Inference system, inference method, and recording medium

Abstract

A presumption system includes a first sensor capable of being disposed between a wheel and a tire fitted to the wheel, which outputs a first sensor signal corresponding to a pressing force generated by the wheel and the tire, and a processor that presumes a state of a rotating body including the wheel and the tire based on the first sensor signal, the processor generating a first interval signal by dividing the first sensor signal in a certain interval, and presuming the state of the rotating body based on the first interval signal.

Description

[0001] This application is based on the priority claimed by Japanese Patent Application No. 2021-187948, filed on November 18, 2021, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure relates to a presumption system, presumption method, and recording medium. Background Technology

[0003] Techniques for estimating the condition of a vehicle's tires are known. For example, Japanese Patent Application Publication No. 8-247745 discloses a technique that uses two laser devices spaced apart on the outer side of a vehicle's tire / wheel assembly to measure the tire's camber angle. Japanese Patent Application Publication No. 2019-49488 discloses a technique that uses an acceleration sensor located in the inner liner of the tire and at the center of the tire's width direction to estimate the load acting on the tire. Summary of the Invention

[0004] The technology disclosed in Japanese Patent Application Publication No. 8-247745 requires the installation of a laser device on the outer side of the tire, thus making the device large and potentially hindering vehicle movement. The technology disclosed in Japanese Patent Application Publication No. 2019-49488 requires the preparation of a special tire with an acceleration sensor installed in the inner liner layer.

[0005] This disclosure describes an estimation system, estimation method, and recording medium for estimating the state of a rotating body using a simple structure.

[0006] One aspect of this disclosure provides an estimation system comprising: a first sensor disposed between a wheel and a tire mounted on the wheel, outputting a first sensor signal corresponding to the pressing force generated by the wheel and the tire; and a processor that estimates the state of a rotating body including the wheel and the tire based on the first sensor signal. The processor generates a first interval signal by dividing the first sensor signal into specific intervals, and estimates the state of the rotating body based on the first interval signal.

[0007] Another aspect of this disclosure provides an estimation method comprising: acquiring a sensor signal corresponding to the pressing force generated by the wheel and the tire from a sensor disposed between the wheel and the tire mounted on the wheel; generating an interval signal by dividing the sensor signal into specific intervals; and estimating the state of a rotating body including the wheel and the tire based on the interval signal.

[0008] Another aspect of this disclosure is a computer-readable, non-transitory recording medium that records an estimation program. The estimation program includes a procedure that causes a computer to perform the following steps: acquiring sensor signals corresponding to the pressing pressure generated by the wheel and tire from sensors disposed between the wheel and the tire mounted on the wheel; generating interval signals by dividing the sensor signals into specific intervals; and estimating the state of a rotating body including the wheel and tire based on the interval signals.

[0009] According to various aspects and embodiments of this disclosure, the state of the rotating body can be estimated through a simple structure. Attached Figure Description

[0010] Figure 1 This is a diagram that roughly represents a vehicle equipped with a presumed system according to one embodiment.

[0011] Figure 2 yes Figure 1 A three-dimensional diagram of the solid of revolution shown.

[0012] Figure 3 It is a general representation Figure 1 The diagram shows the structure of the estimated system.

[0013] Figure 4 yes Figure 1 The image shows an exploded perspective view of the sensor module.

[0014] Figure 5 It is used to explain the action on Figure 1 The force diagram of the sensor module shown.

[0015] Figure 6 It is used to explain from Figure 1 The diagram shows the sensor signal output by the sensor.

[0016] Figure 7 This is a diagram illustrating an example of sensor signals during constant-speed driving.

[0017] Figure 8 This is a diagram illustrating an example of sensor signals during acceleration.

[0018] Figure 9 It means Figure 1 The flowchart shows the estimation method performed by the processor.

[0019] Figure 10 This is a diagram illustrating an example of the generation and processing of interval signals.

[0020] Figure 11 This is another example of the generation and processing of interval signals.

[0021] Figure 12This is another example of how interval signals are generated and processed.

[0022] Figure 13 This is another example of how interval signals are generated and processed.

[0023] Figure 14 It is a diagram used to illustrate the reaction force from the road surface when the outward camber angle is 0 degrees.

[0024] Figure 15 It is a diagram used to illustrate the reaction force from the road surface at the point of positive outward inclination.

[0025] Figure 16 It is a diagram used to illustrate the reaction force from the road surface at the negative outward slope.

[0026] Figure 17 This is a diagram showing an example of the sensor signal for each tilt angle.

[0027] Figure 18 It is a diagram used to illustrate the slip angle.

[0028] Figure 19 This is a diagram used to illustrate the forces acting on the sensor module when a slip angle is generated.

[0029] Figure 20 This is a diagram showing an example of the sensor signal for each slip angle.

[0030] Figure 21 It is a graph used to illustrate the peak-to-peak value and the second peak value.

[0031] Figure 22 It is a graph showing the relationship between peak-to-peak value and attenuation rate when slip angle, outward tilt angle, load, and air pressure change.

[0032] Figure 23 yes Figure 22 A magnified view of a portion of the image.

[0033] Figure 24 It is a diagram used to illustrate the presumed model.

[0034] Figure 25 This is a structural diagram that roughly represents a hypothetical system of another embodiment.

[0035] Figure 26 This is a diagram showing an example of a sensor module configuration.

[0036] Figure 27 This is a diagram showing an example of the sensor signal for each tilt angle.

[0037] Figure 28 This is a diagram showing an example of the sensor signal for each slip angle.

[0038] Figure 29 This is a structural diagram that roughly represents another embodiment of the proposed system.

[0039] Figure 30 This is a structural diagram that roughly represents another embodiment of the proposed system. Detailed Implementation

[0040] Summary of Implementation Methods

[0041] An estimation system according to one aspect of this disclosure includes: a first sensor disposed between a wheel and a tire mounted on the wheel, outputting a first sensor signal corresponding to the pressing force generated by the wheel and the tire; and a processor that estimates the state of a rotating body including the wheel and the tire based on the first sensor signal. The processor generates a first interval signal by dividing the first sensor signal into specific intervals, and estimates the state of the rotating body based on the first interval signal.

[0042] Another aspect of the estimation method disclosed herein includes: acquiring a sensor signal corresponding to the pressing force generated by the wheel and the tire from a sensor disposed between the wheel and the tire mounted on the wheel; generating an interval signal by dividing the sensor signal into specific intervals; and estimating the state of a rotating body including the wheel and the tire based on the interval signal.

[0043] Another aspect of this disclosure is a computer-readable, non-transitory recording medium that records an estimation program. The estimation program includes commands that cause a computer to perform the following steps: acquiring sensor signals corresponding to the pressing pressure generated by the wheel and tire from sensors disposed between the wheel and the tire mounted on the wheel; generating interval signals by dividing the sensor signals into specific intervals; and estimating the state of a rotating body including the wheel and tire based on the interval signals.

[0044] In the technology of this disclosure (hereinafter, sometimes simply referred to as "the technology of this disclosure"), which includes these estimation systems, estimation methods, and recording media, a sensor (first sensor) disposed between the wheel and the tire is configured to output a sensor signal (first sensor signal) corresponding to the pressing force generated by the wheel and the tire. The load from the vehicle acts on the sensor (first sensor) via the wheel. The reaction force from the road surface acts on the sensor (first sensor) via the tire. These forces can vary depending on the state of the rotating body; therefore, the state of the rotating body can be estimated based on the sensor signal (first sensor signal) using the technology of this disclosure. Thus, the state of a rotating body can be estimated using the technology of this disclosure with a simple structure that involves disposing the sensor (first sensor) between the wheel and the tire.

[0045] In some embodiments, the first sensor may also be disposed between the rim and the tire contained in the wheel. In the case where the wheel includes a rim, the tire is mounted on the rim. Therefore, with a simple structure where the first sensor is disposed between the rim and the tire, the state of the rotating body can be estimated.

[0046] In some embodiments, the rotating body may also include a first end and a second end, which are two ends in the direction of the rotation axis of the rotating body. The first sensor may also be positioned closer to the first end than the center of the rotating body in the direction of the rotation axis. When the first sensor is positioned at the center of the rotating body in the direction of the rotation axis, for example, even if the outward tilt angle changes in either the positive or negative direction, the first sensor signal changes in the same manner. On the other hand, in the above structure, the first sensor signal changes asymmetrically. Therefore, the accuracy of estimating the state of the rotating body can be improved.

[0047] In some embodiments, the estimation system may also include a second sensor configured between the wheel and tire, outputting a second sensor signal corresponding to the pressing force generated by the wheel and tire. The second sensor may also be configured closer to the second end than the center of the rotating body in the rotational axis direction. The processor may also generate a second interval signal by dividing the second sensor signal into specific intervals, and further estimate the state based on the second interval signal. In this case, the first sensor and the second sensor are configured on opposite sides of each other relative to the center of the rotating body in the rotational axis direction. The changes in the estimated state of the rotating body produced by the first sensor signal output from the first sensor and the second sensor signal output from the second sensor produce different changes. Therefore, using two sensor signals that produce different changes to estimate the state of the rotating body improves the estimation accuracy of the rotating body's state compared to a structure that uses a single sensor signal to estimate the state of the rotating body.

[0048] In some implementations, the specific interval can also be the interval of one revolution of the rotating body. As the rotating body rotates, the portion of the rotating body in contact with the road surface changes, thus changing the relative positional relationship between the first sensor and the contact portion. Therefore, the first sensor signal exhibits periodicity, with the same waveform shape each time the rotating body completes one revolution. Therefore, by analyzing the signal of the first interval of one revolution of the rotating body, the state of the rotating body can be estimated.

[0049] In some implementations, the processor may also estimate the state based on multiple distinct waveform characteristics calculated from the first interval signal. The waveform characteristics calculated from the first interval signal can serve as an indicator of the state of the rotating body. Therefore, by using these characteristics, the accuracy of the state estimation of the rotating body can be improved.

[0050] In some implementations, the multiple waveform characteristics may also include values ​​based on at least one of the following: the maximum value of the first interval signal; the minimum value of the first interval signal; the difference between the maximum and minimum values; the standard deviation of the first interval signal; the variance of the first interval signal; the average value of the first interval signal; the median of the first interval signal; and the value of the first interval signal at the inflection point. By using these characteristics, the estimation accuracy of the state of the rotating body can be improved.

[0051] In some implementations, the processor may also use a machine learning model to estimate the state of the rotating body. In this case, by fully learning the machine learning model, the accuracy of the state estimation of the rotating body can be improved.

[0052] In some embodiments, the state of the rotating body may also include at least one of the following: tilt angle, slip angle, load applied to the rotating body, and air pressure. The tendency of the first sensor signal to change when the tilt angle changes, the tendency of the first sensor signal to change when the slip angle changes, the tendency of the first sensor signal to change when the load changes, and the tendency of the first sensor signal to change when the air pressure changes are different from each other. Therefore, the tilt angle, slip angle, load, and air pressure can be estimated separately.

[0053] In some embodiments, the first sensor and the processor may also constitute a sensor module. The sensor module may also be disposed on the rotating body. The processor may also output the estimation result to an external device disposed outside the rotating body. In this case, the first sensor signal is processed within the sensor module, and the estimation result is output to the external device. Compared to a structure where the first sensor signal is processed in an external device, the amount of communication between the sensor module and the external device can be reduced.

[0054] In some implementations, the first sensor may also be a piezoelectric element that generates electrical energy in response to pressure. The processor may also operate using the electrical energy generated by the piezoelectric element. In this case, the processor can operate without receiving a power supply from an external source. Therefore, wiring for external power supply is unnecessary, thus simplifying the structure of the estimation system.

[0055] In some embodiments, the first sensor may also be a piezoelectric element that generates electrical energy in response to pressure. The processor may also estimate the state of the rotating body by using the voltage or current of the electrical energy generated by the piezoelectric element as a signal from the first sensor. In this case, the state of the rotating body can be estimated using a simple structure where the piezoelectric element is positioned between the wheel and the tire.

[0056] Examples of implementation methods

[0057] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the description of the drawings, the same symbols are used to denote the same elements, and repeated descriptions are omitted.

[0058] Reference Figures 1-4 This describes the estimation system for one implementation method. Figure 1 This is a diagram that roughly represents a vehicle equipped with a presumed system according to one embodiment. Figure 2 yes Figure 1 A three-dimensional diagram of the solid of revolution shown. Figure 3 It is a general representation Figure 1 The diagram shows the structure of the estimated system. Figure 4 yes Figure 1 The image shows an exploded perspective view of the sensor module. Figure 1 The estimation system 1 shown is a system for estimating the state of the rotating body 2. The estimation system 1 can be mounted, for example, on a vehicle V. The vehicle V includes the rotating body 2 and is configured to move by rotating the rotating body 2. Examples of the vehicle V may also include automobiles, bicycles, and motorcycles. In this embodiment, an automobile is used as an example of a vehicle V for description, but the technology disclosed herein is not limited to applications on automobiles. The vehicle V includes four rotating bodies 2 disposed at the front, rear, left, and right.

[0059] like Figure 2 As shown, the rotating body 2 is a rotatable element centered on the rotation axis AX. The rotating body 2 has an outer end portion 2a (first end; see reference). Figure 14 ) and inner end 2b (second end; refer to Figure 14 The outer end 2a and the inner end 2b are the two ends of the rotating body 2 in the direction of the rotation axis AX (rotation axis direction). The outer end 2a faces the outside of the vehicle V. The rotating body 2 includes a wheel 21 and a tire 22.

[0060] Wheel 21 is a component that transmits rotational force about the axis of rotation AX to tire 22. Wheel 21 can also be constructed from rigid components. Examples of materials used to construct wheel 21 include metallic materials such as steel, magnesium, aluminum, and stainless steel, as well as resin raw materials such as carbon fiber. Figure 2 In the specific example shown, the wheel 21 includes a rim 23 and a plurality of spokes 24. The rim 23 is an annular component forming the outer edge of the wheel 21. A tire 22 is mounted along the outer periphery of the rim 23. The plurality of spokes 24 each extend radially from the center of the wheel 21 to the rim 23. The rim 23 and the spokes 24 can be integrally formed or separately formed.

[0061] Tire 22 is a ring-shaped component fitted onto wheel 21. Tire 22 is positioned along the outer periphery (rim 23) of wheel 21. Tire 22 may also be constructed from flexible components. Examples of materials used to construct tire 22 may include resins such as rubber.

[0062] like Figure 3 As shown, the estimation system 1 includes a sensor module 3. The sensor module 3 is a module capable of detecting the pressing force acting on the rotating body 2. The sensor module 3 is disposed on the rotating body 2. Specifically, the sensor module 3 is disposed between the wheel 21 (rim 23) and the tire 22. The sensor module 3 may also be clamped between the wheel 21 (rim 23) and the tire 22 in the vertical direction. In this embodiment, multiple sensor modules 3 are arranged at equal intervals along the outer circumference of the wheel 21 (rim 23). Some sensor modules 3 are disposed at the outer end 2a (outer rim). The sensor modules 3 may also be disposed at the inner end 2b (inner rim).

[0063] Furthermore, the number and position of the sensor modules 3 disposed on a rotating body 2 can be appropriately selected. In this embodiment, multiple sensor modules 3 are disposed on a rotating body 2; for example, a single sensor module 3 may also be disposed on a rotating body 2. Not limited to this structure, the number of sensor modules disposed on a rotating body 2 may be, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 11. For example, the same number of sensor modules 3 as the spokes 24 may be disposed on a rotating body 2. For example, the same number of sensor modules 3 as the spacing between two adjacent spokes 24 may also be disposed on a rotating body 2. When multiple sensor modules 3 are disposed on a rotating body 2, each sensor module 3 may be arranged at equal intervals along the outer circumference of the wheel 21 (rim 23). Alternatively, multiple sensor modules 3 may be arranged at different intervals along the outer circumference of the wheel 21 (rim 23). Alternatively, at least a portion of the multiple sensor modules 3 may be arranged at equal intervals along the outer periphery of the wheel 21 (rim 23), while the other sensor modules 3 may be arranged at different intervals along the outer periphery of the wheel 21 (rim 23).

[0064] exist Figure 4 In the specific example shown, each sensor module 3 is configured to be disposed between the wheel 21 (rim 23) and the tire 22. Each sensor module 3 includes a piezoelectric element 31 (first sensor), a back plate 32, a substrate 33, a substrate 34, and a base material 35. The piezoelectric element 31 is a component that generates electrical energy corresponding to external forces such as pressure applied to the piezoelectric element 31. Examples of the piezoelectric element 31 may also include a piezoelectric ceramic element (piezoelectric element). The piezoelectric element 31 may also be formed in a plate shape.

[0065] The back plate 32 is a plate-shaped component that protects the piezoelectric element 31. The back plate 32 can be made of metal (e.g., stainless steel) or resin. For example, the back plate 32 has a plate-like shape that is slightly larger than the piezoelectric element 31. By overlapping with the piezoelectric element 31, the back plate 32 can also alleviate the stress on the piezoelectric element 31. The amount of deformation of the piezoelectric element 31, corresponding to the pressing pressure applied to the sensor module 3, is adjusted according to the thickness of the back plate 32.

[0066] Substrates 33 and 34 are plate-shaped components that extract the electrical energy generated in the piezoelectric element 31 as a sensor signal (first sensor signal). Specifically, substrates 33 and 34 may also extract the voltage or current of the electrical energy generated in the piezoelectric element 31 as a sensor signal. In this embodiment, as an example, the case where voltage is processed as a sensor signal will be described. Substrates 33 and 34 may also be flexible printed circuit boards (FPCs). Substrate 33 may, for example, be configured to include a main body portion 33a and a wiring portion 33b. The main body portion 33a is the portion that constitutes the laminated structure described later. The wiring portion 33b is the portion that connects the sensor module 3 to external circuits, etc. Substrate 34 includes a main body portion 34a and a wiring portion 34b. The main body portion 34a is the portion that constitutes the laminated structure described later. The wiring portion 34b is the portion that connects the sensor module 3 to external circuits, etc. In this embodiment, the shape of substrate 33 is substantially the same as the shape of substrate 34, but the shape of substrate 33 may also be different from the shape of substrate 34. The main body parts 33a and 34a may, for example, be formed to be the same size as the back plate 32.

[0067] The substrate 35 is a component for mounting the sensor module 3 to the wheel 21. The substrate 35 has a shape that follows the rim 23. A recess 35a is provided on the substrate 35 to accommodate the laminated structure described later.

[0068] exist Figure 4 In the specific example shown, the back plate 32 overlaps on the piezoelectric element 31, and the overlapping piezoelectric element 31 and back plate 32 are held between the main body portion 33a of the substrate 33 and the main body portion 34a of the substrate 34. That is, by sequentially stacking the substrate 33, back plate 32, piezoelectric element 31, and substrate 34, a laminated structure is formed, which is housed in the recess 35a of the substrate 35. Thus, the sensor module 3 is formed. The sensor module 3 is positioned at a desired location between the rim 23 and the tire 22. Figure 4 In the specific example shown, the sensor module 3 can also be disposed on the rotating body 2 such that the side of the substrate 35 opposite to the side where the recess 35a is provided contacts the wheel rim 23. In this case, the side of the main body portion 33a of the substrate 33 opposite to the back plate 32 contacts the tire 22.

[0069] Each sensor module 3 may include, for example, a piezoelectric element 31 as a circuit element. In addition to the piezoelectric element 31, each sensor module 3 may also include an analog-to-digital (AD) converter 41, a processor 42, a communication interface 43, a power converter 44, and a power storage device 45. The AD converter 41, processor 42, communication interface 43, power converter 44, and power storage device 45 may also be mounted on substrate 33 or substrate 34.

[0070] The AD converter 41 is a circuit element that converts the analog sensor signal output from the piezoelectric element 31 into a digital sensor signal. The AD converter 41 outputs the digital sensor signal to the processor 42.

[0071] Processor 42 is a circuit element that estimates the state of rotating body 2 based on sensor signals. The state of rotating body 2 estimated by processor 42 includes at least one of tilt angle, slip angle, load applied to rotating body 2, and air pressure. Processor 42 can also output the estimation result to external device 5 via communication interface 43. Details of the processing performed by processor 42 will be described later. Examples of processor 42 include, but are not limited to, central processing unit (CPU), digital signal processor (DSP), auxiliary processor (ASP), microcomputer, programmable logic controller (PLC), field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), and integrated circuit (IC). Processor 42 may also have a multi-core structure.

[0072] Communication interface 43 is the hardware that enables sensor module 3 to send and receive data with external device 5 via communication network NW1. Communication network NW1 can be configured as a wired communication network, a wireless communication network, or a combination of these. Examples of communication network NW1 may include one or more of the following: Internet, intranet, wide area network (WAN), local area network (LAN), Bluetooth (registered trademark), wireless LAN (Wi-Fi, etc.), controller area network (CAN), and mobile communication network. Communication interface 43 may also conform to a specific communication protocol.

[0073] The power converter 44 is a device that converts the sensor signal (voltage) generated by the piezoelectric element 31 into a rechargeable energy storage device 45. The power converter 44 is, for example, a power regulator. As described later, if the sensor signal contains a periodically changing AC signal, the power converter 44 may also include a rectifier circuit.

[0074] The energy storage device 45 is a rechargeable and dischargeable device. The energy storage device 45 stores the sensor signal generated by the piezoelectric element 31 as electrical energy (power) and supplies power to the circuit elements within the sensor module 3. For example, the processor 42 operates using the electrical energy generated by the piezoelectric element 31. Examples of the energy storage device 45 may also include batteries such as lithium-ion batteries and capacitors.

[0075] External device 5 is a device capable of communicating with sensor module 3. External device 5 may, for example, be configured to provide a person (passenger) riding in vehicle V with an estimated result related to the state of rotating body 2. External device 5 may also, for example, be configured to provide an estimated result related to the state of rotating body 2 to other equipment contained in vehicle V. External device 5 may also, for example, be configured to provide an estimated result related to the state of rotating body 2 to equipment located outside vehicle V (e.g., a server that can be connected via a communication line).

[0076] The external device 5 is disposed outside the rotating body 2, or it can be disposed inside the vehicle V. Examples of the external device 5 may include an in-vehicle unit and a mobile terminal held by a passenger. Examples of mobile terminals may include smartphones, tablet terminals, and portable computers. The external device 5 may also include, for example, a processor 51, a memory 52, and a communication interface 55. The external device 5 may also further include, for example, an input device 53, an output device 54, and a communication interface 56.

[0077] Processor 51 is a circuit element that controls and performs calculations on external device 5. Processor 51 is configured similarly to processor 42. Examples of processor 51 include, but are not limited to, CPUs, DSPs, ASPs, microcomputers, PLCs, FPGAs, ASICs, and ICs. Processor 51 may also have a multi-core structure. Memory 52 may include main memory and auxiliary memory. The main memory consists of random access memory (RAM) and read-only memory (ROM), etc. Examples of auxiliary memory include semiconductor memory and hard disk drives.

[0078] Input device 53 is a device for receiving input from the user of external device 5. Examples of input device 53 may also include a touch panel, keyboard, and mouse. Output device 54 is a device for outputting information to external device 5. Examples of output device 54 may also include a display and a speaker.

[0079] Communication interface 55 is the hardware that enables external device 5 to send and receive data with sensor module 3 via communication network NW1. Communication interface 55 may also conform to a specific communication protocol. Communication interface 56 is the hardware that enables external device 5 to send and receive data with devices located outside vehicle V (e.g., a server (not shown) that can be connected via communication network NW2) via communication network NW2. Communication network NW2 can be configured via wired communication, wireless communication, or a combination thereof. Examples of communication network NW2 may include one or more of the following: Internet, intranet, WAN, LAN, Bluetooth (registered trademark), Wi-Fi, and mobile communication networks. Communication interface 56 may also conform to a specific communication protocol.

[0080] The processor 51, memory 52, input device 53, output device 54, communication interface 55, and communication interface 56 can also be connected via bus 57 to enable mutual communication.

[0081] Next, refer to Figures 5-8 Provide a detailed description of the sensor signals. Figure 5 It is used to explain the action on Figure 1 The force diagram of the sensor module shown. Figure 6 It is used to explain from Figure 1 The diagram shows the sensor signal output by the sensor. Figure 7 This is a diagram illustrating an example of sensor signals during constant-speed driving. Figure 8 This is a diagram illustrating an example of sensor signals during acceleration.

[0082] exist Figure 5 In the specific example shown, the sensor module 3 is disposed between the outer flange of the rim 23 and the bead of the tire 22, and is in contact with both the flange of the rim 23 and the bead of the tire 22. For the piezoelectric element 31, the weight W of the vehicle V acts as the pressing force via the wheel 21 (rim 23), and the reaction force R from the road surface acts as the pressing force via the tire 22. The piezoelectric element 31 outputs a sensor signal corresponding to the pressing force generated by the wheel 21 and the tire 22. Specifically, the magnitude of the sensor signal varies, for example, according to the magnitude of the pressing force acting on the piezoelectric element 31 and the change in pressing force per unit time. Furthermore, in this embodiment, the sensor module 3 is configured to output a negative sensor signal when the piezoelectric element 31 is subjected to pressing force, but it can also be configured to output a positive sensor signal when subjected to pressing force. As the pressing force acting on the piezoelectric element 31 increases, the absolute value of the sensor signal increases.

[0083] Specifically, during one revolution of the rotating body 2, the portion of the rotating body 2 (the outer circumference of the tire 22) in contact with the road surface changes, thus altering the relative positional relationship between the piezoelectric element 31 and the road surface. For example, the closer the piezoelectric element 31 is to the road surface, the greater the weight W of the vehicle V acting on the piezoelectric element 31 via the wheel 21 (rim 23), and the maximum reaction force R from the road surface acting on the piezoelectric element 31 via the tire 22. When the piezoelectric element 31 is closest to the road surface, the weight W of the vehicle V acting on the piezoelectric element 31 via the wheel 21 (rim 23) is at its maximum, and the maximum reaction force R from the road surface acting on the piezoelectric element 31 via the tire 22 is also at its maximum. At this time, the portion of the tire 22 located between the rim 23 and the road surface is compressed and elastically deformed. As the rotating body 2 rotates further, the weight W of the vehicle V acting on the piezoelectric element 31 via the wheel 21 (rim 23) decreases, and the reaction force R from the road surface acting on the piezoelectric element 31 via the tire 22 also decreases. Subsequently, the compressed tire 22 recovers. At this time, elastic vibration will occur in the tire 22. Under these circumstances, the stress acting on the piezoelectric element 31 will decrease while vibrating.

[0084] exist Figure 6 In the specific example shown, during one revolution of the rotating body 2, the sensor signal has a steep peak bulging in the negative direction, followed by a steep peak bulging in the positive direction. Afterward, the sensor signal decays while vibrating. When the vehicle V travels at a constant speed, the rotational speed of the rotating body 2 is approximately constant. Therefore, as... Figure 7 As shown, this is a waveform that rotates once repeatedly with a constant period. As vehicle V accelerates, the rotational speed of rotating body 2 gradually increases. Therefore, as... Figure 8 As shown, the period of the waveform after one rotation becomes shorter. During acceleration, the reaction force from the road surface sometimes increases; in this case, the absolute value of the negative peak gradually increases.

[0085] Next, refer to Figure 9 This describes the estimation method implemented by processor 42. Figure 9 It means Figure 1 The flowchart shown illustrates the estimation method performed by the processor. The processor 42 can also implement the estimation method, for example, by reading and executing a computer-readable estimation program stored on a non-transitory recording medium. Furthermore, such a recording medium may include, for example, ROM accessible to the processor 42. For example, it may begin after a certain period of time. Figure 9 The series of processes shown.

[0086] First, the processor 42 acquires the sensor signal from the piezoelectric element 31 (step S1). Specifically, the processor 42 may also acquire the sensor signal that has been converted into a digital signal by the AD converter 41.

[0087] Next, the processor 42 generates an interval signal by dividing the sensor signal into specific intervals (step S2). Hereinafter, refer to... Figures 10-13 This section provides some examples of how interval signals are generated and processed, but the generation and processing of interval signals is not limited to these examples. Figures 10-13 This is a diagram illustrating an example of the generation and processing of interval signals. Figures 10-13 The horizontal axis represents time. Figure 10 The vertical axis represents voltage. Figures 11-13 The vertical axis represents the normalized output. The normalized output is the value obtained by dividing the voltage value of the sensor signal by a specified voltage value. Furthermore, the sensor signal sometimes contains noise components. Therefore, the processor 42 can also remove the noise components from the sensor signal and use the noise-removed sensor signal to generate the interval signal.

[0088] like Figure 10 As shown, the processor 42 can also segment the sensor signal into a specific interval signal through window control. Specifically, the processor 42 can also use a window with a time width to select the portion of the sensor signal contained within the window as the interval signal. The time width of the window can be a pre-assigned fixed value or a variable setting value. The time width of the window is, for example, about 5 seconds. The time width of the window is not limited to this; it can be more than 1 second and less than 5 seconds, or it can be more than 5 seconds. The processor 42 shifts the window by a certain time and selects the portion of the sensor signal contained within the shifted window as the next interval signal. The time for shifting the window (shift time) can also be, for example, about 1 second. The shift time is not limited to this; it can also be a time less than the time width of the window. Similarly, the processor 42 selects the interval signal every time the window is shifted. According to this method, for example, by using a fixed window, the processing load of the processor 42 can be reduced.

[0089] The window's time width can also be set dynamically. For example, the processor 42 can also use a high-speed Fourier transform (FFT) to specify the fundamental period of the sensor signal and use the fundamental period as the window's time width.

[0090] As another method, such as Figure 11As shown, processor 42 can also use the maxima and minima contained in the sensor signal to select the interval signal. Specifically, processor 42 can, for example, designate the peak of the interval exceeding a threshold used for determining the maxima in the sensor signal as a maxima. Processor 42 can also, for example, designate the peak (or trough) of the interval below a threshold used for determining the minima in the sensor signal as a minima. The thresholds for determining maxima and minima can also be preset. Furthermore, when maxima and minima alternate in the sensor signal, processor 42 can use this fact as a constraint to designate maxima and minima. In this case, processor 42 can also set a window that successively includes consecutive maxima and minima, and select the portion of the sensor signal contained within the window as the interval signal.

[0091] While the rotating body 2 rotates while in contact with the road surface, under certain conditions, the sensor signal reaches a minimum when the piezoelectric element 31 is closest to the road surface, and a maximum when the piezoelectric element 31 leaves the road surface (when the pressure applied to the piezoelectric element 31 is released). In this case, the interval containing consecutive maximum and minimum values ​​can be equivalent to the sensor signal for one rotation of the rotating body 2. Therefore, according to this method, even when the rotational speed of the rotating body 2 changes, the sensor signal for one rotation of the rotating body 2 can be selected as an interval signal. In this case, according to this method, as the specific interval mentioned above, an interval for one rotation of the rotating body 2 can be selected, and the processor 42 can generate an interval signal by dividing the sensor signal into intervals for one rotation of the rotating body 2.

[0092] As another method, such as Figure 12 As shown, processor 42 can also use zero-crossing points contained in the sensor signal to select an interval signal. Specifically, processor 42 uses, for example, the zero-crossing points in a particular sensor signal when the sensor signal changes from a negative value to a positive value. Furthermore, processor 42 sets a window between two consecutive zero-crossing points and selects the portion of the sensor signal contained within that window as the interval signal.

[0093] While the rotating body 2 is in contact with the road surface and rotating, under certain conditions, during the period when the piezoelectric element 31 is closest to the road surface and then leaves the road surface, the sensor signal abruptly changes from a minimum value to a maximum value. In this case, the zero-crossing point where the sensor signal changes from a negative value to a positive value occurs when the piezoelectric element 31 is closest to the road surface and then leaves the road surface. Therefore, the interval defined by two consecutive zero-crossing points can be equivalent to the sensor signal for one rotation of the rotating body 2. As described above, according to this method, even when the rotational speed of the rotating body 2 changes, the sensor signal for one rotation of the rotating body 2 can be selected as an interval signal. In this case, according to this method, as the specific interval mentioned above, an interval for one rotation of the rotating body 2 can be selected, and the processor 42 can generate an interval signal by dividing the sensor signal into intervals for one rotation of the rotating body 2.

[0094] Furthermore, aside from when the piezoelectric element 31 is closest to the road surface and then moves away from it, the sensor signal sometimes changes from a negative value to a positive value. In this case, the processor 42 can further use a condition such as a value greater than the predetermined value of the change (rate of change) of the sensor signal per unit time to specify a zero-crossing point.

[0095] As another method, such as Figure 13 As shown, the processor 42 can also use the acceleration signal output from the acceleration sensor disposed on the wheel 21 to select the interval signal. This acceleration sensor can, for example, be disposed at the center of the wheel 21. Specifically, the processor 42 sets one cycle of the acceleration signal as a window and selects the portion of the sensor signal contained within the window as the interval signal.

[0096] As the rotating body 2 rotates, the direction of the gravitational acceleration detected by the accelerometer changes, thus the acceleration signal has a periodic waveform. For example, when the rotational speed of the rotating body 2 is fixed, the acceleration signal becomes a sine wave. In this case, one period of the acceleration signal corresponds to one revolution of the rotating body 2. Therefore, according to this method, even when the rotational speed of the rotating body 2 changes, the sensor signal for one revolution of the rotating body 2 can be selected as an interval signal. In this case, according to this method, as the specific interval mentioned above, an interval of one revolution of the rotating body 2 can be selected, and the processor 42 can generate an interval signal by dividing the sensor signal into intervals of one revolution of the rotating body 2.

[0097] Acceleration signals sometimes contain noise components. Therefore, processor 42 can also remove noise components from the acceleration signal and use the noise-removed acceleration signal to implement... Figure 13 The method shown.

[0098] Next, the processor 42 estimates the state of the rotating body 2 based on the interval signal (step S3). As described above, the state of the rotating body 2 estimated by the processor 42 includes, for example, at least one of the tilt angle, slip angle, load applied to the rotating body 2, and air pressure. That is, the parameters representing the state of the rotating body 2 may also include the tilt angle, slip angle, load, and air pressure. When each parameter changes, the waveform of the sensor signal changes. The degree of influence of each parameter on the waveform of the sensor signal may also be different.

[0099] The following is for reference Figures 14-23 Explain the degree of influence of each parameter on the waveform of the sensor signal. Figure 14 It is a diagram used to illustrate the reaction force from the road surface when the outward camber angle is 0 degrees. Figure 15 It is a diagram used to illustrate the reaction force from the road surface at the point of positive outward inclination. Figure 16 It is a diagram used to illustrate the reaction force from the road surface at the negative outward slope. Figure 17 This is a diagram showing an example of the sensor signal for each tilt angle. Figure 18 It is a diagram used to illustrate the slip angle. Figure 19 This is a diagram used to illustrate the forces acting on the sensor module when a slip angle is generated. Figure 20 This is a diagram showing an example of the sensor signal for each slip angle. Figure 21 It is a graph used to illustrate the peak-to-peak value and the second peak value. Figure 22 It is a graph showing the relationship between peak-to-peak value and attenuation rate when slip angle, outward tilt angle, load, and air pressure change. Figure 23 yes Figure 22 A magnified view of a portion of the image.

[0100] like Figures 14-16 As shown, the reaction force on the rotating body 2 from the road surface RS changes as the camber angle θ changes. The camber angle θ can be expressed, for example, as the tilt angle of the rotating body 2 when viewed from the front of the vehicle V. Furthermore, the camber angle θ can also be expressed, for example, as the tilt of the rotating body 2 relative to the road surface RS. Figures 14-16 In the specific example shown, the camber angle θ represents the angle formed by the central axis CX1 of the rotating body 2 and the normal direction of the road surface RS. The central axis CX1 is the vertical axis of the rotating body 2. When the upper end of the rotating body 2 is tilted outward, the camber angle θ is positive. This state can be represented as the upper end of the rotating body 2 tilting in the positive direction (positive camber). When the upper end of the rotating body 2 is tilted inward, the camber angle θ is negative. This state can be represented as the upper end of the rotating body 2 tilting in the negative direction (negative camber). Furthermore, in Figures 14-16 In the specific example shown, the upper end of the rotating body 2 represents the end opposite to the road surface RS.

[0101] like Figure 14As shown, when the camber angle θ is 0 degrees, the road surface RS exerts an equal reaction force on the part of the rotating body 2 (tire 22) in contact with the road surface RS. Figure 15 As shown, when the outward inclination angle θ is positive, the reaction force from the road surface RS increases as the body moves towards the outer end 2a of the rotating body 2. Figure 16 As shown, when the outward tilt angle θ is negative, the reaction force from the road surface RS increases as the body moves toward the inner end 2b of the rotating body 2.

[0102] As an example of this embodiment, the case where the sensor module 3 is disposed at the outer end 2a (outer rim) will be described. In this case, as... Figure 17 As shown, as the outboard angle θ increases, the reaction force on the piezoelectric element 31 from the road surface RS increases. Therefore, as the outboard angle θ increases, the peak-to-peak value of the sensor signal increases. The peak-to-peak value can also be expressed, for example, as... Figure 17 The absolute value of the difference between the minimum value in the negative direction and the maximum value in the positive direction. Furthermore, due to the reaction force from the road surface RS, the bead of tire 22 approaches the flange of rim 23, thus pressing the piezoelectric element 31 against both the bead of tire 22 and the flange of rim 23. Therefore, the degree of freedom of the piezoelectric element 31 is reduced. In this embodiment, the degree of freedom of the piezoelectric element 31 can also represent, for example, the degree of deformability of the piezoelectric element 31. Consequently, as the outward tilt angle θ increases, the post-peak vibration of the sensor signal tends to decrease.

[0103] On the other hand, as the camber angle θ decreases, the reaction force on the piezoelectric element 31 from the road surface RS decreases. Consequently, as the camber angle θ decreases, the peak-to-peak value of the sensor signal decreases. Furthermore, the force exerted by the tire bead and the flange of the rim 23 on the piezoelectric element 31 weakens, thus increasing the degree of freedom of the piezoelectric element 31. Consequently, as the camber angle θ decreases, the post-peak vibration of the sensor signal tends to increase.

[0104] like Figure 18 As shown, the slip angle It is the tilt angle of the rotating body 2 when viewed from above (e.g., when looking down at the vehicle V or the rotating body 2 existing on the road surface). Specifically, it is the slip angle. This is the angle formed by the orientation CX2 of the rotating body 2 and the travel direction F of the vehicle V. The orientation CX2 of the rotating body 2 can, for example, be an orientation orthogonal to the direction extending from the rotation axis AX of the rotating body 2 and approximately parallel to the road surface. Hereinafter, to illustrate the slip angle when the front end of the rotating body 2 tilts outward relative to the travel direction F towards the vehicle V... Indicated as a positive value. The slip angle when the front end of rotating body 2 tilts inward toward the vehicle V relative to the direction of travel F. This is represented as a negative value. Furthermore, in... Figure 18The diagram shows a rotating body 2 on the right side of vehicle V. Within this rotating body 2, with the direction of travel F as the reference, the right direction is the outer side of vehicle V, and the left direction is the inner side of vehicle V. Similarly, in the rotating body 2 on the left side of vehicle V, with the direction of travel F as the reference, the left direction is the outer side of vehicle V, and the right direction is the inner side of vehicle V.

[0105] like Figure 19 As shown, when the slip angle As the angle changes, the degrees of freedom of the piezoelectric element 31 also change. When the value is positive, the force exerted by the tire bead of the tire 22 on the flange of the rim 23 increases as it moves towards the outer end 2a of the rotating body 2. In this case, for example, the pressing force of the tire 22 and rim 23 at the outer end 2a (outer rim side) of the rotating body 2 is greater than the pressing force of the tire 22 and rim 23 at the inner end 2b (inner rim side) of the rotating body 2. When the sensor module 3 is positioned at the outer end 2a (outer rim), the piezoelectric element 31 is pressed by the tire bead of the tire 22, thus reducing the degree of freedom of the piezoelectric element 31. Therefore, as... Figure 20 (especially in) Figure 20 As shown in the figure (when the slip angle is positive), it can suppress the vibration after the peak of the sensor signal.

[0106] On the other hand, at the slip angle When the value is negative, a force similar to pulling the tire bead of the tire 22 is applied to the flange of the rim 23 as it moves towards the outer end 2a of the rotating body 2. In this case, for example, the pressing force of the tire 22 and rim 23 at the outer end 2a (outer rim side) of the rotating body 2 is smaller than the pressing force of the tire 22 and rim 23 at the inner end 2b (inner rim side) of the rotating body 2. Therefore, the force of the tire bead pressing the piezoelectric element 31 is reduced, and the degree of freedom of the piezoelectric element 31 increases. Therefore, as... Figure 20 As shown, the vibration after the peak of the sensor signal becomes larger.

[0107] Even the slip angle The reaction force from the road surface acting on the piezoelectric element 31 may not change as much as it does. Conversely, the slip angle may sometimes change. The larger the slip angle, the greater the force exerted by the tire bead on the piezoelectric element 31. Therefore, depending on the situation, the slip angle may vary. As the value increases, the peak-to-peak value of the sensor signal increases slightly.

[0108] When the load changes, the force exerted on the piezoelectric element 31 from the vehicle body changes. Specifically, as the load increases, the force exerted on the rotating body 2 from the vehicle body increases. At this time, due to the increased pressing force applied to the sensor module 3, the peak-to-peak value of the sensor signal increases. On the other hand, as the load decreases, the force exerted on the rotating body 2 from the vehicle body decreases. At this time, due to the decreased pressing force applied to the sensor module 3, the peak-to-peak value of the sensor signal decreases. That is, due to the change in load, the voltage generated by the piezoelectric element 31 changes, therefore, the waveform of the sensor signal stretches and contracts along the longitudinal axis (voltage value).

[0109] When air pressure changes, the elastic modulus of tire 22 changes. Higher air pressure makes tire 22 less prone to contraction, thus reducing the reaction force exerted on the piezoelectric element 31 from the road surface. Consequently, the peak-to-peak value of the sensor signal decreases. Conversely, lower air pressure makes tire 22 more prone to contraction, thus increasing the reaction force exerted on the piezoelectric element 31 from the road surface. Consequently, the peak-to-peak value of the sensor signal increases. In other words, the voltage change generated by the piezoelectric element 31 according to the change in air pressure causes the waveform of the sensor signal to stretch or contract along the longitudinal axis.

[0110] The processor 42 estimates the state of the rotating body 2 based on the degree of influence of each parameter on the waveform of the sensor signal. The following describes some examples of the state estimation process of the rotating body 2, but the state estimation process of the rotating body 2 is not limited to these examples.

[0111] As a method, processor 42 can also estimate the state of rotating body 2 based on multiple distinct waveform characteristics calculated from the interval signal. These multiple waveform characteristics include values ​​derived from at least one of the following: the maximum value of the interval signal, the minimum value of the interval signal, the difference between the maximum and minimum values ​​in the interval signal (peak-to-peak value), the standard deviation of the interval signal, the variance of the interval signal, the average value of the interval signal, the median of the interval signal, the value at the inflection point of the interval signal, and the wavelength of the interval signal. For example, as multiple waveform characteristics, one or more values ​​from the examples above can be used directly, a combination of two or more values ​​can be used, or values ​​calculated from these values ​​using appropriate formulas can be used.

[0112] Alternatively, for each parameter (outward tilt angle, slip angle, load, and air pressure) representing the state of the rotating body 2, the relationship between the change in that parameter and the change in each waveform characteristic can be pre-determined and stored. Specifically, for each parameter representing the state of the rotating body 2, the relationship between the change in that parameter and the change in each waveform characteristic can also be stored. Here, the number of waveform characteristics used in the state estimation process can be the same as or greater than the number of parameters representing the state of the rotating body 2 that are the objects of estimation.

[0113] As an example, this illustrates the changes in peak-to-peak value and attenuation rate relative to variations in various parameters. The attenuation rate is the rate of decay of the sensor signal waveform generated when the piezoelectric element 31 is away from the road surface. The attenuation rate is obtained by dividing the second peak value by the peak-to-peak value. For example... Figure 21 As shown, as a second peak value, for example, the peak value of the voltage bulging in the positive direction after the maximum value in the interval signal can be used. If the interval signal does not have a peak value bulging in the positive direction other than the maximum value, for example, the value at the inflection point where the rate of change of the slope of the interval signal changes from positive to negative after the maximum value can also be used as the second peak value.

[0114] exist Figure 22 and Figure 23 In the example shown, the state of rotating body 2 is used as the reference state when the outboard angle is 0 degrees, the slip angle is 0 degrees, the load is 5300N, and the air pressure is 240kPa. The reference state represents the state of rotating body 2 under a specific speed, a specific outboard angle, a specific slip angle, a specific load, and a specific air pressure. Under the reference state, the peak-to-peak value is 2.9V, and the attenuation rate is 0.042.

[0115] exist Figure 22 and Figure 23 In the examples shown, as the outclination angle increases, the peak-to-peak value increases, and the attenuation rate decreases. Specifically, when the outclination angle is changed only from -5 degrees to +5 degrees from the baseline state, the peak-to-peak value increases from 1.6V to 3.7V, and the attenuation rate decreases from 0.077 to 0.030. As the slip angle increases, the peak-to-peak value increases, and the attenuation rate decreases. Specifically, when the slip angle is changed only from -1 degree to +1 degree from the baseline state, the peak-to-peak value increases from 2.6V to 3.4V, and the attenuation rate decreases from 0.200 to -0.460.

[0116] exist Figure 22 and Figure 23 In the example shown, as the load increases, the peak-to-peak value increases, and the attenuation rate increases. Specifically, when the load is changed only from the base state from 3000 N to 7600 N, the peak-to-peak value increases from 1.8 V to 3.8 V, and the attenuation rate increases from 0.037 to 0.052. As the air pressure increases, the peak-to-peak value decreases, and the attenuation rate decreases. Specifically, when the air pressure is changed only from 160 kPaN to 260 kPa, the peak-to-peak value decreases from 2.9 V to 2.6 V, and the attenuation rate decreases from 0.100 to 0.083.

[0117] Processor 42 can also estimate the state of rotating body 2 by comparing measured values ​​with reference values. The reference values ​​are the values ​​of each waveform characteristic in the reference state of rotating body 2. The measured values ​​are the values ​​of each waveform characteristic obtained from the interval signal. Specifically, if the measured value differs from the reference value in any waveform characteristic, processor 42 determines that the state of rotating body 2 has changed from the reference state. Furthermore, processor 42 can also calculate the values ​​of the parameters of the estimated object based on the amount of change in each waveform characteristic. As an example, processor 42 can also use... Figure 22 and Figure 23 The relationship shown presumes the state of the rotating body 2. In this case, the processor 42 may, for example, set two parameters in the state of the rotating body 2 as presumed objects, assume that the parameters other than the presumed objects do not change, and calculate the values ​​of the two parameters as presumed objects from the measured values.

[0118] Processor 42 can also assume that any one of the multiple parameters has changed, and infer which parameter has changed from the amount of change in each waveform characteristic (the value obtained by subtracting the reference value from the measured value).

[0119] Alternatively, the processor 42 can also use clustering methods such as the k-means method to determine the state of the rotating body 2. Specifically, the processor 42 classifies the interval signal based on the measured values ​​of each waveform characteristic obtained from the interval signal, according to any of the clusters set according to the parameters of the rotating body 2. The processor 42 infers the state of the rotating body 2 as the state corresponding to the cluster with the classified interval signal.

[0120] As another method, processor 42 can also use the estimation model M to estimate the state of the body of revolution 2. The estimation model M can, for example, be a machine learning model learned specifically for estimating the state of the body of revolution 2. (See also...) Figure 24 Explain the presumed model M. Figure 24 This is a diagram used to illustrate the hypothetical model. For example... Figure 24 As shown, the estimation model M can also be generated by machine learning using the learning data. As a machine learning algorithm, algorithms such as random forest, LightGBM, and deep learning can also be used. Furthermore, the estimation model M can be, for example, a classifier that classifies the state of the rotating body 2 into specific categories (e.g., the range of the outward tilt angle, the range of the slip angle, and the range of the load), or a regression model that outputs the estimated values ​​of the state of the rotating body 2.

[0121] The learning data may include, for example, a range signal generated from sensor signals pre-acquired by sensor module 3, and a feature vector calculated from this range signal. The feature vector may also include values ​​of multiple waveform characteristics as elements. For example, the feature vector may include the maximum value, minimum value, peak-to-peak value, standard deviation, variance, average value, median, inflection point (e.g., second peak value), wavelength, and one or more values ​​calculated from these values ​​as elements. Not limited to this, the feature vector may also be all the data contained in the range signal itself (e.g., the voltage value itself). Labels corresponding to the state of the rotating body 2 may also be assigned to the learning data. Examples of labels may include normal driving, changes in camber angle, and changes in slip angle. As labels, the amount of parameter variation may also be used. For example, as labels, the range of camber angle, the range of slip angle, the range of load, and the range of air pressure may also be used.

[0122] The estimation model M receives the characteristic vector calculated from the interval signal as input and outputs the estimation result. The estimation result represents information about the state of the rotating body 2. The estimation result may also include information about which parameter changes. The estimation result may also include the amount of change of each parameter. The estimation result may also include the range of each parameter (e.g., the range of the outboard angle, the range of the slip angle, the range of the load, and the range of the air pressure, etc.).

[0123] exist Figure 24 In the example, the presumption model M is configured to presume all states in a single model. However, it is not limited to this; the presumption model M may also contain multiple presumption models that set up each presumption parameter (e.g., outboard angle, slip angle, load, and air pressure). Each presumption model presumes the states assigned to it.

[0124] Next, the processor 42 outputs the estimation result (step S4). In this embodiment, the processor 42 may also output the estimation result to the external device 5 via the communication interface 43, for example. When the estimation result is received, the external device 5 may also use the output device 54 to display the estimation result to the passenger. For example, if the output device 54 is a display, the output device 54 displays the estimation result. Not limited to this, the external device 5 may also provide the received estimation result to other devices installed in the vehicle V. The external device 5 may also provide the received estimation result to devices located outside the vehicle V (e.g., a server that can be connected via the communication network NW2).

[0125] The above steps complete the series of processes for the estimation method.

[0126] In the estimation system 1, estimation method, and recording medium described above, a sensor signal corresponding to the pressing force generated by the wheel 21 and tire 22 is output from the piezoelectric element 31 disposed between the wheel 21 and tire 22. The weight W from the vehicle V (body) acts on the piezoelectric element 31 via the wheel 21, and the reaction force R from the road surface acts on the piezoelectric element 31 via the tire 22. These forces can change according to the state of the rotating body 2, therefore, the state of the rotating body 2 can be estimated based on the sensor signal. Therefore, the state of the rotating body 2 can be estimated by a simple structure in which the piezoelectric element 31 (sensor module 3) is disposed between the wheel 21 and tire 22.

[0127] In the case where the wheel 21 includes a rim 23, a tire 22 is mounted on the rim 23. In this case, a piezoelectric element 31 is disposed between the rim 23 and the tire 22. Therefore, the state of the rotating body 2 can be estimated by a simple structure in which the piezoelectric element 31 (sensor module 3) is disposed between the rim 23 and the tire 22.

[0128] When the piezoelectric element 31 is positioned at the center of the rotating body 2 in the direction extending from the rotation axis AX, the sensor signal changes in the same manner, for example, even if the camber angle changes in either the positive or negative direction. On the other hand, in the above embodiment, when the piezoelectric element 31 is positioned at the outer end 2a, the sensor signal changes asymmetrically with respect to changes in the camber angle, etc. Here, "asymmetrically changing sensor signal" means that the sensor signal differs depending on whether the camber angle changes in the positive or negative direction. For example, when the camber angle increases in the positive direction, the reaction force from the road surface increases towards the outer end 2a of the rotating body 2, thus increasing the peak-to-peak value of the sensor signal. Conversely, when the camber angle decreases, the reaction force from the road surface increases towards the inner end 2b of the rotating body 2, thus decreasing the peak-to-peak value of the sensor signal. In other words, by positioning the piezoelectric element 31 at the outer end 2a of the rotating body 2, the accuracy of estimating the state of the rotating body 2 can be improved.

[0129] On the other hand, even if the piezoelectric element 31 is disposed at the inner end 2b, the sensor signal changes asymmetrically with respect to changes in the tilt angle, etc. In this case, the reaction force from the road surface at the inner end 2b of the rotating body 2 changes according to the tilt angle. Therefore, even in a structure where the piezoelectric element 31 is disposed at the inner end 2b, the estimation accuracy of the state of the rotating body 2 can be improved.

[0130] As described above, the interval signal can also be generated, for example, by dividing the rotating body 2 into intervals corresponding to one revolution of the rotating body 2. When the rotating body 2 rotates, the portion of the rotating body 2 in contact with the road surface changes, and therefore, the relative positional relationship between the piezoelectric element 31 and the contact portion changes. Therefore, under certain conditions, the sensor signal exhibits periodicity, with the same waveform shape for each revolution of the rotating body 2. In this case, by analyzing the interval signal of one revolution of the rotating body 2, the state of the rotating body 2 can be estimated.

[0131] The waveform characteristics calculated from the interval signal can serve as an indicator of the state of the rotating body 2. Therefore, by using multiple distinct waveform characteristics calculated from the interval signal, the accuracy of estimating the state of the rotating body 2 can be improved.

[0132] The maximum value, minimum value, peak-to-peak value, standard deviation, variance, average value, median, and inflection point value of the interval signal are values ​​representing the waveform characteristics of the interval signal. These values ​​can change as the state of the rotating body 2 changes. Therefore, by using a value based on at least one of these values, the accuracy of estimating the state of the rotating body 2 can be improved.

[0133] The processor 42 can also use the estimation model M to estimate the state of the rotating body 2. In this case, by fully learning the estimation model M, the estimation accuracy of the state of the rotating body 2 can be improved.

[0134] As mentioned above, sometimes the tendencies of sensor signal changes with variations in tilt angle, slip angle, load, and air pressure differ. In such cases, it is possible to estimate tilt angle, slip angle, load, and air pressure separately.

[0135] As described above, the piezoelectric element 31 is presumably designed to generate electrical energy under pressure. For example, the processor 42 can also be configured to operate using the electrical energy generated by the piezoelectric element 31. With this configuration, the processor 42 can operate without receiving power from the outside of the sensor module 3. Therefore, wiring for supplying power from the outside of the sensor module 3 is not required, thus simplifying the structure of the presumed system 1.

[0136] As described above, the piezoelectric element 31 and processor 42 can also constitute the sensor module 3. This sensor module 3 can also be installed on the rotating body 2. The processor 42 can also be configured to output the estimation result to an external device 5 located outside the rotating body 2. In this configuration, the sensor signal is processed within the sensor module 3, and the estimation result is output to the external device 5. In this case, compared to a configuration where the sensor signal is processed in the external device 5, the amount of communication between the sensor module 3 and the external device 5 can be reduced. Therefore, the power required for communication can be reduced, and thus, the electrical energy generated by the piezoelectric element 31 can be effectively utilized.

[0137] Next, refer to Figure 25 The estimation system of another embodiment is described. Figure 25 This is a structural diagram that roughly represents a hypothetical system of another embodiment. Figure 25 The main difference between the estimation system 1A shown is that it includes multiple sensor modules 3A and a control module 4 instead of a single sensor module 3.

[0138] The main difference between each sensor module 3A and sensor module 3 lies in the fact that it does not include the AD converter 41, processor 42, communication interface 43, power converter 44, and energy storage device 45 as circuit elements.

[0139] Each sensor module 3A may, for example, have the same physical structure as sensor module 3, and may also include a piezoelectric element 31, a back plate 32, a substrate 33, a substrate 34, and a substrate 35. Multiple sensor modules 3A may, for example, be disposed on the same rotating body 2. Each sensor module 3A is disposed between the wheel 21 (rim 23) and the tire 22. Specifically, each sensor module 3A is disposed between the flange of the rim 23 and the bead of the tire 22, and is in contact with both the flange of the rim 23 and the bead of the tire 22.

[0140] In this embodiment, some sensor modules 3A are disposed on the outer end 2a (outer rim), and some sensor modules 3A are disposed on the inner end 2b (inner rim). The number of sensor modules 3A disposed on the outer end 2a can be the same as the number of sensor modules 3A disposed on the inner end 2b, or they can be different. All sensor modules 3A can also be disposed on either the outer end 2a or the inner end 2b.

[0141] Control module 4 processes sensor signals output from multiple sensor modules 3A disposed on a rotating body 2. Control module 4 can also be disposed, for example, at the center of wheel 21. Figure 25In the specific example shown, the control module 4 includes an AD converter 41, a processor 42, a communication interface 43, a power converter 44, and a power storage device 45. Furthermore, the AD converter 41 and the communication interface 43 can also be integrated with the processor 42. The AD converter 41, processor 42, communication interface 43, power converter 44, and power storage device 45 differ from those of the sensor module 3 at the points where the processed signals are multiple sensor signals.

[0142] Next, refer to Figures 26-28 This section describes a configuration example for multiple sensor modules 3A. Figure 26 This is a diagram showing an example of a sensor module configuration. Figure 27 This is a diagram showing an example of the sensor signal for each tilt angle. Figure 28 This is a diagram showing an example of the sensor signal for each slip angle. In Figure 26 In the example shown, one sensor module 3A is disposed at the outer end 2a (outer rim), and another sensor module 3A is disposed at the inner end 2b (inner rim). The sensor module 3A disposed at the outer end 2a is referred to as "sensor module 3Ao", and the sensor module 3A disposed at the inner end 2b is referred to as "sensor module 3Ai".

[0143] Specifically, sensor module 3Ao is disposed at its outer end 2a between wheel 21 (rim 23) and tire 22. More specifically, sensor module 3Ao is disposed between the outer flange of rim 23 and the bead of tire 22, and contacts both the outer flange of rim 23 and the bead of tire 22. Sensor module 3Ai is disposed at its inner end 2b between wheel 21 (rim 23) and tire 22. More specifically, sensor module 3Ai is disposed between the inner flange of rim 23 and the bead of tire 22, and contacts both the inner flange of rim 23 and the bead of tire 22.

[0144] As the outward tilt angle θ increases, the reaction force on the piezoelectric element 31 of the sensor module 3Ao from the road surface increases. Therefore, as... Figure 27 As shown, as the camber angle θ increases, the peak-to-peak value of the sensor signal (hereinafter, sometimes referred to as the "first sensor signal") output from the piezoelectric element 31 of the sensor module 3Ao increases. Furthermore, due to the reaction force from the road surface, the bead of the tire 22 approaches the outer flange of the rim 23, thus pressing the piezoelectric element 31 of the sensor module 3Ao against both the bead of the tire 22 and the outer flange of the rim 23. Therefore, the degree of freedom of the piezoelectric element 31 of the sensor module 3Ao is reduced. Consequently, as the camber angle θ increases, post-peak vibration of the first sensor signal is suppressed.

[0145] As the camber angle θ decreases, the reaction force on the piezoelectric element 31 of the sensor module 3Ao from the road surface decreases. Therefore, as the camber angle θ decreases, the peak-to-peak value of the first sensor signal decreases. Furthermore, the force exerted by the outer flanges of the tire bead 22 and rim 23 on the piezoelectric element 31 of the sensor module 3Ao weakens, thus increasing the degree of freedom of the piezoelectric element 31 of the sensor module 3Ao. Therefore, as the camber angle θ decreases, the post-peak vibration of the first sensor signal increases.

[0146] On the other hand, as the camber angle θ increases, the reaction force on the piezoelectric element 31 of the sensor module 3Ai from the road surface decreases. Therefore, as the camber angle θ increases, the peak-to-peak value of the sensor signal (hereinafter, sometimes referred to as the "second sensor signal") output from the piezoelectric element 31 of the sensor module 3Ai decreases. Furthermore, the force exerted by the inner flanges of the tire bead 22 and the rim 23 on the piezoelectric element 31 of the sensor module 3Ai weakens, thus increasing the degree of freedom of the piezoelectric element 31 of the sensor module 3Ai. Therefore, as the camber angle θ increases, the post-peak vibration of the second sensor signal increases.

[0147] As the camber angle θ decreases, the reaction force on the piezoelectric element 31 of the sensor module 3Ai from the road surface increases. Therefore, as the camber angle θ decreases, the peak-to-peak value of the second sensor signal increases. Furthermore, due to the reaction force from the road surface, the tire bead of the tire 22 approaches the inner flange of the rim 23, thus pressing the piezoelectric element 31 of the sensor module 3Ai against both the tire bead of the tire 22 and the inner flange of the rim 23. Therefore, the degree of freedom of the piezoelectric element 31 of the sensor module 3Ai decreases. Thus, as the camber angle θ decreases, post-peak vibration of the second sensor signal is suppressed.

[0148] With the slip angle As the tire 22 enlarges, its bead approaches the outer flange of the rim 23, thus pressing the piezoelectric element 31 of the sensor module 3Ao against it. Consequently, the degree of freedom of the piezoelectric element 31 of the sensor module 3Ao decreases. Therefore, as... Figure 28 As shown, with the slip angle The increase suppresses post-peak vibrations in the first sensor signal. This is due to the increase in the slip angle. As the size decreases, the force exerted by the outer flanges of the tire bead 22 and rim 23 on the piezoelectric element 31 of the sensor module 3Ao weakens, thus increasing the degree of freedom of the piezoelectric element 31 of the sensor module 3Ao. Therefore, as... Figure 28 As shown, as the slip angle φ decreases, the vibration after the peak of the first sensor signal increases.

[0149] On the other hand, as the slip angle φ increases, the force exerted by the inner flanges of the tire bead 22 and rim 23 on the piezoelectric element 31 of the sensor module 3Ai weakens, thus increasing the degree of freedom of the piezoelectric element 31 of the sensor module 3Ai. Therefore, as... Figure 28 As shown, as the slip angle φ increases, the post-peak vibration of the second sensor signal increases. As the slip angle φ decreases, the tire bead of tire 22 approaches the inner flange of rim 23, therefore, the piezoelectric element 31 of sensor module 3Ai is pressed by the tire bead of tire 22. Therefore, the degree of freedom of the piezoelectric element 31 of sensor module 3Ai decreases. Therefore, as... Figure 28 As shown, as the slip angle φ decreases, the vibration after the peak of the second sensor signal is suppressed.

[0150] like Figure 28 As shown, when receiving the first sensor signal and the second sensor signal, the AD converter 41 can also convert each signal into a digital signal and output the digital first sensor signal and the digital second sensor signal to the processor 42. When obtaining the digital first sensor signal from the AD converter 41, the processor 42 can also generate a first interval signal by dividing the first sensor signal into specific intervals. When obtaining the digital second sensor signal from the AD converter 41, the processor 42 can also generate a second interval signal by dividing the second sensor signal into specific intervals.

[0151] The generation and processing of the first interval signal and the second interval signal can be the same as the generation and processing of the interval signal in estimation system 1. Processor 42 can also estimate the state of the rotating body 2 based on the first interval signal and the second interval signal. The state estimation processing of the rotating body 2 can also be the same as the state estimation processing of the rotating body 2 in estimation system 1. Processor 42 can also output the estimation result.

[0152] In estimation system 1A, the structure common to estimation system 1 achieves the same effect. In estimation system 1A, the piezoelectric element 31 of sensor module 3Ao and the piezoelectric element 31 of sensor module 3Ai are arranged on opposite sides of each other in the direction of rotation of the rotating body 2 extending relative to the rotation axis AX. For example, the piezoelectric element 31 of sensor module 3Ao may also be arranged on the outer end side relative to the center of the rotating body 2 in the direction of rotation of the rotation axis AX. For example, the piezoelectric element 31 of sensor module 3Ai may also be arranged on the inner end side relative to the center of the rotating body 2 in the direction of rotation of the rotation axis AX.

[0153] The sensor signals output from the piezoelectric element 31 of sensor module 3Ao and the piezoelectric element 31 of sensor module 3Ai exhibit different changes depending on the state of the rotating body 2. Specifically, as... Figure 27 and Figure 28 As shown, sometimes opposite changes occur in the sensor signal output from the piezoelectric element 31 of sensor module 3Ao and the sensor signal output from the piezoelectric element 31 of sensor module 3Ai. When using two sensor signals that produce such opposite changes to estimate the state of the rotating body 2, the effects of interference and other disturbances can be reduced. As a result, compared to a structure (estimation system 1) that uses only one sensor signal to estimate the state of the rotating body 2, the estimation accuracy of the state of the rotating body 2 can sometimes be improved.

[0154] Next, refer to Figure 29 This describes a presumption system for yet another implementation method. Figure 29 This is a structural diagram that roughly represents another embodiment of the proposed system. Figure 29 The estimation system 1B shown differs from the estimation system 1 mainly in the points where sensor module 3B is included in place of sensor module 3, and also in the points where external device 5B is included.

[0155] Sensor module 3B differs from sensor module 3 primarily in that it does not contain processor 42. In sensor module 3B, AD converter 41 outputs digital sensor signals to communication interface 43. Communication interface 43 then transmits the digital sensor signals to external device 5B via communication network NW1.

[0156] The external device 5B differs from the external device 5 mainly in that it includes a processor 51B instead of the processor 51. The processor 51B mainly differs from the processor 51 mainly in that it estimates the state of the rotating body 2 based on sensor signals sent from the sensor module 3B. The processor 51B may, for example, be configured to estimate the state of the rotating body 2 in the same way as the processor 42. The processor 51B may also, for example, output the estimation result to the output device 54.

[0157] In estimation system 1B, the same structure as estimation system 1 achieves the same effect. Furthermore, in estimation system 1B, the processor 51B of the external device 5B estimates the state of the rotating body 2. In this case, constraints such as power consumption, physical size, and cooling are mitigated; therefore, a processor with higher computing power than the processor 42 included in the sensor module 3 can be used as processor 51B. Therefore, by using such processor 51B, the time required to estimate the state of the rotating body 2 can be shortened.

[0158] Next, refer to Figure 30 This describes a presumption system for yet another implementation method. Figure 30 This is a structural diagram that roughly represents another embodiment of the proposed system. Figure 30The presumed system 1C shown differs from the presumed system 1B mainly in the points where external device 5C is included in place of external device 5B, and also in the points where server 6 is included.

[0159] The main difference between external device 5C and external device 5B is that it includes a processor 51 instead of processor 51B. Processor 51, like the processor 51 in external device 5, is a circuit element that performs control and calculations within external device 5C. When receiving sensor signals from sensor module 3B, communication interface 55 outputs the sensor signals to communication interface 56. Communication interface 56 can also be configured to send sensor signals to server 6 via communication network NW2.

[0160] Server 6 may, for example, have the same hardware structure as external device 5C. The processor of server 6 may also estimate the state of rotating body 2 based on sensor signals sent from external device 5C. In this case, the processor of server 6 may, for example, estimate the state of rotating body 2 through the same processing as processor 42.

[0161] In estimation system 1C, the same structure as estimation system 1B achieves the same effect. Furthermore, in estimation system 1C, the processor of server 6 estimates the state of the rotating body 2. According to this structure, for example, even if sensor modules 3B are installed on the rotating bodies 2 of multiple different vehicles V, it is not necessary to install the function of estimating the state of the rotating body 2 on the external devices 5 in each vehicle V. That is, server 6 can estimate the state of the rotating body 2 installed in each vehicle V based on signals collected via the external devices 5 in each vehicle V.

[0162] Furthermore, the estimation system, estimation method, and recording medium disclosed herein are not limited to the embodiments described above.

[0163] For example, sensor modules 3 and 3B and control module 4 may not include power converter 44 and energy storage device 45. In this case, sensor modules 3 and 3B and control module 4 may include a battery or receive power from an external source.

[0164] Furthermore, in the above embodiment, the piezoelectric elements 31 of sensor modules 3, 3A, and 3B are disposed at the outer end 2a or the inner end 2b, but they can also be disposed at positions corresponding to the structure of the wheel 21 and the tire 22. The piezoelectric elements 31 of sensor modules 3, 3A, and 3B only need to be disposed near the outer or inner end of the center of the rotating body 2 in a direction extending beyond the rotation axis AX. Figure 26In the example shown, the piezoelectric element 31 of the sensor module 3Ao only needs to be positioned closer to the outer end than the center mentioned above, and the piezoelectric element 31 of the sensor module 3Ai only needs to be positioned closer to the inner end than the center mentioned above.

[0165] Any reference to elements using terms such as "first" and "second" as used in this disclosure does not limit the quantity or order of these elements. These terms are used in this disclosure as a simple way to distinguish between two or more elements. Therefore, reference to a first element and a second element does not imply that only two elements can be used, or that the first element must precede either of the second elements in some form. In this disclosure, the use of a first element does not presuppose the existence of more than two elements.

Claims

1. A presumption system comprising: A first sensor is configured between a wheel and a tire mounted on the wheel, and outputs a first sensor signal corresponding to the pressing force generated by the wheel and the tire. and processor, The processor is configured to, The first interval signal is generated by dividing the first sensor signal into specific intervals; Determine the attenuation rate from the signal in the first interval; and Based on the attenuation rate, the state of the rotating body including the wheel and the tire is estimated. The attenuation rate is the attenuation rate of the waveform of the signal in the first interval, and the attenuation rate is the value obtained by dividing the second peak value by the peak-to-peak value.

2. The estimation system according to claim 1, wherein, The second peak value is the positively bulging peak value of the voltage generated after the maximum value in the interval signal, or... If the interval signal does not have any peaks that bulge in the positive direction except for the maximum value, the second peak value is the value at the inflection point where the rate of change of the interval signal's slope changes from positive to negative after the maximum value.

3. The estimation system according to claim 1, wherein, The first sensor is disposed between the rim and the tire contained in the wheel.

4. The estimation system according to claim 1 or 2, wherein, The rotating body includes a first end and a second end, which serve as two ends in the direction of the rotation axis of the rotating body. The first sensor is positioned closer to the first end than the center of the rotating body in the direction of the rotation axis.

5. The estimation system according to claim 4, wherein, It also includes a second sensor, which can be configured between the wheel and the tire, and outputs a second sensor signal corresponding to the second pressing force generated by the wheel and the tire. The second sensor is positioned at a second location closer to the second end than the center. The processor generates a second interval signal by dividing the second sensor signal into the specific intervals, and also infers the state based on the second interval signal.

6. The estimation system according to claim 1 or 2, wherein, The specific interval is the interval of one revolution of the rotating body.

7. The estimation system according to claim 1 or 2, wherein, The processor estimates the state based on multiple different waveform characteristics calculated from the first interval signal.

8. The estimation system according to claim 7, wherein, The plurality of waveform characteristics include values ​​based on at least one of the following: the maximum value of the first interval signal; the minimum value of the first interval signal; the difference between the maximum value and the minimum value; the standard deviation of the first interval signal; the variance of the first interval signal; the average value of the first interval signal; the median of the first interval signal; and the value of the first interval signal at the inflection point.

9. The estimation system according to claim 1 or 2, wherein, The processor uses a machine learning model to estimate the state.

10. The estimation system according to claim 1 or 2, wherein, The state includes at least one of the following: outward tilt angle, slip angle, load applied to the rotating body, and air pressure.

11. The estimation system according to claim 1 or 2, wherein, The first sensor and the processor constitute a sensor module. The sensor module is disposed on the rotating body. The processor outputs the estimation result to an external device located outside the rotating body.

12. The estimation system according to claim 1 or 2, wherein, The first sensor is a piezoelectric element that generates electrical energy in response to the pressure applied. The processor operates using the electrical energy generated by the piezoelectric element.

13. The estimation system according to claim 1 or 2, wherein, The first sensor is a piezoelectric element that generates electrical energy in response to the pressure applied. The processor infers the state of the rotating body by using the voltage or current of the electrical energy generated by the piezoelectric element as the first sensor signal.

14. A method of estimation, comprising: Sensor signals corresponding to the pressing force generated by the wheel and the tire are acquired from a sensor disposed between the wheel and the tire mounted on the wheel; Interval signals are generated by dividing the sensor signals into specific intervals; Determine the attenuation rate from the interval signal; and Based on the attenuation rate, the state of the rotating body including the wheel and the tire is estimated. The attenuation rate is the attenuation rate of the waveform of the signal in the interval, and the attenuation rate is the value obtained by dividing the second peak value by the peak-to-peak value.

15. A computer-readable, non-transitory recording medium containing a presumed program for causing a computer to execute: Sensor signals corresponding to the pressing force generated by the wheel and the tire are acquired from a sensor disposed between the wheel and the tire mounted on the wheel; Interval signals are generated by dividing the sensor signals into specific intervals; Determine the attenuation rate from the interval signal; and Based on the attenuation rate, the state of the rotating body including the wheel and the tire is estimated. The attenuation rate is the attenuation rate of the waveform of the signal in the interval, and the attenuation rate is the value obtained by dividing the second peak value by the peak-to-peak value.

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