WO2024134705A1 - Magnetic rotary encoder and backup control method therefor - Google Patents

Abstract

The present invention comprises: a processing unit for a first magnetic sensor signal that, in order to generate highly precise rotation angle information as position information for backup control on the occasion of failure of a first magnetic sensor using an output signal from a second magnetic sensor which is less precise and cheaper than the first magnetic sensor, generates first analog data and first digital data pertaining to the rotation angle of an axis of rotation on the basis of the output of the first magnetic sensor; and a processing unit for a second magnetic sensor signal that generates second analog data and second digital data pertaining to the axis of rotation on the basis of AD conversion data for the output of the second magnetic sensor. The second magnetic sensor has a lower resolution than the first magnetic sensor, the output of the second magnetic sensor is calibrated on the basis of the output of the first magnetic sensor, and the second analog data and the second digital data pertaining to the second magnetic sensor are calibrated on the basis of a calibration history of the second magnetic sensor as a fail-safe function for a rotary encoder.

Description

Magnetic rotary encoder and backup control method thereof Technical Background

The present invention relates to a magnetic rotary encoder and a backup control method thereof, and to a magnetic rotary encoder with a backup function in the event of failure of a magnetic sensor or loss of power, and to a backup control method.

Rotary encoders are used to detect the angular position and rotational speed of a rotating shaft driven by a rotating electric machine. In particular, for a motor, such as a brushless DC motor, absolute digital signals and incremental digital signals related to the angular position are generated and output based on the angular position and rotational speed of the rotating shaft detected by a magnetic sensor, and these signals are used to control the motor as a servo motor. Rotary encoders used to control equipment such as industrial robots where system redundancy is important are provided with a backup control function (fail-safe function) that uses other normal magnetic sensors so that the equipment can continue to operate safely even if the rotary encoder breaks down during operation.

The rotation angle detection device disclosed in Patent Document 1 has a magnetic flux detection unit that includes three or more rotation angle sensors using magnetic detection elements such as MR elements or Hall elements, and a rotation angle derivation unit that calculates the rotation angle of the output shaft based on the rotation of the rotation angle sensors other than the rotation angle sensor that has been determined to be abnormal.

Patent Document 2 discloses an invention in which, in a motor rotation angle detection device equipped with a GMR sensor and an AMR sensor, under normal circumstances, the output of the AMR sensor is corrected using the output of the GMR sensor to determine the mechanical angle θ, and in the event of a failure of the GMR sensor, the mechanical angle θ is detected using only the output of the AMR sensor to execute backup control. The microcomputer is equipped with a counter, and when it determines that it is time to perform offset correction based on the output of the GMR sensor, it records the counter value as 1 in the counter, and in the event of a failure of the GMR sensor, it performs offset correction on the output value of the AMR sensor based on this counter value.

The encoder with an optical or magnetic angle detection unit disclosed in Patent Document 3 includes a primary battery, such as a battery, button cell, or dry cell, and a rechargeable secondary battery. This secondary battery is charged by an electric signal generating unit that uses a magnetosensitive wire, such as a Wiegand wire, and the invention disclosed is capable of detecting at least a portion of the rotational position information of the rotating shaft (e.g., multi-rotation information) even when the main power supply of the device in which the encoder device is mounted is not turned on (emergency state, backup state).

JP 2022-164402 A JP 2022-105702 A JP 2016-109554 A

In the invention of Patent Document 1, if one rotation angle sensor of a rotation angle detection device is determined to be abnormal, the rotation angle of the output shaft can be calculated based on the rotation of only the other normal rotation angle sensors. Therefore, various industrial machines controlled by this rotation angle detection device have the advantage that they can continue to operate safely even if one rotation angle sensor becomes abnormal. On the other hand, the invention of Patent Document 1 requires that three or more rotation angle sensors with the same type and characteristics be used, and if high-precision rotation angle sensors are used, the overall cost may increase. Depending on the application of various industrial machines, etc., there are also fields where backup control is required using cheaper rotation angle sensors that are less prone to failure.

In the invention of Patent Document 2, the GMR sensor and AMR sensor are arranged at 180 degree intervals, so an offset occurs between the output of the GMR sensor and the output of the AMR sensor. Therefore, when the GMR sensor fails, the output value of the AMR sensor is offset corrected based on this counter value. However, this offset occurs due to the special structure in which the GMR sensor and AMR sensor are arranged at 180 degree intervals. Furthermore, Patent Document 2 does not mention making any correction other than the above offset correction when the GMR sensor fails.

In the invention of Patent Document 3, the power supply system is equipped with a power supply switch (power supply selection section, selection section), and this power supply switch is configured to switch (select) whether power is supplied to the position detection system from a primary battery or a secondary battery charged by an electrical signal generating unit. However, if the power supply switch fails, there is a possibility that power will not be supplied appropriately to the position detection system.

One object of the present invention is to provide a magnetic rotary encoder and a backup control method thereof which can generate highly accurate rotation angle information using the output signal of a first magnetic sensor under normal conditions, and generate relatively highly accurate rotation angle information by using the output signal of a second magnetic sensor which is less accurate than the first magnetic sensor but less expensive as position information for backup control in the event that the first magnetic sensor fails.
Another object of the present invention is to provide a magnetic rotary encoder equipped with a backup control function that can properly record information on the rotation angle of the motor's shaft even during a power outage, and properly provide the necessary information the next time the motor is started.

According to one aspect of the present invention, a rotary encoder includes:
A magnet fixed to the rotating shaft;
a first magnetic sensor signal processing unit that performs AD conversion on a first analog signal that is an output of a first magnetic sensor disposed opposite the magnet, and generates first digital data including two types of information, an absolute signal and an incremental signal, related to a rotation angle and a rotation direction of the rotating shaft, based on the AD converted data of the output of the first magnetic sensor;
a second magnetic sensor signal processing unit that performs AD conversion on a second analog signal that is an output of a second magnetic sensor disposed opposite to the magnet, and generates second digital data including two types of information, an absolute signal and an incremental signal, related to the rotation angle and the rotation direction of the rotating shaft, based on the AD converted data of the output of the second magnetic sensor,
the second magnetic sensor has a lower resolution than the first magnetic sensor;
the second magnetic sensor signal processing unit has a fail-safe function that backs up the first magnetic sensor signal processing unit,
The second magnetic sensor signal processing unit includes:
calibrating the second analog signal of the second magnetic sensor based on data of the first analog signal of the first magnetic sensor to perform the AD conversion, and calibrating the AD converted data of an output of the second magnetic sensor based on the first digital data of the first magnetic sensor to generate the second digital data;
a function of recording a calibration history of the second analog signal and a calibration history of the second digital data;
The fail-safe function of the rotary encoder is
When the first magnetic sensor and/or the processing unit for the first magnetic sensor signal fails, the second analog signal of the second magnetic sensor is calibrated based on a calibration history of the second analog signal, and the second digital data of the second magnetic sensor is calibrated based on a calibration history of the second digital data.

According to one aspect of the present invention, a rotary encoder can be provided that uses a second magnetic sensor, which is less accurate than the first magnetic sensor but is inexpensive, to generate relatively accurate position information, enabling highly reliable backup control.

According to another aspect of the present invention, the first magnetic sensor is arranged on a printed circuit board at a position corresponding to the axis of the rotating shaft, the second magnetic sensors are arranged on the same side of the printed circuit board as the first magnetic sensor and on a circumference centered on the axis of the rotating shaft, at 120 degree intervals, and one temperature sensor is arranged on the printed circuit board.
The rotary encoder includes, as power supply units, a main power supply, a Barkhausen effect power supply, and a sub-battery, whose output voltage is controlled to a predetermined power. The Barkhausen effect power supply and the sub-battery are power supplies that provide backup power in the event that the main power supply is lost. The Barkhausen effect power supply is provided on the printed circuit board so as to be located on the back side of the first magnetic sensor, and includes a Barkhausen effect element that generates power by utilizing the rotating magnetic field of the magnet. The sub-battery has a capacitor that is charged by the main power supply and the Barkhausen effect power supply.
According to this aspect, a magnetic rotary encoder can be provided that has a backup control function that can properly record information on the rotation angle of the motor's rotating shaft even if either the first magnetic sensor or the second magnetic sensor fails, and even during a power outage, and can properly provide the information necessary the next time the motor is started.

According to yet another aspect of the present invention, the first analog signal, the second analog signal, the first digital data, and the second digital data are monitored, and if it is determined as a result of monitoring each of the data that there is an abnormality in the first magnetic sensor or the processing unit for the first magnetic sensor signal, in the processing unit for the second magnetic sensor signal, a calibrated analog signal is generated from the second analog signal of the second magnetic sensor based on a calibration history of the second analog signal, and calibrated second digital data is generated based on the calibrated analog signal and calibration data for the second digital data.
According to this aspect, even if the first magnetic sensor fails, highly reliable backup control can be performed.

1 is a functional block diagram showing a configuration example of a rotary encoder according to a first embodiment of the present invention; 1 is a diagram illustrating an example of the configuration of a servo control system including a rotary encoder according to a first embodiment; 2 is a vertical cross-sectional view showing a configuration example of a magnetic sensor and a power supply unit in the rotary encoder of the first embodiment; FIG. FIG. 2 is a diagram illustrating an example of the circuit configuration of a power supply unit in the first embodiment. 10 is a time chart showing the operation of the power supply unit, illustrating an example of the relationship between the power supply and the output signal of the rotary encoder when the main power supply goes from a normal state to a power outage. FIG. FIG. 13 is a diagram illustrating another example of the configuration of the circuit of the power supply unit. FIG. 11 is a diagram showing a process of digitizing and absoluteizing a first magnetic sensor signal. 5 is a flowchart showing signal processing in a processing unit for a first magnetic sensor signal in the first embodiment. 9A and 9B are diagrams showing examples of A-phase and B-phase signals based on the signal processing of FIG. 8, and incremental Z-phase, U-phase, V-phase, and W-phase signals generated based on these signals. FIG. 11 is a diagram showing a process of digitizing and absoluteizing a second magnetic sensor signal. 6 is a flowchart showing signal processing in a second magnetic sensor signal processing unit in the first embodiment. 4 is a flowchart showing a process of a fail-safe control unit in the first embodiment. 10 is a flowchart showing data processing of a processing unit for a second magnetic sensor signal during normal operation. 13 is a flowchart showing data processing of a second magnetic sensor signal processing unit in a fail-safe mode.

A first embodiment of the present invention will now be described with reference to the drawings.
First, the overall configuration and functions of a rotary encoder according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a functional block diagram showing an example of the configuration of a rotary encoder, and FIG. 2 is a diagram showing an example of the configuration of a servo control system equipped with this rotary encoder.
The rotary encoder 10 includes a magnetic sensor unit 11, a power supply unit 12, a temperature sensor 13, a system control unit 14, a first magnetic sensor signal processing unit 15, and a second magnetic sensor signal processing unit 16.
The rotary encoder 10 further includes one flat magnet 110 magnetized with one pole each of N and S. This flat magnet is, for example, a ferrite magnet, and is fixed to one end surface of the rotating shaft 510 of the motor 50 as shown in Fig. 3. Note that a rare earth magnet such as a neodymium magnet or a samarium-cobalt magnet may be used instead of the ferrite magnet.
The magnetic sensor unit 11 includes a first magnetic sensor 111 and a second magnetic sensor 112 , and the first magnetic sensor 111 includes a temperature sensor 113 .
The first magnetic sensor 111 is composed of a pair of magnetic sensors (Sin, Cos), and is disposed in a position facing the magnet 110 in the axial direction of the rotating shaft 510. That is, the first magnetic sensor 111 is disposed on the printed circuit board 17 in a position corresponding to the axis O-O of the rotating shaft 510.

The first magnetic sensor 111 used in the present invention is a sensor that can obtain high-precision resolution, and the second magnetic sensor is preferably a magnetic sensor that has a lower resolution than the first magnetic sensor but has a simple structure and is less likely to break down.
In the first embodiment, a TMR sensor is used as the first magnetic sensor 111, and three Hall elements (H1, H2, H3) arranged at 120 degree intervals are used as the second magnetic sensor 112. For example, GaAs elements are used for the Hall elements. The TMR sensor includes a built-in temperature sensor, and its output is temperature compensated.

The power supply unit 12 includes a main power supply 121, a Barkhausen effect power supply 122, and a sub-battery 123. The Barkhausen effect power supply 122 and the sub-battery 123 function as power supplies that supply power to the rotary encoder 10 when the main power supply is lost. A Barkhausen effect power supply unit 115 is installed near the magnet 110. This Barkhausen effect power supply unit 115 is fixed to the printed circuit board 17 at a position that is the back surface of the first magnetic sensor 111 (see FIG. 3). This Barkhausen effect power supply unit 115 has a compound magnetic wire and a coil. This compound magnetic wire is centered on the axis O-O and is arranged in a direction perpendicular to this axis. The Barkhausen effect power supply unit 115 generates power by the Barkhausen effect in response to the magnetic flux Φb of the flat magnet 110 as the rotating shaft 510 rotates, and this output is supplied to the Barkhausen effect power supply 122.

The system control unit 14 has a function of outputting information from the first magnetic sensor signal processing unit 15 as the output of the rotary encoder 10 when the first magnetic sensor 111 and the first magnetic sensor signal processing unit 15 are functioning normally, and outputting information from the second magnetic sensor signal processing unit 16 when an abnormality occurs in the first magnetic sensor 111 and the first magnetic sensor signal processing unit 15.

The initial setting section 141 of the system control unit 14 has a setting section 142 that sets the motor type, number of poles, origin of the rotation axis, output conditions of the rotary encoder, etc. according to conditions input via a user interface, and a function for retaining fail-safe control data 143. The fail-safe control data 143 includes, for example, data on trigonometric functions used to calibrate the analog output of the second magnetic sensor based on the analog output of the first magnetic sensor for data calibration, and data on linear functions used to calibrate the digital of the second magnetic sensor based on the digital output of the first magnetic sensor.

The encoder input/output control unit 144 has a function of controlling the input/output of the rotary encoder 10 according to initially set conditions. The fail-safe control unit 145 controls the fail-safe mode that is executed when a magnetic sensor or other device fails. The output switching unit 146 has a function of switching the output of the rotary encoder according to the operating state of the rotary encoder. The serial/parallel signal transmitting/receiving unit 147 has a function of converting various types of information into parallel or serial signals and transmitting/receiving them between the rotary encoder 10 and the servo control device 40.

The rotary encoder 10 of the present invention can be applied to various rotating electrical machines that require absolute data and incremental A, B, and Z data.

The following will more specifically describe a configuration in which the present invention is applied to a rotary encoder for a brushless DC motor.
The processing unit 15 of the first magnetic sensor signal performs AD conversion on the first analog signal, which is the output of the first magnetic sensor arranged opposite to the magnet 110, and generates first digital data related to the rotation angle and rotation direction of the rotating shaft based on the AD conversion data of the output of the first magnetic sensor. That is, the processing unit 15 of the first magnetic sensor signal has a function of generating two types of information, that is, a high-resolution (e.g., 27 bit/revolution) absolute signal and an incremental signal, which are quantized under a predetermined condition, as first digital data with high accuracy with respect to the rotation angle information of the rotating shaft. For example, incremental A, B, Z, (U, V, W) signals are converted from the rotary encoder as the first digital data into transmission data (BUS) for serial transmission and transmitted to the servo control device via a communication cable.

The second magnetic sensor signal processing unit 16 also performs AD conversion on the second analog signal, which is the output of the second magnetic sensor arranged opposite the magnet 110, and generates second digital data related to the rotation angle and direction of the rotating shaft based on the AD converted data of the output of the second magnetic sensor. In other words, the second magnetic sensor signal processing unit 16 has the function of generating and outputting two types of information, an absolute signal and an incremental signal with a relatively high resolution (e.g., 21 bits/revolution), with high precision as second digital data, regarding the rotation angle information of the rotating shaft, in which the analog output of the second magnetic sensor 112 is corrected based on the correction history for the signal generated by the first magnetic sensor signal processing unit and quantized under predetermined conditions.

The first magnetic sensor signal processing unit 15 includes an analog signal (sin, cos)/amplitude detection section 151 , which is a first analog signal processing section, an AD converter 152 , and a digital signal processing section 153 .
The analog signal (sin, cos)/amplitude detection unit 151 receives sampling data of the first analog signal (sin signal, cos signal) of the first magnetic sensor 111 as time-series data, calculates the number of rotations, and temporarily records in memory the rotation angle (mechanical angle) and amplitude of these analog signals, the number of rotations Nx of the rotating shaft, and the data of the temperature sensor 13 in association with each other. At the same time, the sampling data of the analog signal of the first magnetic sensor 111 is input to, for example, a 64-bit AD converter 152 (ADC-1 (sin) 1521, ADC-2 (cos) 1522) and converted into digital values, and these converted values are recorded in the EEPROM-1 (1523) as time-series data.

The first magnetic sensor absolute signal generating unit 1532 of the digital signal processing unit 153 obtains AD converted data of the rotating shaft from the EEPROM-1, generates an absolute signal of the rotation angle of the rotating shaft, and records it in the EEPROM-2 as time-series data.
Moreover, the digital signal/frequency/rotation direction detection unit 1531 of the first magnetic sensor obtains a digital value from the EEPROM-1, calculates its frequency, and records it together with the rotation direction data in the EEPROM-2.
On the other hand, the incremental A, B, Z, (U, V, W) signal generating unit 1533 of the first magnetic sensor obtains the digital value of the absolute signal of the rotation angle of the rotating shaft from EEPROM-2 as the first digital data, generates incremental A, B, Z, (U, V, W) signals, and records them in EEPROM-3 as time-series data.

The second magnetic sensor signal processing unit 16 includes an analog signal processing section 160 , an AD converter 162 , and a digital signal processing section 163 .
The distortion correction/amplitude/synchronization correction unit 161 for the analog signal of the second magnetic sensor receives sampling data of the second analog signal (sine signal of H1, sine signal of H2, sine signal of H3) of the second magnetic sensor 112 as time-series data, performs distortion correction corresponding to the eccentricity of each Hall element (H1, H2, H3) with respect to the axis O-O, calculates the rotation speed, and records it in memory.
On the other hand, the rotation angle (mechanical angle) and amplitude of the first analog signal of the first magnetic sensor 111, the number of rotations Nx, and data of the temperature sensor 13 are acquired from the analog signal (sin, cos)/amplitude detection section 151 of the first magnetic sensor signal processing unit 15. Then, these data are correlated and temporarily recorded in memory.
Furthermore, the data for each revolution of the second analog signal of the second magnetic sensor 112 is subjected to amplitude correction and synchronization correction, i.e., data calibration, based on the rotation angle (mechanical angle) and amplitude of the first analog signal, the number of revolutions Nx, and the data of the temperature sensor 13, and the calibrated analog data is recorded in the EEPROM-4 (165) together with the correction history.
In addition, the second analog signal may be subjected to amplitude correction and synchronization correction for each signal corresponding to each Hall element (H1, H2, H3) individually with the first analog signal. However, in order to speed up processing, it is preferable to perform amplitude correction and synchronization correction for all the signals together.

Furthermore, if an approximation of a trigonometric function related to the data of the temperature sensor 13 is used to calibrate the data of the second analog signal, it is not necessary to calibrate the data for each rotation, but it can be performed in a predetermined angle range or sampling unit, etc. In other words, the data of the second analog signal at any rotation angle of the second magnetic sensor 112 can be directly calibrated based on the data of the first analog signal of the first magnetic sensor 111 in a corresponding positional relationship, based on the preset data of the relationship between the approximation of a trigonometric function and the temperature sensor 13.
The calibrated analog data is input to, for example, a 64-bit AD converter 162 (ADC-3 to 5 (1621-1623)) and converted into digital values, and these converted values are recorded in an EEPROM-5 (1624) as time-series data.
In a "fail-safe mode" in which the first magnetic sensor 111 or the processing unit 15 for the first magnetic sensor signal has failed, the fail-safe/signal correction unit 164 performs amplitude and synchronization correction of the second analog signal of the second magnetic sensor based on the correction history recorded in the EEPROM-4 (165), and records the result in the EEPROM-4 (165) as calibrated analog data.

The second magnetic sensor absolute signal generating unit 1632 of the digital signal processing unit 163 acquires AD conversion data for each rotation of the rotating shaft from the EEPROM-5, generates an absolute signal of the rotation angle of the rotating shaft, and records it in memory as time-series (provisional) absolute data. This (provisional) absolute data is calibrated in the second magnetic sensor digital signal detection and frequency/rotation direction correction unit 1631. In other words, the second magnetic sensor digital signal detection and frequency/rotation direction correction unit 1631 acquires the frequency/rotation direction data of the digital signal for each rotation of the first magnetic sensor generated by the first magnetic sensor digital signal frequency/rotation direction detection unit 1531, performs synchronization and rotation direction correction of the time-series absolute data of the second magnetic sensor, and records the result in the EEPROM-7 as second digital data, i.e., the second magnetic sensor's (formal) absolute data. In addition, the correction history of the absolute data is recorded in EEPROM-6 (166).

If an approximation of a linear function is used to calibrate the data, it is not necessary to calibrate the data for each rotation, but it can be done within a specified angle range. In other words, the second digital data at any rotation angle of the second magnetic sensor 112 can be calibrated based on the first digital data of the first magnetic sensor 111, which is in a corresponding positional relationship, based on a preset approximation of a linear function and the data of the temperature sensor 13.

On the other hand, the incremental A, B, Z, (U, V, W) signal generating unit 1633 of the second magnetic sensor obtains the digital value of the calibrated absolute signal of the rotation angle of the rotating shaft from the EEPROM-7, generates incremental A, B, Z, (U, V, W) signals, and records them in the EEPROM-8 as time-series data.
In the "fail-safe mode," the AD conversion data for each rotation of the rotating shaft obtained from EEPROM-5 is used to correct the frequency/rotation direction of the absolute data of the second magnetic sensor based on the correction history of the absolute data recorded in EEPROM-6, and the result is recorded in EEPROM-6 as a calibrated digital value/correction history.

1 are merely examples. The functional blocks may be divided in any way, and it goes without saying that the functional blocks may be realized by a common program, or a specific functional block may be realized by a plurality of different programs or IC circuits.
Alternatively, each of the above functions can be realized by installing a program for executing each of the above functions in a microcomputer having a CPU and memory.

As shown in FIG. 2, the rotary encoder 10, together with the servo control device 40 and the motor 50, constitutes a servo control system.

Most of the rotary encoder 10, i.e., the magnetic sensor unit 11 except for the flat magnet 110, the power supply unit 12, the temperature sensor 13, the system control unit 14, the first magnetic sensor signal processing unit 15, and the second magnetic sensor signal processing unit 16, are formed or mounted on a printed circuit board 17. This printed circuit board is fixed to a housing (not shown) of the motor 50.
In particular, the system control unit 14, the first magnetic sensor signal processing unit 15, and the second magnetic sensor signal processing unit 16 are realized as a dedicated FPGA 18 (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit), or as an IC circuit chip using a general-purpose single-chip microcomputer, and are formed on a printed circuit board 17.
The system control unit 14, the first magnetic sensor signal processing unit 15, and the second magnetic sensor signal processing unit 16 are functionally divided blocks, and these functions are realized by writing programs in the digital signal processing unit, SSC interface, incremental interface, etc. of the FPGA or ASIC.
The FPGA includes a ROM, a RAM, and at least one rewritable (overwritable) nonvolatile memory, and is connected to the CPU via a bus. As the rewritable (overwritable) nonvolatile memory, an EEPROM or FRAM (Ferroelectric Random Access Memory, (registered trademark)) may be used. In the following description, such a memory will be simply referred to as an EEPROM.

The pair of magnetoresistance effect elements constituting the first magnetic sensor 111 are arranged at a predetermined interval in the direction of rotation of the rotating shaft so that the phases of the output analog signals are shifted by 90 degrees from each other. A TMR (Tunnel magnetoresistance effect) element is used as the first magnetic sensor 111. The first magnetic sensor 111 senses the magnetic flux Φa of the flat magnet 110 as the rotating shaft 510 rotates, and outputs a sine wave and a cosine wave.

The position of one end of the boundary line between the north pole region and the south pole region of magnet 110 is a specific position in the circumferential direction on the rotation shaft, that is, the origin position (Z ₀ ) corresponding to the rising point of the A-phase pulse.

The three Hall elements of the second magnetic sensor 112 are arranged at equal intervals on the printed circuit board 17, radially outside the first magnetic sensor 111. Hall ICs may be used instead of these Hall elements. Hereinafter, the Hall elements or Hall ICs will simply be referred to as "Hall elements."

Next, an example of the circuit configuration of the power supply unit in the first embodiment will be described with reference to FIG.
The main power supply 121 of the power supply unit 12 includes a main power supply section 1211 in which power supplied from, for example, a commercial power supply is converted into DC power and controlled to a predetermined DC voltage Vcc, for example, 5 V. This main power supply section 1211 supplies power to an output terminal 124 via a diode 1221.

The Barkhausen effect power generation power supply 122 outputs a positive and negative pulse waveform at 180 degree intervals for each rotation of the rotating shaft from the Barkhausen effect power generation unit 115. This power is supplied to the output terminal 124 via a full-wave waveform circuit 1222, a smoothing circuit 1223, and a diode 1231 as DC power of a predetermined voltage Vcc.
The sub-battery 123 includes a current limiting circuit 1232, a capacitor 1233, and a voltage limiting circuit 1234, and supplies DC power of a predetermined voltage Vcc to the output terminal 124. The capacitor 1233 is supplied with power from both the main power supply 121 and the Barkhausen effect power generation power supply 122 individually. The capacitor 1233 functions as a power supply that supplies power to the rotary encoder 10 when the power supply from the main power supply is lost and the rotation of the rotating shaft is also stopped. The current limiting circuit 1232 controls the capacitor 1233 so that an allowable range of charge is accumulated in the capacitor 1233 by limiting the current supplied to the capacitor 1233 when the motor rotation speed is high and the amount of power generated by the Barkhausen effect power generation unit 115 is large. For example, an electric double layer capacitor may be used as the capacitor 1233. The capacitor 1233 may be configured by connecting multiple capacitors in parallel in order to make the voltage drop gentle.
The power supply line connected to the output terminal 124 of the power supply unit 12 is configured as three electrically independent lines, and power is supplied to the system control unit 14, the first magnetic sensor signal processing unit 15, the second magnetic sensor signal processing unit 16, and each sensor of the magnetic sensor unit 11.

FIG. 5 is a time chart showing the operation of the power supply unit, and is a diagram showing an example of the relationship between the power supply and the output signal of the rotary encoder when the main power supply goes from a normal state to a power outage.
When the main power supply unit 1211 of the main power supply is unable to supply power at time t1, for example due to a power outage or malfunction, power is supplied to the rotary encoder 10 from the Barkhausen effect power generation power supply 122 which generates power as the rotating shaft rotates.

As the rotation speed of the rotating shaft decreases over time after the power outage, the output of the Barkhausen effect power generation decreases, and at time t2, it becomes impossible to supply DC power of the specified voltage Vcc. When this state occurs, the charge stored in the capacitor 1233 of the sub-battery 123 supplies power of the voltage Vcc to the rotary encoder 10.
This allows the rotary encoder 10 to generate and record information on the rotation angle of the rotating shaft for a long period of time, for example, until time t3 when the rotation of the rotating shaft completely stops.
Furthermore, if the rotating shaft is forcibly rotated by an external force, for example, human force, via a robot arm after the rotating shaft has stopped due to a power outage, power is supplied to the rotary encoder 10 from time t4 to t5 by the output of the Barkhausen effect power generation and the charge stored in the capacitor 1233. Therefore, even if the rotating shaft is rotated by an external force after the rotating shaft has stopped due to a power outage, information on the rotation angle of the rotating shaft is recorded.

Next, Fig. 6 is a diagram showing another example of the configuration of the circuit of the power supply unit. Instead of the current limiting circuit 1232 in Fig. 4, a MOSFET 1236 controlled by a PWM control unit 1235 is adopted, and the current supplied from the Barkhausen effect power generating unit 115 to the capacitor 1233 is PWM controlled. Reference numeral 1237 denotes a resistor for current detection. The capacitor 1233 is supplied with power individually from both the main power supply 121 and the Barkhausen effect power generating source 122. In this example, the MOSFET 1236 is PWM controlled according to the detected values of the charging voltage and current of the capacitor 1233, and the charge stored in the capacitor 1233 is controlled to be an optimal value.
In this example as well, the rotary encoder 10 can generate and record information on the rotation angle of the rotating shaft for a long period of time, for example, until the rotation of the rotating shaft stops or until it is subsequently driven by an external force.

Next, the process of digitizing and converting the first magnetic sensor signal into an absolute value in the first magnetic sensor signal processing unit 15 will be described with reference to FIGS.
The first magnetic sensor signal processing unit 15 obtains information on the number of poles of the motor and the origin of the rotation shaft from the initial setting values (S701).
7A, the first magnetic sensor (TMR sensor) 111 outputs a first analog signal of 360 degrees (mechanical angle) each for one period of a sine wave and a cosine wave in response to one rotation of the rotating shaft. The data of the rotation angle (mechanical angle) and amplitude of these first analog signals, and the number of rotations Nx, are correlated with the temperature Ta of the temperature sensor 13 by the analog signal (sin, cos)/amplitude detection section 151 of the first magnetic sensor signal processing unit 15, and recorded in memory. Generally, such processing is necessary since Hall elements are more susceptible to the influence of the ambient temperature than TMR sensors.

Here, assuming that the first analog signal output from the first magnetic sensor (TMR sensor) is an accurate sine wave, if the displacement y1 (i.e., amplitude) at time t and position x is y1(x, t), y1(x, t) can be expressed by the following equation.
y1 (x, t) = Asin2π (t/T-x/λ) (1)
where T is the period, λ is the wavelength, and A is a constant.
The actual analog signal output from the first magnetic sensor is temperature compensated and can be considered to be close to the above equation (1).
Therefore, an approximate trigonometric function y1(x, t, Ta) expressing the relationship between the sine wave and cosine wave of the actual analog signal output from the first magnetic sensor and the substrate temperature Ta can be obtained in advance and stored as initial setting data. Using this approximate trigonometric function, data on the rotation angle (mechanical angle) and amplitude of the first analog signal, and the number of rotations Nx can be generated. This makes it possible to generate highly accurate calibration data for the second analog signal over a wide range from low rotation speeds to high rotation speeds.

As shown in FIG. 7B, the analog signals (sine signal, cosine signal) are input to an AD converter 152, quantized, and converted into a multi-divided digital signal by an interpolation process, and then converted into digital values containing information on phases A and B. These converted values are correlated with the rotation speed Nx and temperature Ta, and are recorded in the EEPROM-1.
As shown in the flowchart of Fig. 8, the first magnetic sensor signal processing unit 15 obtains AD converted data of the first magnetic sensor signal (sine and cosine waves) from the EEPROM-1 (S702). The first magnetic sensor signal processing unit 15 further performs time division or other interpolation on the digital waveform based on the AD converted data of the first analog signal (sine signal, cosine signal) as necessary, converts it into, for example, 27-bit data of a rotation angle indicating an absolute position from the origin, and calculates it as an absolute value (S703). Then, the absolute value is assigned a memory address and recorded in the memory (S704).
That is, as shown in FIG. 7C, the digital signal/frequency/rotation direction detection unit 1531 of the first magnetic sensor calculates the frequency for each rotation of the rotating shaft in either direction based on the digital value in EEPROM-1, generates an absolute value for each rotation in either direction, and records this in EEPROM-2 together with the rotation speed Nx, temperature Ta, and rotation direction data.

Here, assuming that the first analog signal output from the first magnetic sensor is an accurate sine wave, and the absolute value obtained based on the digital value of EEPROM-1 is y2(x, t), y2(x, t) can be expressed as a linear function related to the temperature Ta.
That is, the absolute value as shown in FIG. 7C based on the actual analog signal output from the first magnetic sensor can also be approximated by the linear function. Therefore, an approximation formula for the absolute value based on the sine wave and cosine wave of the actual analog signal output from the first magnetic sensor according to the temperature Ta can be obtained in advance and stored as initial setting data. The approximation formula for the absolute value can be used to generate the absolute value for each forward and reverse rotation. This makes it possible to generate highly accurate absolute data calibration data over a wide range from low speed rotation to high speed rotation.

Furthermore, the digital signal/frequency/rotation direction detection unit 1531 of the first magnetic sensor generates multi-rotation information including the rotation direction, rotation angle, and rotation count from the origin information and absolute value, and records this in EEPROM-2 (S711).

The absolute signal generation unit 1532 of the first magnetic sensor calculates the number of rotations from the origin information and the absolute value (S721), generates multi-rotation absolute information, and records it in EEPROM-2 as multi-rotation absolute data (S722).

The incremental A, B, Z (U, V, W) signal generating unit 1533 of the first magnetic sensor calculates A-phase and B-phase data from the AD conversion data and absolute value based on the A-phase and B-phase information shown in FIG. 7B (S731), and calculates the width data of Z-phase synchronized with the rising edge of A-phase and B-phase (S732). Furthermore, based on the A-phase, B-phase, and Z-phase width data, it generates U-phase, V-phase, and W-phase data as shown in FIG. 9 (S733), assigns addresses to the A-phase, B-phase, Z-phase, U-phase, V-phase, and W-phase data, and records them in EEPROM-3 as incremental data (S734).

Next, the signal processing in the second magnetic sensor signal processing unit in the first embodiment will be described with reference to FIG. 10 and FIG.
From each of the Hall elements H1 to H3 constituting the second magnetic sensor, a sine signal (H1 to H3), a sine signal of H2, and a sine signal of H3) that rises or falls every 180 degrees of one rotation is obtained as a second analog signal as shown by the solid line in Fig. 10(A). This waveform shows data that has been corrected for distortion based on the installation position. The Hall elements as the second magnetic sensor are subject to large fluctuations due to position errors, variations in element characteristics, environmental temperature, etc. The dashed line shown in Fig. 10(A) shows the output of the corresponding first magnetic sensor.
The analog output data of the Hall element is stored in memory in association with the data of the rotation speed Nx and the temperature Ta. The analog output data of the Hall element associated with the data of the temperature Ta can also be expressed by an approximation formula, similar to the above formula (1).

Then, the rotation angle (mechanical angle) and amplitude of the analog signal of the first magnetic sensor 111, the number of revolutions Nx, and the data of the temperature sensor 13 are acquired from the first analog signal (sin, cos)/amplitude detection unit 151 of the processing unit 15 of the first magnetic sensor signal. Then, the data of the second analog signal of the second magnetic sensor 112 for each revolution is subjected to amplitude correction and synchronization correction, that is, data calibration, based on the rotation angle (mechanical angle) and amplitude of the first analog signal, the number of revolutions Nx, and the data of the temperature Ta of the temperature sensor 13, and the calibrated analog data is associated with the data of the number of revolutions Nx and the temperature Ta, and is recorded in the EEPROM-4 (165) together with the correction history. (B) of FIG. 10 shows an example of the calibrated analog data of the second magnetic sensor 112.
As described above, this correction history can also be expressed by the calibrated analog data y2 using an approximate trigonometric function y2(x, t, Ta) representing the sine wave and cosine wave of the first analog signal.
This calibrated analog data is input to the AD converter 162 (ADC-3 to ADC-5) and converted into digital values, and these converted values are recorded in the EEPROM-5 as time-series data.

FIG. 10C shows an example of digitally converted data in which the signal of the second magnetic sensor 112 is converted into a digital value including information on A phase and B phase.
FIG. 10D shows an example of a (provisional) absolute value based on the output of the second magnetic sensor signal. The (provisional) absolute value shown by the solid line includes a phase error that depends on the characteristics of the second magnetic sensor. (Note that the error is shown in an exaggerated manner for ease of understanding.) In particular, it is assumed that the second analog signal is converted to digital without being able to fully eliminate the error caused by the influence of temperature Ta at the stage of the second analog signal. The dashed line shown in FIG. 10D shows the absolute value based on the corresponding output of the first magnetic sensor.

In the digital signal detection and frequency/rotation direction correction section 1631 of the second magnetic sensor signal processing unit 16, multi-rotation information including the rotation direction, rotation angle, and rotation count is generated from the origin information and absolute value, and recorded in the EEPROM-7 (S911 in FIG. 11).
That is, the second magnetic sensor digital signal detection and frequency/rotation direction correction unit 1631 acquires the frequency/rotation direction data of the digital signal for each rotation of the first magnetic sensor generated by the first magnetic sensor digital signal and frequency/rotation direction detection unit 1531, performs synchronization and rotation direction correction on the (provisional) absolute data of the second magnetic sensor in time series, and records the result as the (formal) absolute data of the second magnetic sensor in EEPROM-7. In addition, the correction history of the absolute data is recorded in EEPROM-6.
Fig. 10(E) shows an example of a (formal) absolute value based on the output of the second magnetic sensor signal. The absolute value in Fig. 10(E) can also be approximated by a linear function as described above.

11, the second magnetic sensor signal processing unit 16 obtains information on the number of poles of the motor and the origin of the rotating shaft from the initial setting (S901). From the initial setting, trigonometric function approximation and linear function data for data calibration can also be obtained.
The second magnetic sensor signal processing unit 16 then obtains calibrated AD conversion data of the second magnetic sensor signal (sine wave) from the EEPROM-6 (S902). Based on the AD conversion data, the digital waveform is interpolated by time division or the like as necessary, and converted into, for example, 23-bit data of a rotation angle indicating an absolute position from the origin, and a (provisional) absolute value is calculated (S903). Then, the (provisional) absolute value is assigned a memory address and recorded in the memory (S904).

The absolute signal generation unit 1632 of the second magnetic sensor of the digital signal processing unit 163 calculates the number of rotations from the origin information and the absolute value (S921), generates multi-rotation absolute information, and records it in the EEPROM-7 as multi-rotation absolute data (S922).

The incremental A, B, Z (U, V, W) signal generation unit 1633 of the second magnetic sensor of the digital signal processing unit 163 calculates A-phase and B-phase data from the AD conversion data and absolute value (S931), calculates Z-phase width data synchronized with the rising edge of A-phase and B-phase (S932), generates U-phase, V-phase, and W-phase data based on the A-phase, B-phase, and Z-phase width data (S933), assigns addresses to the A-phase, B-phase, Z-phase, U-phase, V-phase, and W-phase data, and records it in the EEPROM-8 as incremental data (S934).

Next, the processing of the fail-safe control unit 145 in the first embodiment will be described with reference to FIG.
First, information regarding the normality of the data in EEPEOM 1-3 and 4-8 is obtained from the initial setting unit (S1001). Next, the data in EEPEOM 1-3 is monitored for each rotation (S1002). In addition, the data in EEPEOM 4-8 is monitored for each rotation (S1003). Note that data does not have to be monitored for each rotation, and may be monitored at a predetermined time interval, for example.
Next, it is determined whether all the data is normal (S1004), and if normal, normal operation is performed (S1005), and this continues until operation is terminated (S1006, S1007). If in S1004, all the data is not normal, it is next determined whether the data in EEPEOM1 to 3 is normal (S1010), and if normal, an abnormality is displayed for the second magnetic sensor or the processing unit for the second magnetic sensor signal (S1011), and semi-normal operation is performed using the data in EEPEOM1 to 3 (S1012), and this continues until operation is terminated (S1013, S1014). If the data in EEPEOM1-3 is not normal in S1010, then it is determined whether the data in EEPEOM4-8 is normal or not (S1020), and if normal, an error is displayed in the first magnetic sensor or the processing unit for the first magnetic sensor signal (S1021), and fail-safe mode operation is performed using the data in EEPEOM4-8 (S1022), and this continues until operation ends (S1023, S1024). If the data in EEPEOM4-8 is not normal in S1020, an encoder error is displayed (S1030), and operation end processing is performed (S1031, S1032).

Next, data processing (S1101) of the second magnetic sensor signal processing unit during normal operation of the rotary encoder will be described with reference to FIG.
The second magnetic sensor signal processing unit obtains information on the number of poles of the motor and the origin of the rotation shaft from the data processing initial setting of the second magnetic sensor during normal operation (S1012).Then, the second analog signal data of the second magnetic sensor is obtained and distortion correction processing is performed (S1103).Furthermore, the first analog signal data of the first magnetic sensor, which is in a synchronous relationship with the signal of the second magnetic sensor, is obtained (S1104).
Next, the amplitude of the second analog signal data of the second magnetic sensor is calibrated based on the amplitude of the first analog signal data of the corresponding first magnetic sensor (S1105). Then, the calibrated analog signal data of the second magnetic sensor is recorded in EEPROM-4 (S1106). Furthermore, the analog signal correction history is recorded in EEPROM-4 (S1107). Next, the calibrated analog signal data is AD converted by the AD converter 162, and the second digital data is recorded in EEPROM-5 (S1108).
Next, the second digital data of the second magnetic sensor is obtained from the EEPROM-5 (S1109), and the rotation angle and rotation direction of the second digital data of the second magnetic sensor are calibrated based on the rotation angle and rotation direction of the corresponding first digital data of the first magnetic sensor (S1110). Then, the calibrated digital data of the second magnetic sensor is recorded in the EEPROM-6 (S1111). In addition, the correction history of the second digital data is recorded in the EEPROM-6 (S1112). The above process is repeated until the end of operation.

Next, data processing (S1201) of the second magnetic sensor signal processing unit in the fail-safe mode of the rotary encoder will be described with reference to FIG.
First, the number of poles of the motor, information on the origin of the rotation shaft, and fail-safe control data are obtained from the initial setting values (S1202). Next, data on the second analog signal of the second magnetic sensor is obtained (S1203). Furthermore, data on the correction history of the analog signal is obtained from the EEPROM-4 (S1204). Then, the distortion and amplitude of the data on the second analog signal of the second magnetic sensor are calibrated based on the fail-safe control data and the correction history of the analog signal (S1205). Furthermore, the calibrated analog signal data of the second magnetic sensor is recorded in the EEPROM-4 (S1206). Furthermore, the calibrated analog signal data is AD converted by the AD converter 162, and the second digital data is recorded in the EEPROM-5 (S1207).
Next, the second digital data of the second magnetic sensor is obtained from EEPROM-5 (S1208). Meanwhile, the digital data correction history data is obtained from EEPROM-6 (S1209). Then, the rotation angle and rotation direction of the second digital data of the second magnetic sensor are calibrated based on the fail-safe control data and the (digital data) correction history data (S1210). Furthermore, the calibrated digital data of the second magnetic sensor is recorded in EEPROM-6 (S1211). The above process is repeated until the end of operation.

According to an embodiment of the present invention, the second digital data of the second magnetic sensor is calibrated based on the first digital data of the first magnetic sensor, and the second digital data of the second magnetic sensor can be calibrated during backup control based on the calibration history. This makes it possible to provide a rotary encoder that enables highly reliable backup control while employing an inexpensive second magnetic sensor that is not highly accurate.

In addition, as an embodiment of the present invention, an AMR (Anisotropic magnetoresistance effect) element may be used as the second magnetic sensor instead of a Hall element. Alternatively, a GMR (Giant magnetoresistance effect) element may be used. These AMR and GMR sensors are also arranged at equal intervals on a circumference centered on the first magnetic sensor, just like the Hall element example.

The present invention can also be used with other types of motors, such as stepping motors. It can also be widely applied to a variety of motors, including synchronous motors and induction motors. It can also be applied to servo control devices that use these motors.

10 Rotary encoder 11 Magnetic sensor unit 110 Magnet 111 First magnetic sensor 112 Second magnetic sensor 113 Temperature sensor 12 Power supply unit 121 Main power supply 122 Barkhausen effect power supply 123 Sub-battery 13 Temperature sensor 130 Encoder output control unit 14 System control unit 142 Setting unit 143 Fail-safe control data 144 Encoder input/output control unit 145 Fail-safe control unit 146 Output switching unit 147 Serial/parallel signal transmission/reception unit 15 First magnetic sensor signal processing unit 151 First magnetic sensor analog signal (sin, cos)/amplitude detection unit 152 AD converter 1521 ADC-1 (sin)
1522 ADC-2 (cos)
1523 EEPROM-1
153 Digital signal processing unit 1531 Digital signal/frequency/rotation direction detection unit of first magnetic sensor 1532 Absolute signal generation unit of first magnetic sensor
1533 First magnetic sensor incremental A, B, Z, (U, V, W) signal generating unit
16 Second magnetic sensor signal processing unit 160 Analog signal processing unit 161 Distortion correction, amplitude, and synchronization correction unit for analog signal of second magnetic sensor 162 AD converter 163 Digital signal processing unit 1631 Digital signal detection and frequency/rotation direction correction unit for second magnetic sensor 1632 Absolute signal generation unit for second magnetic sensor 1633 Incremental A, B, Z, (U, V, W) signal generation unit for second magnetic sensor 164 Fail-safe and signal correction unit 17 Printed circuit board 18 FPGA
40 Servo control device 50 Motor 510 Rotating shaft H1, H2, H3 Hall element

Claims (9)

A magnet fixed to the rotating shaft;
a first magnetic sensor signal processing unit that performs AD conversion on a first analog signal that is an output of a first magnetic sensor disposed opposite the magnet, and generates first digital data including two types of information, an absolute signal and an incremental signal, related to a rotation angle and a rotation direction of the rotating shaft, based on the AD converted data of the output of the first magnetic sensor;
a second magnetic sensor signal processing unit that performs AD conversion on a second analog signal that is an output of a second magnetic sensor disposed opposite to the magnet, and generates second digital data including two types of information, an absolute signal and an incremental signal, related to the rotation angle and the rotation direction of the rotating shaft, based on the AD converted data of the output of the second magnetic sensor,
the second magnetic sensor has a lower resolution than the first magnetic sensor;
the second magnetic sensor signal processing unit has a fail-safe function that backs up the first magnetic sensor signal processing unit,
The second magnetic sensor signal processing unit includes:
calibrating the second analog signal of the second magnetic sensor based on data of the first analog signal of the first magnetic sensor to perform the AD conversion, and calibrating the AD converted data of an output of the second magnetic sensor based on the first digital data of the first magnetic sensor to generate the second digital data;
a function of recording a calibration history of the second analog signal and a calibration history of the second digital data;
The fail-safe function of the rotary encoder is
a calibration history of the second analog signal of the second magnetic sensor and a calibration history of the second digital data of the second magnetic sensor when the first magnetic sensor and/or a processing unit for the first magnetic sensor signal fails. In claim 1,
the first magnetic sensor is disposed on a printed circuit board at a position corresponding to an axis of the rotating shaft;
the second magnetic sensors are arranged on the same surface of the printed circuit board as the first magnetic sensors, on a circumference centered on the axis of the rotation shaft, and at intervals of 120 degrees;
A rotary encoder comprising: a temperature sensor disposed on the printed circuit board. In claim 2,
the processing unit for the first magnetic sensor signal has a function of AD converting data of the first analog signal of the first magnetic sensor and recording the data, and temporarily recording in a memory a rotation angle (mechanical angle) and amplitude of the first analog signal, a rotation speed Nx, and data of the temperature sensor in association with each other as calibration data for the second analog signal;
The second magnetic sensor signal processing unit includes:
a function of generating calibrated analog data based on the second analog signal of the second magnetic sensor, the amplitude, the number of rotations Nx, and the data of the temperature sensor, and the calibration data of the first magnetic sensor, and a function of recording a calibration history of the calibrated analog data for use in the fail-safe function. In claim 2,
the processing unit for the first magnetic sensor signal has a function of detecting and recording a frequency and a rotation direction of the first digital data of the first magnetic sensor, and temporarily recording in a memory a rotation angle (mechanical angle) and amplitude of the first digital data, a rotation speed Nx, and data of the temperature sensor in association with each other as calibration data for the second digital data;
The second magnetic sensor signal processing unit includes:
a function of calibrating and recording the second digital data of the second magnetic sensor based on a calibration history of the second digital data, and recording the calibration history of the calibrated second digital data for use in the fail-safe function. In claim 2,
the magnet fixed to the rotating shaft is a single flat magnet,
the first magnetic sensor is a pair of TMR sensors disposed on the printed circuit board facing the magnet,
A rotary encoder, wherein the second magnetic sensor is three Hall elements arranged at equal intervals on a circumference centered on the first magnetic sensor. In claim 2,
the magnet fixed to the rotating shaft is a single flat magnet,
the first magnetic sensor is a pair of TMR sensors disposed on the printed circuit board facing the magnet,
A rotary encoder characterized in that the second magnetic sensor is three GMR sensors or AMR sensors arranged at equal intervals on a circumference centered on the first magnetic sensor. In claim 1,
the first magnetic sensor signal processing unit generates, as the first digital data, a first absolute signal and first incremental A, B, Z, (U, V, W) signals based on the AD converted data of the output of the first magnetic sensor;
the second magnetic sensor signal processing unit generates, as the second digital data, a second absolute signal and second incremental A, B, Z, (U, V, W) signals based on the AD converted data of the output of the second magnetic sensor. In claim 2,
The rotary encoder includes, as a power supply unit, a main power supply, a Barkhausen effect power supply, and a sub-battery, the output voltage of which is controlled to a predetermined power,
the Barkhausen effect power generation power supply and the sub-battery are power supplies that perform the backup when the main power supply is lost,
13. A rotary encoder comprising: a sub-battery having a capacitor that is charged by the Barkhausen effect power generation power source. 2. A backup control method for a magnetic rotary encoder according to claim 1, comprising:
monitoring the first analog signal, the second analog signal, the first digital data, and the second digital data;
When it is determined as a result of monitoring the data that there is an abnormality in the first magnetic sensor or the processing unit for the first magnetic sensor signal,
a second magnetic sensor signal processing unit for processing the second analog signal of the second magnetic sensor to generate a calibrated analog signal based on a calibration history of the second analog signal, and to generate calibrated second digital data based on the calibrated analog signal and calibration data of the second digital data.

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