JP2008185513A - Tilt angle sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tilt angle sensor capable of easily and responsively detecting a three-dimensional tilt concerning two planar axes. <P>SOLUTION: The tilt angle sensor includes: an acceleration sensor having at least mutually orthogonal first and second sensitivity axes; and a calculation means for finding a first tilt angle being a rotational angle of the first sensitivity axis and a second tilt angle being a rotational angle of the second sensitivity axis from the sum and subtraction of obtained output by finding the sum and subtraction of the output concerning the first and second sensitivity axes of the acceleration sensor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inclination angle sensor that can accurately measure an inclination with respect to gravity by using an acceleration sensor, and for example, knows a three-dimensional inclination with respect to a horizontal reference in a camera, a video camera, a mobile phone, and the like. The present invention relates to an inclination angle sensor used for correcting the inclination.

  An inclination angle sensor using an acceleration sensor is known as an inclination angle sensor that detects an accurate angle with respect to a horizontal reference (for example, Patent Documents 1 and 2).

  In the inclinometer described in Patent Document 1, cos φ and sin φ (φ: digital) are output sin θ and cos θ (θ: inclination angle of the accelerometer) of two moving coil accelerometers whose detection axes are arranged 90 ° apart from each other. The digital inclination angle output φ is obtained by multiplying the respective inclination angle outputs) and subtracting the obtained products and inputting them to the up / down counter.

  The tilt sensor described in Patent Document 2 uses a biaxial acceleration sensor that intersects with a piezoresistive element, and calculates the tilt angle near ± 45 ° by taking the sum or difference of the X-axis output and the Y-axis output. Yes.

Japanese Patent Laid-Open No. 08-128825 JP 2004-264053 A

  These inclination angle sensors disclosed in Patent Documents 1 and 2 only detect an inclination of one plane with respect to a horizontal plane so that it can be intuitively understood in which direction and how much the plane is inclined. It was impossible to detect in three dimensions.

  Accordingly, an object of the present invention is to provide an inclination angle sensor that can accurately detect a three-dimensional inclination about two axes of a plane.

  Another object of the present invention is to provide an inclination angle sensor capable of easily and easily detecting an inclination with respect to two axes of a plane.

  According to the present invention, the acceleration sensor having at least the first and second sensitivity axes orthogonal to each other and the sum and difference of the outputs related to the first and second sensitivity axes of the acceleration sensor are obtained, and the sum of the obtained outputs. In addition, an inclination angle sensor is provided that includes a first inclination angle that is the rotation angle of the first sensitivity axis and a second inclination angle that is the rotation angle of the second sensitivity axis from the difference.

  Further, according to the present invention, the acceleration sensor having first, second, and third sensitivity axes orthogonal to each other, and two sensitivity axes of the first, second, and third sensitivity axes of the acceleration sensor. A first inclination angle that is the rotation angle of the first sensitivity axis and a second inclination angle that is the rotation angle of the second sensitivity axis are obtained from the obtained sum and difference of the outputs. An inclination angle sensor provided with a calculation means is provided.

  The three-dimensional inclination of the plane is obtained by detecting the in-plane direction of gravity acceleration (angle with respect to the in-plane reference direction) and the plane angle with respect to the horizontal. Therefore, in order to know the three-dimensional inclination, it is necessary to detect the in-plane component of the gravitational acceleration in two directions intersecting each other in the plane. However, an error occurs in the in-plane component of the gravitational acceleration as the inclination increases.

  FIG. 1 is a diagram for explaining the output of an acceleration sensor when detecting a three-dimensional inclination with respect to two axes of a plane.

As shown in the figure, it is assumed that the X axis and the Y axis exist in the plane, and the Z axis is perpendicular to the plane. The rotation angle around the Y axis of the X ′ axis when this plane is inclined with respect to the horizontal X axis is α (degrees), and the rotation angle around the X axis of the Y ′ axis when this plane is inclined with respect to the horizontal Y axis. When the rotation angle is β (degrees), the X-axis component (output of the X-axis acceleration sensor) XA and the Y-axis component (output of the Y-axis acceleration sensor) YA of the gravitational acceleration G are affected by the cosine components orthogonal to each other. Included,
XA = G ・ sinα ・ cosβ
YA = G ・ sinβ ・ cosα
It is expressed. Further, the Z-axis component (output of the Z-axis acceleration sensor) ZA of the gravitational acceleration G is
ZA = G ・ cosα ・ cosβ
It is expressed.

  2 and 3 are diagrams in which the X-axis component XA and the Y-axis component YA of the acceleration sensor output with respect to the angles α and β in the case of detecting the inclination with respect to the two axes are respectively displayed in three dimensions.

  When the inclination is small, that is, in the region where the angles α and β are small, both cos α and cos β are close to 1, so that the X-axis component XA and the Y-axis component YA can be represented by sin α and sin β, respectively. Therefore, the angles α and β can be uniquely determined from XA and YA, respectively. However, in the region where the angles α and β are large, cos α and cos β change greatly, so that a plurality of α and β exist for the value of XA as shown in FIG. It becomes impossible to specify β. Further, as shown in FIG. 3, since there are a plurality of α and β for the value of YA, it is impossible to specify the angles α and β from YA.

  Therefore, in the present invention, for example, the sum (XA + YA) and difference (XA−YA) of the X-axis component XA and the Y-axis component YA are obtained, and the angles α and β are obtained from the sum (XA + YA) and difference (XA−YA). -ing

FIG. 4 is a diagram in which the sum (XA + YA) of the X-axis component and the Y-axis component of the acceleration sensor output with respect to the angles α and β when detecting a three-dimensional tilt with respect to two axes is displayed in a three-dimensional manner. As shown in the figure, the sum (XA + YA) is
XA + YA = G · sin α · cos β + G · sin β · cos α = G · sin (α + β)
Therefore, if the division of α and β is performed, a simple equation is established for (α + β), and a partial linear approximation equation can be used. For this reason, one equation of simultaneous equations is obtained by linear approximation of (α + β).

FIG. 5 is a diagram in which the difference (XA−YA) between the X-axis component and the Y-axis component of the acceleration sensor output with respect to the angles α and β when detecting a three-dimensional tilt with respect to two axes is displayed in a three-dimensional manner. As shown in the figure, the difference (XA−YA) is
XA-YA = G.sin.alpha.cos.beta.-G.sin.beta.cos.alpha. = G.sin (.alpha .-. Beta.)
Therefore, if the division of α and β is performed, a simple equation is established for (α−β), and a partial linear approximation equation can be used. For this reason, another equation of simultaneous equations is obtained by linear approximation of (α−β).

  By solving the simultaneous equations obtained by these two equations, the inclination α related to the front and rear of the plane and the inclination β related to the left and right can be uniquely obtained by simple calculation, and the inclination about the two axes of the plane can be accurately and easily performed. And with good responsiveness. Therefore, for example, it is very effective when used for a vehicle for moving at a constant speed, such as a train, a car, a ship, an airplane, etc., and a sensor for knowing the tilt of the front, rear, left and right of a camera. Moreover, even when the values of the inclinations α and β are large, the values can be obtained with high accuracy. For this reason, when the tilt angle sensor of the present invention is used for tilt correction with respect to the horizontal reference in, for example, a camera, a video camera, a mobile phone, and the like, accurate and stable correction operation can be performed.

  As described above, the calculation means calculates the first equation indicating the relationship between the sum of the obtained outputs and the sum of the first and second inclination angles, and the difference between the obtained outputs and the first and second inclination angles. It is preferable that the first and second inclination angles are obtained from simultaneous equations based on the second equation indicating the relationship with the difference. This first equation is a linear approximation of the sum of the output obtained and the sum of the first and second inclination angles, and the difference between the output obtained by the second equation and the first and second inclination angles. It is more preferable to use a linear approximation formula with the difference.

  There is also provided an inclination angle range determining means for determining which range the first and second inclination angles are from the output relating to any one sensitivity axis of the first, second and third sensitivity axes. preferable.

  It is also preferable that the inclination angle range determining means includes means for determining whether the absolute values of the first inclination angle and the second inclination angle are less than 45 degrees or more than 135 degrees. . In this case, when the absolute values of the first tilt angle and the second tilt angle are less than 45 degrees or greater than 135 degrees, the first and second tilts are output from the outputs related to the first and second sensitivity axes. It is preferable that the calculation means includes means for obtaining the angle.

  Further, when the absolute values of the first inclination angle and the second inclination angle are not less than 45 degrees and not more than 135 degrees, the output relating to the first sensitivity axis is replaced with the output relating to the third sensitivity axis. The output related to the third sensitivity axis and the output related to the second sensitivity axis are replaced with the output related to the third sensitivity axis by replacing the output related to the third sensitivity axis and the output related to the second sensitivity axis. More preferably, the computing means includes means for obtaining the first and second inclination angles from the output relating to the above.

  According to the present invention, the inclination related to the front and rear of the plane and the inclination related to the left and right can be uniquely obtained by simple calculation, and the inclination related to the two axes of the plane can be detected accurately and easily with high responsiveness. . Moreover, even when the inclination is large, the value can be obtained with high accuracy.

  FIG. 6 is a perspective view schematically showing an acceleration sensor in one embodiment of the tilt angle sensor of the present invention, and FIG. 7 is a diagram for explaining an output signal of the acceleration sensor. This embodiment is a case of an inclination angle sensor that can detect an inclination with two axes as rotation axes using a single three-axis acceleration sensor. Instead of a single triaxial acceleration sensor, three uniaxial acceleration sensors may be used.

  As shown in FIG. 6, an acceleration sensor 11 capable of detecting acceleration in the three-axis directions of the X axis, the Y axis, and the Z axis is fixed on the substrate 10. Here, the arrow direction shown in the figure is the positive direction of each axis in each acceleration sensor, and hereinafter, the positive directions of these X axis, Y axis, and Z axis are simply referred to as the X axis direction, the Y axis direction, and the Z axis direction. Respectively.

  As shown in FIG. 1, the plane on which the acceleration sensor 11 is placed is inclined by an angle α with respect to the X axis with the Y axis as the rotation center axis, and is inclined by an angle β with respect to the Y axis with the X axis as the rotation center axis. And In this case, from the acceleration sensor 11, as shown in FIG. 7, the signal XA = G · sin α · cos β related to the X axis, the signal YA = G · sin β · cos α related to the Y axis, and the signal ZA = G · cos α and cos β are output and input to an arithmetic circuit, which will be described later, to obtain angles α and β. However, G is a gravitational acceleration.

  FIG. 8 is a block diagram showing the overall configuration of an arithmetic circuit for calculating the angles α and β from the signals XA, YA and ZA obtained from the acceleration sensor 11 in the tilt angle sensor of this embodiment, and FIG. FIG. 10 is a circuit diagram showing a configuration of a biaxial signal selection circuit in the arithmetic circuit, and FIG. 11 is a sum signal difference signal generating in the arithmetic circuit. FIG. 12 is a circuit diagram showing a configuration of an approximate calculation circuit in the arithmetic circuit.

As shown in FIG. 8, the arithmetic circuit is configured by hardware in this embodiment. That is, the signal XA of three axes from the acceleration sensor 11, YA and ZA from the decision signal _{X on,} Y _on, and _{Z on, X> 0, Y} > 0 and determine the signal forming circuit 12 for creating a _{Z> 0,} the acceleration A biaxial signal selection circuit 13 that selects biaxial signals from the triaxial signals XA, YA, and ZA from the sensor 11 to generate signals MX and MY, and a sum signal MX + MY of the selected biaxial signals MX and MY, and Sum signal difference signal creating circuit 14 for calculating the difference signal MX-MY, and an approximate calculation circuit for calculating the angles α and β by performing an approximate calculation according to the angle range from the calculated sum signal MX + MY and the difference signal MX-MY. 15.

  As shown in FIG. 9, the determination signal generation circuit 12 includes differential amplifiers 12 a to 12 f that obtain differential outputs of the triaxial signals XA, YA, and ZA and 2√2 · G and −2√2 · G. Differential amplifiers 12g to 12i that obtain a differential output of three-axis signals XA, YA, and ZA and zero, and AND gates 12j to 12l are provided.

This configuration, ZA-2√2 · G> 0 , ZA + 2√2 · G <0, in the case of _{X on} = 0 and _{Y on = 0, Z on =} 1 becomes, YA-2√2 · G> 0 , YA + 2√2 · G <0, X _on = 0 and Z _on = 0, Y _on = 1, XA-2√2 · G> 0, XA + 2√2 · G <0, Y _on = 0 When Z _on = 0, determination signals X _on , Y _on, and Z _on that X _on = 1 are output. Further, when XA> 0, X _{> 0} becomes 1, when YA> 0, Y _{> 0} becomes 1, and when ZA> 0, Z _{> 0} becomes 1. Determination signals X _{> 0} , Y _{> 0} And Z _{> 0} are output.

As shown in FIG. 10, the biaxial signal selection circuit 13 includes gates 13 a to 13 f controlled by determination signals X _on , Y _on, and Z _on . Thus, when X _on = 1, signals XA and YA are selected to become signals MX and MY, respectively, and when Y _on = 1, signals ZA and YA are selected to become signals MX and MY, respectively, and Z _on = In the case of 1, the signals XA and ZA are selected to become signals MX and MY, respectively, and the obtained signals MX and MY are output.

  As shown in FIG. 11, the sum signal difference signal generation circuit 14 includes amplifiers 14a and 14b and differential amplifiers 14c and 14d. The sum signal MX + MY and the difference signal MX are input from the input signals MX and MY. -My is calculated and output.

As shown in FIGS. 8 and 12, the approximate calculation circuit 15 determines the angle range based _on the determination signals X _{> 0} , Y _{> 0} , Z _{> 0} , _Xon , _Yon, and _Zon , and determines the angle range. Depending on the range, the approximate expression of the sum signal MX + MY and the difference signal MX-My and the trigonometric functions of α + β, α-β, α + β + 90, α-β + 90, α-β-90 with respect to the angles α and β is selected and approximated. The simultaneous equations by the equation are solved to calculate the angles α and β and output them.

  Hereinafter, the approximate expression selected based on the angle ranges of α, β, and α + β will be described. However, in the following description, the unit of angle (degree) is omitted. In the following description, α + β is not a scalar sum but an angle of the sum vector.

(A) −45 <α <45, −45 <β <45, and −45 <α + β <45, or 135 <α <180, 135 <β <180, and 135 <α + β <180, or −180 <α. <−135, −180 <β <−135 and −180 <α + β <−135,
XA + YA = G · sin α · cos β + G · sin β · cos α = G · sin (α + β),
XA-YA = G.sin.alpha.cos.beta.-G.sin.beta.cos.alpha. = G.sin (.alpha .-. Beta.)
Since ZA = G · cos α · cos β, G · cos (α + β) = ZA−G · sin α · sin β holds.

  FIG. 13 is a diagram illustrating the characteristics of XA + YA and ZA when α, β, and α + β are in this angle range, where the horizontal axis represents α + β (degrees) and the vertical axis represents output (G).

From the figure, ZA is larger than √2 / 2 · G when −180 <α + β <−135 and 135 <α + β <180, and ZA is smaller than −√2 / 2 · G when −45 <α + β <45. . Therefore, the angle range of (A) is defined by ZA> √2 / 2 · G or ZA <−√2 / 2 · G. As described above, when α and β are within this angular range, the determination signal Z _on is set to Z _on = 1.

  As can be seen from the figure, in the range of ZA> √2 / 2 · G or ZA <−√2 / 2 · G, XA + YA is uniquely determined and can be linearly approximated as follows. .

When ZA <0 (Z _{> 0} = 0),
XA + YA = √2 / 90 · (α + β), and therefore α + β = 90 / √2 · (XA + YA).
When ZA> 0 (Z _{> 0} = 1) and XA + YA <0,
XA + YA = −√2 / 90 · (α + β) −2√2, and thus α + β = −90 / √2 · (XA + YA) −180.
When ZA> 0 (Z _{> 0} = 1) and XA + YA> 0,
XA + YA = √2 / 90 · (α + β) + 2√2, and therefore α + β = 90 / √2 · (XA + YA) +180.

  FIG. 14 is a diagram illustrating the characteristics of XA-YA and ZA when α, β, and α + β are in this angle range, where the horizontal axis represents α-β (degrees) and the vertical axis represents output (G). .

From the figure, ZA is larger than √2 / 2 · G when −180 <α−β <−135 and 135 <α−β <180, and when −45 <α−β <45, ZA is −√2 / Less than 2 · G. Therefore, the angle range of (A) is defined by ZA> √2 / 2 · G or ZA <−√2 / 2 · G, as described above. When α and β are within this angular range, the determination signal Z _on is set to Z _on = 1.

  As can be seen from the figure, in this range of ZA> √2 / 2 · G or ZA <−√2 / 2 · G, XA-YA is uniquely determined and should be linearly approximated as follows: Can do.

When ZA <0 (Z _{> 0} = 0),
XA−YA = √2 / 90 · (α−β), and therefore α−β = 90 / √2 · (XA−YA).
When ZA> 0 (Z _{> 0} = 1) and XA−YA <0,
XA−YA = −√2 / 90 · (α−β) −2√2, and thus α−β = −90 / √2 · (XA−YA) −180.
When ZA> 0 (Z _{> 0} = 1) and XA-YA> 0,
XA−YA = √2 / 90 · (α−β) + 2√2, and therefore α−β = 90 / √2 · (XA−YA) +180.

(B) When 45 <α <135, 45 <α + β <135, or −180 <α <−135, −180 <α + β <−135,
In this case, as shown in FIG. 15A, the Z axis has an inclination of α + 90, and when the X axis is replaced with the Z axis, that is, when the ZA signal is used instead of the XA signal,
ZA + YA = G · sin (α + 90) · cosβ + G · sinβ · cos (α + 90) = G · sin (α + β + 90),
ZA−YA = G · sin (α + 90) · cosβ−G · sinβ · cos (α + 90) = G · sin (α−β + 90)
Since XA = G · sin α · cos β, G · cos (α + β + 90) = XA−G · sin α · cos β holds.

  FIG. 16 is a diagram showing the characteristics of ZA + YA and XA when α, β, and α + β are in this angle range, where the horizontal axis represents α + β + 90 (degrees) and the vertical axis represents output (G).

From the figure, when −135 <α + β + 90 <−45, XA is larger than √2 / 2 · G, and when 45 <α + β + 90 <135, XA is smaller than −√2 / 2 · G. Therefore, the angle range of (B) is defined by XA> √2 / 2 · G or XA <−√2 / 2 · G. As described above, when α and β are within this angular range, the determination signal X _on is set to X _on = 1.

  As can be seen from the figure, in the range of XA> √2 / 2 · G or XA <−√2 / 2 · G, ZA + YA is uniquely determined and can be linearly approximated as follows. .

When XA> 0 (X _{> 0} = 1),
ZA + YA = √2 / 90 · (α + β + 90), and therefore α + β + 90 = 90 / √2 · (ZA + YA) −90.
_{XA <0 (X> 0 =} 0) when,
ZA + YA = −√2 / 90 · (α + β + 90) + √2, and therefore α + β + 90 = −90 / √2 · (ZA + YA) +90.

  FIG. 17 is a diagram showing the characteristics of ZA-YA and XA when α, β, and α + β are in this angle range, where the horizontal axis represents α-β + 90 (degrees) and the vertical axis represents output (G). .

From the figure, when −135 <α−β + 90 <−45, XA is larger than √2 / 2 · G, and when 45 <α−β + 90 <135, XA is smaller than −√2 / 2 · G. Therefore, the angle range of (B) is defined by XA> √2 / 2 · G or XA <−√2 / 2 · G as described above. When α and β are within this angular range, the determination signal X _on is set to X _on = 1.

  As can be seen from the figure, in the range of XA> √2 / 2 · G or XA <−√2 / 2 · G, ZA-YA is uniquely determined and should be linearly approximated as follows: Can do.

When XA> 0 (X _{> 0} = 1) 0,
ZA−YA = √2 / 90 · (α−β + 90), and therefore α−β + 90 = 90 / √2 · (ZA−YA) −90.
When XA <0 (X _{> 0} = 0),
ZA−YA = −√2 / 90 · (α−β + 90) + √2, and therefore α−β + 90 = −90 / √2 · (ZA−YA) +90.

(C) When 45 <β <135, 45 <α + β <135, or −180 <β <−135, −180 <α + β <−135,
In this case, as shown in FIG. 15B, the Z axis has a slope of β + 90, and when the Y axis is replaced with the Z axis, that is, when the ZA signal is used instead of the YA signal,
XA + ZA = G · sin α · cos (β + 90) + G · sin (β + 90) · cosα = G · sin (α + β + 90),
XA−ZA = G · sin α · cos (β + 90) −G · sin (β + 90) · cos α = G · sin (α−β−90)
Since YA = G · sin β · cos α, G · cos (α + β + 90) = YA−G · sin α · cos β holds.

  FIG. 18 is a diagram illustrating the characteristics of XA + ZA and YA when α, β, and α + β are in this angle range, where the horizontal axis represents α + β + 90 (degrees) and the vertical axis represents output (G).

From the figure, when −135 <α + β + 90 <−45, YA is larger than √2 / 2 · G, and when 45 <α + β + 90 <135, YA is smaller than −√2 / 2 · G. Therefore, the angle range of (C) is defined by YA> √2 / 2 · G or YA <−√2 / 2 · G. As described above, when α and β are within this angular range, the determination signal Y _on is set to Y _on = 1.

  As can be seen from the figure, in the range of YA> √2 / 2 · G or YA <−√2 / 2 · G, XA + ZA is uniquely determined and can be linearly approximated as follows. .

When YA> 0 (Y _{> 0} = 1),
XA + ZA = √2 / 90 · (α + β + 90), and thus α + β + 90 = 90 / √2 · (XA + ZA) −90.
When YA <0 (Y _{> 0} = 0),
XA + ZA = −√2 / 90 · (α + β + 90) + √2, and therefore α + β + 90 = −90 / √2 · (XA + ZA) +90.

  FIG. 19 is a diagram illustrating the characteristics of XA-ZA and YA when α, β, and α + β are within this angular range, the horizontal axis represents α-β + 90 (degrees), and the vertical axis represents output (G). .

From the figure, YA is larger than √2 / 2 · G when −135 <α−β + 90 <−45, and YA is smaller than −√2 / 2 · G when 45 <α−β + 90 <135. Therefore, the angle range of (C) is defined by YA> √2 / 2 · G or YA <−√2 / 2 · G, as described above. When α and β are within this angular range, the determination signal Y _on is set to Y _on = 1.

  As can be seen from the figure, in this range of YA> √2 / 2 · G or YA <−√2 / 2 · G, XA-ZA is uniquely determined and should be linearly approximated as follows: Can do.

When YA> 0 (Y _{> 0} = 1),
XA−ZA = √2 / 90 · (α + β + 90), and thus α + β + 90 = 90 / √2 · (XA−ZA) −90.
When YA <0 (Y _{> 0} = 0),
XA−ZA = −√2 / 90 · (α + β + 90) + √2, and therefore α + β + 90 = −90 / √2 · (XA−ZA) +90.

As can be seen from the above description, the approximate calculation circuit 15 shown in FIGS. 8 and 12 obtains simultaneous equations in each condition range, and calculates the angles α and β therefrom. That is,
(1) When Z _on = 1 and ZA <0 (Z _{> 0} = 0),
From the simultaneous equations of α + β = 90 / √2 · (XA + YA) and α−β = 90 / √2 · (XA−YA), α = 90 / √2 · XA and β = 90 / √2 · YA are obtained.
(2) When Z _on = 1, ZA> 0 (Z _{> 0} = 1) and XA + YA <0 (XA−YA <0),
From the simultaneous equations α + β = −90 / √2 · (XA + YA) −180 and α−β = −90 / √2 · (XA−YA) −180, α = −90 / √2 · XA, β = −90 / √2 · YA is obtained.
(3) When Z _on = 1, ZA> 0 (Z _{> 0} = 1) and XA + YA> 0 (XA−YA> 0),
From the simultaneous equations α + β = 90 / √2 · (XA + YA) +180 and α−β = 90 / √2 · (XA−YA) +180, α = 90 / √2 · XA + 180, β = 90 / √2 · YA obtain.
(4) When X _on = 1 and XA> 0 (X _{> 0} = 1),
From the simultaneous equations α + β + 90 = 90 / √2 · (ZA + YA) −90 and α−β + 90 = 90 / √2 · (ZA−YA) −90, α = 90 / √2 · ZA-270, β = 90 / √ 2 · YA is obtained.
(5) When X _on = 1 and XA <0 (X _{> 0} = 0),
From the simultaneous equations α + β + 90 = −90 / √2 · (ZA + YA) +90 and α−β + 90 = −90 / √2 · (ZA−YA) +90, α = −90 / √2 · ZA, β = −90 / √ 2 · YA is obtained.
(6) When Y _on = 1 and YA> 0 (Y _{> 0} = 1),
From the simultaneous equations α + β + 90 = 90 / √2 · (XA + ZA) −90 and α + β + 90 = 90 / √2 · (XA−ZA) −90, α = 90 / √2 · XA-270, β = 90 / √2 · Obtain ZA.
(7) When Y _on = 1 and YA <0 (Y _{> 0} = 0),
From the simultaneous equations α + β + 90 = −90 / √2 · (XA + ZA) +90 and α + β + 90 = −90 / √2 · (XA−ZA) +90, α = −90 / √2 · XA, β = −90 / √2 · Obtain ZA.

  As described above, according to the present embodiment, a simple expression is established for the sum of the biaxial components of the acceleration sensor output and the sum of the angles α and β, and one of the simultaneous equations is obtained using a partial linear approximation expression. An equation is obtained, and a simple equation is established for the difference between the biaxial components and the difference between the angles α and β, and a partial linear approximation equation is used to obtain another equation of the simultaneous equations. By solving the equations, it is possible to uniquely obtain the inclination α related to the front and back of the plane and the inclination β related to the left and right by a simple calculation. Therefore, it is possible to detect a three-dimensional inclination with respect to the two axes of the plane with high accuracy, easily and with good responsiveness. For this reason, for example, it is very effective when used for a vehicle for moving at a constant speed such as a train, a car, a ship, an airplane, etc., or for a sensor for knowing the front / rear / left / right inclination of a camera. In addition, even when the values of the inclinations α and β are large, the values can be obtained with high precision. Therefore, the inclination angle sensor is used for inclination correction with respect to the horizontal reference in, for example, a camera, a video camera, and a mobile phone. In this case, accurate and stable correction operation can be performed.

  FIG. 20 is a block diagram showing the overall configuration of an arithmetic circuit for calculating the angles α and β from the signals XA, YA and ZA obtained from the acceleration sensor in another embodiment of the tilt angle sensor of the present invention. FIG. 22 is a flowchart schematically showing a computer program in the arithmetic circuit for calculating angles α and β in FIG. 20, and FIGS. 22, 23 and 24 are flowcharts schematically showing a part of the program in FIG. .

  The configuration and arrangement of the acceleration sensor itself in the present embodiment are the same as those in the embodiments of FIGS. What is different is the configuration of an arithmetic circuit that calculates the angles α and β by an approximate expression corresponding to the angle range.

  As shown in FIG. 20, in this embodiment, a digital computer (CPU) 17 is used as a circuit for calculating the angles α and β by an approximation formula corresponding to the angle range. That is, the output signals XA, YA and ZA of the acceleration sensor are converted into digital signals by the A / D converter 16 a in the interface circuit 16 and taken into the computer 17.

  In the computer 17, the following calculation is performed according to the flowchart of FIG.

  First, digitally converted XA, YA, and ZA are captured (step S1).

Next, when ZA-2√2 · G> 0, ZA + 2√2 · G <0, X _on = 0 and Y _on = 0, the determination signal Z _{on is set} to Z _on = 1 (step S2).

Next, when XA-2√2 · G> 0, XA + 2√2 · G <0, Y _on = 0 and Z _on = 0, the determination signal X _{on is set} to X _on = 1 (step S3).

Next, when YA-2√2 · G> 0, YA + 2√2 · G <0, X _on = 0 and Z _on = 0, the determination signal Y _{on is set} to Y _on = 1 (step S4).

Thereafter, it is determined whether or not the determination signal Z _on is Z _on = 1 (step S5).

When the determination result is Yes, MX = XA and MY = YA are set (step S6), and after calculating the sum MX + MY and the difference MX−MY (step S7), the approximate calculation process Z _on shown in FIG. 22 is performed. The routine is executed (step S8), and the calculated angles α and β are output (step S9).

If the determination result in step S5 is No, it is determined whether or not the determination signal X _on is X _on = 1 (step S10).

If the determination result is Yes, MX = ZA and MY = YA are set (step S11), and after calculating the sum MX + MY and the difference MX−MY (step S12), the approximate calculation process X _on shown in FIG. 23 is performed. The routine is executed (step S13), and the calculated angles α and β are output (step S9).

If the determination result in step S10 is No, it is determined whether or not the determination signal Y _on is Y _on = 1 (step S14).

When the determination result is Yes, MX = XA and MY = ZA are set (step S15), and after calculating the sum MX + MY and the difference MX−MY (step S16), the approximate calculation process Y _on shown in FIG. 24 is performed. The routine is executed (step S17), and the calculated angles α and β are output (step S9).

  If the determination result in step S14 is No, the process returns to step S5 and the same process is repeated.

The routine of the approximate calculation process Z _on is shown in FIG.

First, it is determined whether the determination signal Z _{> 0} is Z _{> 0} = 0, that is, whether ZA <0 (step S81).

If this determination result is Yes, it corresponds to the condition range (1) Z _on = 1, ZA <0 (Z _{> 0} = 0) in the embodiment of FIGS. 6 to 19, and the approximate expression α + β = 90. / √2 · (MX + MY) is obtained (step S82) and an approximate expression α−β = 90 / √2 · (MX−MY) is obtained (step S83), and simultaneous equations composed of these approximate expressions are solved to obtain α = 90 / √2 · MX = 90 / √2 · XA is calculated (step S84), and β = 90 / √2 · MY = 90 / √2 · YA is calculated (step S85).

  If the determination result in step S81 is No, it is determined whether or not MX + MY <0 (step S86).

If the determination result is Yes, the condition range (2) Z _on = 1, ZA> 0 (Z _{> 0} = 1) and XA + YA <0 (XA−YA <0) in the embodiment of FIGS. Corresponding to a certain case, the approximate expression α + β = −90 / √2 · (MX + MY) −180 is obtained (step S87) and the approximate expression α−β = −90 / √2 · (MX−MY) −180 is obtained ( In step S88), simultaneous equations composed of these approximate equations are solved to calculate α = −90 / √2 · MX = −90 / √2 · XA (step S89), and β = −90 / √2 · MY. = −90 / √2 · YA is calculated (step S90).

If the determination result in step S86 is No, the condition range (3) Z _on = 1, ZA> 0 (Z _{> 0} = 1) and XA + YA> 0 (XA−YA> 0) in the embodiment of FIGS. ), An approximate expression α + β = 90 / √2 · (MX + MY) +180 is obtained (step S91), and an approximate expression α−β = 90 / √2 · (MX−MY) +180 is obtained (step S92). ), Solving simultaneous equations composed of these approximate expressions to calculate α = 90 / √2 · MX + 180 = 90 / √2 · XA + 180 (step S93), and β = 90 / √2 · MY = 90 / √2 -YA is calculated (step S94).

The approximate calculation processing X _on routine is shown in FIG.

First, it is determined whether or not the determination signal X _{> 0} is X _{> 0} = 1, that is, whether XA> 0 (step S131).

If the determination result is Yes, the condition range ₍₄₎ in the embodiment of FIGS. 6 to 19 X on = 1, corresponds to a case XA> is _{0 (X> 0 = 1)} , approximate expression α + β + 90 = 90 / √2 · (MX + MY) −90 is obtained (step S132) and an approximate expression α−β + 90 = 90 / √2 · (MX−MY) −90 is obtained (step S133), and simultaneous equations composed of these approximate expressions are obtained. Solved, α = 90 / √2 · MX-270 = 90 / √2 · ZA-270 is calculated (step S134), and β = 90 / √2 · MY = 90 / √2 · YA is calculated (step S134). S135).

If the determination result in step S131 is No, it corresponds to the case where the condition range (5) X _on = 1 and XA <0 (X _{> 0} = 0) in the embodiment of FIGS. 6 to 19, and the approximate expression α + β + 90. = −90 / √2 · (MX + MY) +90 is obtained (step S136), and an approximate expression α−β + 90 = −90 / √2 · (MX−MY) +90 is obtained (step S137). By solving the equation, α = −90 / √2 · MX = −90 / √2 · ZA is calculated (step S138), and β = −90 / √2 · MY = −90 / √2 · YA is calculated. (Step S139).

The approximate calculation process Y _on routine is shown in FIG.

First, it is determined whether the determination signal Y _{> 0} is Y _{> 0} = 1, that is, whether YA> 0 (step S171).

If this determination result is Yes, it corresponds to the condition range (6) Y _on = 1, YA> 0 (Y _{> 0} = 1) in the embodiment of FIGS. 6 to 19, and the approximate expression α + β + 90 = 90. / √2 · (MX + MY) −90 is obtained (step S172) and an approximate expression α−β + 90 = 90 / √2 · (MX−MY) −90 is obtained (step S173), and simultaneous equations composed of these approximate expressions are obtained. Solving, α = 90 / √2 · MX−270 = 90 / √2 · XA-270 is calculated (step S174), and β = 90 / √2 · MY = 90 / √2 · ZA is calculated (step S174). S175).

If the determination result in step S171 is No, it corresponds to the case where the condition range (7) Y _on = 1 and YA <0 (Y _{> 0} = 0) in the embodiment of FIGS. 6 to 19, and the approximate expression α + β + 90. = −90 / √2 · (MX + MY) +90 is obtained (step S176) and an approximate expression α−β + 90 = −90 / √2 · (MX−MY) +90 is obtained (step S177), and the simultaneous equations including these approximate expressions are obtained. By solving the equation, α = −90 / √2 · MX = −90 / √2 · XA is calculated (step S178), and β = −90 / √2 · MY = −90 / √2 · ZA is calculated. (Step S179).

  Other configurations in the present embodiment, and the operations, effects, and the like in the present embodiment are shown in FIGS. 6 to 6 except that the circuit configuration can be further simplified and the cost can be reduced according to the configuration of the present embodiment. This is almost the same as the case of the nineteenth embodiment.

  All the embodiments described above are illustrative of the present invention and are not intended to be limiting, and the present invention can be implemented in other various modifications and changes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

It is a figure explaining the output of the acceleration sensor in the case of detecting the three-dimensional inclination of a plane. It is the figure which displayed in three dimensions the X-axis component XA of the acceleration sensor output with respect to the angles (alpha) and (beta) in the case of detecting the inclination regarding 2 axes | shafts. It is the figure which displayed three-dimensionally the Y-axis component YA of the acceleration sensor output with respect to the angles (alpha) and (beta) in the case of detecting the inclination regarding 2 axes | shafts. It is the figure which displayed three-dimensionally the sum (XA + YA) of the X-axis component of the acceleration sensor output with respect to the angle (alpha) and (beta) in the case of detecting the three-dimensional inclination regarding 2 axes | shafts, and (beta). It is the figure which displayed three-dimensionally the difference (XA-YA) of the X-axis component of the acceleration sensor output with respect to the angle (alpha) and (beta) in the case of detecting the three-dimensional inclination regarding 2 axes | shafts, and (beta). In one Embodiment of the inclination-angle sensor of this invention, it is a perspective view which shows an acceleration sensor schematically. It is a figure explaining the output signal of the acceleration sensor shown in FIG. In the above-described embodiment of the tilt angle sensor, it is a block diagram showing an overall configuration of an arithmetic circuit that calculates angles α and β from signals XA, YA, and ZA obtained from an acceleration sensor. It is a circuit diagram which shows the structure of the judgment signal preparation circuit in the arithmetic circuit shown in FIG. It is a circuit diagram which shows the structure of the biaxial signal selection circuit in the arithmetic circuit shown in FIG. It is a circuit diagram which shows the structure of the sum signal difference signal preparation circuit in the arithmetic circuit shown in FIG. It is a circuit diagram which shows the structure of the approximate calculation circuit in the arithmetic circuit shown in FIG. It is a figure showing the characteristic of XA + YA and ZA when (alpha), (beta), and (alpha) + (beta) exist in a predetermined angle range. It is a figure showing the characteristic of XA-YA and ZA when (alpha), (beta), and (alpha) -beta exists in a predetermined angle range. It is a figure explaining the case where the X-axis is replaced with a Z-axis, and the case where a Y-axis is replaced with a Z-axis. It is a figure showing the characteristic of ZA + YA and XA when (alpha), (beta), and (alpha) + (beta) +90 are in a predetermined angle range. It is a figure showing the characteristic of ZA-YA and XA in case (alpha), (beta), and (alpha)-(beta) +90 are in a predetermined angle range. It is a figure showing the characteristic of XA + ZA and YA when (alpha), (beta), and (alpha) + (beta) +90 are in a predetermined angle range. It is a figure showing the characteristic of XA-ZA and YA when (alpha), (beta), and (alpha) -beta-90 exist in a predetermined angle range. In other embodiment of the inclination-angle sensor of this invention, it is a block diagram which shows the whole structure of the arithmetic circuit which calculates angle (alpha) and (beta) from the signals XA, YA, and ZA obtained from an acceleration sensor. FIG. 21 is a flowchart schematically showing a computer program in an arithmetic circuit for calculating angles α and β in FIG. 20. It is a flowchart which shows a part of program of FIG. 21 roughly. It is a flowchart which shows a part of program of FIG. 21 roughly. It is a flowchart which shows a part of program of FIG. 21 roughly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Board | substrate 11 Acceleration sensor 12 Judgment signal creation circuit 12a-12i Differential amplifier 12j-12l AND gate 13 2 axis | shaft signal selection circuit 13a-13f Gate 14 Sum signal difference signal creation circuit 14a, 14b Amplifier 14c, 14d Differential amplifier 15 Approximation Calculation circuit 16 Interface circuit 16a A / D converter 17 Digital computer

Claims (10)

  An acceleration sensor having at least first and second sensitivity axes orthogonal to each other, and a sum and a difference of outputs related to the first and second sensitivity axes of the acceleration sensor are obtained, and the sum and difference of the obtained outputs are calculated from An inclination angle sensor comprising: a first inclination angle that is a rotation angle of a first sensitivity axis; and a calculation unit that obtains a second inclination angle that is a rotation angle of the second sensitivity axis.   The arithmetic means calculates the first expression indicating the relationship between the sum of the obtained outputs and the sum of the first and second inclination angles, and the difference between the obtained outputs and the first and second inclination angles. 2. The tilt angle sensor according to claim 1, wherein the tilt angle sensor is means for obtaining the first and second tilt angles from simultaneous equations based on a second formula indicating a relationship with a difference.   The first formula is a linear approximation formula of the sum of the obtained outputs and the sum of the first and second inclination angles, and the second formula is the difference between the obtained outputs and the first and second The tilt angle sensor according to claim 2, wherein the tilt angle sensor is a linear approximation formula with a difference between two tilt angles.   An acceleration sensor having first, second, and third sensitivity axes that are orthogonal to each other, and the sum and difference of outputs related to two sensitivity axes of the first, second, and third sensitivity axes of the acceleration sensor. And calculating means for obtaining a first inclination angle that is a rotation angle of the first sensitivity axis and a second inclination angle that is a rotation angle of the second sensitivity axis from the sum and difference of the obtained outputs. An inclination angle sensor comprising:   The arithmetic means calculates the first expression indicating the relationship between the sum of the obtained outputs and the sum of the first and second inclination angles, and the difference between the obtained outputs and the first and second inclination angles. 5. The tilt angle sensor according to claim 4, wherein the tilt angle sensor is means for obtaining the first and second tilt angles from simultaneous equations according to a second formula indicating a relationship with a difference.   The first formula is a linear approximation formula of the sum of the obtained outputs and the sum of the first and second inclination angles, and the second formula is the difference between the obtained outputs and the first and second The tilt angle sensor according to claim 5, wherein the tilt angle sensor is a linear approximation formula with a difference between two tilt angles.   Inclination angle range determining means for determining in which range the first and second inclination angles are based on an output related to one of the first, second, and third sensitivity axes. The inclination angle sensor according to any one of claims 4 to 6, wherein   The inclination angle range determining means includes means for determining whether absolute values of the first inclination angle and the second inclination angle are less than 45 degrees or more than 135 degrees. The tilt angle sensor according to claim 7.   When the absolute values of the first tilt angle and the second tilt angle are less than 45 degrees or greater than 135 degrees, the first and second sensitivity axes are output from the outputs related to the first and second sensitivity axes. 9. The tilt angle sensor according to claim 8, wherein said calculating means includes means for obtaining an tilt angle.   When the absolute values of the first tilt angle and the second tilt angle are not less than 45 degrees and not more than 135 degrees, the output related to the first sensitivity axis is replaced with the output related to the third sensitivity axis. From the output related to the replaced third sensitivity axis and the output related to the second sensitivity axis, or to the output related to the third sensitivity axis by replacing the output related to the second sensitivity axis with the output related to the third sensitivity axis 9. The tilt angle sensor according to claim 8, wherein the calculation means includes means for obtaining the first and second tilt angles from an output and an output related to the first sensitivity axis.

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