JP6370261B2 - Inclination angle calculation device - Google Patents

Description

  The present invention relates to an inclination angle calculation device that calculates an inclination angle of a road surface or a moving body using an acceleration sensor.

  Conventionally, using an acceleration sensor mounted on a vehicle, an inclination angle of a road surface with respect to a horizontal plane (hereinafter referred to as “road surface gradient angle”) or an inclination angle of a vehicle body in the longitudinal direction of the vehicle with respect to the road surface (hereinafter referred to as “pitching angle”). An inclination angle calculation device for calculating the angle has been developed. The value of the road surface gradient angle is used, for example, by the navigation device for correcting information indicating the turning angle and the current position of the vehicle, or by the attitude control device for assisting the vehicle in starting a hill. The value of the pitching angle is used, for example, by the optical axis adjustment device for adjusting the optical axis of the headlight. Patent Document 1 discloses an inclination detection device that calculates a pitching angle using an acceleration value along the longitudinal direction of a vehicle, and an optical axis direction adjustment device that uses the inclination detection device.

An example of processing for calculating the pitching angle using acceleration along the longitudinal direction of the vehicle will be described. The acceleration along the longitudinal direction of the vehicle is Gx, the road surface gradient angle is θ1 (hereinafter, the unit of the angle when no unit is specified is radians), the pitching angle is θ2, and the gravitational acceleration is g. When the vehicle is stopped, the total value θ1 + θ2 of the road surface gradient angle θ1 and the pitching angle θ2 is expressed by the following equation (1).
Gx = −g · sin (θ1 + θ2) (1)

If θ1 + θ2 is a minute angle, sin (θ1 + θ2) ≈θ1 + θ2 is established, and equation (1) is approximated by the following equation (2).
Gx = −g (θ1 + θ2) (2)

Usually, when the vehicle is stopped, the road surface gradient angle θ1 does not change, so that the change amount of −Gx / g becomes equal to the change amount of the pitching angle θ2, as shown in the following equation (3).
-ΔGx / g = Δθ2 (3)

When the optical axis of the headlight is raised once by the passenger riding on the host vehicle or loading the luggage, the light of the headlight is irradiated to the driver's seat of the oncoming vehicle, and the driver of the oncoming vehicle is dazzled. For this reason, the optical axis adjusting device is required to adjust the optical axis of the headlight with an accuracy of 0.1 degree. In order for the tilt angle calculation device to calculate the pitching angle with an accuracy of 0.1 degree, the acceleration sensor has an accuracy of several millimeters G (mG) with G being 10 millimeters per second (mm / s ² ). It is required to detect acceleration.

In general, some characteristic values of an acceleration sensor change with temperature. Since an in-vehicle inclination angle calculation device usually uses an inexpensive acceleration sensor, the variation range of the characteristic value with respect to temperature is large. For example, the value of the sensor output (hereinafter referred to as “offset”) in a state where no acceleration is applied has a variation range of about 100 to 1000 mm / s ² , that is, about 10 to 100 mG. Therefore, in order to detect the acceleration with an accuracy of several mG, it is important to correct the offset value at each temperature and bring it closer to the target value. In addition, it is preferable that the characteristic values other than the offset such as sensitivity are close to the target value.

  In the load sensor of Patent Document 2, an IC (Integrated Circuit) chip for sensitivity adjustment is integrated in a processing unit of the load sensor, and the temperature characteristic of sensitivity is compensated for components. In addition, the processing unit includes a correction circuit for adjusting offset and temperature drift. The load sensor disclosed in Patent Document 2 selects three temperatures: a reference room temperature, a temperature higher than the reference room temperature, and a temperature lower than the reference room temperature, and arbitrarily sets a temperature drift adjustment voltage to the processing unit under each temperature condition. The temperature drift of the sensor output is adjusted by applying at least two points.

JP 2009-126268 A JP-A-2005-308591

  The load sensor of Patent Document 2 uses a load sensor processing unit for correction of sensitivity, offset, and temperature drift. However, as described above, since the in-vehicle tilt angle calculation device uses an inexpensive acceleration sensor, the number of circuit elements in the processing unit in the sensor is limited, and the processing capability is low. For this reason, even if the technique of Patent Document 2 is applied to an in-vehicle inclination angle calculation device, the correction accuracy is low, and the characteristic value cannot be sufficiently close to the target value. As a result, there has been a problem that the calculation accuracy of the tilt angle is low.

  The present invention has been made to solve the above-described problems, and provides an inclination angle calculation device capable of correcting a characteristic value of an acceleration sensor with high accuracy using an acceleration sensor with low processing capability. The purpose is to do.

  The tilt angle calculation apparatus of the present invention includes a temperature sensor that detects temperature, an acceleration detection unit that detects acceleration, a first temperature, a second temperature lower than the first temperature, and a third temperature higher than the first temperature. An acceleration sensor comprising: a first characteristic value correction unit that corrects a characteristic value at a detected temperature of the temperature sensor using a primary correction formula including a characteristic value of the acceleration detection unit at any two of the temperatures; and an acceleration sensor And the characteristic value at the detected temperature is corrected using a secondary correction formula including a characteristic value at a temperature different from the primary correction formula among the first temperature, the second temperature, and the third temperature. Using the acceleration value corrected by the second characteristic value correction unit and the characteristic value corrected by the first characteristic value correction unit and the second characteristic value correction unit, an inclination sensor of the road surface with respect to the horizontal plane or an acceleration sensor for the road surface is provided. Inclined moving body And the inclination angle calculation unit that calculates a are those comprising a.

  In the tilt angle calculation apparatus of the present invention, the first characteristic value correction unit of the acceleration sensor corrects the characteristic value using the primary correction formula, and the second characteristic value correction unit configured separately from the acceleration sensor has the secondary characteristic value. The characteristic value is corrected using a correction formula. As a result, the processing load of the acceleration sensor can be reduced, and the characteristic value can be corrected with high accuracy using an acceleration sensor with low processing capability. As a result, the calculation accuracy of the tilt angle can be improved.

It is explanatory drawing which shows the hardware constitutions of the inclination-angle calculation apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the principal part of the inclination-angle calculation apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the 1st characteristic value correction | amendment part and 1st acceleration correction part which concern on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the 2nd characteristic value correction | amendment part and 2nd acceleration correction part which concern on Embodiment 1 of this invention. It is a characteristic view which shows the detection sensitivity of the acceleration sensor with respect to temperature. It is a characteristic view which shows the offset of the acceleration sensor with respect to temperature. It is a flowchart which shows operation | movement of the 2nd characteristic value correction | amendment part and 2nd acceleration correction part which concern on Embodiment 2 of this invention. It is a characteristic view which shows the detection sensitivity of the acceleration sensor with respect to temperature. It is a characteristic view which shows the offset of the acceleration sensor with respect to temperature. It is a flowchart which shows operation | movement of the 1st characteristic value correction | amendment part and 1st acceleration correction part which concern on Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the 2nd characteristic value correction | amendment part and 2nd acceleration correction part which concern on Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the 1st characteristic value correction | amendment part and 1st acceleration correction part which concern on Embodiment 4 of this invention. It is a flowchart which shows operation | movement of the 2nd characteristic value correction | amendment part and 2nd acceleration correction part which concern on Embodiment 4 of this invention. It is a characteristic view which shows the detection sensitivity of the acceleration sensor with respect to temperature. It is a characteristic view which shows the offset of the acceleration sensor with respect to temperature. It is a flowchart which shows operation | movement of the 2nd characteristic value correction | amendment part and 2nd acceleration correction part which concern on Embodiment 5 of this invention. It is a characteristic view which shows the detection sensitivity of the acceleration sensor with respect to temperature. It is a characteristic view which shows the offset of the acceleration sensor with respect to temperature.

Embodiment 1 FIG.
FIG. 1 is an explanatory diagram illustrating a hardware configuration of the tilt angle calculation apparatus 100. As shown in FIG. 1, the tilt angle calculation device 100 is mounted on the vehicle body of a vehicle A, and includes a temperature sensor 1, an acceleration sensor 2, and a microcontroller (hereinafter referred to as “microcomputer”) 3. FIG. 2 is a block diagram illustrating a main part of the tilt angle calculation apparatus 100. With reference to FIG.1 and FIG.2, the inclination-angle calculation apparatus 100 of Embodiment 1 is demonstrated.

  The temperature sensor 1 is configured by, for example, a MEMS (Micro Electro Mechanical Systems), a thermistor, or a thermal diode, and is disposed adjacent to the acceleration sensor 2. The temperature sensor 1 detects the temperature of the acceleration sensor 2 and outputs the value of the detected temperature T to the acceleration sensor 2 and the microcomputer 3.

  The acceleration sensor 2 is composed of, for example, MEMS, and includes an acceleration detection unit 21, a first characteristic value correction unit 22, and a first acceleration correction unit 23.

  The acceleration detector 21 detects the acceleration Gx of the first axis along the longitudinal direction of the vehicle body of the vehicle A. Further, the acceleration detector 21 detects the acceleration Gz of the second axis along the vertical direction of the vehicle body of the vehicle A.

  The first characteristic value correction unit 22 corrects the characteristic value of the acceleration detection unit 21 at the detection temperature T of the temperature sensor 1 using a primary correction formula preset in the acceleration sensor 2. The characteristic value corrected by the first characteristic value correcting unit 22 is a characteristic value whose value changes with temperature. Specifically, for example, the detection sensitivity Sx of the acceleration Gx, the detection sensitivity Sz of the acceleration Gz, the offset Ox of the acceleration Gx, and the offset Oz of the acceleration Gz.

  The first acceleration correction unit 23 uses the values of the detection sensitivities S1x and S1z and the offsets O1x and O1z corrected by the first characteristic value correction unit 22 to determine the values of the accelerations Gx and Gz detected by the acceleration detection unit 21. It is to correct. The first acceleration correction unit 23 outputs the corrected acceleration G1x and G1z values to the microcomputer 3.

  The microcomputer 3 is configured separately from the acceleration sensor 2 and is provided outside the acceleration sensor 2. The microcomputer 3 includes a second characteristic value correction unit 31, a second acceleration correction unit 32, and an inclination angle calculation unit 33.

  The second characteristic value correction unit 31 corrects the characteristic value of the acceleration detection unit 21 at the detection temperature T of the temperature sensor 1 using a secondary correction formula preset in the microcomputer 3. The characteristic value corrected by the second characteristic value correction unit 31 is a characteristic value whose value changes with temperature. Specifically, for example, the detection sensitivity Sx of the acceleration Gx, the detection sensitivity Sz of the acceleration Gz, the offset Ox of the acceleration Gx, and the offset Oz of the acceleration Gz.

  The second acceleration correction unit 32 uses the values of the detection sensitivities S2x and S2z and the offsets O2x and O2z corrected by the second characteristic value correction unit 31, and outputs the values after correction by the first acceleration correction unit 23. The values of the accelerations G1x and G1z thus corrected are further corrected.

  The vehicle A is equipped with a wheel speed sensor 10 that detects the rotational speed of a traveling wheel. Further, the vehicle A is equipped with an ECU (Electronic Control Unit) 11 that calculates the traveling speed V of the vehicle A using the speed signal output from the wheel speed sensor 10. The ECU 11 transmits the calculated value of the traveling speed V to the microcomputer 3 via an in-vehicle communication network based on a so-called CAN (Controller Area Network) standard or a LIN (Local Interconnect Network) standard.

  The inclination angle calculation unit 33 uses the values of the accelerations G2x and G2z corrected by the second acceleration correction unit 32 and the value of the traveling speed V received from the ECU, and the inclination angle of the vehicle body of the vehicle A with respect to the road surface B. The pitching angle θ2 is calculated as follows. The tilt angle calculation unit 33 outputs the calculated pitching angle θ2 to the optical axis adjustment device 12 mounted on the vehicle A.

  The temperature sensor 1, the acceleration sensor 2, and the microcomputer 3 are mounted on an electronic circuit board (not shown). In this way, the tilt angle calculation device 100 is configured.

Next, the primary correction formula will be described.
The manufacturer of the acceleration sensor 2 sets values of the first temperature TC, the second temperature TL lower than the first temperature TC, and the third temperature TH higher than the first temperature TC. The first temperature TC is, for example, a value equivalent to normal temperature in the usage environment of the tilt angle calculation device 100. The second temperature TL is, for example, a value equivalent to the lower limit value of the operation guarantee temperature of the acceleration sensor 2. The third temperature TH is, for example, a value equivalent to the upper limit value of the operation guarantee temperature of the acceleration sensor 2.

In general, the detection sensitivity S of the acceleration detector 21 is expressed by the following equation (4), where G1out is the output value for the input value G1in and G2out is the output value for the input value G2in.
S = (G1out-G2out) / (G1in-G2in) (4)

  The manufacturer of the acceleration sensor 2 measures the characteristic value of the acceleration detector 21 after manufacturing the acceleration sensor 2. Specifically, the acceleration Gx detection sensitivity SCx, the acceleration Gz detection sensitivity SCz, the acceleration Gx offset OCx, and the acceleration Gz offset OCz at the first temperature TC are measured. Further, the acceleration sensor 2 is placed in a low temperature bath, and the acceleration Gx detection sensitivity SLx, the acceleration Gz detection sensitivity SLz, the acceleration Gx offset OLx, and the acceleration Gz offset OLz at the second temperature TL are measured.

The manufacturer of the acceleration sensor 2 stores the values of the first temperature TC, the second temperature TL, the detection sensitivities SCx, SCz, SLx, SLz and the offsets OCx, OCz, OLx, OLz in a storage unit (not shown) of the acceleration sensor 2. Let The manufacturer of the acceleration sensor 2 sets the following formulas (5) to (8) in the acceleration sensor 2 as primary correction formulas. Expressions (5) to (8) are expressions expressed as linear functions of the temperature T.
S1x = SCx + (SLx−SCx) × (T−TC) / (TL−TC) (5)
S1z = SCz + (SLz−SCz) × (T−TC) / (TL−TC) (6)
O1x = OCx + (OLx−OCx) × (T−TC) / (TL−TC) (7)
O1z = OCz + (OLz−OCz) × (T−TC) / (TL−TC) (8)

Next, the secondary correction formula will be described.
The manufacturer of the tilt angle calculation device 100 assembles the tilt angle calculation device 100 by mounting the temperature sensor 1, the acceleration sensor 2, and the microcomputer 3 on the electronic circuit board. Next, the manufacturer of the tilt angle calculation device 100 measures the characteristic value of the acceleration detection unit 21. Specifically, the acceleration Gx detection sensitivity SCx, the acceleration Gz detection sensitivity SCz, the acceleration Gx offset OCx, and the acceleration Gz offset OCz at the first temperature TC are measured. In addition, the tilt angle calculation device 100 is placed in a high-temperature bath, and the acceleration Gx detection sensitivity SHx, the acceleration Gz detection sensitivity SHz, the acceleration Gx offset OHx, and the acceleration Gz offset OHz at the third temperature TH are measured.

The manufacturer of the tilt angle calculation device 100 stores the values of the first temperature TC, the third temperature TH, the detection sensitivities SCx, SCz, SHx, SHz and the offsets OCx, OCz, OHx, OHz in a storage unit (not shown) of the microcomputer 3. Remember. Further, the manufacturer of the tilt angle calculation apparatus 100 sets the following formulas (9) to (12) in the microcomputer 3 as secondary correction formulas. Expressions (9) to (12) are expressions expressed as linear functions of the temperature T.
S2x = SCx + (SHx-SCx) * (T-TC) / (TH-TC) (9)
S2z = SCz + (SHz−SCz) × (T−TC) / (TH−TC) (10)
O2x = OCx + (OHx-OCx) * (T-TC) / (TH-TC) (11)
O2z = OCz + (OHz−OCz) × (T−TC) / (TH−TC) (12)

Next, operations of the first characteristic value correction unit 22 and the first acceleration correction unit 23 will be described with reference to the flowchart of FIG.
First, in step ST <b> 1, the first characteristic value correction unit 22 acquires the value of the detected temperature T from the temperature sensor 1. In step ST <b> 2, the first acceleration correction unit 23 acquires values of accelerations Gx and Gz detected by the acceleration detection unit 21. The first characteristic value correction unit 22 and the first acceleration correction unit 23 repeat the processes of steps ST1 and ST2 at predetermined time intervals (for example, at intervals of 0.1 seconds) while power is supplied to the acceleration sensor 2.

  Next, in step ST3, the first characteristic value correction unit 22 corrects the detection sensitivity Sx of the acceleration detection unit 21 at the detection temperature T using the primary correction formula of Formula (5). Similarly, in Step ST4, the first characteristic value correction unit 22 corrects the detection sensitivity Sz of the acceleration detection unit 21 at the detection temperature T using the primary correction formula of Formula (6). In step ST5, the first characteristic value correction unit 22 corrects the offset Ox of the acceleration detection unit 21 at the detection temperature T using the primary correction formula of Formula (7). In step ST6, the first characteristic value correction unit 22 corrects the offset Oz of the acceleration detection unit 21 at the detection temperature T using the primary correction formula of Formula (8).

Next, in step ST7, the first acceleration correction unit 23 obtains in step ST2 using the detection sensitivities S1x and S1z and the offsets O1x and O1z corrected by the first characteristic value correction unit 22 in steps ST3 to ST6. The values of the accelerations Gx and Gz are corrected. At this time, the first acceleration correction unit 23 corrects the values of the accelerations Gx and Gz using the following equations (13) and (14). The first acceleration correction unit 23 outputs the values of the accelerations G1x and G1z after correcting the accelerations Gx and Gy before correction to the microcomputer 3.
G1x = (Gx−O1x) / S1x (13)
G1z = (Gz-O1z) / S1z (14)

Next, operations of the second characteristic value correction unit 31 and the second acceleration correction unit 32 will be described with reference to the flowchart of FIG.
First, in step ST <b> 11, the second characteristic value correction unit 31 acquires the value of the detected temperature T from the temperature sensor 1. In step ST12, the second acceleration correction unit 32 acquires the values of the accelerations G1x and G1z output from the first acceleration correction unit 23. The second characteristic value correction unit 31 and the second acceleration correction unit 32 repeat the processes of steps ST11 and ST12 at predetermined time intervals (for example, at intervals of 0.1 seconds) while power is supplied to the microcomputer 3.

  Next, in step ST13, the second characteristic value correction unit 31 determines whether or not the detected temperature T acquired in step ST11 is lower than the first temperature TC. When the detected temperature T is equal to or higher than the first temperature TC (step ST13 “NO”), in step ST14, the second characteristic value correction unit 31 uses the secondary correction formula of formula (9) to detect the detected temperature T. The detection sensitivity Sx of the acceleration detection unit 21 is corrected. Similarly, in step ST15, the second characteristic value correction unit 31 corrects the detection sensitivity Sz of the acceleration detection unit 21 at the detection temperature T using the secondary correction formula of Formula (10). In step ST16, the second characteristic value correcting unit 31 corrects the offset Ox of the acceleration detecting unit 21 at the detected temperature T using the secondary correction formula of Formula (11). In step ST <b> 17, the second characteristic value correction unit 31 corrects the offset Oz of the acceleration detection unit 21 at the detection temperature T using the secondary correction formula of Formula (12).

Next, in step ST18, the second acceleration correction unit 32 acquires in step ST12 using the detection sensitivities S2x and S2z and the offsets O2x and O2z corrected by the second characteristic value correction unit 31 in steps ST14 to ST17. The values of the accelerations G1x and G1z are corrected. At this time, the second acceleration correction unit 32 corrects the values of the accelerations Gx and Gz using the following equations (15) and (16).
G2x = (G1x-O2x) / S2x (15)
G2z = (G1z-O2z) / S2z (16)

On the other hand, when the detected temperature T is lower than the first temperature TC (step ST13 “YES”), the second characteristic value correction unit 31 notifies the second characteristic value correction unit 31 to that effect. In step ST19, as shown in the following formulas (17) and (18), the second characteristic value correction unit 31 uses the acceleration G1x and G1z values output by the first acceleration correction unit 23 as the accelerations G2x and G2z. Set to value.
G2x = G1x (17)
G2z = G1z (18)

Next, an example of processing in which the tilt angle calculation unit 33 calculates the pitching angle θ2 will be described.
The inclination angle calculation unit 33 compares the value of the traveling speed V of the vehicle A with 0 and determines whether or not the vehicle A is stopped. When the vehicle A is stopped, the inclination angle calculation unit 33 calculates the total value θ1 + θ2 of the road surface gradient angle θ1 and the pitching angle θ2 using the acceleration G2x and G2z values corrected by the second acceleration correction unit 32. To do. At this time, the inclination angle calculation unit 33 calculates the total value θ1 + θ2 using the following formula (19) or formula (20).
θ1 + θ2 = sin ⁻¹ (−G2x / g) (19)
θ1 + θ2 = cos ⁻¹ (−G2z / g) (20)

  In general, when the vehicle A is stopped, the road surface gradient angle θ1 is constant without changing. The inclination angle calculation unit 33 calculates the pitching angle θ2 by subtracting the value of the road surface gradient angle θ1, which is a constant value stored and calculated from the calculated total value θ1 + θ2 before stopping using a known method. The tilt angle calculation unit 33 outputs the calculated pitching angle θ2 to the optical axis adjustment device 12.

  The optical axis adjustment device 12 adjusts the optical axis angle of the headlight with respect to the road surface B using the value of the pitching angle θ2 output from the inclination angle calculation unit 33. Thereby, the optical axis angle of the headlight with respect to the road surface B can be maintained at a constant angle regardless of the passenger boarding the vehicle A and loading the luggage.

Next, the effect of correction using the primary correction formula and the secondary correction formula will be described with reference to the characteristic diagrams of FIGS.
FIG. 5A is a characteristic diagram showing the detection sensitivity of the acceleration detector 21 with respect to temperature. The acceleration detection unit 21 is in an ideal state because the input value and the output value are closer as the detection sensitivity value is closer to 1. However, as shown in FIG. 5A, the acceleration detector 21 has a characteristic that the detection sensitivity value gradually increases as the temperature increases. The detection sensitivity value increases from 1 as the temperature increases. .

  FIG. 5B is a characteristic diagram showing the detection sensitivity obtained by correcting the detection sensitivity shown in FIG. 5A by the primary correction formulas of the equations (5) and (6). The correction by the primary correction equation of the equations (5) and (6) is a straight line approximating a linear function between the detection sensitivity at the second temperature TL and the detection sensitivity at the first temperature TC shown in FIG. This is a correction to bring the value of D close to 1. As a result of the correction by the primary correction formula, the value of the detection sensitivity becomes approximately 1 over the temperature range from the second temperature TL to the first temperature TC as shown in FIG.

  FIG. 5C is a characteristic diagram showing the detection sensitivity obtained by correcting the detection sensitivity shown in FIG. 5B by the secondary correction formulas of the equations (9) and (10). The correction by the quadratic correction formulas of the equations (9) and (10) is a straight line approximating a linear function between the detection sensitivity at the first temperature TC and the detection sensitivity at the third temperature TH shown in FIG. This is a correction to bring the value of E close to 1. As a result of the correction by the secondary correction formula, as shown in FIG. 5C, the value of the detection sensitivity becomes approximately 1 over the temperature range from the first temperature TC to the third temperature TH. That is, as a result of the correction using the primary correction formula and the secondary correction formula, the value of the detection sensitivity is approximately 1 over the temperature range from the second temperature TL to the third temperature TH.

  In the tilt angle calculation apparatus 100 according to the first embodiment, first, the first characteristic value correction unit 22 corrects the detection sensitivities Sx and Sz using a primary correction formula. Next, the first acceleration correction unit 23 corrects the accelerations Gx and Gz detected by the acceleration detection unit 21 using the detection sensitivities S1x and S1z corrected by the first characteristic value correction unit 22. Next, when the detected temperature T of the temperature sensor 1 is equal to or higher than the first temperature TC, the second characteristic value correction unit 31 corrects the detection sensitivities Sx and Sz using a secondary correction formula. Next, the second acceleration correction unit 32 further corrects the accelerations G1x and G1z output by the first acceleration correction unit 23 using the detection sensitivities S1x and S1z corrected by the second characteristic value correction unit 31. As a result, the accelerations G2x and G2z finally used by the inclination angle calculation unit 33 to calculate the pitching angle θ2 are in a state in which the detection sensitivities Sx and Sz of the acceleration detection unit 21 are corrected to the detection sensitivities shown in FIG. It becomes a value equivalent to acceleration.

  Here, in the tilt angle calculation device 100, the first characteristic value correction unit 22 of the acceleration sensor 2 executes only correction using the primary correction formula. Further, the second characteristic value correction unit 31 of the microcomputer 3 corrects an error component that cannot be corrected using the primary correction formula, using the secondary correction formula. In general, in the in-vehicle inclination angle calculation device 100, the acceleration sensor 2 has a low processing capability in order to reduce the price, while the microcomputer 3 is higher than the acceleration sensor 2 in order to realize functions such as the inclination angle calculation unit 33. Has processing capacity. The configuration in which the microcomputer 3 performs the correction using the secondary correction formula reduces the processing load on the acceleration sensor 2 as compared to the configuration in which all the correction processes at three temperatures are performed in the sensor as in Patent Document 2. be able to. As a result, it is possible to correct the detection sensitivity with high accuracy by using an inexpensive acceleration sensor 2 having a low processing capability.

  FIG. 6A is a characteristic diagram showing an offset of the acceleration detector 21 with respect to temperature. The acceleration detection unit 21 is in an ideal state because the input value and the output value are closer as the offset value is closer to zero. However, as shown in FIG. 6A, the acceleration detector 21 has a characteristic that the offset value gradually increases as the temperature rises, and the offset value departs from 0 as the temperature rises.

  FIG. 6B is a characteristic diagram showing the offset obtained by correcting the offset shown in FIG. 6A by the primary correction formulas of the equations (7) and (8). FIG. 6C is a characteristic diagram showing the offset obtained by correcting the offset shown in FIG. 6B by the secondary correction formulas of the equations (11) and (12). The offset correction by the primary correction formula and the secondary correction formula is the same as the correction of the detection sensitivity shown in FIG. The tilt angle calculation apparatus 100 can correct the offset with high accuracy by using an inexpensive acceleration sensor 2 having a low processing capability.

  When the vehicle A is traveling at a constant speed, the inclination angle calculation unit 33 calculates a road surface gradient angle θ1 that is an inclination angle of the road surface B with respect to the horizontal plane C, instead of the pitching angle θ2. In general, when the vehicle A is traveling at a constant speed, the pitching angle θ2 is constant without changing. The inclination angle calculation unit 33 calculates the road surface gradient angle θ1 by subtracting a constant value of the pitching angle θ2 from the calculated value of the total inclination angle θ. The inclination angle calculation unit 33 outputs the calculated value of the road surface gradient angle θ1 to a navigation device and a posture control device (not shown) mounted on the vehicle A. The navigation device uses the value of the road surface gradient angle θ1 output from the inclination angle calculation unit 33 to correct the information indicating the turning angle and the current position of the vehicle A. The attitude control device uses the value of the road surface gradient angle θ1 output from the inclination angle calculation unit 33 to assist the vehicle A in starting the hill.

  The primary correction equation may be any one that corrects the characteristic value at the detected temperature T using the characteristic value at any two of the first temperature TC, the second temperature TL, and the third temperature TH. The formulas (5) to (8) are not limited. The secondary correction equation may be any equation that corrects an error component that cannot be corrected by the primary correction equation using characteristic values at a temperature different from that of the primary correction equation. Equations (9) to (12) ) Is not limited to.

  Further, the first temperature TC, the second temperature TL, and the third temperature TH are not limited to values indicating one temperature, respectively. A plurality of values may be set for the first temperature TC, the second temperature TL, and the third temperature TH, respectively. Alternatively, it may be a value indicating a temperature region having a predetermined width. In the first embodiment, the approximation by the primary correction equation and the quadratic correction equation has been described by the linear function approximation based on the characteristic values for two temperatures. However, the least square method is applied to the characteristic values for three or more temperatures. The approximation error can also be improved by using the coefficient determined by use.

  The microcomputer 3 may be composed of a plurality of microcomputers. For example, the second characteristic value correction unit 31 and the second acceleration correction unit 32 may be configured by a first microcomputer, and the tilt angle calculation unit 33 may be configured by a second microcomputer separate from the first microcomputer. . At least the second characteristic value correction unit 31 and the second acceleration correction unit 32 are configured by a microcomputer separate from the acceleration sensor 2 so that the characteristic value can be corrected with high accuracy using an inexpensive acceleration sensor 2 with low processing capability. can do.

  Further, the temperature sensor 1 may be configured by MEMS integrated with the acceleration sensor 2. Thereby, the temperature of the acceleration sensor 2 can be detected more accurately.

  The acceleration sensor 2 is not limited to a biaxial acceleration sensor. This is a three-axis acceleration sensor that detects a third-axis acceleration Gy along the left-right direction in addition to a first-axis acceleration Gx along the front-rear direction of the vehicle body of the vehicle A and a second-axis acceleration Gz along the up-down direction. May be. In this case, the first characteristic value correction unit 22 and the second characteristic value correction unit 31 correct the characteristic values in each of the three axes.

  In addition, the characteristic values corrected by the first characteristic value correction unit 22 and the second characteristic value correction unit 31 are not limited to detection sensitivity and offset as long as the values change with respect to temperature. The characteristic value to be corrected may be, for example, a value of an output delay time (so-called “delay characteristic”) with respect to the input of the acceleration detection unit 21. Alternatively, the acceleration detection unit 21 generally has a characteristic of an output value with respect to frequency (so-called “frequency characteristic”) similar to that of a low-pass filter, and may be a cutoff frequency value of the low-pass filter.

  In addition, the moving body on which the tilt angle calculation device 100 is mounted is not limited to the vehicle A. As long as the road surface gradient angle θ1 or the pitching angle θ2 is used for control, the vehicle may be mounted on any moving body including a vehicle, a railroad, an aircraft, or the like.

  As described above, the tilt angle calculation apparatus 100 according to the first embodiment is more than the temperature sensor 1 that detects temperature, the acceleration detection unit 21 that detects accelerations Gx and Gz, the first temperature TC, and the first temperature TC. At the detected temperature T of the temperature sensor 1 using the primary correction formula including the characteristic value of the acceleration detector 21 at any two of the lower second temperature TL and the third temperature TH higher than the first temperature TC. The acceleration sensor 2 having a first characteristic value correction unit 22 that corrects the characteristic value, and the acceleration sensor 2 are configured separately from the first temperature TC, the second temperature TL, and the third temperature TH. A second characteristic value correction unit 31 that corrects a characteristic value at the detected temperature T using a secondary correction expression including a characteristic value at a temperature different from the primary correction expression, a first characteristic value correction unit 22, and a second characteristic value correction Depending on the characteristic value corrected by the unit 31 Using the corrected acceleration G2x and G2z values, the inclination angle of the road surface B with respect to the horizontal plane C (road surface gradient angle θ1) or the inclination angle of the vehicle A equipped with the acceleration sensor 2 with respect to the road surface B (pitching angle θ2) is calculated. And an inclination angle calculation unit 33. The acceleration sensor 2 performs only the correction by the primary correction formula, and the correction by the secondary correction formula is executed outside the acceleration sensor 2, so that the characteristic value can be obtained with high accuracy by using an inexpensive acceleration sensor 2 having a low processing capability. Can be corrected. As a result, the calculation accuracy of the road surface gradient angle θ1 and the pitching angle θ2 can be improved.

  Further, the second characteristic value correction unit 31 is configured by a microcomputer 3 provided outside the acceleration sensor 2. In general, the microcomputer 3 of the tilt angle calculation apparatus 100 has a high processing capability in order to realize functions such as the tilt angle calculation unit 33. By providing the second characteristic value correction unit 31 in the microcomputer 3, it is possible to perform correction using a complicated secondary correction equation.

  Further, the value of the second temperature TL is set to the lower limit value of the operation guarantee temperature of the acceleration sensor 2, and the value of the third temperature TH is set to the upper limit value of the operation guarantee temperature of the acceleration sensor 2. As a result, the characteristic value of the acceleration detector 21 can be corrected over almost the entire guaranteed operating temperature of the acceleration sensor 2.

  In general, the measurement of the characteristic value at the second temperature TL is performed in a closed low-temperature bath. When the inspection object is exchanged, moisture in the air flows into the low-temperature tank due to opening and closing of the low-temperature tank, and condensation occurs in the tank, so that equipment maintenance time is required every certain number of times of opening and closing. For this reason, when the number of objects that can be measured by one opening and closing is small, the ratio of maintenance cost per piece increases. In the state of the acceleration sensor 2 alone, the size is small and the number of characteristic values that can be measured in the low-temperature chamber is large. However, in the state where the tilt angle calculation device 100 is assembled, the size is large and the characteristic value is measured once in the low-temperature chamber. The number that can be measured is limited. The primary correction formula includes the characteristic values at the first temperature TC and the second temperature TL, and the secondary correction formula includes the characteristic values at the first temperature TC and the third temperature TH. Measurement can be performed in the state of the acceleration sensor 2 alone. As a result, by increasing the number of characteristic values that can be measured at a time, the number of maintenance can be reduced, and the manufacturing cost of the tilt angle calculation apparatus 100 can be reduced.

  The characteristic value is at least one of the offset, detection sensitivity, delay characteristic, and cutoff frequency of the acceleration detection unit 21. As long as the characteristic value changes with respect to the temperature, the calculation accuracy of the road surface gradient angle θ1 and the pitching angle θ2 can be improved no matter what characteristic value is corrected.

  The temperature sensor 1 is configured integrally with the acceleration sensor 2. Thereby, the temperature of the acceleration sensor 2 can be detected more accurately.

  Further, the primary correction formula is a formula that approximates the value of the straight line D obtained by approximating the characteristic values at two temperatures with a linear function to a constant value. As a result, the first characteristic value correction unit 22 can correct the characteristic value using a simple linear correction equation of a linear function, and can further reduce the processing load of the acceleration sensor 2.

Embodiment 2. FIG.
In the second embodiment, an inclination angle calculating apparatus 100 in which a secondary correction formula different from that in the first embodiment is set will be described. Note that the hardware configuration and the main part of the tilt angle calculation apparatus 100 according to the second embodiment are the same as those in the first embodiment, and therefore will be described with reference to FIGS. 1 and 2. The operations of the first characteristic value correction unit 22 and the first acceleration correction unit 23 are the same as those in the first embodiment, and will be described with reference to FIG.

First, the secondary correction formula will be described.
The manufacturer of the tilt angle calculation device 100 assembles the tilt angle calculation device 100 by mounting the temperature sensor 1, the acceleration sensor 2, and the microcomputer 3 on the electronic circuit board. Next, the manufacturer of the tilt angle calculation device 100 measures the characteristic value of the acceleration detection unit 21. Specifically, the detection sensitivities SCx and SCz and the offsets OCx and OCz at the first temperature TC are measured. Further, the tilt angle calculation device 100 is placed in a high temperature bath, and the detection sensitivities SHx and SHz and the offsets OHx and OHz at the third temperature TH are measured.

The manufacturer of the tilt angle calculation device 100 stores the values of the first temperature TC, the second temperature TL, the third temperature TH, the detection sensitivities SCx, SCz, SHx, SHz and the offsets OCx, OCz, OHx, OHz in the microcomputer 3. Store in the department. Further, the manufacturer of the tilt angle calculation apparatus 100 sets the following formulas (21) to (24) in the microcomputer 3 as secondary correction formulas. Expressions (21) to (24) are expressions expressed as quadratic functions of temperature T.
S2x = SCx + (T−TL) × (T−TC) / (TH−TL)
/ (TH-TC) × (SHx-SCx) (21)
S2z = SCz + (T−TL) × (T−TC) / (TH−TL)
/ (TH-TC) × (SHz-SCz) (22)
O2x = OCx + (T-TL) * (T-TC) / (TH-TL)
/ (TH-TC) × (OHx-OCx) (23)
O2z = OCz + (T−TL) × (T−TC) / (TH−TL)
/ (TH-TC) × (OHz-OCz) (24)

  Next, operations of the second characteristic value correction unit 31 and the second acceleration correction unit 32 will be described with reference to the flowchart of FIG. In FIG. 7, the same steps as those in the flowchart of the first embodiment shown in FIG.

  First, the second characteristic value correction unit 31 and the second acceleration correction unit 32 execute the processes of steps ST11 and ST12 similar to those in the first embodiment.

  Next, in step ST21, the second characteristic value correction unit 31 corrects the detection sensitivity Sx at the detection temperature T using the secondary correction formula of Formula (21). Similarly, in step ST22, the second characteristic value correction unit 31 corrects the detection sensitivity Sz at the detection temperature T using the secondary correction formula of Formula (22). In step ST23, the second characteristic value correction unit 31 corrects the offset Ox at the detected temperature T using the secondary correction formula of Formula (23). In step ST24, the second characteristic value correction unit 31 corrects the offset Oz at the detected temperature T using the secondary correction formula of Formula (24).

  Next, the second acceleration correction unit 32 executes the process of step ST18 similar to that of the first embodiment.

Next, the effect of correction using the primary correction formula and the secondary correction formula will be described with reference to the characteristic diagrams of FIGS.
FIG. 8A is a characteristic diagram showing the detection sensitivity of the acceleration detector 21 with respect to temperature. FIG. 8B is a characteristic diagram showing the detection sensitivity obtained by correcting the detection sensitivity shown in FIG. 8A by the primary correction formulas of the equations (5) and (6). As described in the first embodiment, the correction using the primary correction formulas of the formulas (5) and (6) is a correction that brings the value of the straight line D closer to 1.

  FIG. 8C is a characteristic diagram showing the detection sensitivity obtained by correcting the detection sensitivity shown in FIG. 8B by the secondary correction equations of the equations (21) and (22). The correction based on the quadratic correction formulas of Expression (21) and Expression (22) is correction that brings the value of the curve F of the quadratic function along the detection sensitivity characteristic line shown in FIG. As a result of the correction by the primary correction formula and the secondary correction formula, the value of the detection sensitivity becomes approximately 1 over the temperature range from the second temperature TL to the third temperature TH as shown in FIG.

  FIG. 9A is a characteristic diagram showing an offset of the acceleration detector 21 with respect to temperature. FIG. 9B is a characteristic diagram showing the offset obtained by correcting the offset shown in FIG. 9A by the primary correction formulas of Expressions (7) and (8). FIG. 9C is a characteristic diagram showing the offset obtained by correcting the offset shown in FIG. 9B by the secondary correction formulas of the equations (23) and (24). The offset characteristics shown in FIG. 9 are the same as the detection sensitivity characteristics shown in FIG.

  The characteristic lines shown in FIGS. 8C and 9C are closer to 1 than the characteristic lines shown in FIGS. 5C and 6C. That is, by using the quadratic correction equation of the quadratic function shown in equations (21) to (24), the characteristic value can be corrected with higher accuracy than the configuration using the quadratic correction equation of the linear function. it can.

  As described above, the tilt angle calculation apparatus 100 according to the second embodiment has the first temperature value TC, the first temperature characteristic value XC, the second temperature value TL, and the second temperature characteristic value XL. The third temperature value is TH, the characteristic value at the third temperature is XH, the detected temperature value is T, the characteristic value after correction by the first characteristic value correction unit 22 is X1, and the correction by the second characteristic value correction unit 31 Assuming that the subsequent characteristic value is X2, the primary correction formula is the formula X1 = XC + (XL−XC) × (T−TC) / (TL−TC), and the secondary correction formula is the formula X2 = XC + (T−TL). ) * (T-TC) / (TH-TL) / (TH-TC) * (XH-XC). By using the quadratic correction equation of the quadratic function shown in equations (21) to (24), the characteristic value can be corrected with higher accuracy than the configuration using the quadratic correction equation of the linear function.

Embodiment 3 FIG.
In the third embodiment, the same primary correction equation and secondary correction equation as in the second embodiment are set, and the inclination angle calculation device 100 that specifies the values of the first temperature TC, the second temperature TL, and the third temperature TH is specified. Will be described. Note that the hardware configuration and the main part of the tilt angle calculation apparatus 100 according to the third embodiment are the same as those in the first embodiment, and therefore will be described with reference to FIGS. 1 and 2.

  In the acceleration sensor 2, the same equations (5) to (8) as in the second embodiment are set as the primary correction equations. In the microcomputer 3, the same equations (21) to (24) as in the second embodiment are set as secondary correction equations.

In the inclination angle calculation device 100 of the third embodiment, the value of the first temperature TC is set to 24 ° C., the value of the second temperature TL is −40 ° C., and the value of the third temperature TH is set to 88 ° C. Equations (5) to (8), which are primary correction equations, are expressed by the following equations (25) to (28) when the values of the first temperature TC, the second temperature TL, and the third temperature TH are substituted. Is done.
S1x = SCx + (SLx−SCx) × (T−24) / 64 (25)
S1z = SCz + (SLz−SCz) × (T−24) / 64 (26)
O1x = OCx + (OLx−OCx) × (T−24) / 64 (27)
O1z = OCz + (OLz−OCz) × (T−24) / 64 (28)

Similarly, equations (21) to (24), which are secondary correction equations, are substituted into the following equations (29) to (32) when the values of the first temperature TC, the second temperature TL, and the third temperature TH are substituted. ).
S2x = SCx + (T + 40) × (T−24) / 128/64
× (SHx-SCx) (29)
S2z = SCz + (T + 40) × (T−24) / 128/64
× (SHz-SCz) (30)
O2x = OCx + (T + 40) × (T−24) / 128/64
× (OHx-OCx) (31)
O2z = OCz + (T + 40) × (T−24) / 128/64
× (OHz-OCz) (32)

  Next, operations of the first characteristic value correction unit 22 and the first acceleration correction unit 23 will be described with reference to the flowchart of FIG. In FIG. 10, the same steps as those in the flowchart of the first embodiment shown in FIG.

  First, the first characteristic value correction unit 22 and the first acceleration correction unit 23 execute the processes of steps ST1 and ST2 similar to those in the first embodiment.

Next, in step ST31, the first characteristic value correction unit 22 corrects the detection sensitivity Sx at the detection temperature T using the primary correction formula of Formula (25). At this time, the first characteristic value correction unit 22 calculates Expression (25) by sequentially calculating Expressions (25a) to (25c) below.
S′x = (SLx−SCx) × (T−24) (25a)
S ″ x = bitshift (S′x, −6) (25b)
S1x = SCx + S ″ x (25c)

Similarly, in step ST32, the first characteristic value correction unit 22 corrects the detection sensitivity Sz at the detection temperature T using the primary correction formula of Formula (26). At this time, the first characteristic value correction unit 22 calculates Expression (26) by sequentially calculating Expressions (26a) to (26c) below.
S′z = (SLz−SCz) × (T−24) (26a)
S ″ z = bitshift (S′z, −6) (26b)
S1z = SCz + S ″ z (26c)

In Step ST33, the first characteristic value correction unit 22 corrects the offset Ox at the detected temperature T using the primary correction formula of Formula (27). At this time, the first characteristic value correction unit 22 calculates Expression (27) by sequentially calculating Expressions (27a) to (27c) below.
O′x = (OLx−OCx) × (T−24) (27a)
O ″ x = bitshift (O′x, −6) (27b)
O1x = OCx + O ″ x (27c)

In step ST <b> 34, the first characteristic value correction unit 22 corrects the offset Oz at the detected temperature T using the primary correction formula of Formula (28). At this time, the first characteristic value correction unit 22 calculates Expression (28) by sequentially calculating Expressions (28a) to (28c) below.
O′z = (OLz−OCz) × (T−24) (28a)
O ″ z = bitshift (O′z, −6) (28b)
O1z = OCz + O ″ z (28c)

  Next, the first acceleration correction unit 23 executes the process of step ST7 similar to that of the first embodiment.

  In all of Expressions (25) to (28), the denominator is 2 to the Nth power (N is a natural number). For this reason, the first characteristic value correction unit 22 includes the expressions (25a) to (25c), the expressions (26a) to (26c), the expressions (27a) to (27c), and the expressions (28a) to (28c). As shown in (), Expression (25) to Expression (28) can be calculated using bit shift. That is, the first characteristic value correction unit 22 does not require division and can further reduce the processing load on the acceleration sensor 2.

  Next, operations of the second characteristic value correction unit 31 and the second acceleration correction unit 32 will be described with reference to the flowchart of FIG. In FIG. 11, the same steps as those in the flowchart of the first embodiment shown in FIG.

  First, the second characteristic value correction unit 31 and the second acceleration correction unit 32 execute the processes of steps ST11 and ST12 similar to those in the first embodiment.

Next, in step ST41, the second characteristic value correction unit 31 corrects the detection sensitivity Sx at the detection temperature T using the secondary correction formula of Formula (29). At this time, the second characteristic value correction unit 31 calculates Expression (29) by sequentially calculating Expressions (29a) to (29c) below.
S′x = (T + 40) × (T−24) × (SHx−SCx) (29a)
S ″ x = bitshift (S′x, −13) (29b)
S2x = SCx + S ″ x (29c)

Similarly, in step ST42, the second characteristic value correction unit 31 corrects the detection sensitivity Sz at the detection temperature T using the secondary correction formula of Formula (30). At this time, the second characteristic value correction unit 31 calculates Expression (30) by sequentially calculating Expressions (30a) to (30c) below.
S′z = (T + 40) × (T−24) × (SHz−SCz) (30a)
S ″ z = bitshift (S′z, −13) (30b)
S2z = SCz + S ″ z (30c)

In Step ST43, the second characteristic value correction unit 31 corrects the offset Ox at the detected temperature T using the secondary correction formula of Formula (31). At this time, the 2nd characteristic value correction | amendment part 31 calculates Formula (31) by calculating sequentially the following formula | equation (31a)-Formula (31c).
O′x = (T + 40) × (T−24) × (OHx−OCx) (31a)
O ″ x = bitshift (O′x, −13) (31b)
O2x = OCx + O ″ x (31c)

In step ST44, the second characteristic value correction unit 31 corrects the offset Oz at the detected temperature T using the primary correction formula of the formula (32). At this time, the second characteristic value correcting unit 31 calculates the expression (32) by sequentially calculating the following expressions (32a) to (32c).
O′z = (T + 40) × (T−24) × (OHz−OCz) (32a)
O ″ z = bitshift (O′z, −13) (32b)
O2z = OCz + O ″ z (32c)

  Next, the second acceleration correction unit 32 executes the process of step ST18 similar to that of the first embodiment.

  In all of the equations (29) to (32), the denominator is 2 to the Nth power (N is a natural number). For this reason, the second characteristic value correction unit 31 includes the expressions (29a) to (29c), the expressions (30a) to (30c), the expressions (31a) to (31c), and the expressions (32a) to (32c). (29) to (32) can be calculated using bit shift. That is, the second characteristic value correction unit 31 does not require division and can reduce the processing load on the microcomputer 3.

  As described above, the tilt angle calculation apparatus 100 according to the third embodiment sets the value of the first temperature TC to 24 degrees Celsius, sets the value of the second temperature TL to minus 40 degrees Celsius, and sets the third temperature TH. The value of is set to 88 degrees Celsius. As a result, the first characteristic value correction unit 22 does not require division and can further reduce the processing load of the acceleration sensor 2. Further, the second characteristic value correction unit 31 also does not require division, and the processing load on the microcomputer 3 can be reduced.

Embodiment 4 FIG.
In the fourth embodiment, an inclination angle calculating apparatus 100 in which a primary correction equation and a secondary correction equation different from those of the first to third embodiments are described. Note that the hardware configuration and main parts of the tilt angle calculation apparatus 100 according to the fourth embodiment are the same as those in the first embodiment, and thus will be described with reference to FIGS. 1 and 2.

First, the primary correction formula will be described.
The manufacturer of the acceleration sensor 2 measures the characteristic value of the acceleration detector 21 after manufacturing the acceleration sensor 2. Specifically, the acceleration sensor 2 is placed in a low temperature bath, and the detection sensitivities SLx and SLz and the offsets OLx and OLz at the second temperature TL are measured. Further, the acceleration sensor 2 is placed in a high temperature bath, and the detection sensitivities SHx and SHz and the offsets OHx and OHz at the third temperature TH are measured.

The manufacturer of the acceleration sensor 2 stores the values of the second temperature TL, the third temperature TH, the detection sensitivities SLx, SLz, SHx, SHz and the offsets OLx, OLz, OHx, OHz in the storage unit of the acceleration sensor 2. The manufacturer of the acceleration sensor 2 sets the following equations (33) to (36) in the acceleration sensor 2 as primary correction equations. Expressions (33) to (36) are expressions expressed as linear functions of the temperature T.
S1x = SHx + (SLx−SHx) × (T−TH) / (TL−TH) (33)
S1z = SHz + (SLz−SHz) × (T−TH) / (TL−TH) (34)
O1x = OHx + (OLx−OHx) × (T−TH) / (TL−TH) (35)
O1z = OHz + (OLz−OHz) × (T−TH) / (TL−TH) (36)

Next, the secondary correction formula will be described.
The manufacturer of the tilt angle calculation device 100 sets a target value for the characteristic value of the acceleration detector 21. For example, the target values SOx and SOz of the detection sensitivities Sx and Sz are 1, and the target values OOx and OOz of the offsets Ox and Oz are 0.

  The manufacturer of the tilt angle calculation device 100 assembles the tilt angle calculation device 100 by mounting the temperature sensor 1, the acceleration sensor 2, and the microcomputer 3 on the electronic circuit board. Next, the manufacturer of the tilt angle calculation device 100 measures the characteristic value of the acceleration detection unit 21. Specifically, the detection sensitivities SCx and SCz and the offsets OCx and OCz at the first temperature TC are measured.

The manufacturer of the tilt angle calculation apparatus 100 determines the values of the target values SOx, SOz, OOx, OOz, the first temperature TC, the second temperature TL, the third temperature TH, the detection sensitivities SCx, SCz, and the offsets OCx, OCz. Is stored in the storage unit. Further, the manufacturer of the tilt angle calculation apparatus 100 sets the following formulas (37) to (40) in the microcomputer 3 as secondary correction formulas. Expressions (37) to (40) are expressions expressed as linear functions of temperature T.
S2x = SOx + (SCx−SOx) × (T−TH) / (TC−TH) (37)
S2z = SOz + (SCz−SOz) × (T−TH) / (TC−TH) (38)
O2x = OOx + (OCx−OOx) × (T−TH) / (TC−TH) (39)
O2z = OOz + (OCz-OOz) * (T-TH) / (TC-TH) (40)

Furthermore, the manufacturer of the tilt angle calculation apparatus 100 sets the following formulas (41) to (44) in the microcomputer 3 as secondary correction formulas. Expressions (41) to (44) are expressions expressed as linear functions of the temperature T.
S2x = SOx + (SCx−SOx) × (T−TL) / (TC−TL) (41)
S2z = SOz + (SCz−SOz) × (T−TL) / (TC−TL) (42)
O2x = OOx + (OCx-OOx) * (T-TL) / (TC-TL) (43)
O2z = OOz + (OCz−OOz) × (T−TL) / (TC−TL) (44)

  Next, operations of the first characteristic value correction unit 22 and the first acceleration correction unit 23 will be described with reference to the flowchart of FIG. In FIG. 12, the same steps as those in the flowchart of the first embodiment shown in FIG.

  First, the first characteristic value correction unit 22 and the first acceleration correction unit 23 execute the processes of steps ST1 and ST2 similar to those in the first embodiment.

  Next, in step ST51, the first characteristic value correction unit 22 corrects the detection sensitivity Sx at the detection temperature T using the primary correction formula of Formula (33). Similarly, in step ST52, the first characteristic value correction unit 22 corrects the detection sensitivity Sz at the detection temperature T using the primary correction equation of equation (34). In step ST53, the first characteristic value correction unit 22 corrects the offset Ox at the detected temperature T using the primary correction formula of Formula (35). In step ST54, the first characteristic value correction unit 22 corrects the offset Oz at the detected temperature T using the primary correction formula of Formula (36).

  Next, the first acceleration correction unit 23 executes the process of step ST7 similar to that of the first embodiment.

  Next, operations of the second characteristic value correction unit 31 and the second acceleration correction unit 32 will be described with reference to the flowchart of FIG. In FIG. 13, the same steps as those in the flowchart of the first embodiment shown in FIG.

  First, the second characteristic value correction unit 31 and the second acceleration correction unit 32 execute the processes of steps ST11 to ST13 similar to those in the first embodiment.

  When the detected temperature T is equal to or higher than the first temperature TC (step ST13 “NO”), in step ST61, the second characteristic value correction unit 31 uses the secondary correction formula of formula (37) to detect the detected temperature T. The detection sensitivity Sx is corrected. Similarly, in step ST62, the second characteristic value correction unit 31 corrects the detection sensitivity Sz at the detection temperature T using the secondary correction formula of Formula (38). In step ST63, the second characteristic value correction unit 31 corrects the offset Ox at the detected temperature T using the secondary correction formula of Formula (39). In step ST64, the second characteristic value correction unit 31 corrects the offset Oz at the detected temperature T using the secondary correction formula of Formula (40).

  On the other hand, when the detected temperature T is lower than the first temperature TC (step ST13 “YES”), in step ST65, the second characteristic value correction unit 31 detects using the secondary correction formula of the formula (41). The detection sensitivity Sx at the temperature T is corrected. Similarly, in Step ST66, the second characteristic value correction unit 31 corrects the detection sensitivity Sz at the detection temperature T using the secondary correction formula of Formula (42). In step ST67, the second characteristic value correction unit 31 corrects the offset Ox at the detected temperature T using the secondary correction formula of Formula (43). In step ST68, the second characteristic value correction unit 31 corrects the offset Oz at the detected temperature T using the secondary correction formula of Formula (44).

  Subsequent to step ST64 or step ST68, the second acceleration correction unit 32 executes the process of step ST18 similar to that of the first embodiment.

Next, the effect of correction using the primary correction formula and the secondary correction formula will be described with reference to the characteristic diagrams of FIGS.
FIG. 14A is a characteristic diagram showing the detection sensitivity of the acceleration detector 21 with respect to temperature. FIG. 14B is a characteristic diagram showing the detection sensitivity obtained by correcting the detection sensitivity shown in FIG. 14A by the primary correction formulas of the equations (33) and (34). The correction using the linear correction formulas of Expression (33) and Expression (34) is a straight line approximating a linear function between the detection sensitivity at the second temperature TL and the detection sensitivity at the third temperature TH shown in FIG. This is a correction to bring the value of G closer to the target value of 1.

  FIG. 14 (c) shows a detection in which the detection sensitivity shown in FIG. 14 (b) is corrected by the secondary correction formula of formula (37) and formula (38) or the secondary correction formula of formula (41) and formula (42). It is a characteristic view which shows a sensitivity. The correction by the quadratic correction formulas of Expression (37) and Expression (38) is a straight line that approximates the detection sensitivity at the second temperature TL and the detection sensitivity at the first temperature TC with a linear function shown in FIG. This is a correction that brings the value of H close to the target value of 1. On the other hand, the correction by the quadratic correction formulas of the equations (41) and (42) is approximated by a linear function between the detection sensitivity at the first temperature TC and the detection sensitivity at the third temperature TH shown in FIG. This is a correction to bring the value of the straight line I close to the target value of 1. That is, the correction based on the secondary correction expressions of Expressions (37) to (44) is a polygonal line correction that brings the values of the two straight lines H and I crossing each other closer to 1. As a result of the correction using the primary correction formula and the secondary correction formula, the value of the detection sensitivity becomes equal to the target value of 1 over the temperature range from the second temperature TL to the third temperature TH.

  FIG. 15A is a characteristic diagram showing an offset of the acceleration detector 21 with respect to temperature. FIG. 15B is a characteristic diagram showing an offset obtained by correcting the offset shown in FIG. 15A by the primary correction formulas of Expressions (35) and (36). FIG. 15C shows an offset obtained by correcting the offset shown in FIG. 15B by the secondary correction expression of Expression (39) and Expression (40) or the secondary correction expression of Expression (43) and Expression (44). FIG. The offset characteristics shown in FIG. 15 are the same as the detection sensitivity characteristics shown in FIG.

  As described above, the tilt angle calculation apparatus 100 according to the fourth embodiment has the first temperature value TC, the first temperature characteristic value XC, the second temperature value TL, and the second temperature characteristic value XL. The primary correction equation is expressed as X1 = TH, the third temperature value is TH, the third temperature characteristic value is XH, the detected temperature value is T, and the characteristic value after correction by the first characteristic value correction unit 22 is X1. XH + (XL-XH) * (T-TH) / (TL-TH). As in the first embodiment, by including the characteristic value at the second temperature TL in the primary correction formula, the measurement of the characteristic value in the low temperature bath can be performed by the acceleration sensor 2 alone, and the inclination angle calculating device The manufacturing cost of 100 can be reduced. Further, since the primary correction formula is a formula expressed as a linear function of temperature, the first characteristic value correction unit 22 can execute the correction processing with a simple calculation, and the processing load on the acceleration sensor 2 is reduced. can do.

  Further, assuming that the characteristic value after correction by the second characteristic value correction unit 31 is X2 and the target value of the characteristic value is XO, the secondary correction equation is expressed as X2 = XO + when the detected temperature T is equal to or higher than the first temperature TC. When (XC−XO) × (T−TH) / (TC−TH) and the detected temperature T is lower than the first temperature TC, the formula X2 = XO + (XC−XO) × (T−TL) / ( TC-TL). As a result, the second characteristic value correction unit 31 can correct the characteristic value by simple polygonal line correction, and can reduce the processing load on the microcomputer 3 while correcting the characteristic value with high accuracy.

  Further, the target values of the characteristic values are 1 for the detection values Sox and Sz of the detection sensitivity Sx and Sz of the acceleration detection unit 21 and 0 for the target values OOx and OOz of the offsets Ox and Oz of the acceleration detection unit 21. By setting the target values SOx and SOz of the detection sensitivities Sx and Sz to 1, the corrected detection sensitivities S2x and S2z can be made close to 1, and the output value of the acceleration detector 21 can be made equal to the input value. it can. Further, by setting the target values OOx and OOz of the offsets Ox and Oz to 0, the corrected values of the offsets O2x and O2z can be brought close to 0 and the output value of the acceleration detector 21 can be made equal to the input value. it can.

Embodiment 5. FIG.
In the fifth embodiment, an inclination angle calculating apparatus 100 in which a secondary correction formula different from that of the fourth embodiment is set will be described. Note that the hardware configuration and the main part of the tilt angle calculation apparatus 100 according to the fifth embodiment are the same as those in the first embodiment, and therefore will be described with reference to FIGS. 1 and 2. The operations of the first characteristic value correction unit 22 and the first acceleration correction unit 23 are the same as those in the fourth embodiment, and therefore will be described with reference to FIG.

First, the secondary correction formula will be described.
The manufacturer of the tilt angle calculation device 100 sets a target value for the characteristic value of the acceleration detector 21. For example, the target values SOx and SOz of the detection sensitivities Sx and Sz are 1, and the target values OOx and OOz of the offsets Ox and Oz are 0.

  The manufacturer of the tilt angle calculation device 100 assembles the tilt angle calculation device 100 by mounting the temperature sensor 1, the acceleration sensor 2, and the microcomputer 3 on the electronic circuit board. Next, the manufacturer of the tilt angle calculation device 100 measures the characteristic value of the acceleration detection unit 21. Specifically, the detection sensitivities SCx and SCz and the offsets OCx and OCz at the first temperature TC are measured.

The manufacturer of the tilt angle calculation apparatus 100 determines the values of the target values SOx, SOz, OOx, OOz, the first temperature TC, the second temperature TL, the third temperature TH, the detection sensitivities SCx, SCz, and the offsets OCx, OCz. Is stored in the storage unit. Further, the manufacturer of the tilt angle calculation apparatus 100 sets the following formulas (45) to (48) in the microcomputer 3 as secondary correction formulas. Expressions (45) to (48) are expressions expressed as linear functions of the temperature T.
S2x = SOx + (SCx−SOx) × (T−TL) × (T−TH)
/ (TC-TL) / (TC-TH) (45)
S2z = SOz + (SCz−SOz) × (T−TL) × (T−TH)
/ (TC-TL) / (TC-TH) (46)
O2x = OOx + (OCx−OOx) × (T−TL) × (T−TH)
/ (TC-TL) / (TC-TH) (47)
O2z = OOz + (OCz−OOz) × (T−TL) × (T−TH)
/ (TC-TL) / (TC-TH) (48)

  Next, operations of the second characteristic value correction unit 31 and the second acceleration correction unit 32 will be described with reference to the flowchart of FIG. In FIG. 16, the same steps as those in the flowchart of the fourth embodiment shown in FIG.

  First, the second characteristic value correction unit 31 and the second acceleration correction unit 32 execute the processes of steps ST11 and ST12 similar to those in the fourth embodiment.

  Next, in step ST71, the second characteristic value correction unit 31 corrects the detection sensitivity Sx at the detection temperature T using the secondary correction formula of Formula (45). Similarly, in step ST72, the second characteristic value correction unit 31 corrects the detection sensitivity Sz at the detection temperature T using the secondary correction formula of Formula (46). In step ST73, the second characteristic value correction unit 31 corrects the offset Ox at the detected temperature T using the secondary correction formula of Formula (47). In step ST74, the second characteristic value correction unit 31 corrects the offset Oz at the detected temperature T using the secondary correction formula of Formula (48).

  Next, the second acceleration correction unit 32 executes the process of step ST18 similar to that of the fourth embodiment.

Next, the effect of correction using the primary correction formula and the secondary correction formula will be described with reference to the characteristic diagrams of FIGS.
FIG. 17A is a characteristic diagram showing the detection sensitivity of the acceleration detector 21 with respect to temperature. FIG. 17B is a characteristic diagram showing the detection sensitivity obtained by correcting the detection sensitivity shown in FIG. 17A by the primary correction formulas of the equations (33) and (34). As described in the fourth embodiment, the correction using the primary correction formulas of Expression (33) and Expression (34) is correction that brings the value of the straight line G closer to the target value of 1.

  FIG. 17C is a characteristic diagram showing the detection sensitivity obtained by correcting the detection sensitivity shown in FIG. 17B by the secondary correction formulas of the equations (45) and (46). The correction by the quadratic correction formulas of the equations (45) and (46) is a correction in which the value of the curve J of the quadratic function along the detection sensitivity characteristic line shown in FIG. It is. As a result of correction by the primary correction formula and the secondary correction formula, as shown in FIG. 17C, the value of the detection sensitivity is equal to 1 which is the target value over the temperature range from the second temperature TL to the third temperature TH. Value.

  FIG. 18A is a characteristic diagram showing an offset of the acceleration detector 21 with respect to temperature. FIG. 18B is a characteristic diagram showing an offset obtained by correcting the offset shown in FIG. 18A by the primary correction formulas of Expression (35) and Expression (36). FIG. 18C is a characteristic diagram showing the offset obtained by correcting the offset shown in FIG. 18B by the secondary correction formulas of the equations (47) and (48). The offset characteristics shown in FIG. 18 are the same as the detection sensitivity characteristics shown in FIG.

  The characteristic lines shown in FIGS. 17 (c) and 18 (c) are closer to 1 than the characteristic lines shown in FIGS. 14 (c) and 15 (c). That is, by using the quadratic correction equation of the quadratic function shown in the equations (45) to (48), the characteristic value can be corrected with higher accuracy than the configuration using the quadratic correction equation of the linear function. it can.

  As described above, the tilt angle calculation apparatus 100 according to the fifth embodiment has the characteristic value after correction by the second characteristic value correction unit 31 as X2 and the target value of the characteristic value as XO, and the secondary correction equation is expressed as X2 = XO + (XC-XO) * (T-TL) * (T-TH) / (TC-TL) / (TC-TH). By using the quadratic correction equation of the quadratic function shown in equations (45) to (48), the characteristic value can be corrected with higher accuracy than the configuration using the quadratic correction equation of the linear function.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  DESCRIPTION OF SYMBOLS 1 Temperature sensor, 2 Acceleration sensor, 3 Microcomputer, 10 Wheel speed sensor, 11 ECU, 12 Optical axis adjustment apparatus, 21 Acceleration detection part, 22 1st characteristic value correction part, 23 1st acceleration correction part, 31 2nd characteristic value Correction part, 32 2nd acceleration correction part, 33 Inclination angle calculation part, 100 Inclination angle calculation apparatus.

Claims (14)

A temperature sensor for detecting the temperature;
An acceleration detection unit that detects acceleration, and a characteristic value of the acceleration detection unit at any one of a first temperature, a second temperature lower than the first temperature, and a third temperature higher than the first temperature An acceleration sensor having a first characteristic value correction unit that corrects the characteristic value at a temperature detected by the temperature sensor using a primary correction formula including:
It is comprised separately from the said acceleration sensor, Using the secondary correction formula containing the said characteristic value in the temperature different from the said primary correction formula among the said 1st temperature, the said 2nd temperature, and the said 3rd temperature. A second characteristic value correction unit for correcting the characteristic value at the detected temperature;
Using the acceleration value corrected by the characteristic value corrected by the first characteristic value correction unit and the second characteristic value correction unit, the inclination angle of the road surface with respect to a horizontal plane or the movement provided with the acceleration sensor with respect to the road surface An inclination angle calculation unit for calculating an inclination angle of the body;
An inclination angle calculation device comprising:   The tilt angle calculation apparatus according to claim 1, wherein the second characteristic value correction unit is configured by a microcontroller provided outside the acceleration sensor. The value of the second temperature is set to a lower limit value of the operation guarantee temperature of the acceleration sensor,
The inclination angle calculation device according to claim 1, wherein the value of the third temperature is set to an upper limit value of an operation guarantee temperature of the acceleration sensor.   The inclination angle calculation apparatus according to claim 1, wherein the secondary correction formula includes the characteristic values at two of the first temperature, the second temperature, and the third temperature. The primary correction formula includes the characteristic values at the first temperature and the second temperature,
The inclination angle calculation device according to claim 4, wherein the secondary correction formula includes the characteristic values at the first temperature and the third temperature.   The tilt angle calculation apparatus according to claim 1, wherein the characteristic value is at least one of an offset, detection sensitivity, delay characteristic, and cutoff frequency of the acceleration detection unit.   The tilt angle calculation apparatus according to claim 1, wherein the temperature sensor is configured integrally with the acceleration sensor.   2. The tilt angle calculation apparatus according to claim 1, wherein the primary correction expression is an expression that approximates a value of a straight line obtained by approximating the characteristic values at two temperatures by a least square method to a constant value. The value of the first temperature is TC, the characteristic value at the first temperature is XC,
The value of the second temperature is TL, the characteristic value at the second temperature is XL,
The value of the third temperature is TH, the characteristic value at the third temperature is XH,
The detected temperature value is T,
The characteristic value after correction by the first characteristic value correction unit is X1,
The characteristic value after correction by the second characteristic value correction unit is X2,
The primary correction formula is the formula X1 = XC + (XL−XC) × (T−TC) / (TL−TC),
The secondary correction formula is the formula X2 = XC + (T−TL) × (T−TC) / (TH−TL) / (TH−TC) × (XH−XC). Inclination angle calculation device.   The first temperature value is set to 24 degrees Celsius, the second temperature value is set to minus 40 degrees Celsius, and the third temperature value is set to 88 degrees Celsius. Item 10. The tilt angle calculation device according to Item 9. The value of the first temperature is TC, the characteristic value at the first temperature is XC,
The value of the second temperature is TL, the characteristic value at the second temperature is XL,
The value of the third temperature is TH, the characteristic value at the third temperature is XH,
The detected temperature value is T,
The characteristic value after correction by the first characteristic value correction unit is X1,
The tilt angle calculation apparatus according to claim 1, wherein the primary correction formula is formula X1 = XH + (XL−XH) × (T−TH) / (TL−TH). The characteristic value after correction by the second characteristic value correction unit is X2,
The target value of the characteristic value is XO,
When the detected temperature is equal to or higher than the first temperature, the secondary correction formula is the formula X2 = XO + (XC−XO) × (T−TH) / (TC−TH), and the detected temperature is the first temperature. The inclination angle calculation device according to claim 11, wherein, when the temperature is less than one temperature, the equation is X2 = XO + (XC−XO) × (T−TL) / (TC−TL). The characteristic value after correction by the second characteristic value correction unit is X2,
The target value of the characteristic value is XO,
12. The secondary correction formula is the formula X2 = XO + (XC-XO) * (T-TL) * (T-TH) / (TC-TL) / (TC-TH). Inclination angle calculation device. The characteristic value is a value of offset and detection sensitivity of the acceleration detection unit,
14. The target value of the characteristic value is a target value of detection sensitivity of the acceleration detector, and a target value of offset of the acceleration detector is 0. 14. Inclination angle calculation device.

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