit interpolation signal Means, comprising:
The method is characterized in that a detected rotation angle signal having the plurality of bits of the interpolation signal as the lower side is output.

[0007]

According to the present invention, the values except for the lower n bits of the count value of the first counting means, a value count was 1/2 ⁿ of the first counting means in other words is stored in the storage means, the content held A predetermined pulse signal is output each time the count value of the second count means coincides with the count value of the second count means.

[0008] Here, the count period of the first counting means, the rotation angle signals of a plurality of bits which is generated based on the output signals of the plurality of position sensors (e.g., the conventional example A ₆ ~
A period corresponding to a half cycle of the least significant bits (A ₄₎ of the A _4), the predetermined pulse signal, from and outputted to the same period every 1/2 ⁿ equal parts the time, for example, , Assuming that the synchronous period is equivalent to X degrees in mechanical angle of the rotating body,
One cycle of the predetermined pulse signal is X degrees × (1/2 ⁿ ), and the resolution is improved by 1/2 ^{n with} respect to X degrees.
Note that the resolution is 1/2 ^{n + 1} for the least significant bit (A ₄ ) of the rotation angle signal.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of a rotation angle detecting device according to the present invention. First, the configuration will be described. In FIG. 1, reference numeral 10 denotes a rotating body (for example, a rotor of a brushless DC motor), 11 denotes a magnet attached to the rotating body 10, 1
Reference numerals 2a to 12c denote Hall elements as position sensors arranged at regular intervals on the stator side along the rotation direction of the rotating body 10. The Hall elements 12a to 12c output rectangular-wave signals # 1 to # 3 which change into two levels of H level and L level in synchronization with the rotation of the rotating body 10 by the magnetic flux from the magnet 11, and these signals # One cycle of each of 1 to # 3 is 180
Degrees (however, a mechanical angle in which one rotation of the rotating body 10 is 360 degrees; hereinafter, the angles are mechanical angles unless otherwise specified), and the position sensors 12a to 1
A phase difference is provided according to the mounting interval (60 degrees) of 2c.

Reference numeral 13 denotes a magnetic pole commutation logic (refer to FIG. 4 for a detailed configuration diagram) as signal generation means for generating 3-bit rotation angle signals A _{6 to} A ₄ based on the signals # 1 to # 3. a smoothing circuit comprising a point embodiment, the smoothing circuit 14 is based on the least significant bits of the rotation angle signal _{a 6 ~A 4 (a 4)} , generates an interpolation signal a ₃ to a ₀ of 4 bits Is what you do.

Reference numeral 15 denotes a first ROM (read only memor)
y) and 16 are second ROMs, and these ROMs 1
Reference numerals 5 and 16 denote 7-bit detected rotation angle signals (A _{6 to} A _{0) having the} 3-bit rotation angle signals A _{6 to} A ₄ as upper bits and the 4-bit interpolation signals A _{3 to} A ₀ as lower bits. ) Has a predetermined address space, and reads out digital data stored in the space in advance in accordance with a combination of 7-bit detected rotation angle signals.

Here, the digital data is data that is the basis of a voltage waveform for driving the rotating body 10 (assuming a brushless DC motor), and is finally the data Dα read from the first ROM 15. An A-phase drive voltage waveform φ _A is generated, and a C-phase drive voltage waveform φ _C is generated by data Dβ read from the second ROM 16.
It is adapted to generate a driving voltage waveform phi _B of B phase by adding the α and D.beta.

That is, reference numerals 17 and 18 denote multiplication type digital / analog converters (hereinafter referred to as “A / D converters”) which multiply Dα and Dβ by a coefficient M to generate a sinusoidal analog voltage waveform having an amplitude corresponding to the coefficient M. ), 19 is an adder for adding the outputs of the A / D converters 17 and 18, 20 is an oscillator for generating a reference pulse for PWM (pulse width modulation), 21 to 21
A comparator 23 changes the width of the reference pulse according to the magnitude of the analog voltage signal from the A / D converters 17 and 18 or the adder 19 (as drive voltage waveforms φ _A , φ _B and φ _C ) and outputs the same. the abbreviation "COMP"), 24 to 26 denote inverters for outputting the driving voltage waveform φ _a, φ _B, φ _C of inverting the voltage waveform (identified by bar with sign).

[0014] Incidentally, 27 is the frequency of the output signal from the position sensor 12 a to 12 c (# 3 in the figure), that is, an output frequency / voltage converter voltage V _V corresponding to the rotational speed of the rotating body 10 (hereinafter, "F / V converter ”), 28 is an adder that outputs a coefficient M obtained by adding the voltage V _V from the F / V converter 27 and an arbitrary command voltage V _C. Varying the command voltage V _C, the value of the coefficient M is changed D / A converter 17, 1
The amplitude of the sinusoidal analog voltage waveform output from 8 changes, and as a result, the rotational speed of the rotating body 10 is controlled in accordance with the command voltage.

FIG. 2 is a conceptual configuration diagram of the smoothing circuit 14. In this figure, 14a is a reset signal generating means for outputting a reset signal RST ₁ on the falling edge and the rising edge of the least significant bits A ₄ of the rotary angle signal (i.e. every half cycle of the A _4), 14b delay the RST ₁ (RST ₂ is a reset signal after delay) delay means, 14
c denotes a clock generating means for generating a clock signal CLK of a predetermined frequency, 14d resets the count contents at the timing of the RST ₂ with counting the CLK m
The first counting means 14e having a (m = 12 for convenience) bit configuration, and mn = 8 bits excluding the lower n (for convenience n = 4) bits of the count value of the first counting means 14d. below "CNT _1") holding means for holding uptake in response to RST _1, 14f is the count contents m-n bits (here reset at the timing of RST ₂ or later pulse signal PLS with counts the CLK is The second counting means 14g having an 8-bit structure has a count value (hereinafter referred to as "CN") of the second counting means 14f.
T ₂ )) and the contents held by the holding means 14 e (hereinafter “C _REF ”), and when they match (CNT
₂ = C _REF) to the comparison means for outputting a predetermined pulse signal PLS, 14h is the count contents with counts the pulse signal PLS for outputting an interpolation signal of 4 bits from A ₀ to A ₃ of the RST ₂ This is a third counting means for resetting at a timing.

In such a configuration, the signal A_FourHalf a lap of
Count value of the first counting means 14d in the period,
For example, "4000" in decimal notation_(Ten)"
The binary representation is "1111 1010 0000₍₂₎"
Is the lower n bits of this count value (here, 4 bits
Mn bits (8 bits) excluding (1) 1
010₍₂₎”, That is,“ 250 in decimal notation._(Ten)"When
So, after all, signal A_FourThe half cycle of is 1/2ⁿ(N = 4
Therefore, it is divided into 1/16).

[0017] Therefore, the resolution of the pulse signal PLS having a period corresponding to 1/2 ⁿ of the half period of the signal A _4, for example a half cycle of the signal A ₄ a mechanical angle of the rotor 10 when the 30 °, 30 degree × (1/2 ⁿ⁾ becomes, 1/2 ⁿ stuff resolution improvement effect can be obtained. As a result, despite having the same number (three) of position sensors as the conventional example at the beginning, compared with the resolution (A ₄ = 60 degrees) of the conventional example, the pulse signal PLS of the present embodiment has 30 Degree ÷ 16 = 1.875 degrees (n
= 4) High resolution can be obtained, and high detection accuracy can be realized without increasing the number of position sensors.

In this embodiment, as shown in FIG.
The period of 4-bit interpolated signal A ₃ to A ₀ output from the third counting means 14h, are respectively 1 / 2,1 / 4,1 / 8,1 / 16 against the period of the signal A ₄ .
This is because the finally generated detected rotation angle signal (A ₆ to
This is because the continuity of weighting (see the following table) of each bit of A ₀ ) is considered. Thus, the actual resolution of this embodiment becomes a resolution of the least significant bit A ₀ of the detected rotational angle signal, as can be seen from FIG. 3, the half cycle of the A ₀ is A ₄ 1
Since it is divided into six parts (*), if it is calculated in the same manner as above, it becomes 30 degrees / 16 = 1.875 degrees.

* Least significant bit A₀Is A_FourHit a half cycle
8 cycles, so it is as if A _Four1/8 resolution
Looks like, but actually A₀H period of one cycle and L
Since the level period is the resolution, A_FourHalf a lap of
The resolution is obtained by dividing the period (30 degrees) by 1/16.
You.

[0020]

According to the present invention, the rotation angle signal is interpolated by further dividing the half cycle of the least significant bit of the rotation angle signal generated based on the signal from the position sensor by 1 / ^2n. With this configuration, a low-cost, high-resolution rotation angle detection device can be realized without increasing the number of position sensors, and particularly useful technology applicable to relatively small rotating bodies can be provided.

[Brief description of the drawings]

FIG. 1 is an overall block diagram of one embodiment.

FIG. 2 is a conceptual configuration diagram of a smoothing circuit according to one embodiment.

FIG. 3 is a timing chart of a smoothing circuit according to one embodiment.

FIG. 4 is a configuration diagram of a magnetic pole commutation logic that is also used as a conventional example.

FIG. 5 is a timing chart of a magnetic pole commutation logic.

[Explanation of symbols]

 10: Rotating body 12a to 12c: Position sensor 13: Magnetic pole commutation logic (signal generating means) 14a: Reset signal generating means 14b: Delay means 14d: First counting means 14e: Holding means 14f: Second counting means 14g : Comparison means 14h: third counting means

Continuation of the front page (56) References JP-A-64-63811 (JP, A) JP-A-5-203463 (JP, A) JP-A-5-79856 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G01B ^7/ 00-7/34 102 G01D 5/00-5/252 G01D 5/39-5/62

Claims (1)

(57) [Claims] 1. A plurality of position sensors arranged at regular intervals along a rotation direction of a rotating body and generating rectangular waves synchronized with the rotation of the rotating body, based on output signals from the plurality of position sensors. Signal generation means for generating a plurality of bits of rotation angle signal; reset signal generation means for generating a reset signal every half cycle of the least significant bit of the rotation angle signal; delay means for delaying the reset signal; First and second counting means for counting the clock signal at least and resetting the count value at least with the output of the delay means; and in response to the output of the reset signal generating means, holding means for taking in and holding a count value excluding n bits; comparing the count value of the second count means with the content held by the holding means; A comparison unit that outputs a predetermined pulse signal when a match is found, and a third counting unit that counts the pulse signal and outputs a multi-bit interpolation signal. A rotation angle detection device for outputting a detection rotation angle signal having a higher-order side and the multi-bit interpolation signal as a lower-order side.