JP4480453B2 - Rotation angle sensor - Google Patents

Description

  The present invention relates to a rotation angle sensor that detects a rotation angle of a rotation shaft.

  There are optical and magnetic types of rotation angle sensors that detect the rotation angle of the rotary shaft. In the absolute encoder that detects the absolute angle of the optical type, the origin of the encoder and the origin of the servo motor are precisely matched. Therefore, an origin setting method as disclosed in Patent Document 1 has been proposed. In this setting method, an absolute rotary encoder is mounted and connected to a servo motor, etc., then the detection signal from the encoder is processed and the angle detection signal is output to the power supply terminal of the servo motor at the origin position of the servo motor. The origin reset signal from the origin reset circuit is supplied in a state of being superimposed on the power source. As a result, the origin reset signal detection circuit in the signal processing circuit detects this origin reset signal, and binary data for the rotation angle of the encoder at that time is held in the memory. Thereafter, by subtracting the value held in this memory from the outputs of the gray / binary conversion circuit and the multi-rotation counter, the rotation angle from the set origin position can be output as a detection value.

  On the other hand, when an optical encoder is used to produce a high-precision absolute encoder, there is a problem in that the shape of the optical slit becomes large and cannot be reduced in size, and a magnetic rotation angle sensor as disclosed in Patent Document 2 is present. Has been devised.

Japanese Unexamined Patent Publication No. Hei 6-29875 JP-A-4-48215

  A magnetic rotation angle sensor as described in Patent Document 2 is a plurality of rotating bodies composed of magnets and detecting the strength of the magnetic field of the rotating body and outputting a value corresponding to the rotation angle. And a signal processing circuit that calculates and outputs the angle of the rotating body from the signals output from the plurality of magnetic sensors. The rotating body and the magnetic sensor are small and highly accurate. Can be provided.

  However, in the magnetic rotation angle sensor, the value of the signal output from the magnetic sensor corresponds to the angle detection value of the rotating body, and the change corresponds to the angle change of the rotating body. A signal output from the magnetic sensor is a minute signal, and an operation amplification stage for amplifying the minute signal is provided in the signal processing circuit. Therefore, when the origin reset signal is superimposed on the power supply terminal of the signal processing circuit as described in Patent Document 1 described above, fluctuations in the output of circuits such as the operation amplification stage occur due to fluctuations in the power supply voltage caused by the input of the origin reset signal. As a result, the measurement angle value fluctuates, and there is a problem that the origin cannot be reset accurately.

  If an input terminal dedicated to resetting the origin is installed, the number of terminals of the signal processing circuit (usually an IC) increases, which not only increases costs, but also due to external noise and carelessness during normal use. However, there is a problem in that the origin reset is activated, leading to a malfunction of the entire system using the rotation angle sensor.

  Therefore, an object of the present invention is to provide a rotation angle sensor that solves the above problems.

  Furthermore, the other object of this invention is to provide the rotation angle sensor which can set arbitrary angle ranges.

  The present invention provides a rotating body having a magnet, and a plurality of signals that output a signal having a value corresponding to the rotation angle of the rotating body by detecting the strength of the magnetic field of the magnet that changes according to the rotation of the rotating body. A reference point is set by a magnetic sensor, an angle calculation circuit for calculating a rotation angle of the rotating body from signals output from the plurality of magnetic sensors, and a signal input to at least one terminal connected to an external device. An input signal determination circuit for determining whether or not the signal is a predetermined signal for starting, and a signal input to the at least one terminal by the input signal determination circuit is a predetermined signal for starting reference point setting Storage means for storing, as reference point data, the rotation angle of the rotating body from the angle calculation circuit obtained in response to the determination, and rotation of the rotating body calculated by the angle calculation circuit. Characterized in that it comprises an output means for outputting a value obtained by adding a predetermined value to the value or the value obtained by subtracting by subtracting the reference point data in the storage means from the time the rotation angle measurement.

  Here, the at least one terminal may be connected to a serial interface.

  The at least one terminal is a signal output terminal, and the input terminal is capable of inputting a predetermined signal for starting the reference point setting from outside by temporarily disconnecting the signal output terminal from the signal output means. An input / output switching circuit to function can be further provided.

  Further, the at least one terminal may be an error output terminal.

  Furthermore, the present invention provides a rotating body having a magnet, and a plurality of signals that detect the strength of the magnetic field of the magnet that changes in accordance with the rotation of the rotating body and output a value corresponding to the rotation angle of the rotating body. A plurality of magnetic sensors, an angle calculation circuit for calculating a rotation angle of the rotating body from signals output from the plurality of magnetic sensors, and a predetermined reference from the rotation angle of the rotating body calculated by the angle calculation circuit An output unit that outputs a value obtained by subtracting the point data as a rotation angle measurement value, and a value within a predetermined angle range among the rotation angle measurement values from the output unit is output as it is, and a value outside the angle range is output in advance. An angle conversion means for converting to a predetermined value and outputting it is provided.

  Here, the predetermined value may be one of an upper limit value and a lower limit value of the predetermined angle range.

  Further, the predetermined value is the upper limit value until the rotation angle measurement value from the output means exceeds the upper limit value of the predetermined angle range and reaches a predetermined angle, and the predetermined value exceeds the predetermined angle. Until the lower limit value of the determined angle range is reached, the lower limit value can be used.

  Furthermore, the present invention provides a rotating body having a magnet, and a plurality of signals that detect the strength of the magnetic field of the magnet that changes in accordance with the rotation of the rotating body and output a value corresponding to the rotation angle of the rotating body. An angle calculation circuit for calculating a rotation angle of the rotating body from signals output from the plurality of magnetic sensors, and a signal input to at least one terminal connected to an external device is a reference point An input signal determination circuit for determining whether or not the signal is a predetermined signal for starting setting, and a signal input to the at least one terminal by the input signal determination circuit is a predetermined signal for starting reference point setting When it is determined that there is a storage means for storing the rotation angle of the rotating body from the angle calculation circuit obtained in response to the determination as reference point data, and the rotation calculated by the angle calculation circuit A value obtained by subtracting the reference point data in the storage means from the rotation angle or a value obtained by adding a constant value to the subtracted value as a rotation angle measurement value, and a rotation angle measurement value from the output means. Among them, there is provided angle conversion means for outputting a value within a predetermined angle range as it is and converting a value outside the angle range into a predetermined value and outputting it.

  According to the present invention, by setting the terminal that receives a signal for setting the reference point as at least one terminal connected to an external device different from the power supply line, the power supply voltage may fluctuate when the reference point is set. Therefore, an accurate reference point can be set.

  In addition, by causing the signal output terminal to function as an input terminal for receiving a signal for temporarily starting the reference point setting, there is no possibility that the reference point setting procedure will be started again. Inadvertent operation prevents malfunctions.

  Further, the number of terminals of the signal processing IC can be saved by sharing the input terminal for setting the reference point with the output terminal.

  Furthermore, since an arbitrary angle range can be set, versatility as a rotation angle sensor is further improved.

Example 1
FIG. 1 shows an example of a basic structure of a rotation detection mechanism portion of a rotation angle sensor according to the present invention, where (a) is a bottom view and (b) is a side view, showing a disk-shaped magnetism generating portion. The positional relationship between one and two magnetic sensors 2 and 3 is also shown. The magnetism generator 1 is magnetized in the radial direction, is supported by a rotating shaft 4, and rotates about the rotating shaft 4. The magnetic sensors 2 and 3 are composed of, for example, Hall elements, and are both disposed immediately below the periphery of the magnetism generator 1 and, as shown in (a), the center O of the circle of the magnetism generator 1 and the magnetism. An angle formed by a straight line passing through the sensor 2 and a straight line passing through the center O and the magnetic sensor 3 is approximately 90 degrees.

  FIG. 2 is a block diagram of the signal processing circuit 5 (IC) of the rotation angle sensor of this embodiment, and shows an example in which the input terminal for setting the reference point is shared with the input terminal of the serial interface. Output signals from the magnetic sensors 2 and 3 are amplified by the amplifiers 6 and 7, converted to digital data by analog / digital (A / D) converters 8 and 9, and input to the angle calculation circuit 10. The angle calculation circuit 10 is based on the input data from the A / D converters 8 and 9, and the internal origin (that is, two magnetic generators 1 and 2) that is a reference point unique to the rotation detection mechanism of the rotation angle sensor. Rotation angle data (hereinafter referred to as internal angle data) indicating how much the magnetism generating unit 1 has rotated is calculated from a unique reference point determined by the magnetic sensors 2 and 3. As will be described in detail later, when an ON signal is input from the reference point setting circuit 11, the angle calculation circuit 10 stores the internal angle data at that time in the rewritable nonvolatile memory 12 as a reference point. . When the detected angle value as the signal processing circuit is output from the output terminal DOUT, the angle calculation circuit 10 compares the internal angle data at that time with the value of the reference point in the nonvolatile memory 12, and the internal angle data is the reference value. If the value is larger than the point value, the value obtained by subtracting the reference point value from the internal angle data is used as the detected angle data after conversion. If the internal angle data is smaller than the reference point value, the reference point value is subtracted from the internal angle data. A value obtained by adding 360 degree angle data to the obtained value is supplied as angle data after conversion to an angle output circuit (D / A converter) 14 via an angle conversion circuit 13 (details will be described later). To convert it to an analog output and supply it to the output terminal DOUT.

  A chip select terminal CS, a serial clock terminal SCLK, a data input terminal MOSI, and a data output terminal MISO are serial interface terminals for connection with an external device. The angle calculation circuit 10 and the angle conversion are connected via the serial interface circuit 15. Connected to the circuit 13. An input signal determination circuit 16 is connected to the chip select terminal CS, the serial clock terminal SCLK, and the data input terminal MOSI. The signal processing circuit 5 has a CPU, a RAM as a work area of the CPU, and a function as a signal processing circuit such as angle calculation (including control procedures as shown in FIGS. 5 and 8 below). The angle calculation circuit 10, the reference point setting circuit 11, the angle conversion circuit 13, and the input signal determination circuit 16 can be realized as a part of the function of the CPU.

  When setting the reference point, the reference point is set in the following manner by a signal from the external device 17 (for example, a device or a computer using an angle detection value from the signal processing circuit 5) connected to the serial interface terminal. .

  FIG. 3 shows an example of a signal waveform at each terminal to which data is input from the external device 17 through the serial interface. In the normal operation of the serial interface, when the chip select terminal CS becomes active (GND level in FIG. 3), a clock signal is input to the serial clock terminal SCLK, and a predetermined data string is input to the data input terminal MOSI. Is input and serial data communication is performed with an external device. When the serial interface is used as an input terminal for setting a reference point, as shown in FIG. 4, when the chip select terminal CS is made active (GND level in FIG. 4) by control from an external device, the serial clock is set. A clock signal is not input to the terminal SCLK, and the terminal SCLK is maintained at a constant voltage level (in the case of FIG. 4, VDD level, that is, power supply voltage level) for a predetermined time or more. In response to this, the signal processing circuit 5 sets the reference point as follows. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 5, the input signal determination circuit 16 determines whether the signal input to the serial interface terminal is a signal for communication or a signal for setting a reference point. First, in S1, it is determined whether the chip select signal is activated. After the chip select signal is activated, the process proceeds to S2, and it is determined whether the serial clock signal is held high (VDD level) for a predetermined time. That is, if the serial clock signal is high (VDD level) in S2, the counter is started (S3), and the process proceeds to S4. In S4, it is determined whether the serial clock signal is at a low level, and in S5, it is determined whether the count of the counter has elapsed for a predetermined time (counting end). Therefore, when the voltage level of the serial clock terminal changes within the predetermined time set in the counter (that is, when the serial clock signal is determined to be low level in S4), the process returns to S1 and the state of the input signal determination circuit is initialized. Is done. If there is no voltage change at the serial clock terminal within the set time of the counter, the input signal determination circuit 16 determines that the signal input to the serial interface terminal is a signal for setting the reference point, and the reference point setting circuit An ON signal is output to the angle calculation circuit 10 via 11. In response to this, the angle calculation circuit 10 acquires the output signals from the magnetic sensors 2 and 3 at that time through the A / D converters 8 and 9 as described above (S6), and obtains the internal angle data. Calculation is performed (S7), and the internal angle data is stored in the nonvolatile memory 12 as reference point data (S8).

Next, the angle conversion circuit 13 will be described.
The angle conversion circuit 13 sets an upper limit value and a lower limit value of the measured angle based on the upper limit value and lower limit value data of the measured angle supplied from the outside through the serial interface circuit 15 and outputs them from the angle calculation circuit 10. If the value of the set angle data is not less than the lower limit value of the set angle to be measured and not more than the upper limit value, the angle output circuit outputs the angle data output from the angle calculation circuit 10 as it is as angle output data. 14 for output.

  Next, the operation of the angle conversion circuit 13 when the measured angle range (the angle range between the upper limit value and the lower limit value) is set to a value smaller than 360 degrees will be described. As a method of converting the angle output data in the angle conversion circuit 13 when the angle data output from the angle calculation circuit 10 is outside the angle range between the upper limit value and the lower limit value of the angle to be measured, FIG. As shown in (b), two types can be selected. 6 indicates the angle output of the angle conversion circuit 13, and the horizontal axis indicates the mechanical angle, that is, the internal angle calculated by the angle calculation circuit 10 (in the example of FIG. 6, the internal angle of 90 degrees is the reference point data). ).

  Type 1 shown in FIG. 6A is the upper limit until the angle data output from the angle calculation circuit 10 exceeds the upper limit value (180 degrees) of the measured angle range and matches the lower limit value (0 degrees). A value (180 degrees) is output as angle output data. In the case of this type, the lower limit value (0 degree) can be used as the angle output data until it exceeds the upper limit value and matches the lower limit value. This type is suitable when the rotating body rotates only in either the forward or reverse direction.

  In the type 2 shown in FIG. 6B, when the angle data output from the angle calculation circuit 10 exceeds the upper limit value (180 degrees) of the measured angle range, the upper limit value + α (α is the value in this figure). Within the range of 90 degrees in the example, the upper limit value is output as angle output data, and the lower limit value is output as angle data between the lower limit value -β (β is 90 degrees in the example of this figure) and the lower limit value. In this case, the values of α and β can be arbitrarily set, but the sum of the values of α and β is smaller than the difference between 360 degrees and the measured angle range. This type is suitable when the rotating body rotates in one or both directions.

  In the rotation angle sensor of the first embodiment, the values of α and β can be stored in the angle conversion circuit 13 through a serial interface.

  In determining whether the signal input to the serial interface terminal in the input signal determination circuit 16 is a signal for communication or a signal for setting a reference point, the reference point setting circuit 11 caused by noise is used. In order to prevent malfunction, a signal for setting a reference point indicates that the data input terminal (MOSI) has also passed a predetermined time (counting of the counter is finished) at a certain voltage level (GND level in the case of FIG. 4). You may add to the judgment that there is.

Example 2
FIG. 7 is a block diagram of the signal processing circuit 20 (IC) of the rotation angle sensor of the present embodiment. The input terminal for setting the reference point is shared with the error signal output terminal ERROR, and the input signal determination circuit 21 is used. Shows an example of supplying a signal from the error signal output terminal ERROR. 2 are the same as those in FIG. 2, and in this embodiment, the operation of the input signal determination circuit 21 is different from that in FIG.

  In a normal operation state, the error terminal ERROR is an output terminal that outputs an error signal, and is connected to the external device 17. Reference numeral 23 denotes an abnormality diagnosis circuit. For example, according to a diagnosis program executed by a CPU constituting a part of the signal processing circuit 5, an abnormality of each component in the signal processing circuit 20 is diagnosed. The error signal is supplied to the error terminal ERROR via the input / output switching circuit 22.

  The input / output switching circuit 22 supplies a signal from the error terminal ERROR to the input signal determination circuit 21 based on a control signal input from an external device via the serial interface circuit 15. As a result, the signal from the abnormality diagnosis circuit 23 is not supplied to the error terminal ERROR and is not supplied to the input signal determination circuit 21. In this state, as described later, the input / output switching circuit 22 can supply the output from the abnormality diagnosis circuit 23 to the error terminal ERROR based on the control signal from the angle calculation circuit 10. The signal from 23 is not supplied to the input signal determination circuit 21.

  In the signal processing circuit 20 configured as described above, the reference point is set as follows. Hereinafter, a description will be given with reference to FIG.

When a control signal for switching the input / output switching circuit 22 from the external device 17 to supply an external signal to the input signal determination circuit 21 is input via the serial interface circuit 15 (S11). In the determination circuit 21, it is determined whether or not the signal string input from the error terminal ERROR matches a predetermined signal string (for example, a VDD level signal for a predetermined time) (S12). When the input signal sequence matches the predetermined signal sequence, the process proceeds to S6, and thereafter, the same operation as in the first embodiment is performed up to S8. That is, the input signal determination circuit 21 determines that the signal input to the error output terminal ERROR is a signal for setting the reference point, and outputs an ON signal to the angle calculation circuit 10 via the reference point setting circuit 11. In response to this, the angle calculation circuit 10 acquires the output signals from the magnetic sensors 2 and 3 at that time via the A / D converters 8 and 9 (S6), and calculates the internal angle data (S7). The internal angle data is stored in the nonvolatile memory 12 as reference point data (S8). Next, in S9, the input / output switching circuit 22 can be supplied to the error terminal ERROR by the control signal from the angle calculation circuit 10, and the output from the abnormality diagnosis circuit 23 can be supplied to the input signal determination circuit. 21 is not supplied.
The operation of the angle conversion circuit 13 is exactly the same as in the first embodiment.

  In the second embodiment, the example in which one output terminal of the signal processing circuit 20 is used as the reference point setting input terminal has been described. However, for example, when two output terminals are switched to the input terminal, or one input terminal is used. It is also possible to execute the reference point setting procedure using two or more terminals by combining a terminal and a terminal in which one output terminal is switched to an input terminal.

An example of the basic structure of the rotation detection mechanism part of the rotation angle sensor concerning this invention is shown, Comprising: (a) is a bottom view, (b) is a side view. It is a block diagram of the signal processing circuit (IC) of the rotation angle sensor of the Example of this invention. It is a figure which shows an example of the signal waveform of each terminal into which data was input from the external device via the serial interface. It is a figure which shows an example of the signal waveform of each terminal into which the signal for a reference point setting was input from the external device via the serial interface. It is a flowchart which shows the control procedure of the signal processing circuit for judging whether the signal input into the serial interface terminal is a signal for communication, or a signal for a reference point setting. It is a figure explaining the method of angle output data conversion in case the angle data output from the angle calculation circuit are outside the angle range between the upper limit value and lower limit value of the angle to be measured. It is a block diagram of the signal processing circuit (IC) of the rotation angle sensor of the other Example of this invention. It is a flowchart which shows the other control procedure of a signal processing circuit.

Explanation of symbols

2, 3 Magnetic sensor 6, 7 Amplifier 8, 9 A / D converter 10 Angle calculation circuit 11 Reference point setting circuit 12 Non-volatile memory 13 Angle conversion circuit 14 Angle output circuit 15 Serial interface circuit 16 Input signal determination circuit 17 External device

Claims (5)

A rotating body having a magnet;
A plurality of magnetic sensors for detecting the strength of the magnetic field of the magnet that changes in accordance with the rotation of the rotating body and outputting a signal having a value corresponding to the rotation angle of the rotating body;
An angle calculation circuit for calculating a rotation angle of the rotating body from signals output from the plurality of magnetic sensors;
An input signal determination circuit for determining whether or not a signal input to at least one terminal connected to an external device is a predetermined signal for starting reference point setting;
When it is determined that the signal input to the at least one terminal by the input signal determination circuit is a predetermined signal for starting the reference point setting, the signal from the angle calculation circuit obtained in response to the determination Storage means for storing the rotation angle of the rotating body as reference point data;
An output means for outputting a value obtained by subtracting the reference point data in the storage means from the rotation angle calculated by the angle calculation circuit or a value obtained by adding a constant value to the subtracted value as a rotation angle measurement value; the equipped,
The at least one terminal is a signal output terminal;
The rotation further comprising an input / output switching circuit that functions as an input terminal capable of inputting a predetermined signal for temporarily disconnecting the signal output terminal from the signal output means and starting the setting of an external reference point Angle sensor. In claim 1,
The rotation angle sensor, wherein the at least one terminal is connected to a serial interface. In claim 1 ,
The rotation angle sensor, wherein the signal output terminal is an error output terminal. A rotating body having a magnet;
A plurality of magnetic sensors for detecting the strength of the magnetic field of the magnet that changes in accordance with the rotation of the rotating body and outputting a signal having a value corresponding to the rotation angle of the rotating body;
An angle calculation circuit for calculating a rotation angle of the rotating body from signals output from the plurality of magnetic sensors;
An input signal determination circuit for determining whether or not a signal input to at least one terminal connected to an external device is a predetermined signal for starting reference point setting;
When it is determined that the signal input to the at least one terminal by the input signal determination circuit is a predetermined signal for starting the reference point setting, the signal from the angle calculation circuit obtained in response to the determination Storage means for storing the rotation angle of the rotating body as reference point data;
An output means for outputting a value obtained by subtracting the reference point data in the storage means from the rotation angle calculated by the angle calculation circuit or a value obtained by adding a constant value to the subtracted value as a rotation angle measurement value; ,
Among the rotation angle measurement values from the output means, a value within a predetermined angle range is output as it is, and a value outside the angle range is converted into a predetermined value and output .
The at least one terminal is a signal output terminal;
The rotation further comprising an input / output switching circuit that functions as an input terminal capable of inputting a predetermined signal for temporarily disconnecting the signal output terminal from the signal output means and starting the setting of an external reference point Angle sensor.   In claim 4,
  The rotation angle sensor, wherein the signal output terminal is an error output terminal.

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