JP7115060B2 - Road surface condition determination device - Google Patents

Description

According to the present invention, a tire-side device detects vibrations received by a tire, creates road surface data indicating the road surface condition based on the vibration data, transmits the road surface data to a vehicle body-side system, and determines the road surface condition based on the road surface data. It relates to a road surface condition determination device.

Conventionally, in Patent Document 1, an acceleration sensor is provided on the back surface of a tire tread, and along with detecting vibration applied to the tire by the acceleration sensor, there is a road surface condition determination method for determining the road surface condition based on the detection result of the vibration. Proposed. In this road surface condition determination method, feature vectors are extracted from the tire vibration waveform detected by the acceleration sensor, and the degree of similarity between the extracted feature vectors and all support vectors stored for each type of road surface is calculated. , determine the road surface condition. For example, using a kernel function, the similarity between the extracted feature vector and all support vectors is calculated, and the type of road surface with the highest degree of similarity, such as dry road, wet road, icy road, snowy road, etc., is currently being driven. road surface condition. With such a road surface state determination method, it is possible to perform road surface determination with high robustness.

JP 2016-107833 A

The inventors of the present invention are studying how to perform two-way communication that enables reliable communication between a tire-side device provided with an acceleration sensor and a vehicle-body-side receiver in a road surface condition determination device.

In the field of communication, when two-way communication is performed, a communication connection is established to form a dedicated communication path between the two parties, and after the connection is established, data to be actually transmitted is communicated. In this case, in order to establish a connection, one device first transmits an advertisement signal, and then the other device that has received the advertisement signal sends a connection request signal to the other device, thereby forming a connection. . By establishing such a connection, communication of a large amount of data becomes possible.

However, in the case of the road surface condition determination device, since the tire side device is provided in the tire and the battery cannot be easily replaced, it is necessary to perform sensing and data communication with limited power. As described above, the form of establishing a connection based on an advertise signal and then transmitting data can reliably communicate a large amount of data, but consumes a large amount of power. In particular, considering the battery life of the tire-side device, it is not preferable to keep the connection open because it consumes a lot of power. power consumption will increase.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a road surface condition determining apparatus capable of accurately determining the road surface condition while reducing power consumption.

In order to achieve the above object, the road surface condition determination device according to claim 1 is arranged in a tire (3) and includes a tire side device (1) that transmits road surface data that is data related to road surface conditions, and a vehicle body side. It has a vehicle body side system (2) that receives road surface data and determines road surface conditions, and the tire side device and the vehicle body side system perform two-way communication. In such a configuration, the tire-side device includes a vibration detection section (10) that outputs a detection signal corresponding to the magnitude of tire vibration, and a waveform processing section (11) that creates road surface data based on the detection signal. and a first data communication section (12) for performing data communication with a vehicle body side system, and the vehicle body side system has a second data communication section (24) for performing data communication with a tire side device. and a road surface determination unit (25) that determines the road surface condition based on the road surface data received by the second data communication unit. Then, the tire side device indicates the result of waveform processing of the detection signal by the waveform processing unit and transmits the road surface data including the waveform processing value corresponding to the road surface state in the advertisement signal, and the vehicle body side system transmits the advertisement signal. The road surface condition is discriminated based on the waveform processing value included in . In addition, if the vehicle body side system cannot determine the road surface condition based on the waveform processing value included in the advertisement signal, it transmits a request signal requesting transmission of detailed data to the tire side device, and the tire side device When receiving a detailed data request signal, it establishes a connection with the vehicle body side system, and after the connection is established, transmits the raw waveform data of the detection signal as the road surface data.

In this way, when the road surface data is transmitted from the tire side device, the road surface condition determination device includes the road surface data including the feature amount, which is a small amount of data, in the advertisement signal, and performs road surface determination based on the feature amount. ing. As a result, road surface determination can be performed without establishing a connection, and power consumption can be reduced by the amount that a connection is not established each time road surface data is transmitted. Therefore, it is possible to provide a road surface condition determination device capable of accurately determining the road surface condition while reducing power consumption.

It should be noted that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and specific components etc. described in the embodiments described later.

1 is a diagram showing a block configuration of a tire device equipped with a tire side device and a vehicle body side system according to the first embodiment when mounted on a vehicle; FIG. FIG. 3 is a block diagram showing details of a receiver of the tire side device and the vehicle body side system; It is a cross-sectional schematic diagram of the tire to which the tire side device was attached. FIG. 4 is an output voltage waveform diagram of the vibration sensor unit during tire rotation; FIG. 10 is a diagram showing how the detection signal of the vibration sensor section is divided for each time window having a predetermined time width T; 4 is a flowchart of tire-side processing executed by a waveform processing section of the tire-side device; 4 is a flowchart of road surface condition determination processing executed by a road surface determination unit of the vehicle body side system; Determinants Xi(r), Xi(s) and distances in each section obtained by dividing the time-axis waveform at the time of the current rotation of the tire and the time-axis waveform at the time of the previous rotation, respectively, by a time window of a predetermined time width T It is the figure which showed the relationship with _yz . 4 is a flowchart of road surface condition determination processing executed by a road surface determination unit of the vehicle body side system;

An embodiment of the present invention will be described below with reference to the drawings. In addition, in each of the following embodiments, portions that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A tire device 100 having a road surface condition determination function according to the present embodiment will be described with reference to FIGS. 1 to 8. FIG. The tire device 100 according to the present embodiment determines the road surface condition during running based on the vibration applied to the ground contact surface of the tire provided for each wheel of the vehicle, and also notifies the vehicle of danger based on the road surface condition. It performs motion control and the like.

As shown in FIGS. 1 and 2, the tire device 100 includes a tire side device 1 provided on the wheel side and a vehicle body side system 2 including various parts provided on the vehicle body side. The vehicle body side system 2 includes a receiver 21, an electronic control unit for brake control (hereinafter referred to as brake ECU) 22, an alarm device 23, and the like. A portion of the tire device 100 that realizes a road surface condition determination function corresponds to a road surface condition determination device. In the case of this embodiment, the receiver 21 of the tire side device 1 and the vehicle body side system 2 constitutes a road surface condition determination device.

In the tire device 100 of the present embodiment, the tire device 1 transmits data corresponding to the road surface condition on which the tire 3 is running (hereinafter referred to as road surface data), and the receiver 21 receives the road surface data to determine the road surface condition. to determine. Further, the tire device 100 notifies the notification device 23 of the determination result of the road surface condition by the receiver 21, and causes the notification device 23 to notify the determination result of the road surface condition. This makes it possible to notify the driver of the road surface condition, such as whether the road is dry, wet, or icy, and to warn the driver if the road is slippery. In addition, the tire device 100 transmits the road surface condition to the brake ECU 22 or the like that controls the vehicle motion, so that the vehicle motion control for avoiding danger is performed. For example, when the road is icy, the braking force generated relative to the amount of brake operation is weakened compared to when the road is dry, so that the vehicle motion control is adapted to the low road surface μ. . Specifically, the tire-side device 1 and the receiver 21 are configured as follows.

As shown in FIG. 2, the tire side device 1 includes a vibration sensor section 10, a waveform processing section 11, a data communication section 12, and a power supply section 13. As shown in FIG. 31 is provided on the back side.

The vibration sensor section 10 constitutes a vibration detection section for detecting vibration applied to the tire 3 . For example, the vibration sensor section 10 is configured by an acceleration sensor. When the vibration sensor unit 10 is an acceleration sensor, the vibration sensor unit 10 is in contact with the circular orbit drawn by the tire side device 1 when the tire 3 rotates, that is, in the direction indicated by the arrow X in FIG. An acceleration detection signal is output as a detection signal corresponding to the magnitude of vibration in the tangential direction. More specifically, the vibration sensor unit 10 generates, as a detection signal, an output voltage that is positive in one of the two directions indicated by the arrow X and negative in the opposite direction. For example, the vibration sensor unit 10 detects acceleration at each predetermined sampling period set to a period shorter than one rotation of the tire 3, and outputs it as a detection signal. The detection signal of the vibration sensor unit 10 is expressed as an output voltage or an output current, but here, the case where it is expressed as an output voltage is taken as an example.

The waveform processing unit 11 is composed of a well-known microcomputer having a CPU, ROM, RAM, I/O, etc., performs signal processing of the detection signal according to a program stored in the ROM, etc., and calculates the road surface state appearing in the detection signal. Generate the road surface data shown. The road surface data includes data including the feature amount of tire vibration and data including the raw waveform of the detection signal in addition to the feature amount.

Specifically, the waveform processing unit 11 uses the detection signal output by the vibration sensor unit 10 as a detection signal representing vibration data in the tire tangential direction, and performs waveform processing on the vibration waveform indicated by this detection signal. Extract feature values of tire vibration. In the case of this embodiment, the characteristic amount of the tire G is extracted by signal processing the detection signal of the acceleration of the tire 3 (hereinafter referred to as tire G). In addition, the waveform processing unit 11 acquires a raw waveform that is the detection signal itself of the vibration sensor unit 10, performs signal processing such as noise removal as necessary, and converts it into data (hereinafter referred to as raw waveform data conversion). The resulting data is called raw waveform data). Then, the waveform processing unit 11 transmits the data including the extracted feature amount or the raw waveform data to the data communication unit 12 as road surface data. In this case, the road surface data including the raw waveform data also includes the data indicating the feature amount, but it is also possible to adopt a form in which the data indicating the feature amount is not included. In addition, the detail of a feature-value here is demonstrated later.

Further, the waveform processing unit 11 controls data transmission from the data communication unit 12, and transmits the road surface data to the data communication unit 12 at the desired timing for data transmission, so that the data is transmitted from the data communication unit 12. Allow communication to take place. For example, the waveform processing unit 11 extracts the characteristic amount of the tire G each time the tire 3 rotates once, and the data communication unit 12 extracts the characteristic amount once or more once or more each time the tire 3 rotates once or more. The road surface data is transmitted to For example, the waveform processing unit 11 transmits to the data communication unit 12 the road surface data including the characteristic amount of the tire G extracted during one revolution of the tire 3 when transmitting the road surface data to the data communication unit 12. ing. Further, when the waveform processing unit 11 receives a detailed data request signal from the vehicle body side system 2, the waveform processing unit 11 includes the raw waveform data in addition to the characteristic amount of the tire G extracted during one rotation of the tire 3 at that time. The road surface data is transmitted to the data communication unit 12 .

The data communication unit 12 is a part that constitutes the first data communication unit, and performs data communication with a data communication unit 24 (described later) of the receiver 21 in the vehicle body side system 2 . For example, when the road surface data is transmitted from the waveform processing unit 11, the data communication unit 12 transmits the road surface data at that timing. The timing of data transmission from the data communication unit 12 is controlled by the waveform processing unit 11, and each time road surface data is sent from the waveform processing unit 11 each time the tire 3 makes one or more rotations, the data communication unit Data transmission from 12 is performed.

In addition, the data communication section 12 is configured to perform two-way communication with the data communication section 24 . Although the data communication unit 12 is described here as one configuration, the transmission unit and the reception unit may be configured separately. Various forms of two-way communication can be applied, including Bluetooth communication including BLE (abbreviation of Bluetooth Low Energy) communication, wireless LAN (abbreviation of Local Area Network) such as wifi, Sub-GHz communication, ultra Wideband communication, ZigBee, etc. can be applied. "Bluetooth" is a registered trademark.

As described above, in the field of communication, when two-way communication is performed, a communication connection is constructed to form a dedicated communication path between the two. Communication takes place.

However, in this embodiment, the method of two-way communication differs depending on whether the amount of data sent from the tire side device 1 to the vehicle body side system 2 is large or small. Specifically, "road surface data including feature amounts" that does not include raw waveform data is "small amount of data" with a relatively small amount of data, and "raw waveform data is included" regardless of whether feature amounts are included "Road surface data" is "mass data" with a larger amount of data than that. In the case of this embodiment, two-way communication is performed between "road surface data including feature amounts", which is "small amount of data", and "road surface data including raw waveform data in addition to feature amounts", which is "large amount of data". changing the form of That is, in the former, data communication is performed without building a connection, and in the latter, data communication is performed after building a connection.

When building a connection, the tire side device 1 first transmits an advertising signal, and then the vehicle body side system 2 that has received the advertising signal transmits a connection request signal to the tire side device 1 . By establishing such a connection, communication of a large amount of data becomes possible. This is because, for large amounts of data, it is not possible to transmit all packets of the desired amount of data in one transmission. For large amounts of data, a predetermined amount of data per packet is transmitted with a certain transmission interval such as 7.5 μsec, and all data transmission is completed by repeating multiple transmissions. . Such data communication cannot be performed unless a connection is established.

Here, the advertise signal is a keyword signal used when building a connection in two-way communication. It becomes a signal requesting establishment of a connection. In this embodiment, the tire side device 1 corresponds to a peripheral side device, and the vehicle body side system 2 corresponds to a central side device. is constructed. The frequency and number of transmissions of the advertising signal are determined by specifications, regulations, etc. For example, when BLT communication is applied as two-way communication, the advertising signal is a signal in the frequency band of 2.5 GHz. Since the advertisement signal is a signal that is repeatedly transmitted in a short period, it can contain only a small amount of data, and cannot contain a large amount of data.

For this reason, "road surface data including raw waveform data in addition to the feature amount", which is "a large amount of data", cannot be included in the advertisement signal, but "road surface data including a feature amount", which is "a small amount of data" is included in the advertising signal. Therefore, in this embodiment, the "road surface data including the feature amount" is included in the advertising signal and transmitted, and only when "road surface data including raw waveform data in addition to the feature amount" is required as detailed data. , a connection is established before data communication is performed.

The power supply unit 13 serves as a power supply for the tire-side device 1, and supplies power to each unit provided in the tire-side device 1 to operate each unit. The power supply unit 13 is composed of a battery such as a button battery. Since the tire-side device 1 is provided inside the tire 3, the battery cannot be easily replaced, so it is necessary to reduce power consumption. In addition to the battery, the power supply unit 13 can also be configured by a power generation device, a storage battery, or the like. When the power supply unit 13 is configured to have a power generator, the problem of battery life is reduced compared to the case of using a battery, but since it is difficult to generate a large amount of power, the problem of reducing power consumption is the battery. is the same as

On the other hand, the receiver 21, the brake ECU 22, and the notification device 23, which constitute the vehicle body side system 2, are driven when a start switch such as an ignition switch (not shown) is turned on.

As shown in FIG. 2, the receiver 21 has a data communication section 24 and a road surface determination section 25.

The data communication unit 24 is a part that constitutes the second data communication unit, and includes raw waveform data in addition to the road surface data including the feature amount transmitted from the data communication unit 12 of the tire side device 1 and the feature amount. It plays a role of receiving road surface data and transmitting it to the road surface determination unit 25 .

The road surface determination unit 25 is configured by a well-known microcomputer having a CPU, ROM, RAM, I/O, etc., and performs various processes according to programs stored in the ROM to determine the road surface condition. Specifically, the road surface determination unit 25 stores support vectors, and determines the road surface state by comparing the road surface data transmitted from the waveform processing unit 11 with the support vectors.

Support vectors are stored and saved for each type of road surface. A support vector is a feature quantity that serves as a model, and is obtained, for example, by learning using a support vector machine. A vehicle equipped with the tire-side device 1 is experimentally driven for each type of road surface, and the feature values extracted by the waveform processing unit 11 at that time are learned for a predetermined number of tire revolutions, and a typical feature value is selected from among the feature values. Support vectors are obtained by extracting a predetermined number. For example, feature amounts for 1 million rotations are learned for each type of road surface, and a typical feature amount for 100 rotations is extracted from the learned feature amounts as support vectors.

Then, the road surface determination unit 25 determines the road surface condition by comparing the feature amount sent from the tire side device 1 received by the data communication unit 24 and the stored support vector for each type of road surface. . For example, the feature amount included in the road surface data received this time is compared with support vectors for each type of road surface, and the road surface with the support vector having the closest feature amount is determined as the current road surface.

After determining the road surface condition, the road surface determination unit 25 notifies the determined road surface condition to the notification device 23, and if necessary, notifies the driver of the road surface condition from the notification device 23. As a result, the driver will try to drive according to the road surface condition, and it will be possible to avoid the danger of the vehicle. For example, the road surface condition determined through the notification device 23 may be always displayed, or the road surface may be displayed only when it is necessary to drive more carefully, such as when the determined road surface condition is wet or icy. The state may be displayed to warn the driver. Further, the road surface condition is transmitted from the receiver 21 to an ECU such as the brake ECU 22 for executing vehicle motion control, and the vehicle motion control is executed based on the transmitted road surface condition.

The brake ECU 22 constitutes a brake control device that performs various brake controls. Specifically, the brake ECU 22 controls the braking force by increasing or decreasing the wheel cylinder pressure by driving an actuator for brake fluid pressure control. The brake ECU 22 can also independently control the braking force of each wheel. When the road surface condition is transmitted from the receiver 21, the brake ECU 22 controls braking force as vehicle motion control based on the information. For example, the brake ECU 22 weakens the braking force generated with respect to the amount of brake operation by the driver, compared to the dry road surface, when the road surface condition conveyed indicates that the road surface is icy. As a result, it is possible to suppress the wheel slip and avoid the danger of the vehicle.

The notification device 23 is composed of, for example, a meter display, and is used to notify the driver of the road surface condition. When the notification device 23 is configured by a meter display, it is arranged in a place where the driver can visually recognize it while driving the vehicle, for example, it is installed in the instrument panel of the vehicle. When the road surface condition is transmitted from the receiver 21, the meter display can visually inform the driver of the road surface condition by displaying the road surface condition in such a manner that the road surface condition can be grasped.

Note that the notification device 23 can also be configured with a buzzer, a voice guidance device, or the like. In this case, the notification device 23 can audibly notify the driver of the road surface condition by a buzzer sound or voice guidance. In addition, although the meter display device is exemplified as the notification device 23 that performs visual notification, the notification device 23 may be configured by a display device that displays information such as a head-up display.

Thus, the tire device 100 according to this embodiment is configured. Each part constituting the vehicle body side system 2 is connected through an in-vehicle LAN (abbreviation of Local Area Network) by CAN (abbreviation of Controller Area Network) communication, for example. Therefore, each part can transmit information to each other through the in-vehicle LAN.

The tire device 100 according to this embodiment is configured as described above. Next, details of the feature amount extracted by the waveform processing unit 11 described above will be described.

The feature amount referred to here is an amount indicating the feature of the vibration applied to the tire 3 acquired by the vibration sensor unit 10, and is represented as a feature vector, for example.

The output voltage waveform of the detection signal of the vibration sensor unit 10 when the tire rotates is, for example, the waveform shown in FIG. As shown in this figure, when the portion of the tread 31 corresponding to the location where the vibration sensor section 10 is arranged in the tread 31 begins to contact the ground as the tire 3 rotates, the output voltage of the vibration sensor section 10 reaches its maximum value. Take. Hereinafter, the peak value at the start of grounding at which the output voltage of the vibration sensor section 10 takes the maximum value will be referred to as the first peak value. Further, as shown in FIG. 4, as the tire 3 rotates, the portion of the tread 31 that corresponds to the location where the vibration sensor unit 10 is arranged stops contacting the ground. takes a local minimum value. Hereinafter, the peak value at the time when the output voltage of the vibration sensor section 10 takes a minimum value and the grounding is terminated is referred to as a second peak value.

The reason why the output voltage of the vibration sensor unit 10 takes the peak value at the above timing is as follows. That is, when the portion of the tread 31 that corresponds to the location where the vibration sensor section 10 is disposed in the tread 31 is brought into contact with the ground as the tire 3 rotates, the portion of the tire 3 that had been a substantially cylindrical surface until then in the vicinity of the vibration sensor section 10 becomes It is pressed and deformed into a flat shape. By receiving this impact, the output voltage of the vibration sensor section 10 takes the first peak value. Further, when the portion of the tread 31 corresponding to the location where the vibration sensor section 10 is arranged in the tread 31 moves away from the ground contact surface as the tire 3 rotates, the tire 3 is released from pressure in the vicinity of the vibration sensor section 10 and becomes flat. returns to a substantially cylindrical shape. The output voltage of the vibration sensor section 10 takes the second peak value by receiving the shock when the shape of the tire 3 returns to its original shape. In this manner, the output voltage of the vibration sensor section 10 takes the first and second peak values at the start and end of grounding, respectively. Further, since the direction of the impact when the tire 3 is pressed is opposite to the direction of the impact when the tire 3 is released from the pressure, the sign of the output voltage is also opposite.

Here, the moment when the portion of the tire tread 31 corresponding to the location where the vibration sensor unit 10 is placed touches the road surface is defined as a "stepping area", and the moment when it leaves the road surface is defined as a "kicking area". The "stepping region" includes the timing of the first peak value, and the "kicking region" includes the timing of the second peak value. In addition, the area in front of the stepping-on area is referred to as the "pre-treading area", and the area from the stepping-on area to the kicking-out area, that is, the area in which the portion of the tire tread 31 corresponding to the location where the vibration sensor unit 10 is arranged is grounded, is the "before-kicking area". area", and the area after the kicking-out area is called the "after-kicking area". In this manner, the period in which the portion of the tire tread 31 corresponding to the location where the vibration sensor section 10 is placed is grounded, and the period before and after that can be divided into five areas. Note that in FIG. 4, the "pre-stepping region", "stepping-in region", "pre-kicking region", "kicking region", and "post-kicking region" of the detection signal are divided into five regions R1 to R5 in this order. is shown as

Depending on the road surface condition, the vibration generated in the tire 3 varies in each of the partitioned regions, and the detection signal of the vibration sensor unit 10 changes. , to detect the road surface condition on which the vehicle is traveling. For example, in slippery road conditions such as compacted snow, the shear force at the time of kicking off decreases, so the band value selected from the 1 kHz to 4 kHz band decreases in the kicking region R4 and the post-kicking region R5. In this way, since each frequency component of the detection signal of the vibration sensor section 10 changes according to the road surface condition, it is possible to determine the road surface condition based on the frequency analysis of the detection signal.

Therefore, the waveform processing unit 11 converts the detection signal of the vibration sensor unit 10 for one rotation of the tire 3, which is a continuous time-axis waveform, into each time window of a predetermined time width T as shown in FIG. A feature amount is extracted by dividing into a plurality of sections and performing frequency analysis on each section. Specifically, by performing frequency analysis in each section, a power spectrum value in each frequency band, that is, a vibration level in a specific frequency band is obtained, and this power spectrum value is used as a feature amount.

Note that the number of sections divided by the time window of time width T is a value that varies according to the vehicle speed, more specifically, the rotational speed of the tire 3 . In the following description, the number of sections for one tire rotation is n (where n is a natural number).

For example, the power obtained by passing the detection signal of each section through a plurality of specific frequency band filters, for example, five bandpass filters of 0 to 1 kHz, 1 to 2 kHz, 2 to 3 kHz, 3 to 4 kHz, and 4 to 5 kHz A spectral value is used as a feature quantity. This feature quantity is called a feature vector, and the feature vector Xi of a certain section i (where i is a natural number of 1 ≤ i ≤ n) is the power spectrum value a _ik of each specific frequency band. is expressed as the following formula as a matrix whose elements are:

なお、パワースペクトル値ａ_ｉｋにおけるｋは、特定周波数帯域の数、つまりバンドパスフィルタの数であり、上記のように０～５ｋＨｚの帯域を５つに分ける場合、ｋ＝１～５となる。そして、全区画１～ｎの特徴ベクトルＸ１～Ｘｎを総括して示した行列式Ｘは、次式となる。

Note that k in the power spectrum value a _ik is the number of specific frequency bands, that is, the number of bandpass filters. A determinant X summarizing the feature vectors X1 to Xn of all the sections 1 to n is given by the following equation.

この行列式Ｘがタイヤ１回転分の特徴量を表した式となる。波形処理部１１では、この行列式Ｘで表される特徴量を振動センサ部１０の検出信号を周波数解析することによって抽出している。

This determinant X becomes an expression representing the feature amount for one rotation of the tire. The waveform processing unit 11 extracts the feature quantity represented by the determinant X by frequency-analyzing the detection signal of the vibration sensor unit 10 .

Next, the operation of the tire device 100 according to this embodiment will be described with reference to FIGS. 6 and 7. FIG. Here, an example will be described in which the road surface condition can be determined without detailed data, that is, the raw waveform data, but later detailed data is required to determine the road surface condition.

First, in the tire side device 1 for each wheel, the waveform processing section 11 executes the tire side processing shown in FIG. This process is executed in each predetermined control cycle.

First, in step S100, input processing of the detection signal of the vibration sensor section 10 is performed. This process is continued until the tire 3 rotates once in step S105. After inputting the detection signal of the vibration sensor unit 10 for one rotation of the tire, the process proceeds to step S110 to extract the feature amount of the time-axis waveform of the input detection signal of the vibration sensor unit 10 for one rotation of the tire.

It should be noted that whether or not the tire 3 has made one revolution is determined based on the time-axis waveform of the detection signal from the vibration sensor section 10 . That is, since the detection signal draws the time domain waveform shown in FIG. 4, one rotation of the tire 3 can be grasped by confirming the first peak value and the second peak value of the detection signal.

Moreover, the road surface condition particularly appears as a change in the time-axis waveform of the detection signal in the periods before and after the "push-in area", "pre-kicking area", and "kicking area". Therefore, it is sufficient that the data during this period is input, and it is not necessary to input all the data of the detection signals of the vibration sensor unit 10 during one rotation of the tire. For example, for the "pre-tread region" and "post-kick region," it is sufficient to have data in the vicinity of the "tread-in region" and the "kick-out region." For this reason, the region in which the vibration level of the detection signal of the vibration sensor unit 10 is smaller than a predetermined threshold is defined as a period that is less likely to be affected by road surface conditions, even in the "region before stepping on" and the "region after kicking out." , the detection signal may not be input.

Also, the extraction of the feature quantity performed in step S110 is performed by the method as described above.

Then, in step S115, it is determined whether or not there is a request for detailed data. This determination is affirmative when a detailed data request signal has been transmitted from the vehicle body side system 2 in step S250 of FIG. 7, which will be described later. Here, since the detailed data request signal has not yet been transmitted, the process proceeds to step S120 to transmit the road surface data including the feature amount extracted during the current control cycle to the data communication unit 12 . As a result, the road surface data including the feature amount is included in the advertisement signal and transmitted from the data communication unit 12 in a state in which no connection is established. Note that the advertising signal at this time corresponds to the first advertising signal.

On the other hand, in the receiver 21, the road surface determination section 25 performs the road surface state determination process shown in FIG. This process is executed in each predetermined control cycle.

First, in step S200, data reception processing is performed. This processing is performed by the road surface determination unit 25 fetching the road surface data when the data communication unit 24 receives the road surface data. When the data communication section 24 is not receiving data, the road surface determination section 25 ends this processing without taking in any road surface data.

After that, the process proceeds to step S210 to determine whether or not data has been received. If the data has been received, the process proceeds to step S220. If the data has not been received, the processes of steps S200 and S210 are repeated until the data is received.

Then, the process proceeds to step S220 to determine the road surface condition. The road surface condition is determined by comparing the feature amount included in the received road surface data with the support vector for each road surface type stored in the road surface determination unit 25 . For example, the similarity between the feature quantity and all support vectors for each type of road surface is obtained, and the road surface of the support vector with the highest similarity is determined as the current road surface.

For example, the similarity between the feature quantity and all support vectors for each type of road surface can be calculated by the following method.

Regarding the determinant X representing the feature quantity as described above, let the determinant of the feature quantity be X(r), the determinant of the support vector be X(s), and the power spectrum value a _ik be denoted by a(r) _ik , a(s) _ik . In that case, the determinant X(r) of the feature amount and the determinant X(s) of the support vector are expressed as follows.

類似度は、２つの行列式で示される特徴量とサポートベクタとの似ている度合いを示しており、類似度が高いほどより似ていることを意味している。本実施形態の場合、路面判別部２５は、カーネル法を用いて類似度を求め、その類似度に基づいて路面状態の判定を行う。ここでは、特徴量の行列式Ｘ（ｒ）とサポートベクタの行列式Ｘ（ｓ）の内積、換言すれば特徴空間内において所定の時間幅Ｔの時間窓毎で分割した区画同士の特徴ベクトルＸｉが示す座標間の距離を算出し、それを類似度として用いている。

The degree of similarity indicates the degree of similarity between the feature quantity and the support vectors indicated by the two determinants, and the higher the degree of similarity, the more similar they are. In the case of this embodiment, the road surface determination unit 25 obtains the degree of similarity using the kernel method, and determines the road surface state based on the degree of similarity. Here, the inner product of the determinant X(r) of the feature quantity and the determinant X(s) of the support vector, in other words, the feature vector Xi The distance between the coordinates indicated by is calculated and used as the degree of similarity.

For example, as shown in FIG. 8, with respect to the time-axis waveform of the detection signal of the vibration sensor unit 10, the time-axis waveform during the current rotation of the tire 3 and the time-axis waveform of the support vector are each captured in a time window of a predetermined time width T. to divide into each partition. In the illustrated example, since each time-axis waveform is divided into five sections, n=5 and i is represented by 1≤i≤5. Here, as shown in the figure, let Xi(r) be the feature vector Xi of each section during the current rotation of the tire 3, and Xi(s) be the feature vector of each section of the support vector. In that case, for the distance _Kyz between the coordinates indicated by the feature vector Xi of each section, the horizontal cell containing the feature vector Xi(r) of each section during the current rotation of the tire 3 and the feature of each section of the support vector It is shown as a square intersecting with the vertical square containing the vector Xi(s). In the distance _Kyz , y is the rewritten i in Xi(s), and z is the rewritten i in Xi(r). In practice, the number of sections during the current rotation of the tire 3 and the number of support vectors may differ depending on the vehicle speed.

In the case of the present embodiment, feature vectors are obtained by dividing into five specific frequency bands. Therefore, the feature vector Xi of each section is represented in a six-dimensional space including the time axis, and the distance between the coordinates indicated by the feature vectors Xi of the sections is the distance between the coordinates in the six-dimensional space. However, the distance between the coordinates indicated by the feature vectors of each block is smaller when the feature quantity and the support vector are similar, and larger when they are dissimilar. A larger value indicates a lower degree of similarity.

For example, when sections 1 to n are defined by time division, the distance K _yz between the coordinates indicated by the feature vectors of section 1 is given by the following equation.

このようにして、時分割による区画同士の特徴ベクトルが示す座標間の距離Ｋ_ｙｚを全区画について求め、全区画分の距離Ｋ_ｙｚの総和Ｋ_{ｔｏｔａｌ}を演算し、この総和Ｋ_{ｔｏｔａｌ}を類似度に対応する値として用いている。そして、総和Ｋ_{ｔｏｔａｌ}を所定の閾値Ｔｈと比較し、総和Ｋ_{ｔｏｔａｌ}が閾値Ｔｈよりも大きければ類似度が低く、総和Ｋ_{ｔｏｔａｌ}が閾値Ｔｈよりも小さければ類似度が高いと判定する。そして、このような類似度の算出を全サポートベクタに対して行い、最も類似度が高かったサポートベクタと対応する路面の種類が現在走行中の路面状態であると判別する。このようにして、路面状態判別を行うことができる。

In this way, the distance K _yz between the coordinates indicated by the feature vectors of the partitions by time division is obtained for all partitions, the _total sum K _yz of the distances K yz for all partitions is calculated, and this total K _total is used as the similarity are used as corresponding values. Then, the total K _total is compared with a predetermined threshold Th, and if the total K _total is greater than the threshold Th, the similarity is determined to be low, and if the total K _total is less than the threshold Th, the similarity is determined to be high. Then, such similarity calculation is performed for all support vectors, and the type of road surface corresponding to the support vector with the highest similarity is determined to be the road surface condition on which the vehicle is currently running. In this manner, road surface condition determination can be performed.

Although the sum K _total of the distances K _yz between the two coordinates indicated by the feature vectors of each section is used here as the value corresponding to the degree of similarity, other parameters can also be used as the parameter indicating the degree of similarity. . For example, an average distance K _ave that is an average value of distances K _yz obtained by dividing the total sum K _total by the number of sections can be used as a parameter indicating the degree of similarity. Also, as disclosed in Patent Document 1, similarity can be calculated using various kernel functions. Further, instead of using all of the feature vectors, the similarity calculation may be performed by excluding paths having a low degree of similarity among them.

However, there may be cases where the road surface condition determination cannot be accurately performed, for example, when there are multiple candidates that are considered to be similar due to high similarity between support vectors on multiple road surfaces. In such a case, it is preferable to request detailed data and perform more detailed road surface condition determination. Therefore, in the following step S230, it is determined whether detailed data is required.

Then, if the road surface condition has not been accurately determined in step S220, a positive determination is made in step S230, and if the road surface condition has been accurately determined, a negative determination is made in step S230. The road surface condition determination described above is performed based on the feature amount in the road surface data sent from the tire side device 1 for each wheel. Therefore, the road surface conditions of the road surface on which the tire 3 on which the four tire-side devices 1 are arranged are determined. Here, even one of the four tire-side devices 1 detects the road surface condition based on the feature amount in the road surface data sent from the tire-side device 1 when the road surface condition cannot be accurately determined. It is assumed that the state could not be determined.

However, this is only an example, and another form may be applied as a case where road surface condition determination cannot be accurately performed. For example, when the road surface condition cannot be determined based on the feature amounts in the road surface data for all four tire-side devices 1, or when the tire-side devices 1 for both right wheels or both left wheels have the feature values in the road surface data. For example, the road surface condition could not be determined based on

Here, first, assuming that the road surface condition can be accurately determined without detailed data, the process proceeds to step S240. Step S240 is a process performed when a connection, which will be described later, has been established. If the connection has been established, a disconnection request signal for disconnecting it is transmitted, and the processing is terminated. If the connection has not been established, the processing is terminated. As a result, connections can be formed as needed, and power consumption can be reduced. In other words, if the connection is established all the time, detailed data can be communicated all the time. will lead to a decrease in battery life. Therefore, by disconnecting the connection when it is not necessary to maintain the connection and establishing the connection when necessary, it is possible to reduce power consumption and improve battery life. It becomes possible.

On the other hand, if the road surface condition could not be properly determined in step S230, the process proceeds to step S250 to transmit a detailed data request signal. In this case, the detailed data request signal may be sent to all of the plurality of tire side devices 1, but at least the detailed data request signal is sent to the tire side device 1 that could not accurately determine the road surface condition. you should do it. For this reason, ID information of the tire-side device 1 requesting transmission of detailed data is stored and a request signal is transmitted. As a result, power consumption can be reduced because information needs to be sent only to the tire-side device 1 that needs it. Note that the ID information of each tire device 1 can be recognized by the vehicle body system 2 by, for example, storing the ID included in the data transmitted from the tire device 1 by the receiver 21. It is possible to include identification information in the signal.

Here, when a detailed data request signal is transmitted from the vehicle body side system 2 to the tire side device 1, an affirmative determination is made in step S115 in the tire side processing of FIG. If an affirmative determination is made in step S115, the process proceeds to step S125, and the waveform processing unit 11 determines whether or not connection is in progress. If the detailed data request signal has just been received, the connection is not yet established, so the process proceeds to step S130. Also, if the connection is established based on the process described later, the process proceeds to step S150.

In step S130, the waveform processing unit 11 transmits an advertise signal in order to establish a connection. The advertising signal at this time corresponds to the second advertising signal, and may be any signal that requires transmission of a connection request signal, which will be described later, from the vehicle body side system 2 in order to establish a connection. It does not matter if the road surface data is included. After that, the process proceeds to step S135, and the waveform processing unit 11 enters a reception standby state so as to be able to receive a later-described connection request signal to be sent from the vehicle body side system 2 later.

Further, in the road surface state determination process of FIG. 7, it is determined in step S260 whether or not an advertising signal has been received, and this process is repeated until an advertising signal is received. For example, scanning for reading data transmitted from the tire-side device 1 is performed for each predetermined scanning cycle, and whether or not an advertising signal has been received is determined for each scanning cycle. Here, when the advertisement signal is transmitted from the tire-side device 1 as described above, an affirmative determination is made in step S260, and the process proceeds to step S270 to transmit the connection request signal.

Then, as described above, when the connection request signal is transmitted from the receiver 21, an affirmative determination is made in step S140 of the tire side processing in FIG. As a result, a dedicated communication path is formed between each tire-side device 1 and the receiver 21, and even large-capacity data can be communicated. Therefore, the process proceeds to step S150 to transmit the road surface data including the raw waveform data in addition to the characteristic amount to the vehicle body side system 2. FIG.

In this way, when the road surface data including the raw waveform data in addition to the feature amount is transmitted to the receiver 21, when the processing of steps S200 to S220 of the road surface state determination processing in FIG. The road surface condition is determined based on the detailed data. It should be noted that various publicly known methods can be applied as the road surface condition determination method using the raw waveform data. For example, in the receiver 21, the feature amount as described above is again extracted and the degree of similarity with the support vector is calculated to determine the road surface state, or the integrated value of the output voltage in the predetermined frequency band in the raw waveform data The road surface condition can be determined based on the size of .

When the road surface condition can be accurately determined in step S220, the road surface determination unit 25 proceeds to step S240 and transmits a disconnection request signal. Based on this, the waveform processing unit 11 determines that the disconnection request signal has been received in step S155 of the tire side processing in FIG. 6, proceeds to step S160, disconnects the connection, and ends the processing. Also, the connection is maintained until the disconnection request signal is received, and the transmission of the road surface data including the characteristic amount and the raw waveform data is continued.

As described above, the tire device 100 according to the present embodiment can determine the road surface condition of the road surface on which the vehicle is traveling. When the road surface data is transmitted from the tire-side device 1, the road surface data including the feature amount, which is a small amount of data, is included in the advertising signal when the road surface state is determined as described above, and the road surface is determined based on the feature amount. It is carried out. As a result, road surface determination can be performed without establishing a connection, and power consumption can be reduced by the amount that a connection is not established each time road surface data is transmitted.

Therefore, the tire device 100 including the road surface condition determination device capable of accurately determining the road surface condition while reducing power consumption can be provided.

Further, when the road surface condition cannot be determined accurately with the feature quantity included in the road surface data sent in the advertisement signal, the vehicle body system 2 sends a detailed data request signal to the tire device 1. is doing. As a result, a connection is established between the tire side device 1 and the vehicle body side system 2, and road surface data including raw waveform data, which is a large amount of data, is sent from the tire side device 1 to the vehicle body side system 2, and the raw waveform data is sent to the vehicle body side system 2. The determination of the road surface condition is performed based on. Therefore, even if the road surface condition cannot be determined based on the feature amount sent as the advertising signal, the road surface condition can be accurately determined based on the raw waveform data.

(Second embodiment)
A second embodiment will be described. This embodiment differs from the first embodiment in the method of establishing a connection, and is otherwise the same as the first embodiment. Therefore, only the differences from the first embodiment will be described.

In the first embodiment, when the vehicle body side system 2 requests detailed data when detailed data is required, the tire side device 1 transmits an advertisement signal, and when the vehicle body side system 2 receives the advertisement signal, a connection request is made. A signal is being sent. In other words, the system 2 on the vehicle body requests the device 1 on the tire side to establish a connection.

Alternatively, the tire device 1 may request the vehicle body system 2 to establish a connection. Specifically, the road surface condition determination process shown in FIG. 9 is executed by the road surface determination unit 25 . Note that the processing shown in FIG. 9 is executed instead of the processing shown in FIG. 7 described in the first embodiment. In this embodiment, substantially the same processing as the processing shown in FIG. 6 described in the first embodiment is executed, and part of the processing shown in FIG. 9 is common to that in FIG. , the description of the common parts is omitted.

Also in this embodiment, the tire side device 1 executes the processing shown in FIG. 6 as in the first embodiment, and the road surface determination section 25 executes the processing shown in FIG. Then, in step S250 of FIG. 9, when the detailed data request signal is transmitted, as shown in step S130 of FIG. . At this time, the advertisement signal includes a connection request signal requesting establishment of a connection. Then, when the vehicle body side system 2 receives the advertisement signal including the connection request signal in step S280 in FIG. 9, instead of transmitting the connection request signal in step S270 in FIG. The process of S290 is executed. That is, a connection is established by transmitting a connection response signal for establishing a connection in step S285, and a connection completion signal indicating completion of connection establishment is transmitted to the tire side device 1 in step S290. As a result, the tire-side device 1 can reliably confirm that the connection has been formed. Since the vehicle body side system 2 and the tire side device 1 transition to the connected state when the connection is established, they themselves can grasp that they are in the connected state. When the tire side device 1 requests the vehicle body side system 2 to establish a connection in this way, the processes of steps S140 and S145 among the processes shown in FIG. 6 are deleted.

After that, when the connection completion signal is received during the reception waiting state in step 135 of FIG. to be processed.

In this way, the tire device 1 can request the vehicle body system 2 to establish a connection. Even if it does in this way, there can exist an effect similar to 1st Embodiment.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the claims.

(1) For example, in each of the above embodiments, the vibration sensor unit 10 is configured by an acceleration sensor. can also

(2) In each of the above-described embodiments, data including a feature amount is used as the road surface data indicating the road surface state appearing in the detection signal of the vibration sensor section 10 . However, this is only an example, and other data may be used as the road surface data. For example, integrated value data of vibration waveforms in each of the five regions R1 to R5 included in the vibration data during one rotation of the tire 3 may be used as the road surface data. These feature amounts and integral value data are values corresponding to road surface conditions, and are waveform processing values indicating the result of performing waveform processing on the vibration waveform. Since the processed waveform value is a small amount of data, it can be included in the advertisement signal and transmitted to the vehicle body side system 2 .

(3) In each of the above-described embodiments, the road surface condition is determined by calculating the degree of similarity between the feature amount and the support vector by the road surface determination unit 25 of the receiver 21 provided in the vehicle body side system 2 . Further, the receiver 21 transmits instruction signals such as a request signal for detailed data, a connection request signal, and a disconnection request signal.

However, this is only an example, and another ECU such as the brake ECU 22 determines the degree of similarity, determines the road surface condition, or issues an instruction signal. You may make it transmit.

(4) The tire side device 1 is provided with a pressure sensor capable of detecting the tire air pressure and a temperature sensor capable of detecting the tire internal temperature, and the data of the tire air pressure and the tire internal temperature are sent to the vehicle body side system 2 as data related to the tire air pressure. You can also send In this case, since the data related to the tire pressure is a small amount of data, if it is included in the advertisement signal and transmitted together with the waveform processed value such as the feature amount, it is not necessary to establish a connection, so the tire side device 1 is consumed. Power consumption can be reduced.

(5) In the second embodiment, when the vehicle body system 2 requests the detailed data, the tire side device 1 transmits the advertisement signal including the connection request signal. However, this is only an example. For example, when the data amount of the tire side device 1 itself is larger than a predetermined amount, the connection request signal may be included in the advertisement signal and transmitted, and a connection with the vehicle body side system 2 may be established. .

Further, in each of the above-described embodiments, the tire-side device 1 is provided for each of the plurality of tires 3, but at least one may be provided with the device.

Reference Signs List 1 tire side device 2 vehicle body side system 10 vibration sensor section 11 waveform processing section 12, 24 data communication section 13 power supply section 21 receiver 25 road surface determination section

Claims (4)

A tire-side device (1) arranged on a tire (3) for transmitting road surface data, which is data relating to a road surface condition, and a vehicle-body-side system arranged on a vehicle body for receiving the road surface data and determining the road surface condition. (2), wherein the tire side device and the vehicle body side system perform two-way communication,
The tire side device
Between a vibration detection section (10) that outputs a detection signal corresponding to the magnitude of the tire vibration, a waveform processing section (11) that creates the road surface data based on the detection signal, and the vehicle body side system a first data communication unit (12) for performing data communication in
The vehicle body side system
a second data communication unit (24) for performing data communication with the tire-side device; a road surface determination unit (25) for determining a road surface condition based on the road surface data received by the second data communication unit; has
The tire-side device transmits, in an advertising signal, the road surface data including waveform processing values corresponding to the road surface state and indicating the result of waveform processing of the detection signal by the waveform processing unit,
The vehicle body side system determines the road surface state based on the waveform processing value included in the advertising signal ,
Further, when the vehicle body side system cannot determine the road surface condition based on the waveform processing value included in the advertising signal, the vehicle body side system transmits a request signal requesting transmission of detailed data to the tire side device. ,
When the tire-side device receives the detailed data request signal, the tire-side device establishes a connection with the vehicle-body-side system, and after the connection is established, the raw waveform data of the detection signal is used as the road surface data. Road surface condition determination device to be transmitted . A tire-side device (1) arranged on a tire (3) for transmitting road surface data, which is data relating to a road surface condition, and a vehicle-body-side system arranged on a vehicle body for receiving the road surface data and determining the road surface condition. (2), wherein the tire side device and the vehicle body side system perform two-way communication,
The tire side device
Between a vibration detection section (10) that outputs a detection signal corresponding to the magnitude of the tire vibration, a waveform processing section (11) that creates the road surface data based on the detection signal, and the vehicle body side system a first data communication unit (12) for performing data communication in
The vehicle body side system
a second data communication unit (24) for performing data communication with the tire-side device; a road surface determination unit (25) for determining road surface conditions based on the road surface data received by the second data communication unit; has
The tire-side device transmits, in an advertising signal, the road surface data including waveform processing values corresponding to the road surface state and indicating the result of waveform processing of the detection signal by the waveform processing unit,
The vehicle body side system determines the road surface condition based on the waveform processing value included in the advertising signal,
Using the advertising signal as a first advertising signal,
When the vehicle body side system cannot determine the road surface condition based on the waveform processed value included in the first advertising signal, the vehicle body side system transmits a request signal requesting transmission of detailed data to the tire side device. after that, upon receiving a second advertisement signal from the tire-side device, transmitting a connection request signal requesting connection establishment to the tire-side device;
When the tire-side device receives the detailed data request signal, the tire-side device waits for the connection request signal after transmitting the second advertising signal, and establishes a connection with the vehicle body-side system when the connection request signal is received. to establish a connection, and after the connection is established, the raw waveform data of the detection signal is transmitted as the road surface data. A tire-side device (1) arranged on a tire (3) for transmitting road surface data, which is data relating to a road surface condition, and a vehicle-body-side system arranged on a vehicle body for receiving the road surface data and determining the road surface condition. (2), wherein the tire side device and the vehicle body side system perform two-way communication,
The tire side device
Between a vibration detection section (10) that outputs a detection signal corresponding to the magnitude of the tire vibration, a waveform processing section (11) that creates the road surface data based on the detection signal, and the vehicle body side system a first data communication unit (12) for performing data communication in
The vehicle body side system
a second data communication unit (24) for performing data communication with the tire-side device; a road surface determination unit (25) for determining a road surface condition based on the road surface data received by the second data communication unit; has
The tire-side device transmits, in an advertising signal, the road surface data including waveform processing values corresponding to the road surface state and indicating the result of waveform processing of the detection signal by the waveform processing unit,
The vehicle body side system determines the road surface state based on the waveform processing value included in the advertising signal,
Using the advertising signal as a first advertising signal,
If the vehicle body side system cannot determine the road surface condition based on the waveform processing value included in the first advertising signal, it transmits a request signal requesting transmission of detailed data to the tire side device. after that, when receiving a second advertisement signal including a connection request signal requesting connection establishment from the tire-side device, establishing a connection with the tire-side device by establishing a connection;
When the tire-side device receives the detailed data request signal, the tire-side device transmits the second advertising signal, and after the connection is established by the vehicle-body-side system, the raw waveform of the detection signal is used as the road surface data. A road surface condition determination device that transmits data. 4. The waveform processing unit according to any one of claims 1 to 3, wherein the waveform processing unit extracts, as the waveform processed value, a feature quantity indicating characteristics of the vibration of the tire from the detection signal, and creates the road surface data including the feature quantity. 1. The road surface condition determination device according to 1.

Images