JP5445270B2 - Calibration data acquisition method, acceleration sensor output correction method, and calibration data acquisition system - Google Patents

Description

  The present invention relates to a calibration data acquisition method, an acceleration sensor output correction method, and a calibration data acquisition system.

  In various fields such as so-called seamless positioning, motion sensing, and attitude control, the use of inertial sensors is attracting attention. As an inertial sensor, an acceleration sensor, a gyro sensor, a pressure sensor, a geomagnetic sensor, and the like are widely known.

  In recent years, sensor modules equipped with multi-axis inertial sensors have been developed. This multi-axis sensor module is configured such that an inertial sensor is mounted on a plurality of orthogonal axes, and sensing in a three-dimensional space can be performed. However, due to the fact that the mounting posture of the inertial sensor with respect to the sensor module is not accurate, there has been a problem that the output of the inertial sensor can include a misalignment error due to a mounting error or other axis sensitivity error.

  In view of such a problem, for example, Japanese Patent Application Laid-Open No. H10-228707 considers an attachment error of the acceleration sensor to the sensor module, calculates the other axis sensitivity of the gravitational acceleration detected by the acceleration sensor, and corrects the output value of the acceleration sensor. Is disclosed.

JP-A-10-267651

  Certainly, according to the technique of Patent Document 1, the misalignment error may be corrected. However, other components can be included in the output of the inertial sensor. Typically, it is a component such as a zero point bias or a scale factor. The zero point bias means an error value that is constantly added, and the scale factor means the sensitivity of the sensor, that is, the ratio of the change in the output value to the change in the input value to be measured.

  The problem is that these components are temperature dependent. Since these components have temperature dependency, the output of the inertial sensor also has temperature dependency. For this reason, it is not sufficient to consider misalignment errors, and the output of the inertial sensor cannot be corrected correctly unless the temperature characteristics of the inertial sensor are also taken into consideration.

  The present invention has been made in view of the above-described problems, and its object is to propose a new method for appropriately determining the temperature characteristics of an inertial sensor while taking into account misalignment errors. is there.

  The first form for solving the above-described problem is that the direction of each detection axis of the acceleration sensor is an absolute axis direction, the posture of the acceleration sensor is changed so as to detect the acceleration in each absolute axis direction, Performing a data acquisition process of recording an output value of each detection axis of the acceleration sensor by changing an operating environment temperature, and calculating a temperature-dependent characteristic of the acceleration sensor based on the output value. This is a calibration data acquisition method.

  As another form, the direction of each detection axis of the acceleration sensor is set to the absolute axis direction, the attitude of the acceleration sensor is changed so as to detect the acceleration in each absolute axis direction, and the operating environment temperature is changed. A calibration data acquisition system comprising: a data acquisition processing unit that records output values of the respective detection axes of the acceleration sensor; and a temperature dependent characteristic calculation unit that calculates temperature dependent characteristics of the acceleration sensor based on the output values May be configured.

  According to the first embodiment, the direction of each detection axis of the acceleration sensor is set as the absolute axis direction, the posture of the acceleration sensor is changed so as to detect the acceleration in each absolute axis direction, and the operating environment temperature is By changing, the output value of each detection axis of the acceleration sensor is recorded. Then, the temperature dependence characteristic of the acceleration sensor is calculated based on the output value.

  An acceleration sensor is a kind of inertial sensor. Under an environment in which the absolute axis direction is determined, the direction of each detection axis of the acceleration sensor is set as the absolute axis direction, and the posture of each acceleration sensor is changed so that the acceleration of each absolute axis direction is detected. By measuring and recording the output value, the misalignment error can be separated from the detected value of the acceleration sensor (that is, the detected value of acceleration). The output value is measured and recorded while changing the operating environment temperature of the acceleration sensor. Thereby, the temperature characteristic of an acceleration sensor can also be calculated | required appropriately.

  Further, as a second form, the calibration data obtaining method according to the first form, further comprising calculating a misalignment error of the acceleration sensor using the output value and the temperature-dependent characteristic. A data acquisition method may be configured.

  According to the second embodiment, the misalignment error of the acceleration sensor is calculated using the output value of each detection axis of the acceleration sensor and the calculated temperature dependence characteristic of the acceleration sensor.

  From the output value of each detection axis of the acceleration sensor at a predetermined operating environment temperature and the temperature-dependent characteristics of the acceleration sensor, the acceleration with the temperature-dependent component separated can be calculated. Although the acceleration from which the temperature-dependent component is separated may include a misalignment error, the misalignment error can be appropriately obtained by using the acceleration at a plurality of operating environment temperatures.

  Further, as a third mode, in the calibration data acquisition method according to the first or second mode, the calculation of the temperature-dependent characteristic includes the output value in each case where the posture and the operating environment temperature are changed. May be used to configure a calibration data acquisition method including calculating the temperature dependence characteristics of the zero point bias and the scale factor included in the detection result value of the acceleration sensor.

  According to the third aspect, the temperature dependence of the zero point bias and the scale factor included in the value of the detection result of the acceleration sensor using the output value of the acceleration sensor in each case where the posture and the operating environment temperature are changed. Characteristics can be calculated.

  Further, as a fourth mode, in the calibration data acquisition method according to the third mode, the calculation of the temperature-dependent characteristic further includes the temperature dependence of the secondary sensitivity included in the value of the detection result of the acceleration sensor. You may comprise the calibration data acquisition method including calculating a characteristic.

  According to the fourth embodiment, not only the temperature dependence characteristics of the zero point bias and the scale factor, but also the temperature dependence characteristics of the secondary sensitivity included in the value of the detection result of the acceleration sensor can be calculated.

  Further, as a fifth mode, an acceleration for correcting the output value of the acceleration sensor using the temperature dependence characteristic acquired by the calibration data acquisition method of any one of the first to fourth modes and the operating environment temperature. A sensor output correction method may be configured.

  Further, as a sixth embodiment, an acceleration that corrects the output value of the acceleration sensor using the temperature-dependent characteristics acquired by the calibration data acquisition method of the second embodiment, the operating environment temperature, and the misalignment error. A sensor output correction method may be configured.

  According to the fifth or sixth embodiment, the output value of the acceleration sensor can be correctly corrected using the calibration data acquired by the calibration data acquisition method of the above-described embodiment.

The figure which shows an example of a function structure of a test system. The figure which shows an example of a function structure of a test apparatus. The figure which shows an example of a function structure of a sensor module. The figure which shows an example of a data structure of a test database. The figure which shows an example of the table structure of a temperature coefficient table. The flowchart which shows the flow of a characteristic determination process. The flowchart which shows the flow of a test process. The flowchart which shows the flow of a temperature coefficient calculation process. The flowchart which shows the flow of a misalignment coefficient calculation process. The flowchart which shows the flow of a correction | amendment output process.

  An embodiment in which the present invention is applied to a test system as a calibration data acquisition system that acquires a calibration data of an acceleration sensor by testing a sensor module including the acceleration sensor will be described below with reference to the drawings. However, it goes without saying that embodiments to which the present invention can be applied are not limited to the embodiments described below.

1. Functional configuration 1-1. Functional Configuration of Test System FIG. 1 is a block diagram illustrating an example of a functional configuration of the test system 1 in the present embodiment. The test system 1 is a type of calibration data acquisition system that performs a test (test) of the sensor module 5 (see FIG. 3), which is a type of module on which the acceleration sensor 520 is mounted, and acquires calibration data of the sensor module 5. For example, the correction coefficient calculation device 2 and the test device 3 are provided.

(1) Functional Configuration of Correction Coefficient Calculation Device 2 The correction coefficient calculation device 2 is a device that calculates a correction coefficient for correcting the output value of the acceleration sensor 520 mounted on the sensor module 5. As shown in FIG. 1, the correction coefficient calculation device 2 includes a processing unit 10, an input unit 20, a display unit 30, a communication unit 40, and a storage unit 50, and each unit is connected via a bus 60. Connected computer system.

  The processing unit 10 is a control device that comprehensively controls each unit of the correction coefficient calculation device 2 and the test device 3 in accordance with various programs such as a system program stored in the storage unit 50, and includes a CPU (Central Processing Unit) and the like. It is configured with a processor.

  As main processing blocks, the processing unit 10 includes a test execution control unit 11 that performs test processing according to the test program 511, a temperature coefficient calculation unit 13 that performs temperature coefficient calculation processing according to the temperature coefficient calculation program 513, and a misalignment coefficient calculation program. A misalignment coefficient calculation unit 15 that performs a misalignment coefficient calculation process according to 515. The correction coefficient table creating unit 17 creates a correction coefficient table 55 that is a table storing correction coefficients using the temperature coefficient and the misalignment coefficient calculated by the temperature coefficient calculating unit 13 and the misalignment coefficient calculating unit 15. Have

  The input unit 20 is an input device configured by, for example, a keyboard, a button switch, or the like, and outputs a pressed key or button signal to the processing unit 10. By operating the input unit 20, various data are input and various instructions such as a test start request for the sensor module 5 are input.

  The display unit 30 is configured by an LCD (Liquid Crystal Display) or the like, and is a display device that performs various displays based on display signals input from the processing unit 10. Information such as a correction coefficient of the sensor module 5 calculated by the processing unit 10 is displayed on the display unit 30.

  The communication unit 40 is a communication device for the correction coefficient calculation device 2 to perform wired communication or wireless communication with an external device. This function is realized by, for example, a wired communication module that performs communication via a wired cable, a wireless communication module that performs wireless LAN, spread spectrum communication, or the like.

  The storage unit 50 is configured by a storage device (memory) such as a ROM (Read Only Memory), a flash ROM, or a RAM (Random Access Memory), and realizes various functions such as a system program of the correction coefficient calculation device 2 and a test function. It stores various programs, various data, etc. In addition, it has a work area for temporarily storing data being processed and results of various processes.

  The storage unit 50 stores a characteristic determination program 51 that is read by the processing unit 10 and executed as a characteristic determination process (see FIG. 6) as a program. The characteristic determination program 51 includes a test program 511 executed as a test process (see FIG. 7), a temperature coefficient calculation program 513 executed as a temperature coefficient calculation process (see FIG. 8), and a misalignment coefficient calculation process. A misalignment coefficient calculation program 515 executed as (see FIG. 9) is included as a subroutine.

  The characteristic determination process is a process for determining the characteristic of the sensor module 5. That is, the processing unit 10 fixes the sensor module 5 to the test apparatus 3 in various postures, and changes the temperature of the test apparatus 3 to record the output value of each detection axis of the acceleration sensor 520 as data acquisition processing. Perform the test process. And the process which calculates the correction coefficient of the acceleration sensor 520 using the test data acquired by the test apparatus 3 is performed.

  In this embodiment, two types of coefficients, which are temperature dependency and include a temperature coefficient of a component included in the output of the inertial sensor and a misalignment coefficient, are defined as correction coefficients. Components that have temperature dependence and are included in the output of the inertial sensor include parameters that do not depend on misalignment, such as zero point bias, scale factor, and secondary sensitivity.

  The zero point bias means an error value that is constantly added to the output value of the acceleration sensor 520. The scale factor means the sensitivity of the sensor, that is, the ratio of the change in output value to the change in input value to be measured. The secondary sensitivity means the ratio of the change in the output value to the change in the square value of the input value to be measured.

  The misalignment coefficient is a coefficient representing the sensitivity of each detection axis determined as the detection axis of the acceleration sensor 520 to the other detection axis. In the present embodiment, the detection axes of the acceleration sensor 520 are assumed to be three axes (orthogonal three axes) of the x axis, the y axis, and the z axis orthogonal to each other, and the acceleration sensor 520 detects the acceleration of each detection axis.

In this case, as a misalignment coefficient, a coefficient “m _xy ” that represents the sensitivity of the x axis to the y axis, a coefficient “m _xz ” that represents the sensitivity of the x axis to the z axis, and a coefficient that represents the sensitivity of the y axis to the x axis. “M _yx ”, a coefficient “m _yz ” that represents the sensitivity of the y axis to the z axis, a coefficient “m _zx ” that represents the sensitivity of the z axis to the x axis, and a coefficient “m” that represents the sensitivity of the z axis to the y axis _zy "is defined. Further, “m _xx = m _yy = m _zz = 1” is defined as a coefficient representing the sensitivity of each detection axis with respect to its own axis.

但し、「ｗ」はホワイトノイズである。このホワイトノイズは無視できるほど小さな値であるため、本実施形態では考慮しないこととする。 Here, the output model of the acceleration sensor 520 is formulated. The output value “p” of the acceleration sensor 520 is modeled by the following equation (1) including the zero point bias “b”, the scale factor “s”, the secondary sensitivity “q”, and the misalignment error.

However, “w” is white noise. Since the white noise is a value that can be ignored, it is not considered in the present embodiment.

  The zero point bias “b”, the scale factor “s”, and the secondary sensitivity “q” are components that depend on the temperature “t”, and the values change depending on the temperature “t”. Therefore, in the present embodiment, these components are referred to as “temperature-dependent components”.

  In order to clarify that the component depends on temperature, the subscript “t” is attached to the zero point bias “b”, the scale factor “s”, and the secondary sensitivity “q”, respectively. . In addition, since the temperature-dependent component is included in the right side of Expression (1), the output value “p” on the left side also depends on the temperature. Therefore, the subscript “t” is also attached to the output value “p”.

Each temperature dependent component is a polynomial of temperature “t” and is approximated by the following equations (2) to (4).

“B ₀ , b ₁ , b ₂ ,...” In equation (2) indicates a temperature coefficient corresponding to the order of the temperature of the zero point bias. Similarly, “s ₀ , s ₁ , s ₂ ,...” In Expression (3) indicates a temperature coefficient corresponding to the order of the temperature of the scale factor, and “q ₀ , q ₁ in Expression (4)”. , Q ₂ ,... Indicate the temperature coefficient corresponding to the temperature order of the secondary sensitivity.

In Expression (1), “r” is the acceleration value of each detection axis of the acceleration sensor 520 including a misalignment error (this acceleration “r” is defined as “acceleration including a misalignment error”). And is formulated by the following equation (5).

In Expression (5), “r _x , r _y , r _z ” indicates the x-axis, y-axis, and z-axis accelerations including misalignment errors, respectively. On the other hand, “a _x , a _y , a _z ” indicate x-axis, y-axis, and z-axis accelerations that do not include misalignment errors, respectively. The fact that no misalignment error is included means that the acceleration does not include the attachment error of the acceleration sensor 520 and the other-axis sensitivity error, and can be said to be “true value of acceleration”. “M” is a misalignment coefficient matrix having a misalignment coefficient as a component, and “G _a ” is an acceleration matrix having a true value of the acceleration of each detection axis as a component.

  Although the principle will be described in detail later, in this embodiment, the test of the sensor module 5 is performed using the test apparatus 3, and the correction coefficient is calculated according to the above model formula using the test data. Then, the correction coefficient table 55 storing the calculated correction coefficient is created, and the true value of the acceleration is calculated using the correction coefficient table 55, whereby the output value of the acceleration sensor 520 is corrected. Is the purpose.

  Returning to the description of the functional blocks in FIG. 1, the storage unit 50 stores a test database 53 and a correction coefficient table 55 as data.

  FIG. 4 is a diagram illustrating an example of the data configuration of the test database 53. The test database 53 is a database in which a plurality of test data 54 (54-1, 54-2, 54-3,...) Are accumulated and stored. The test data 54 is data in which the output value of each detection axis of the acceleration sensor 520 is recorded while changing the posture of the acceleration sensor 520 and the operating environment temperature using the test apparatus 3.

  Each test data 54 stores a test temperature 541 indicating the temperature at which the test was performed and output value data 543 of the acceleration sensor 520 acquired at the test temperature 541 in association with each other. The output value data 543 stores output value data of each detection axis for each test posture, with the posture in which the acceleration sensor 520 is fixed to the test apparatus 3 as a test posture.

  The temperature coefficient table 553 is a table in which the temperature coefficient of each temperature dependent component is stored, and an example of the table configuration is shown in FIG. In the temperature coefficient table 553, each detection axis 5531 of the acceleration sensor 520 and the temperature coefficient 5533 of each temperature-dependent component calculated for the detection axis 5531 are stored in association with each other.

  The misalignment coefficient table 555 is a table in which misalignment coefficients are stored. For example, the misalignment coefficient matrix “M” in Expression (5) is stored.

(2) Functional Configuration of Test Device 3 FIG. 2 is a block diagram illustrating an example of a functional configuration of the test device 3.
The test apparatus 3 includes a subject fixing device 340 having a mounting table in which at least a vertical direction is accurately positioned (an absolute axis is determined) as an absolute plane, a temperature adjusting unit 350 having a heater device and a cooling device, a temperature The sensor 360 is installed in the thermostat 320. Further, the test apparatus 3 includes a test control apparatus 310, and the test control apparatus 310 can test the subject at an arbitrary test environment temperature by controlling the temperature adjustment unit 350.

  The sensor module 5 is fixed in a posture where the vertical downward direction (absolute axis positive direction) defined on the mounting table of the subject fixing device 340 is the direction of any detection axis of the acceleration sensor 520. Specifically, the posture with the x-axis positive direction as the absolute axis positive direction (x-axis positive), the posture with the x-axis negative direction as the absolute axis positive direction (x-axis negative), and the y-axis positive direction as the absolute axis positive direction (Y axis positive), y axis negative direction as absolute axis positive direction (y axis negative), z axis positive direction as absolute axis positive direction (z axis positive), z axis negative direction as In order to perform a test of a total of six postures in the absolute axis positive direction (z-axis negative), the sensor module 5 is fixed in a posture corresponding to each of these six postures.

  The subject fixing device 340 may be a device that can automatically displace the sensor module 5 to one of the six postures described above and then automatically displace it to any of the remaining postures. (For example, the sensor module 5 is fixed to one side of a regular cube-shaped fixture that can be installed with an arbitrary surface facing downward in the center of the mounting table, and the fixing tool is mounted on the mounting table. It is good also as an apparatus provided with mechanisms, such as changing an attachment direction.

  The temperature sensor 360 is a contact-type or non-contact-type sensor that detects the temperature inside the thermostatic chamber 320, and is configured to output the detected temperature to the test control device 310.

  The test control device 310 is a control device that controls each unit of the test device 3 in accordance with an instruction signal from the processing unit 10, and includes a processor such as a CPU or a DSP (Digital Signal Processor). The test control device 310 controls the temperature adjustment unit 350 so that the temperature inside the thermostat 320 is set to a temperature instructed by the processing unit 10. The test control device 310 is connected to the sensor module 5 and is configured to measure and record the output value of the acceleration sensor 520 under test.

  As a test procedure, the sensor module 5 is fixed to the subject fixing device 340 in a certain posture, the thermostat 320 is sealed, and then the temperature is changed. Then, the acceleration sensor 520 is tested when the temperature reaches a predetermined constant temperature. During the test, the output value of the acceleration sensor 520 is recorded. This is done for all temperatures and all postures.

1-2. Functional Configuration of Sensor Module FIG. 3 is a block diagram illustrating an example of a functional configuration of the sensor module 5. The sensor module 5 is a module including a processing unit 510, an acceleration sensor 520, a temperature sensor 530, an output unit 540, and a storage unit 550.

  The processing unit 510 is a control device that comprehensively controls each unit of the sensor module 5 according to various programs such as a system program stored in the storage unit 550, and includes a processor such as a CPU or DSP. .

  The acceleration sensor 520 is a kind of inertial sensor designed to be able to detect the acceleration of three orthogonal axes (x-axis, y-axis, and z-axis), and outputs the detection result to the processing unit 510. The acceleration sensor 520 is attached to the sensor module 5 so that the axis of the detection direction is a predetermined direction with respect to the sensor module 5. One of the purposes of the test of the present embodiment is to determine the error of the mounting angle (posture).

  The temperature sensor 530 is a contact-type or non-contact-type sensor that detects the ambient air temperature, and outputs the detected temperature to the processing unit 510.

  The output unit 540 is an interface (I / F) unit that externally outputs a corrected output value obtained by the processing unit 510 correcting the output value of the acceleration sensor 520. However, during the test, the output value of the acceleration sensor 520 is output as it is without correction, for example, by setting all the correction coefficients to zero.

  The storage unit 550 is configured by a storage device (memory) such as a ROM, a flash ROM, or a RAM, and stores a program for correcting and outputting the output value of the acceleration sensor 520.

  In the present embodiment, the storage unit 550 stores a correction output program 551 that is read as a program by the processing unit 510 and executed as a correction output process (see FIG. 10). Further, a correction coefficient table 55 including a temperature coefficient table 553 and a misalignment coefficient table 555 created by the correction coefficient calculation device 2 is stored as data.

2. Principle 2-1. Principle of Calculation of Correction Coefficient (1) Calculation of Temperature Coefficient of Temperature Dependent Component The output value “ _pt ” of each detection axis of the acceleration sensor 520 at the test temperature “t” is expressed by the following formula (6) according to the formula (1). It becomes.

In order to make the explanation easy to understand, for example, consider the “x-axis”. In a state where the test temperature is “t”, the output value of the acceleration sensor 520 in an attitude (x axis positive) in which the x axis positive direction is the absolute axis positive direction (vertically downward in this embodiment) is “p _x1t ”. The output value in the posture with the x axis negative direction as the absolute axis positive direction (x axis negative) is “p _x2t ”, the average output value is “p _x3t ”, and “(p _x1t , p _x2t , p _x3t )” ". If the gravitational acceleration in the positive direction of the absolute axis (vertical gravitational acceleration) is “g”, the gravitational acceleration in the negative direction of the absolute axis is “−g”, and the average value thereof is “0”.

但し、（ｒ_x1t，ｒ_x2t，ｒ_x3t）＝（ｇ，−ｇ，０）である。ｘ軸正方向を絶対軸正方向とする姿勢や、ｘ軸負方向を絶対軸正方向とする姿勢で加速度センサー５２０の出力値を取得することにより、ミスアライメント誤差を含まない出力値を取得することができる。 At this time, simultaneous equations such as the following equation (7) can be established according to equation (1).

However, (r _x1t , r _x2t , r _x3t ) = (g, −g, 0). By acquiring the output value of the acceleration sensor 520 in an attitude in which the x-axis positive direction is the absolute axis positive direction and an attitude in which the x-axis negative direction is the absolute axis positive direction, an output value that does not include misalignment errors is acquired. be able to.

From the simultaneous equations of Equation (7), the values “b _xt , s _xt , q _xt ” of the temperature dependent components at the test temperature “t” can be obtained as in the following Equation (8).

Here, three patterns of output values and gravitational acceleration samples of “(p _x1t , p _x2t , p _x3t )” and “(r _x1t , r _x2t , r _x3t ) = (g, −g, 0)” are shown _here. Although it has been described that the value of the temperature-dependent component is calculated using data, it is also possible to perform calculation by increasing the number of patterns of sample data.

For example, the mounting table is rotated at a predetermined rotation speed “n” so that the acceleration sensor 520 is rotated around the x axis while the y axis and the z axis are fixed. Then, the output value “p _x4t ” of the acceleration sensor 520 in that case is measured and added to the sample data of the output value. In this case, the gravity acceleration sample data is “g · sin θ”. However, “θ” is a rotation angle, and is an integrated value of the angular velocity “ω = 2πn” obtained from the rotation speed “n” of the mounting table.

  By rotating the mounting table, a plurality of types of output values and gravity acceleration sample data can be acquired. In this case, since Equation (7) is an overdetermined equation, the value of the temperature-dependent component can be obtained with high accuracy by using, for example, the least square method.

Obtaining values of N temperature-dependent components with different test temperatures for each temperature-dependent component by performing tests at N test temperatures “t = t1, t2, t3,..., TN”. Can do. In other words, N number of zero-point bias _{"b xt1, b xt2, b xt3} , ···, b xtN " and, N number of scale factor _{"s xt1, s xt2, s xt3} , ···, s xtN " and , N secondary sensitivities “q _xt1 , q _xt2 , q _xt3 ,..., Q _xtN ” can be acquired.

Here, for ease of explanation, for example, attention is paid to the zero point bias “b”. In this case, each test temperature “t = t1, t2, t3,..., _TN ” and zero point bias values “b _xt1 , b _xt2 , b _xt3,. In use, N simultaneous equations can be established according to equation (2).

If “N” is sufficiently large, Equation (2) becomes an overdetermined equation, and can be solved using, for example, the least square method. Therefore, the temperature coefficient “b _x0 , b _x1 , b _x2 ,...” Of the zero point bias can be obtained approximately. However, regarding the subscript, the first subscript indicates the detection axis, and the second subscript indicates the temperature order.

Similarly, for the scale factor “s” and the secondary sensitivity “q”, N simultaneous equations are formed according to the equations (3) and (4), respectively. Then, for example, by using the least square method, the temperature coefficients of the scale factors “s _x0 , s _x1 , s _x2 ,...” And the temperature coefficients of the secondary sensitivity “q _x0 , q _x1 , q _x2 ,. "" Can be obtained approximately.

  Although the method for calculating the temperature coefficient of each temperature-dependent component has been described focusing on the x-axis for easy understanding, the temperature coefficient of each temperature-dependent component can also be calculated for the y-axis and the z-axis by the same procedure. .

(2) Calculation of misalignment coefficient First, a test temperature is fixed to a certain test temperature “t”. In this case, using the temperature coefficient of each temperature-dependent component at the test temperature “t”, the value “(b _t , s) of each temperature-dependent component at the test temperature“ t ”according to the following equations (9) to (11). _t, it is possible to calculate the q _t) ".

  Next, an acceleration “r” including a misalignment error is calculated. In order to simplify the explanation, attention is paid to the case where the x-axis coincides with the absolute axis. When the acceleration sensor 520 is fixed in a posture (x-axis positive) in which the x-axis positive direction is the absolute axis positive direction, and in a posture (x-axis negative) in which the x-axis negative direction is the absolute axis positive direction , The output value of the acceleration sensor 520 is measured.

  Further, for each case (x-axis positive, x-axis negative) fixed, the installation direction of the acceleration sensor 520 relative to the mounting table is changed so that the direction of the acceleration sensor 520 is the respective direction of east, west, south, and north Calculate the average of the output values measured in the installation direction. The reason for taking the average of the output values measured by changing the installation direction is to eliminate the error of the output value caused by the inclination of the mounting table.

When the average value of the output values measured under such conditions is calculated, the average value is “p _xt ”, and the value “(b _xt , s _xt , q _xt ) ”is used to calculate the x-axis acceleration“ r _x ”including misalignment error according to equation (1).

In addition, although it demonstrated paying attention to the case where the x-axis coincides with the absolute axis, the same applies to the case where the y-axis and the z-axis coincide with the absolute axis while changing the orientation and installation direction of the acceleration sensor 520. The output value is measured, and the y-axis and z-axis accelerations “r _y ” and “r _z ” including the misalignment error are back-calculated by the above procedure.

On the other hand, the acceleration “r” including the misalignment error can be expressed as follows using the gravitational acceleration “g”. That is, in the case where the acceleration sensor 520 is fixed in a posture in which the positive x-axis direction is the positive positive axis (positive x-axis), the acceleration “(r _xt , r _yt , r _zt )” including the misalignment error is absolute. It can be expressed as “(r _xt , r _yt , r _zt ) = (g, _myx g, m _zx g)” using the gravitational acceleration in the positive axis direction (vertical gravitational acceleration) “g”.

On the other hand, the acceleration “(r _xt , r _yt , r _zt )” including misalignment error in the case where the acceleration sensor 520 is fixed in an attitude (x axis negative) with the x axis negative direction as the absolute axis positive direction is Using absolute gravity negative direction gravity acceleration (vertical upward gravity acceleration) “−g”, “(r _xt , r _yt , r _zt ) = (− g, −m _yx g, −m _zx g)” Can be represented.

Similarly, when the acceleration sensor 520 is fixed so that the y-axis and the z-axis coincide with the absolute axis, the angular velocity “including misalignment error” is determined using positive and negative gravitational accelerations “g” and “−g”. (R _xt , r _yt , r _zt ) ”can be expressed.

In this case, when the simultaneous equations are established according to the equation (5), the following equation (12) is derived.

Finally, using the gravitational acceleration “g” and the acceleration “r” including the misalignment error, the misalignment coefficient matrix “M” can be approximately obtained as in the following equation (13).

2-2. Correction of Output Value of Acceleration Sensor 520 Next, the principle of correction of the output value of the acceleration sensor 520 will be described. In the sensor module 5, the temperature coefficient of each temperature dependent component corresponding to the detected temperature “td” of the temperature sensor 530 is read with reference to the temperature coefficient table 553 stored in the storage unit 50. Then, the values “(b _td , _{st dd} , q _td )” of the temperature dependent components at the detected temperature “td” are calculated according to the equations (9) to (11).

Then, by using the output value of the acceleration sensor 520 at the detected temperature "td", "p _td", the value of each temperature dependent component of the detected temperature "td", "(b _td, s _td, q _td)" and the formula According to (1), the acceleration “r” of each detection axis including the misalignment error is calculated backward.

  Then, using the acceleration “r” including the calculated misalignment error and the misalignment coefficient matrix “M” stored in the misalignment coefficient table 555 of the storage unit 50, the true value of the acceleration according to the equation (5). “A” is calculated, and the value is output as a corrected output value.

3. Flow of processing 3-1. Processing of Correction Coefficient Calculation Device 2 FIG. 6 shows characteristic determination processing executed in the correction coefficient calculation device 2 when the characteristic determination program 51 stored in the storage unit 50 is read and executed by the processing unit 10. It is a flowchart which shows the flow.

  First, the test execution control unit 11 performs a test process by reading and executing the test program 511 stored in the storage unit 50 (step A1). Thereafter, the temperature coefficient calculation unit 13 reads and executes the temperature coefficient calculation program 513 stored in the storage unit 50, thereby performing a temperature coefficient calculation process (step A3).

  Next, the misalignment coefficient calculation unit 15 performs a misalignment coefficient calculation process by reading and executing the misalignment coefficient calculation program 515 stored in the storage unit 50 (step A5). Then, the characteristic determination process ends. Hereafter, each process of step A1-A5 is demonstrated using a flowchart.

FIG. 7 is a flowchart showing the flow of the test process.
First, the test execution control unit 11 sets an initial test posture of the sensor module 5 (step B1). For example, the sensor module 5 is fixed to the subject fixing device 340 in a posture (x-axis positive) such that the x-axis positive direction of the acceleration sensor 520 matches the absolute axis positive direction. And the test execution control part 11 performs the process of the loop A about each predetermined test temperature (step B3-B7).

  In the process of loop A, the test execution control unit 11 acquires the test data 54 from the test control device 310 and stores it in the test database 53 of the storage unit 50 (step B5). Then, the test execution control unit 11 shifts the processing to the next test temperature. After performing the process of step B5 for all the predetermined test temperatures, the test execution control unit 11 ends the process of loop A (step B7).

  Next, the test execution control unit 11 determines whether or not the test of the sensor module 5 has been completed for all predetermined test postures (for example, six postures) (step B9), and determines that the test has not yet been completed. In such a case (step B9; No), control for changing the test posture is performed (step B11). That is, when the posture of the sensor module 5 can be automatically displaced, the test control device 310 performs instruction control so as to change the test posture. Further, when changing manually, a setting for changing the attitude of the sensor module 5 is made.

  On the other hand, when it determines with the test having been complete | finished about all the test postures (step B9; Yes), the test execution control part 11 complete | finishes a test process.

FIG. 8 is a flowchart showing the flow of the temperature coefficient calculation process.
First, the temperature coefficient calculation part 13 performs the process of the loop C about each test temperature (step C1-C9).

In the process of the loop C, the temperature coefficient calculation unit 13 reads the output value of the acceleration sensor 520 for that test temperature "t" of the sample data of the "p _t" from the test database 53 (step C3). Then, the temperature coefficient calculation unit 13 uses the sample data of the output value “p _t ” and the sample data “(g, −g, 0)” of the gravitational acceleration, and the value of each temperature dependent component at the test temperature. “(B _t , _st , q _t )” is calculated using, for example, the least square method (step C7).

  And the temperature coefficient calculation part 13 transfers a process to the next test temperature. After performing the processing of steps C3 to C7 for all the test temperatures, the temperature coefficient calculation unit 13 ends the processing of loop C (step C9).

  Thereafter, the temperature coefficient calculation unit 13 calculates the temperature coefficient of each temperature-dependent component by using, for example, the least square method using each test temperature and the value of each temperature-dependent component at each test temperature (step S2). C11). Then, the temperature coefficient calculation unit 13 ends the temperature coefficient calculation process.

FIG. 9 is a flowchart showing the flow of misalignment coefficient calculation processing.
First, the misalignment coefficient calculation unit 15 selects a test temperature (step D1). That is, one test temperature is arbitrarily selected from a plurality of test temperatures.

Next, the misalignment coefficient calculation unit 15 uses the test temperature “t” selected in step D1 and the temperature coefficient of each temperature dependent component calculated in the temperature coefficient calculation process to obtain the value “(b _t, s _t, q _t) "is calculated (step D3).

Next, the misalignment coefficient calculation unit 15 uses the value “(b _t , _st , q _t )” of each temperature-dependent component calculated in step D3 and the output value “p _t ” of the acceleration sensor 520, The acceleration “r” including the misalignment error is calculated backward according to the equation (1) (step D5).

  Next, the misalignment coefficient calculating unit 15 calculates the misalignment coefficient using, for example, the least square method, using the gravitational acceleration “g” and the acceleration “r” including the misalignment error calculated in Step D7. (Step D7). Then, the misalignment coefficient calculation unit 15 ends the misalignment coefficient calculation process.

  When the characteristic determination process ends, the correction coefficient table creation unit 17 creates a temperature coefficient table 553 in which the temperature coefficient of each temperature-dependent component calculated in the temperature coefficient calculation process is stored in association with each detection axis. Further, a misalignment coefficient table 555 storing the misalignment coefficient matrix calculated in the misalignment coefficient calculation process is created. These tables are stored in the storage unit 50 as the correction coefficient table 55.

  The correction coefficient table 55 created by the correction coefficient table creation unit 17 is mounted on the sensor module 5. That is, when the test and characteristic determination of the sensor module 5 are completed in the test system 1, the correction coefficient table 55 created for the sensor module 5 is written in the storage unit 550 of the sensor module 5. The sensor module 5 is then shipped as a product.

3-2. Processing of Sensor Module 5 FIG. 10 shows a flow of correction output processing executed in the sensor module 5 when the correction output program 551 stored in the storage unit 550 is read and executed by the processing unit 510. It is a flowchart.

  First, the processing unit 510 reads the temperature coefficient of each temperature-dependent component from the temperature coefficient table 553 of the correction coefficient table 55 stored in the storage unit 550 (step E1). Further, the processing unit 510 reads a misalignment coefficient from the misalignment coefficient table 555 of the correction coefficient table 55 (Step E3).

Next, the processing unit 510 uses the detected temperature “td” of the temperature sensor 530 and the temperature coefficient of each temperature-dependent component read in step E1 to obtain the value “(b _td , _std , q for each temperature-dependent component”. _td ) "is calculated (step E5).

Then, the processing unit 510 uses the output value “p _td ” of the acceleration sensor 520 and the value “(b _td , _{st td} , q _td )” of each temperature-dependent component calculated in step E5 to make a misalignment error. The acceleration “r” including is calculated backward (step E7).

  Next, the processing unit 510 corrects the misalignment error using the acceleration “r” including the misalignment error and the misalignment coefficient matrix (Step E9), and outputs the corrected output value “a” from the output unit 540. (Step E11). After performing the series of processes, the processing unit 510 ends the correction output process.

4). Effects According to the present embodiment, the characteristic determination processing of the sensor module 5 including the acceleration sensor 520 is performed in the test system 1. That is, in the test apparatus 3, the sensor module 5 is fixed to the subject fixing apparatus 340 having the absolute axis determined so that the direction of the detection axis of the acceleration sensor 520 is the absolute axis direction. And the data acquisition process which records the output value of the acceleration sensor 520 is performed, changing the attitude | position of the sensor module 5, and the temperature inside the thermostat 320. FIG. Then, using the recorded output value of the acceleration sensor 520, the correction coefficient calculation device 2 calculates the temperature coefficient and the misalignment coefficient of the temperature-dependent component as correction coefficients.

  The acceleration sensor 520 is a kind of inertial sensor. In the test apparatus 3 in which the absolute axis direction is determined, the sensor module 5 is fixed in such a posture that each detection axis of the acceleration sensor 520 coincides with the absolute axis direction. Then, the misalignment error can be separated from the detection result of the acceleration sensor 520 by changing the posture of the sensor module 5 and recording the output value of the acceleration sensor 520 for each posture. Further, the temperature inside the thermostat 320 is changed and the same test is performed at a plurality of test temperatures to separate misalignment errors. Then, by performing approximate calculation using the output value of the acceleration sensor 520 and the gravitational acceleration, the temperature coefficient of the temperature-dependent component can be appropriately calculated.

  Further, the value of the temperature dependent component at the test temperature can be calculated from the predetermined test temperature and the temperature coefficient of the temperature dependent component. Then, by using the output value of each detection axis of the acceleration sensor 520 at the test temperature and the value of the temperature-dependent component at the test temperature, the acceleration including the misalignment error from which the temperature-dependent error is separated is calculated backward. it can. Then, by performing approximate calculation using acceleration including misalignment error and gravitational acceleration, the misalignment coefficient can be appropriately calculated.

  If only one of the x-axis, y-axis, and z-axis detection axes matches the absolute axis direction and the output value is obtained, the temperature coefficient of the acceleration sensor attached to that axis can be obtained. Only a part of the misalignment coefficient is obtained. By making the detection axes of the x axis, the y axis, and the z axis coincide with the absolute axis direction and detecting the acceleration of each detection axis, the temperature coefficient of each axis and all the coefficients of the 3-axis misalignment (3 × 3 Matrix).

5. Application Example The above-described sensor module 5 can be used by being mounted on various electronic devices. Further, instead of mounting the sensor module 5 on the electronic device, the acceleration sensor 520 may be mounted on the electronic device or a substrate in the electronic device. In this case, the characteristic determination process including the test process (FIG. 7) is not performed on the sensor module 5, but the process is performed on the electronic device in which the acceleration sensor 520 is mounted. The test environment temperature at this time is more preferably determined according to the operating temperature specification of the electronic device.

  Further, the correction output process of FIG. 10 is not performed by the processing unit 510 of the sensor module 5, but is performed by the processor of the electronic device. That is, the temperature sensor is mounted on the electronic device, and the processor of the electronic device performs a process of correcting the output value of the acceleration output from the acceleration sensor 520.

  A specific example of the electronic device is a portable navigation device. In the portable navigation device, the acceleration output correction value is mainly used for position calculation. In this case, it is more preferable to mount a gyro sensor in addition to the acceleration sensor on the portable navigation device. Note that an IMU (Inertial Measurement Unit) known as an inertial measurement unit may be mounted as a sensor module including an acceleration sensor and a gyro sensor.

  The portable navigation device calculates the position by performing an inertial navigation calculation process using the output correction value of the acceleration of the acceleration sensor and the output value of the angular velocity of the gyro sensor. Specifically, the moving speed is calculated by integrating the output correction value of acceleration, and the moving direction is calculated by integrating the output value of angular velocity. And the process which calculates the position of a portable navigation apparatus at any time using the moving speed vector which consists of the calculated moving speed and moving direction is performed.

  The portable navigation device may also perform position calculation using a satellite positioning system such as GPS (Global Positioning System). In this case, the final output position is determined using the absolute position (absolute position) calculated using the satellite positioning system and the relative position (relative position) calculated by the inertial navigation calculation processing. It is preferable to do so.

DESCRIPTION OF SYMBOLS 1 Test system, 2 Correction coefficient calculation apparatus, 3 Test apparatus, 5 Sensor module, 20 Input part, 30 Display part, 40 Communication part, 50 Memory | storage part, 60 bus | bath, 310 Test control apparatus, 320 Constant temperature bath, 340 Object fixation Apparatus, 350 temperature adjustment unit, 360 temperature sensor, 510 processing unit, 520 acceleration sensor, 530 temperature sensor, 540 output unit, 550 storage unit

Claims (6)

The output value of the first axis in the first posture with the first axis positive direction of the acceleration sensor as the direction of gravity, and the output of the first axis in the second posture with the negative direction of the first axis of the acceleration sensor as the direction of gravity. Obtaining a value by changing the operating environment temperature ;
Calculating a temperature-dependent characteristic of the acceleration sensor based on the acquired output values of the plurality of first axes ;
The temperature dependence characteristics, the output value of the first axis in the first posture, the output value of the second axis orthogonal to the first axis, and the third axis orthogonal to the first axis and the second axis A misalignment error of the acceleration sensor is calculated using the output value, the output value of the first axis in the second posture, the output value of the second axis, and the output value of the third axis. When,
Calibration data acquisition method including The calculation of the temperature-dependent characteristic includes a zero point bias and a scale included in the detection result value of the acceleration sensor using the output value of the first axis in each case where the posture and the operating environment temperature are changed. Including calculating the temperature dependence of the factor,
The calibration data acquisition method according to claim 1 . Calculating the temperature dependent characteristic further includes calculating a temperature dependent characteristic of a secondary sensitivity included in the value of the detection result of the acceleration sensor.
The calibration data acquisition method according to claim 2 . The acceleration sensor output correction method which correct | amends the output value of the said acceleration sensor using the temperature dependence characteristic acquired by the calibration data acquisition method as described in any one of Claims 1-3 , and operating environment temperature. An acceleration sensor output correction method for correcting an output value of the acceleration sensor using the temperature dependence characteristic acquired by the calibration data acquisition method according to claim 1 , an operating environment temperature, and a misalignment error. The output value of the first axis in the first posture with the first axis positive direction of the acceleration sensor as the direction of gravity, and the output of the first axis in the second posture with the negative direction of the first axis of the acceleration sensor as the direction of gravity. A data acquisition processing unit for acquiring values by changing the operating environment temperature;
A temperature-dependent characteristic calculating unit that calculates temperature-dependent characteristics of the acceleration sensor based on the acquired output values of the plurality of first axes ;
The temperature dependence characteristics, the output value of the first axis in the first posture, the output value of the second axis orthogonal to the first axis, and the third axis orthogonal to the first axis and the second axis Using the output value and the output value of the first axis, the output value of the second axis, and the output value of the third axis in the second posture, a mistake for calculating a misalignment error of the acceleration sensor An alignment error calculation unit;
Calibration data acquisition system with

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