Temperature characteristic correction method, temperature characteristic correction device, and sensor device

Abstract

To provide a technique for correcting the temperature characteristics of an inertial sensor, which change complexly within the operating temperature range.SOLUTION: A sensor device includes an inertial sensor, a temperature sensor for detecting the temperature of the inertial sensor, a memory unit for storing temperature characteristics indicating the relationship between the temperature and output value of the inertial sensor for each of a plurality of temperature ranges, and a computation processing unit for deriving a correction value for correcting the output value of the inertial sensor, on the basis of the temperature characteristics corresponding to the temperature range including the temperature detected by the temperature sensor to correct the output value using the correction value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a temperature characteristic correction method, a temperature characteristic correction device, and a sensor device. [Background technology]

[0002] It has been known that the output of an inertial sensor has temperature characteristics. A technology for correcting the output value for each temperature is known, for example, from Patent Document 1. Patent Document 1 discloses a technology for correcting the output signal from a detection circuit using a calibration curve that is quadratic or higher. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-170294 Summary of the Invention [Problem to be solved by the invention]

[0004] The output value of an inertial sensor may include temperature characteristics. For example, if an inertial sensor outputs a non-zero output value even when its true value should be zero, and if the output value fluctuates with temperature, the relationship between the temperature and the output value is called the temperature characteristic. The temperature characteristic may result in a sudden change in the output value within a certain temperature range, resulting in a complex temperature characteristic. For example, the output value may change suddenly and peak within a specific temperature range, but change more gradually with respect to temperature in other temperature ranges. Conventional technology has made it difficult to correct the temperature characteristic of an inertial sensor, which changes in a complex manner within the temperature range. [Means for solving the problem]

[0005] A temperature characteristic correction method as one embodiment for solving the above problem is a temperature characteristic correction method for correcting the temperature characteristic of an inertial sensor, and includes: a first approximation step of deriving an ith output value at the ith temperature from an ith approximation curve showing the relationship between the temperature and the output value in an ith temperature range including the ith temperature, for each case where i is 1 to n (n is an integer of 3 or more), based on the output value of the inertial sensor for each temperature; a second approximation step of deriving a jth approximation curve in a jth temperature range including the jth temperature, for each case where j is 1 to m (m is an integer of 2 or more), based on the ith temperature and the ith output value where i is 1 to n; and a correction step of deriving a correction value for correcting the output value of the inertial sensor at the temperature to be corrected, based on the jth approximation curve in the jth temperature range including the temperature to be corrected, and correcting the output value of the inertial sensor using the correction value.

[0006] One embodiment of a temperature characteristic correction device for solving the above problem is a temperature characteristic correction device that corrects the temperature characteristic of an inertial sensor, and based on the output value of the inertial sensor for each temperature, for each case where i is 1 to n (n is an integer of 3 or more), an i-th output value at the i-th temperature is derived from an i-th approximation curve showing the relationship between the temperature and the output value in an i-th temperature range including the i-th temperature, and based on the i-th temperature and the i-th output value for each case where j is 1 to m (m is an integer of 2 or more), a j-th approximation curve in a j-th temperature range including the j-th temperature is derived, and a correction value for correcting the output value of the inertial sensor at the temperature to be corrected is derived based on the j-th approximation curve in the j-th temperature range including the temperature to be corrected, and the output value is corrected using the correction value.

[0007] A sensor device as one embodiment for solving the above problem includes an inertial sensor, a temperature sensor that detects the temperature of the inertial sensor, a memory unit that stores temperature characteristics that indicate the relationship between the temperature and output value of the inertial sensor in each of a plurality of temperature ranges, and an arithmetic processing unit that derives a correction value that corrects the output value of the inertial sensor based on the temperature characteristics of the temperature range that includes the temperature detected by the temperature sensor, and corrects the output value using the correction value. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows an example of the configuration of a sensor device according to the first embodiment. [Figure 2] FIG. 10 is a diagram showing an example of temperature characteristics of an inertial sensor. [Figure 3] FIG. 10 is a graph showing the results of correcting the temperature characteristics of the inertial sensor based on one approximation curve. [Figure 4] FIG. 10 is a diagram showing the results of correcting the temperature characteristics of the inertial sensor based on an approximation curve for each temperature range. [Figure 5] 10 is a flowchart showing the derivation of an approximation curve. [Figure 6] A diagram showing the i-th temperature. [Figure 7] FIG. 10 is a graph showing output values ​​for each ith temperature. [Figure 8] FIG. 10 is a diagram showing the jth temperature range and spline curve. [Figure 9] 10 is a flowchart showing a correction process. DETAILED DESCRIPTION OF THE INVENTION

[0009] A preferred embodiment of the present invention will be described in detail below. Note that the present embodiment described below does not limit the content of the present invention as defined in the claims, and not all of the configurations described in the present embodiment are necessarily essential as means for solving the problems of the present invention.

[0010] (1) First embodiment 1 shows an example of the configuration of a sensor device 10 according to this embodiment. The sensor device 10 is a device that corrects and outputs the output value of an inertial sensor, and is connected to a microcontroller 20. The microcontroller 20 is connected to a host 30.

[0011] The sensor device 10 includes an inertial sensor 11, a temperature sensor 12, a storage unit 13, an arithmetic processing unit 14, and an interface 15. In this embodiment, the sensor device 10 is a device in which an integrated circuit device including the inertial sensor 11, the temperature sensor 12, the storage unit 13, the arithmetic processing unit 14, and the interface 15 is housed in a package. The integrated circuit device is an IC chip realized by a semiconductor.

[0012] The inertial sensor 11 is a sensor element that detects values ​​related to inertia, and in this embodiment is a gyro sensor. That is, the inertial sensor 11 outputs a signal corresponding to the angular velocity around the axis of the measurement object. The temperature sensor 12 is a sensor element that detects a value indicating temperature. In this embodiment, the temperature sensor 12 is provided near the inertial sensor 11 and outputs a value indicating the temperature of the inertial sensor 11.

[0013] The storage unit 13 is a storage medium capable of storing various types of information, and in this embodiment is a non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read-Only Memory). In this embodiment, the storage unit 13 stores temperature characteristics that indicate the relationship between the temperature and the output value of the inertial sensor. The temperature characteristics are the output values ​​of the inertial sensor 11 at each temperature when the sensor is stationary. In this embodiment, the temperature characteristics are described by a cubic equation that approximately indicates the relationship between the temperature and the output value. Therefore, the storage unit 13 stores coefficients of the cubic equation.

[0014] In this embodiment, the temperature range in which the inertial sensor 11 is used is divided into a plurality of temperature ranges, and the temperature characteristics in each temperature range are described by a cubic equation. Therefore, coefficients of the cubic equation are defined for each temperature range and stored in the storage unit 13 in association with the temperature range.

[0015] The arithmetic processing unit 14 includes an analog circuit and an A / D conversion circuit that converts analog signals from the analog circuit into digital data. The analog circuit includes circuits for detecting signals from the inertial sensor 11 and the temperature sensor 12. For example, the analog circuit may include an amplifier circuit that amplifies signals, a detection circuit such as a synchronous detection circuit, a gain adjustment circuit, an offset adjustment circuit, etc. The A / D conversion circuit is a circuit that converts the output of the analog circuit into a digital value.

[0016] The calculation processing unit 14 further includes a processor that performs predetermined processing based on the digital value, i.e., the output value of the inertial sensor 11. In this embodiment, the calculation processing unit 14 acquires the current temperature of the inertial sensor 11 as the correction target temperature based on the detection value of the temperature sensor 12. The calculation processing unit 14 also acquires, from the storage unit 13, a coefficient that indicates the temperature characteristics of the temperature range that includes the correction target temperature. The calculation processing unit 14 then derives a correction value that corrects the output value of the inertial sensor 11 based on the coefficient. In this embodiment, the calculation processing unit 14 corrects the output value of the inertial sensor 11 by subtracting the correction value from the output value of the inertial sensor 11 that indicates the angular velocity at the correction target temperature (if the correction value is negative, the negative sign of the correction value is deleted and the correction value is added).

[0017] The interface 15 is a circuit for communicating with the microcontroller 20, for example, a circuit for transmitting and receiving serial data. The communication standard is not limited, and it is possible to adopt, for example, a communication standard such as SPI or I2C, or a communication standard obtained by improving or modifying part of the SPI or I2C standard.

[0018] The microcontroller 20 is a processor capable of executing various processes and is connected to the sensor device 10 and the host 30. When detection data output from the sensor device 10 is input to the microcontroller 20, the microcontroller 20 executes various processes based on the detection data. The processes executed by the microcontroller 20 may be various processes. For example, the microcontroller 20 may perform processing in response to a command from the host 30, or may perform alignment correction to correct deviations in the attitude of the sensor device 10 from an ideal attitude, or correction of scale factors and nonlinearity. In this embodiment, the microcontroller 20 is an integrated circuit device and can be implemented by a processor such as an MPU, CPU, or DSP. The microcontroller 20 may also be implemented by an ASIC that uses automatic placement and routing, such as a gate array.

[0019] The host 30 is a computer that issues various instructions to the microcontroller 20 and acquires various data output by the microcontroller 20. The host 30 issues, for example, read requests and write requests to the microcontroller 20. In this embodiment, the host 30 can use a read command to cause the sensor device 10 to output and acquire the corrected value of the output value of the inertial sensor 11.

[0020] In the above configuration, the arithmetic processing unit 14 of the sensor device 10 corrects the output value of the inertial sensor 11 based on the approximation curve that indicates the temperature characteristics for each temperature range stored in the storage unit 13. Therefore, correction can be performed with higher accuracy than in a configuration in which the output value of the inertial sensor 11 is corrected based on a single approximation curve that indicates the temperature characteristics for the entire temperature range.

[0021] 2 to 4 are diagrams showing how the output value is corrected. Fig. 2 is a diagram showing an example of the temperature characteristics of the inertial sensor 11. Fig. 3 is a diagram showing the results of correcting the temperature characteristics of the inertial sensor 11 based on one approximation curve. Fig. 4 is a diagram showing the results of correcting the temperature characteristics of the inertial sensor 11 based on approximation curves for each temperature range. In these diagrams, the horizontal axis is temperature (°C) and the vertical axis is output value (dps: degree per second).

[0022] The temperature range in which the inertial sensor 11 according to this embodiment is used is -50°C to 90°C. In FIG. 2, the output value at each temperature when the inertial sensor 11 is stationary is indicated by a black circle. That is, measurements were performed under conditions in which the output value of the inertial sensor 11 should be 0 at all temperatures. As shown in FIG. 2, the temperature characteristics of the inertial sensor 11 include temperature ranges in which the output value changes rapidly with temperature and temperature ranges in which the output value changes gradually. For example, in the temperature range of -50°C to 0°C, the output value increases rapidly as the temperature rises from -50°C, peaks at around -30°C, and then decreases rapidly as the temperature rises further. On the other hand, in the temperature range above 0°C, the output value does not change much.

[0023] As described above, the output value of the inertial sensor 11 changes in a complex manner over the operating temperature range. It is extremely difficult to approximate such complex changes using a single multi-order approximation formula. Increasing the order of the approximation formula improves the approximation accuracy, but the improvement in accuracy is often insufficient. Figure 3 is a graph that approximates the temperature characteristics of the operating temperature range using a single third-order approximation formula, and plots the values ​​obtained by subtracting the approximate values ​​for each temperature indicated by the approximation formula from the output value of the inertial sensor 11 at each temperature. As shown in Figure 3, the magnitude of the output value tends to be smaller than in Figure 2, but the complex changes shown in Figure 2 also result in complex output values ​​after correction. As a result, the correction accuracy is low, and the correction accuracy varies depending on the temperature.

[0024] On the other hand, if the operating temperature range is divided into multiple temperature ranges and the temperature characteristics of each temperature range are approximated and corrected using a multi-order approximation formula for each temperature range, the correction accuracy can be improved. FIG. 4 shows an example in which the temperature characteristics of the operating temperature range are divided and the temperature characteristics of each divided temperature range are approximated and corrected using a third-order approximation formula. That is, this is a graph in which a process is performed for each temperature range to plot values ​​obtained by subtracting the approximate values ​​for each temperature indicated by the approximation formula from the output values ​​of the inertial sensor 11 at each temperature. As shown in FIG. 4, the magnitude of the output values ​​is smaller than that of FIG. 2, and the correction accuracy is approximately the same across the entire temperature range.

[0025] (1-1) Deriving the approximate curve In this embodiment, as described above, the operating temperature zone is divided into a plurality of temperature ranges, and correction is performed using an approximate equation for each temperature range. The derivation of the approximate equation will be described below. FIG. 5 is a flowchart showing the derivation of the approximate curve. Steps S100 to S140 shown in FIG. 5 are a first approximation step, and steps S150 to S155 are a second approximation step. These processes can be realized by a device for measuring the output value of the inertial sensor 11 and a computer that performs processing based on the measurement results of the measuring device.

[0026] The first approximation step is a process for identifying output values ​​at a plurality of temperatures included in the operating temperature range of the inertial sensor 11. Here, these plurality of temperatures are referred to as the i-th temperatures (where i is an integer from 1 to n, and n is an integer equal to or greater than 3), and the output value (approximate value of) at the i-th temperature is referred to as the i-th output value. In the first approximation step, first, a variable i for identifying the i-th temperature is initialized to 1 (step S100).

[0027] Next, the ith temperature is set (step S105). The ith temperature is a plurality of temperatures included in the operating temperature range. The ith temperature may be determined by various methods, for example, it is possible to adopt a configuration in which the ith temperature is set at regular intervals in the operating temperature range. FIG. 6 shows the same temperature characteristic as that of the inertial sensor 11 shown in FIG. 2, and the graph illustrates the first temperature T1 to the eighth temperature T8. Note that the temperatures shown in FIG. 6 are merely examples, and for example, the first temperature T1 may be greater than the lower limit of the operating temperature range, and the eighth temperature T8 may be less than the upper limit of the operating temperature range.

[0028] Next, a jth approximation curve in an i-th temperature range including the i-th temperature is derived (step S110). The i-th temperature range is a temperature zone including the i-th temperature, and is set over a predetermined range at least either before or after the i-th temperature. The size of the temperature range is arbitrary, for example, a predetermined size. Here, an example is assumed in which the i-th temperature range is set over the i-th temperature for each i-th temperature. FIG. 6 illustrates a second temperature range R2 set over the second temperature T2 and a first temperature range R1 set over the first temperature T1.

[0029] Once the i-th temperature range is set, the i-th approximation curve is derived based on the output values ​​at each temperature within the i-th temperature range. In this embodiment, the i-th approximation curve is a curve expressed by a cubic equation. The cubic equation is defined, for example, by identifying each coefficient of the cubic equation using the least squares method using the output values ​​for each temperature in the i-th temperature range. In Figure 6, the second approximation curve in the second temperature range R2 is shown as a solid curve.

[0030] Next, it is determined whether the variable i matches n, which is the maximum value of the variable i (step S115), and if it is determined that they do not match, the variable i is incremented (step S120) and the processing from step S105 onwards is repeated. If it is determined in step S115 that the variable i matches n, the first approximation curve to the nth approximation curve corresponding to the first temperature T1 to the nth temperature Tn, respectively, have already been derived, so the second approximation process from step S125 onwards is started.

[0031] In step S125, first, a variable j for specifying the jth temperature is initialized to 1 (step S125). Next, the jth temperature is set based on the i-th approximation curve derived in the first approximation step (step S130). Here, the j-th temperature is a plurality of temperatures included in the operating temperature range, and is the temperature at the boundary between the spline curves that are the j-th approximation curves described later. The j-th temperature may be determined by various methods, and for example, it is possible to adopt a configuration in which the j-th temperature is set at regular intervals in the operating temperature range. The j-th temperature and the i-th temperature may be the same or different. Here, an example in which both are the same will be described. In the example shown in FIG. 6, the j-th temperature is temperatures T1 to T8 shown in FIG. 6.

[0032] Next, the output value of the jth temperature is obtained based on the i-th approximation curve (step S135). That is, the j-th temperature is substituted into the i-th approximation curve, and the output value of the inertial sensor 11 at the j-th temperature is obtained. In FIG. 6, point P2 indicating the output value at the second temperature T2 is shown. Note that, since the output value of the j-th temperature is obtained based on the i-th approximation curve, it can also be said to be an approximation of the output value of the inertial sensor 11. Here, since i=j, the approximation value corresponds to the i-th output value at the i-th temperature.

[0033] Next, it is determined whether variable j matches m+1 (m+1 is the maximum value of variable j) (step S140), and if it is determined that they do not match, variable j is incremented (step S145) and the processes from step S130 onwards are repeated. If it is determined in step S140 that variable j matches m+1, output values ​​corresponding to the first temperature T1 through the (m+1)th temperature Tm+1 have been acquired. In Figure 7, points P1 through P8 are shown that indicate output values ​​corresponding to the first temperature T1 through the eighth temperature T8, respectively.

[0034] Next, a j-th approximation curve including the j-th temperature is derived for each of j=1 to m (step S150). In this embodiment, the j-th approximation curve is derived by deriving a spline curve. The spline curve can be derived by a known method. Specifically, since m+1 points Pj indicating the output value at the j-th temperature are generated, m cubic equations are defined with these P1 to Pm+1 as boundaries, and the respective coefficients are identified.

[0035] The cubic equation y that represents the jth approximate curve j For example, it is expressed as follows: y j =a 3,j (TT j ) 3 +a 2,j (TT j ) 2 +a 1,j (TT j )+a 0,j where T is the temperature, T j is the jth temperature, a 3,j ,a 2,j ,a 1,j ,a 0,j are the third order coefficient, the second order coefficient, the first order coefficient, and the zeroth order coefficient, respectively.

[0036] The j-th approximation curve is a cubic equation of the j-th temperature range (the section from Tj to Tj+1), and m cubic equations are defined. In FIG. 8, the j-th temperature range is shown as range Zj, and a total of seven ranges Z1 to Z7 are shown. The cubic equation y that shows the j-th approximation curve j is an approximate equation in each range Zj. A continuous curve made up of these m approximate equations is a spline curve, which is derived, for example, by solving 4m simultaneous equations based on the following conditions: Condition 1: The spline curve passes through all m points P1 to Pm Condition 2: The first derivative is continuous from point P2 to point Pm-1 Condition 3: The second derivative is continuous from point P2 to point Pm-1 Condition 4: The second derivative is 0 at points P1 and Pm

[0037] Once the coefficients are identified by solving the simultaneous equations, all m cubic equations are defined, and the spline curve is defined. In FIG. 8, seven cubic equations, i.e., y1 to y7, are shown as solid curves. The spline curve shown in FIG. 8 is composed of cubic equations for multiple temperature ranges, but is defined so that it changes smoothly at the jth temperature boundary according to the above-mentioned conditions. Therefore, the spline curve changes smoothly in the operating temperature range of the inertial sensor 11. Furthermore, the spline curve is defined by dividing the operating temperature range into multiple temperature ranges and defining a separate cubic equation for each temperature range. Therefore, compared to a configuration in which an approximation curve is generated using a single polynomial equation across the entire operating temperature range, it is possible to accurately reproduce the complexly changing temperature characteristics of the inertial sensor.

[0038] Once the j-th approximation curve is obtained for each of j=1 to m in this manner, the coefficients representing the j-th approximation curve are stored in the storage unit 13 (step S155). That is, each of the coefficients representing the j-th approximation curve is associated with the j-th temperature range and stored in the storage unit 13. This process is performed, for example, by outputting a write command from the host 30 to the storage unit 13. That is, when the write command is output, the microcontroller 20 obtains the value of the coefficient associated with the j-th temperature range from the host 30 and stores it in the storage unit 13 of the sensor device 10.

[0039] (1-2) Correction processing Next, a correction process based on the temperature characteristics stored in the memory unit 13 will be described. FIG. 9 is a flowchart showing the correction process executed by the arithmetic processing unit 14. When power supply to the sensor device 10 starts, the arithmetic processing unit 14 periodically executes the correction process shown in FIG. 9. In the correction process, the arithmetic processing unit 14 acquires the detection value of the temperature sensor 12 (step S200). That is, the arithmetic processing unit 14 identifies the current temperature of the inertial sensor 11 based on the detection value of the temperature sensor 12, and regards it as the temperature to be corrected.

[0040] Next, the calculation processing unit 14 identifies a temperature range that includes the correction target temperature (step S205). That is, the calculation processing unit 14 refers to the storage unit 13 and identifies a temperature range that includes the correction target temperature from the j-th temperature range.

[0041] Next, the calculation processing unit 14 acquires coefficients of the approximation curve corresponding to the specified temperature range (step S210). That is, the calculation processing unit 14 refers to the storage unit 13 and acquires the third-order coefficient, the second-order coefficient, the first-order coefficient, and the zero-order coefficient associated with the temperature range specified in step S205.

[0042] Next, the calculation processing unit 14 acquires the correction value at the correction target temperature (step S215). That is, the calculation processing unit 14 calculates the coefficient acquired in step S210 by the formula y j =a 3,j (TT j ) 3 +a 2,j (TT j ) 2 +a 1,j (TT j )+a 0,j The jth temperature corresponding to the temperature range is substituted into the cubic equation to define a cubic equation, and the correction target temperature is substituted into the cubic equation. The calculation processing unit 14 obtains the obtained value as the correction value at the correction target temperature.

[0043] Next, the calculation processing unit 14 corrects the output value of the inertial sensor 11 based on the correction value (step S220). That is, the calculation processing unit 14 corrects the output value of the inertial sensor 11 by subtracting the correction value from the output value of the inertial sensor 11 (if the correction value is negative, the negative sign of the correction value is deleted and the correction value is added). The calculation processing unit 14 outputs the corrected value to the microcontroller 20 via the interface 15.

[0044] In the above configuration, the cubic equation, which is the approximate curve of the temperature characteristics, is defined for each of the multiple temperature ranges obtained by dividing the operating temperature range. Therefore, compared to a configuration in which an approximate curve is generated using a single multi-degree equation across the entire operating temperature range, it is possible to accurately correct the temperature characteristics of the inertial sensor, which change in a complex manner.

[0045] (2) Other embodiments The above-described embodiment is an example for implementing the present invention, and various other embodiments are also possible. For example, the sensor device 10 is not limited to the configuration shown in FIG. 1 , and various modifications are possible, such as omitting some of its components or adding other components. For example, in FIG. 1 , the microcontroller 20 controls one sensor device 10, but multiple sensor devices may be connected to the microcontroller 20, and the microcontroller 20 may perform processing based on the output of each sensor device. In this case, the measurement targets of the multiple inertial sensors may be inertia about the same axis or inertia about different axes.

[0046] Furthermore, the arithmetic processing unit that corrects the output value based on the correction value may be a microcontroller 20. Furthermore, the i-th approximation curve and the j-th approximation curve are not limited to cubic curves, but may be quadratic curves or curves of higher degrees. Furthermore, the sensor device may be used for various purposes. For example, it may be used in various electronic devices and in-vehicle devices. Examples of in-vehicle devices include various navigation devices and autonomous driving control devices. It may also be used in positioning devices that measure the position of a vehicle.

[0047] The inertial sensor may be any sensor that detects values ​​for evaluating inertia, such as an acceleration sensor, an angular acceleration sensor, or a velocity sensor. The temperature characteristic is the relationship between temperature and the output of the inertial sensor. The output of the inertial sensor in terms of the temperature characteristic may be the output value itself, or a value obtained by correcting the bias by subtracting a certain bias value from the output value, for example.

[0048] The first approximation step may be any step of deriving an ith approximation curve based on the output values ​​of the inertial sensor for each temperature and deriving an ith output value at the ith temperature. That is, the first approximation step may be any step of deriving output values ​​at multiple temperatures (ith temperatures) based on the output values ​​of the inertial sensor for each temperature. Therefore, the ith approximation curve is not limited, and any curve that approximately reproduces the output values ​​for each temperature can be the ith approximation curve. Also, output values ​​at multiple temperatures (ith temperatures) may be derived without using an approximation curve. For example, the ith output value at the ith temperature may be derived based on statistics of the output values ​​at the ith temperature or statistics of the output values ​​at the ith temperature and its surrounding temperatures.

[0049] i may be any number indicating each of multiple (n) temperatures, and may be 3 or greater. For example, it may be set to satisfy the number of temperatures required to correct the temperature characteristics of the inertial sensor. Furthermore, the upper limit n of i may be larger as the temperature range to be corrected for the temperature characteristics becomes wider, or as the order of the approximation curve used in the second approximation step becomes larger. The multiple temperatures indicated by the i-th temperature may be temperatures at equal intervals or may be temperatures at unequal intervals.

[0050] The second approximation step only needs to be able to derive the i-th temperature and i-th output value, where i is 1 to n, and the j-th approximation curve in the j-th temperature range. That is, the second approximation step only needs to be able to derive the j-th approximation curve showing the temperature characteristics in each of a plurality of temperature ranges based on the results of the first approximation step. Therefore, the j-th approximation curve is not limited, and any curve that approximately reproduces the output value for each temperature can be the j-th approximation curve. For example, the j-th approximation curve may not be a spline curve, but may be a multi-order curve for each j-th temperature range, in which the derivative at the boundary may be discontinuous.

[0051] j may be any number indicating each of multiple (m) temperatures, and may be 2 or greater. For example, j may be set to satisfy the number of temperatures required to correct the temperature characteristics of the inertial sensor. Furthermore, the upper limit value m+1 of j may be larger as the temperature range to be corrected for the temperature characteristics becomes wider, or as the order of the approximation curve used in the second approximation step becomes larger. The multiple temperatures indicated by the jth temperature may be temperatures at equal intervals or at unequal intervals.

[0052] The correction step may derive a correction value for correcting the output value of the inertial sensor at the correction target temperature based on a j-th approximation curve in a j-th temperature range including the correction target temperature, and may correct the output value using the correction value. That is, the j-th temperature range including the correction target temperature is selected from the j-th approximation curves derived for m temperature ranges, and a correction value for the correction target temperature is derived based on the j-th approximation curve that shows the temperature characteristics in the j-th temperature range. The correction value may be data that makes the error between the output value and the true value zero or approximately zero.

[0053] The temperature sensor may be any sensor that detects the temperature of the inertial sensor, and the correction target temperature is determined based on the detected value of the temperature sensor. For example, the current temperature detected by the temperature sensor is considered to be the correction target temperature. The number of temperature sensors is not limited. For example, in a sensor unit using multiple inertial sensors, multiple temperature sensors may be used to detect the temperatures of the respective inertial sensors, or the temperatures of the multiple inertial sensors may be detected by a single temperature sensor. Furthermore, the distance between the temperature sensor and the inertial sensor is arbitrary as long as the temperature of the inertial sensor can be determined based on the detected value of the temperature sensor.

[0054] The storage unit is only required to store temperature characteristics indicating the relationship between the temperature and output value of the inertial sensor in each of a plurality of temperature ranges. That is, the storage unit is only required to store data for specifying the output value and the correction value for the output value based on the correction target temperature. Such data may be information indicating the coefficients of the jth approximation curve described above, or may be table data indicating the correspondence between a plurality of temperatures and output values, or may take any form.

[0055] The calculation processing unit is only required to derive a correction value for correcting the output value of the inertial sensor based on the temperature characteristics of the temperature range that includes the temperature detected by the temperature sensor, and to correct the output value using the correction value. That is, the calculation processing unit is only required to derive a correction value for making the error between the output value of the correction target temperature and the true value zero or approximately zero based on the temperature characteristics stored in the storage unit, and to correct the output value of the inertial sensor using the correction value. [Explanation of symbols]

[0056] 10...sensor device, 11...inertial sensor, 12...temperature sensor, 13...memory unit, 14...arithmetic processing unit, 15...interface, 20...microcontroller, 30...host

Claims

1. A temperature characteristic correction method for correcting a temperature characteristic of an inertial sensor, comprising: a first approximation step of deriving an i-th output value at the i-th temperature from an i-th approximation curve showing the relationship between temperatures and the output value in an i-th temperature range including the i-th temperature, for each case where i is 1 to n (n is an integer of 3 or more), based on the output value of the inertial sensor for each temperature; a second approximation step of deriving a j-th approximation curve in a j-th temperature range including the j-th temperature for each of j ranges from 1 to m (m is an integer of 2 or more) based on the i-th temperature and the i-th output value for each of i ranges from 1 to n; a correction step of deriving a correction value for correcting the output value of the inertial sensor at the correction target temperature based on the jth approximation curve in the jth temperature range including the correction target temperature, and correcting the output value using the correction value; A temperature characteristic compensation method including:

2. The i-th approximation curve is a curve represented by a cubic equation. The temperature characteristic correction method according to claim 1 .

3. The jth approximation curve is a curve represented by a cubic equation.

3. The temperature characteristic correction method according to claim 1.

4. A temperature characteristic correction device that corrects the temperature characteristic of an inertial sensor, based on the output value of the inertial sensor for each temperature, for each of i being 1 to n (n being an integer of 3 or more), an i-th output value at the i-th temperature is derived from an i-th approximation curve showing the relationship between temperatures in an i-th temperature range including the i-th temperature and the output value; a jth approximation curve in a jth temperature range including the jth temperature is derived for each of j's ranges from 1 to m (m is an integer of 2 or more) based on the i'th temperature and the i'th output value for i's range from 1 to n; deriving a correction value for correcting the output value of the inertial sensor at the correction target temperature based on the jth approximation curve in the jth temperature range including the correction target temperature, and correcting the output value using the correction value; Temperature characteristic correction device.

5. an inertial sensor; a temperature sensor for detecting a temperature of the inertial sensor; a storage unit that stores temperature characteristics indicating a relationship between a temperature and an output value of the inertial sensor in each of a plurality of temperature ranges; a calculation processing unit that derives a correction value for correcting the output value of the inertial sensor based on the temperature characteristics of the temperature range that includes the temperature detected by the temperature sensor, and corrects the output value using the correction value; A sensor device comprising:

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