JP6475954B2 - Tire pressure drop detection device, method and program - Google Patents

Description

  The present invention relates to a tire pressure drop detection device, method, and program. More particularly, the present invention relates to a tire pressure drop detection device, method, and program for detecting a tire pressure drop based on a torsional resonance frequency of a tire of a running vehicle.

  One of the factors that enable a car to travel safely is the tire air pressure. If the air pressure falls below an appropriate value, the steering stability and fuel consumption are deteriorated, which may cause tire bursts. For this reason, a tire pressure alarm system (TPMS) that detects a decrease in tire air pressure and issues an alarm to the driver to prompt appropriate measures is used to protect the environment and ensure the safety of the driver. It is an important technology.

  Conventional alarm devices can be classified into two types, a direct detection type and an indirect detection type. The direct detection type directly measures tire air pressure by incorporating a pressure sensor inside the tire wheel. While it is possible to detect a decrease in air pressure with high accuracy, there are technical and cost issues such as the need for a dedicated wheel and the problem of fault-tolerant performance in the actual environment.

  On the other hand, the indirect detection type is a method for estimating air pressure from tire rotation information, and can be subdivided into a dynamic load radius (DLR) method and a resonance frequency (RFM) method. Among them, the RFM method has been proposed as various technologies that can solve the problems in the DLR method (problems such as the inability to detect simultaneous reduction of four wheels because of the relative principle of wheel rotation speed). (For example, refer to Patent Documents 1 and 2).

  The RFM method in the inventions described in Patent Documents 1 and 2 uses the characteristic that the torsional resonance frequency of the tire is reduced by decompression, and estimates the torsional resonance frequency of the tire in time series from the rotation speed information or the rotation acceleration information of the tire. Thus, a decrease in the air pressure of the tire is detected.

  However, in a driving wheel of a vehicle, periodic noise may occur near the torsional resonance frequency of the tire depending on the vehicle speed, gear position, and the like. In this case, the resonance frequency estimated in time series by the AR model or the like is pulled by the periodic noise and becomes a value different from the original torsional resonance frequency of the tire. As a result, there is a risk of false alarms or unalarmed in the TPMS.

  Therefore, in order to eliminate the influence of such periodic noise, it has been proposed to take a difference between disturbances generated in the left and right wheels (see, for example, Non-Patent Document 1). In the tire pressure estimation method described in Non-Patent Document 1, the difference between the disturbances of the left and right wheels is taken in view of the fact that engine noise generated by the vehicle speed and gear position appears in the same phase in the left wheel and the right wheel.

That is, the disturbance of the left and right wheels respectively w _L, and w _R, the twist angle theta, the torsion spring constant of the tire and K, the attenuation constant is D, the wheel is subjected torque (left and right in-phase) and T _S, When the noise due to the road surface is _Td , the wheel speed disturbance of each of the left and right wheels can be expressed by the following equations (1) to (2).

Here, sequentially obtains the tire torsional spring constant _K L, and _{K R,} the damping coefficient _D L, and _{D R.} Since T _dL -T _dR is white noise, the influence on the estimation of the resonance frequency is small. Tire torsion spring constant _K L, and _{K R,} the damping coefficient _D L, _{D R} and, because the tire torsional resonance frequency there is a clear relationship, the tire torsional spring constant _K L, and _{K R,} the damping coefficient _D L, by obtaining a D _R, it is possible to estimate the resonance frequency of the tire, and the estimated resonance frequency, the tire is depressurized by comparing the resonance frequency of the tire in normal pressure obtained in advance It can be estimated whether or not.

JP 2010-023546 A JP 2010-023673 A

Koji Umeno, “Development of Tire Pressure Estimation Method Using Wheel Speed Sensor”, Toyota Central R & D Review, December 1997, Vol. 32, no. 4, p. 45-52

  However, since the lengths of the drive shafts are different on the left and right, even if the noise appears in the same phase in the wheel speeds of the left and right wheels, their amplitudes may differ from each other. In this case, even if the difference between the left and right wheels is taken as described above, the in-phase noise cannot be canceled, and as a result, the tire pressure cannot be estimated correctly.

  When the in-phase noise, that is, the torque applied to the wheels is different between the left and right wheels, the left and right wheel speed disturbances are expressed by the following formulas (3) to (4), and the difference between the left and right wheel speeds is expressed by the formula (5). The

Here, since T _sL -T _sR in the equation (5) has a large influence on the estimation, if this is a size that cannot be ignored, the resonance frequency cannot be estimated correctly.

  The present invention has been made in view of such circumstances, and a tire pressure drop detection device and method that can improve the estimation accuracy of tire pressure by eliminating the influence of noise appearing in the same phase on the left and right wheels. And to provide a program.

(1) A tire pressure drop detection device (hereinafter also simply referred to as “detection device”) according to a first aspect of the present invention includes a rotation speed information detection unit that detects rotation speed information of each wheel of a vehicle,
From the rotation speed information obtained by the rotation speed information detection unit, a resonance frequency estimation unit that estimates the torsional resonance frequency of the rotation speed information in time series,
A determination unit that determines a decrease in the air pressure of the tire mounted on each wheel based on the estimated torsional resonance frequency, and
The resonance frequency estimation unit is configured to obtain a difference between the rotational speed information of the left and right wheels to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference by the difference acquisition unit, the left and right wheels And a correction unit that multiplies the rotational speed information of the left wheel or the right wheel by a difference coefficient based on the amplitude of each noise appearing in the same phase.

(2) A detection device according to a second aspect of the present invention includes a rotation speed information detection unit that detects rotation speed information of each wheel of the vehicle,
From the rotational speed information obtained by the rotational speed information detection unit, a rotational acceleration information calculation unit that calculates rotational acceleration information of the wheel,
From the rotational acceleration information calculated by the rotational acceleration information calculation unit, a resonance frequency estimation unit that estimates the torsional resonance frequency of the rotational acceleration information in time series,
A determination unit that determines a decrease in the tire air pressure based on the estimated torsional resonance frequency, and
The resonance frequency estimation unit is configured to obtain a difference between rotational acceleration information of the left and right wheels in order to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when obtaining the difference by the difference acquisition unit, the left and right wheels And a correction unit that multiplies the rotational acceleration information of the left wheel or the right wheel by a difference coefficient based on the amplitude of each noise appearing in the same phase.

  In the detection apparatus of the present invention, when canceling noise appearing in the same phase on the left and right wheels of the vehicle, the difference coefficient based on the amplitude of the noise of the left and right wheels is multiplied by the rotational speed information or rotational acceleration information of the left or right wheel. Thereby, the noise appearing in the same phase on the left and right wheels of the vehicle can be canceled more reliably, and the torsional resonance frequency of the rotational speed information or rotational acceleration information estimated in time series from the rotational speed information or rotational acceleration information can be reduced. As a result, the estimation accuracy of the tire pressure can be improved.

(3) A tire pressure drop detecting method (hereinafter also simply referred to as “detecting method”) according to a third aspect of the present invention includes a rotational speed information detecting step of detecting rotational speed information of each wheel of the vehicle,
From the rotational speed information obtained in the rotational speed information detection step, a resonance frequency estimation step for time-series estimation of the torsional resonance frequency of the rotational speed information;
A determination step of determining a decrease in the air pressure of the tire mounted on each wheel based on the estimated torsional resonance frequency, and
The resonance frequency estimation step includes a difference acquisition step for obtaining a difference in rotational speed information between the left and right wheels in order to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference in the difference acquisition step, the left and right wheels Includes a correction step of multiplying the rotational speed information of the left wheel or the right wheel by a difference coefficient based on the amplitude of each noise appearing in phase.

(4) A detection method according to a fourth aspect of the present invention includes a rotation speed information detection step of detecting rotation speed information of each wheel of the vehicle;
From the rotational speed information obtained in the rotational speed information detection step, a rotational acceleration information calculation step of calculating rotational acceleration information of the wheel,
From the rotational acceleration information obtained in the rotational acceleration information calculation step, a resonance frequency estimation step for time-series estimating the torsional resonance frequency of the rotational acceleration information;
A determination step of determining a decrease in the air pressure of the tire mounted on each wheel based on the estimated torsional resonance frequency, and
The resonance frequency estimation step includes a difference acquisition step of obtaining a difference between rotational acceleration information of the left and right wheels in order to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference in the difference acquisition step, Includes a correction step of multiplying the rotational acceleration information of the left wheel or the right wheel by a difference coefficient based on the amplitude of each noise appearing in phase.

  In the detection method of the present invention, when canceling the noise appearing in the same phase on the left and right wheels of the vehicle, the difference coefficient based on the amplitude of the noise of the left and right wheels is multiplied by the rotational speed information or rotational acceleration information of the left wheel or right wheel. Thereby, the noise appearing in the same phase on the left and right wheels of the vehicle can be canceled more reliably, and the torsional resonance frequency of the rotational speed information or rotational acceleration information estimated in time series from the rotational speed information or rotational acceleration information can be reduced. As a result, the estimation accuracy of the tire pressure can be improved.

(5) A tire air pressure drop detection program (hereinafter also simply referred to as “program”) according to a fifth aspect of the present invention detects a tire air pressure drop based on a resonance frequency of a tire of a running vehicle. A rotational frequency information obtained by a rotational speed information detection unit that detects rotational speed information of each wheel of the vehicle, and a resonance frequency estimation unit that estimates a torsional resonance frequency of the rotational speed information in time series, and Function as a determination unit for determining a decrease in the air pressure of the tire mounted on each wheel based on the twist resonance frequency,
The resonance frequency estimation unit is configured to obtain a difference between the rotational speed information of the left and right wheels to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference by the difference acquisition unit, the left and right wheels And a correction unit that multiplies the rotational speed information of the left wheel or the right wheel by a difference coefficient based on the amplitude of each noise appearing in the same phase.

(6) A program according to a sixth aspect of the present invention detects a rotational speed information of each wheel of a vehicle and a computer for detecting a decrease in air pressure of the tire based on a resonance frequency of a tire of a running vehicle. A rotational acceleration information calculation unit that calculates rotational acceleration information of the wheel from the rotational speed information obtained by the rotational speed information detection unit, and a torsional resonance of the rotational acceleration information from the rotational acceleration information calculated by the rotational acceleration information calculation unit Resonance frequency estimation unit that estimates frequency in time series, and function as a determination unit that determines a decrease in tire air pressure based on the estimated torsional resonance frequency,
The resonance frequency estimation unit is configured to obtain a difference between rotational acceleration information of the left and right wheels in order to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when obtaining the difference by the difference acquisition unit, the left and right wheels And a correction unit that multiplies the rotational acceleration information of the left wheel or the right wheel by a difference coefficient based on the amplitude of each noise appearing in the same phase.

  According to the tire pressure drop detecting device, method, and program of the present invention, it is possible to eliminate the influence of noise appearing in the same phase on the left and right wheels and improve the estimation accuracy of the tire pressure.

It is a block diagram which shows one Embodiment of the detection apparatus of this invention. It is a block diagram which shows the electrical structure of the detection apparatus shown by FIG. It is a figure showing the FFT spectrum which multiplied the wheel speed gain of FL wheel and FR wheel, and the wheel speed gain of FR wheel spectrum by 1.2 times. After the difference between the front wheel speed of the left and right front wheels after the FFT spectrum of the signal after the wheel speed of the left and right front wheels is subtracted without multiplying the wheel speed of the FR wheel by a constant, It is a figure showing the FFT spectrum about the signal of. It is a figure which shows the tire resonant frequency estimated value calculated | required by making the wheel speed of a right-and-left wheel differed without multiplying the wheel speed of FR wheel. It is a figure which shows the tire resonant frequency estimated value calculated | required by subtracting the wheel speed of a right-and-left wheel after multiplying the wheel speed of FR wheel 1.2 times.

  Hereinafter, embodiments of the detection apparatus, method, and program of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included.

FIG. 1 is a block diagram showing a detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an electrical configuration of the detection device shown in FIG.
As shown in FIG. 1, the detection device according to an embodiment of the present invention includes a left front wheel (FL), a right front wheel (FR), a left rear wheel (RL), and a right rear wheel (RR) of a four-wheel vehicle. In order to detect rotation speed information, a normal wheel speed detection unit (rotation speed information detection unit) 1 provided in association with each wheel is provided.

  The wheel speed detector 1 generates a rotation pulse by using an electromagnetic pickup or the like, and uses a wheel speed sensor for measuring a rotation angular speed and a wheel speed from the number of pulses, or rotation like a dynamo. An angular velocity sensor including that for measuring the rotational angular velocity and the wheel speed from this voltage can be used. The output of the wheel speed detector 1 is given to a control unit 2 which is a computer such as ABS. The control unit 2 includes, for example, a liquid crystal display element for displaying that the tire is depressurized, a display 3 composed of a plasma display element or a CRT, an initialization button 4 that can be operated by a driver, An alarm device 5 is connected to notify the driver that the tire pressure is reduced.

  As shown in FIG. 2, the control unit 2 stores an I / O interface 2a necessary for passing signals to and from an external device, a CPU 2b that functions as a center of arithmetic processing, and a control operation program for the CPU 2b. The ROM 2c and the RAM 2d from which data is temporarily written or the written data is read when the CPU 2b performs a control operation.

  The wheel speed detection unit 1 outputs a pulse signal corresponding to the number of rotations of the tire (hereinafter also referred to as “wheel speed pulse”). Then, by re-sampling the wheel speed pulse at a predetermined cycle ΔT (sec), for example, ΔT = 0.005 seconds, time-series data of the wheel speed signal can be obtained. Since the resonance frequency of the torsional direction of the tire of interest appears in the vicinity of several tens of Hz, it is necessary to set the sampling period so that it is included in the Nyquist frequency.

  The detection device according to the present embodiment estimates the torsional resonance frequency of the rotation speed information from the wheel speed detection section (rotation speed information detection section) 1 and the rotation speed information obtained by the wheel speed detection section 1 in time series. A resonance frequency estimation unit and a determination unit that determines a decrease in air pressure of the tire mounted on each wheel based on the estimated torsional resonance frequency are mainly configured. The resonance frequency estimation unit is configured to obtain a difference between the rotational speed information of the left and right wheels to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference by the difference acquisition unit, the left and right wheels And a correction unit that multiplies the rotational speed information of the left wheel or the right wheel by a difference coefficient based on the amplitude of each noise appearing in the same phase. The program according to the present embodiment is installed in the control unit 2, and causes the control unit 2 to function as a resonance frequency estimation unit including a difference acquisition unit and a correction unit, and a determination unit.

For the torsional resonance frequency, for example, rotational speed information or rotational acceleration information is subjected to time series analysis based on a second-order autoregressive (AR) model, or disclosed in, for example, Japanese Patent Application Laid-Open No. 2011-102077. The estimation is performed by estimating each parameter as a time-series signal as a time-series signal, and by estimating each parameter as a linear model of the following formulas (6) to (7) (n is an integer of 3 or more). Can do. In Expressions (6) to (7), y (t) is a time series signal of wheel rotational acceleration, n is a model order (an integer of 3 or more), a _i is each parameter, y ′ (t) is a rotational component, w (T) is a disturbance (vibration component).

  Then, when the obtained torsional resonance frequency becomes lower than a reference torsional resonance frequency calculated at initialization, for example, and stored in the RAM 2d by exceeding a predetermined threshold (for example, 2 Hz), the tire is depressurized. The alarm device 5 issues an alarm.

  In this embodiment, when determining a decrease in tire air pressure by paying attention to a change in the torsional resonance frequency, periodic noise is generated in the vicinity of the torsional resonance frequency of the tire depending on the vehicle speed, gear position, and the like in the drive wheels of the vehicle. In view of the possibility of false alarms and unwarned alarms, the difference between the wheel speeds of the left and right wheels is taken to cancel the periodic noise, thereby eliminating the influence of the periodic noise even when the amplitudes of the noises of the left and right wheels are different. Is.

  That is, noise generated by the vehicle speed, gear position, and the like in the driving wheels of the vehicle has the same phase, and therefore, normally, the noise can be canceled by taking the difference between the left and right wheels. However, under a situation where the amplitudes of the common-mode noise appearing at the wheel speeds of the left and right wheels are different from each other due to the difference in the length of the drive shaft between the left and right, the noise cannot be canceled by simply taking the difference. For example, in the example shown in FIG. 3, the peak height (proportional to the amplitude of noise) of the wheel speed spectrum near 42 Hz is different between the FL wheel and the FR wheel. This peak frequency is considered to be engine noise because it is a frequency that matches the explosion vibration of the engine. Such engine noise is the same phase noise on the left and right wheels. In FIG. 3, the peak in the vicinity of 50 Hz is the torsional resonance frequency of the tire, which is a resonance frequency correlated with the tire air pressure.

  Here, as shown in FIG. 4, simply by taking the difference between the left and right wheels, the peak height of the wheel speed spectrum near 42 Hz is different between the FL wheel and the FR wheel as described above. As shown in the thick solid line labeled “difference between left and right front wheel speeds without multiplying by a constant”, noise remains in the vicinity of 42 Hz, and the estimated value of the tire torsional resonance frequency is correctly obtained as shown in FIG. I can't. The results shown in FIGS. 3 to 6 are based on a running test in a front engine / front drive FF vehicle. 3 to 4 are based on data obtained when the gear shift position is “5th gear” in a manual vehicle and travels at 70 kph. FIGS. 5 to 6 are for “45 kph” except “4th gear” and 45 kph. The speed is based on data obtained when traveling at “5th speed”.

On the other hand, in the present embodiment, the difference coefficient of each noise appearing in phase on the left and right wheels is obtained in advance, and the difference between the amplitudes of the in-phase noise of the left and right wheels is multiplied by the difference coefficient on the left wheel or the right wheel. Is eliminated.
The differential coefficient, for example, the amplitude of engine noise that appears to the left and right wheels respectively B _L, and B _R, the ω is the angular frequency of the engine noise, the time of t, and the engine noise that appears to the left wheel and B _L sin .omega.t, right wheel the engine noise when the _B R sin .omega.t appearing in _a coefficient expressed by _B L / B _R.

  The difference coefficient can be obtained by, for example, outputting a frequency spectrum for each of the left and right wheels by FFT in an experimental run in the vehicle production stage (see FIG. 3) and calculating a ratio from the peak value of the spectrum in the output diagram. The obtained ratio is stored as a predetermined value in a control unit mounted on the vehicle. On the other hand, if the control unit has sufficient computing resources, the difference coefficient may be obtained each time in the initialization stage after the tire is replaced or the tire pressure is adjusted. In this case, even if a tire other than the standard tire is mounted, the difference coefficient corresponding to the tire can be obtained. Furthermore, assuming that there is a possibility that the difference coefficient may change during traveling, the difference coefficient can be obtained at regular intervals.

In the example shown in FIG. 3, the wheel speed gain of the FL wheel is approximately 1.2 times the wheel speed gain of the FR wheel. Therefore, in this case, the difference coefficient is 1.2, and by taking the difference between the left and right wheels after multiplying the wheel speed gain of the FR wheel by 1.2, as shown by the thin line in FIG. In-phase noise can be canceled (refer to “difference between front and rear wheel speeds after FR wheel is multiplied by 1.2”). The obtained torsional resonance frequency of the tire was a level at which the change due to the speed could be ignored as shown in FIG.
5 to 6, it can be seen that according to the present embodiment, the influence of in-phase noise on the left and right wheels having different amplitudes can be reduced, and the estimation accuracy of the torsional resonance frequency of the tire can be improved.

Next, the operation of the detection apparatus according to this embodiment or the detection method according to this embodiment will be described.
(1) First, a wheel rotation signal is detected by a wheel speed detector.
(2) Next, the control unit 2 re-samples the wheel rotation signal according to a predetermined period to obtain a wheel speed signal. The period must be determined in consideration of the resonance frequency in the torsional direction of the tire of interest. Specifically, the sampling period is preferably set to a sampling period of 100 Hz or more because the resonance frequency in the torsional direction of interest appears in the vicinity of several tens of Hz.

(3) Next, if the disturbance included in the left and right wheel speeds is wL (t), wR (t), and a1, a2,..., An, and b1, b2,.
wL (t) = a1 (t−1) + a2 (t−2) +... + an (t−n)
wR (t) = b1 (t−1) + b2 (t−2) +... + bn (t−n)
It is.
a1, a2,..., an, and b1, b2,..., bn are tire torsion spring constant K, damping constant D, wheel received torque (right and left in-phase) Ts, and road surface noise Td. It is.

(4) Here, in order to eliminate the influence of engine noise, a difference is taken as wL (t) −wR (t). For example, when FL = 1.2 × FR as in the example shown in FIG. Since the difference coefficient between the left and right wheels is “1.2”,
wL (t) −1.2 wR (t) = a1 (t−1) + a2 (t−2) +... an (t−n) −1.2 {b1 (t−1) + b2 (t−2) ) +... + Bn (t-n)}, a1, a2,..., An and b1, b2,. And estimate the resonant frequency of each of the FR wheels.
(5) Then, the estimated resonance frequency is compared with the reference resonance frequency, and when the difference is larger than a predetermined value, it is determined that the tire is depressurized, and an alarm is issued.

[Example]
Next, examples of the detection method of the present invention will be described, but the present invention is not limited to such examples.
[Example 1]
An FF (front engine, front drive) vehicle was run on a test course (circumference circuit), and the wheel speeds of the two front wheels were measured. A resonance peak between 33 Hz and 67 Hz was estimated by a second order approximation with a sampling time of 3.75 ms by a sequential time series estimation method.
In taking the difference between the left and right wheels, the difference between the left and right wheels was taken after multiplying the wheel speed gain of the FR wheel by a difference coefficient (1.2) obtained in advance.

[Comparative Example 1]
The resonance peak was estimated in the same manner as in Example 1 except that the difference between the left and right wheels was taken without using the difference coefficient.
In Example 1, the variation in the estimated resonance frequency when the speed condition was changed was smaller than that in Comparative Example 1.

[Other variations]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims.
For example, in the embodiment described above, the torsional resonance frequency of the wheel speed that is the rotational speed information is obtained by time series estimation, but instead of the wheel speed, the torsional resonance frequency of the wheel acceleration that is the rotational acceleration information is estimated in time series. Can also be obtained. In this case, the rotation acceleration information is calculated from the rotation speed information obtained by the rotation speed information detection unit by the control unit that functions as the rotation acceleration information calculation unit. Then, the torsional resonance frequency of the rotation acceleration information is time-series estimated from the calculated rotation acceleration information by a control unit that functions as a resonance frequency estimation unit. Since the rotational acceleration information has less change than the rotational speed information, it is desirable that the rotational acceleration information be time-series data from the viewpoint of improving calculation accuracy.

DESCRIPTION OF SYMBOLS 1 Wheel speed detection part 2 Control unit 2a Interface 2b CPU
2c ROM
2d RAM
3 Display 4 Initialization button 5 Alarm

Claims (6)

A rotational speed information detector for detecting rotational speed information of each wheel of the vehicle;
From the rotation speed information obtained by the rotation speed information detection unit, a resonance frequency estimation unit that estimates the torsional resonance frequency of the rotation speed information in time series,
A determination unit that determines a decrease in the air pressure of the tire mounted on each wheel based on the estimated torsional resonance frequency, and
The resonance frequency estimation unit is configured to obtain a difference between the rotational speed information of the left and right wheels to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference by the difference acquisition unit, the left and right wheels A correction unit that multiplies the rotational speed information of the left wheel or the right wheel by a difference coefficient obtained based on a difference in amplitude of each noise appearing in the same phase ,
The noise is engine noise, the difference coefficients, respectively B _L amplitudes of engine noise that appears to the left and right _wheels, and B _R, the ω is the angular frequency of the engine noise, the time of t, the engine noise that appears to the left wheel and B _L sin .omega.t, when the engine noise that appears to the right wheel and _{B R sinωt, B L / B} R Ru der, tire pressure drop detecting device. A rotational speed information detector for detecting rotational speed information of each wheel of the vehicle;
From the rotational speed information obtained by the rotational speed information detection unit, a rotational acceleration information calculation unit that calculates rotational acceleration information of the wheel,
From the rotational acceleration information calculated by the rotational acceleration information calculation unit, a resonance frequency estimation unit that estimates the torsional resonance frequency of the rotational acceleration information in time series,
A determination unit that determines a decrease in the tire air pressure based on the estimated torsional resonance frequency, and
The resonance frequency estimation unit is configured to obtain a difference between rotational acceleration information of the left and right wheels in order to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when obtaining the difference by the difference acquisition unit, the left and right wheels A correction unit that multiplies the rotational acceleration information of the left wheel or the right wheel by a difference coefficient obtained based on the difference in amplitude of each noise appearing in the same phase ,
The noise is engine noise, the difference coefficients, respectively B _L amplitudes of engine noise that appears to the left and right _wheels, and B _R, the ω is the angular frequency of the engine noise, the time of t, the engine noise that appears to the left wheel and B _L sin .omega.t, when the engine noise that appears to the right wheel and _{B R sinωt, B L / B} R Ru der, tire pressure drop detecting device. A rotational speed information detecting step for detecting rotational speed information of each wheel of the vehicle;
From the rotational speed information obtained in the rotational speed information detection step, a resonance frequency estimation step for time-series estimation of the torsional resonance frequency of the rotational speed information;
A determination step of determining a decrease in the air pressure of the tire mounted on each wheel based on the estimated torsional resonance frequency, and
The resonance frequency estimation step includes a difference acquisition step for obtaining a difference in rotational speed information between the left and right wheels in order to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference in the difference acquisition step, the left and right wheels look including a correction step of multiplying the difference coefficient obtained based on the difference in amplitude of the noise appearing in phase with the rotational speed information of the left wheel or the right wheel,
The noise is engine noise, the difference coefficients, respectively B _L amplitudes of engine noise that appears to the left and right _wheels, and B _R, the ω is the angular frequency of the engine noise, the time of t, the engine noise that appears to the left wheel and B _L sin .omega.t, when the engine noise that appears to the right wheel and _B R sin _.omega.t, a _B L / B _R, a tire pressure drop detecting method. A rotational speed information detecting step for detecting rotational speed information of each wheel of the vehicle;
From the rotational speed information obtained in the rotational speed information detection step, a rotational acceleration information calculation step of calculating rotational acceleration information of the wheel,
From the rotational acceleration information obtained in the rotational acceleration information calculation step, a resonance frequency estimation step for time-series estimating the torsional resonance frequency of the rotational acceleration information;
A determination step of determining a decrease in the air pressure of the tire mounted on each wheel based on the estimated torsional resonance frequency, and
The resonance frequency estimation step includes a difference acquisition step of obtaining a difference between rotational acceleration information of the left and right wheels in order to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference in the difference acquisition step, the left and right wheels look including a correction step of multiplying the difference coefficient obtained based on the difference in amplitude of the noise appearing in phase with the rotation acceleration information left wheel or the right wheel,
The noise is engine noise, the difference coefficients, respectively B _L amplitudes of engine noise that appears to the left and right _wheels, and B _R, the ω is the angular frequency of the engine noise, the time of t, the engine noise that appears to the left wheel and B _L sin .omega.t, when the engine noise that appears to the right wheel and _B R sin _.omega.t, a _B L / B _R, a tire pressure drop detecting method. Based on the rotational speed information obtained by the rotational speed information detecting unit for detecting rotational speed information of each wheel of the vehicle, a computer is used to detect a decrease in air pressure of the tire based on the resonance frequency of the tire of the traveling vehicle. Resonance frequency estimation unit for time series estimation of the torsional resonance frequency of the rotation speed information, and function as a determination unit for determining a decrease in the air pressure of the tire mounted on each wheel based on the estimated torsional resonance frequency,
The resonance frequency estimation unit is configured to obtain a difference between the rotational speed information of the left and right wheels to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when acquiring the difference by the difference acquisition unit, the left and right wheels A correction unit that multiplies the rotational speed information of the left wheel or the right wheel by a difference coefficient obtained based on a difference in amplitude of each noise appearing in the same phase ,
The noise is engine noise, the difference coefficients, respectively B _L amplitudes of engine noise that appears to the left and right _wheels, and B _R, the ω is the angular frequency of the engine noise, the time of t, the engine noise that appears to the left wheel and B _L sin .omega.t, when the engine noise that appears to the right wheel and _{B R sinωt, B L / B} R Ru der, tire pressure drop detecting program. From the rotational speed information obtained by the rotational speed information detecting unit that detects the rotational speed information of each wheel of the vehicle, the computer detects the decrease in air pressure of the tire based on the resonance frequency of the tire of the running vehicle. A rotational acceleration information calculating unit for calculating the rotational acceleration information of the rotational acceleration information, a resonance frequency estimating unit for estimating the torsional resonance frequency of the rotational acceleration information in time series from the rotational acceleration information calculated by the rotational acceleration information calculating unit, and Function as a determination unit for determining a decrease in the tire air pressure based on the twist resonance frequency,
The resonance frequency estimation unit is configured to obtain a difference between rotational acceleration information of the left and right wheels in order to eliminate the influence of noise appearing in the same phase on the left and right wheels, and when obtaining the difference by the difference acquisition unit, the left and right wheels A correction unit that multiplies the rotational acceleration information of the left wheel or the right wheel by a difference coefficient obtained based on the difference in amplitude of each noise appearing in the same phase ,
The noise is engine noise, the difference coefficients, respectively B _L amplitudes of engine noise that appears to the left and right _wheels, and B _R, the ω is the angular frequency of the engine noise, the time of t, the engine noise that appears to the left wheel and B _L sin .omega.t, when the engine noise that appears to the right wheel and _B R sin _.omega.t, a _B L / B _R, a tire pressure drop detecting program.