Anomaly detection device, anomaly detection program, and anomaly detection method

Abstract

Based on a signal representing the wheel's rotation speed, abnormalities in the wheel can be detected at an earlier stage. [Solution] The anomaly detection device performs frequency analysis on a first indicator showing the fluctuation in rotational speed during one rotation of the wheel at each point in time to calculate the gain of each rotational order component, and calculates the total gain by summing the gains of a predetermined number of rotational order components. The anomaly detection device determines that an anomaly has occurred in the wheel if the rate of increase of the total gain per predetermined time is equal to or greater than the reference rate of increase.

Description

[Technical Field]

[0001] The present invention relates to an abnormality detection device, an abnormality detection method, and an abnormality detection program that detect abnormalities occurring in each of the multiple wheels of a vehicle and identify the wheel in which the abnormality occurred. [Background technology]

[0002] Early detection of abnormalities in the wheels and the ability to take countermeasures are crucial for maintaining the proper operation of a vehicle. Examples of wheel abnormalities include slight wheel wobble and damage to the tires. Wheel wobble is typically caused by loose wheel nuts. If driving continues with loose wheel nuts, the loosening will gradually progress, potentially leading to the wheel falling off. Damage to the tires includes pinch cuts. A pinch cut occurs when the tire is significantly deformed by an impact, causing the sidewall to get pinched between the road surface and the flange of the wheel rim, resulting in damage to the structural components within the tire. In severe cases of pinch cuts, the tire can rapidly depressurize, rendering the vehicle inoperable. In mild cases of pinch cuts, there may be no rapid depressurization, and the driver may not notice it. However, continuing to drive with such a pinch cut can lead to a sudden puncture or blowout.

[0003] For example, Patent Document 1, shown below, discloses the following abnormality detection method for appropriately detecting abnormalities occurring in a wheel based on a signal representing the rotational speed of the wheel. Specifically, in this abnormality detection method, the computer first sequentially acquires a signal representing the rotational speed of the wheel as pulses with rising edges, and calculates a first index that represents the temporal variation of the rising edges of each of the multiple pulses corresponding to one rotation of the wheel. From this first index, the computer calculates the level (gain) of each of the multiple rotational order components, and standardizes the calculated gain of each rotational order component using "the mean value and standard deviation of the gain of each rotational order component in the absence of an abnormality." Then, the computer uses, for example, the sum of the squares of the standardized gains of each rotational order component as a second index for determining whether or not there is an abnormality in the wheel. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-146447 [Overview of the project] [Problems that the invention aims to solve]

[0005] The inventors of this case have been investigating a method for detecting abnormalities in a wheel based on a signal representing the rotational speed of the wheel, and have discovered the following: Specifically, the inventors have discovered that by calculating the sum of the gains of multiple rotational order components from the first indicator described in Patent Document 1, and observing the change in the sum of these gains over time, it is possible to determine the presence or absence of a wheel abnormality at an earlier stage.

[0006] In one aspect, the present invention has been made in view of these circumstances, and its purpose is to provide an abnormality detection device, an abnormality detection program, and an abnormality detection method that can detect abnormalities occurring in a wheel at an earlier stage based on a signal representing the rotational speed of the wheel. [Means for solving the problem]

[0007] An abnormality detection device according to an aspect of the present invention is an abnormality detection device that detects an abnormality occurring in a wheel, and includes a signal acquisition unit, a first index calculation unit, a spectrum calculation unit, a total gain calculation unit, and a determination unit. The signal acquisition unit sequentially acquires, as pulses having rising edges, signals representing the rotational speed of the wheel. The first index calculation unit calculates, at each time point, a first index representing the temporal variation in the rising edge of each of the pulses corresponding to one rotation of the wheel. The spectrum calculation unit calculates, for each time point, a frequency spectrum of the rotational order from the first order to the m-th order (where m is an integer of 2 or more) of the first index by performing frequency analysis on the first index at each time point. The total gain calculation unit calculates, as the total gain at each time point, the sum of the gains of each of a plurality of predetermined rotational order components of the frequency spectrum at each time point. The determination unit determines that an abnormality has occurred in the wheel when the increase rate of the total gain per predetermined time calculated from the total gain at each time point is equal to or higher than a predetermined reference increase rate.

[0008] The above abnormality detection device may further include a tightening time information acquisition unit that acquires tightening time information indicating the most recent tightening time point, which is the time point when the wheel nut was most recently tightened normally. The determination unit may determine that an abnormality has occurred in the wheel nut that attaches the wheel of the wheel to the hub as an abnormality of the wheel when the increase rate is equal to or higher than the reference increase rate. The determination unit may further determine that an abnormality has occurred in the hub bearing fixed to the hub that is the rotational center of the wheel when the total gain at a time point when the elapsed period from the most recent tightening time point is equal to or shorter than a predetermined reference period is equal to or higher than a predetermined reference value.

[0009] The above abnormal detection device may further include a map information acquisition unit, a nut information acquisition unit, and a notification unit. The map information acquisition unit may acquire map information. Such map information may be map information capable of specifying the position of the vehicle equipped with the wheels at each time point and the position of the nut repair operator who can repair the wheel nut within a predetermined distance from the position of the vehicle at each time point. The nut information acquisition unit may acquire nut information for specifying a wheel nut that can be replaced with the wheel nut in which an abnormality has occurred. When it is determined by the determination unit that an abnormality has occurred in the wheel nut, the notification unit may perform the following notification. That is, the notification unit may perform at least one of (1) notifying the occupant of the vehicle of the determination result that an abnormality has occurred in the wheel nut and the position of the nut repair operator, and (2) notifying the nut repair operator of the determination result that an abnormality has occurred in the wheel nut and the nut information.

[0010] The above abnormal detection device may further include a map information acquisition unit, a bearing information acquisition unit, and a notification unit. The map information acquisition unit may acquire map information. Such map information may be map information capable of specifying the position of the vehicle equipped with the wheels at each time point and the position of the bearing repair operator who can repair the hub bearing within a predetermined distance from the position of the vehicle at each time point. The bearing information acquisition unit may acquire bearing information for specifying a hub bearing that can be replaced with the hub bearing in which an abnormality has occurred. When it is determined by the determination unit that an abnormality has occurred in the hub bearing, the notification unit may perform the following notification. That is, the notification unit may perform at least one of (1) notifying the occupant of the vehicle of the determination result that an abnormality has occurred in the hub bearing and the position of the bearing repair operator, and (2) notifying the bearing repair operator of the determination result that an abnormality has occurred in the hub bearing and the bearing information.

[0011] An abnormality detection method according to one aspect of the present invention is an abnormality detection method for detecting abnormalities occurring in a wheel, which is executed by a computer, and includes the following. Furthermore, an abnormality detection program according to one aspect of the present invention is an abnormality detection program for detecting abnormalities occurring in a wheel, which causes a computer to execute the following. The signal representing the rotational speed of the wheel is sequentially acquired as a pulse with a rising edge. - At each point in time, calculate a first index that represents the temporal variation of the rise time of each pulse corresponding to one rotation of the wheel. • By performing frequency analysis on the first index at each time point, the frequency spectra of the rotational orders from the 1st to the mth order (where m is an integer of 2 or greater) of the first index are calculated for each time point. - Calculate the sum of the gains of a predetermined number of rotational order components of the frequency spectrum at each time point as the total gain at each time point. - If the rate of increase of the total gain per predetermined time, calculated from the total gain at each point in time, is equal to or greater than a predetermined standard rate of increase, it is determined that an abnormality has occurred in the wheel. [Effects of the Invention]

[0012] In this invention, a signal representing the rotational speed of the wheel is sequentially acquired as pulses with rising edges, and at each point in time, a first index is calculated that represents the temporal variation of the rising edges of each pulse corresponding to one rotation of the wheel. Then, in this invention, the frequency spectrum of the rotational orders from the 1st to the mth order (where m is an integer of 2 or more) of the first index at each point in time is calculated by frequency analysis of the first index at each point in time, and the sum of the gains of a predetermined number of rotational order components of the frequency spectrum at each point in time is calculated as the total gain at each point in time. Here, the inventors(s) have discovered that by observing the change in the sum of the gains at each point in time over time, it is possible to determine the presence or absence of a wheel abnormality at an earlier stage. Therefore, in this invention, if the rate of increase of the total gain per predetermined time, calculated from the total gain at each point in time, is greater than or equal to a predetermined standard rate of increase, it is determined that a wheel abnormality has occurred. Accordingly, according to this invention, it is possible to detect abnormalities occurring in the wheel at an earlier stage based on a signal representing the rotational speed of the wheel. [Brief explanation of the drawing]

[0013] [Figure 1] A schematic diagram showing the general configuration of a vehicle equipped with an anomaly detection device according to one embodiment of the present invention. [Figure 2] A block diagram showing the electrical configuration of the anomaly detection device. [Figure 3] A flowchart illustrating the flow of anomaly detection processing. [Figure 4] A flowchart illustrating the flow of anomaly detection processing. [Figure 5] A flowchart illustrating the process for handling abnormality notifications. [Figure 6] An example of the gain of the frequency spectrum of the rotational order of the first index, comparing the case where no abnormality occurs and the case where an abnormality occurs in the wheel. [Figure 7] An example of determining wheel abnormalities based on the change in total gain over time. [Figure 8] An example of anomaly detection timing in cases where the total gain itself is compared to a threshold to detect anomalies, and cases where anomalies are detected based on the rate of increase of the total gain per predetermined time. [Figure 9] This example demonstrates that when detecting anomalies based on the total gain itself, a threshold must be set for each wheel. [Figure 10] A diagram illustrating an example of a method for detecting abnormalities in the hub bearing. [Figure 11] A diagram illustrating the pulses obtained from a rotational speed sensor. [Modes for carrying out the invention]

[0014] The following describes an anomaly detection device, an anomaly detection program, and an anomaly detection method according to one embodiment of the present invention, with reference to the drawings.

[0015] <1. Overview> Figure 1 is a schematic diagram showing how the abnormality detection system 1 according to this embodiment is mounted on a vehicle VH. The vehicle VH is a four-wheeled vehicle and is equipped with a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR. The vehicle VH is equipped with a front axle 4a and a rear axle 4b, and the wheels FL, FR, RL, and RR are attached to hub units 40 fixed to the left and right ends of the front and rear axles 4a and 4b, respectively. In this embodiment, when there is no need to particularly distinguish between the left front wheel FL, the right front wheel FR, the left rear wheel RL, and the right rear wheel RR, they may simply be referred to as "wheels". Similarly, when there is no need to particularly distinguish between the front axle 4a and the rear axle 4b, they may simply be referred to as "axles".

[0016] The hub unit 40 is, for example, a wheel support structure that rotatably supports a wheel. The hub unit 40 according to this embodiment includes a hub that serves as the rotation center of the wheel and a hub bearing fixed to the hub. The hub is a ring-shaped member to which the wheel is attached and rotates together with the wheel. The hub bearing is a bearing that rotatably supports the hub with respect to the axle. In the hub unit 40, the hub and the hub bearing may be formed integrally, or the hub bearing formed integrally with the hub may rotatably support the wheel.

[0017] Each wheel FL, FR, RL, and RR comprises a wheel 7b and a tire 7a mounted thereon. The wheel 7b is attached to and secured to the hub unit 40 (particularly the hub of the hub unit 40) by fastening members (not shown). The fastening members are typically multiple wheel nuts with threads. By engaging the fastening members with hub bolts (not shown) on the hub unit 40 side and tightening the screws appropriately, each wheel is securely fixed to each hub unit 40 without loosening.

[0018] The abnormality detection system 1 comprises a control unit 2 as an abnormality detection device and a sensor unit 3 that detects information representing the rotational speed of the wheels FL, FR, RL, and RR. Based on the signal output from the sensor unit 3, the control unit 2 detects whether or not an abnormality has occurred in at least one of the wheels FL, FR, RL, and RR, and if an abnormality is detected, it has the function of alerting the driver or other person via a display 6 provided in the vehicle VH. When the control unit 2 detects an abnormality in at least one of the wheels FL, FR, RL, and RR, it may identify the wheel in which the abnormality occurred (abnormal wheel) and notify the driver or other person of the identified abnormal wheel via a display 6 provided in the vehicle VH.

[0019] Abnormalities occurring in the wheels FL, FR, RL, and RR include at least one of the following: wheel rattle or damage to the tire 7a included in it. Factors causing wheel rattle include damage to the hub bolts, damage to the wheel nuts, loose wheel nuts, and damage (failure) to the hub bearings. Particularly typical is loose wheel nuts, followed by failure of the hub bearings. When the wheel 7b is properly fixed to the hub unit 40, there is no damage to the wheel nuts, hub bolts, and hub bearings, and the wheel nuts and hub bolts are tightened to the appropriate torque. If looseness occurs between the wheel nuts and hub bolts, mechanical play occurs between the wheel 7b and the hub unit 40, causing the wheel to rattle. Similarly, if the hub bearing fails, mechanical play occurs between the wheel 7b and the hub unit 40, causing the wheel to rattle. Furthermore, if the vehicle VH continues to be driven with loose wheel nuts, the vibrations applied to the wheels will cause the wheel nuts to loosen further, eventually leading to the wheel nuts coming off the hub bolts and the wheel detaching from the hub unit 40 (resulting in wheel detachment). Also, if the vehicle VH continues to be driven with a faulty hub bearing unattended, the vehicle may experience increased vibration, difficulty steering, instability, or the wheel detaching from the hub unit 40. For this reason, it is important to detect wheel looseness early and eliminate the cause.

[0020] On the other hand, a typical type of damage to tire 7a is pinch cuts that occur while driving. A pinch cut is a severance of internal structural members of tire 7a caused by the tire 7a deforming significantly due to impacts from uneven road surfaces or obstacles, resulting in the sidewall being pinched between the wheel rim flange and the road surface or obstacle (pinching). These structural members are typically the carcass cords that make up the carcass inside tire 7a. Severing of the carcass cords is irreparable, and the tire 7a itself must be replaced. In severe pinch cuts, the rubber is also severed along with the carcass cords due to pinching, causing a rapid depressurization of tire 7a and rendering the vehicle VH inoperable.

[0021] On the other hand, with minor pinch cuts, the rubber does not break and the air pressure is maintained, making it difficult for the driver to notice. However, even with minor pinch cuts, if driving continues, the tire may suddenly puncture or burst, so it is necessary to detect it early and replace tire 7a. The anomaly detection system 1 can detect and warn of pinch cuts regardless of their severity, but it is more important to detect and warn of minor pinch cuts, which are less likely to be noticed by the driver.

[0022] Therefore, the control unit 2 determines whether an abnormality has occurred in each of the multiple wheels of the vehicle VH, and if it determines that an abnormality has occurred in at least one wheel, it notifies the occupants of the vehicle VH of the abnormality and prompts them to, for example, repair the abnormality. In particular, the control unit 2 distinguishes between "an abnormality occurring in the wheel nut that attaches the wheel 7b of the wheel to the hub" and "an abnormality occurring in the hub bearing fixed to the hub, which is the center of rotation of the wheel." For example, if the control unit 2 determines that an abnormality has occurred in the wheel when "the elapsed time since the most recent tightening time TMS, which is the time when the wheel nut was most recently tightened normally, is less than or equal to a predetermined standard period (bearing judgment standard period RPB)," it executes the following process. That is, the control unit 2 determines that the "abnormality that occurred in the wheel" is an "abnormality that occurred in the hub bearing" rather than an "abnormality that occurred in the wheel nut." When the control unit 2 determines that an abnormality has occurred in the hub bearing, it distinguishes this abnormality from "an abnormality occurring in the wheel nut" and notifies the occupants of the vehicle VH (e.g., the driver). In other words, the control unit 2 distinguishes between "an abnormality occurring in the wheel nut" and "an abnormality occurring in the hub bearing" and notifies the driver of the occurrence of the abnormality. Therefore, the driver can appropriately identify the parts that need to be repaired, replaced, or retightened.

[0023] Furthermore, when the control unit 2 detects a wheel abnormality, it may transmit information useful for repairing the abnormality and the occurrence of the abnormality to a repair shop or other facility capable of repairing the abnormality. For example, when the control unit 2 detects a wheel nut abnormality, it may transmit information about the occurrence of the abnormality and nut information IN, which identifies a wheel nut that can be replaced with the abnormal wheel nut, to a nut repair business SPN or other facility capable of repairing the abnormality. For example, when the control unit 2 detects a hub bearing abnormality, it may transmit information about the occurrence of the abnormality and bearing information IB, which identifies a hub bearing that can be replaced with the abnormal hub bearing, to a bearing repair business SPB or other facility capable of repairing the abnormality. By receiving such information from the control unit 2, the repair shop (at least one of the nut repair business SPN and the bearing repair business SPB) can know in advance that it may receive a request from the occupants of the vehicle VH for repair or replacement of an abnormal wheel (at least one of the wheel nut and the hub bearing). Furthermore, by receiving this information, repair shops can prepare the necessary parts for repairs and replacements in advance, and can perform repairs and replacements promptly when requested.

[0024] <2. Anomaly Detection System> Figure 2 is a block diagram showing the electrical configuration of the anomaly detection system 1. The following describes each element of the anomaly detection system 1.

[0025] [Control Unit] The control unit 2 is a vehicle-mounted computer in terms of hardware, and includes an I / O interface 8, a CPU (Central Processing Unit) 9, a ROM (Read Only Memory) 10, a RAM (Random Access Memory) 11, and a non-volatile, rewritable storage device 12. The I / O interface 8 is a communication device for communicating with external devices such as the sensor unit 3, the display unit 6, the communication device 7, and an ECU (Electronic Control Unit, vehicle-mounted control device) not shown, which is installed in the vehicle VH. The ROM 10 stores a program 13 for controlling the operation of various parts of the vehicle VH. The program 13 is written to the ROM 10 from a storage medium 14 such as a CD-ROM. The CPU 9 reads the program 13 from the ROM 10 and executes it, thereby virtually operating as a signal acquisition unit 20, a first index calculation unit 21, a spectrum calculation unit 22, a total gain calculation unit 23, a determination unit 24, a fastening time information acquisition unit 25, a map information acquisition unit 26, a nut information acquisition unit 27, a bearing information acquisition unit 28, and a notification unit 29. Details of the operation of each part 20-29 will be described later. The storage device 12 is composed of a hard disk, flash memory, etc. Note that the storage location of the program 13 may be the storage device 12 instead of the ROM 10. The RAM 11 and the storage device 12 are used as appropriate for the calculations of the CPU 9. For example, information such as the reference growth rate RRI, the bearing judgment reference period RPB, and the bearing judgment reference value RVB, which the control unit 2 uses to detect abnormalities in the wheels, may be stored in advance in at least one of the RAM 11 and the storage device 12. Details of each piece of information will be described later.

[0026] [Sensor Unit] The sensor unit 3 comprises four rotating bodies 31 that rotate with the wheels FL, FR, RL, and RR, and four sensors 30 that continuously detect the physical quantities changed by the rotating bodies 31 and output detection signals. The mounting positions of the rotating bodies 31 are not particularly limited, as long as they are mounted so as to be rotatable with each wheel, with respect to the rotation axis of each wheel. The sensors 30 are mounted near the corresponding rotating body 31, on the non-rotating parts of the vehicle body. Each sensor 30 is connected to the control unit 2 via a communication line 5.

[0027] The rotating body 31 is, but is not limited to, a gear made of a magnetic material in this embodiment. The sensor 30 is, but is not limited to, a magnetic field sensor containing a permanent magnet and a coil in this embodiment, and is fixed to the vehicle body so as to face the side surface of the rotating body 31. The magnetic field generated by the permanent magnet of the sensor 30 changes as the rotating body 31 rotates and the teeth sequentially pass in front of the sensor 30, generating an induced electromotive force in the coil. The waveform of the induced electromotive force is a sine wave with a frequency proportional to the rotational speed of the rotating body 31. This sine wave has a period of the same number as the number of teeth (N) of the rotating body 31, and one period corresponds to one rotation of the wheel. The sensor 30 outputs a sine wave signal based on the induced electromotive force to the control unit 2 in real time as a signal representing the rotational speed of the wheel.

[0028] [Display] The display unit 6 can be implemented in any form, such as a liquid crystal display element, liquid crystal monitor, plasma display, and organic EL (Electro-Luminescence) display, as long as it can inform the driver that there is a problem with at least one wheel. The problem includes at least one of a problem with the wheel nut and a problem with the hub bearing. The display unit 6 can distinguish between a problem with the wheel nut and a problem with the hub bearing and notify the driver or other occupants of the vehicle VH. In addition to the message that "there is a problem with at least one wheel," the display unit 6 may also provide the driver with information identifying the wheel in which the problem occurred (the wheel with the problem). The wheel with the problem may be a wheel in which at least one of the wheel nut and hub bearing has a problem. For example, the display unit 6 can have four lamps corresponding to each wheel FL, FR, RL, RR, arranged according to the actual arrangement of the wheels. The display unit 6 may distinguish the wheel with the problem from the wheels without the problem and inform the driver, for example, by controlling the illumination state of each lamp according to a control signal from the control unit 2. The mounting position of the display unit 6 can be selected as appropriate, but it is preferable to install it in a location easily visible to the driver, such as on the instrument panel. When the control unit 2 is connected to a car navigation system, the monitor for the car navigation system can also be used as the display unit 6. Warnings can be output to the display unit 6 in the form of icons, text information, etc. In addition, warnings may be output in the form of voice or warning sounds via the speaker installed in the vehicle VH.

[0029] [Communication equipment] Communication device 7 is a wireless communication device that enables communication with a repair shop or the like that can repair the wheel of vehicle VH that has malfunctioned. In this embodiment, communication device 7 performs communication with the repair shop or the like in accordance with the instructions of control unit 2, and transmits to the repair shop or the like that a malfunction has occurred in the wheel of vehicle VH, and information useful for repairing the malfunction. For example, when control unit 2 detects a malfunction in a wheel nut, communication device 7 transmits the determination result that a malfunction has occurred in the wheel nut, and nut information IN, to a nut repair business SPN or the like, in accordance with the instructions of control unit 2. For example, when control unit 2 detects a malfunction in a hub bearing, communication device 7 transmits the determination result that a malfunction has occurred in the hub bearing, and bearing information IB, to a bearing repair business SPB or the like, in accordance with the instructions of control unit 2.

[0030] [ECU] Vehicle VH is further equipped with an ECU (not shown). This ECU is, for example, an information system ECU that controls a navigation system. Control unit 2 can communicate with the information system ECU via, for example, a CAN (Controller Area Network) or other in-vehicle network and receive map information MPI from the information system ECU. Map information MPI is information that can identify the position of vehicle VH at each point in time and the position of a repair shop located within a predetermined distance from the position of vehicle VH at each point in time. As the position of the repair shop, map information MPI is information that can identify the position of at least one of a nut repair business SPN and a bearing repair business SPB located within a predetermined distance from the position of vehicle VH at each point in time.

[0031] Vehicle VH may be equipped with a management system ECU in addition to an information system ECU, which manages maintenance information MTI related to the maintenance and servicing of each part of the vehicle VH. Maintenance information MTI includes, for example, the following information as information related to the maintenance and servicing of each of the multiple wheel nuts equipped on the vehicle VH. Specifically, maintenance information MTI includes information indicating the most recent tightening time TMS (tightening time information IT), which is the time when the wheel nuts of the vehicle VH were most recently tightened correctly, and nut information IN, which identifies wheel nuts that can be replaced with the wheel nuts of the vehicle VH. Nut information IN indicates, for example, the size, material, model, part number, etc., for each of the multiple wheel nuts equipped on the vehicle VH. Similarly, maintenance information MTI includes, for example, bearing information IB, which identifies hub bearings that can be replaced with the hub bearings of the vehicle VH, as information related to the maintenance and servicing of each of the multiple hub bearings equipped on the vehicle VH. Bearing information IB indicates, for example, the size, material, model, part number, etc., for each of the multiple hub bearings equipped on the vehicle VH. The control unit 2 communicates with the management system ECU via the in-vehicle network and can receive tightening time information IT, nut information IN, and bearing information IB from the management system ECU. Maintenance information MTI may be registered and updated by at least one person, such as the occupant of the vehicle VH (e.g., the driver), the manager of the vehicle VH, the repair shop, the manufacturer of the vehicle VH (automobile manufacturer), or the manufacturers of each part of the vehicle VH.

[0032] <3. Anomaly detection processing> The following describes the anomaly detection method for detecting anomalies in the wheels FL, FR, RL, and RR, which is performed by the anomaly detection system 1 according to this embodiment. Figures 3 and 4 are flowcharts showing the flow of the anomaly detection process. Figure 5 is a flowchart showing the flow of the anomaly notification process that the anomaly detection system 1 (in particular, the control unit 2) executes when it is determined in the anomaly detection process that "an anomaly has occurred in at least one of the wheels FL, FR, RL, and RR." Specifically, Figure 5(A) is a flowchart showing the flow of the nut anomaly notification process executed when it is determined that an anomaly has occurred in the wheel nut of at least one wheel. Figure 5(B) is a flowchart showing the flow of the bearing anomaly notification process executed when it is determined that an anomaly has occurred in the hub bearing of at least one wheel. To facilitate understanding of the anomaly detection system 1 (in particular, the control unit 2), an overview of the control unit 2 will first be explained using Figures 6 to 10.

[0033] (Regarding anomaly detection methods) The control unit 2 sequentially acquires a signal representing the rotational speed of the wheel as a pulse with a rising edge, and at each point in time, calculates a first index representing the temporal variation of the rising edge of each pulse corresponding to one rotation of the wheel. Next, the control unit 2 calculates the total gain TG for each point in time from the first index at each point in time. That is, the control unit 2 calculates the frequency spectrum of the rotational order from the 1st to the mth order of the first index for each point in time by frequency analysis of the first index at each point in time. In this embodiment, m is an integer of 2 or more. Then, the control unit 2 calculates the gain G of each of a predetermined number of rotational order components of the frequency spectrum at each point in time. j The sum of (where j is an integer from 1 to m) is calculated as the total gain TG at each point in time. The control unit 2 determines that an abnormality has occurred in the wheel if the rate of increase RGI of the total gain TG per predetermined time PT, calculated from the total gain TG at each point in time, is equal to or greater than a predetermined standard rate of increase RRI.

[0034] Here, the gain G for each rotational order is calculated from the first indicator. jWhen a malfunction occurs in the wheel, the gain G changes from what it was when there was no malfunction, and becomes larger than when there was no malfunction, as illustrated in Figure 6. However, in the example shown in Figure 6, depending on the rotational order, the gain G differs between when there is a malfunction in the wheel and when there is no malfunction. j Some of the changes are small, and for example, some show almost no change. Therefore, the control unit 2 controls the gain G of each of the predetermined multiple rotational order components. j The sum of these values ​​is calculated as the total gain TG, and this total gain TG is used to determine whether or not an abnormality has occurred in the wheel.

[0035] In particular, the control unit 2 detects abnormalities in the wheel by observing the change in the total gain TG over time. For example, as shown in Figure 7, the control unit 2 determines that an abnormality has occurred in the wheel if the total gain TG is increasing, and in the illustrated example, it determines that the wheel nuts are becoming loose. In this embodiment, the control unit 2 determines that an abnormality has occurred in the wheel if the increase rate RGI of the total gain TG per predetermined time PT, calculated from the total gain TG at each point in time, is equal to or greater than the reference increase rate RRI. Through this process, the control unit 2 achieves the effects illustrated in Figures 8 and 9.

[0036] As described above, the gain G for each rotational order is calculated from the first indicator. j When a malfunction occurs in the wheel, it becomes larger than when there is no malfunction. Therefore, as illustrated in Figure 8, the gain G of each of the predetermined multiple rotational order components is... jOne approach is to compare the total gain TG, which is the sum of the two values, with a predetermined threshold, and determine that a wheel malfunction has occurred if the total gain TG exceeds the threshold. However, the inventors have discovered that by observing the temporal change in the total gain TG at each point in time, it is possible to determine the presence or absence of a wheel malfunction at an earlier stage. In other words, instead of "comparing the total gain TG itself with a predetermined threshold," the inventors have discovered that by observing the rate of increase RGI of the total gain TG per predetermined time PT, it is possible to determine the presence or absence of a wheel malfunction at an earlier stage. Specifically, as shown in Figure 8, by determining that a wheel malfunction has occurred when the rate of increase RGI exceeds the reference rate RRI, it is possible to determine the presence or absence of a wheel malfunction at an earlier stage compared to the case where "a wheel malfunction is determined when the total gain TG exceeds a threshold." In the example shown in Figure 8, the abnormality detection timing in this embodiment (the abnormality detection timing when detecting an abnormality by comparing the growth rate RGI with the reference growth rate RRI) is significantly earlier than the abnormality detection timing when using a threshold (the abnormality detection timing when detecting an abnormality by comparing the total gain TG itself with a predetermined threshold). Therefore, the control unit 2, which determines that an abnormality has occurred in the wheel when the growth rate RGI of the total gain TG per predetermined time PT, calculated from the total gain TG at each point in time, is equal to or greater than the reference growth rate RRI, can detect abnormalities in the wheel at an earlier stage.

[0037] Furthermore, the gain G for each rotational order. j This is calculated from the first index for each wheel, that is, it is calculated for each wheel. And it is thought that this first index for each wheel is influenced in a way that is unique to each wheel, and this influence appears, for example, as the number of teeth N of each rotating body 31 that rotates with each wheel, that is, as the number of pulses for one rotation of the wheel. Therefore, it is thought that the "gain Gj for each rotation order" also depends on the wheel (especially the number of teeth N of the rotating body 31 for each wheel) (in other words, it is influenced in a way that is unique to each wheel). Naturally, the gain G of each of a given number of rotation order components jThe total gain TG, which is the sum of the values ​​of each wheel, is also thought to be wheel-dependent, meaning that each wheel is affected in a unique way. Therefore, when attempting to detect wheel abnormalities by comparing the total gain TG itself with a predetermined threshold, since the total gain TG is wheel-dependent, the threshold used for comparison with the total gain TG for each wheel must also be set for each wheel. In the example shown in Figure 9, the threshold (1) used for comparison with the total gain TG (1) of wheel (1) is a threshold that can only be used to determine if wheel (1) is abnormal, and is a threshold set for wheel (1). Similarly, the threshold (2) used for comparison with the total gain TG (2) of wheel (2) is a threshold that can only be used to determine if wheel (2) is abnormal, and is a threshold set for wheel (2). For this reason, as illustrated in Figure 9, threshold (1) and threshold (2) have different values.

[0038] In contrast, the growth rate RGI of the total gain TG per predetermined time PT, calculated from the total gain TG at each point in time, is independent of the wheel. The growth rate RGI is the change in the total gain TG at each point in time per predetermined time PT, and not the total gain TG itself at each point in time; therefore, it is independent of the wheel. Figure 9 illustrates that when abnormalities occur in both wheel (1) and wheel (2), the total gain TG(1) for wheel (1) and the total gain TG(2) for wheel (2) show similar changes over time. In other words, when an abnormality occurs in a wheel, the growth rate RGI of the total gain TG for that wheel per predetermined time PT will be the same, independent of the wheel. Therefore, the reference growth rate RRI used for comparison with the growth rate RGI can also be determined independently of the wheel. Accordingly, the control unit 2 can determine whether or not an abnormality has occurred for each wheel by comparing a common reference growth rate RRI for multiple wheels with the growth rate RGI of the total gain TG for each wheel.

[0039] The reference growth rate RRI can be used to determine whether there are abnormalities in the "multiple wheels" of a single vehicle (vehicle VH in this embodiment), as well as in the "multiple wheels" of each of multiple vehicles. For example, the reference growth rate RRI can be used to determine whether there are abnormalities in the "multiple wheels" of a vehicle different from vehicle VH. In other words, the reference growth rate RRI used by the control unit 2 as a "value within a predetermined range common to multiple wheels, independent of the wheel" is a value that can be used in common for multiple vehicles and multiple wheels. The control unit 2 can use this common reference growth rate RRI to determine whether there are abnormalities in each of the "multiple wheels" of each of multiple vehicles.

[0040] (Regarding the targets of anomaly detection) The control unit 2 detects abnormalities in the wheels, and in particular distinguishes between "abnormalities occurring in the wheel nuts" and "abnormalities occurring in the hub bearings." The control unit 2 grasps the "most recent tightening time TMS, which is the time when the wheel nuts were most recently tightened normally," such as the time when the wheel nuts were replaced. Then, as illustrated in Figure 10, the control unit 2 determines that an abnormality has occurred in the hub bearing if the total gain TG remains high even after, for example, the wheel nuts have been replaced. In this embodiment, the control unit 2 determines that an abnormality has occurred in the hub bearing if the total gain TG is equal to or greater than a predetermined standard value (bearing standard value RVB) at a time when the elapsed time from the most recent tightening time TMS is less than or equal to the bearing judgment standard period RPB.

[0041] As described above, the control unit 2 can detect abnormalities in the wheel earlier by comparing the increase rate RGI of the total gain TG with the reference increase rate RRI, compared to comparing the total gain TG itself with a predetermined threshold. A typical cause of abnormalities such as wheel rattling is "abnormalities in the wheel nuts," such as loosening of the wheel nuts. Therefore, in this embodiment, if the increase rate RGI is greater than or equal to the reference increase rate RRI, the control unit 2 determines that there is an abnormality in the wheel, for example, "an abnormality has occurred in the wheel nuts." Through this determination, the control unit 2 can detect "abnormalities in the wheel nuts," which are typical causes of wheel abnormalities, earlier than when comparing the total gain TG itself with a predetermined threshold.

[0042] Furthermore, since the wheel nuts were tightened normally at the most recent tightening time TMS, if a wheel abnormality is detected shortly after the most recent tightening time TMS, it is considered that the cause of the abnormality lies in something other than "an abnormality in the wheel nuts." Therefore, when the elapsed time since the most recent tightening time TMS is less than or equal to the bearing judgment criterion period RPB, the control unit 2 determines that an abnormality has occurred in the hub bearing if the total gain TG is greater than or equal to the bearing judgment criterion value RVB, and notifies the occupants of the vehicle VH accordingly. Through this process, when the control unit 2 detects a wheel abnormality that is thought to have been caused by something other than "an abnormality in the wheel nuts," it can alert the occupants to the possibility of "an abnormality in the hub bearing," which could lead to serious consequences.

[0043] In particular, when detecting a hub bearing abnormality, control unit 2 uses the total gain TG, not the "rate of increase RGI of the total gain TG per predetermined time PT calculated from the total gain TG at each point in time," which was used to detect a wheel nut abnormality. Specifically, control unit 2 uses the "total gain TG at a point in time when the elapsed time from the most recent tightening point TMS is less than or equal to the bearing judgment criterion period RPB," rather than the "rate of increase RGI of the total gain TG," to determine whether or not a hub bearing abnormality has occurred.

[0044] Here, the "rate of increase RGI of total gain TG" is the "rate of increase RGI of total gain TG per predetermined time PT," so in order to calculate the "rate of increase RGI of total gain TG" from the total gain TG at each point in time, the elapsed "predetermined time PT" is required. However, at the point in time when "the elapsed time from the most recent tightening point TMS is less than or equal to the bearing judgment criterion period RPB," if no abnormality has occurred, the total gain TG should be a sufficiently small value. Therefore, at the point in time when "the elapsed time from the most recent tightening point TMS is less than or equal to the bearing judgment criterion period RPB," the control unit 2 determines that an abnormality has occurred in the wheel if the total gain TG is large, without waiting for the aforementioned "predetermined time PT" to elapse. Specifically, the control unit 2 determines that an abnormality has occurred in the hub bearing if the total gain TG at the point in time when "the elapsed time from the most recent tightening point TMS is less than or equal to the bearing judgment criterion period RPB" is greater than or equal to the bearing judgment criterion value RVB. Through this process, the control unit 2 can detect the hub bearing abnormality more quickly than if it were to wait for the aforementioned "predetermined time PT" to elapse before detecting the hub bearing abnormality.

[0045] Furthermore, the "predetermined time PT" used to calculate the rate of increase RGI of the total gain TG from the total gain TG at each point in time should preferably be shorter than the bearing judgment criterion period RPB. For example, the bearing judgment criterion period RPB may be about one month, and the "predetermined time PT" used to calculate the rate of increase RGI may be about one week. To give one example, the rate of increase RGI may be the rate of increase of the total gain TG per week. Next, the processing flow executed by the anomaly detection system 1 (particularly the control unit 2) which has been outlined above will be explained using Figures 3 to 5.

[0046] In step S1 of FIG. 3, the signal acquisition unit 20 sequentially acquires, as pulses having a rising edge, the sine wave signals output from the sensors 30 for each wheel. The signal acquisition unit 20 samples the sine wave signal at a predetermined period to convert it into a pulse as shown in FIG. 11, and calculates the transit time t i for each pulse. The transit time t i corresponds to the time when the tooth (i) of the tooth number i of the rotating body 31 passes in front of the sensor 30. This transit time t i can be measured based on, for example, a signal called a "timestamp" supplied from a clock module mounted on the sensor 30.

[0047] Here, the pitch of the gear of the rotating body 31 is not perfectly uniform, and variations corresponding to the pitch of each tooth occur in each transit time ti during one rotation of the rotating body 31 (see FIG. 11). In step S2, the first index calculation unit 21 calculates a comparison value x i for each of the transit times t mean of the pulses corresponding to the number of teeth N corresponding to one rotation of the wheel, with respect to their average transit time t i according to the following formula. x i =t i / t mean -1

[0048] In the subsequent step S3, the first index calculation unit 21 estimates i a signal representing the comparison value x

Number

Number

number

[0049] The above estimated x with a hat i (k) is the transit time t for tooth (i). i This is a correction coefficient to compensate for variations, and when there is no abnormality in the wheel, it becomes a signal that includes frequency components corresponding to the pitch of each tooth. In other words, the estimated x with hats as described above. i (k) is an example of a first index that represents the temporal variation in the rising edge of pulses corresponding to one rotation of the wheel, which are sequentially acquired by the signal acquisition unit 20. The first index calculation unit 21 calculates a first index that represents the temporal variation in the rising edge of each pulse corresponding to one rotation of the wheel at each point in time. The first index is not limited to this, as long as it is an index that represents the temporal variation in the rising edge of pulses corresponding to one rotation of the wheel.

[0050] Step S4 is a step that includes the loop of steps S5 to S7. In step S4, the spectrum calculation unit 22 calculates the x with hats estimated by frequency analysis. i The frequency spectrum of (k) is derived, and the gain G is based on this. j Steps S5 to S7, which calculate the gain G of the frequency spectrum for rotational orders from the 1st to the mth order, are repeated. As a result, in step S4, the gain G of the frequency spectrum for rotational orders from the 1st to the mth order is calculated. j The following is calculated. In particular, the spectrum calculation unit 22 calculates the first index (x with a hat) at each time point. i By performing frequency analysis on (k), the frequency spectra of the rotational orders from the 1st to the mth order of the first index are calculated. The spectrum calculation unit 22 then calculates the gain G of the frequency spectra of the rotational orders from the 1st to the mth order. j The gain G of the frequency spectrum of rotational orders from the 1st to the mth order at each time point is calculated, and in particular, the gain G of the frequency spectrum of rotational orders from the 1st to the mth order. j This calculates the result. Below, we will explain the process executed in steps S5 to S7, using the first loop as an example.

[0051] In the first loop, the analysis is performed on the first rotational order component, that is, the component that completes one period corresponding to one rotation of the wheel. The spectrum calculation unit 22 first calculates the x with a hat corresponding to one rotation of the wheel. i (k) is passed through a bandpass filter to extract components near the first order of rotation (Step S5).

[0052] In step S6, the spectrum calculation unit 22 applies a window function to the rotation order component extracted in step S5. This process is performed in the following step S7, where the gain G j This is a process for extracting a finite interval before calculating the result. The window function to be applied is not particularly limited; known window functions such as the Hanning window and Hamming window can be applied. From the viewpoint of rapid sidelobe decay, the Blackman window function is preferred.

[0053] In step S7, the spectrum calculation unit 22 calculates the gain G1 of the first rotational order for the signal multiplied by the window function in step S6. Based on Parseval's theorem, the spectrum calculation unit 22 determines the gain G1 for the first rotational order from the time-domain signal. At this point, the first loop ends and the second loop begins.

[0054] In the second loop, the analysis is performed on the second-order rotation component, that is, the component that completes two periods corresponding to one rotation of the wheel. The spectrum calculation unit 22 changes the frequency band of the bandpass filter in step S5 to make it a bandpass filter that passes the frequency band around the second-order rotation component. That is, in step S5 of the second loop, the hatted x corresponding to one rotation of the wheel estimated in step S3 is analyzed. i Components around the second-order rotation are extracted from (k). Then, steps S6 to S7 are executed in the same manner as in the first loop.

[0055] As described above, the spectrum calculation unit 22 repeats steps S5 to S7 for the component that completes j periods corresponding to one rotation of the wheel, while changing the passband frequency range of the bandpass filter each time the number of loops increases by one. As a result, when all loops in step S4 are completed, the gain G for rotational orders from the 1st to the mth order is calculated. j (j=1,2,…,m) is calculated. In particular, the spectrum calculation unit 22 calculates the gain G for the rotation order from the 1st to the mth order at each time point. j The spectrum calculation unit 22 calculates the gain G j The data is stored in RAM 11 or storage device 12. The process from steps S1 to S7 is repeated for each wheel's signal acquired sequentially by the signal acquisition unit 20. In other words, each time a signal for one rotation of each wheel is input sequentially, the gain G j (j=1,2,…,m) are calculated sequentially.

[0056] Here, the maximum order m of the rotational order analysis is not particularly limited and can be an integer of 1 or greater. From the viewpoint of improving the reliability of anomaly detection, it is preferable that m is 10 or greater. In this embodiment, m = 20.

[0057] Referring to Figure 4, in the subsequent step S8, the total gain calculation unit 23 calculates the gain G of each of a predetermined number of rotational order components of the frequency spectrum at each time point. j The sum of these is calculated as the total gain TG at each point in time. As described above, in step S4, "Gain G for rotational orders from the 1st to the mth order (at each point in time)" j The above is stored in RAM 11 or storage device 12. The total gain calculation unit 23 may then calculate the total gain TG (at each point in time) by, for example, performing the following process. That is, the total gain calculation unit 23 first refers to RAM 11 (or storage device 12) and calculates the gain G for rotational orders from the 1st to the mth order (at each point in time). j The unit obtains the "gain G for rotational orders from the 1st to the mth order". The total gain calculation unit 23 then calculates the obtained "gain G for rotational orders from the 1st to the mth order". jFrom among these, the gain G of each of the predetermined multiple rotational order components j Extract the following. The "predetermined multiple rotational orders" may be all of the "rotational orders from the 1st to the mth order" mentioned above, or they may be a part of the "rotational orders from the 1st to the mth order". The extracted rotational order components may be multiple rotational order components, and they may be predetermined rotational order components. The predetermined multiple rotational order components may be, for example, statistically, used to determine the gain G when there is an abnormality in the wheel and when there is no abnormality. j It is desirable to include rotational order components that have been confirmed to exhibit large fluctuations.

[0058] The total gain calculation unit 23 calculates the gain G of each of the extracted "predetermined multiple rotational order components". j The sum of the above is calculated as the total gain TG. The total gain TG is calculated as the gain G of each of the extracted "predetermined rotational order components". j The total gain calculation unit 23 calculates the gain G of each of the extracted predetermined rotational order components. j The total gain TG is calculated as either the "sum", the "sum of absolute values", or the "sum of squares". In step S9, the total gain calculation unit 23 stores (stores) the total gain TG (total gain TG at each point in time) calculated in step S8 in RAM 11 or storage device 12.

[0059] In step S10, the determination unit 24 calculates the rate of increase RGI (increase amount) of the total gain TG per predetermined time PT from the total gain TG at each point in time. As described above, in step S9, the "total gain TG at each point in time" is stored in RAM 11 or storage device 12. Then, the determination unit 24 calculates the rate of increase RGI of the total gain TG per predetermined time PT by executing, for example, the following process. That is, the determination unit 24 first refers to RAM 11 (or storage device 12) to obtain the "total gain TG at the current time (in other words, the most recently stored total gain TG)" and the "total gain TG at a point in time that is a predetermined time PT backward from the current time". Then, the total gain calculation unit 23 may calculate the rate of increase RGI by subtracting the "total gain TG at a point in time that is a predetermined time PT backward from the current time" from the "total gain TG at the current time" and dividing the result by the predetermined time PT. If the predetermined time PT is considered as a unit time, the rate of increase RGI can be understood as the amount of change (increase amount) of the total gain TG in that unit time (predetermined time PT).

[0060] In step S11, the determination unit 24 compares the growth rate RGI calculated in step S10 with the standard growth rate RRI to determine whether there is an abnormality (in this embodiment, an abnormality in the wheel nuts). This determination is performed for each of the wheels FL, FR, RL, and RR. If the growth rate RGI is less than the standard growth rate RRI for all wheels (YES in step S11), the determination unit 24 determines that there is no "wheel nut abnormality" in any of the wheels, and the process proceeds to step S13. If the growth rate RGI is not less than the standard growth rate RRI for any of the wheels (NO in step S11), that is, if the growth rate RGI is greater than or equal to the standard growth rate RRI, the determination unit 24 determines that an "abnormality in the wheel nuts" has occurred in any of the wheels, and the process proceeds to step S12. In step S12, the CPU 9 executes the nut abnormality notification process. Details of the nut abnormality notification process will be described later with reference to Figure 5(A).

[0061] As described above, the determination unit 24 determines that a wheel malfunction has occurred if the increase rate RGI of the total gain TG per predetermined time PT, calculated from the total gain TG at each point in time, is equal to or greater than the standard increase rate RRI. In this embodiment, the determination unit 24 determines that a wheel malfunction has occurred if the increase rate RGI, calculated by "subtracting the total gain TG at a predetermined time PT prior to the current point in time from the total gain TG at the current point in time, and dividing the result by the predetermined time PT", is equal to or greater than the standard increase rate RRI. However, the determination unit 24 may also determine that a wheel malfunction has occurred if, within a predetermined time PT, there are a predetermined number of points in time where "the amount (or rate of increase) of the total gain TG from the previous total gain TG is equal to or greater than a predetermined increase threshold (or predetermined rate of increase threshold)". Furthermore, the determination unit 24 may determine that an abnormality has occurred in the wheel if, within a predetermined time period PT, there are a predetermined number of consecutive times where "the increase (or rate of increase) of the total gain TG from the previous total gain TG is equal to or greater than a predetermined increase threshold (or predetermined rate of increase threshold)." For example, the determination unit 24 determines that an abnormality has occurred in the wheel if the total gain TG calculated at each time point shows an increasing trend (an increasing trend over time). This increasing trend is determined within a predetermined time period PT. This increasing trend may be determined based on "the value obtained by subtracting the total gain TG at a predetermined time period PT prior to the current time from the total gain TG at the current time." This increasing trend may also be determined based on at least one of the number of times within a predetermined time period PT where "the increase (or rate of increase) of the total gain TG from the previous total gain TG is equal to or greater than a predetermined increase threshold (or predetermined rate of increase threshold)," and whether or not these times are consecutive.

[0062] If the determination unit 24 determines in step S11 that there is an abnormality in the wheels (at least one wheel has a growth rate RGI that is equal to or greater than the standard growth rate RRI), it may further identify the wheel where the abnormality occurred (the abnormal wheel). For example, the determination unit 24 may extract the growth rate RGI with the largest value among the total gain TG growth rate RGI per predetermined time PT calculated for each wheel in step S10, and identify the wheel corresponding to the extracted "growth rate RGI with the largest value" as the abnormal wheel. The determination unit 24 may also report the identified abnormal wheel to the notification unit 29.

[0063] In step S13, the fastening time information acquisition unit 25 acquires fastening time information IT indicating the most recent fastening time TMS. For example, the CPU 9, which operates as the fastening time information acquisition unit 25, receives the fastening time information IT from the ECU (for example, the management ECU) via the I / O interface 8.

[0064] In step S14, the determination unit 24 determines whether "the elapsed time since the most recent tightening time TMS indicated by the tightening time information IT is less than or equal to the bearing judgment criterion period RPB, and whether the total gain TG is greater than or equal to the criterion value (bearing judgment criterion value RVB)." That is, in step S14, the determination unit 24 determines whether the total gain TG at the time when the elapsed time since the most recent tightening time TMS is less than or equal to the bearing judgment criterion period RPB is greater than or equal to the bearing judgment criterion value RVB. For example, the determination unit 24 first determines whether "the current elapsed time since the most recent tightening time TMS" is less than or equal to the bearing judgment criterion period RPB. If "the current elapsed time since the most recent tightening time TMS" exceeds the bearing judgment criterion period RPB, the determination unit 24 determines "NO" in step S14, and the process returns to step S1. If the determination unit 24 determines that the "current elapsed time since the most recent tightening time TMS" is less than or equal to the bearing judgment criterion period RPB, in step S14 the determination unit 24 then compares the current total gain TG with the bearing judgment criterion value RVB to determine whether there is an abnormality (in this embodiment, an abnormality in the hub bearing). This determination is performed for each of the wheels FL, FR, RL, and RR. If the total gain TG is less than the bearing judgment criterion value RVB for all wheels (NO in step S14), the determination unit 24 determines that there is no "hub bearing abnormality" in any of the wheels, and the process returns to step S1. If the total gain TG is greater than or equal to the bearing judgment criterion value RVB for any of the wheels (YES in step S14), the determination unit 24 determines that an "abnormality in the hub bearing" has occurred in any of the wheels, and the process proceeds to step S15. In step S15, the CPU 9 executes the bearing abnormality notification process. Details of the bearing abnormality notification process will be described later with reference to Figure 5(B).

[0065] If the determination unit 24 determines in step S14 that there is an abnormality in the wheel (the total gain TG for at least one wheel is equal to or greater than the bearing judgment criterion value RVB), it may further identify the wheel where the abnormality occurred (the abnormal wheel). For example, the determination unit 24 may extract the total gain TG with the largest value among the total gain TG (in particular, the most recently calculated total gain TG) calculated for each wheel in step S8, and identify the wheel corresponding to the extracted "largest total gain TG" as the abnormal wheel. In other words, the determination unit 24 may extract the "current total gain TG" with the largest value among the "current total gain TG" for each wheel, and identify the wheel corresponding to the extracted "largest current total gain TG" as the abnormal wheel. The determination unit 24 may report the identified abnormal wheel to the notification unit 29.

[0066] (Regarding notification processing for nut abnormalities) In step S1210 of Figure 5(A), the map information acquisition unit 26 acquires map information MPI that can identify the position of the vehicle VH at each point in time and the position of the nut repair business SPN located within a predetermined distance from the position of the vehicle VH at each point in time. For example, the CPU 9, which operates as the map information acquisition unit 26, receives the map information MPI from the ECU (for example, an information system ECU) via the I / O interface 8.

[0067] In the following step S1220, the nut information acquisition unit 27 acquires nut information IN, which identifies a wheel nut that can be replaced with the wheel nut that the determination unit 24 has determined to be abnormal. For example, the CPU 9, which operates as the nut information acquisition unit 27, receives the nut information IN from the ECU (for example, a management ECU) via the I / O interface 8.

[0068] In step S1230, the notification unit 29 performs at least one of the following two notifications (first nut abnormality notification and second nut abnormality notification). The first nut abnormality notification is a notification to the occupants of the vehicle VH of the following two matters: that is, the first nut abnormality notification is a notification of the determination result that an abnormality has occurred in the wheel nut, and the location of the nut repair business SPN located within a predetermined distance from the location of the vehicle VH at the time the abnormality was determined to have occurred, as indicated by the map information MPI. The second nut abnormality notification is a notification to the nut repair business SPN located within a predetermined distance from the location of the vehicle VH at the time the abnormality was determined to have occurred, of the following two matters: that is, the second nut abnormality notification is a notification of the determination result that an abnormality has occurred in the wheel nut, and nut information IN identifying a wheel nut that can be replaced with the abnormal wheel nut.

[0069] (Regarding the notification process for bearing malfunctions) In step S1510 of Figure 5(B), the map information acquisition unit 26 acquires map information MPI that can identify the position of the vehicle VH at each point in time and the position of the bearing repair business SPB located within a predetermined distance from the position of the vehicle VH at each point in time. For example, the CPU 9, which operates as the map information acquisition unit 26, receives the map information MPI from the ECU (for example, an information system ECU) via the I / O interface 8.

[0070] In the following step S1520, the bearing information acquisition unit 28 acquires bearing information IB that identifies a hub bearing that can be replaced with the hub bearing that the determination unit 24 has determined to have an abnormality. For example, the CPU 9, which operates as the bearing information acquisition unit 28, receives the bearing information IB from the ECU (for example, the management ECU) via the I / O interface 8.

[0071] In step S1530, the notification unit 29 performs at least one of the following two notifications (first bearing abnormality notification and second bearing abnormality notification). The first bearing abnormality notification is a notification to the occupants of the vehicle VH of the following two matters: namely, the first bearing abnormality notification is a notification of the determination result that an abnormality has occurred in the hub bearing, and the location of the bearing repair business SPB located within a predetermined distance from the location of the vehicle VH at the time the abnormality was determined to have occurred, as indicated by the map information MPI. The second bearing abnormality notification is a notification to the bearing repair business SPB located within a predetermined distance from the location of the vehicle VH at the time the abnormality was determined to have occurred, of the following two matters: namely, the second bearing abnormality notification is a notification of the determination result that an abnormality has occurred in the hub bearing, and the bearing information IB that identifies a hub bearing that can be replaced with the abnormal hub bearing.

[0072] In both the nut abnormality notification process and the bearing abnormality notification process, the notification unit 29 notifies the occupants of the vehicle VH (outputs an alarm) via the display unit 6. At this time, the display unit 6 can distinguish which wheel is experiencing the abnormality and issue an alarm, or it can simply indicate that an abnormality is occurring in any of the wheels. The display unit 6 can also distinguish between a wheel nut abnormality and a hub bearing abnormality and issue an alarm. The alarm may include specific instructions for action regarding the suspected wheel abnormality, such as prompting the driver to inspect the wheel nuts or hub bearings, or prompting the replacement of the tire 7a (wheel nuts or hub bearings).

[0073] Here, the control unit 2 detects an abnormality in the wheel nut based on a comparison between the increase rate RGI of the total gain TG per predetermined time PT and the reference increase rate RRI. When the control unit 2 notifies the occupants of the vehicle VH of the detected abnormality, it is assumed that the occupants of the vehicle VH, etc., will perform the following actions. That is, the occupants of the vehicle VH, a repair shop, etc., will, for example, replace the wheel nut in which the abnormality was detected, and the (replaced) wheel nut will be tightened properly. The control unit 2 then determines that an abnormality has occurred in the hub bearing if the total gain TG remains high during the period from when the wheel nut is replaced until the bearing judgment standard period RPB (for example, one month) has elapsed.

[0074] Therefore, the bearing judgment criterion value RVB for determining whether or not "the total gain TG remains large" may be set based on the total gain TG at the time when the control unit 2 determines that "the increase rate RGI of the total gain TG is equal to or greater than the reference increase rate RRI." Alternatively, the bearing judgment criterion value RVB may be set based on the total gain TG at the time immediately preceding the most recent tightening time TMS. The time immediately preceding the most recent tightening time TMS is the time immediately preceding "the time when the wheel nuts were most recently tightened normally," and is therefore the time before the wheel nuts were replaced, and is considered to be the time when an abnormality occurred in the wheel nuts before replacement. Therefore, by using the bearing judgment criterion value RVB set based on the total gain TG at the time when it is determined that "the increase rate RGI of the total gain TG is equal to or greater than the reference increase rate RRI" (or the time immediately preceding the most recent tightening time TMS), the control unit 2 achieves the following effect. That is, the control unit 2 can precisely detect abnormalities in the hub bearing without falsely detecting "abnormalities in the wheel nuts." However, it is not essential for the control unit 2 that the bearing judgment criterion value RVB be set based on the total gain TG at the time when it is determined that "the increase rate RGI of the total gain TG is equal to or greater than the reference increase rate RRI" (or at the time immediately preceding the most recent tightening time TMS). The bearing judgment criterion value RVB may be a predetermined value, or for example, a predetermined value set for each wheel (for example, a value statistically calculated from the total gain TG at a time when no abnormality has occurred).

[0075] Furthermore, as described above, when the control unit 2 detects an abnormality in the wheel nuts and notifies the occupants of the vehicle VH of the abnormality, it is assumed that the occupants will then properly tighten the wheel nuts (for example, after replacement). Therefore, the control unit 2 may define the most recent tightening time TMS as the point in time when it "most recently detected an abnormality in the wheel nuts." However, the most recent tightening time TMS does not have to be the point in time when it "most recently detected an abnormality in the wheel nuts based on a comparison of the increase rate RGI of the total gain TG with the reference increase rate RRI." Regardless of when it detected the "abnormality in the wheel nuts," the control unit 2 can determine an "abnormality in the hub bearing" based on the total gain TG within the bearing judgment criterion period RPB from the most recent tightening time TMS when the wheel nuts were properly tightened.

[0076] <4. Features> The abnormality detection system 1 (particularly the control unit 2) according to the above embodiment sequentially acquires a signal representing the rotational speed of the wheel as a pulse with a rising edge, and at each point in time calculates a first index representing the temporal variation of the rising edge of each pulse corresponding to one rotation of the wheel. The control unit 2 then performs frequency analysis on the first index at each point in time to calculate the frequency spectrum of the rotational orders from the 1st to the mth order (where m is an integer of 2 or more) of the first index, and calculates the gain G of each predetermined number of rotational order components of the frequency spectrum at each point in time. j The sum of these is calculated as the total gain TG at each point in time. The control unit 2 determines that an abnormality has occurred in the wheel if the increase rate RGI of the total gain TG per predetermined time PT, which is calculated from the total gain TG at each point in time, is equal to or greater than a predetermined standard increase rate RRI.

[0077] The inventors(s) of this invention have discovered that by observing the change in the total gain TG over time at each point in time, it is possible to determine the presence or absence of a wheel abnormality earlier than by comparing the total gain TG itself at each point in time with a predetermined threshold. According to the abnormality detection system 1 of the above embodiment, the presence or absence of an abnormality is determined based on the rate of increase RGI of the total gain TG per predetermined time PT, which is calculated from the total gain TG at each point in time. Therefore, the abnormality detection system 1 (in particular, the control unit 2) can detect abnormalities occurring in the wheel earlier based on a signal representing the rotational speed of the wheel.

[0078] <5. Variation> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention. For example, the following modifications are possible. Furthermore, the gist of the following modifications can be combined as appropriate.

[0079] (1) Although the vehicle VH in the above embodiment was a four-wheeled vehicle, the number of wheels is not particularly limited and may be less than four or five or more. The type of vehicle VH on which the abnormality detection system 1 according to the above embodiment is installed is also not particularly limited and may be a passenger car, commercial vehicle, etc.

[0080] (2) In the above embodiment, the sensor unit 3 was an electromagnetic pickup type sensor unit comprising a gear, a permanent magnet, and a coil. However, the sensor unit 3 is not particularly limited as long as it can detect a physical quantity that changes according to the rotational speed of the wheel. For example, the rotating body 31 may be a permanent magnet in which north poles and south poles are alternately arranged in a ring shape at a predetermined pitch, and the sensor 30 may be a Hall element sensor, an MR (Magneto Resistive) sensor, an MI (Magneto Impedance) sensor, etc., that detects a magnetic field. Alternatively, for example, the sensor unit 3 may be an optical sensor unit that detects light as a physical quantity. In this case, the sensor unit 3 may comprise a light-emitting element, a sensor 30 as a light-receiving element, and a disk-shaped rotating body 31 with slits formed at a predetermined pitch in the circumferential direction.

[0081] (3) In the above embodiment, the signal representing the rotational speed was converted into a pulse with a rising edge by the control unit 2. However, the sensor unit 3 may output a pulse with a rising edge, and the signal acquisition unit 20 of the control unit 2 may acquire this pulse.

[0082] (4) The anomaly detection process in the above embodiment is merely an example and can be modified as appropriate. For example, steps S3 and S6 may be omitted. If step S3 is omitted, the comparison value x i This can be used as the first indicator. [Explanation of symbols]

[0083] 2. Control Unit (Anomaly Detection Device) 20 Signal intensity acquisition unit 21 1st indicator calculation department, 22. Spectrum calculation unit 23 Total Gain Calculation Unit 24 Judgment section 25 Information Acquisition Department at the Time of Agreement 26 Map Information Acquisition Unit 27 Nut Information Acquisition Unit 28 Bearing Information Acquisition Unit 29 Notification Department G j gain IB Bearing Information IN Nut Information IT information at the time of signing MPI Map Information PT (Physical Therapy) - Scheduled Hours RGI growth rate RPB Bearing Judgment Criteria Period (Criteria Period) RRI baseline increase rate RVB Bearing Judgment Criteria (Criteria Value) SPB Bearing Repair Service SPN Nut Repair Service TG Total Gain TMS most recent tightening date VH Vehicle

Claims

1. An abnormality detection device for detecting abnormalities occurring in the wheels, A signal acquisition unit sequentially acquires a signal representing the rotational speed of the wheel as a pulse with a rising edge, A first index calculation unit calculates a first index that represents the temporal variation of the rise time of each pulse corresponding to one rotation of the wheel at each point in time, A spectrum calculation unit calculates the frequency spectrum of the rotation order from the 1st to the mth order (where m is an integer of 2 or more) of the first index at each time point by performing frequency analysis on the first index at each time point. A total gain calculation unit calculates the sum of the gains of a predetermined number of rotational order components of the frequency spectrum at each time point as the total gain at each time point. A determination unit determines that an abnormality has occurred in the wheel if the rate of increase of the total gain per predetermined time, calculated from the total gain at each point in time, is equal to or greater than a predetermined standard rate of increase. Equipped with, Anomaly detection device.

2. The determination unit determines, if the rate of increase is equal to or greater than the standard rate of increase, that there is an abnormality in the wheel, specifically in the wheel nut that attaches the wheel to the hub. A tightening time information acquisition unit acquires tightening time information indicating the most recent tightening time, which is the time when the wheel nut was most recently tightened correctly. Furthermore, The determination unit further determines that if the total gain at a point in time when the elapsed time since the most recent tightening is less than or equal to a predetermined reference period is greater than or equal to a predetermined reference value, then an abnormality has occurred in the hub bearing fixed to the hub which is the center of rotation of the wheel. An anomaly detection device according to claim 1.

3. Map information, The position of the vehicle equipped with the aforementioned wheels at each point in time, The location of a nut repair business capable of repairing the wheel nuts, located within a predetermined distance from the vehicle's position at each point in time, A map information acquisition unit that acquires map information that can identify, A nut information acquisition unit acquires nut information to identify a wheel nut that can be replaced with the wheel nut in question, If the determination unit determines that an abnormality has occurred in the wheel nut, Notification to the occupants of the vehicle of the determination that an abnormality has occurred in the wheel nuts, and the location of the nut repair business, and, Notification to the aforementioned nut repair business of the determination result that an abnormality has occurred in the wheel nut, and the information of the nut. A notification unit that performs at least one of the following, Furthermore, An anomaly detection device according to claim 2.

4. Map information, The position of the vehicle equipped with the aforementioned wheels at each point in time, The location of a bearing repair business capable of repairing the hub bearing, located within a predetermined distance from the vehicle's position at each point in time, A map information acquisition unit that acquires map information that can identify, A bearing information acquisition unit acquires bearing information to identify a hub bearing that can be replaced with the hub bearing in question, If the determination unit determines that an abnormality has occurred in the hub bearing, Notification to the occupants of the vehicle of the determination that an abnormality has occurred in the hub bearing, and the location of the bearing repair business, and, Notification to the bearing repair business operator of the determination result that an abnormality has occurred in the hub bearing, and the bearing information. A notification unit that performs at least one of the following, Furthermore, An anomaly detection device according to claim 2 or 3.

5. An anomaly detection program that detects abnormalities occurring in the wheels, The signal representing the rotational speed of the wheel is sequentially acquired as a pulse with a rising edge, At each point in time, a first index is calculated that represents the temporal variation of the rise time of each pulse corresponding to one rotation of the wheel, By performing frequency analysis on the first index at each time point, the frequency spectra of the rotational orders from the first to the mth order (where m is an integer of 2 or more) of the first index are calculated for each time point. The sum of the gains of a predetermined number of rotational order components of the frequency spectrum at each time point is calculated as the total gain at each time point. If the rate of increase of the total gain per predetermined time, calculated from the total gain at each point in time, is greater than or equal to a predetermined standard rate of increase, it is determined that an abnormality has occurred in the wheel. Make the computer execute it. Anomaly detection program.

6. An anomaly detection method for detecting abnormalities occurring in a wheel, which is performed by a computer, The signal representing the rotational speed of the wheel is sequentially acquired as a pulse with a rising edge, At each point in time, a first index is calculated that represents the temporal variation of the rise time of each pulse corresponding to one rotation of the wheel, By performing frequency analysis on the first index at each time point, the frequency spectra of the rotational orders from the first to the mth order (where m is an integer of 2 or more) of the first index are calculated for each time point. The sum of the gains of a predetermined number of rotational order components of the frequency spectrum at each time point is calculated as the total gain at each time point. If the rate of increase of the total gain per predetermined time, calculated from the total gain at each point in time, is greater than or equal to a predetermined standard rate of increase, it is determined that an abnormality has occurred in the wheel. including, Anomaly detection method.

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