JP2012093152A - Magnetic gyroscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic gyroscope capable of accurately determining whether or not there is an influence from a surrounding magnetic field other than geomagnetism, and preventing accidental output of an inaccurate rotation angle.SOLUTION: A magnetic gyroscope 1 comprises a triaxial magnetic sensor 2 and a triaxial acceleration sensor 3. The triaxial acceleration sensor 3 determines whether a measuring body is in a low speed state or a non-low speed state. Only when the measuring body has been determined to be in a non-low speed state, the triaxial magnetic sensor 2 determines whether or not there is an influence from a surrounding magnetic field other than geomagnetism, using the measurement data of the triaxial magnetic sensor 2. When the measuring body has been determined to be in a low speed state, and when the triaxial magnetic sensor 2 has confirmed the influence from a magnetic field other than geomagnetism, the magnetic gyroscope does not output the rotation angle of the measuring body.

Description

  The present invention relates to a magnetic gyro provided with a triaxial magnetic sensor and a triaxial acceleration sensor.

  As shown in FIG. 9, a magnetic gyro 91 provided with a three-axis magnetic sensor 93 capable of detecting magnetism in three axial directions orthogonal to each other is conventionally known as an apparatus for detecting the rotational movement of a measured object. (See Patent Document 1 below).

  The magnetic gyro 91 measures the terrestrial magnetism in time series as a magnetic vector (Mx, My, Mz) by using a triaxial magnetic sensor 93 provided on the measurement object 92. When the measured object 92 rotates, the measured value of the magnetic vector (Mx, My, Mz) changes with time. The magnetic gyro 91 calculates and outputs the rotation angle and angular velocity of the measured object 92 from the temporal change of the measured magnetic vector (Mx, My, Mz).

  When the three-axis magnetic sensor 93 can measure only uniform geomagnetism, such as when there is no magnet around the measurement object 92, the magnetic gyro 91 accurately detects the rotational movement of the measurement object 92. Can do. However, as shown in FIG. 9, a magnetic field other than geomagnetism such as a magnet 99 exists around the measured object 92 and is affected by the magnetic field generated by the magnet 99. When the three-axis magnetic sensor 93 is affected by this, the rotational movement of the measured object 92 cannot be accurately detected.

  Therefore, the conventional magnetic gyro 91 does not output the detection result of the rotational motion when the triaxial magnetic sensor 93 is affected by the magnet 99 or the like. As means for determining whether or not the triaxial magnetic sensor 93 is affected by a magnetic field other than geomagnetism (effect determination means), for example, as measured in claims 10 and 11 of Patent Document 2, the measured geomagnetism is used. There is known a method for determining whether or not there is a change in the absolute value of a value greater than a preset threshold value. The contents will be described below.

  First, the magnitude | M | of the measured magnetic vector (Mx, My, Mz) is calculated using the following mathematical formula.

  Although the magnitude of the geomagnetism varies depending on the measurement location, it is normally measured continuously within a range that does not move significantly, so the value can be considered constant, so the triaxial magnetism If the sensor 93 is not affected by the magnet 99 or the like, the direction of the magnetic vector will change even if the measured object 92 (magnetic gyroscope) changes its direction, but the magnitude | M | Can do. On the other hand, when the triaxial magnetic sensor 93 is affected by a magnetic field other than geomagnetism such as the magnet 99, the positional relationship between the measured object 92 and the magnet 99 changes or the direction of the measured object 92 changes with time. , | M | varies with time. Therefore, the difference Δ | M | between the measured values | M1 | and | M2 | at two different time points t1 and t2 is calculated, and when this difference Δ | M | exceeds a predetermined threshold value, It can be determined that the three-axis magnetic sensor 93 is affected by the geomagnetic disturbance. As a result, when the measurement result such as the rotation angle becomes inaccurate due to the influence of the magnetic field other than the geomagnetism, the triaxial magnetic sensor 93 can be prevented from outputting the measurement result.

  On the other hand, the measured object 92 may rotate at a low speed or at a high speed. When rotating at a low speed, the change in the rotation speed of the measured object 92 during the measurement time interval Δt is small, and even if there is a change in the rotation axis, it does not cause a large calculational effect even if ignored. Further, since the rotation angle within the time Δt also becomes small, even if the time interval Δt (= t2−t1) for measuring the magnetic vector is set relatively long, the actual rotational motion state can be accurately grasped with almost no problem. be able to. However, when the measured object 92 rotates at a high speed, if the time interval Δt is set longer, the change in the rotational speed of the measured object 92 and the change in the rotation axis within the time Δt cannot be ignored. At the same time, since the rotation angle within Δt also increases, it is difficult to accurately grasp the rotational motion state of the measured object 92.

  In other words, the magnetic gyroscope targeted by the present invention enables accurate measurement even when the rotational angular velocity exceeds 1000 degrees / second as if the user intentionally swung a portable device such as a mobile phone. It is aimed. In this case, the rotation axis and rotation speed change even during one swing, and the rotation angle cannot be obtained unless the rotation axis is obtained. Therefore, the rotation angle is continuously obtained every minute time of several milliseconds or less. It was necessary to measure the geomagnetic vector.

International Publication WO2007 / 099599 Japanese Patent Laid-Open No. 2003-167039

  However, if the time interval Δt is shortened, when the measured object 92 rotates at a low speed, the above Δ | M | becomes small, which causes a problem that it becomes difficult to set the threshold value.

  That is, even when Δ | M | becomes small due to low-speed rotation, it is necessary to set the threshold value of Δ | M | low so that the presence or absence of the magnet 99 or the like can be confirmed. However, since the triaxial magnetic sensor 93 may have noise inherent in the sensor itself such as an offset error, if the threshold value is set low, Δ | M | tends to exceed the threshold value due to the noise. As a result, it is easy to erroneously determine that the magnetic field is not affected by a magnetic field other than geomagnetism.

  If the threshold value is set high, Δ | M | is difficult to exceed the threshold value during low-speed rotation, so that although it is actually affected by a magnetic field other than geomagnetism, it is mistakenly not affected. Judgment is likely to occur.

  Further, as shown in FIG. 10, the conventional magnetic gyro 91 has a time change in the peripheral magnetic field even when the measured object 92 is not rotating, such as when the magnet 99 approaches the measured object 92. In such a case, since the measurement value detected by the magnetic sensor changes as a matter of course, it may be erroneously determined as if the measurement object 92 is rotating. Here, if the threshold value is low, the influence determining means can determine the influence of the presence of the peripheral magnetic field. However, when the threshold value is set high, Δ | M | does not easily exceed the threshold value, and therefore it is difficult to recognize that the triaxial magnetic sensor 93 is affected by a magnetic field other than geomagnetism. For this reason, there is a problem that it is easy to output an inaccurate rotation angle or the like by erroneously determining that the measured object 92 is not rotated but rotating.

  The present invention has been made in view of such a problem, and can accurately determine whether or not it is affected by a peripheral magnetic field other than geomagnetism, and can prevent erroneous output of an inaccurate rotation angle. It is intended to provide an expression gyro.

The present invention includes a three-axis magnetic sensor that detects geomagnetism as a magnetic vector in a three-axis orthogonal coordinate system fixed to a measurement object;
A triaxial acceleration sensor for detecting gravitational acceleration as an acceleration vector in the triaxial orthogonal coordinate system;
A memory for storing data of the magnetic vector detected in time series by the triaxial magnetic sensor and data of the acceleration vector detected in time series by the triaxial acceleration sensor;
A rotation angle calculating means for calculating a rotation angle of the object to be measured based on at least the magnetic vector data among the magnetic vector data and the acceleration vector data at two or more different points of time stored in the memory; ,
Based on the acceleration vector data stored at two or more different points in time stored in the memory, the measured object is rotating at a rotation speed slower than a predetermined threshold or is not rotating, A rotation determining means for determining whether or not a non-low speed state is rotating at a rotation speed not slower than the threshold value;
When the rotation determining means determines that the object to be measured is in the non-low speed state, the three-axis magnetic sensor is operated based on the magnetic vector data stored in the memory at two or more different points in time. An impact judging means for judging whether or not it is affected by a magnetic field other than geomagnetism,
Output means for outputting the rotation angle when the influence determination means determines that the three-axis magnetic sensor is not affected by a magnetic field other than the geomagnetism,
When the rotation determining means determines that the measured object is in the low speed state, and when the influence determining means determines that the three-axis magnetic sensor is affected by a magnetic field other than the geomagnetism. Is a magnetic gyroscope configured not to output the rotation angle to the output means (claim 1).

  The magnetic gyro includes a triaxial acceleration sensor that detects gravitational acceleration as an acceleration vector. Then, rotation determining means for determining whether the measured object is in the low speed state or the non-low speed state using acceleration vector data measured by the three-axis acceleration sensor is provided. In this way, since the three-axis acceleration sensor is not affected by magnetism, even if a magnet or the like is present around the object to be measured, the object to be measured is in a low speed state or a non-low speed state without being affected by the magnet. Can be determined accurately. For example, even when the surrounding magnetic field changes over time, such as when a magnet approaches a measurement object that is in a low-speed state, the measurement object is accurately in a low-speed state even when it is stationary and not rotating. I can judge. For this reason, it is possible to prevent an incorrect value of the rotation angle from being output erroneously when the object to be measured is rotated even though the object to be measured is stationary without rotating due to the time change of the peripheral magnetic field.

In the magnetic gyro, when the rotation determining means determines that the object to be measured is in a non-low speed state, the triaxial magnetic sensor uses the magnetic vector data to influence the magnetic field other than geomagnetism. An impact judging means for judging whether or not it is received is provided.
In this way, only when the measured object is rotating at a certain speed (non-low speed state), it is determined whether or not it is affected by a magnetic field other than geomagnetism. If the object to be measured is in a non-low speed state and there are magnets around it, the detected value of the magnetic sensor changes due to the magnetic field other than the geomagnetism due to the rotation of the object to be measured. The time variation of | M | _H tends to be large, and conversely, if a magnet or the like is present in the low speed state, the variation in the detected value of the magnetic sensor is smaller than that in the non-low speed state. The time variation of | M | _H tends to be small. In the present invention, the three-axis magnetic sensor affects the influence of a magnetic field other than geomagnetism only when the object to be measured is in a non-low-speed state (when there is a magnet or the like around the time, the time fluctuation of | M | _H tends to increase). In order to determine whether or not | M | _H exceeds a threshold value, the threshold value is compared with the case of determining whether or not there is a magnetic field other than geomagnetism including a low-speed state. Even if it is set to a large value, it is possible to greatly reduce the possibility of erroneously judging that it is not affected even though it is affected by a magnetic field other than geomagnetism. Therefore, even when noise such as an offset error occurs in the three-axis magnetic sensor, it is difficult to cause a problem that | M | _H exceeds the threshold due to the noise. As a result, it is possible to prevent a problem that the measured object is erroneously determined as being received even though it is not affected by a magnetic field other than geomagnetism.

Further, in the present invention, when the object to be measured is in a low speed state (when | M | _H tends to be small even if a magnet or the like is present in the surroundings), the three-axis magnetic sensor is affected by a magnetic field other than geomagnetism. Do not judge whether or not. If, by the judgment in the case the object to be measured is low state, and when set large the threshold value, even if there is a magnet or the like around | M | _{for H} tends to be small, | M | _H is the threshold It becomes difficult to exceed. As a result, it is easy to determine that the measurement object is not erroneously received even though it is affected by a magnetic field other than the geomagnetism. However, in the present invention, when the object to be measured is in a low speed state, such a problem is unlikely to occur because it is not determined whether the three-axis magnetic sensor is affected by a magnetic field other than geomagnetism.

  As described above, according to the present invention, there is provided a magnetic gyro capable of accurately determining whether or not it is affected by a peripheral magnetic field other than geomagnetism and preventing erroneous output of an inaccurate rotation angle. be able to.

1 is a conceptual diagram of a magnetic gyroscope in Embodiment 1. FIG. 1 is a block diagram of a magnetic gyroscope in Embodiment 1. FIG. 2 is a flowchart of a magnetic gyroscope according to the first embodiment. The flowchart following FIG. 1 is a perspective view of a triaxial magnetic sensor in Embodiment 1. FIG. 3 is a graph showing a change in an X component of an acceleration vector in the first embodiment. The graph showing the fluctuation | variation of the acceleration high frequency component extracted from the graph of FIG. 3 is a graph showing a change in an absolute value of an acceleration high frequency component in Example 1. The conceptual diagram of the magnetic-type gyro in a prior art example. In the conventional example, a magnetic gyro when a magnet approaches a stationary object to be measured.

As a matter of course, the low-speed state includes a state where the measurement object is not rotating. Moreover, the said threshold value can be set suitably. For example, by setting the threshold value to 0 m / s ² , an error that is unavoidable in the measurement of the acceleration sensor, that is, a value that is very close to 0 m / s ² , which is the sum of the expected noise magnitude, Only the state in which the measuring body is not substantially rotated can be the low speed state. When such a threshold is adopted, not only the measured rotation angle is not output, but the rotation angle is output as 0 ° regardless of the value of the measured rotation angle, or it is in a stationary state. It is also possible to take means such as displaying on a screen.

In the present invention, the rotation determining means extracts an acceleration high-frequency component having a frequency of fluctuation of the acceleration vector higher than a predetermined value from the acceleration vector data, and an absolute value of the acceleration high-frequency component. When the absolute value is larger than a predetermined value, it is preferable to determine that the measured object is in the non-low speed state (claim 2).
The data of the acceleration vector includes an acceleration low frequency component whose fluctuation frequency is lower than a predetermined value and an acceleration high frequency component whose fluctuation frequency is higher than a predetermined value. Among these, acceleration high frequency components higher than a predetermined value are caused by the rotational motion of the measured object, while acceleration low frequency components lower than the predetermined value are other than rotational motion, for example, gravitational acceleration. This is caused by such reasons. Therefore, with the above configuration, since the acceleration low frequency component whose fluctuation frequency is lower than a predetermined value can be removed from the acceleration vector data, it is possible to more accurately determine whether the measured object is in the low speed state or the non-low speed state. It becomes possible.

The influence determination means calculates an absolute value of the magnetic vector, extracts a magnetic high frequency component having a frequency of fluctuation of the absolute value higher than a predetermined value from the absolute value, and outputs the magnetic high frequency. When the component exceeds a predetermined range, it is preferable to determine that the three-axis magnetic sensor is affected by a magnetic field other than the geomagnetism (Claim 3).
The absolute value of the magnetic vector includes a magnetic low frequency component whose fluctuation frequency is lower than a predetermined value and a magnetic high frequency component whose fluctuation frequency is higher than a predetermined value. Among them, the magnetic high frequency component is generated because the value of each component of the magnetic sensor to which the measured object is fixed changes and the surrounding magnetic field changes with time as the measured object rotates. However, the magnetic low frequency component is generated due to, for example, the absolute value of the original magnetic vector, that is, the absolute value of the geomagnetic vector, other than the temporal change of the peripheral magnetic field. With the above configuration, it is possible to remove magnetic low frequency components whose fluctuation frequency is lower than a predetermined value caused by the presence of the geomagnetic vector from the magnetic vector data, so that it is possible to accurately detect changes in the magnetic field around the measured object. . Therefore, it is possible to accurately calculate the rotation angle of the measured object.

Example 1
A magnetic gyro according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the magnetic gyro 1 of this example includes a three-axis magnetic sensor 2, a three-axis acceleration sensor 3, a memory 4, a rotation angle calculation unit 5, a rotation determination unit 6, and an influence determination unit 7. And an output means 8.
As shown in FIG. 5, the triaxial magnetic sensor 2 detects geomagnetism as a magnetic vector M in the triaxial orthogonal coordinate system 10 fixed to the object to be measured.
The triaxial acceleration sensor 3 detects the acceleration of the measurement object including the gravitational acceleration as the acceleration vector A in the triaxial orthogonal coordinate system 10.

As shown in FIG. 1, the memory 4 stores the magnetic vector M data detected in a time series by the triaxial magnetic sensor 2 and the acceleration vector A data detected in a time series by the triaxial acceleration sensor 3. To do.
As shown in FIG. 3, the rotation angle calculation means 5 is based on at least the data of the magnetic vector M among the data of the magnetic vector M and the data of the acceleration vector A stored in the memory 4 at two or more different time points. A body rotation angle θ is calculated (step S3).
For the method of obtaining the rotation axis and the rotation angle from the detected magnetic vector M data or both the magnetic vector M and acceleration vector A data, the above-mentioned Patent Document 1 and the present inventors have already filed applications. Since it is clarified in Japanese Patent Application Laid-Open No. 2008-224642 and Japanese Patent Application No. 2010-128241, the description is omitted here.
Based on the acceleration vector A data stored at two or more different points in time stored in the memory 4, the rotation determination unit 6 rotates or rotates at a rotation speed slower than a predetermined threshold. It is determined whether there is no low speed state or a non-low speed state rotating at a rotational speed not slower than the threshold value (step S4).

When the rotation determining means 6 determines that the measured object is in the non-low speed state, the influence determining means 7 is a three-axis magnetic field based on the magnetic vector data stored at two or more different points in time stored in the memory. It is determined whether the sensor is affected by a magnetic field other than geomagnetism (step S6).
The output unit 8 outputs the rotation angle θ when the influence determination unit 7 (step S6) determines that the triaxial magnetic sensor 2 is not affected by a magnetic field other than geomagnetism (step S9).
When the rotation determining means 6 (step S4) determines that the object to be measured is in the low speed state, the influence determining means 7 (step S6) causes the triaxial magnetic sensor 2 to be affected by a magnetic field other than geomagnetism. If it is determined that the rotation angle θ is determined, the rotation angle θ is not output to the output means 8.
The details will be described below.

  As shown in FIG. 2, the magnetic gyro 1 of this example includes a computer 100. The computer 100 includes a CPU 11, a ROM 12, a RAM (memory) 4, an I / O 13, and a line 14 that connects them. The ROM 12 stores a program 12p. When the CPU 11 reads and executes the program 12p, the rotation angle calculation means 5, the rotation determination means 6, and the influence determination means 7 of this example are realized. Further, the computer 100 is connected with a triaxial magnetic sensor 2, a triaxial acceleration sensor 3, and output means 8.

  The triaxial magnetic sensor 2 is configured by a magneto-impedance sensor element 20 as shown in FIG. That is, the three-axis magnetic sensor 2 causes the three magneto-impedance sensor elements 20 to be in three-axis directions (X-axis direction, Y-axis direction, and Z-axis direction) in which the respective magnetic sensing directions are orthogonal to each other. It is formed by arranging. Further, the triaxial acceleration sensor 3 is a so-called MEMS acceleration sensor that combines two parts obtained by finely processing silicon in a comb shape and detects a change in the gap between parts caused by application of acceleration as a change in capacitance. They are combined in three axial directions. In FIG. 5, electronic components and wiring other than the magneto-impedance sensor element 20 are omitted.

Next, a flow of a series of processes performed by the magnetic gyro 1 of this example will be described using the flowcharts of FIGS. As shown in FIG. 3, when the magnetic gyro 1 is started, step S1 is first processed. Here, data measured by the triaxial magnetic sensor 2 and the triaxial acceleration sensor 3 are input.
After step S1, the process moves to step S2. In step S2, it is confirmed whether the low speed state is stored in step S5 described later or whether an error is stored in step S7. When starting the magnetic gyro 1 and processing step S2 for the first time, it is judged as No and moves to step S3.

  In step S3, the process in the rotation angle calculation means 5 mentioned above is performed. That is, the rotation angle θ of the measured object is calculated using only the magnetic vector M data, or the rotation angle θ is calculated by combining the magnetic vector M data and the acceleration vector A data.

After step S3, the process moves to step S4. In step S4, the process in the rotation determination means 6 described above is executed. That is, based on the acceleration vector A data stored at two or more different points in time stored in the memory 4, it is determined whether the measured object is in the low speed state or the non-low speed state.
In this example, the method described below is used to determine whether the object to be measured is in a low speed state or a non-low speed state. As shown in FIG. 6, among the components of the acceleration vector (Ax, Ay, Az), for example, the X component (Ax) is an acceleration low frequency component Ax _L (a component that varies slowly) whose fluctuation frequency is lower than a predetermined value. And an acceleration high frequency component Ax _H (a component that fluctuates quickly) whose fluctuation frequency is higher than a predetermined value. That is,
Ax = Ax _H + Ax _L (2)
It is. Similarly, other components (Ay, Az)
Ay = Ay _H + Ay _L
Az = Az _H + Az _L (3)
It is.

In this example, in step S4, data of acceleration vectors (Ax, Ay, Az) at appropriate time points are passed through a digital low-pass filter, and acceleration low frequency components (Ax _L , Ay _L , Az _L ) are extracted. Then, as shown in the following formula, the acceleration high frequency components (Ax _H , Ay _H , Az) are obtained by subtracting the acceleration low frequency components (Ax _L , Ay _L , Az _L ) from the acceleration vector (Ax, Ay, Az). _H ) is extracted. Further, the absolute value | A | _H of the acceleration high frequency components (Ax _H , Ay _H , Az _H ) is calculated using the following equation. The absolute value | A | _H varies with time, for example, as shown in FIG. Calculated absolute value | A | _{if H} is greater than the threshold value K ₁ with a predetermined, it is determined that the object to be measured is a non-slow state.

As shown in FIG. 3, in step S4, the absolute value | A | if _H is less than the threshold value K ₁ is No, i.e. determines that the object to be measured is low state, the procedure proceeds to step S5. In step S5, it memorize | stores that a to-be-measured object is a low speed state, and does not output rotation angle (theta). Further, in step S4, the absolute value | A | if _H is greater than the threshold value K ₁ is Yes, that is, determines that the object to be measured is a non-slow state, moves to step S6.
In this example, by setting a value very close to the threshold K ₁ to 0 m / s ^2, it is only state in which the measurement object is not rotating substantially slow state.
When such a value very close to 0 m / s ² is set as the threshold value, the absolute value | A | _H being smaller than the threshold value means that the measured object is in a stationary state. Therefore, without using the calculated rotation angle θ, the rotation angle can be forcibly replaced with 0, or a display indicating that the camera is in a stationary state can be displayed on the screen.

In step S6, the process in the influence determination means 7 is performed. That is, based on the data of the magnetic vector M stored at two or more different points in time stored in the memory 4, it is determined whether or not the triaxial magnetic sensor 2 is affected by a magnetic field other than geomagnetism.
In this example, the method described below is used to determine whether or not the triaxial magnetic sensor 2 is affected by a magnetic field other than geomagnetism. First, the time change of the magnitude | M | of the magnetic vector (Mx, My, Mz) is calculated by using the following equation using the magnetic vector data stored in the memory by the magnetic sensors at a plurality of points in time.

Here, as shown in the following formula, the time change data of | M | has a magnetic low frequency component | M | _L (a slowly varying component) whose fluctuation frequency is lower than a predetermined value and a fluctuation frequency of a predetermined frequency. It is a value obtained by adding the magnetic high frequency component | M | _H (component that fluctuates quickly) higher than the value.
| M | = | M | _H + | M | _L (7)

In step S6 in this example, from the data of the magnetic vector M plural points stored in the memory | M | calculated by the number 3, through the data to digital low-pass filter, magnetic low frequency components | a _L | M Extract. After that, as shown in the following formula, by subtracting the magnetic low frequency component | M | _L generated mainly due to geomagnetism from | M |, the temporal change of the peripheral magnetic field caused by the rotational motion of the measured object can be reduced. Only the corresponding magnetic high frequency component | M | _H is extracted.
| M | _H = | M | − | M | _L (8)
| M | _H changes with time, but when it is affected by a magnetic field other than geomagnetism, the fluctuation becomes large. Therefore, as a matter of course, in this case, the maximum value of | M | _H is also a larger value.
Therefore, the extracted magnetic high-frequency components | M | _{if H} is greater than the threshold value K ₂ to a predetermined condition occurs instantaneously, 3 the axis magnetic sensor 2 are affected by the magnetic field other than geomagnetism to decide.

As shown in FIG. 3, in step S6, the magnetic high-frequency component | M | if the latest value of _H is greater than the threshold value K ₂ is Yes, that is, three-axis magnetic sensor is affected by a magnetic field other than geomagnetism Judge, and go to step S7. In step S7, it is stored that the geomagnetism cannot be measured normally (error), and the rotation angle θ is not output. After processing step S7, time t1 is stored in step S8.
Further, in step S6, the magnetic high-frequency component | M | if the latest value of _H is smaller than the threshold value K ₂ is determined No, that is, the three-axis magnetic sensor is not affected by the magnetic field other than geomagnetism, step Move to S9.

  In step S9, the rotation angle θ calculated in step S3 is output. Thus, only when it is determined in step S4 that the device to be measured is in a non-low speed state, and in step S6, it is determined that the triaxial magnetic sensor 2 is not affected by a magnetic field other than geomagnetism. Is output.

  As shown in FIG. 3, after performing step S5, S8, or S9, the process returns to step S1. In step S1, after inputting new measurement data, step S2 is processed again. If the low-speed state is stored in step S5 or if an error is stored in step S7, Yes is determined in step S2, and the process proceeds to step S10. If it is not stored as a low speed state or an error, it is determined No in step S2, and the process proceeds to step S3. As described above, unless Step S5 or Step S7 is executed, Steps S1, S2, S3, S4, S6, and S9 are repeatedly executed to continuously output the rotation angle θ.

On the other hand, if Yes is determined in step S2, the process proceeds to step S10 shown in FIG. 4 to determine whether there is an error or a low speed state in step S10. If there is an error, the process proceeds to step S11. Move on to S14. In step S11, it is determined whether or not the triaxial magnetic sensor 2 is not affected by a magnetic field other than geomagnetism. Here, the magnetic high-frequency component | M | if the latest value of _H is smaller than the threshold value K _2/2 is determined Yes, i.e. 3-axis magnetic sensor 2 is no longer affected by the magnetic field other than geomagnetism, Step S12 Move on. In step S12, the processed time t2 is stored, and then the process proceeds to step S13. The magnetic high-frequency component in step S11 | determined that if the latest value of _H is greater than the threshold value K _2/2 is No, that is 3-axis magnetic sensor 2 has received yet the influence of a magnetic field other than geomagnetism | M Then, the process returns to step S1 again.
The threshold _K 2/2 in step S11, is half of the threshold _{K 2} in step S6. This is because if the Same thresholds and K ₂ in step S11, the magnetic high-frequency component | is determined that _H is Yes only dropped slightly, that is, 3-axis magnetic sensor 2 no longer affected by the magnetic field other than geomagnetism | M This is because the reliability is lowered. In the present embodiment, an example in which the threshold value is halved is shown as an example. However, this value is of course not limited to ½, and the reliability can be improved within a range of less than 1 time. Can be adjusted appropriately.

In step S13, the elapsed time from the time t1 to time t2 (t2-t1) is to determine whether a given value _{K 3} above. No in step S13, i.e., if it is determined that the t2-t1 _{<K 3} returns to step S1, and repeats the steps S10, S11, S12, S13. Update the t2 in step S12, in a case filled with t2-t1 ≧ _{K 3} in step S13 (Yes), it determines that the influence of the magnetic field other than geomagnetism is exhausted, the flow proceeds to step S14. This is because | M | _H is a value that fluctuates with time, and it cannot be immediately determined that the influence of a magnetic field other than geomagnetism has disappeared just because the value is instantaneously below the threshold. Accordingly, 3-axis magnetic sensor 2 is a time t1 that is determined to be influenced by the magnetic field other than geomagnetism from the memory in step S8, | M | elapsed time _H until a threshold K _2/2 or less ( If t2-t1) is too short, the full effect has disappeared can not be determined, the predetermined time K ₃ or more on standby, to enhance the reliability.

In step S14, it is determined whether or not the object to be measured is in a non-low speed state. Here, it is determined whether or not the absolute value | A | _H of the acceleration high frequency components (Ax _H , Ay _H , Az _H ) is greater than or equal to the threshold value 2K ₁ . The absolute value | A | If _H is less than the threshold 2K ₁ No, i.e. determines that the object to be measured is low state, the flow returns to step S1. The absolute value | A _| if _H is the threshold value 2K ₁ or Yes, that is, determines that the object to be measured is a non-slow state, moves to step S15. In step S15, the determination of the low speed state stored in step S5 or the error determination stored in step S7 is canceled.
The threshold 2K ₁ at step S14 is twice of _{K 1} in step S4. This is because if the Same threshold as K ₁ at step S14, the absolute value | A | _H is Yes only slightly increased, i.e. cause it is determined that the object to be measured is a non-slow state, the lower the reliability Because. In this embodiment, an example in which the threshold value is doubled is shown as an example, but this value is of course not limited to twice, so that the reliability can be improved in a range exceeding one time. It can be adjusted appropriately.

  As described above, when the predetermined time has elapsed after the triaxial magnetic sensor 2 is not affected by magnetism other than geomagnetism (step S13), and it is determined that the measured object is in a non-low speed state (step S14). In addition, the low speed state or error is canceled (step S15), and the process returns to step S1. As a result, the processing from step S2 to step S9 can be performed, and the rotation angle θ can be output.

  Next, the effect of the present invention will be described with reference to examples including specific numerical values. The magnetic gyro 1 of the present invention is capable of instantaneous rotation even when the object to be measured rotates at a high speed exceeding 1000 degrees / second instantaneously while changing the rotation axis and the rotation angular velocity with time. The purpose is to enable accurate measurement of the situation. Of course, it does not always rotate at high speed, but considering the user's usage situation, it is not known in advance when the object to be measured starts high-speed rotation, so that the rotation status can be measured accurately even during high-speed rotation. Therefore, it is necessary to make the measurement time interval very short regardless of whether the object to be measured is rotating at high speed or not. As an example, the experiment was performed with 1 ms.

  When the measurement time interval is 1 msec, even if there is an influence of the external magnetic field as described above, the detection value of the magnetic sensor is unlikely to change greatly. In order to determine the influence, the threshold needs to be about 5 mG. However, since the magnetic sensor is affected by the magnetized electronic component in the vicinity of the magnetic sensor, offset correction is difficult, but it is difficult to suppress the error to 5 mG or less even after offset, and the threshold is set to 5 mG. If there is no external magnetic field, there is a possibility that the external magnetic field may be erroneously determined.

  On the other hand, if the threshold value is set to a value slightly larger than the maximum expected offset error (for example, 34 mG), there is a problem in that it cannot be recognized despite the influence of the external magnetic field. .

Therefore, the acceleration sensor is further used with the threshold value kept at 34 mG, the fluctuation threshold value is set to 0.2 m / s ^2, and the rotation angle calculated from the magnetic sensor is set at a low speed state where the fluctuation of the acceleration sensor is equal to or less than the threshold value. Is it possible to determine the presence of an external magnetic field by preparing three types of gyros: a configuration that does not output, a gyro when the acceleration sensor is not used, and a gyro with the above-described threshold value of 5 mG, and intentionally approaching the magnet in a stationary state? I tested it. The experiment was performed with the cut-off frequency of the low-pass filter for the detected value of the magnetic vector being 0.2 Hz Putterworth characteristic and the cut-off frequency of the low-pass filter for the detected value of the acceleration vector being 0.5 Hz.

  As a result, the magnetic gyroscope with the magnetic vector fluctuation threshold value of 5 mG is of course judged to have the influence of the external magnetic field when the magnet is brought close, but it is not always possible even when the magnet is not brought close. However, it has been found that a state in which the rotation angle is not output occurs.

  The magnetic gyroscope with a magnetic vector threshold of 34 mG and no acceleration sensor does not cause a state in which the rotation angle is not output when the magnet is not brought close, but when the magnet is intentionally brought close However, it was found that the influence of the external magnetic field could not be determined, and the rotation angle could continue to be output.

  On the other hand, the magnetic field gyroscope using an acceleration sensor with a magnetic field vector fluctuation threshold value of 34 mG continues to output the rotation angle reliably when the magnet is not brought close, and when the magnet is brought closer, the rotation angle is reliably output. It was confirmed that it stopped and operated normally.

  Next, the function and effect of this example will be described. The magnetic gyro 1 of this example includes a triaxial acceleration sensor 3 that detects gravitational acceleration as an acceleration vector A, as shown in FIG. Further, as shown in FIGS. 1 and 3, rotation determination means 6 for determining whether the object to be measured is in a low speed state or a non-low speed state using data of the acceleration vector A measured by the triaxial acceleration sensor 3 (step S4). Is provided. In this way, since the triaxial acceleration sensor 3 is not affected by magnetism, even if a magnet or the like is present around the object to be measured, the object to be measured is in a low speed state or a non-low speed without being affected by the magnet. It is possible to accurately determine whether it is in a state. For example, even when the surrounding magnetic field changes with time, such as when a magnet approaches a measurement object in a low speed state, it can be accurately determined that the measurement object is in a low speed state. Therefore, it is possible to prevent erroneous output when the measured object is rotating due to the temporal change of the peripheral magnetic field.

In addition, the magnetic gyro 1 of this example uses the data of the magnetic vector M when the rotation determining means 6 (step S4) determines that the rotational motion of the measured object is in a non-low speed state. An influence determining means 7 (step S6) is provided for determining whether the axial magnetic sensor 2 is affected by a magnetic field other than geomagnetism.
In this way, only when the measured object is rotating at a certain speed (non-low speed state), it is determined whether or not it is affected by a magnetic field other than geomagnetism. As described above, if there is a magnet or the like around the object to be measured in the non-low speed state, | M | _H tends to increase, and if there is a magnet or the like around in the low speed state, | M | _H becomes small. Prone. In this example, whether or not the three-axis magnetic sensor 2 is affected by the magnetic field only when the object to be measured is in a non-low-speed state (when there is a magnet or the like, | M | _H tends to increase). determination, i.e. | M | _{for H} to determine whether or not more than the threshold value K _2, the low-speed state is also included, as compared to the case of determining the presence or absence of influence of a magnetic field other than geomagnetism, increase the threshold value K ₂ Can be set. Therefore, even if noise occurs in the 3-axis magnetic sensor 2, by the noise | M | _H hardly occurs a defect that exceeds the threshold value K _2. As a result, it is possible to prevent a problem that the measured object is erroneously determined as being received even though it is not affected by a magnetic field other than geomagnetism.

Further, in this example, when the object to be measured is in a low-speed state (when | M | _H tends to be small even if a magnet is present in the surroundings), the triaxial magnetic sensor 2 is affected by a magnetic field other than geomagnetism. Do not judge whether or not. If, by the judgment when the object to be measured is in a low speed state, and if the threshold value K ₂ is set large, even if there is a magnet around | M | _{for H} tends to be small, | M | _H is the threshold less likely to exceed the K _2. As a result, it is easy to determine that the measurement object is not erroneously received even though it is affected by a magnetic field other than the geomagnetism. However, in this example, when the object to be measured is in a low speed state, such a problem is unlikely to occur because the three-axis magnetic sensor 2 does not determine whether or not it is affected by a magnetic field other than geomagnetism.

Further, the rotation determining means 6 (step S4) of the present example uses acceleration high frequency components (Ax _H , Ay _H , Az _H ) from the acceleration vector A data, where the frequency of fluctuation of the acceleration vector A is higher than a predetermined value. ). Then, the absolute value of the acceleration high-frequency component _{(Ax H, Ay H, Az} H) | A | calculates the _H, the absolute value | A _| if _H is greater than the threshold value _{K 1} with a predetermined, measured Judge that the body is in a non-low speed state.
The acceleration vector data includes an acceleration low frequency component (Ax _L , Ay _L , Az _L ) whose fluctuation frequency is lower than a predetermined value and the acceleration high frequency component (Ax _H , Ay _H , Az _H ). included. Among them, the acceleration high frequency component is generated due to the rotational motion of the measured object, while the acceleration low frequency component is generated due to gravity acceleration or the like other than the rotational motion. With the above configuration, since the acceleration low frequency component generated due to the gravitational acceleration can be removed from the acceleration vector A data, the remaining data includes only the acceleration high frequency component generated due to the rotational motion of the measured object. Therefore, it is possible to more accurately determine whether the object to be measured is in the low speed state or the non-low speed state.

Further, the influence determining means 7 (step S6) of this example calculates a time change of the absolute value | M | of the magnetic vector M, and from the time change data of the absolute value | M |, the absolute value | M | A magnetic high frequency component | M | _H having a fluctuation frequency higher than a predetermined value is extracted. The magnetic nobility frequency components | determined that _{if H} is greater than the threshold value K ₂ to a predetermined state is instantaneously generated, three-axis magnetic sensor 2 are affected by the magnetic field other than geomagnetism | M To do.
The absolute value | M | of the magnetic vector M includes a magnetic low-frequency component | M | _L whose fluctuation frequency is lower than a predetermined value and the magnetic high-frequency component | M | _H. Among them, the magnetic high frequency component | M | _H is generated due to the time-dependent change of the peripheral magnetic field with the rotational movement of the measured object, while the magnetic low frequency component | M | _L is Other than the time change of the surrounding magnetic field, that is, the absolute value of the geomagnetic vector occurs. With the above configuration, since the magnetic low frequency component | M | _L generated by the presence of the geomagnetic vector can be removed from the magnetic vector M data, the remaining data is only the magnetic high frequency component generated by the change in the peripheral magnetic field. Therefore, it is possible to accurately detect a change in the magnetic field around the object to be measured. Therefore, it is possible to accurately determine whether there is no influence of a magnetic field other than geomagnetism and whether the rotation angle of the measured object can be accurately calculated.

Further, as shown in FIG. 5, the triaxial magnetic sensor 2 of the present example includes a magneto-impedance sensor element 20 disposed in three axial directions (X-axis direction, Y-axis direction, Z-axis direction) orthogonal to each other. It is configured.
The magneto-impedance sensor element 20 is a magnetic sensor having a high sensitivity, so that it is easy to detect geomagnetism, but an object approaching the measurement object in a low-speed state has a slight magnetism. However, it detects a change in the magnetic field. Therefore, if the present invention is not applied, the measured object actually rotates even when an object that is slightly magnetized approaches the measured object in a low-speed state that is close to a stationary state. There is a possibility that it is erroneously determined that the rotation is larger than the speed at which the rotation is performed, and it is easy to output an inaccurate rotation angle.
However, in this example, when it is determined that the measured object is in a low speed state using the acceleration vector data, the rotation angle calculated from the magnetic vector data measured by the magnetic sensor is not output. Is hard to get up. For this reason, this example makes full use of the advantages of the high-sensitivity magneto-impedance sensor element 20 while preventing the above-mentioned problems that are likely to occur when the three-axis magnetic sensor 2 comprising the magneto-impedance sensor element 20 is used. be able to.

  As described above, according to this example, it is possible to accurately determine whether or not it is affected by a surrounding magnetic field other than geomagnetism, and to provide a magnetic gyro capable of preventing erroneous output of an inaccurate rotation angle. be able to.

DESCRIPTION OF SYMBOLS 1 Magnetic gyro 2 3-axis magnetic sensor 3 3-axis acceleration sensor 4 Memory 5 Rotation angle calculation means 6 Rotation judgment means 7 Influence judgment means 8 Output means

Claims (3)

A three-axis magnetic sensor for detecting geomagnetism as a magnetic vector in a three-axis orthogonal coordinate system fixed to the measurement object;
A triaxial acceleration sensor for detecting gravitational acceleration as an acceleration vector in the triaxial orthogonal coordinate system;
A memory for storing data of the magnetic vector detected in time series by the triaxial magnetic sensor and data of the acceleration vector detected in time series by the triaxial acceleration sensor;
A rotation angle calculating means for calculating a rotation angle of the object to be measured based on at least the magnetic vector data among the magnetic vector data and the acceleration vector data at two or more different points of time stored in the memory; ,
Based on the acceleration vector data stored at two or more different points in time stored in the memory, the measured object is rotating at a rotation speed slower than a predetermined threshold or is not rotating, A rotation determining means for determining whether or not a non-low speed state is rotating at a rotation speed not slower than the threshold value;
When the rotation determining means determines that the object to be measured is in the non-low speed state, the three-axis magnetic sensor is operated based on the magnetic vector data stored in the memory at two or more different points in time. An impact judging means for judging whether or not it is affected by a magnetic field other than geomagnetism,
Output means for outputting the rotation angle when the influence determination means determines that the three-axis magnetic sensor is not affected by a magnetic field other than the geomagnetism,
When the rotation determining means determines that the measured object is in the low speed state, and when the influence determining means determines that the three-axis magnetic sensor is affected by a magnetic field other than the geomagnetism. The magnetic gyro is configured not to output the rotation angle to the output means.   In Claim 1, the said rotation judgment means extracts the acceleration high frequency component from which the frequency of the fluctuation | variation of this acceleration vector is higher than a predetermined value from the data of the said acceleration vector, and uses the absolute value of this acceleration high frequency component. A magnetic gyro comprising: calculating and determining that the measured object is in the non-low speed state when the absolute value is greater than a predetermined value.   3. The influence determination means according to claim 1, wherein the influence determination means calculates an absolute value of the magnetic vector, and extracts a magnetic high frequency component having a frequency of fluctuation of the absolute value higher than a predetermined value from the absolute value. In addition, when the magnetic high frequency component exceeds a predetermined range, it is determined that the three-axis magnetic sensor is affected by a magnetic field other than the geomagnetism.

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