JP2011226829A - Sensor and acceleration detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor and an acceleration detection method capable of detecting displacements in a plurality of directions using a simple and compact acceleration sensor.SOLUTION: A sensor according to the present invention includes an optical fiber cable 202 having a plurality of FBG section subjected to FBG processing, beam members 203 and 204 provided by at least the two FBG sections and fixed at each of the fixed ends, which are one ends of the beam members, so that vibration directions of weights are controllable, and the weights 205 and 206 attached to the free ends, which are another ends of the beam members, of at least two of the beam members. The FBG sections are each processed to have different reflection light wavelengths.

Description

  The present invention relates to a sensor and an acceleration detection method.

Conventionally, various sensors for detecting acceleration are known. One example is an acceleration sensor using an optical fiber.
For example, Patent Document 1 describes a seismometer including an optical fiber grating and capable of measuring translational acceleration and rotational angular acceleration. Patent Document 2 describes an angle sensor using FBG (Fiber Bragg Grating) which is an optical detection element as a sensing part of an angle sensor incorporated in a displacement meter or an inclinometer.

JP 2001-281347 A JP 2003-287411 A

  However, the above-described acceleration sensor has a problem that its structure becomes complicated. In addition, the angle sensor has a problem that it is difficult to reduce the size because the structure becomes complicated.

  The seismometer described in Patent Literature 1 is positioned inside a hollow polyhedral casing so that the center position of the inner surface of the casing matches the center position of a solid load body having a polyhedral shape. Then, the solid load body is relatively displaced corresponding to the translational acceleration applied to the casing between four sides of the solid load body, that is, between the central portion of the inner surface of the casing and the central portion of the solid load body. The optical fiber grating is supported by a support wire.

  Since the solid load body is supported by a plurality of optical fiber gratings and support lines, it is difficult to limit the vibration direction of the solid load body. In addition, since the solid load body and the optical fiber grating are not provided in a one-to-one relationship, each direction in which the solid load body vibrates, for example, the x-axis direction, the y-axis direction, and the z-axis direction. It is difficult to detect each displacement.

  In the FBG type angle sensor described in Patent Document 2, a lever member is pivotally supported on a rotation shaft that is pivotally supported on a support plate, and the rotational force of the rotation shaft is transmitted to the lever member via a spring member. Then, the optical fiber in which the FBG is formed in the middle is fixed to the support plate and the lever member at the optical fiber portions on both sides of the FBG so that the FBG is stretched between the support plate and the lever member. Thereby, the tension acting on the FBG is changed by the spring member in accordance with the rotation angle of the rotation shaft, and the rotation angle of the rotation shaft is detected by the change of the Bragg wavelength due to the change in tension.

  The rotational force is converted into a force in the expansion / contraction direction via a spring member or the like, and is applied to the optical fiber forming the FBG. For this reason, it is difficult to detect the angular velocity from the change in the center point of the vibration of the FBG itself.

  The present acceleration sensor has been made in view of the above-described problems, and a problem to be solved is to provide a sensor and a detection method capable of detecting displacement in a plurality of directions using a simple and small acceleration sensor. That is.

  The sensor according to claim 1 is provided along an optical fiber cable having a plurality of FBG portions processed by FBG and at least two or more FBG portions so as to be able to regulate a vibration direction of a weight. A beam member fixed at a fixed end and a weight attached to a free end that is the other end of at least two or more of the beam members, and the FBG portions are processed into different reflected light wavelengths. It is the sensor characterized by the above.

  The beam member provided along the FBG portion refers to a case where the vibration of the beam member can be transmitted to the FBG portion, and is not limited to the case where the beam member is provided in direct contact with the FBG portion. The case where an FBG part and a beam member are arrange | positioned through such a protection member is included.

According to the sensor of the first aspect, it is possible to provide a plurality of acceleration sensors in one optical fiber cable.
The sensor according to claim 2 connects between the pair of FBG units when there is a pair of FBG units arranged with the weights facing each other on a line of the optical fiber cable among the FBG units. 2. The sensor according to claim 1, wherein a length of the optical fiber cable is longer than a linear interval between the weights attached to the pair of FBG portions.

According to the sensor of Claim 2, there exists an effect that the vibration of the weight arrange | positioned facing on the line of an optical fiber cable becomes difficult to propagate.
The sensor according to claim 3 is the sensor according to claim 1 or 2, wherein the FBG portions to which at least two or more weights are attached are arranged in different directions.

According to the sensor of the third aspect, it is possible to detect a change in weight in two dimensions.
The sensor according to claim 4 is the sensor according to claim 3, wherein the FBG portion to which at least two or more weights are attached is arranged in a direction orthogonal to the sensor.

According to the sensor of the fourth aspect, it is possible to detect the variation of the weight in two orthogonal directions, for example, the x-axis direction and the y-axis direction in the xy coordinate system.
The sensor according to claim 5, wherein the beam member is a member having a major axis and a minor axis in a cross-sectional shape perpendicular to the direction along the FBG portion. It is a sensor of any one of these.

According to the sensor of the fifth aspect, since the beam member is easily bent in the minor axis direction, it is suitable for regulating the vibration direction.
The sensor according to claim 6, further comprising: a fixing member that is disposed between weights disposed facing each other on a line of the optical fiber cable, and capable of fixing the optical fiber cable. It is a sensor of any one of -5.

According to the sensor of Claim 6, it becomes possible to suppress that the vibration of a weight is propagated between adjacent FBG parts.
The sensor according to claim 7, further comprising a support member that fixes the fixed end of the beam member.

According to the sensor of Claim 7, it becomes suitable for attaching an FBG part and a weight as a unit.
The sensor unit according to claim 8, further comprising: a light source unit that inputs multi-wavelength light to the optical fiber cable; and an arithmetic unit that acquires an output waveform from the FBG unit. The sensor unit according to item 1.

A vehicle according to a ninth aspect is a vehicle on which the sensor according to any one of the first to seventh aspects is mounted.
The vehicle according to the ninth aspect can detect various accelerations applied to the vehicle such as a yaw rate. Moreover, it becomes possible to implement | achieve the sensor of any one of Claim 1 to 7 using CAN (Controller Area Network) with which a vehicle is equipped. In this case, it is possible to detect the distortion of the beam member simultaneously with the exchange of various information using CAN.

  The acceleration detection method according to claim 10 is displaced according to vibration of a weight attached to the FBG portion among wavelengths included in the multi-wavelength light output by the sensor according to claims 1 to 4. The intensity of the wavelength is detected as the displacement of the sensor in the vibration direction of the weight, the center position of the vibration of the sensor is calculated from the displacement of the sensor, and at least two or more center positions calculated at present or in the past are relatively And the acceleration applied to the sensor is calculated from the comparison result.

  According to the present sensor, it is possible to provide a sensor capable of detecting displacement using a simple and small sensor and an acceleration detection method.

It is a figure which shows the structural example of the acceleration detection apparatus which implement | achieves the detection method of the acceleration using the acceleration sensor which concerns on a present Example. It is a figure which shows the structural example of the acceleration sensor which concerns on a present Example. It is a figure explaining the function of the 1st area of an optical fiber cable. It is a figure explaining the outline | summary of the detection method of the acceleration using the acceleration sensor which concerns on a present Example. It is a figure explaining the center value of the amplitude which concerns on a present Example. It is a flowchart which shows the detection process of the acceleration using the acceleration sensor which concerns on a present Example. It is the schematic diagram which showed the waveform from the 1st wavelength which concerns on a present Example. It is a figure explaining the case where a Lissajous curve is used for the detection method of the acceleration which concerns on a present Example. It is a figure which shows the 1st modification of a structure of the acceleration sensor which concerns on a present Example. It is a figure which shows the 2nd modification of a structure of the acceleration sensor which concerns on a present Example. It is a figure which shows the structural example of the acceleration sensor which detects only the acceleration of the specific direction which concerns on a present Example. It is a figure which shows the application example of the acceleration sensor which concerns on a present Example.

Hereinafter, an example of this embodiment will be described with reference to FIGS.
FIG. 1 is a diagram illustrating a configuration example of an acceleration detection apparatus 100 that realizes an acceleration detection method using the acceleration sensor according to the present embodiment.

  1 includes a multi-wavelength light emitting device (light source unit) 101, acceleration sensors 102 and 103, a spectroscope 104, and an arithmetic unit 105. The multi-wavelength light emitting device 101 and the acceleration sensor 102, the acceleration sensor 102 and the acceleration sensor 103, and the acceleration sensor 103 and the spectrometer 104 are connected by optical fiber cables 110, 111 and 112, respectively.

  The multiwavelength light emitting device 101 generates multiwavelength light including a plurality of wavelengths and outputs the multiwavelength light to the optical fiber cables 110, 111, and 112. The multiwavelength light emitting device 101 can be realized by, for example, a multiwavelength light emitting diode (LED) that outputs multiwavelength light having a plurality of wavelengths.

  In this embodiment, since the two acceleration sensors 102 and 103 are used, the multi-wavelength light emitting device 101 needs to generate and output multi-wavelength light including at least first to fourth wavelengths described later. is there.

  The acceleration sensor 102 attenuates and outputs only light of a specific wavelength among the multi-wavelength light input to the acceleration sensor 102 according to the vibration of the acceleration sensor 102. At this time, the attenuation of light is reflected inside the acceleration sensor 102 and output from the input end. In the present embodiment, the wavelength of the light that the acceleration sensor 102 attenuates and outputs in accordance with the vibration in the x-axis direction shown in FIG. 1 is referred to as a “first wavelength”. Further, the wavelength of light that the acceleration sensor 102 attenuates and outputs in response to vibration in the y-axis direction shown in FIG. 1 is referred to as a “second wavelength”.

  The acceleration sensor 103 also attenuates and outputs only light of a specific wavelength among the multi-wavelength light input to the acceleration sensor 103 according to the vibration of the acceleration sensor 103. In the present embodiment, the wavelength of the light that the acceleration sensor 103 attenuates and outputs in accordance with the vibration in the x-axis direction shown in FIG. 1 is referred to as a “third wavelength”. Further, the wavelength of light output by the acceleration sensor 103 after being attenuated according to the vibration in the y-axis direction shown in FIG. 1 is referred to as a “fourth wavelength”.

  The spectroscope 104 detects the intensities of the first to fourth wavelengths from the input multi-wavelength light. This is because in the present embodiment, the acceleration sensor 102 and the acceleration sensor 103 include FBG portions that are processed into different reflected light wavelengths, that is, first to fourth wavelengths. For example, the spectroscope 104 can convert the intensity of light of the first to fourth wavelengths into an electric signal and express it as a voltage value.

  The computing device 105 calculates the acceleration applied to the acceleration sensor 102 from the intensities of the first and second wavelengths output from the spectroscope 104. In addition, the arithmetic unit 105 calculates the acceleration applied to the acceleration sensor 103 from the intensities of the light with the third and fourth wavelengths output from the spectroscope 104.

  In addition, in the acceleration detection apparatus 100 according to the present embodiment, as shown in FIG. 1, the case where two acceleration sensors 102 and 103 are used is shown. However, when two acceleration sensors are used, the acceleration detection apparatus 100 It is not intended to limit the configuration of 100 or the method of detecting acceleration. There may be at least one acceleration sensor, and a plurality of acceleration sensors may be used as necessary. In the case of the acceleration detection apparatus 100 shown in FIG. 1, by installing the two acceleration sensors 102 and 103 at different parts of the object, it is possible to simultaneously measure the accelerations of the parts.

  Further, an optical fiber cable provided inside an acceleration sensor 102 and an acceleration sensor 103, which will be described later, is connected between the multi-wavelength light emitting device 101 and the acceleration sensor 102, between the acceleration sensor 102 and the acceleration sensor 103, and between the acceleration sensor 103 and the spectrometer 104. A series of optical fiber cables can be used.

  Hereinafter, the acceleration sensor 102 and the acceleration sensor 103 will be specifically described. Since the acceleration sensor 102 and the acceleration sensor 103 have the same structure, the acceleration sensor 102 will be described below as a representative.

FIG. 2 is a diagram illustrating a configuration example of the acceleration sensor 102 according to the present embodiment.
The acceleration sensor 102 includes a frame 201, an optical fiber cable 202, leaf springs 203 and 204, and weights 205 and 206.

  The frame 201 is a hollow structure housing that encompasses the entire acceleration sensor 102. The frame 201 is preferably a rigid body. As shown in FIG. 2, the frame 201 according to the present embodiment uses a rectangular parallelepiped having a hollow structure that does not have an upper surface and a lower surface facing in the z-axis direction.

  The optical fiber cable 202 is an optical fiber cable having an FBG portion subjected to FBG processing in a first section (between AB in FIG. 2) and a second section (between CD in FIG. 2). is there. By this FBG processing, in the first section, a part or all of the light having the first wavelength is reflected according to the stress applied to the core portion of the optical fiber cable 202. As a result, the light having the first wavelength is attenuated. . Similarly, in the second section, a part or all of the light having the second wavelength is reflected in accordance with the stress applied to the core portion, so that the light having the second wavelength is attenuated.

  A leaf spring 203 made of a resin such as polyimide is fixed to the optical fiber cable 202 along the first section. At this time, it is desirable that the leaf spring 203 is fixed so that the optical fiber cable 202 in the first section is held linearly.

  The fixed end of the first section, that is, the A end of the leaf spring 203 is such that the optical fiber cable 202 in the first section is parallel to the y axis and the plane formed by the leaf spring 203 and the xy plane are perpendicular to each other. The frame 201 is fixed.

  A vibration weight 205 is fixed to the free end of the first section, that is, the B end of the leaf spring 203. The B end to which the weight 205 is fixed vibrates in a certain range on the xy plane by the leaf spring 203. In the case of slight vibration, the B end to which the weight 205 is fixed can be approximated by vibrating in the x direction on the xy plane.

  A leaf spring 204 made of resin such as polyimide is fixed to the optical fiber cable 202 along the second section. At this time, it is desirable that the leaf spring 204 is fixed so that the optical fiber cable 202 in the second section is held linearly.

  The fixed end of the second section, that is, the C end of the leaf spring 204 is such that the optical fiber cable 202 in the second section is parallel to the x axis and the plane formed by the leaf spring 204 and the xy plane are perpendicular to each other. The frame 201 is fixed.

  A vibration weight 206 is fixed to the free end of the second section, that is, the D end of the leaf spring 203. The D end to which the weight 206 is fixed vibrates in a certain range on the xy plane by the leaf spring 204. In the case of slight vibration, the D end to which the weight 206 is fixed can be approximated by vibrating in the y direction on the xy plane.

The optical fiber cable 202 between the weight 205 and the weight 206 is covered with, for example, a soft resin in order to protect the optical fiber cable 202 from scratches and the like.
As shown in FIG. 2, in the FBG portion to which the weights 205 and 206 arranged facing each other on the line of the optical fiber cable 202 are attached, the vibration of one weight is applied to the FBG portion in the section to which the other weight is attached. When propagated, the vibration of each FBG part is affected by vibrations other than the regulated direction of each weight attached to each FBG part.

  For example, when the vibration of the weight 205 is propagated to the FBG portion of the second section to which the weight 206 is attached, the vibration of the FBG portion of the second section is vibration other than the y-axis direction of the weight 206, for example, x Affected by axial vibration.

  In this case, since a signal including vibrations other than the regulated direction is detected, there is a possibility that sensing accuracy may be reduced. Therefore, in the present embodiment, the length of the optical fiber cable 202 that connects adjacent FBG portions is long enough to prevent the vibration of one adjacent weight from being propagated to the vibration of the other weight.

  For example, the length of the optical fiber cable 202 connecting the adjacent FBG portions of the first section and the second section is such that the vibration of the weight 205 is in the FBG section of the second section or the vibration of the weight 206 is the first. A sufficient length is secured in the FBG portion of one section so as not to propagate.

  As described above, the acceleration sensor 102 is configured such that the length of the optical fiber cable that connects the FBG portions to which the weights are disposed facing each other on the line of the optical fiber cable is longer than at least the interval between adjacent weights. It can be.

  Note that “arranged to face each other on the line of the optical fiber cable 202” means, for example, “on the line of the optical fiber cable 202,” “the weight 205 faces the weight 205 from the end A to which the leaf spring 203 to which the weight 205 is attached is fixed. “Direction” and “direction in which the weight 206 is faced from the C end to which the leaf spring 204 to which the weight 206 is attached” are fixed.

  In the configuration described above, the leaf spring 203 and the leaf spring 204 can be cited as examples of beam members. Further, the A end and the C end can be cited as examples of the fixed end. The B end and D end can be cited as examples of free ends. The frame 201 can be cited as an example of a support member.

  The frame 201 is not an essential component for the acceleration sensor 102. Instead of the frame 201, for example, a part of an object on which the acceleration sensor 102 is installed can be used.

Further, the shape of the frame 201 is not necessarily the rectangular parallelepiped shown in FIG. 2, and may be various shapes such as a cylindrical shape, a polygonal shape, a spherical shape, a U-shape, and an arc shape.
Moreover, the optical fiber cable 202 does not need to be FBG-processed in all sections of the first section. For example, only a part of the first section needs to be FBG-processed. Similarly, in the optical fiber cable 202, all the sections of the second section do not have to be FBG-processed. For example, only a part of the second section needs to be FBG-processed.

  The leaf springs 203 and 204 may be fixed so that the optical fiber cable 202 penetrates the inside of the leaf springs 203 and 204. The leaf springs 203 and 204 are constituted by a plurality of leaf springs, and the optical fiber cable 202 is formed. You may fix so that it may pinch | interpose.

  The weights 205 and 206 may be fixed so that the optical fiber cable 202 penetrates the weights 205 and 206, or may be fixed so as to sandwich the optical fiber cable 202.

  In this embodiment, a resin such as polyimide is used as the material of the leaf springs 203 and 204, but the present invention is not limited to this. For example, steel, phosphor bronze, beryllium copper, rubber, synthetic resin, shape memory alloy or wood may be used as required.

  In the present embodiment, the leaf springs 203 and 204 are used, but the present invention is not limited to the leaf spring. For example, the leaf spring 203 is an example of a beam member for restricting and vibrating the weight 205 to a certain range on the xy plane, and the leaf spring 204 is for restricting and vibrating the weight 206 to a certain range on the xy plane. It is an example of a beam member. As the beam member, one having a major axis and a minor axis in a cross-sectional shape in a plane parallel to the axis of the beam member, that is, perpendicular to the longitudinal direction of the beam member can be used. Thereby, the vibration of the beam member can be limited in the minor axis direction.

  In the present embodiment, the optical fiber cable 202 in the first section is parallel to the y-axis, and the optical fiber cable 202 in the second section is parallel to the x-axis, that is, the longitudinal direction of the first section Although the case where the longitudinal direction of 2 section is orthogonal is illustrated, it is not the meaning limited to this. It is sufficient that the longitudinal direction of the first section and the longitudinal direction of the second section are different directions.

  FIG. 3 is a diagram for explaining the function of the first section of the optical fiber cable 202. FIG. 3 shows the vicinity of the first section of the optical fiber cable 202 viewed from the direction of the arrow Z shown in FIG. In addition, in order to ensure visibility, the leaf | plate spring 203 is abbreviate | omitted, However, It is not the meaning limited to the structure of FIG.

  When acceleration in the x direction is applied to the weight 205, the weight 205, that is, the B end vibrates in the direction of the arrow A shown in FIG. When the B end vibrates, the optical fiber cable 202 in the first section fixed to the leaf spring 203 is distorted together with the leaf spring 203 (not shown). At this time, the core portion of the optical fiber cable 202 is also distorted. Then, the refractive index of the core part also varies depending on the degree of distortion of the core part, that is, the degree of stress applied to the portion where the FBG processing of the core part is applied (FBG part).

  Therefore, for example, when multi-wavelength light is input to the optical fiber cable 202, the reflected light 301 reflected by the FBG portion in the first section changes from red to blue according to the vibration at the B end.

  Focusing only on the light of the first wavelength, the reflectance at which the light of the first wavelength input to the optical fiber cable 202 is reflected by the FGB in the first section varies according to the vibration at the B end. As a result, the light amount or intensity of the first wavelength light output from the acceleration sensor 102 through the first section of the optical fiber cable 202 varies according to the vibration at the B end.

  In FIG. 3, the function of the first section has been described, but the second section also passes through the second section of the optical fiber cable 202 and outputs from the acceleration sensor 102 by the same operation as the first section. The light quantity or intensity of the second wavelength light that varies is varied in accordance with the vibration at the D end.

FIG. 4 is a diagram for explaining the outline of the acceleration detection method using the acceleration sensor 102 according to this embodiment.
A waveform 401 shown in FIG. 4 shows the displacement of vibration of the weight 205 in the x-axis direction in time series. Similarly, the waveform 402 shows the vibration displacement of the weight 206 in the y-axis direction in time series.

  For example, when the weight 205 does not vibrate, the light having the first wavelength among the multi-wavelength light passing through the first section is reflected by the FBG section in the first section. However, when acceleration is applied to the weight 205 and it vibrates like the waveform 401, the reflectance at which the light of the first wavelength is reflected by the FBG portion in the first section varies. When the intensity of the light of the first wavelength at this time is detected, a waveform whose amplitude varies according to the variation in reflectance is obtained. Then, the acceleration in the x-axis direction among the accelerations applied to the acceleration sensor 102 can be obtained from the magnitude at which the central value of the amplitude of the waveform changes.

  Similarly, for example, when the weight 206 does not vibrate, the light having the second wavelength among the multi-wavelength light passing through the second section is reflected by the FBG section in the second section. However, when acceleration is applied to the weight 206 and vibrates like the waveform 402, the reflectance at which the light of the second wavelength is reflected by the FBG portion in the second section varies. When the intensity of the light of the first wavelength at this time is detected, a waveform whose amplitude varies according to the variation in reflectance is obtained. Then, the acceleration in the y-axis direction among the accelerations applied to the acceleration sensor 102 can be obtained from the magnitude at which the central value of the amplitude of the waveform changes.

  FIG. 5 is a diagram illustrating the center value of the amplitude of the intensity of the first and second wavelengths according to the present embodiment. In FIG. 5, as an example, a case will be described in which the vehicle installed with the acceleration sensor 102 that travels straight in the y-axis direction shown in FIG. 4 turns left while decelerating.

Note that the XY coordinates shown in FIG. 5 are a coordinate system in which the intensity of light of the first wavelength is taken on the X axis and the intensity of light of the second wavelength is taken on the Y axis.
When the vehicle traveling straight ahead is decelerated while turning left, the intensity of the first wavelength light and the intensity of the second wavelength light output from the acceleration sensor 102 oscillate around the point A (a, b), for example. To do.

  In this case, the intensity of the light having the first wavelength output from the acceleration sensor 102 oscillates in the X-axis direction around (a, 0). The value a of the X coordinate of the center (a, 0) of the amplitude in the X axis direction is the center value of the amplitude in the X axis direction.

  The intensity of the second wavelength light output from the acceleration sensor 102 oscillates in the Y-axis direction around (0, b). The Y-coordinate value b of the amplitude center (0, b) in the Y-axis direction is the center value of the amplitude in the Y-axis direction.

  When the vehicle is further decelerated from this state and the vehicle turns left, the intensity of the first wavelength light and the intensity of the second wavelength light output from the acceleration sensor 102 are, for example, points B (a ′, b ') Vibrates around. The center of the amplitude is displaced from A (a, b) to B (a ', b').

  In this case, the intensity of the light having the first wavelength output from the acceleration sensor 102 oscillates in the X-axis direction centering on (a ′, 0). The X coordinate value a ′ of the center (a ′, 0) of the amplitude in the X-axis direction is the center value of the amplitude in the X-axis direction.

  The intensity of the second wavelength light output from the acceleration sensor 102 oscillates in the Y-axis direction around (0, b '). The Y coordinate value b ′ of the amplitude center (0, b ′) in the Y-axis direction is the center value of the amplitude in the Y-axis direction.

  When the center of amplitude is displaced from A (a, b) to B (a ′, b ′), the center value of the amplitude in the X-axis direction changes by Δa = a′−a. From the magnitude Δa at which the central value of the amplitude changes, the acceleration in the x-axis direction shown in FIG. 4 among the accelerations applied to the acceleration sensor 102 can be obtained.

  Further, when the center of the amplitude is displaced from A (a, b) to B (a ′, b ′), the center value of the amplitude in the Y-axis direction changes by Δb = b′−b. The acceleration in the y-axis direction shown in FIG. 4 among the accelerations applied to the acceleration sensor 102 can be obtained from the magnitude Δb at which the center value of the amplitude changes.

FIG. 6 is a flowchart illustrating a specific example of acceleration detection processing using the acceleration sensor 102 according to the present embodiment.
In the process shown in FIG. 6, the acceleration sensor 102 is attached to the vehicle so that the coordinate system indicating the position of the acceleration sensor 102, that is, the xy plane of the xyz coordinate system shown in FIG. Shows about the case.

  When the multi-wavelength light emitting device 101 outputs multi-wavelength light including the first and second wavelengths to the acceleration sensor 102 and the computing device 105 is activated, an acceleration detection process is started (step S600).

  In step S601a, the arithmetic unit 105 acquires the intensity of the first wavelength light from the spectrometer 104. Note that the process of step S601a is performed a specified number of times in a certain period T. When the light intensity of the first wavelength is acquired from the spectroscope 104, the arithmetic device 105 stores the acquired light intensity of the first wavelength in a storage device or the like provided in the arithmetic device 105. Through the processing in step S601a, for example, discrete values of the waveform 701 shown in FIG. 7 can be acquired.

  In step S602a, the arithmetic unit 105 calculates the amplitude in the X-axis direction and the center thereof in the XY coordinates from the light intensity of the first wavelength acquired in the process in step S601a. For example, the center of the amplitude can be obtained from the average value of the light intensity of the first wavelength acquired in the process of step S601a. In addition, the amplitude can be obtained from the difference between the maximum value of the intensity of the light of the first wavelength acquired in the process of step S601a and the center.

  On the other hand, in step S601b, the arithmetic unit 105 acquires the intensity of the second wavelength light from the spectrometer 104. The process in step S601b is performed a specified number of times during a certain period T, as in step S601a. When the light intensity of the second wavelength is acquired from the spectroscope 104, the arithmetic device 105 stores the acquired light intensity of the second wavelength in a storage device or the like provided in the arithmetic device 105. With the processing in step S601b, for example, discrete values of the waveform 702 shown in FIG. 7 can be acquired.

  In step S602b, the arithmetic unit 105 calculates the amplitude in the Y-axis direction and the center thereof in the XY coordinates from the light intensity of the second wavelength acquired in the process of step S601b. For example, the center of the amplitude can be obtained from the average value of the light intensity of the second wavelength acquired in the process of step S601b. Further, the amplitude can be obtained from the difference between the maximum value of the light intensity of the second wavelength acquired in the process of step S601b and the center.

In step S603, the arithmetic unit 105 determines the X coordinate on the XY plane shown in FIG. 5 from the amplitude and center in the X-axis direction obtained in step S602a.
Further, the computing device 105 determines the Y coordinate on the XY plane shown in FIG. 5 from the amplitude and center in the Y-axis direction obtained in S602b.

In step S604, the arithmetic unit 105 calculates the acceleration from the magnitude at which the center value obtained in steps S602a and S602b changes.
In step S605, the arithmetic unit 105 calculates the current relative position (coordinates) of the vehicle based on the previously determined vehicle position from the acceleration calculated in step S604. The calculated relative position (coordinates) of the vehicle can be expressed by a vector representing the amount of movement from the previously determined position of the vehicle.

  In step S606, the arithmetic unit 105 obtains the absolute value of the relative position (coordinates) of the vehicle represented by the vector obtained in step S605. In this embodiment, for the sake of simplicity, the amount of change in the relative position of the vehicle is used as the “movement amount of the vehicle”.

In step S607, the arithmetic unit 105 calculates a difference C between the predetermined limit value and the vehicle movement amount obtained in step S606.
In the present embodiment, if the difference C is greater than 0 in step S608 (YES in step S608), the arithmetic unit 105 determines that it is normal and shifts the processing to steps S601a and S601b. If the difference C is 0 or less (NO in step S608), the arithmetic unit 105 determines that an abnormality has occurred and moves the process to step S609.

  In step S609, the arithmetic unit 105 performs operation control for avoiding an abnormality on the vehicle. For example, when the movement amount of the vehicle, which is estimated to cause an abnormality such as the vehicle tire slipping on the road surface, is designated as a limit value in advance, the arithmetic device 105 decelerates the vehicle speed in step S609. Perform operational control.

  In FIG. 6, the calculation device 105 is not limited to the case where it is determined that the calculation unit 105 is normal when the difference C is larger than 0 in step S608. As necessary, for example, when the difference C is smaller than 0, it may be determined to be normal.

  7 and 8 show the present embodiment as an example of visually grasping the acceleration / deceleration direction and magnitude based on the displacement amount / displacement direction of the center value of the amplitude on the XY plane shown in FIG. It is a figure explaining the case where a Lissajous curve is used for the detection method of the acceleration which concerns on.

  A waveform 701 shown in FIG. 7 shows the intensity of light of the first wavelength in the multi-wavelength light output from the acceleration sensor 102 in time series in association with the X-axis. Similarly, a waveform 702 shows the intensity of the second wavelength light among the multi-wavelength light output from the acceleration sensor 102 in time series in association with the Y axis.

  A Lissajous curve 703 can be obtained on the XY plane from the waveform 701 of the first wavelength light and the waveform 702 of the second wavelength light. The Lissajous curve 703 is, for example, circular or substantially circular as shown in FIG. The direction of the force applied to the sensor 102 can be determined by the displacement of the center point P of the Lissajous curve 703. Further, the acceleration applied to the sensor 102 can be obtained from the moving speed of the center point P.

  FIG. 8 shows the relationship between the motion of the object to which the sensor 102 is attached and the center point P of the XY coordinate system shown in FIG. The object to which the sensor 102 is attached is simply referred to as “object”. Further, the origin of the XY coordinate system shown in FIG.

  The Lissajous curves 801 to 807 shown in FIG. 8 place the sensor 102 on the object so that the coordinate system indicating the position of the acceleration sensor 102, that is, the xy plane of the xyz coordinate system shown in FIG. It shows the case of mounting. The movement of the object in the y-axis (+) direction is forward, and the movement of the object in the y-axis (−) direction is backward.

  Note that the xyz coordinate system is a coordinate system indicating the position of the sensor 102, that is, the object to which the sensor 102 is attached, and the XY coordinate system is a coordinate system indicating the Lissajous curve 703 shown in FIG. I want to be.

  The Lissajous curve 801 is an example of a Lissajous curve obtained when the object is in a stopped state or in a state where it is moving at a constant velocity. Therefore, for example, in the case of the Lissajous curve 801, the acceleration sensor 102 can detect a uniform motion.

  The Lissajous curve 802 is a Lissajous obtained when acceleration is applied to the object in the y-axis (+) direction, or when shifting from a constant velocity motion in the y-axis (−) direction to a deceleration motion. It is an example of a curve. Therefore, for example, in the case of the Lissajous curve 802, the acceleration sensor 102 can detect the acceleration motion of the object.

  The Lissajous curve 803 is a Lissajous obtained when acceleration is applied to the object in the y-axis (−) direction, or when moving from a constant-velocity motion in the y-axis (+) direction to a deceleration motion. It is an example of a curve. Therefore, for example, in the case of the Lissajous curve 803, the acceleration sensor 102 can detect the deceleration motion of the object.

  The Lissajous curve 804 is a Lissajous obtained when acceleration is applied to the object in the x-axis (−) direction, or when moving from a constant velocity motion in the x-axis (+) direction to a deceleration motion. It is an example of a curve. Therefore, for example, in the case of the Lissajous curve 804, the acceleration sensor 102 can detect the left turning motion of the object.

  The Lissajous curve 805 is a Lissajous obtained when acceleration is applied to the object in the x-axis (+) direction or when a transition is made from constant velocity motion in the x-axis (−) direction to deceleration motion. It is an example of a curve. Therefore, for example, in the case of the Lissajous curve 805, the acceleration sensor 102 can detect the right turning motion of the object.

  The Lissajous curve 806 is a state in which acceleration is applied to the object in the x-axis (−) direction and the y-axis (+) direction, or constant velocity motion in the x-axis (+) direction and the y-axis (−) direction. It is an example of a Lissajous curve obtained when it is in the state which shifted to deceleration movement from. Therefore, for example, in the case of the Lissajous curve 806, the acceleration sensor 102 can detect the left turning acceleration motion of the object.

  The Lissajous curve 807 is a state where acceleration is applied to the object in the x-axis (+) direction and the y-axis (+) direction, or constant velocity motion in the x-axis (−) direction and the y-axis (−) direction. It is an example of a Lissajous curve obtained when it is in the state which shifted to deceleration movement from. Therefore, for example, in the case of the Lissajous curve 807, the acceleration sensor 102 can detect the right turn acceleration motion of the object.

Below, the modification of the structure of the acceleration sensor 102 which concerns on a present Example is shown.
FIG. 9 is a diagram illustrating a first modification of the configuration of the acceleration sensor 102 according to the present embodiment.
The acceleration sensor 900 shown in FIG. 9 further includes a fixing member 901 in addition to the configuration shown in FIG.

  The fixing member 901 has one end of the fixing member 901 fixed to the frame 201 and the other end fixed to the optical fiber cable 202 between the weight 205 and the weight 206. The fixing member 901 is desirably a rigid body. The fixing member 901 prevents the vibration of the weight 205 from propagating to the second section and prevents the vibration of the weight 206 from propagating to the first section. That is, it is possible to suppress the vibration of the weights arranged facing each other from being propagated between adjacent FBG portions.

  FIG. 10 is a diagram illustrating a second modification of the configuration of the acceleration sensor 102 according to the present embodiment. An acceleration sensor 1000 shown in FIG. 10 uses a part 1001 of an object, for example, a frame such as an ECU (Engine Control Unit) or a part of a body of a vehicle body instead of the frame 201.

  The acceleration sensor 102 according to the present embodiment can be applied to an acceleration sensor that detects only acceleration in a specific direction. FIG. 11 shows a configuration example of an acceleration sensor that detects only acceleration in a specific direction.

The acceleration sensor 1100 includes a frame 1101, an optical fiber cable 1102, a leaf spring 1103, and a weight 1104.
The frame 1101 is a hollow housing that includes part or all of the acceleration sensor 1100. The frame 1101 is preferably a rigid body.

  The optical fiber cable 1102 is an optical fiber cable in which FBG processing is performed on the third section. By this FBG processing, in the third section, a part or all of the light having a specific wavelength is reflected according to the stress applied to the core portion of the optical fiber cable 1102, and as a result, the light having a specific wavelength is attenuated.

  A leaf spring 1103 made of resin such as polyimide is fixed to the optical fiber cable 1102 along the third section. At this time, it is desirable that the leaf spring 1103 is fixed so that the optical fiber cable 1102 in the third section is held linearly.

  The fixed end of the third section, that is, the E end of the leaf spring 1103 is such that the optical fiber cable 1102 in the third section is parallel to the x axis, and the plane formed by the leaf spring 1103 is parallel to the xy plane. The frame 1101 is fixed.

  A vibration weight 1104 is fixed to the free end of the third section, that is, the F end of the leaf spring 1103. The F end to which the weight 1104 is fixed vibrates in a certain range on the xz plane by the leaf spring 1103. In the case of minute vibrations, it can be approximated that the F end to which the weight 1104 is fixed vibrates in the z-axis direction.

  Therefore, only when the optical fiber cable 1102 receives acceleration in the z-axis direction, stress is generated in the core portion of the optical fiber cable 202 in the third section, and light of a specific wavelength is attenuated. At this time, by detecting the intensity of light of a specific wavelength output from the optical fiber cable 1102, it is possible to detect only the acceleration in a specific direction, for example, the z-axis direction.

  FIG. 12 is a diagram illustrating an application example of the acceleration sensor according to the present embodiment. In FIG. 12, the optical fiber cable connecting the sensors is omitted in order to prioritize the visibility of the arrangement of the sensors. However, the present invention is not limited to this.

  A three-axis sensor (yaw rate sensor) including the three acceleration sensors shown in FIG. 11 is attached to the vehicle 1200 shown in FIG. Of the three acceleration sensors shown in FIG. 12, the acceleration sensors 1201 and 1202 are used as turning sensors that detect acceleration when the vehicle turns, for example, acceleration in the z-axis direction shown in FIG. Hereinafter, the acceleration sensor 1201 is referred to as a “turn sensor 1201”, and the acceleration sensor 1202 is referred to as a “turn sensor 1202”.

  Of the three acceleration sensors shown in FIG. 12, the acceleration sensor 1203 is used as an acceleration sensor that detects the acceleration in the front-rear direction of the vehicle, for example, the acceleration in the x-axis direction shown in FIG.

Here, the turning sensor 1201 is disposed in front of the center of gravity G of the vehicle. Further, the turning sensor 1202 is arranged behind the center of gravity G of the vehicle. This is for the following reason.
When the vehicle turns normally, almost the same turning force is generated at any position of the vehicle. However, when the vehicle is in the slide / spin mode, the amount of turning force generated differs at the center of turning, that is, before and after the center of gravity of the vehicle. In this case, by disposing the turning sensors 1201 and 1202 before and after the center of gravity of the vehicle, it is possible to measure a difference in turning force and a difference in direction generated before and after the vehicle. As a result, the stability (yaw rate) during turning of the vehicle can be detected more easily.

  In the above description, in the acceleration detection method using the acceleration sensor according to the present embodiment, the case where the first to fourth light beams attenuated and output by the acceleration sensors 102 and 103 is used has been described. However, the acceleration detection method using the acceleration sensor according to the present embodiment can use reflected light reflected by the acceleration sensors 102 and 103. In this case, for example, light having a wavelength reflected in the first section of the acceleration sensor 102 may be set as light having the first wavelength, and light having a wavelength reflected in the second section may be set as the second wavelength.

  As described above, the acceleration sensors 102 and 103 according to the present embodiment are realized by the optical fiber cable 202, the leaf springs 203 and 204, and the weights 205 and 206, as shown in FIG. Can do. Thus, according to the present embodiment, the structure of the acceleration sensor can be simplified. Therefore, the acceleration sensor can be easily downsized.

  Further, for example, the acceleration detecting device 100 includes an optical fiber cable provided in the acceleration sensors 102 and 103, a multi-wavelength light emitting device 101-acceleration sensor 102, an acceleration sensor 102-acceleration sensor 103, and an acceleration sensor 103-spectrometer. The optical cable connecting between the 104 can be realized by a series of optical fiber cables. That is, it becomes possible to provide a plurality of acceleration sensors in one optical fiber cable.

  Thus, according to the present embodiment, the number of wirings does not increase even when a plurality of acceleration sensors and FBG sensors are used. Also, only one light source is required. As a result, it is possible to realize an acceleration detection device having a simple structure. Therefore, the acceleration detection device can be easily downsized.

  It should be noted that the weights may not be attached to all the FBG units, and for example, some FBG units may be used as known strain sensors or impact sensors. In that case, a weight may be attached to at least two or more FBG portions and used as a sensor of the present invention.

  In addition, the length of the optical fiber cable 202 connecting the FBG portions in adjacent sections is such that the vibration of the weight 205 is in the FBG section in the second section, or the vibration of the weight 206 is in the FBG section in the first section. Sufficient length is secured to prevent propagation. Thereby, it is possible to prevent the vibration of one weight from being propagated to the FBG portion of the section to which the other weight is attached. As a result, it is possible to prevent the vibrations of the FBG portions in the adjacent sections from being influenced by vibrations other than the restricted direction of the weight attached to each section.

  Further, the acceleration detection apparatus 100 calculates the acceleration from the difference between the point B (a ′, b ′) and the previously obtained point A (a, b) (step S604). As a result, the acceleration detection device does not require a device such as a circuit necessary for correction. Note that the point A can be said to be a point obtained in the past when the point in time when the point B is obtained is the current point. Therefore, according to the present embodiment, it can be said that acceleration is calculated from at least two points, such as the point B currently obtained and the point A obtained in the past. Further, the acceleration sensor 102 is arranged in a direction in which the longitudinal direction of the FBG portion in the first section is different from the longitudinal direction of the FBG section in the second section. In the present embodiment, since the longitudinal direction of the FBG portion in the first section and the longitudinal direction of the FBG section in the second section are arranged at 90 degrees different from each other, the longitudinal direction of the FBG section in the first section The acceleration in two dimensions determined by the longitudinal direction of the FBG portion in the second section can be detected.

  Moreover, it is not restricted to when the FBG part to which the weight was attached is arrange | positioned in a different direction. For example, the angle formed by the longitudinal direction of the FBG part in the first section and the longitudinal direction of the FBG part in the second section may be 180 degrees, that is, the longitudinal direction of at least two or more FBG parts. May be arranged in the same direction. In the FBG portions arranged in the same longitudinal direction, when the beam member is provided on a different side at least with respect to the FBG portion, different fluctuations on the same straight line can be detected.

  Further, for example, the leaf spring 203 of the acceleration sensor 102 is attached to the frame 201 so that the optical fiber cable 202 in the first section is parallel to the y axis and the plane formed by the leaf spring 203 and the xy plane are perpendicular to each other. It is fixed. Thereby, it is possible to limit the vibration of the optical fiber cable 202 in the first section within a certain range in the xy plane and approximately in the x-axis direction.

  Similarly, the leaf spring 204 of the acceleration sensor 102 is fixed to the frame 201 so that the optical fiber cable 202 in the second section is parallel to the x axis and the plane formed by the leaf spring 203 and the xy plane are perpendicular to each other. Has been. As a result, the vibration of the optical fiber cable 202 in the second section can be limited to a certain range in the xy plane and approximately in the y-axis direction.

  As a result, by using leaf springs in the first section and the second section of the acceleration sensor 102, for example, the acceleration sensor 102 installed parallel to the xy plane as shown in FIG. Only the acceleration applied to the x-axis direction and / or the y-axis direction can be detected without being affected by the applied acceleration.

  Further, by providing the fixing member 901 between the first section and the second section of the acceleration sensor 102, the vibration of the weight 205 is prevented from propagating to the second section, and the vibration of the weight 206 is prevented. Propagation to the first section can be prevented.

  By using the frame 201, the FBG part and the weight included in the acceleration sensor 102 can be attached to the object as one unit.

DESCRIPTION OF SYMBOLS 100 ... Acceleration detection apparatus 101 ... Multi-wavelength light-emitting device 102 ... Acceleration sensor 103 ... Acceleration sensor 104 ... Spectroscope 105 ... Arithmetic apparatus 110-112 ... Optical fiber cable 201 ..Frame 202 ... Optical fiber cable 203 ... Leaf spring 204 ... Leaf spring 205 ... Weight 206 ... Weight

Claims (10)

An optical fiber cable having a plurality of FBG parts processed by FBG (Fiber Bragg Grating);
A beam member provided along at least two or more of the FBG portions so as to be able to regulate the vibration direction of the weight, and fixed at a fixed end that is one end;
A weight attached to a free end that is the other end of at least two of the beam members;
With
The FBG portions are processed to different reflected light wavelengths,
A sensor characterized by that.   Among the FBG portions, when there is a pair of FBG portions arranged with the weights facing each other on a line of the optical fiber cable, the length of the optical fiber cable connecting the pair of FBG portions is: The sensor according to claim 1, wherein the sensor is longer than a linear interval between the weights attached to the pair of FBG portions. The FBG parts to which at least two or more weights are attached are arranged in different directions;
The sensor according to claim 1 or 2, wherein The FBG portion to which at least two or more weights are attached is disposed in a direction orthogonal to each other.
The sensor according to claim 3. The beam member is a member whose cross-sectional shape in a direction perpendicular to the direction along the FBG portion has a major axis and a minor axis.
The sensor of any one of Claims 1-4 characterized by the above-mentioned. A fixing member arranged between weights arranged facing each other on a line of the optical fiber cable and capable of fixing the optical fiber cable;
The sensor of any one of Claims 1-5 characterized by the above-mentioned. A support member for fixing the fixed end of the beam member;
The sensor of any one of Claims 1-6 characterized by the above-mentioned. A light source unit for inputting multi-wavelength light into the optical fiber cable;
An arithmetic unit for obtaining an output waveform from the FBG unit;
The sensor unit according to claim 1, further comprising:   A vehicle on which the sensor according to any one of claims 1 to 7 is mounted. The intensity of the wavelength displaced according to the vibration of the weight attached to the FBG portion among the wavelengths included in the multi-wavelength light output by the sensor according to claim 1 to 4 in the vibration direction of the weight. Detected as displacement of
Calculate the center position of vibration of the sensor from the displacement of the sensor,
A method of detecting an acceleration, wherein at least two or more center positions calculated at present or in the past are relatively compared, and an acceleration applied to the sensor is calculated from the comparison result.