Piezoelectric cable and detection system

Abstract

The present invention provides a piezoelectric cable and a detection system that can simplify the configuration of a detection system. [Solution] The piezoelectric cable 1 comprises an inner conductor 11, a polymer piezoelectric layer 12 that is in contact with the inner conductor 11 and surrounds the outer surface of the inner conductor 11, and an outer conductor 13 that is in contact with the polymer piezoelectric layer 12 and surrounds the outer surface of the polymer piezoelectric layer 12. The resistance value from one end to the other of one of the conductors, the inner conductor 11 or the outer conductor 13, is 10kΩ or more and 100GΩ or less.

Description

Technical Field

[0001] The present invention relates to a piezoelectric cable and a detection system.

Background Art

[0002] A piezoelectric cable in which a piezoelectric element is disposed between an inner conductor and an outer conductor surrounding the inner conductor is known. When a force is applied to the outer peripheral surface of the piezoelectric cable, the piezoelectric cable can detect the polarization of the piezoelectric element through the inner conductor and the outer conductor. A detection system that uses a plurality of such piezoelectric cables to detect the position of a force applied to a measurement object is known, and Patent Document 1 below describes such a detection system.

[0003] The detection system of Patent Document 1 below includes a plurality of piezoelectric cables provided along a plate material of a bed, and a detection unit that is electrically connected to each of the piezoelectric cables and to which a voltage output output from each of the piezoelectric cables is input. The detection unit detects where a force is applied to the bed based on the voltage output from each piezoelectric cable. According to such a detection system, it is said that it is possible to detect where a person is located on the bed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the detection system described in Patent Document 1 above, each of a plurality of piezoelectric cables is electrically connected to a detection unit. Therefore, there is a demand to reduce the number of piezoelectric cables and simplify the configuration of the detection system.

[0006] Therefore, the present invention aims to provide a piezoelectric cable and a detection system that can simplify the configuration of a detection system. [Means for solving the problem]

[0007] One aspect of the present invention is a piezoelectric cable comprising an inner conductor, a polymer piezoelectric layer in contact with the inner conductor and surrounding the outer surface of the inner conductor, and an outer conductor in contact with the polymer piezoelectric layer and surrounding the outer surface of the polymer piezoelectric layer, wherein the resistance value from one end to the other of one of the inner conductor and the outer conductor is 10 kΩ or more and 100 GΩ or less.

[0008] When a portion of the piezoelectric cable in Embodiment 1 is pressed, a voltage is generated between the inner conductor and the outer conductor at the pressed position. If the section of the piezoelectric cable from the pressed position to one end is considered the first section, the resistance of one conductor in the first section decreases as the pressed position approaches one end. Therefore, the closer the pressed position is to one end, the greater the voltage at one end of one conductor. However, if the resistance of one conductor from one end to the other is greater than 100 GΩ, the voltage is excessively attenuated by one conductor, so for example, when the pressed position is close to the other end, the voltage at one end of one conductor becomes too small and difficult to detect. Also, if the resistance of one conductor from one end to the other is less than 10 kΩ, the voltage attenuation by one conductor becomes too small. Therefore, the change in voltage at one end of one conductor due to a change in the pressed position becomes too small, making it difficult to distinguish between different pressed positions. In Embodiment 1, as described above, the resistance value from one end to the other of one conductor is between 10 kΩ and 100 GΩ. Therefore, the position of pressure along the longitudinal direction of the piezoelectric cable can be detected by the electrical output from one end of one conductor. For this reason, the detection unit for detecting the pressure position in the piezoelectric cable only needs to be connected to at least one end of one conductor of the piezoelectric cable. Thus, according to Embodiment 1, even with a single piezoelectric cable, the position of pressure on the object being measured can be detected, and the configuration of the detection system can be simplified.

[0009] Aspect 2 of the present invention is a detection system comprising: a piezoelectric cable having an internal conductor, a polymer piezoelectric layer in contact with the internal conductor and surrounding the outer surface of the internal conductor, and an external conductor in contact with the polymer piezoelectric layer and surrounding the outer surface of the polymer piezoelectric layer, wherein the resistance value from one end to the other of one of the internal conductor and the external conductor is 10 kΩ or more and 100 GΩ or less; a ground wire electrically connected to the other of the internal conductor and the external conductor; and a detection unit, wherein the detection unit includes a first input unit electrically connected to one end of the one conductor and receiving an electrical output output from the one conductor; and a detection unit that detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical output received from the first input unit.

[0010] In Embodiment 2, the other conductor of the inner and outer conductors in the piezoelectric cable of Embodiment 1 is connected to the ground wire. As described above, the closer the pressed position in the piezoelectric cable is to one end, the greater the voltage at one end of that conductor. The first input unit of the detection unit is electrically connected to one end of such a conductor and receives the electrical output from that conductor as input. Based on the electrical output received from the first input unit, the detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable. Therefore, according to Embodiment 2, it is possible to detect the pressed position in the object under test even with a single piezoelectric cable. Accordingly, Embodiment 2 can simplify the configuration of the detection system.

[0011] A third aspect of the present invention is a detection system according to aspect 2, wherein the detection unit further includes a second input unit which is electrically connected to the other end of the one conductor and to which an electrical output output from the one conductor is input, and the detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical outputs input from the first input unit and the second input unit.

[0012] If the section from the pressed position to the other end of the piezoelectric cable is defined as the second section, the resistance of one conductor in the second section increases as the pressed position approaches one end. Therefore, unlike the voltage at the other end of one conductor, the voltage at the other end of one conductor changes so that it decreases as the pressed position approaches one end. In embodiment 3, the detection unit detects the pressed position based on the electrical output from one end of one conductor and the other end of the other conductor. Therefore, according to embodiment 3, the accuracy of position detection can be improved.

[0013] Aspect 4 of the present invention is a detection system comprising: a piezoelectric cable having an internal conductor, a polymer piezoelectric layer in contact with the internal conductor and surrounding the outer surface of the internal conductor, and an external conductor in contact with the polymer piezoelectric layer and surrounding the outer surface of the polymer piezoelectric layer, wherein the resistance value from one end to the other of one of the internal conductor and the external conductor is 10 kΩ or more and 100 GΩ or less; and a detection unit, wherein the detection unit includes a first input unit that is individually electrically connected to one end of the one conductor and one end of the other of the internal conductor and the external conductor and receives electrical outputs output from the one conductor and the other conductor; and a detection unit that detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical outputs received from the first input unit.

[0014] In Embodiment 4, the first input unit of the detection unit is electrically connected to one end of one conductor and the other conductor of the piezoelectric cable in Embodiment 1, and receives the electrical outputs from one conductor and the other conductor. The detection unit of the detection unit then detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical outputs received from the first input unit. Therefore, according to Embodiment 4, similar to Embodiment 2, it is possible to detect the pressed position on the object to be measured even with a single piezoelectric cable, and the configuration of the detection system can be simplified.

[0015] Aspect 5 of the present invention is a detection system according to aspect 4, wherein the detection unit further includes a second input unit which is individually electrically connected to the other ends of the one conductor and the other conductor and to which the electrical outputs output from the one conductor and the other conductor are input, and the detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical outputs input from the first input unit and the second input unit.

[0016] According to Embodiment 5, similar to Embodiment 3, the accuracy of detecting the pressed position in the longitudinal direction of the piezoelectric cable can be improved.

[0017] Aspect 6 of the present invention is a detection system according to any one of aspects 2 to 5, characterized in that the detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable based on the period from when the electrical output reaches a first reference value until it reaches a second reference value that is higher than the first reference value.

[0018] Aspect 7 of the present invention is a detection system according to any one of aspects 2 to 6, characterized in that the electrical output is a voltage.

[0019] Aspect 8 of the present invention is a detection system according to any one of aspects 2 to 6, characterized in that the electrical output is electric charge.

[0020] Aspect 9 of the present invention is a detection system according to any one of aspects 2 to 8, characterized in that the detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable using a learning model constructed by machine learning the electrical output.

[0021] According to embodiment 9, the accuracy of detecting the pressed position in the longitudinal direction of the piezoelectric cable can be improved.

[0022] Aspect 10 of the present invention is the detection system according to any one of Aspects 2 to 9, characterized in that the piezoelectric cable is arranged along a plane in the object to be measured, and the piezoelectric cable has a curved portion that curves.

[0023] According to Aspect 10, it is possible to detect where a force is applied on the plane of the object to be measured.

[0024] Aspect 11 of the present invention is the detection system according to any one of Aspects 2 to 9, characterized in that the piezoelectric cable is arranged along a curved surface in the object to be measured.

[0025] According to Aspect 11, it is possible to detect where a force is applied on the curved surface of the object to be measured.

Advantages of the Invention

[0026] As described above, according to the present invention, there are provided a piezoelectric cable capable of realizing simplification of the configuration of the detection system, and a detection system.

Brief Description of the Drawings

[0027] [Figure 1] It is a diagram schematically showing the detection system according to the first embodiment. [Figure 2] It is a diagram showing the structure of the piezoelectric cable shown in FIG. 1. [Figure 3] It is a cross-sectional view of the piezoelectric cable. [Figure 4] It is a diagram for explaining the arrangement of the piezoelectric cable in the first embodiment. [Figure 5] It is a diagram showing an example of the voltage measured by the measurement unit when a part of the piezoelectric cable is pressed from the outer peripheral surface. [Figure 6] It is a diagram showing, in the same manner as FIG. 5, an example of the voltage measured by the measurement unit when another part of the piezoelectric cable is pressed from the outer peripheral surface. [Figure 7] It is a diagram showing an example of the charge measured by the measurement unit when a part of the piezoelectric cable is pressed from the outer peripheral surface. [Figure 8] This figure, similar to Figure 7, shows an example of the electric charge measured at the measuring unit when another part of a piezoelectric cable is pressed from its outer surface. [Figure 9] This figure shows the period including the rise of the charge input from the first input unit shown in Figure 7, and the period including the rise of the charge input from the first input unit shown in Figure 8. [Figure 10] This figure shows the detection system according to the fourth embodiment, similar to Figure 1. [Figure 11] This diagram illustrates the arrangement of piezoelectric cables in a modified example. [Figure 12] This diagram illustrates the arrangement of piezoelectric cables in another modified example. [Modes for carrying out the invention]

[0028] Preferred embodiments of the piezoelectric cable and detection system according to the present invention will be described in detail below with reference to the figures. The embodiments illustrated below are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention can be modified and improved from the following embodiments within the scope of the claims without departing from its spirit. For ease of understanding, the scale of each figure may differ from the scale described in the following description.

[0029] (First Embodiment) Figure 1 is a schematic diagram showing the detection system according to this embodiment. As shown in Figure 1, the detection system 100 of this embodiment mainly comprises a piezoelectric cable 1, amplifiers 45 and 46, a detection unit 50, a memory 60, and a monitor 70.

[0030] First, the piezoelectric cable 1 will be described. Figure 2 is a diagram showing the structure of the piezoelectric cable 1 shown in Figure 1, and Figure 3 is a cross-sectional view of the piezoelectric cable 1. As shown in Figures 2 and 3, the piezoelectric cable 1 of this embodiment includes an inner conductor 11, a polymer piezoelectric layer 12, an outer conductor 13, and a protective layer 15. The length of the piezoelectric cable 1 is, for example, 0.1m or more and 20m or less, but is not limited. Note that the protective layer 15 is not shown in Figure 1.

[0031] The internal conductor 11 is a linear conductor. In this embodiment, the internal conductor 11 is made of a high-resistance material, and the resistance value from one end to the other in the longitudinal direction is 10 kΩ or more and 100 GΩ or less. Examples of high-resistance materials include tyranno fiber, aramid fiber, carbon fiber, conductive silicone rubber, glass fiber, nickel-chromium alloy, etc. In this embodiment, the resistance value per unit length of the internal conductor 11 is generally constant in the longitudinal direction. The resistance value per unit length of the internal conductor 11 is preferably 10 kΩ / m or more and 10 GΩ / m or less, and more preferably 1 MΩ / m or more and 1 GΩ / m or less. In this embodiment, the internal conductor 11 is a stranded wire in which multiple conductors are twisted together. The internal conductor 11 may also be a conductor made of a single wire made of a high-resistance material.

[0032] The polymer piezoelectric layer 12 is a layer that is in contact with the internal conductor 11 and surrounds the outer surface of the internal conductor 11. The polymer piezoelectric layer 12 is made of a polymer that exhibits piezoelectric properties, and examples of such polymers include polyvinylidene fluoride (PVDF), polylactic acid, polyurea, etc. The polymer piezoelectric layer 12 in this embodiment is a cylindrical member formed by extrusion molding or the like, and the outer shape of the cross-section is approximately circular. The polymer piezoelectric layer 12 may also be configured by winding a tape-like film made of polymer piezoelectric material around the internal conductor 11, in which case the film may be wound in a spiral or longitudinal pattern.

[0033] The outer conductor 13 is a conductor that is in contact with the polymer piezoelectric layer 12 and surrounds the outer surface of the polymer piezoelectric layer 12. The outer conductor 13 in this embodiment may be a conductor with higher conductivity than the high-resistance material mentioned above, and such a conductor may be made of copper, aluminum, tin-plated soft copper alloy, etc. Therefore, the resistance value of the outer conductor 13 from one end to the other in the longitudinal direction is smaller than the resistance value of the inner conductor 11 from one end to the other in the longitudinal direction. The resistance value of the outer conductor 13 from one end to the other in the longitudinal direction is preferably 1 kΩ or less. The outer conductor 13 in this embodiment is configured with multiple wires wound spirally in the same direction. The outer conductor 13 may also be a braided wire made of multiple wires.

[0034] The protective layer 15 of this embodiment includes an insulating layer 16, a shielding layer 17, and a jacket layer 18. The insulating layer 16 is an insulator that covers the outer surface of the outer conductor 13. The insulating layer 16 of this embodiment consists of an inner insulating layer 16a and an outer insulating layer 16b.

[0035] The inner insulating layer 16a consists of a tape-shaped film 16at made of an insulating resin, and the film 16at is spirally wound on the outer surface of the outer conductor 13. No adhesive layer is provided on any surface of the film 16at, and the inner insulating layer 16a is not adhered to the outer conductor 13. The material of the film 16at is not particularly limited, but examples include insulating resins such as polyethylene terephthalate, polyethylene naphthalate, polyimide, polyvinyl chloride, polypropylene, polyetheretherketone, polyetherimide, and polyphenylene sulfide. An adhesive layer may be provided on one surface of the film 16at.

[0036] The outer insulating layer 16b is the outermost layer of the insulating layer 16 and consists of a tape-shaped film 16bt made of an insulating resin and an adhesive layer 16ba provided on one surface of the film 16bt. The film 16bt is wound spirally on the outer surface of the inner insulating layer 16a with the adhesive layer 16ba facing the inner insulating layer 16a. Therefore, the adhesive layer 16ba is in contact with the inner insulating layer 16a, and the film 16bt is bonded to the inner insulating layer 16a by the adhesive layer 16ba. In this embodiment, the film 16bt of the outer insulating layer 16b is wound in the same direction as the film 16at of the inner insulating layer 16a, but it may be wound in the opposite direction to the film 16at. Also, at least one of the film 16at and the film 16bt may be wound longitudinally. The material of the film 16bt is not particularly limited, but for example, it can be the same material as the film 16at. The adhesive used in the adhesive layer 16ba is not particularly limited, but examples include acrylic adhesives, polyester adhesives, polyamide adhesives, and ethylene vinyl acetate copolymer (EVA) adhesives.

[0037] Furthermore, the adhesive layer 16ba may be omitted. Alternatively, one of the inner insulating layer 16a and the outer insulating layer 16b may be omitted, and the insulating layer 16 may consist of either the inner insulating layer 16a or the outer insulating layer 16b.

[0038] The shield layer 17 is a conductor that surrounds the outer surface of the insulator layer 16. The shield layer 17 is not particularly limited as long as it is made of a conductor, but for example, it is made of a conductor similar to the outer conductor 13. In this embodiment, the shield layer 17 is configured in which multiple conductors are wound spirally in the same direction. The shield layer 17 may also be a braided wire in which multiple conductors are woven together.

[0039] The jacket layer 18 is a layer that covers the outer surface of the shield layer 17. In this embodiment, the jacket layer 18 has an inner jacket layer 18a and an outer jacket layer 18b.

[0040] The inner jacket layer 18a consists of a tape-shaped film 18at made of resin, and the film 18at is wound spirally on the outer surface of the shield layer 17. No adhesive layer is provided on any surface of the film 18at, and the inner jacket layer 18a is not adhered to the shield layer 17. The material of the film 18at is not particularly limited, but for example, it can be the same material as the film 16at. An adhesive layer may be provided on one surface of the film 18at.

[0041] The outer jacket layer 18b is the outermost layer of the jacket layer 18 and is located on the outermost periphery of the piezoelectric cable 1. The outer jacket layer 18b consists of a tape-shaped film 18bt made of resin and an adhesive layer 18ba provided on one surface of the film 18bt. The film 18bt is wound spirally on the outer circumferential surface of the inner jacket layer 18a with the adhesive layer 18ba facing the inner jacket layer 18a. Therefore, the adhesive layer 18ba is in contact with the inner jacket layer 18a, and the film 18bt is adhered to the inner jacket layer 18a by the adhesive layer 18ba. In this embodiment, the film 18bt of the outer jacket layer 18b is wound in the same direction as the film 18at of the inner jacket layer 18a, but it may be wound in the opposite direction to the film 16at. Also, at least one of the film 18at and the film 18bt may be wound longitudinally. The material of film 18bt is not particularly limited, but for example, it can be a material similar to that of film 18at. The adhesive used in adhesive layer 18ba is not particularly limited, but for example, it can be an adhesive similar to that used in adhesive layer 18ba.

[0042] The inner jacket layer 18a may be omitted, and the jacket layer 18 may be composed of the outer jacket layer 18b.

[0043] In a piezoelectric cable 1 with this configuration, when the piezoelectric cable 1 is pressed from its outer surface, the polymer piezoelectric layer 12 deforms, causing polarization in the polymer piezoelectric layer 12, and a voltage is generated between the inner conductor 11 and the outer conductor 13 at the pressed position.

[0044] Figure 4 illustrates the arrangement of the piezoelectric cable 1 in this embodiment. As shown in Figure 4, the piezoelectric cable 1 in this embodiment is placed on the seat surface 111 of the bench 110, which is the object to be measured. The seat surface 111 is a long plane in the left-right direction, and the piezoelectric cable 1 is arranged in a roughly straight line along the seat surface 111, with its longitudinal direction aligned with the longitudinal direction of the seat surface 111. The piezoelectric cable 1 is also covered by a resin protective sheet 112. In the bench 110 with the piezoelectric cable 1 arranged in this way, the position where the piezoelectric cable 1 is pressed in the longitudinal direction changes depending on the seating position of the person. In Figure 4, the protective sheet 112 is shown by a dotted line.

[0045] Returning to Figure 1, let's explain the detection unit 50.

[0046] The detection unit 50 consists of, for example, an integrated circuit such as a microcontroller, IC (Integrated Circuit), LSI (Large-scale Integrated Circuit), or ASIC (Application Specific Integrated Circuit), or an NC (Numerical Control) device. The detection unit 50 may or may not use a machine learning machine. The detection unit 50 is electrically connected to the piezoelectric cable 1, the memory 60, and the monitor 70.

[0047] The memory 60 is configured to store information and to be readable. The memory 60 is, for example, a non-transitory recording medium, and semiconductor recording media such as RAM (Random Access Memory) or ROM (Read Only Memory) are preferred, but any type of recording medium such as optical recording media or magnetic recording media may be included. Note that "non-transitory" recording media include all computer-readable recording media except transient propagation signals, and do not exclude volatile recording media. The memory 60 and the detection unit 50 may be provided in a single package. The memory 60 stores various programs for controlling some of the configurations of the detection unit 50 and generating information, as well as data necessary for generating information. The detection unit 50 reads the programs and information stored in the memory 60. The memory 60 also stores information, etc., based on instructions from the detection unit 50.

[0048] The detection unit 50 of this embodiment includes a first input unit 51, a second input unit 52, a measurement unit 53, a detection unit 54, and an output unit 55, each of which is electrically connected via a bus line.

[0049] The first input unit 51 of this embodiment has terminals 51a and 51b. Terminal 51a is electrically connected to the internal conductor 11 at one end of the piezoelectric cable 1 via the amplifier 45, and terminal 51b is electrically connected to the external conductor 13 at the other end of the piezoelectric cable 1 via the amplifier 45. In other words, the first input unit 51 is electrically connected to one end each of the internal conductor 11 and the external conductor 13. These terminals 51a and 51b are electrically connected to the measuring unit 53 individually.

[0050] The second input unit 52 of this embodiment has terminals 52a and 52b. Terminal 52a is electrically connected to the internal conductor 11 at the other end of the piezoelectric cable 1 via amplifier 46, and terminal 52b is electrically connected to the external conductor 13 at the other end of the piezoelectric cable 1 via amplifier 46. In other words, the second input unit 52 is electrically connected individually to the other ends of the internal conductor 11 and the external conductor 13. These terminals 52a and 52b of the second input unit 52 are electrically connected individually to the measuring unit 53.

[0051] In this embodiment, the measuring unit 53 is electrically connected individually to one end of the inner conductor 11 and the outer conductor 13 via the first input unit 51 and amplifier 45, and electrically connected individually to the other end of the inner conductor 11 and the outer conductor 13 via the second input unit 52 and amplifier 46. When force is applied to the piezoelectric cable 1, the measuring unit 53 receives the voltage output from one end of the inner conductor 11 and the outer conductor 13, and the voltage output from the other end of the inner conductor 11 and the outer conductor 13, which are amplified by amplifiers 45 and 46, respectively, as electrical outputs from the piezoelectric cable 1. In other words, the voltage output from one end of the inner conductor 11 and the outer conductor 13 is amplified and input to the first input unit 51, and the voltage output from the other end of the inner conductor 11 and the outer conductor 13 is amplified and input to the second input unit 52. The measuring unit 53 is a voltmeter that measures the respective voltages input from the first input unit 51 and the second input unit 52 in this manner. The measurement unit 53 outputs a signal related to the measured voltage, and this signal is input to the detection unit 54 via the bus line.

[0052] The detection unit 54 detects the pressed position in the longitudinal direction of the piezoelectric cable 1. As shown in Figure 1, in this embodiment, the detection unit 54 detects which of the three sections SEa, SEb, and SEc, obtained by dividing the piezoelectric cable 1 into three longitudinal sections, is located in the pressed position P. The lengths of these sections SEa, SEb, and SEc are approximately the same. Section SEa is the section that includes one end of the piezoelectric cable 1. Section SEc is the section that includes the other end of the piezoelectric cable 1. Section SEb is the section sandwiched between sections SEa and SEc and connected to sections SEa and SEc.

[0053] When a portion of the piezoelectric cable 1 is pressed, a voltage is generated between the internal conductor 11 and the external conductor 13 at the pressed position P. If the section of the piezoelectric cable 1 from the pressed position P to one end is called the first section SE1, then the first section SE1 becomes shorter as the pressed position P approaches one end. Similarly, if the section from the pressed position P to the other end is called the second section SE2, then the second section SE2 becomes longer as the pressed position P approaches one end. Therefore, the resistance of the internal conductor 11 in the first section SE1 decreases as the pressed position P approaches one end, and the voltage at one end of the internal conductor 11 increases. Conversely, the resistance of the internal conductor 11 in the second section SE2 increases as the pressed position P approaches one end, and the voltage at one end of the internal conductor 11 decreases.

[0054] Figure 5 shows an example of the voltage measured by the measuring unit 53 when a portion of the piezoelectric cable 1 is pressed from the outer surface. It is a diagram showing an example of the voltage when the approximately central part of the longitudinal direction of section SEa of the piezoelectric cable 1 is pressed from the outer surface with a predetermined force for a predetermined period of time. In Figure 5, the voltage V1 input from the first input unit 51 and the voltage V2 input from the second input unit 52 are shown side by side. The polymer piezoelectric layer 12 of the piezoelectric cable 1 becomes polarized due to the piezoelectric effect when it is deformed, and the polarization disappears after deformation. Therefore, at the moment a force is applied to the piezoelectric cable 1, a voltage is generated between the inner conductor 11 and the outer conductor 13 of the piezoelectric cable 1 at the position where the force is applied. During the period when a constant force is applied to the piezoelectric cable 1, there is no voltage between the inner conductor 11 and the outer conductor 13. At the moment the force on the piezoelectric cable 1 is stopped, a voltage is generated between the inner conductor 11 and the outer conductor 13, and thereafter, there is no voltage between the inner conductor 11 and the outer conductor 13. Therefore, as shown in Figure 5, the voltages V1 and V2 have waveforms with positive and negative peaks. Here, the pressed position P in the piezoelectric cable 1 is one end away from the center in the longitudinal direction of the piezoelectric cable 1, and the first section SE1 is shorter than the second section SE2. Therefore, the resistance value of the internal conductor 11 in the first section SE1 is smaller than the resistance value of the internal conductor 11 in the second section SE2, and the absolute value of the peak of voltage V1 is larger than the absolute value of the peak of voltage V2.

[0055] Figure 6 shows an example of the voltage measured by the measuring unit 53 when another part of the piezoelectric cable 1 is pressed from the outer surface, similar to Figure 5. The force and duration of pressure applied to the piezoelectric cable 1 are approximately the same as the force and duration applied when the voltage shown in Figure 5 was measured. The pressed position P of the piezoelectric cable 1 is approximately in the longitudinal center of section SEb of the piezoelectric cable 1, and the first section SE1 and the second section SE2 are approximately the same length. Therefore, the resistance value of the internal conductor 11 in the first section SE1 is approximately the same as the resistance value of the internal conductor 11 in the second section SE2, and the absolute value of the peak of voltage V1 is approximately the same as the absolute value of the peak of voltage V2. Furthermore, the absolute values ​​of the peaks of voltages V1 and V2 are smaller than the absolute value of the peak of voltage V1 shown in Figure 5, and larger than the absolute value of the peak of voltage V2 shown in Figure 5.

[0056] Thus, the closer the pressed position P is to one end of the piezoelectric cable 1, the larger the voltage V1 input to the first input unit 51 becomes, and the smaller the voltage V2 input to the second input unit 52 becomes. The detection unit 54 of this embodiment detects the section in which the pressed position P of the piezoelectric cable 1 is located, based on the voltages V1 and V2 measured by the measurement unit 53, that is, the voltages V1 and V2 input from the first input unit 51 and the second input unit 52. More specifically, information showing the relationship between the maximum values ​​of voltages V1 and V2 and the pressed position P is stored in the memory 60 in advance, and the detection unit 54 refers to this information based on the intensity of the voltages V1 and V2 input from the first input unit 51 and the second input unit 52, and detects the section in which the pressed position P of the piezoelectric cable 1 is located. Note that the method of detecting the section in which the pressed position P is located based on the intensity of voltages V1 and V2 is not limited to the method described above. For example, the detection unit 54 may detect the section in which the pressed position P is located based on the ratio V1 / V2 of the maximum value of voltage V1 to the maximum value of voltage V2. The ratio V1 / V2 increases as the pressed position P is closer to one end of the piezoelectric cable 1. For this reason, for example, information showing the relationship between the ratio V1 / V2 and the pressed position P is stored in the memory 60 in advance. Then, the detection unit 54 refers to this information based on the ratio V1 / V2 and detects the section in which the pressed position P is located. Alternatively, the detection unit 54 may detect the section in which the pressed position P is located based on the ratio V1 / V2 and the ratio V2 / V1 of the maximum value of voltage V2 to the maximum value of voltage V1.

[0057] The detection unit 54 outputs a signal related to the detection result, and this signal is output to the monitor 70 from the output unit 55 via the bus line.

[0058] The monitor 70 displays information corresponding to the detection result signal input from the output unit 55, for example. Note that the monitor 70 is not an essential component of the detection system 100.

[0059] As described above, the piezoelectric cable 1 in this embodiment is placed on the seat surface 111 of the bench 110, which is the object to be measured. Therefore, the detection system 100 in this embodiment can detect, for example, where on the bench 110 a person is sitting by detecting the section in which the pressed position P by the detection unit 54 is located.

[0060] As described above, the piezoelectric cable 1 of this embodiment comprises an inner conductor 11, a polymer piezoelectric layer 12 that is in contact with the inner conductor 11 and surrounds the outer surface of the inner conductor 11, and an outer conductor 13 that is in contact with the polymer piezoelectric layer 12 and surrounds the outer surface of the polymer piezoelectric layer 12. The resistance value of the inner conductor 11 from one end to the other is 10 kΩ or more and 100 GΩ or less.

[0061] As described above, when a part of the piezoelectric cable 1 is pressed, a voltage is generated between the inner conductor 11 and the outer conductor 13 at the pressed position P. The resistance of the inner conductor 11 in the first section SE1 from the pressed position P to one end of the piezoelectric cable 1 decreases as the pressed position P approaches one end. Therefore, the closer the pressed position P is to one end, the greater the voltage at one end of the inner conductor 11. Here, if the resistance value from one end to the other end of the inner conductor 11 is greater than 100 GΩ, the voltage is excessively attenuated by the inner conductor 11, and for example, when the pressed position P is close to the other end, the voltage at one end of the inner conductor 11 becomes too small, making detection difficult. Also, if the resistance value from one end to the other end of the inner conductor 11 is less than 10 kΩ, the voltage attenuation by the inner conductor 11 becomes too small. Therefore, the change in voltage at one end of the inner conductor 11 due to the change in the pressed position P becomes too small, making it difficult to distinguish between different pressed positions P. In the piezoelectric cable 1 of this embodiment, as described above, the resistance value from one end to the other of the internal conductor 11 is 10kΩ or more and 100GΩ or less. Therefore, the pressed position P in the longitudinal direction of the piezoelectric cable 1 can be detected by the electrical output from one end of the internal conductor 11. For this reason, at least one end of the internal conductor 11 of the piezoelectric cable 1 needs to be connected to the detection unit that detects the pressed position P in the piezoelectric cable 1. For this reason, the piezoelectric cable 1 of this embodiment can detect the pressed position on the object to be measured even with just one piezoelectric cable 1, and the configuration of the detection system can be simplified. In addition, from the viewpoint of making it easier to detect the pressed position P, it is preferable that the resistance value from one end to the other of the internal conductor 11 is 1MΩ or more and 1GΩ or less.

[0062] The detection system 100 of this embodiment comprises the piezoelectric cable 1 described above, and a detection unit 50 including a first input unit 51, a second input unit 52, and a detection unit 54. As described above, the resistance value of the internal conductor 11 in the second section SE2 from the pressed position P to the other end of the piezoelectric cable 1 increases as the pressed position P approaches one end. Therefore, the voltage at the other end of the internal conductor 11 changes to become smaller as the pressed position P approaches one end, unlike the voltage at one end of the internal conductor. In the detection system 100 of this embodiment, the first input unit 51 is electrically connected to one end of the internal conductor 11 and one end of the external conductor 13 individually, and the voltage V1 output from the internal conductor 11 and the external conductor 13 is input. The second input unit 52 is electrically connected to the other end of the internal conductor 11 and the other end of the external conductor 13 individually, and the voltage V2 output from the internal conductor 11 and the external conductor 13 is input. The detection unit 54 detects the pressed position P in the longitudinal direction of the piezoelectric cable 1 based on the voltages V1 and V2 input from the first input unit 51 and the second input unit 52. Therefore, according to the detection system 100 of this embodiment, even with a single piezoelectric cable 1, the pressed position on the object to be measured can be detected, and the configuration of the detection system 100 can be simplified.

[0063] In this embodiment, the detection unit 54 detects the pressed position P of the piezoelectric cable 1 based on the voltages V1 and V2 input from the first input unit 51 and the second input unit 52. However, the detection unit 54 may also detect the pressed position P of the piezoelectric cable 1 based on the voltage V1 input from the first input unit 51. Such a configuration can further simplify the configuration of the detection system 100. Furthermore, when the detection unit 54 detects the pressed position P of the piezoelectric cable 1 based on the voltages V1 and V2 input from the first input unit 51 and the second input unit 52, as in this embodiment, the accuracy of the detection can be improved.

[0064] (Second Embodiment) Next, a second embodiment of the present invention will be described in detail. Note that components identical or equivalent to those in the first embodiment are denoted by the same reference numerals unless otherwise specified, and redundant descriptions will be omitted.

[0065] The detection system 100 of this embodiment differs from the detection system 100 of the first embodiment in that the detection unit 54 detects the pressed position P of the piezoelectric cable 1 and the section in which the pressed position P is located, based on the electric charge as an electrical output input from the first input unit 51 and the second input unit 52.

[0066] Here, the integral of the voltage is approximately equal to the charge. Therefore, the measuring unit 53 in this embodiment measures the charge by integrating the voltages input from the first input unit 51 and the second input unit 52.

[0067] Figure 7 shows an example of the charge measured by the measuring unit 53 when a portion of the piezoelectric cable 1 is pressed from its outer surface, and is a diagram showing an example of charges Q1 and Q2 obtained by integrating the voltages V1 and V2 shown in Figure 5. In Figure 7, the charge Q1 obtained by integrating the voltage V1 input from the first input unit 51 and the charge Q2 obtained by integrating the voltage V2 input from the second input unit 52 are shown side by side. As shown in Figure 7, the charges Q1 and Q2 are approximately constant during the period when the piezoelectric cable 1 is pressed, and are close to zero during the period when the piezoelectric cable 1 is not pressed. However, for most of the period when the piezoelectric cable 1 is pressed, the charge Q1 is greater than the charge Q2, and the maximum value of the charge Q1 is greater than the maximum value of the charge Q2.

[0068] Figure 8 shows an example of the charge measured by the measuring unit 53 when another part of the piezoelectric cable 1 is pressed from the outer surface, similar to Figure 7, and is a diagram showing an example of charges Q1 and Q2 obtained by integrating the voltages V1 and V2 shown in Figure 6. As shown in Figure 8, the waveform of charge Q1 is approximately the same as the waveform of charge Q2. Charges Q1 and Q2 are approximately constant during the period when the piezoelectric cable 1 is pressed, and are close to zero during the period when the piezoelectric cable 1 is not pressed. The maximum values ​​of charges Q1 and Q2 are smaller than the maximum value of charge Q1 shown in Figure 7 and larger than the maximum value of charge Q2 shown in Figure 7.

[0069] Thus, the closer the pressed position P is to one end of the piezoelectric cable 1, the larger the charge Q1 input to the first input unit 51 becomes, and the smaller the charge Q2 input to the second input unit 52 becomes. The detection unit 54 of this embodiment detects the section in which the pressed position P of the piezoelectric cable 1 is located, based on the charges Q1 and Q2 measured by the measurement unit 53, that is, the charges Q1 and Q2 input from the first input unit 51 and the second input unit 52. More specifically, information showing the relationship between the maximum values ​​of charges Q1 and Q2 and the pressed position P is stored in the memory 60 in advance, and the detection unit 54 refers to this information based on the intensity of charges Q1 and Q2 input from the first input unit 51 and the second input unit 52 to detect the section in which the pressed position P of the piezoelectric cable 1 is located. Note that the method for detecting the section in which the pressed position P of the piezoelectric cable 1 is located based on the intensity of charges Q1 and Q2 is not limited to the method described above. For example, the detection unit 54 may detect the section in which the pressed position P is located based on the ratio Q1 / Q2 of the maximum value of charge Q1 to the maximum value of charge Q2. The ratio Q1 / Q2 increases as the pressed position P is closer to one end of the piezoelectric cable 1. For this reason, for example, information showing the relationship between the ratio Q1 / Q2 and the pressed position P is stored in the memory 60 in advance. Then, the detection unit 54 refers to this information based on the ratio Q1 / Q2 and detects the section in which the pressed position P is located. Alternatively, the detection unit 54 may detect the section in which the pressed position P is located based on the ratio Q1 / Q2 and the ratio Q2 / Q1 of the maximum value of charge Q2 to the maximum value of charge Q1.

[0070] According to the detection system 100 of this embodiment, the configuration of the detection system 100 can be simplified in the same way as the detection system 100 of the first embodiment.

[0071] In this embodiment, the measurement unit 53 measured charges Q1 and Q2 by integrating voltages V1 and V2. However, the method for measuring charges Q1 and Q2 is not limited; for example, the measurement unit 53 may be a coulomb meter.

[0072] Furthermore, the detection unit 54 may detect the section in which the pressed position P of the piezoelectric cable 1 is located based on the charge Q1 input from the first input unit 51. With such a configuration, the configuration of the detection system 100 can be further simplified. In addition, as in this embodiment, when the detection unit 54 detects the section in which the pressed position P of the piezoelectric cable 1 is located based on the charges Q1 and Q2 input from the first input unit 51 and the second input unit 52, the accuracy of the detection can be improved.

[0073] (Third embodiment) Next, a third embodiment of the present invention will be described in detail. Note that components identical or equivalent to those in the first embodiment are denoted by the same reference numerals unless otherwise specified, and redundant descriptions will be omitted.

[0074] The detection system 100 of this embodiment differs from the detection system 100 of the first embodiment in that the detection unit 54 detects the pressed position P of the piezoelectric cable 1 based on the rising edge of charges Q1 and Q2 input from the first input unit 51 and the second input unit 52, and detects the section in which the pressed position P is located.

[0075] Figure 9 shows the period including the rise of charge Q1 input from the first input unit 51 shown in Figure 7, and the period including the rise of charge Q2 input from the first input unit 51 shown in Figure 8. In Figure 9, the charge Q1 when the approximate center of the longitudinal direction of section SEa is pressed is shown by a solid line, and the charge Q1 when the approximate center of the longitudinal direction of section SEb is pressed is shown by a dashed line. As shown in Figure 9, the period TQa from when the charge Q1 when section SEa is pressed reaches the first reference value BL1 to the second reference value BL2, which is higher than the first reference value BL1, is shorter than the period TQb from when the charge Q1 when section SEb is pressed reaches the second reference value BL2. Note that the first reference value BL1 and the second reference value BL2 are smaller than the maximum value of charge Q1 when section SEb is pressed.

[0076] Furthermore, the closer the pressed position P is to one end of the piezoelectric cable 1, the shorter the time it takes for the charge Q1 to reach the first reference value BL1 and then the second reference value BL2. Although not illustrated here, the closer the pressed position P is to one end of the piezoelectric cable 1, the longer the time it takes for the charge Q2 to reach the first reference value BL1 and then the second reference value BL2.

[0077] The reason why the rise times of charges Q1 and Q2 change as described above in response to changes in the pressed position P is, for example, as follows. In the piezoelectric cable 1, the polymer piezoelectric layer 12 is sandwiched between the inner conductor 11 and the outer conductor 13, and the inner conductor 11 and the outer conductor 13 are spaced apart. For this reason, the piezoelectric cable 1 also functions as a capacitor. When the piezoelectric cable 1 is pressed, a voltage is generated between the inner conductor 11 and the outer conductor 13 at the pressed position P, and it can be considered that so-called RC circuits are formed in the first section SE1 and the second section SE2 of the piezoelectric cable 1. It is known that the time constant of an RC circuit can be determined by the product of the capacitance of the capacitor and the resistance of the resistor. As the pressed position P approaches one end of the piezoelectric cable, the resistance of the inner conductor 11 in the first section SE1 decreases, and the resistance of the inner conductor 11 in the second section SE2 increases. Therefore, as the pressed position P approaches one end of the piezoelectric cable, the time constant of the RC circuit in the first section SE1 becomes shorter, and the time constant of the RC circuit in the second section SE2 becomes longer. For this reason, as mentioned above, as the pressed position P approaches one end of the piezoelectric cable, the time required for the rise of charge Q1 input from the first input unit 51 becomes shorter, and the time required for the rise of charge Q2 input from the second input unit 52 becomes longer.

[0078] In this embodiment, the measurement unit 53 measures the period from when the charge Q1 input from the first input unit 51 reaches the first reference value BL1 until it reaches the second reference value BL2. The measurement unit 53 also measures the period from when the charge Q2 input from the second input unit 52 reaches the first reference value BL1 until it reaches the second reference value BL2. The measurement unit 53 then outputs signals related to these measured periods, and these signals are input to the detection unit 54 via a bus line.

[0079] In this embodiment, the detection unit 54 detects the section in which the pressed position P is located, based on the period from when the charge Q1 input from the first input unit 51 reaches the first reference value BL1 to when it reaches the second reference value BL2, and the period from when the charge Q2 input from the second input unit 52 reaches the first reference value BL1 to when it reaches the second reference value BL2. More specifically, information showing the relationship between the period from when the charge Q1 reaches the first reference value BL1 to when it reaches the second reference value BL2, and the period from when the charge Q2 input from the second input unit 52 reaches the first reference value BL1 to when it reaches the second reference value BL2, and the pressed position P is stored in the memory 60 in advance. Based on the signals related to these periods input from the measurement unit 53, the detection unit 54 refers to this information and detects the section in which the pressed position P of the piezoelectric cable 1 is located.

[0080] Furthermore, the detection unit 54 may detect the section in which the pressed position P is located based on the period from when the charge Q1 input from the first input unit 51 reaches a first reference value BL1 until it reaches a second reference value BL2. With such a configuration, the configuration of the detection system 100 can be further simplified. In addition, as in this embodiment, when the detection unit 54 detects the section in which the pressed position P of the piezoelectric cable 1 is located based on the period from when the charge Q1 input from the first input unit 51 reaches a first reference value BL1 until it reaches a second reference value BL2, and the period from when the charge Q2 input from the second input unit 52 reaches a first reference value BL1 until it reaches a second reference value BL2, the accuracy of the detection can be improved.

[0081] Furthermore, similar to the charges Q1 and Q2, the closer the pressed position P is to one end of the piezoelectric cable 1, the shorter the time required for the voltage V1 to rise and the longer the time required for the voltage V2 to rise. For this reason, the detection unit 54 may detect the section in which the pressed position P is located based on the rise of the voltage V1 input from the first input unit 51, or it may detect the section in which the pressed position P is located based on the rise of the voltages V1 and V2 input from the first input unit 51 and the second input unit 52. Note that the voltages V1 and V2 and the charges Q1 and Q2 are the electrical outputs of the piezoelectric cable 1 input to the detection unit 50 from the first input unit 51 and the second input unit 52. For this reason, the detection unit 54 may detect the section in which the pressed position P is located based on the period from when the electrical output reaches a first reference value until it reaches a second reference value which is higher than the first reference value.

[0082] (Fourth Embodiment) Next, a third embodiment of the present invention will be described in detail. Note that components identical or equivalent to those in the first embodiment are denoted by the same reference numerals unless otherwise specified, and redundant descriptions will be omitted.

[0083] Figure 10 is a diagram showing the detection system 100 according to this embodiment, similar to Figure 1. As shown in Figure 10, the detection system 100 of this embodiment differs from the detection system 100 of the first embodiment in that it includes a ground line 48.

[0084] In this embodiment, the ground wire 48 is electrically connected to the other end of the outer conductor 13. The ground wire 48 only needs to be electrically connected to the outer conductor 13; for example, it may be electrically connected to one end of the outer conductor 13.

[0085] In the first input unit 51 of this embodiment, terminal 51a is electrically connected to one end of the internal conductor 11 via the amplifier 45, but terminal 51b is not electrically connected to the piezoelectric cable 1. In other words, the first input unit 51 is electrically connected to one end of the internal conductor 11.

[0086] In the second input section 52 of this embodiment, terminal 52a is electrically connected to one end of the internal conductor 11 via the amplifier 46, but terminal 52b is not electrically connected to the piezoelectric cable 1. In other words, the second input section 52 is electrically connected to the other end of the internal conductor 11.

[0087] In this embodiment, the measuring unit 53 is electrically connected to one end of the internal conductor 11 via the first input unit 51 and amplifier 45, and electrically connected to the other end of the internal conductor 11 via the second input unit 52 and amplifier 46. The measuring unit 53 is a voltmeter that measures the voltages to ground input from the first input unit 51 and the second input unit 52.

[0088] In this embodiment, as in the first embodiment, the closer the pressed position P is to one end of the piezoelectric cable 1, the larger the voltage V1 to ground input to the first input unit 51 becomes, and the smaller the voltage V2 to ground input to the second input unit 52 becomes. Then, as in the first embodiment, the detection unit 54 detects the section in which the pressed position P is located, based on the strength of the voltages V1 and V2 input from the first input unit 51 and the second input unit 52, as detection of the pressed position in the longitudinal direction of the piezoelectric cable 1.

[0089] As described above, the detection system 100 of this embodiment comprises a piezoelectric cable 1, a ground wire 48 electrically connected to the outer conductor 13, and a detection unit 50 including a first input unit 51, a second input unit 52, and a detection unit 54. The first input unit is electrically connected to one end of the inner conductor 11 and receives a voltage V1 output from the inner conductor 11. The second input unit 52 is electrically connected to the other end of the inner conductor 11 and receives a voltage V2 output from the inner conductor 11. The detection unit 54 detects the pressed position P in the longitudinal direction of the piezoelectric cable 1 based on the voltages V1 and V2 input from the first input unit 51 and the second input unit 52. According to the detection system 100 of this embodiment, the configuration of the detection system 100 can be simplified in the same way as the detection system 100 of the first embodiment.

[0090] In this embodiment, the detection unit 54 detects the section in which the pressed position P of the piezoelectric cable 1 is located based on the voltages V1 and V2 input from the first input unit 51 and the second input unit 52. However, the detection unit 54 may also detect the section in which the pressed position P of the piezoelectric cable 1 is located based on the voltage V1 input from the first input unit 51. Such a configuration can further simplify the configuration of the detection system 100. Furthermore, when the detection unit 54 detects the section in which the pressed position P of the piezoelectric cable 1 is located based on the voltages V1 and V2 input from the first input unit 51 and the second input unit 52, as in this embodiment, the accuracy of the detection can be improved.

[0091] Furthermore, similar to the second embodiment, the measuring unit 53 may measure the charge Q1 input from the first input unit 51 and the charge Q2 input from the second input unit 52, and the detection unit 54 may detect the section in which the pressed position P of the piezoelectric cable 1 is located based on the charges Q1 and Q2 input from the first input unit 51 and the second input unit 52.

[0092] Although the present invention has been described above with reference to the above embodiments, the present invention is not limited to these.

[0093] For example, in the above embodiment, the internal conductor 11 is made of a high-resistance material, and the resistance value of the internal conductor 11 from one end to the other in the longitudinal direction is 10 kΩ or more and 100 GΩ or less. However, the external conductor 13 may be made of a high-resistance material, and the resistance value of the external conductor 13 from one end to the other in the longitudinal direction may be 10 kΩ or more and 100 GΩ or less. In this case, for example, the internal conductor 11 is a conductor with higher conductivity than the high-resistance material, similar to the external conductor 13 in the above embodiment. Furthermore, the external conductor 13 may be configured in which a tape-shaped film made of a high-resistance material is wound around the polymer piezoelectric layer 12, and in this case, the film may be wound in a spiral winding or a longitudinal winding.

[0094] In other words, the piezoelectric cable 1 comprises an inner conductor 11, a polymer piezoelectric layer 12 that is in contact with the inner conductor 11 and surrounds the outer surface of the inner conductor 11, and an outer conductor 13 that is in contact with the polymer piezoelectric layer 12 and surrounds the outer surface of the polymer piezoelectric layer 12. The resistance value of one of the conductors, the inner conductor 11 or the outer conductor 13, from one end to the other should be between 10 kΩ and 100 GΩ.

[0095] Alternatively, the detection system 100 may include the piezoelectric cable 1, a ground wire 48 electrically connected to the other conductor of the inner conductor 11 and outer conductor 13, and a detection unit 50, wherein the detection unit 50 may include a first input unit 51 electrically connected to one end of the one conductor and receiving the electrical output from the one conductor, and a detection unit 54 that detects the pressed position P in the longitudinal direction of the piezoelectric cable 1 based on the electrical output received from the first input unit 51.

[0096] Furthermore, in the above embodiment, a piezoelectric cable 1 comprising a protective layer 15 including an insulating layer 16, a shielding layer 17, and a jacket layer 18 was described as an example. However, the protective layer 15 is not limited and may consist of, for example, only the jacket layer 18. Also, the piezoelectric cable 1 may not have a protective layer 15.

[0097] Furthermore, in the above embodiment, the detection unit 54 was described as detecting which of the three sections SEa to SEc of the piezoelectric cable 1 the pressed position P of the piezoelectric cable 1 is located in, as an example of detecting the pressed position P of the piezoelectric cable 1 in the longitudinal direction. However, the detection of the pressed position P of the piezoelectric cable 1 in the longitudinal direction is not limited. For example, the number of sections of the piezoelectric cable 1 may be two or four or more. Also, the detection unit 54 may detect the distance along the piezoelectric cable 1 from one end of the piezoelectric cable 1 to the pressed position P as the detection of the pressed position P of the piezoelectric cable 1 in the longitudinal direction.

[0098] Furthermore, even when two or more different positions on the piezoelectric cable 1 are pressed, the electrical output input from the first input unit 51 and the electrical output input from the second input unit 52 change. Therefore, even when two or more different positions on the piezoelectric cable 1 are pressed, the pressed position P in the longitudinal direction of the piezoelectric cable 1 can be detected from the electrical output input from the first input unit 51 and the electrical output input from the second input unit 52. For this reason, the detection unit 54 may also detect the pressed position P in such cases.

[0099] Furthermore, the detection unit 54 may detect the pressed position P of the piezoelectric cable 1 using a learning model constructed by machine learning the electrical output from the piezoelectric cable 1. For example, the learning model is constructed using the voltages V1 and V2 input from the first input unit 51 and the second input unit 52 and measured by the measurement unit 53, and the machine learning used to construct this learning model is supervised learning. Specifically, for example, in the first embodiment, the learning model is constructed by machine learning using the voltages V1 and V2 shown in Figure 5 as representing the central part of section SEa of the piezoelectric cable 1 being pressed, and the voltages V1 and V2 shown in Figure 6 as representing the central part of section SEb of the piezoelectric cable 1 being pressed. The detection unit 54 then uses the learning model constructed in this way to detect the section in which the pressed position P of the piezoelectric cable 1 is located. With this configuration, the accuracy of the detection can be improved, and it is particularly useful as the number of sections of the piezoelectric cable 1 increases. The electrical output from the piezoelectric cable 1 may be the charges Q1 and Q2 input from the first input unit 51 and the second input unit 52 and measured by the measurement unit 53, or it may be the voltage V1 or charge Q1 input from the first input unit 51 and measured by the measurement unit 53. Furthermore, a learning model may be constructed by machine learning the electrical output from the piezoelectric cable 1 when two or more different locations on the piezoelectric cable 1 are pressed.

[0100] Furthermore, in the above embodiment, the piezoelectric cable 1 was described as being arranged in a generally straight line along the flat seat surface 111. However, the arrangement of the piezoelectric cable 1 is not limited.

[0101] Figure 11 illustrates the arrangement of the piezoelectric cable 1 in a modified example. As shown in Figure 11, in this modified example, the piezoelectric cable 1 is arranged along the plane 121 of the object to be measured in a meandering manner. Therefore, the piezoelectric cable 1 has a curved portion FL. With this configuration, it is possible to detect where a force is applied on the plane 121 of the object to be measured. Examples of objects to be measured include the floor of a room, and for example, it is possible to detect where a person is in the room. Note that the piezoelectric cable 1 does not have to meander; for example, it may be arranged in a spiral shape.

[0102] Figure 12 illustrates the arrangement of the piezoelectric cable 1 in another modified example. As shown in Figure 12, in this modified example, the piezoelectric cable 1 is arranged along the curved surface 122 of the object to be measured in a meandering manner. With this configuration, it is possible to detect where a force is applied on the curved surface 122 of the object to be measured. Note that the piezoelectric cable 1 does not have to meander; for example, it may be arranged in a spiral shape. Also, the object to be measured may be a sphere, and the curved surface 122 may be a sphere.

[0103] Furthermore, although the detection system 100 had only one piezoelectric cable 1 in the above embodiment, there may be multiple piezoelectric cables 1. [Industrial applicability]

[0104] As described above, the present invention provides a piezoelectric cable and a detection system that can simplify the configuration of a detection system, and can be used in fields such as object position detection systems. [Explanation of symbols]

[0105] 1. Piezoelectric cable 11. Internal Conductor 12. Polymer piezoelectric layer 13. Outer conductor 50...Detection Unit 51...First Input Section 52...Second Input Section 53...Measurement part 54...Detection unit 100 detection system

Claims

1. Internal conductor and, A polymer piezoelectric layer in contact with the inner conductor and surrounding the outer surface of the inner conductor, An outer conductor that is in contact with the polymer piezoelectric layer and surrounds the outer surface of the polymer piezoelectric layer, Equipped with, The resistance value of one of the inner conductors and the outer conductor from one end to the other is 10 kΩ or more and 100 gΩ or less. A piezoelectric cable characterized by the following features.

2. A piezoelectric cable having an inner conductor, a polymer piezoelectric layer in contact with the inner conductor and surrounding the outer surface of the inner conductor, and an outer conductor in contact with the polymer piezoelectric layer and surrounding the outer surface of the polymer piezoelectric layer, wherein the resistance value of one of the inner conductor and the outer conductor from one end to the other is 10 kΩ or more and 100 GΩ or less, A ground wire electrically connected to the other conductor of the inner conductor and the outer conductor, Detection unit and Equipped with, The detection unit includes a first input unit that is electrically connected to one end of the one conductor and receives an electrical output from the one conductor, and a detection unit that detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical output received from the first input unit. A detection system characterized by the following features.

3. The detection unit further includes a second input section which is electrically connected to the other end of the one conductor and to which the electrical output output from the one conductor is input, The detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical outputs input from the first input unit and the second input unit. The detection system according to feature 2.

4. A piezoelectric cable having an inner conductor, a polymer piezoelectric layer in contact with the inner conductor and surrounding the outer surface of the inner conductor, and an outer conductor in contact with the polymer piezoelectric layer and surrounding the outer surface of the polymer piezoelectric layer, wherein the resistance value of one of the inner conductor and the outer conductor from one end to the other is 10 kΩ or more and 100 GΩ or less, Detection unit and Equipped with, The detection unit includes a first input unit that is electrically connected individually to one end of the one conductor and one end of the other conductor among the inner and outer conductors, and to which electrical outputs from the one conductor and the other conductor are input; and a detection unit that detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical outputs input from the first input unit. A detection system characterized by the following features.

5. The detection unit further includes a second input unit which is electrically connected individually to the other ends of the one conductor and the other conductor, and to which the electrical outputs output from the one conductor and the other conductor are input. The detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable based on the electrical outputs input from the first input unit and the second input unit. The detection system according to feature 4.

6. The detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable based on the period from when the electrical output reaches a first reference value until it reaches a second reference value that is higher than the first reference value. The detection system according to any one of claims 2 to 5.

7. The aforementioned electrical output is voltage. The detection system according to any one of claims 2 to 5.

8. The aforementioned electrical output is electric charge. The detection system according to any one of claims 2 to 5.

9. The detection unit detects the pressed position in the longitudinal direction of the piezoelectric cable using a learning model constructed by machine learning the electrical output. The detection system according to any one of claims 2 to 5.

10. The piezoelectric cable is arranged along a plane in the object being measured. The piezoelectric cable has a curved portion that curves. The detection system according to any one of claims 2 to 5.

11. The piezoelectric cable is arranged along the curved surface of the object being measured. The detection system according to any one of claims 2 to 5.

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