JP2013064670A - Contact surface shape measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring device capable of more accurately measuring a shape of a contact surface between soft objects.SOLUTION: A contact surface shape measuring device 100 which measures a shape of a contact surface 106 between soft objects 102 and 104 comprises: a substrate 108 which has flexibility and is arranged along the contact surface; two or more strain sensors 110 which measure strain amounts at positions on the substrate where the strain sensors are attached thereto; a shape approximation section 120 which calculates curvature on the basis of the strain amounts as well as a curve approximating the shape of the contact surface along a path connecting the two or more strain sensors on the basis of the curvature; at least two acceleration sensors 112 which are arranged along the path on the substrate and measure inclination angles at positions on the substrate where the acceleration sensors are attached thereto; a comparison section 122 which calculates a difference between an angle of tangent of the approximate curve at the position where either of the acceleration sensors is arranged and the measured inclination angle; and a correction section 124 which corrects the approximate curve so that the difference falls within a predetermined value.

Description

  The present invention relates to a contact surface shape measuring apparatus that measures the shape of a contact surface between flexible objects.

  In general, when flexible objects come into contact with each other, the contact surface (contact interface) is deformed by the interaction between the objects. Below, as a flexible object, the seat (seat cushion) of a vehicle and the passenger | crew who seats on this seat are mentioned and demonstrated.

  A vehicle seat includes a member serving as a skeleton disposed inside and a plurality of members having different flexibility such as cushions and skin materials having different foaming ratios, and these members are formed in a composite manner. . The occupant contains a skeleton and a plurality of flexible muscles. That is, both the vehicle seat and the occupant are flexible objects that are deformed by a load.

  Such a contact surface between the occupant and the seat is likely to be complicatedly deformed by the interaction between the two. For example, in a situation where an occupant with individual differences in physique and body condition sits on the seat, adjusts the posture arbitrarily, and receives vibration and acceleration while the vehicle is running, the contact surface undergoes complex deformation .

  The interaction between the occupant and the seat not only greatly affects the sitting comfort felt by the occupant, but in some cases may cause pain or the like to the human body and cause health problems. For this reason, the technique of predicting the state of the contact surface between flexible objects from the outside is also important in vehicle design.

  For example, there is a technique for measuring a pressure distribution on a contact surface using a sheet-like pressure sensor and observing the state of the contact surface based on the measured pressure distribution. However, with this technique, physical parameters such as the stiffness of the occupant's muscles when seated cannot be observed, so it is difficult to accurately predict the deformation state of the contact surface.

  Patent Document 1 discloses a method in which a large number of strain sensors attached to the surface of a tape-like elastic metal plate are sandwiched between contact surfaces of a seat and an occupant, and deformation of the elastic metal body is detected by the strain sensor. A technique for measuring the shape of a surface is described. The shape of the elastic metal body is deformed along the shape of the contact surface.

JP-A-5-296706

  The strain sensor can measure only the amount of strain at the position attached to the elastic metal plate. As in Patent Document 1, in a technique using a strain sensor, a curvature is calculated based on a strain amount that is a measurement value of a plurality of strain sensors, and each arc having a predetermined radius and center angle is calculated. And the shape of an elastic metal plate is approximated by connecting each circular arc.

  However, the shape of the elastic metal body is a continuous curved surface. For this reason, in the above technique for approximating the shape using only discrete curvature with respect to a continuous curved surface, for example, when a sharp bend occurs at a position where a strain sensor is not attached, the calculated arc May not match the actual shape. Therefore, in the above technique, since the shape is approximated by connecting the calculated arcs that do not match the actual shape, an error from the actual shape is accumulated.

  In view of such a problem, an object of the present invention is to provide a contact surface shape measuring apparatus that can more accurately measure the shape of a contact surface between flexible objects.

  In order to solve the above problems, a typical configuration of a contact surface shape measuring apparatus according to the present invention is arranged along a contact surface in a contact surface shape measuring apparatus that measures the shape of a contact surface between flexible objects. A flexible substrate, two or more strain sensors that are attached to the substrate and measure the strain amount of the substrate at the pasting position, a curvature is calculated based on the strain amount, and two or more strain sensors are calculated based on the curvature. A shape approximating unit that calculates a curve that approximates the shape of the contact surface along the path to which the strain sensor is attached, and at least two acceleration sensors that are arranged in the path on the substrate and measure the inclination angle of the substrate at the arrangement position; A comparison unit that calculates a difference between the tangent angle of the approximated curve and the measured inclination angle at any of the acceleration sensor arrangement positions, and a correction unit that corrects the approximated curve so that the difference falls within a predetermined value; Characterized by comprising That.

  According to the above configuration, when the flexible substrate forms a continuous curved surface along the shape of the contact surface, the plurality of strain sensors measure the amount of strain at the position where the substrate is stuck. That is, the strain sensor measures a discrete strain amount with respect to a continuous curved surface. The shape approximation unit calculates the curvature based on the discrete distortion amount, and calculates the curve based on this curvature, so the calculated curve and the actual shape of the contact surface do not match and an error occurs. There is. On the other hand, the inclination angle measured by the acceleration sensor is an angle formed with respect to the direction of gravity at the position where the acceleration sensor is arranged, and always maintains a constant accuracy. Therefore, the correction curve is set so that the difference between the tangent angle of the curve obtained by approximation and the actually measured inclination angle at the position of the acceleration sensor as the measurement point is within a predetermined value. Correct. Therefore, with the above configuration, the shape of the contact surface can be measured more accurately by canceling the error of the curve caused by the discrete strain measured by the strain sensor using the tilt angle measured by the acceleration sensor. it can.

  The approximated curve is formed by connecting arcs based on the curvature calculated by the shape approximating unit, and the correcting unit may correct the entire approximated curve by the difference. In this case, the correction unit subtracts the difference between the tangent angle and the tilt angle at the position of the acceleration sensor from the tangent angle at the starting point that serves as the measurement reference for the approximated curve, and corrects the entire approximated curve by correcting the tilt. do it. In this way, the curve can be easily corrected.

  The approximated curve is formed by connecting each arc based on the curvature calculated by the shape approximating unit, and the correcting unit subtracts or adds the angle obtained by dividing the difference by the number of strain sensors from the central angle of each arc. It is preferable to correct the approximated curve by correcting the curved line approximated by each arc and connecting the corrected arcs. In this case, since the correction unit corrects the approximated curve for each arc, the curve can be corrected smoothly as a whole.

  The acceleration sensor may have two detection axes that are orthogonal to each other. In this case, since the output values of the two detection axes maintain a phase of 90 degrees, the sensitivity of the other detection axis is high in the region where the sensitivity of one detection axis decreases. For this reason, the tilt angle can be uniquely measured over 360 degrees by using a biaxial acceleration sensor.

  The acceleration sensor may have three detection axes that are orthogonal to each other. Thus, even when the substrate is deformed by being twisted around the longitudinal axis, the twist of the substrate can be detected by the three detection axes. Therefore, it is possible to measure the shape of the contact surface more accurately by correcting the curve in consideration of the detected twist.

  ADVANTAGE OF THE INVENTION According to this invention, the contact surface shape measuring apparatus which can measure the shape of the contact surface of flexible objects more correctly can be provided.

It is a figure which shows the state using the contact surface shape measuring apparatus in this embodiment. It is a figure which shows schematic structure of the contact surface shape measuring apparatus of FIG. It is a block diagram which shows the function of the contact surface shape measuring apparatus of FIG. It is a figure which shows the state which affixed the distortion sensor on the board | substrate. It is a figure which shows typically the relationship between the radius based on the distortion amount measured with a distortion sensor, and a center angle. It is a figure which shows typically the principle which approximates a shape by the continuation of a circular arc. It is a figure explaining the principle of the acceleration sensor used with the contact surface shape measuring apparatus of FIG. It is a figure which shows typically the principle of correction | amendment by the contact surface shape measuring apparatus in this embodiment. It is a figure which illustrates the state which corrected the curve with the contact surface shape measuring apparatus in this embodiment. It is a figure which shows the relationship between the inclination-angle of an acceleration sensor which has one detection axis, and an output. It is a figure explaining the acceleration sensor which has a 2-axis detection axis. It is a figure which shows the relationship between the inclination-angle of an acceleration sensor which has a biaxial detection axis, and an output. It is a figure which shows typically the principle of correction | amendment by the contact surface shape measuring apparatus using the acceleration sensor which has a 3 axis | shaft detection axis. It is a figure which shows the other example of arrangement | positioning of an acceleration sensor.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a diagram illustrating a state in which the contact surface shape measuring apparatus according to the present embodiment is used. FIG. 2 is a diagram showing a schematic configuration of the contact surface shape measuring apparatus of FIG. FIG. 3 is a block diagram showing functions of the contact surface shape measuring apparatus of FIG. As shown in FIG. 1, the contact surface shape measuring apparatus 100 measures the shape of flexible objects deformed by a load, that is, the contact surface (interface) 106 between the seat 102 and the passenger 104 seated on the seat 102. It is.

  As shown in FIG. 2, the contact surface shape measuring apparatus 100 includes a substrate 108, a strain sensor (strain cage) 110, and an acceleration sensor (gravity sensor) 112. The substrate 108 is a tape-like thin plate having flexibility. A plurality of strain sensors 110 are affixed on the substrate 108 at predetermined intervals. The “predetermined intervals” are all constant in the present embodiment, but may be intervals of various predetermined lengths. The acceleration sensor 112 is disposed on the substrate 108 at an interval including at least one strain sensor 110. The substrate 108, the strain sensor 110, and the acceleration sensor 112 are used while being sandwiched between the contact surfaces 106 shown in FIG. The substrate 108 is deformed along the shape of the contact surface 106 while being sandwiched between the contact surfaces 106.

  As shown in FIG. 2, the strain sensor 110 is affected by the tensile force and the compressive force applied to the substrate 108 indicated by the white arrow, so that the substrate 108 is attached to the substrate 108 at the position (applied position). Measure the amount of distortion.

  The acceleration sensor 112 measures the tilt angle of the substrate 108 at the position (arrangement position) where the acceleration sensor 112 is disposed on the substrate 108. As shown in FIG. 2, the acceleration sensor 112 measures the inclination of the tangent line at the position of the substrate 108 indicated by the alternate long and short dash line, that is, the inclination angle, based on the direction of gravity indicated by the arrow.

  As shown in FIG. 3, the contact surface shape measuring apparatus 100 includes an input unit 114 including the strain sensor 110 and the acceleration sensor 112, an interface shape estimation unit 116, and a display unit 118. The interface shape estimation unit 116 includes a shape approximation unit 120, a comparison unit 122, and a correction unit 124. The interface shape estimation unit 116 approximates the shape of the contact surface 106 based on the strain amount input from the strain sensor 110, and further, approximates the contact surface 106 based on the inclination angle input from the acceleration sensor 112. Correct the shape. Hereafter, each structure is demonstrated roughly.

  The shape approximating unit 120 receives the amount of strain at the attachment position of the substrate 108 measured by the strain sensor 110. The shape approximating unit 120 calculates a curvature based on the input strain amount, and calculates a curve approximating the shape of the contact surface 106 based on the curvature. In addition, a curve means the data which show a curve.

  Data indicating the curve calculated by the shape approximating unit 120 and the inclination angle at the arrangement position of the substrate 108 measured by the acceleration sensor 112 are input to the comparing unit 122. The comparison unit 122 compares the tangent angle of the curve calculated by the shape approximation unit 120 (described later with reference to FIG. 6A) at the position where the substrate 108 is disposed with the inclination angle input from the acceleration sensor 112. And the difference is calculated.

  The correcting unit 124 corrects the data indicating the curve calculated by the shape approximating unit 120 so that the difference calculated by the comparing unit 122 falls within a predetermined range. Note that within the predetermined range, for example, it is preferable to make the tangent angle substantially coincide with the inclination angle to make the difference smaller, but there is no particular limitation.

  The display unit 118 is an appropriate display or the like, and displays a curve based on data indicating the curve corrected by the correction unit 124.

  Next, the principle of calculating a curve that approximates the shape of the contact surface 106 using the strain sensor 110 will be described with reference to FIGS. FIG. 4 is a diagram illustrating a state in which the strain sensor 110 is attached to the substrate 108. FIG. 4A shows a state where the substrate 108 is not receiving a load. FIG. 4B shows a state where the substrate 108 is deformed by receiving a load. FIG. 5 is a diagram schematically illustrating the relationship between the radius and the center angle based on the strain amount measured by the strain sensor 110. FIG. 6 is a diagram schematically illustrating the principle of approximating the shape by a continuous arc. FIG. 6A is a diagram showing a state in which the shape is approximated by a continuous arc. FIG. 6B is a diagram illustrating an error due to the measurement of the strain sensor 110.

  First, when the plurality of strain sensors 110 attached to the substrate 108 shown in FIG. 4A are sandwiched between the contact surfaces 106, the tensile force and the compression indicated by the white arrows in FIG. Receive power. The strain sensor 110 measures the amount of strain ε at the attachment position (pasting point) of the substrate 108.

  The strain amount ε is in the relationship of the thickness t and the radius of curvature r of the substrate 108 and the equation (1).

ε = t / 2r (1)
For this reason, the radius of curvature r of the arc including the attachment position of the strain sensor 110 is derived from the amount of strain ε and the thickness t of the substrate 108 from Equation (1).

  Furthermore, as shown in FIG. 5, when the interval between the strain sensors 110 is d, the distance between the strain sensors 110 attached at equal intervals is the length of an arc having a curvature obtained from the strain amount ε. The distance d between the strain sensors 110 is in the relationship of the center angle θ of the arc with the formula (2).

θ = d / r (2)
The shape approximating unit 120 connects the arcs having the radius r and the center angle θ derived from the measurement values of the respective strain sensors 110 as shown in FIG. Approximate. Here, a state is shown in which an arc having a radius r ₁ and a center angle θ ₂ is connected to an arc having a radius r ₀ and a center angle θ ₁ .

Further, θ ₀ shown in FIG. 6A is used as a measurement standard. The measurement reference θ ₀ is horizontal. Further, the tangent angle of the arc having the radius r ₀ and the center angle θ ₁ is indicated by “θ ₀ + θ ₁ ”, and the tangent angle θ _{s of the} arc having the radius r ₁ and the center angle θ ₂ connected to the arc is expressed as “ θ ₀ + θ ₁ + θ ₂ ”. Thus, the tangent angle of the arc is calculated by adding the center angle every time the arc is connected.

  However, while the flexible substrate 108 forms a continuous curved surface along the shape of the contact surface 106, the strain sensor 110 only measures the amount of strain at the position where the substrate 108 is applied. That is, the shape approximating unit 120 calculates a discrete curvature from the measured distortion amount for a continuous curved surface.

  Since the shape approximating unit 120 calculates the curve based on the discrete curvature, as shown in FIG. 6B, the shape 140 of the actual contact surface 106 indicated by the solid line and the calculation indicated by the two-dot chain line are calculated. The curve 142 may not match and an error may occur. Other problems will be described below.

  First, the center angle measurement error by each strain sensor 110 may be accumulated. In addition, since the amount of strain at each strain sensor 110 is approximated and integrated with a corresponding arc, an error occurs when the shape of the strain sensor 110 is difficult to approximate with a continuous arc. End up.

Furthermore, when a sharp bend occurs between the strain sensors 110, the amount of strain cannot be measured by the strain sensor 110, and the distance between the curve estimated from the arc radius and the center angle and the actual curve is not possible. In this case, a deviation occurs and an error occurs in the overall shape. Further, as a starting point for accumulating the curvature calculated from the strain amount, a portion fixed to the coordinate system serving as a measurement reference is required on the strain sensor 110, and at least the measurement reference θ ₀ shown in FIG. Need to be.

  In order to increase the accuracy of the measurement, it is conceivable to install a large number of strain sensors 110 by reducing the interval between the strain sensors 110. However, in that case, the number of wirings increases, making it difficult to reduce the size of the entire strain sensor 110, and a large number of strain measurement amplifiers are required and the apparatus becomes complicated.

  Therefore, in the contact surface shape measuring apparatus 100 of the present embodiment, as shown in FIG. 2, the acceleration sensor 112 is arranged on the substrate 108 in addition to the strain sensor 110, the main measurement is performed by the strain sensor 110, and a plurality of strain sensors. A method of canceling the accumulated error due to 110 by the acceleration sensor 112 was adopted. Hereinafter, a description will be given with reference to FIGS.

  FIG. 7 is a diagram illustrating the principle of the acceleration sensor 112 used in the contact surface shape measuring apparatus 100 of FIG. The acceleration sensor 112, which is a gravity sensor, has a general DC component detection capability. In the acceleration sensor 112, as shown in FIG. 7, the detected gravitational acceleration G decreases at a rate of cos θ according to the angle θ that the detection axis 130 forms with the vertical line on the earth. In the figure, the gravitational acceleration detected by the acceleration sensor 112 is indicated by “G · cos θ”.

That is, the acceleration sensor 112 can detect the inclination of the acceleration sensor 112 using cos ⁻¹ from the detected magnitude of the DC component acceleration. Such inclination detection by the acceleration sensor 112 measures the angle formed with respect to the direction of gravity at each measurement point, and therefore has a characteristic that it always has a certain accuracy at any position.

  In the contact surface shape measuring apparatus 100, the tangential slope (tangential angle) of the curve indicating the shape of the contact surface 106 measured by the technique using the strain sensor 110 using the above characteristics of the acceleration sensor 112 is the slope measured by the gravity sensor. The accuracy is improved by correcting the inclination of the curve measured by the strain sensor 110 so as to be within a certain error range (inclination angle).

  However, the acceleration sensor 112 generally has a larger outer shape than the strain sensor 110, requires wiring for power supply, and is often expensive. For this reason, the contact surface shape measuring apparatus 100 is arranged at intervals including at least one strain sensor 110. Note that the acceleration sensor 112 is also preferably installed at a midpoint between the strain sensor 110 and the strain sensor 110, for example, at a rate of one for every several strain sensors 110.

  FIG. 8 is a diagram schematically showing the principle of correction by the contact surface shape measuring apparatus 100 in the present embodiment. FIG. 8A corresponds to FIG. 6A and shows a state in which an acceleration sensor 112 (indicated by G in the figure) is added. FIG. 8B shows a state in which the inclination angle is measured by the acceleration sensor 112. FIG. 9 is a diagram illustrating a state in which a curve is corrected by the contact surface shape measuring apparatus 100 according to the present embodiment.

The comparison unit 122 uses the tangent angle θ _{s of the} curve calculated by the shape approximating unit 120 at the position where the acceleration sensor 112 shown in FIG. 8A and the arrangement of the acceleration sensor 112 shown in FIG. A difference θ _d between the position and the calculated inclination angle θ _g with respect to the gravitational direction is calculated. The difference θ _d is indicated by “θ _s −θ _g ”.

The correction unit 124 corrects the inclination of the entire curve of the section by the difference with respect to the section in which the acceleration sensor 112 performs correction, that is, the section in which two arcs shown in FIG. 8A are connected. Specifically, the correction unit 124 subtracts the difference θ _d from the tangent angle θ ₀ that becomes the measurement reference in the section, sets the new measurement reference as “θ ₀ −θ _d ”, and tilts the entire curve of the section. to correct. In this way, the curve can be easily corrected.

  Here, a description will be given with reference to FIG. In the figure, the shape 140 indicated by the solid line is the true shape as in FIG. In addition, the shape 142 indicated by the two-dot chain line is set as the approximate shape of the curve calculated by the shape approximating unit 120. Furthermore, as shown in the figure, it is assumed that the difference θd exists between the tangent direction 140a at the end point of the true shape 140 and the tangent direction 142a at the end point of the approximate shape 142. The correction unit 124 performs the inclination correction by rotating the entire approximate shape 142 by the difference θd as shown in the drawing with the measurement reference of the approximate shape 142 as a starting point, and obtained a correction shape 144 indicated by a one-dot chain line in the drawing. . By such correction of the curve by the correction unit 124, the difference θd is generated between the tangential direction at the start point of the true shape 140 and the tangential direction of the start point of the correction shape 144. However, since the tangent direction 144a of the end point of the correction shape 144 coincides with the tangent direction 140a of the true shape 140, a simple correction of the curve by the correction unit 124 is performed.

  Further, the correction unit 124 is not limited to the above correction method, and adds or subtracts the central angle of each arc included in this section at a certain ratio to the section where the acceleration sensor 112 performs correction, and sets the section to each arc. You may correct | amend every.

Specifically, the correction unit 124 calculates the angle θ _d / n obtained by dividing the difference θ _d by the number n (two in FIG. 8A) of the strain sensors 110 included in the section, as the center angle of each arc. (In FIG. 8 (a), it subtracts or adds from (theta) ₁ , (theta) ₂ ), and correct | amends an area for every circular arc. In this way, the entire curve can be corrected more smoothly than the above method of correcting the inclination of the entire curve in the section.

  Referring to FIG. 9 again, a correction shape 146 indicated by a dotted line in the drawing shows a state after the approximate shape 142 is corrected for each arc by the correction unit 124. As shown in the figure, the corrected shape 146 corrected for each arc is such that the tangent direction 146a at the end point coincides with the tangent direction 140a at the end point of the true shape 140, and the tangent direction at the start point of both shapes is also the same. I'm doing it. Therefore, the correction shape 146 is closer to the true shape 140 than the correction shape 144, for example.

  In the contact surface shape measuring apparatus 100 of the present embodiment, shape measurement by an inexpensive, small, and thin strain sensor 110 is corrected by an acceleration sensor 112 that does not accumulate errors. In other words, the correction unit 124 improves the measurement accuracy of the shape of the contact surface 106 by correcting the tangent angle of the approximated curve so that the error from the inclination angle formed with respect to the direction of gravity falls within a certain range. ing.

  In other words, the contact surface shape measuring apparatus 100 interpolates the curvature calculated based on the strain amount obtained intermittently by the strain sensor 110 with the inclination angle obtained by the acceleration sensor 112. Thereby, in the contact surface shape measuring apparatus 100, the accumulated error from the starting point does not occur unlike the method of integrating the arcs in the strain sensor 110, and the measurement accuracy of the entire shape can be improved.

  Further, in the contact surface shape measuring apparatus 100, since the acceleration sensor 112 is arranged with a space in addition to the strain sensor 110 attached to the substrate 108, the apparatus is made smaller and thinner than the shape measurement by the acceleration sensor 112 alone. In addition, the amount of wiring can be reduced to reduce the cost.

  Moreover, in the said embodiment, although the acceleration sensor 112 had the uniaxial detection axis | shaft 130, it is not restricted to this, You may have a biaxial detection axis. Hereinafter, a specific description will be given with reference to FIGS.

  FIG. 10 is a diagram illustrating the relationship between the tilt angle and the output of the acceleration sensor 112 having the single detection axis 130. FIG. 11 is a diagram illustrating an acceleration sensor 112A having two detection axes 130 and 132. As shown in FIG. FIG. 12 is a diagram showing the relationship between the tilt angle of the acceleration sensor 112A having the two detection axes 130 and 132 and the output.

  The output of the acceleration sensor 112 and the tilt angle have a relationship of cos θ. For this reason, in the acceleration sensor 112, the angle detection sensitivity changes depending on the angle formed by gravity. In the acceleration sensor 112 having the uniaxial detection axis 130 shown in FIG. 10, the output change with respect to the angle change is small near 0 degrees, 180 degrees, and 360 degrees, and the inclination detection sensitivity is low. On the other hand, in the vicinity of 90 degrees and 270 degrees, the change in output with respect to the angle change is large, and the inclination detection sensitivity is high.

  That is, there are points with different tilt angles even if the output is the same, such as 90 degrees and 270 degrees. Therefore, the absolute value of the angle can be obtained only from the value of the acceleration sensor 112 having the single axis detection axis 130. Can not. In particular, when the detection axis 130 of the acceleration sensor 112 is installed on the same axis as the surface of the substrate 108, in a situation where the substrate 108 is substantially horizontal, the sensitivity is low and the positive side with respect to the horizontal. It is not known whether the inclination is negative or negative, and the output of the strain sensor 110 cannot be sufficiently corrected.

  Therefore, as shown in FIG. 11, by using an acceleration sensor 112A having two detection axes 130 and 132 orthogonal to each other, the tilt angle can be measured with high accuracy. In the biaxial acceleration sensor 112A, the output of the two detection axes 130 and 132 can compensate for the region where the sensitivity of one detection axis 130 decreases as shown in FIG. it can. In addition, since the output values from the two detection axes 130 and 132 have a phase of 90 degrees, the inclination angle of the tangent line can be obtained uniquely over 360 degrees. For example, since the sin component outputs values different from 1 and −1 at the 90 ° and 270 ° points where the cos component is 0, the two can be reliably distinguished.

  As described above, in the acceleration sensor 112A having the two detection axes 130 and 132, the sensitivity of the inclination angle and the detection performance of the absolute angle are improved as compared with the acceleration sensor 112 having the uniaxial detection axis 130. For this reason, by using the acceleration 112A, the output of the strain sensor 110 is sufficiently corrected, and the shape of the contact surface 106 can be reliably measured.

  Furthermore, although the uniaxial or biaxial acceleration sensors 112 and 112A are used in the above embodiment, the present invention is not limited to this, and an acceleration sensor having a triaxial detection axis may be used. By using an acceleration sensor (three-dimensional acceleration sensor) having three detection axes, deformation in the twisting direction around the axis along the longitudinal direction of the substrate 108 is detected, and the detection accuracy of the shape of the cross-sectional curve is improved. it can. This will be specifically described below.

  FIG. 13 is a diagram schematically showing the principle of correction by the contact surface shape measuring apparatus using an acceleration sensor having three detection axes. In the figure, a section sandwiched between two three-dimensional acceleration sensors (G0 and G1 in the figure) is assumed.

First, based on the strain amount measured by the strain sensor 110, the tangent angle θ _s of the curve at the arrangement position of the acceleration sensor G1 calculated by the shape approximating unit 120 is set to “θ ₀ ” as in FIG. + Θ ₁ + θ ₂ ”. Further, the orientation of the acceleration sensor G0 is horizontal for convenience of calculation. Furthermore, the attitude of the _{G 1,} yaw (theta _y), the sequence were ZXY type Euler angles of pitch (theta _p) and roll (θ _r).

The triaxial acceleration vector A of G ₀ and G ₁ is expressed by the following equation (3) when gravity g is used. Since the yaw angle cannot be measured by the acceleration sensor G1, only θ _p corresponding to the sensor deflection amount measured by the strain sensor 110 and θ _r corresponding to the torsion angle of the sensor are calculated based on the equation (3). It becomes possible to calculate as shown in Formula (4).

  In the measurement using the acceleration sensors 112 and 112A having one or two detection axes 130 and 132, the strain sensor 110 is attached along the longitudinal axis of the substrate 108 which is a thin tape-like plate. The torsional deformation around the axis of the substrate 108 is not considered. That is, in the above measurement, a method of accumulating curves on the assumption that the substrate 108 is not twisted and the axis is deformed in the same plane is adopted. For this reason, when measuring the shape of the contact surface 106 which becomes a three-dimensional curve, there is a possibility of measuring an incorrect shape as a cross-sectional shape.

  On the other hand, by using the acceleration sensor G1 having the detection axes of xyz orthogonal three axes, as shown in the above formulas (3) and (4), the deformation in the twist direction around the axis of the substrate 108 is detected. it can.

  Accordingly, the contact surface with which the substrate 108 is in contact is obtained by subjecting a curved line formed by a continuous arc estimated from the output of the strain sensor 110 to torsional deformation with respect to gravity at the measurement point at which the acceleration sensor G1 is disposed. The shape of 106 can be estimated more accurately. That is, it is possible to estimate to some extent which shape of the three-dimensional surface is actually measured, and the accuracy of detecting the shape of the curve can be improved.

  Furthermore, in the said embodiment, although the acceleration sensor 112 was installed in the state inclined on the board | substrate 108, it is not limited to this. FIG. 14 is a diagram illustrating another arrangement example of the acceleration sensors. Here, the acceleration sensor 112B is installed so that the surface direction of the substrate 108 and the detection axis are perpendicular to each other.

  In such a contact surface shape measuring apparatus 100A, it is easier to install the correct alignment on the substrate 108 than when the acceleration sensor 112B is installed on the substrate 108 in an inclined state. When the acceleration sensor 112 is installed on the substrate 108 in an inclined state as in the contact surface shape measuring apparatus 100, for example, calibration for measuring the initial output of the acceleration sensor 112 on a horizontal jig (not shown). Just do it.

  Further, in the above-described embodiment, the vehicle seat 102 and the occupant 104 have been described as flexible objects. However, the present invention is not limited thereto, and may be an electric wheelchair seat, furniture, bedding, etc. The contact surface shape measuring apparatus 100 may be applied to a purpose of measuring the shape of the contact surface between the flexible objects.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  INDUSTRIAL APPLICABILITY The present invention can be used for a contact surface shape measuring apparatus that measures the shape of a contact surface between flexible objects.

DESCRIPTION OF SYMBOLS 100, 100A ... Contact surface shape measuring apparatus, 102 ... Seat, 104 ... Passenger, 106 ... Contact surface, 108 ... Board | substrate, 110 ... Strain sensor, 112, 112A, 112B ... Accelerometer, 114 ... Input part, 116 ... Interface shape Estimating section 118 ... Display section 120 ... Shape approximating section 122 ... Comparison section 124 ... Correction section 130, 132 ... Detection axis 140 ... True shape 142 ... Approximate shape 144, 146 ... Correction 140a, 142a, 144a, 146a ... tangential direction

Claims (5)

In the contact surface shape measuring device that measures the shape of the contact surface between flexible objects,
A flexible substrate disposed along the contact surface;
Two or more strain sensors that are attached to the substrate and measure the amount of strain of the substrate at the attachment position;
A shape approximation unit that calculates a curvature based on the amount of distortion, and calculates a curve that approximates the shape of the contact surface along a path to which the two or more strain sensors are attached based on the curvature;
At least two acceleration sensors arranged in the path on the substrate and measuring an inclination angle of the substrate at the arrangement position;
A comparison unit that calculates a difference between a tangent angle of the approximated curve and the measured inclination angle at any one of the positions of the acceleration sensors;
A contact surface shape measuring apparatus comprising: a correction unit that corrects the approximated curve so that the difference falls within a predetermined value. The approximated curve is formed by connecting arcs based on the curvature calculated by the shape approximating unit,
The contact surface shape measurement apparatus according to claim 1, wherein the correction unit corrects the inclination of the entire approximated curve by the difference. The approximated curve is formed by connecting arcs based on the curvature calculated by the shape approximating unit,
The correction unit corrects the approximated curve for each arc by subtracting or adding an angle obtained by dividing the difference by the number of the strain sensors from the center angle of each arc, and the corrected arcs are corrected. The contact surface shape measuring apparatus according to claim 1, wherein the approximated curve is corrected by connecting the two.   The contact surface measuring apparatus according to claim 1, wherein the acceleration sensor has two detection axes orthogonal to each other.   The contact surface shape measuring apparatus according to claim 1, wherein the acceleration sensor has three detection axes orthogonal to each other.

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