JP2006153802A - Noncontact-type angle detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle detector for detecting an angle range that exceeds 180°, using a simple structure. <P>SOLUTION: An MR sensor 1 outputs a wave signal of at least two cycles per revolution; in response to a rotating body 8 with a magnet 9. A microcomputer 2 calculates the rotation angle, by inputting the wave signal and discriminating in which the angle region the wave signal is of which period by software. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a detector that detects a rotation angle of a rotating body in a non-contact manner.

  The non-contact type rotation angle detector has advantages such as no wear compared to a contact type such as a potentiometer. For this reason, it has been put to practical use in fields that require a long life and high reliability.

  In the non-contact type angle detector, a magnet is provided on a rotating body to be detected, and a detection element having a magnetic sensitivity characteristic is disposed at a position facing the magnet. A magnetoresistive element (hereinafter sometimes referred to as “MR element”) is used as the detection element.

  In the MR element, the resistance value of the element changes according to the magnitude of the magnetic field. Further, the resistance value changes depending on the rotation angle of the magnetic field, and the same waveform is repeated at a rotation angle of 180 °. However, since the polarity inversion cannot be determined, the rotation angle detection range is limited to 0 ° to 180 ° only with the MR element.

  Therefore, in the prior art, the angle detection range is extended to 0 ° to 360 ° by using an element that can determine the magnetic field direction such as a Hall element in addition to the MR element as in Patent Documents 1 and 2. . That is, in the Hall element, when the polarity of the magnet is inverted (N pole and S pole are inverted by 180 °), the signal level is inverted from the high level to the low level or vice versa. By combining the signal, a rotation angle of 0 ° to 360 ° can be detected.

US Pat. No. 6,064,197 US Pat. No. 6,707,293

  In the conventional magnetic sensitive rotation angle detector, it is necessary to provide a Hall element in addition to the MR element as described above, and the structure of the angle detector is complicated. Further, in order to continuously detect 0 ° to 360 °, such as the presence of hysteresis in the magnetic reactivity of the Hall element, it is necessary to provide a plurality of Hall elements. In addition, detection in a range exceeding 360 ° was impossible.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems and aims to provide a rotation angle detector that eliminates the need for a Hall element and can detect a rotation angle of 360 ° or more as required.

  A rotation angle detector according to the present invention receives a detection element that outputs a waveform signal of at least two cycles per rotation in response to a rotating body to be detected, and the waveform signal, and the waveform signal is in any cycle. And calculating means for calculating the rotation angle by determining which angle region is in the software.

  For example, a rotating body with a magnet driven by a motor, a magnetoresistive element that is magnetically sensitive to the rotating body and outputs a waveform signal that changes according to the rotation angle of the rotating body, and a magnetic field direction of the rotating body, Computing means for discriminating the waveform signal by software processing and detecting a rotation angle of the rotating body.

  According to the present invention, an angle range exceeding 180 ° can be detected by an angle detector having a simple structure. The object of detecting the rotation angle of the rotating body in a range exceeding 180 ° can be realized with a minimum number of parts and without impairing reliability.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a non-contact angle detector according to a first embodiment of the present invention.

  The output shaft 8 is connected to the rotating shaft of the motor 6 via the worm gear 7. The motor 6 can be controlled to rotate in both forward and reverse directions. As a result, the output shaft 8 can also rotate forward (CW) and reverse (CCW) as indicated by an arrow 8A via the worm gear.

  The magnet 9 fixed to the output shaft 8 includes a pair of N poles and S poles. The magnet 9 constitutes a rotor of an angle detector and performs a rotational motion in synchronization with the output shaft 8. The shape is a disk shape, half of which is N pole and the other half is S pole.

At a position away from the magnet 9 to about 5mm, the printed circuit board (P rinted C ircuit B oard; hereinafter referred to as "PCB") 5 is disposed. The magnetoresistive element (hereinafter referred to as MR sensor) 1 is disposed on the PCB 5 and is on the axis of the rotation axis of the magnet 9.

  In this embodiment, the MR sensor 1 is used as the rotation angle detection element, but the MR sensor includes a GMR (giant magnetoresistive element) sensor and an AMR (anisotropic magnetoresistive) sensor. In addition, the use of an element that reacts to magnetic force, such as a hole, is not limited as long as the same effect as the MR sensor can be obtained.

  On the PCB 5 are a microcomputer 2 electrically connected to the MR sensor 1, an EEPROM (Electrically Erasable Programmable ROM) 3 electrically connected to the microcomputer 2, and a motor driver electrically connected to the microcomputer 2. 4 are implemented.

  The motor driver 4 is electrically connected to the motor 6. A worm gear 7 is attached to the rotating shaft of the motor 6. The worm gear 7 meshes with a gear mechanism formed on the output shaft 8.

  FIG. 2 is a functional block diagram of the angle detector of the present embodiment.

  As the motor 6 rotates, the magnet 9 rotates in synchronization with the output shaft 8. As the magnet 9 rotates, the magnetic circuit at the position of the MR sensor 1 changes. The MR sensor 1 is sensitive to the magnetism in the horizontal direction (X direction in FIG. 1) and has almost insensitive characteristics to the magnetism in the Y direction perpendicular to the X direction. Also, its own resistance value changes according to the strength of the magnetic field.

  As the magnet 9 rotates, the magnetic field direction changes and the magnetic intensity of the X direction component changes, so that a wavy waveform signal is output. If the plurality of MR sensors 1 are arranged at different angles, waveforms having different phase differences are output. In this example, as will be described later, the MR sensor 1 outputs two systems of waveform signals having a phase difference of 45 degrees with one cycle being 180 °.

  The output (change in resistance value) of the MR sensor 1 is converted into a voltage change by the interface circuit 10. The converted voltage value is input to the microcomputer 2 as an analog value, converted into a digital value, and then subjected to signal processing by the microcomputer 2. Here, the signal processing is to calculate the rotation angle of the output shaft 8 based on the signal input from the interface circuit 10. In the calculation process, the judgment data of the rotation area necessary for angle calculation is stored in the EEPROM 3.

  The microcomputer 2 communicates with an external control device via the interface circuit 11. When receiving a command for rotating the output shaft 8 from the external control device, the microcomputer 2 gives a predetermined command signal to the motor driver 4. .

  The motor driver 4 supplies a current for driving the motor 6 to the motor 6 based on an input signal from the microcomputer 2.

  The rotational force of the motor 6 is transmitted to the worm gear 7 and the output shaft 8 rotates. Since the worm gear 7 is used for the power transmission mechanism of the motor 6, the rotational movement of the output shaft 8 while the motor 6 is stopped causes backlash between the worm gear 7 and the gear formed on the output shaft 8. It is the range of movement allowed as a stop condition.

  FIG. 3 shows the MR sensor waveform and the rotation angle region determination signal when the output shaft 8 rotates in the range of 360 degrees. As the MR sensor 1, for example, KMZ43 manufactured by Philips is used.

  3 shows the rotation angle of the output shaft 8 on the X axis and the output waveform of the MR sensor 1 on the Y axis. The outputs of the MR sensor 1 are two-system outputs with a phase difference of 45 degrees, and these outputs are designated as MR1 and MR2, respectively. The signal period of MR 1 and MR 2 is 180 ° with respect to the rotation angle of the output shaft 8. That is, the same waveform is repeated in the 0 ° to 180 ° region and the 180 ° to 360 ° region. For this reason, it is impossible to distinguish the region of 0 ° to 180 ° and the region of the rotation angle of 180 ° to 360 ° only by the waveform signals of MR1 and MR2. Therefore, if only MR1 and MR2 are used, the angle detection range is limited to 0 ° to 180 °. In this embodiment, in order to detect a range exceeding 180 °, the software of the microcomputer 2 generates an area determination signal 1 (hereinafter referred to as “H1”) and an area determination signal 2 (hereinafter referred to as “H2”). To do.

  As shown in the middle section 3-2 of FIG. 3, H1 is an area determination signal generated in synchronization with the upper limit peak of MR1. H2 is an area determination signal created in synchronization with the lower limit peak of MR1.

  If the rotation angle of the output shaft 8 is taken as the X-axis and the state of H1 and H2 is taken as the Y-axis, the microcomputer 2 has a rotation angle range of 0 ° to 180 ° with respect to H1. It has a low level (“0”) at a hysteresis α) and a high level (“1”) within a range of 180 ° to 360 ° (with a positive or negative hysteresis α by forward / reverse rotation).

  Such H1 indicates that the magnetic field direction of the magnet 9 is reversed.

  Further, H2 is set to a low level within a rotation angle range of 90 ° to 270 ° (with a positive or negative hysteresis α by forward / reverse rotation), and a range of 270 ° to 360 ° (0 °) to 90 ° (however, (With hysteresis α of + and-by forward / reverse rotation).

3A, 3 </ b> B, 3 </ b> C, and 3 </ b> D are angular regions in the forward rotation direction (CW), and 360 degrees are divided into four equal parts. Further, (E), (F), (G), and (H) are angular regions in the reverse rotation direction (CCW), and 360 degrees are equally divided into four as described above. Here, α is a hysteresis of the region determination signal generated in a pseudo manner. In this embodiment, the angular regions (A) to (H) at the time of forward rotation and reverse rotation are represented by the determination signals H1 and H2 as follows.
(About H1)
During the forward rotation of the output shaft 8, H1 is in the low level state ("0") in the angular range (A position and B position) from (0 ° + α °) to (180 ° + α °). In the angular range (C position and D position) from (180 ° + α °) to (360 ° + α or 0 ° + α °), H1 becomes a high level state (“1”).

When the output shaft 8 rotates in the reverse direction, H1 is in a high level state (180 ° -α) in an angular range (E position and F position) of (360 ° -α °) to (180 ° -α °). In the angle range (G position and H position) of (°) to (360 ° -α ° or 0 ° -α °), H1 becomes a low level state.
(About H2)
During the forward rotation of the output shaft 8, H2 is in a low level state in an angular range (B position and C position) of (90 ° + α °) to (270 ° + α °). In the angular range (A position and D position) of (0 ° to 90 ° + α °) or (270 ° + α ° to 360 ° + α), H2 is in a high level state. Further, during the reverse rotation of the output shaft 8, H2 is in a low level state in an angle range (F position and G position) of (270 ° −α °) to (90 ° −α °). In the angle range (H position and E position) of (90 ° -α ° to 0 °) or (360 ° to 270 ° -α °), H2 is in a high level state.

  The microcomputer 2 writes predetermined information in the EEPROM 3 at the timing when the states of H1 and H2 change. The predetermined information includes the number of the region determination signal that has changed (the number corresponding to H1 is 1 and the number corresponding to H2 is 2) and the updated value (signal level) of the region determination signal. FIG. 7 shows the update condition of the area determination signal written in the EEPROM 3.

  For example, when the rotation direction of the output shaft 8 is CW and the angle region is at the A position, the microcomputer 2 reads the value of H1, and when H1 = 0, the address 0x00 (number of the region determination signal) of the EEPROM 3 “1” is written to “0”, and “0” is written to address 0x01 (signal level of the region determination signal). When the rotation direction of the output shaft 8 is CCW and the angle region is at the H position, the microcomputer 2 reads the value of H2, and when H2 = 1, writes 2 to the address 0x00 of the EEPROM 3 and 1 to the address 0x01. Write. Here, the direction in which the angle increases is forward rotation (CW), and the direction in which the angle decreases is reverse rotation (CCW).

  FIG. 4 shows a flow for calculating the rotation angle of the rotary shaft 8 from the output of the MR sensor 1.

  The microcomputer 2 determines the region number based on the outputs (MR1 and MR2) of the MR sensor 1 and the region determination signals H1 and H2 (EEPROM data).

  Here, the region number is a number indicating each angle region (in other words, the direction of the rotating magnetic field) obtained by dividing 360 ° into eight equal parts (45 ° × 8), and includes (1) to (8). The region numbers (1) to (8) can be determined by comparing the signals of MR1 and MR2 with threshold values TH1 and TH2 and referring to region determination signals H1 and H2 shown in FIG.

  FIG. 8 shows the area number determination conditions. For example, in the signal state of FIG. 3, if MR2> TH1 and the current EEPROM data is H1 = 0, the region number is (1). When MR2> TH1 and H1 = 1, the region number is (5). When MR1 <TH2 and H1 = 0, the region number is (2). When MR1 <TH2 and H1 = 1, the region number is (6). The thresholds TH1 and TH2 are constants set with reference to the point where MR1 and MR2 intersect.

  Next, the rotation angle θ of the rotating shaft 8 is calculated by Equation 1.

Here, the parameters {x, y, b} in Equation 1 are as shown in FIG. For example, when the region number is (1), {x, y, b} = {MR1, −MR2, 45} is set, and Expression 2 is obtained.

  As shown in FIG. 9, in the present invention, the constant b increases by 45 degrees corresponding to the region number and is set to 45 °, 90 °, 135 °,..., 360 °. Angle detection is possible in a range.

  In the present invention, the region determination signals H1 and H2 are realized by software of the microcomputer 2. For this reason, there are concerns that the microcomputer 2 may be out of control or the angle detector may be powered off while the output shaft 8 is rotating.

  If these conditions overlap with the writing timing of the EEPROM 3 or occur immediately before the writing timing of the EEPROM 3, the predetermined information may not be written to the EEPROM 3.

  For example, in FIG. 3, when the power of the angle detector is cut off at the microcomputer stop position a: 12 and the operation of the microcomputer 2 is thereby stopped, the value of H1 is not updated from low to high, Writing to EEPROM3 is not executed. In this case, the current supply to the motor 6 is stopped, but since there is an inertia moment in the motor 6, the worm gear 7 and the output shaft 8, the output shaft 8 continues the rotational movement for a certain period of time, and then the rotational speed due to the frictional force. Drop and stop.

  The amount of rotation from the microcomputer stop position a: 12 to the output shaft stop position 13 (hereinafter referred to as overshoot amount) is determined by the friction and moment of inertia of the sliding part. Here, the overshoot amount is 45 ° and the output shaft 8 is set as the output shaft stop position: 13 in FIG.

  In this embodiment, even if the operation of the angle detector is stopped without writing predetermined information in the EEPROM 3, when the angle detector is turned on again, it returns to normal operation as follows. Can do.

  FIG. 5 shows an initialization process of the microcomputer 2 when the power is turned on.

  Immediately after the power is turned on, the microcomputer 2 assigns 0xFF (initialization) to predetermined RAM variables H1 and H2 (step 1).

  Next, data is read from the address 0x00 of the EEPROM 3, and if the corresponding data is 1, the data is read from the address 0x01 of the EEPROM 3 and assigned to the RAM variable H1 (step 2).

  Alternatively, data is read from the address 0x00 of the EEPROM 3 and if the corresponding data is 2, the data is read from the address 0x01 of the EEPROM 3 and assigned to the RAM variable H2 (step 3).

  Next, using the outputs MR1 and MR2 of the MR sensor 1 and the region determination signals H1 and H2, the angle region number is determined based on FIG. 8 (step 4). The angle region numbers are defined from (1) to (8), and each has an angle range of about 45 ° as described above.

  Here, consider a case where the angle detector is normally terminated after writing to the EEPROM 3 is executed at the microcomputer stop position a: 12 in FIG.

  After power-on again, 0xFF is assigned to H1 and H2. Since the angle detector has finished normally, writing to the EEPROM 3 is normally executed at the microcomputer stop position a: 12, and 1 is assigned to the address 0x00 and 1 is assigned to the address 0x01 of the EEPROM 3, respectively. Has been written. According to the above-described step 2, 1 is assigned to H1, but H2 indicates 0xFF. At this time, since the output shaft 8 is stopped at the output shaft stop position: 15 in FIG. 3, the condition of MR2 ≧ TH1 is satisfied. For this reason, the area number is determined as (5) from the conditional expression of FIG.

  Here, a case is considered in which writing to the EEPROM 3 is not executed at the microcomputer stop position a: 12 in FIG. 3 and the angle detector ends abnormally.

  After power-on again, 0xFF is assigned to H1 and H2. Since the angle detector has ended abnormally, writing to the EEPROM 3 is not executed at the microcomputer stop position a: 12, and the output shaft 8 is in the angle region (1) → (2) → (3) → Assuming that the rotation is (4), 2 is written in the address 0x00 of the EEPROM 3 and 0 is written in the address 0x01. If the output shaft 8 is rotated in the angular region (5) → (4) → (3) → (4), 2 is written in the address 0x00 of the EEPROM 3 and 0 is written in the address 0x01. . According to the above-mentioned step 3, 0 is substituted for H2, but H1 indicates 0xFF. At this time, since the output shaft 8 is stopped at the output shaft stop position: 15 in FIG. 3, the condition of MR2 ≧ TH1 is satisfied. For this reason, the area number is determined as (5) from the conditional expression of FIG.

  As described above, even when the angle detector is turned off while the output rotating shaft 8 is rotating, if the angle detector is turned on again, the region number can be normally determined as (5). Normal processing is performed.

  In the above-described embodiment, an example in which the angle can be detected in the range of the output shaft 8 from 0 to 360 ° is shown, but in the next embodiment, the angle can be detected even when the angle is 360 ° or more.

  Consider the case where the output shaft 8 rotates beyond 360 °.

  Here, the case where an angle is detected in the rotation range of 1080 degrees (three rotations) is demonstrated as the example.

  FIG. 6 shows signal waveforms of the outputs MR1 and MR2 and the region determination signals H1 and H2 of the MR sensor 1 when the output shaft rotates by 1080 °.

  The output of the MR sensor 1 is an output waveform with a cycle of 180 ° as described above, and the same waveform is repeated every 180 °. The area determination signal is generated by software of the microcomputer 2 according to FIG.

  In the above-described angle range of 0 ° to 360 °, it is composed of eight regions A to H. However, in the angle range of 0 ° to 1080 °, A to H, A ′ to H ′, and A It is composed of 24 areas '' to H ''.

  In addition, the area determination signal in the above-described 0 ° to 360 ° detection is a binary state of “0” and “1”, but the area determination signal in the 0 ° to 1080 ° detection is 0, 1, 2, 3, It has six states of 4,5. The angle calculation process of the output shaft 8 is the same as that in FIG. 4, but the region number determination condition in FIG. 8 and the region determination signal update condition in FIG. 7 are replaced with FIG. 11 and FIG. Further, in the case of calculating the angle according to Equation 2, the angle calculation parameters shown in FIG. 12 are used.

  Here, let us consider a case where writing to the EEPROM 3 is not executed at the microcomputer stop position b: 14 in FIG. 6 and the angle detector ends abnormally. After power-on again, 0xFF is assigned to H1 and H2. Since the angle detector has ended abnormally, writing to the EEPROM 3 is not executed at the microcomputer stop position b: 14, and the output shaft 8 is in the angle region (14) → (15) → (16) → Assuming that the rotation is (17), 2 is written in the address 0x00 of the EEPROM 3, and 3 is written in the address 0x01. If the output shaft 8 is rotated in the angular region (17) → (16) → (15) → (16), 2 is written in the address 0x00 of the EEPROM 3 and 3 is written in the address 0x01. . According to the above-mentioned step 3, 3 is substituted for H2, but H1 indicates 0xFF. At this time, since the output shaft 8 is stopped at the output shaft stop position: 15 in FIG. 3, the condition of MR2 ≧ TH1 is satisfied. For this reason, the area number is determined to be (17) from the conditional expression of FIG.

  From the above, in the case of 0 ° to 1080 ° detection, even if an abnormality occurs such as the power of the angle detector being cut off while the output rotating shaft 8 is rotating, if the power of the angle detector is turned on again, The angle region can be normally determined and normal processing is executed.

The block diagram of the rotation angle detector which concerns on 1st Example of this invention. The functional block diagram of FIG. The time chart which shows MR sensor waveform and a region determination signal. The flowchart which shows the angle calculation process in the said Example. The flowchart of the initialization process in the said Example. The time chart which shows the MR sensor waveform and area | region determination signal of 2nd Example. Update conditions for the region determination signal used in the first embodiment. Area number determination conditions used in the first embodiment. Angle parameters used in the first embodiment. Update conditions for the region determination signal used in the second embodiment. Area number determination conditions used in the second embodiment. Angle parameters used in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... MR sensor, 2 ... Microcomputer, 3 ... EEPROM, 4 ... Motor driver, 5 ... PCB, 6 ... Motor, 8 ... Output shaft, 9 ... Magnet, 10 ... I / F_a, 11 ... I / F_b.

Claims (9)

A detection element that outputs a waveform signal of at least two cycles per rotation in response to a rotating body to be detected;
An arithmetic means for inputting the waveform signal, determining which angle region the waveform signal is in which period and in which angle region by software, and calculating a rotation angle;
A rotation angle detector. In Claim 1, the said rotation angle detector is for detecting the rotation angle within 1 rotation of the said rotary body, or the rotation angle more than 1 rotation,
The arithmetic means inputs a waveform signal from the detection element, divides the waveform signal into a plurality of regions in a predetermined angle unit, and forms a signal for discriminating each region based on the waveform signal. A rotation angle detector that calculates a rotation angle by using the parameters. The detection element according to claim 1 or 2, wherein the detection element outputs two waveform signals having a cycle of 180 ° and a phase difference of 45 ° according to the rotation of the rotating body,
The calculation means divides these two types of waveform signals into eight parts in a 360 ° range using a threshold signal, and calculates a rotation angle using a parameter for each of the eight divided areas. Angle detector.   4. The rotating body according to claim 1, wherein the rotating body includes a magnet composed of a pair of N poles and S poles, and the detection element is magnetically sensitive to the rotation of the rotating body. The magnetoresistive element outputs two waveform signals having a cycle of 180 ° and a phase difference of 45 °, and the computing means converts the two waveform signals output from the magnetoresistive element into two threshold signals. A rotation angle detector comprising: a microcomputer that calculates a rotation angle using a parameter for each of the 8 divided areas by dividing the area into 8 by 360 degrees.   5. The calculation unit according to claim 1, wherein the calculation unit divides a rotation angle range in which the rotating body is operable into a plurality of areas, and information on the divided areas is associated with the rotation of the rotating body. A rotation angle detector, characterized by having a storage device that stores the data in a rewritable manner. A rotating body with a magnet driven by a motor;
A magnetoresistive element that is magnetically sensitive to the rotating body and outputs a waveform signal that changes in accordance with the rotation angle of the rotating body;
Arithmetic means for detecting the rotation angle of the rotating body by determining the magnetic field direction of the rotating body by software processing the waveform signal;
A rotation angle detector.   7. The calculation means according to claim 6, wherein when the rotating body makes one or more rotations, the calculation means determines the number of rotations by software processing of the waveform signal, and this determination and the determination of the magnetic field direction. A rotation angle detector that detects a rotation angle of 360 ° or more. In a rotation angle detector comprising a rotating body with a magnet rotated by a motor, and a magnetoresistive element that outputs a waveform signal that changes according to the rotation of the rotating body,
The magnetoresistive element and a microcomputer for inputting a waveform signal from the magnetoresistive element are provided on a printed circuit board, and the microcomputer performs software processing on the output signal of the magnetoresistive element to A rotation angle detector for detecting a rotation angle of the rotating body by discriminating a magnetic field direction. 9. The writable storage device for storing the angle region of the rotating body calculated by the microcomputer and a motor driver circuit in addition to the magnetoresistive element and the microcomputer in the printed wiring board. A rotation angle detector characterized by being mounted.

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