JP4073476B2 - Vehicle travel safety evaluation device and vehicle travel safety evaluation method - Google Patents

Description

  The present invention relates to an apparatus and a method for evaluating the degree of safety when a vehicle is running.

  It is important for the driver of an automobile vehicle to know the traveling state of the automobile vehicle that he / she runs. In particular, it is important to know the degree of safety (running safety) during travel of an automobile vehicle that it controls and travels. Here, the traveling safety represents at least one of the ease of steering and the stability of driving of the vehicle when the vehicle is traveling. The traveling safety of the vehicle specifically corresponds to the degree of the degree of slippage between the tire of the automobile vehicle and the road surface. The greater the degree of slippage between the tire and the road surface of the automobile vehicle, the lower the degree of maneuverability and stability of the vehicle and the more difficult the maneuvering of the vehicle. It can be said that the greater the degree of slippage between the tire of the automobile vehicle and the road surface, the lower the traveling safety of the vehicle.

  For example, when a cornering force or a lateral force applied to a tire of the automobile vehicle is increased to some extent while the automobile vehicle is running, slip occurs in a contact area between the tire and the road surface. If this slip becomes relatively large, it becomes difficult to control (control) a vehicle equipped with tires. The degree of such slip that occurs in the contact area between the tire and the road surface is greatly related to the safety of the automobile vehicle during travel. In Patent Document 1 below, tire squeal noise generated according to the degree of slipping is measured by a microphone provided in the vicinity of the vehicle tire, and the grounding of the tire with respect to the road surface is based on the measured tire squeal noise. An apparatus for estimating a state and issuing a warning to a driver based on the estimated ground contact state is disclosed. In this specification, the squealing noise is described in Patent Document 1, and is generated when the tire vibrates due to the slip generated between the tire and the road surface. This refers to a sound of about 1500 Hz. The squeal noise is a sound generated due to tire vibration generated according to the ground contact state between the tire and the road surface, and can be directly measured by, for example, a microphone provided in the vicinity of the tire of the vehicle.

  The following Patent Document 2 and Patent Document 3 also propose a method and an apparatus for evaluating a tire running state based on tire vibration generated according to a ground contact state between a tire and a road surface. In Patent Document 2, as described in Paragraph [0014] of Patent Document 2, the acceleration and sound pressure spectrum inside the tire when traveling on a dry road is used as a reference at a specific frequency during traveling. A method and apparatus for determining a road surface condition by detecting a change from a reference frequency spectrum is disclosed. In Patent Document 2, the road surface condition is evaluated using the frequency spectrum of the acceleration signal in the vehicle longitudinal direction generated in the tire. Further, Patent Document 3 discloses a road surface state and tire traveling state estimation device for the purpose of improving the traveling safety of a vehicle. In Patent Document 3, as described in paragraph [0004] of Patent Document 3, the road surface state where the tire is in contact with the ground and the traveling state of the tire are accurately measured in a constant traveling state in which operations such as braking / driving and steering are not applied. I estimate well. As described in paragraph [0005] of Patent Document 3, the invention described in Patent Document 3 is a vibration frequency obtained by frequency analysis of the vibration in the circumferential direction or the vibration in the width direction of a running tire. The inventor of Patent Document 3 pays attention to the fact that the vibration level of the spectrum is characteristically changed depending on the road surface state where the tire is in contact with the ground and the failure mode of the tire. The invention described in Patent Document 3 acquires information on vibrations of wheels and suspensions as information representing tire vibrations, and travels from a vibration level in a specific frequency band of a frequency spectrum obtained by frequency analysis of the acquired vibrations. The road surface condition (mainly, the coefficient of friction between the road surface and the tire) and the running state of the tire (tire internal pressure, wear, failure, etc.) are estimated.

JP-A-5-332889 JP 2002-340863 A JP 2003-182476 A

  In the tire ground contact state estimation method and apparatus described in Patent Literature 1, the generated tire squeal noise is directly measured by a microphone provided in the vicinity of the vehicle tire. As described above, when the microphone is installed in the vicinity of the tire, there is a problem that it is easily influenced by external sounds such as engine sound and wind noise, and the ground contact state of the tire cannot be accurately estimated.

  The road surface determination device described in Patent Document 2 and the road surface state and tire running state estimation methods described in Patent Document 3 are both intended to determine the road surface state. In the road surface judging device described in Patent Document 2 that evaluates the road surface state using the frequency spectrum of the acceleration signal in the vehicle longitudinal direction generated in the tire, the driver of the automobile vehicle is running the automobile vehicle that the driver controls. You can know the degree of slipperiness on the road surface. However, for example, it has not been possible to know the degree of slipping in the contact area between the tire and the road surface, which changes every moment during steering of an automobile, and the vehicle traveling safety according to the size of the slipping. Further, in the invention described in Patent Document 3, the road surface condition and the tire running condition are estimated based on the level of the frequency spectrum of the vibration obtained by frequency analysis of the circumferential or widthwise vibration of the running tire. However, it was impossible to know the degree of slipping in the contact area between the tire and the road surface, which changes every moment during the steering of the automobile, and the traveling safety of the vehicle according to the size of the slip. Accordingly, an object of the present invention is to accurately evaluate the traveling safety of a vehicle, which changes every moment during steering of an automobile vehicle.

  In order to solve the above-described problems, the present invention relates to a vehicle having wheels equipped with tires, and is an apparatus for evaluating traveling safety when the vehicle travels on a road surface. The vehicle travels on a road surface. When the rolling tire receives an external force from the road surface, means for acquiring in a time series acceleration data at a predetermined position fixed to the tire, and frequency analysis of the time series acceleration data. Means for determining the acceleration spectrum; means for detecting a peak value of the acceleration spectrum in a frequency range of 500 Hz to 1500 Hz; and means for evaluating the driving safety of the vehicle according to the detected peak value. And a vehicle travel safety evaluation device characterized by comprising: The acceleration data acquired by the acceleration data acquisition means is preferably acceleration data in the radial direction of the tire.

  Further, the acceleration data of the predetermined position of the tire is arranged at the predetermined position of the tire, and is generated when the rolling tire receives an external force from the road surface when the vehicle travels on the road surface. It is preferably measured by an acceleration sensor that measures and outputs the acceleration of the position.

  Further, the means for obtaining the spectrum may be configured so that, from the measurement time range of the acquired time-series acceleration data, the predetermined position passes through a portion corresponding to the contact area between the tire and the road surface, and then passes through the tire shaft. It is preferable that an analysis target time region until reaching a position opposite to the center of the ground contact region is extracted, and the time-series acceleration data spectrum in the analysis target time region is obtained as the acceleration spectrum. The means for obtaining the spectrum preferably extracts the analysis target time region based on the acquired time-series acceleration data.

  The means for evaluating evaluates the driving safety of the vehicle for each rotation of the tire according to the maximum value of the peak value of the spectrum of the time-series acceleration data in the analysis target time region. It is preferable.

  In addition, a storage unit that stores a predetermined threshold value is provided, and the evaluation unit reads the threshold value from the storage unit, compares the read threshold value with the peak value, and responds to the comparison result. It is preferable to determine whether or not the vehicle is in a safe traveling state and output the determined result. The threshold is a cornering force generated in the tire, which is acquired in advance using a tire testing machine that measures at least one of a cornering force value and a lateral force value generated in the rolling tire. 500 Hz of a spectrum of acceleration at a predetermined position fixed to the tire, generated during rolling in the tire testing machine, and at least one of the value of the lateral force generated in the tire and the value of the lateral force generated in the tire It is preferably determined in advance based on a correspondence relationship with a peak value in a frequency range of ˜1500 Hz.

  The present invention also relates to a method for evaluating traveling safety when the vehicle travels on a road surface with respect to a vehicle having wheels on which tires are mounted, and the vehicle is rolling when the vehicle travels on the road surface. A step of acquiring acceleration data at a predetermined position fixed to the tire, which is generated when the tire receives an external force from the road surface, in time series; and a frequency analysis of the time series acceleration data to obtain a spectrum of the acceleration. Determining a peak value in a frequency range of 500 Hz to 1500 Hz corresponding to a frequency of a squeal sound generated from the tire in the spectrum of the acceleration, and traveling of the vehicle according to the detected peak value. There is also provided a vehicle travel safety evaluation method characterized by having a step of evaluating safety.

  In the step of obtaining the spectrum, the predetermined position passes through a portion corresponding to the ground contact region between the tire and the road surface in the time region corresponding to the time-series acceleration data, and then passes through the tire shaft. It is preferable that an analysis target time region until reaching a position opposite to the center of the ground contact region is extracted, and the time-series acceleration data spectrum in the analysis target time region is obtained as the acceleration spectrum. Further, in the step of obtaining the spectrum, it is preferable to extract the analysis target time region based on the acquired time-series acceleration data.

  According to the present invention, it is possible to accurately evaluate the traveling safety of the automobile vehicle according to the magnitude of the slip in the contact area between the tire and the road surface, which changes every moment when the automobile vehicle is steered.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus and a method for evaluating the traveling safety of a vehicle according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  FIG. 1 is a schematic configuration diagram illustrating an evaluation device 10 (device 10) which is an example of a device for evaluating the traveling safety of a vehicle according to the present invention. The device 10 is provided in a vehicle 12 provided with four wheels 14a to 14d. The apparatus 10 includes sensor units 16a to 16d, a determination unit 20, and a notification unit 34. The sensor units 16a to 16d are respectively provided on the four wheels 14a to 14d, and are generated when the tires 15 (see FIG. 2) of the wheels receive external force from the road surface when the vehicle 12 travels on the road surface. The acceleration information of the predetermined part of the tire 15 is acquired and transmitted by a radio signal. The determination means 20 receives the radio signals transmitted from the sensor units 16a to 16d, acquires acceleration data of a predetermined part of the tire 15 in time series, performs frequency analysis on the acquired time series acceleration data, and obtains acceleration data. Is determined, and based on the frequency spectrum of the acceleration data, it is determined whether or not the current traveling state of the vehicle 12 is safe. The notification unit 34 notifies the determination result of the determination unit 20 and issues a warning to the driver of the vehicle 12 according to the determination result of the determination unit 20.

  FIG. 2 is a diagram illustrating a sensor unit and a data processing unit in the vehicle travel safety evaluation apparatus shown in FIG. The determination unit 20 illustrated in FIG. 2 includes a receiver 3, an amplifier (AMP) 4, a data processing unit 21, a CPU 23, and a memory 27. The determination unit 20 is a computer including the receiver 3 and the AMP 4 in which each unit (each unit to be described later) of the data processing unit 21 functions when the CPU 23 executes a program stored in the memory 27. Based on the measurement data of the acceleration in the tread portion 19 of the tire 15 constituting the wheel 14 (representing any one of the wheels 14a to 14d), the determination means 20 is safe in the current traveling state of the vehicle 12. It is determined whether or not. The acceleration measurement data used here is detected by the acceleration sensor 2 fixed to the inner peripheral surface of the tire hollow region of the tread portion 19 of the tire 15 and is transmitted from the transmitter 17 of the sensor unit 16 provided on the wheel 14. The data is transmitted to the receiver 3 and amplified by the amplifier 4. Note that the transmitter 17 may not be provided, and for example, the acceleration sensor 2 may be separately provided with a transmission function and transmitted from the acceleration sensor 2 to the receiver 3. Each transmitter 17 provided on each of the wheels 14a to 14d has identification information (ID) that enables identification, and the transmitter 17 measures acceleration measured by a corresponding acceleration sensor. An ID is transmitted together with the data.

As the acceleration sensor 2, for example, a semiconductor acceleration sensor disclosed in Japanese Patent Application No. 2003-134727 filed earlier by the applicant of the present application is exemplified. Specifically, the semiconductor acceleration sensor includes a Si wafer having a diaphragm formed in the outer peripheral frame portion of the Si wafer, and a pedestal for fixing the outer peripheral frame portion, and a weight is provided at the center of one surface of the diaphragm. And a plurality of piezoresistors are formed on the diaphragm. When acceleration is applied to the semiconductor acceleration sensor, the diaphragm is deformed, and the resistance value of the piezoresistor changes due to the deformation. A bridge circuit is formed so that this change can be detected as acceleration information.
By fixing this acceleration sensor to the tire inner peripheral surface, the acceleration acting on the tread portion 19 during tire rotation can be measured.
In addition to this, the acceleration sensor 2 may be an acceleration pickup using a piezoelectric element, or a strain gauge type acceleration pickup combined with a strain gauge.

  The data processing means 21 to which the acceleration measurement data amplified by the amplifier 4 is supplied includes a data acquisition unit 22, a time domain extraction unit 24, a frequency analysis unit 26, a peak value derivation unit 28, and an evaluation unit 29. The data acquisition unit 22 is a part that acquires, as input data, acceleration measurement data for at least one rotation of the tire amplified by the amplifier 4. The data supplied from the amplifier 4 is analog data, and the data acquisition unit 22 samples this data at a predetermined sampling frequency and converts it into digital data (acquired acceleration data). The acquired acceleration data is stored in the memory 27. In addition, the data acquisition part 22 is the measurement data of the acceleration of the tire of which wheel the measurement data of the acceleration transmitted from each wheel based on the above-mentioned ID transmitted from each transmitter 17 (wheels 14a to 14). Which wheel of the wheels 14d is determined). Thereafter, each process performed by the time domain extracting unit 24, the frequency analyzing unit 26, the peak value deriving unit 28, and the evaluating unit 29 is performed for each measurement data of the tire of each wheel.

  The time domain extraction unit 24 reads the acquired acceleration data from the memory 27. Based on the time-series acquired acceleration data, the time domain extraction unit 24 passes the portion corresponding to the ground contact area between the tire 15 and the road surface, and then the center position of the ground contact area via the tire axis. The time domain for analysis until the position on the opposite side is reached is extracted. The analysis target time region refers to a time region in which the acceleration sensor 2 is located in the analysis target portion indicated by α in FIG. In the time domain extraction unit 24, for example, time series data (deformation acceleration data) representing acceleration components based on tire deformation by removing centrifugal force components caused by tire rolling from time series acquired acceleration data. To extract. The time domain extraction unit 24 extracts an analysis target time domain using the deformation acceleration data. The time domain extraction unit 24 receives, for example, acceleration data acquired by the data acquisition unit 22 and converted into digital data, and smoothes this data, thereby representing time series data representing acceleration components based on tire deformation. (Deformation acceleration data) may be extracted, and the analysis target time region may be extracted using the deformation acceleration data.

  To obtain smoothed acceleration data by smoothing the acquired acceleration data, a known method such as a method using a trend model, a method using a digital filter, a method using a moving average process, or a method using a spline function is used. Any of these may be used. Acquired acceleration data uses a change in acceleration based on tire deformation caused by deformation of the tire rolling on the road surface as a trend component, and the acceleration component based on this tire deformation includes many noise components such as tire vibration. It is included data. For example, it can be said that acceleration data smoothed by a technique using a known trend model represents an acceleration component obtained by removing a noise component from acquired acceleration data. The time domain extraction unit 24 may extract the analysis target time domain using such smoothed acceleration data.

  The time domain extracting unit 24 may extract tire deformation acceleration data as follows. FIGS. 3A to 3C are diagrams illustrating an example of processing performed in the time domain extraction unit 24. FIG. In this embodiment, smoothing processing is performed on the acquired acceleration data (FIG. 3A), and an approximate curve is calculated for the smoothed acceleration data to obtain the background component 1 (FIG. 3B). . Then, the background component 1 is removed from the smoothed acceleration data, and time series data of acceleration based on tire deformation (deformation acceleration data of the tire) is extracted (FIG. 3C). For calculating the approximate curve for the smoothed acceleration data, any of known methods such as a method using a trend model, a method using a digital filter, a method using a moving average process, and a method using a spline function may be used. Good.

  The time domain extraction unit 24 calculates the timing at which the acceleration sensor 2 provided in the tread unit 19 passes the front end portion of the tire contact area from the time-series waveform of the deformation acceleration data (the front contact end timing), and the acceleration sensor 2 detects the tire contact with the tire. The timing at which the rear end portion of the area is passed (ground rear end timing) is extracted. For example, two timings when the time series waveform of the deformation acceleration data crosses acceleration 0 are extracted, and one earlier timing is extracted as the ground contact end timing, and one later timing is extracted as the ground contact end timing. The time domain extraction unit 24 extracts an analysis target time domain on the basis of the extracted front contact end timing and contact back end timing. The extraction of the analysis target time region will be described in detail later.

  Here, the relationship between the vibration generated in the tire and the slip angle of the tire contact area, which was first discovered by the inventor of the present application, which the inventor of the present application focused on when creating the present invention, will be described.

  4 (a) to 4 (f) are diagrams for explaining vibrations generated in a tire of a running vehicle, and using a known flat belt type indoor running tester, the tread portion 19 is similar to the tire 15 described above. This is data obtained by applying a slip angle input to a tire A having a predetermined specification provided with an acceleration sensor on the inner surface. At this time, the acceleration sensor provided in the tire A can measure not only the acceleration of the tire tread portion 19 in the tire radial direction but also the acceleration in the tire circumferential direction and the acceleration in the tire width direction. It was used. FIG. 4F shows time-series data of slip angles between the tire A and the ground road surface. As shown in FIG. 4F, the tire A was given a slip angle input that monotonously increased in time series. FIG. 4A shows acquired acceleration data in the radial direction obtained by digitally converting the acceleration data in the tire radial direction measured by the acceleration sensor provided on the tire A. FIG. FIG. 4E shows the smoothed acceleration data of the radial acceleration that has been smoothed by removing the high-frequency component of the acquired acceleration data in the radial direction. FIGS. 4B to 4D show the frequency spectrum (vibration spectrum) of the acquired acceleration data obtained by frequency analysis of the acquired acceleration data every predetermined minute time region (0.0016 seconds). It represents a change in the series. FIG. 4B is time series data of the frequency spectrum in the tire circumferential direction, FIG. 4C is time series data of the frequency spectrum in the tire width direction, and FIG. 4D is the tire radial direction. Frequency spectrum data. Each horizontal axis of FIGS. 4A to 4F is a time axis, and the same coordinates on each time axis represent the same time. In this experiment conducted using the tire A, a squeal noise was generated from the tire A when the magnitude of the slip angle input applied to the tire A increased to some extent (specifically, the slip angle was 3 °). It was confirmed by an operator located near the tire A.

A tire that rolls on the road surface has a deformation acceleration in the tire radial direction that varies in a time series as shown in FIG. That is, as is clear from FIG. 2, the radial deformation of the tire increases at the moment when it approaches the front end of the ground contact area, and the acceleration sensor moves in parallel with the road surface while passing through the ground contact area. Therefore, it becomes small (particularly zero at the center position of the grounding area), and becomes large again when passing through the rear end of the grounding area. For this reason, based on the smoothed acceleration data in the tire radial direction excluding high-frequency components (noise components) as shown in FIG. 4E, the tire and road surface as shown in FIG. It is possible to determine a time region where the acceleration sensor is approaching the ground contact region (ground contact time region C _{1 to} C ₈ ). Note that the smoothing process and the determination process of the contact time period will be described later.

  The acquired acceleration data in the tire radial direction shown in FIG. 4A is obtained by adding other noise components (mainly, the acceleration data in time series generated as the tire is deformed) shown in FIG. Tire vibration component). As can be seen by comparing FIG. 4F and FIG. 4A, the noise component of the acquired acceleration data increases as the tire slip angle increases. The inventor of the present application pays attention to noise components in the tire width direction, the circumferential direction, and the radial direction, which increase as the tire slip angle increases, and as shown in FIGS. The time change of the frequency spectrum of the acquired acceleration data generated in the experiment was derived, and the mode of the change was confirmed. The vertical axis of the graphs of FIGS. 4B to 4D is the frequency, and the magnitude of the spectral value is represented by the degree of color shading (dot density).

As a result of comparing and examining the graphs of FIGS. 4B to 4D, the inventor of the present application shows that the noise component of the acquired acceleration data appears most strongly in the tire radial direction among the tire width direction, the circumferential direction, and the radial direction. I found. Then, regarding the frequency spectrum of the acquired acceleration data in the tire radial direction shown in FIG. 4D, the correspondence with the contact time regions C _{1 to} C ₈ determined from the graph shown in FIG. The relationship between the position of the acceleration sensor provided on the moving tire on the tire and the frequency spectrum in the radial direction was investigated. Thus, the present inventors, as shown in FIG. 4 (d), the frequency spectrum of the radial, not only the time in which the acceleration sensor is located in the ground area (contact time domain C ₁ -C ₈₎ , A predetermined time region (analysis target time region E _{1 to} E) from immediately after the acceleration sensor passes through the rear end of the ground contact region until it reaches a point opposite to the center position of the ground contact region via the tire shaft. ₈ ) However, it was found that the high spectral value is still maintained. In other words, when squeal noise is generated from the tire as the slip angle increases, it is found that particularly large tire vibration is generated from the front end of the tire contact area to the rear side (analysis target portion) of the tire contact area. It was. And it has been found that this vibration is particularly dominant in the tire radial direction.

As can be seen by comparing FIGS. 4B to 4D, the tire radial direction appears most prominently as the frequency spectrum of the acquired acceleration data. It can be seen that the peak of the frequency spectrum is concentrated in the range of 500 Hz to 1500 Hz from the contact time region to the analysis target time region, and the peak frequency is in the frequency range of 500 Hz to 1500 Hz. As described above, the frequency range of 500 Hz to 1500 Hz is a frequency range corresponding to the squeal noise generated in the tire. Further, when the distribution of the frequency spectrum values in the ground contact time region C _{1 to} C ₈ is compared with the distribution of the frequency spectrum values in the analysis target time regions E _{1 to} E ₈ immediately after the ground contact time region, the ground contact time region C ₁ compared to the peak frequency in the -C _8, towards the peak frequency in the analyzed time domain E ₁ to E ₈ is (low frequency) and is lower can be seen.

  5 (a) to 5 (f) are also diagrams for explaining vibrations generated in the tires of the traveling vehicle, as in FIGS. 4 (a) to (f). FIGS. 5A to 5F also show tires having specifications different from those of the tire A, in which an acceleration sensor is provided on the inner surface of the tread portion 19 in the same manner as the tire 15 using a known flat belt type indoor running test machine. Data obtained by applying slip angle input to B. In this experiment conducted using the tire B, the operator who was located near the tire B even if the slip angle input was monotonously increased until the slip angle reached 10 °, as in the case where the tire A was used. However, it was not possible to confirm that squeal noise was generated from the tire B. In this case, a characteristic noise component did not appear in each data shown in FIGS.

FIG. 6A shows a frequency spectrum in the radial direction over a time region in which the tire makes one rotation when a slip angle input having a slip angle of 6 ° is given to the tire A. FIG. As can be determined from the graphs of FIG. 4, in this state (slip angle 6 °), a squeal noise is generated in the tire A. As shown in FIG. 6A, in the state where the squeal noise is generated, the frequency spectrum in the radial direction has a relatively large spectrum value in the frequency range of 500 Hz to 1500 Hz, and naturally peaks in this frequency range. have. In the frequency spectrum in the radial direction shown in FIG. 6A, two distinctive peaks can be confirmed. Figure 4 (d) As is clear from, among the two characteristic peaks shown in FIGS. 6 (a), (indicated by P ₁ in FIG. 6 (a)) relatively low frequency peak is mainly It is due to the tire vibration in the analysis target part, a relatively high peak (indicated by P ₂ in FIG. 6 (a)), mainly in the tire vibration of the middle of the acceleration sensor is passing through the tire contact area Is attributed.

As can be seen by comparing the two characteristic peaks shown in FIG. 6A, the vibration component in the analysis target portion is dominant in the tire vibration over the time region in which the tire makes one rotation (FIG. 6A). ), the larger is more of _{P 1).} FIG. 6B shows a frequency spectrum in the radial direction over a time region corresponding to one rotation of the tire when a slip angle input with a slip angle of 10 ° is given to the tire B different from the tire A. As can be determined from each graph of FIG. 4, the squeal noise is not generated in the tire 15 even in this state (slip angle 10 °). As shown in FIG. 6B, in the state where no squeal noise is generated, there is no significant peak in the frequency range of 500 Hz to 1500 Hz.

  The present invention is obtained by such a confirmation experiment conducted by the inventor of the present application. (1) When tire squeal noise is generated as the slip angle increases, noise components (mainly tire vibrations) of acquired acceleration data are generated. Component) should appear most strongly in the tire radial direction among the tire width direction, circumferential direction, and radial direction. (2) The frequency spectrum value of the acquired acceleration data in the tire radial direction is not only the time when the acceleration sensor is located in the ground contact area (ground contact time area) but immediately after the acceleration sensor passes the rear end of the ground contact area. The high value is still maintained even in a predetermined time region from when the vehicle reaches the point opposite to the center position of the ground contact region through the tire shaft. Rather, it is dominated in a predetermined time region (analysis target time region) from immediately after the acceleration sensor passes through the rear end of the ground contact region to the point opposite to the center position of the ground contact region via the tire shaft. Big. (3) And the peak frequency of such a frequency spectrum in the radial direction is in the frequency range of 500 Hz to 1500 Hz corresponding to the squeal noise generated in the tire. It was made based on such knowledge.

  The time domain extraction unit 24 extracts the analysis target time domain, as described above, in the noise component (mainly vibration component) of the acquired acceleration data in the tire radial direction in the time domain over one rotation of the tire. This is because the noise component of the acquired acceleration data in the tire radial direction in the target time region is dominantly large. The analysis time domain information extracted by the time domain extraction unit 24 is sent to the frequency analysis unit 26.

  The frequency analysis unit 26 receives the analysis time domain information and reads the acquired acceleration data from the memory 27. The frequency analysis unit 26 performs frequency analysis of the acquired acceleration data for each analysis target time region for each rotation of the tire extracted by the time region extraction unit 24, and is shown in FIGS. 6 (a) and 6 (b). The frequency spectrum of the acquired acceleration data in the tire radial direction is obtained. The frequency analysis unit 26 outputs the obtained frequency spectrum in the radial direction to the peak value deriving unit 28. The peak value deriving unit 28 obtains a peak value (spectrum peak value) of the frequency spectrum from the radial frequency spectrum output from the frequency analyzing unit 26, and further calculates a maximum value (maximum spectrum peak value) of the obtained peak values. ) Is derived.

  7 (a) and 7 (b) show the magnitude of the slip angle, the lateral force generated in the ground contact area of the tire, and the tire derived from a known indoor tire testing machine. It is a graph showing the correspondence with the maximum spectrum peak value of the acquisition acceleration data of radial direction, and each. FIG. 7A is a graph showing a correspondence relationship between the maximum spectrum peak value and the slip angle in the time region in which the tire makes one rotation of the acquired acceleration data (acquired acceleration data). FIG. 7B is a graph showing the correspondence between the maximum spectral peak value and the slip angle in the analysis target time region, obtained by frequency analysis of the acquired acceleration data only in the analysis target time region. Fy shown in FIGS. 7 (a) and 7 (b) is a lateral force generated in the tire contact area, and Ax to Az shown in FIGS. 7 (a) and 7 (b) is Ax in the tire circumferential direction. The spectral peak value, Ay is the maximum spectral peak value in the tire width direction, and Az is the maximum spectral peak value in the tire radial direction. The maximum spectrum peak value in each direction is obtained by frequency-analyzing the acquired acceleration data in the time domain in which the tire rotates once, obtaining a spectrum (frequency spectrum), obtaining a peak value of the frequency spectrum from each frequency spectrum, It is obtained by extracting the maximum value. As shown in FIGS. 7A and 7B, as the slip angle between the tire and the road surface increases, the value of the maximum spectral peak value also increases monotonously.

  In both cases of FIG. 7A and FIG. 7B, the slip angle between the tire and the road surface and the maximum spectral peak value in each direction show a good linear relationship. In both cases of FIG. 7A and FIG. 7B, the slip angle between the tire and the road surface exhibits a particularly good linearity with the maximum spectral peak value in the tire radial direction. The slip angle between the tire and the road surface and the maximum spectral peak value show a good linear relationship not only in the graph shown in FIG. 7 (a) but also in the graph shown in FIG. 7 (b). This is because the component (mainly vibration component) is dominantly large in this analysis target time region in the time region in which the tire rotates once. Further, when FIG. 7A is compared with FIG. 7B, the value of Az (maximum spectral peak value in the tire radial direction) in the whole range of the slip angle is compared with FIG. 7A. FIG. 7B is larger. As described above, the peak frequency corresponding to the maximum spectral peak value is in the frequency range of 500 Hz to 1500 Hz corresponding to the squeal noise generated in the tire. The maximum spectral peak value obtained by frequency analysis of the acquired acceleration data in the tire radial direction only in the analysis target time domain is the time domain (including the ground contact area) of the acquired acceleration data in the tire radial direction over one rotation of the tire. It can be said that the sensitivity to the squeal sound (corresponding vibration) is better than the maximum spectral peak value obtained by frequency analysis. In the present embodiment, an evaluation value representing the magnitude of the slip angle between the tire and the road surface is derived using such a maximum spectral peak value in the analysis target time region.

  Thus, the magnitude of the peak value of the frequency spectrum of the acquired acceleration data in the tire radial direction accurately represents the magnitude of the slip angle between the tire and the road surface. In the present embodiment, for example, with respect to the tire 14 mounted on the vehicle 12, a correspondence relationship between the slip angle and the maximum spectrum peak value is derived in advance using a known indoor tire testing machine, so that the vehicle is safe. The maximum spectrum peak value corresponding to the upper limit value of the slip angle at which the vehicle can travel is set as a threshold for determining the current traveling safety of the vehicle. The set threshold value is stored in the memory 27 in advance.

  The evaluation unit 29 compares the maximum spectrum peak value (evaluation value) derived for each rotation of the tire in the peak value deriving unit 28 with this threshold value stored in advance in the memory 27, and the evaluation value is set to the threshold value. It is determined whether or not it exceeds, and the determination result is displayed on the display. Here, the threshold value represents the upper limit value of the slip angle at which the vehicle can travel safely as described above. When the evaluation value (the maximum spectral peak value in the radial direction of the tire, which corresponds well to the size of the slip angle of the tire 15) is below the preset threshold value, the size of the slip angle between the tire 15 and the road surface Can be said to be in a range where the vehicle 12 including the tire 15 can travel safely. Further, when the evaluation value is larger than the preset threshold value, the size of the slip angle between the tire 15 and the road surface is larger than the upper limit value at which the vehicle 12 including the tire 15 can travel safely, It can be said that the vehicle 12 is not in a safe traveling state.

  The notification means 34 is composed of, for example, a display or a speaker (not shown), and receives information on a determination result sent from the evaluation unit 29 as to whether or not the vehicle is in a safe traveling state, and notifies the driver of the vehicle 12. An alarm is issued. Thus, the notification unit 34 notifies the driver of the vehicle 12 which wheel has an extremely large slip angle. For example, a warning may be generated by generating a warning sound from a speaker or displaying an image indicating the warning on a display.

  FIG. 8 is an example of a flowchart of a vehicle travel safety evaluation method performed by such an apparatus 10. Hereinafter, an example in which vehicle traveling safety is evaluated while the vehicle 12 is traveling will be described. First, the acceleration measurement data of each wheel amplified by the amplifier 4 is supplied to the data acquisition unit 22 and sampled at a predetermined sampling frequency to acquire digitized measurement data (step S102). At this time, as described above, the data acquisition unit 22 is based on the above-mentioned ID transmitted from each transmitter 15, and the acceleration measurement data transmitted from each wheel is the measurement data of the acceleration of the tire of which wheel. It is determined whether there is any wheel (wheel 14a to wheel 14d). The subsequent processes are performed in parallel for the measurement data of the tires of the wheels.

  The acquired measurement data (acquired acceleration data) is stored in the memory 27. The time domain extraction unit 24 reads the acquired acceleration data from the memory 27. Then, in the time domain extraction unit 24, first, smoothing processing using a low-pass filter is performed (step S104). As shown in FIG. 4A and FIG. 5A, the measurement data supplied to the time domain extraction unit 24 includes a lot of noise components. The data is smooth as shown in e). For example, a digital filter having a predetermined frequency as a cutoff frequency is used as the filter. The cut-off frequency varies depending on the rolling speed and noise components. For example, when the rolling speed is 60 (km / hour), the cut-off frequency is set to 0.5 to 2 (kHz). In addition, a smoothing process may be performed using a moving average process, a trend model, or the like instead of the digital filter.

Next, from the time-series waveform of the acceleration data smoothed by the time domain extraction unit 24, the timing at which the acceleration sensor 2 provided in the tread unit 19 passes the front end portion of the tire ground contact region (ground contact front end timing), The timing at which the acceleration sensor 2 passes the rear end portion of the tire ground contact area (ground rear end timing) is extracted. Specifically, two timings when the time-series waveform of the deformation acceleration data obtained by extracting the centrifugal force component from the acceleration data in the tire radial direction crosses acceleration 0 are extracted, and one of the earlier timings is extracted. The timing before the ground contact and one of the later timings is extracted as the timing after the ground contact. FIG. 9 is a schematic diagram showing a time-series waveform of deformation acceleration data, which is shown over a time range in which the tire rotates twice. As shown in FIG. 9, the time domain extracting unit 24 extracts the front contact end timing (F _n and F _{n + 1} ) and the rear contact end timing (R _n and R _{n + 1} ) for each rotation of the tire.

Then, the time domain extraction unit 24 extracts and sets the analysis target time domain for each rotation of the tire. As described above, the analysis target time region is a time region corresponding to the time during which the acceleration sensor 2 passes through the analysis target portion α shown in FIG. 2, and more specifically, as described above, It means the time region from passing through the portion corresponding to the contact area with the road surface until reaching the position opposite to the center point of the contact area via the tire shaft. When the tire is rolling at a constant speed, from the timing when the acceleration sensor passes the rear end portion of the tire ground contact region (for example, the rear contact end timing R _n shown in FIG. 9), the acceleration sensor 2 is in the tire ground contact region. In the time range up to the next timing of passing through the front end portion (for example, grounding front end timing F _{n + 1} ), the time region (for example, as shown in FIG. E _n ). In the time domain extraction unit 24, based on the extracted contact front end timing and contact rear end timing, for example, as shown in FIG. 4 (e) and FIG. (Analysis target time regions E _{1 to} E ₈ ) are extracted.

  Then, the frequency analysis unit 26 receives the analysis time domain information and reads the acquired acceleration data from the memory 27. The frequency analysis unit 26 performs frequency analysis of time-series acquired acceleration data for each analysis target time region of each rotation of the tire extracted by the time region extraction unit 24, and a frequency spectrum (radius of acquired acceleration data in the tire radial direction). The vibration spectrum in the direction is obtained and output (step S110).

  Then, the peak value deriving unit 28 determines from the radial frequency spectrum output from the frequency analyzing unit 26 the maximum value of the peak value of the radial frequency spectrum in the frequency range of 500 Hz to 1500 Hz (maximum spectral peak value). Is derived (step S112). Then, the evaluation unit 29 evaluates the current traveling safety of the vehicle 12 based on the maximum spectrum peak value derived for each rotation of the tire (each analysis target time region) (step S114). The evaluation unit 29 compares the evaluation value for each rotation of the tire derived in step S112 with the threshold value stored in advance in the memory 27 to determine whether or not the evaluation value exceeds the threshold value. The result is displayed and output on a display (not shown) of the notification means 34.

  When the evaluation value falls below the preset threshold value (when the determination result in step S114 is Yes), the slip angle between the tire 14 and the road surface is such that the vehicle 12 including the tire 14 can travel safely. It can be said that it is in range. In this case (when the determination result in step S114 is Yes), the determination result is displayed on the display in the normal display mode. On the other hand, when the evaluation value is larger than the preset threshold value (when the determination result in step S114 is No), the vehicle 12 including the tire 14 has a slip angle between the tire 14 and the road surface. It is larger than the upper limit value that allows safe traveling, and it can be said that the vehicle 12 is not in a safe traveling state. In this case (when the determination result of step S114 is No), a warning is issued by the notification means 34 (step S116). For example, by generating a warning sound from a speaker or displaying an image that conveys a warning on a display, a warning is given to the driver of the vehicle 12 and at which wheel the slip angle is extremely large is notified. . Such an alarm allows the driver of the vehicle 12 to know whether or not the current vehicle is in a safe driving state. A series of processing from step S102 to step S116 is repeatedly executed until the vehicle 12 finishes traveling.

  The evaluation value is not limited to the maximum value of the peak value of the frequency spectrum (maximum spectrum peak value) in the analysis target time region. Also, the time domain for frequency analysis is not particularly limited. For example, the evaluation value may be a peak value of a vibration spectrum in the time domain where the tire rotates once. However, since the noise component of tire vibration during rolling is dominantly large in the analysis target portion of the tire, in order to evaluate the driving safety of the vehicle with higher accuracy, the frequency in the analysis target time domain is used as an evaluation value. It is preferable to use the peak value of the spectrum. Further, the evaluation value is not limited to using the maximum spectrum peak value in the tire radial direction, and a spectrum value in the tire circumferential direction or the tire width direction may be used. However, the acceleration in the tire radial direction is particularly larger than the acceleration in the tire circumferential direction and the acceleration in the tire width direction. In order to evaluate the traveling safety of the vehicle with higher accuracy, it is more preferable to use the maximum value of the spectrum value of the acceleration in the tire radial direction as the evaluation value.

  The present invention is not limited to calculating an evaluation value for each rotation of the tire and evaluating the running safety for each rotation of the tire. For example, an evaluation value per one tire rotation may be calculated at a predetermined time interval, and the determination may be made at the predetermined time interval. In addition, an evaluation value for each rotation of the tire is calculated continuously in a predetermined time unit, an average value is obtained for a plurality of evaluation values acquired in the predetermined time unit, and the average value is used for a predetermined time. You may determine the driving safety of a vehicle for every unit. The determination method and determination criteria in the present invention are not particularly limited.

  As mentioned above, although the vehicle travel safety evaluation apparatus and the vehicle travel safety evaluation method of the present invention have been described in detail, the present invention is not limited to the above-described embodiment, and various improvements can be made without departing from the gist of the present invention. Of course, you may make changes.

It is a schematic block diagram explaining an example of the vehicle travel safety evaluation apparatus of this invention. It is a figure explaining the sensor unit and the data processing unit in the vehicle travel safety evaluation apparatus shown in FIG. (A)-(c) is a figure explaining the example of the process implemented in the time-domain extraction part shown in FIG. (A)-(f) is a figure explaining the vibration generate | occur | produced in the tire of the vehicle in driving | running | working. (A)-(f) is a figure explaining the vibration generate | occur | produced in the tire of the vehicle in driving | running | working. (A) and (b) are frequency spectra of acceleration in the tire radial direction when slip angle input is given to different tires. (A) And (b) is a scatter diagram showing the correspondence of the maximum value of the frequency spectrum of the lateral force generated in the contact area of the tire and the acceleration in the tire radial direction with respect to the magnitude of the slip angle for different tires. It is. It is a flowchart which shows an example of the vehicle travel safety evaluation method of this invention. It is the schematic which shows the time-sequential waveform of the acceleration of a tire radial direction, while a tire rotates 2 times.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Evaluation apparatus 12 Vehicle 14a-14d Wheel 15 Tire 16a-16d Sensor unit 17 Transmitter 20 Determination means 21 Data processing means 22 Data acquisition part 23 CPU
24 Time domain extraction unit 26 Frequency analysis unit 27 Memory 28 Peak value deriving unit 29 Evaluation unit 34 Notification means

Claims (11)

For a vehicle having wheels equipped with tires, an apparatus for evaluating the traveling safety when the vehicle travels on a road surface,
Means for acquiring, in a time series, acceleration data at a predetermined position fixed to the tire, generated when the rolling tire receives an external force from the road surface when the vehicle travels on a road surface;
Means for frequency-analyzing the time-series acceleration data to obtain the acceleration spectrum;
Means for detecting a peak value in a frequency range of 500 Hz to 1500 Hz of the acceleration spectrum;
Means for evaluating the traveling safety of the vehicle according to the detected peak value.   2. The vehicle travel safety evaluation device according to claim 1, wherein the acceleration data acquired by the acceleration data acquisition means is data of acceleration in the radial direction of the tire.   The acceleration data of the predetermined position of the tire is arranged at the predetermined position of the tire and is generated when the rolling tire receives an external force from the road surface when the vehicle travels on the road surface. 3. The vehicle travel safety evaluation device according to claim 1, wherein the vehicle travel safety evaluation device is measured by an acceleration sensor that measures and outputs an acceleration. The means for obtaining the spectrum, from the measurement time range of the acquired time-series acceleration data, after the predetermined position has passed the portion corresponding to the contact area of the tire and the road surface, the ground contact via the tire shaft Extract the time domain to be analyzed until it reaches the position opposite to the center of the area,
The vehicle travel safety evaluation device according to claim 1, wherein a spectrum of the time-series acceleration data in the analysis target time domain is obtained as the acceleration spectrum.   5. The vehicle travel safety evaluation device according to claim 4, wherein the means for obtaining the spectrum extracts the analysis target time region based on the acquired time-series acceleration data.   The evaluating means evaluates the driving safety of the vehicle for each rotation of the tire according to the maximum value of the peak value of the spectrum of the time-series acceleration data in the analysis target time region. 6. The vehicle travel safety evaluation device according to claim 4 or 5, characterized in that: A storage means for storing a predetermined threshold value;
The evaluation unit reads the threshold value from the storage unit, compares the read threshold value with the peak value, and determines whether the vehicle is in a safe driving state according to the comparison result. The vehicle running safety evaluation device according to claim 1, wherein the determined result is output. The threshold value is a value of a cornering force generated in the tire, which is acquired in advance using a tire testing machine that measures at least one of a cornering force value and a lateral force value generated in the rolling tire. Or at least one of the values of the lateral force generated in the tire,
Predetermined based on a correspondence relationship between a peak value in a frequency range of 500 Hz to 1500 Hz of an acceleration spectrum at a predetermined position fixed to the tire that is generated while rolling in the tire testing machine. 8. The vehicle travel safety evaluation device according to claim 7, wherein For a vehicle having wheels equipped with tires, a method for evaluating traveling safety when the vehicle travels on a road surface,
When the vehicle travels on the road surface, the tire that is rolling is generated by receiving an external force from the road surface, the acceleration data of a predetermined position fixed to the tire is acquired in time series,
Obtaining a spectrum of the acceleration by frequency analysis of the time-series acceleration data;
Detecting a peak value in a frequency range of 500 Hz to 1500 Hz corresponding to a frequency of a squeal noise generated from the tire in the spectrum of the acceleration;
Evaluating the traveling safety of the vehicle according to the detected peak value, and a vehicle traveling safety evaluation method. In the step of obtaining the spectrum, the predetermined position passes through a portion corresponding to a ground contact region between the tire and a road surface in a time region corresponding to the time-series acceleration data, and then the ground contact is performed via a tire shaft. Extract the time domain to be analyzed until it reaches the position opposite to the center of the area,
The vehicle travel safety evaluation method according to claim 9, wherein a spectrum of the time-series acceleration data in the analysis target time domain is obtained as the acceleration spectrum.   The vehicle travel safety evaluation method according to claim 10, wherein in the step of obtaining the spectrum, the analysis target time region is extracted based on the acquired time-series acceleration data.

Images