JP2006130941A - Tire discrimination device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire discrimination device capable of discriminating that an attached tire is a summer tire or a winter tire in a four-wheel drive vehicle. <P>SOLUTION: The tire discrimination device is provided with a rotation speed detection means for detecting rotation speed of a wheel attached to the vehicle; a wheel speed operation means for calculating an average wheel speed of a driving wheel from the rotation speed; an acceleration operation means for operating speed and acceleration of the vehicle from a satellite signal received by GPS receiver mounted on the vehicle; a slip ratio operation means for operating a slip ratio of the driving wheel from the driving wheel average wheel speed and the vehicle speed; and a tire discrimination means for discriminating the tire attached at present based on the front and rear rigidity of the tire obtained from primary regression coefficient of a relationship of the acceleration of the vehicle and the slip ratio of the driving wheel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tire identification apparatus and method. More particularly, the present invention relates to a tire identification apparatus and method used for identifying a tire driving stiffness level and applying it to vehicle control, or for enhancing vehicle safety.

  In consideration of drainage and the like, the tire has carved longitudinal grooves and lateral grooves, and therefore a rubber block surrounded by these grooves is formed. If this rubber block is large, it is difficult to shear and deform in the front / rear and left / right directions, and the rigidity is large. Generally, a tire having a tread pattern composed of a large block is called a tire having a large pattern rigidity. Further, the pattern rigidity greatly depends on the blending of rubber. Generally, summer tires have high pattern rigidity, and winter tires have low pattern rigidity.

  The size of the pattern stiffness has a significant effect on the cornering power and cornering force, as well as the slip rate, so devices that improve vehicle performance and safety based on tire rotation information, such as ABS (anti-block braking system) ), TCS (Traction Control System) or so-called indirect tire pressure drop warning device, etc., it is important to know the pattern stiffness of the tire to estimate the vehicle behavior based on tire rotation information It is.

  In addition, the indirect air pressure drop alarm device that detects a decrease in the tire internal pressure from the change in the rotation speed of the tire reduces the dynamic load radius of the tire when the tire air pressure decreases. For example, Patent Document 1 proposes a method of detecting a decrease in internal pressure from a relative difference in tire rotation speed. In this case, since the rotational speed of the tire is affected by turning, acceleration / deceleration, load, vehicle speed, and the like, various devices have been made to remove these influences. In addition, these tire pressure drop warning devices are installed in new cars and tune vehicle factors such as correction factors when turning according to the tires, but the summer tires from winter tires or winter tires to summer tires with greatly different specifications If it is exchanged, the estimation of the behavior of the vehicle is far from the initial tuning, and there is a possibility that accurate information provided to the driver cannot be secured. Therefore, there is a method in which initial tuning is performed for summer tires and winter tires, and the average value thereof is used as a vehicle factor. However, even in this case, the accuracy of internal pressure detection is reduced.

  Therefore, it is possible to identify how big the pattern stiffness is, such as whether the currently installed tire is a summer tire, a winter tire, or a tire with worn tread, and the vehicle factor is automatically set accordingly. It can be said that the rewriting method is optimal.

  For example, Patent Document 2 describes a method for discriminating summer tires from winter tires only for vehicles equipped with a differential limiting device (LSD).

  Even if a differential limiting device is not installed, as a method for distinguishing between a summer tire and a winter tire, a method of measuring a rising slope (driving stiffness) of a tire μ-s curve, a vehicle acceleration, There is a method of determining tire stiffness by comparing a linear regression coefficient of the relationship between the tire slip ratio and the tire with a given value (Patent Document 3).

  In addition, the type of tire is determined by comparing the ratio of the rotational speed of the front wheels and the rotational speed of the rear wheels with a vehicle speed-front-rear wheel ratio function created based on data measured in advance for each tire type. Patent Document 5 is known as a method for doing this (Patent Document 4) and a method for specifying the tire type by the driver.

JP 7-149119 A JP 2000-79812 A JP 2002-181669 A JP-A-9-188114 JP 2004-98877 A

  If the tire pressure alarm device can automatically identify whether the tire that is automatically mounted is a summer tire or a winter tire, the detection accuracy can be greatly improved, but the tire is identified from the rising slope of the tire μ-s curve. In this case, since the rising gradient differs depending not only on the pattern rigidity of the tread but also on the friction coefficient of the road surface, it is difficult to apply it to tire identification unless the road surface to be measured is limited.

  The method of Patent Document 2 is limited to vehicles equipped with a differential limiting device. The method of Patent Document 3 requires driven wheels to calculate the vehicle speed and cannot be applied to a four-wheel drive vehicle.

  In view of the above circumstances, an object of the present invention is to provide a tire identification device and method that can identify whether a tire mounted on a four-wheel drive vehicle is a summer tire or a winter tire.

  A tire identification device according to the present invention is mounted on a vehicle, a rotation speed detection unit that detects a rotation speed of a wheel mounted on the vehicle, a wheel speed calculation unit that calculates an average wheel speed of a drive wheel from the rotation speed, and the vehicle. Acceleration calculation means for calculating the speed and acceleration of the vehicle from satellite signals received by the GPS receiver, slip ratio calculation means for calculating the slip ratio of the drive wheel from the average wheel speed of the drive wheel and the vehicle speed, Tire identifying means for identifying a currently mounted tire based on a longitudinal stiffness of the tire obtained from a first-order regression coefficient of the relationship between the acceleration of the vehicle and the slip ratio of the driving wheel. To do.

  The tire identification method of the present invention includes a step of detecting a rotational speed of a wheel mounted on a vehicle, a step of calculating an average wheel speed of driving wheels from the rotational speed, and a GPS receiver mounted on the vehicle. Calculating vehicle speed and vehicle acceleration from the received satellite signal; calculating drive wheel average wheel speed and vehicle speed slip ratio; and vehicle acceleration and drive wheel slip. And a step of identifying a currently mounted tire on the basis of the longitudinal rigidity of the tire obtained from a first-order regression coefficient in relation to the rate.

  Further, the tire identification program of the present invention includes a computer for identifying tires mounted on a vehicle, wheel speed calculation means for calculating an average wheel speed of driving wheels from the rotational speed of wheels mounted on the vehicle, Acceleration calculation means for calculating the speed and acceleration of the vehicle from a satellite signal received by a GPS receiver mounted on the vehicle, and a slip ratio calculation for calculating a slip ratio of the driving wheel from the average wheel speed and the vehicle speed. And a tire identification means for identifying a currently mounted tire based on a longitudinal stiffness of the tire obtained from a linear regression coefficient of a relationship between the acceleration of the vehicle and the slip ratio of the drive wheel. And

  In the present invention, the wheel speed is the rotational angular speed of the wheel × the dynamic load radius of the tire.

  According to the present invention, it is possible to determine the type of tires worn and whether or not they are worn even in a four-wheel drive vehicle from the primary regression coefficient of the relationship between the acceleration of the vehicle and the slip ratio of the drive wheels. . In the example described later, in Subaru Legacy, the primary regression coefficient of the slip ratio with respect to the vehicle acceleration is 0.0282 in the summer tire, and the primary regression coefficient in the winter tire (studless tire) is 0.0761. Thus, the tire type could be accurately determined.

  As a result of determining the type of tire mounted on the vehicle, more accurate vehicle control can be performed by setting the correct tire stiffness in the ABS device or TRC device. In the case of a tire with a high degree of wear, the driver can be warned and tire replacement can be encouraged.

  According to the present invention, even in a vehicle that does not have driven wheels such as a four-wheel drive vehicle, whether the mounted tire is a low rigidity tire such as a studless tire or a relatively high rigidity tire such as a summer tire. The tire can be identified by the difference in the rigidity of the tire, such as whether the tire is a tire having very high rigidity due to wear of the tread. Since tires can be identified even in a four-wheel drive vehicle, differences in tire stiffness can be automatically reflected in vehicle control. In addition, in the air pressure reduction alarm device that uses the tire rotation speed for determination of pressure reduction, the accuracy of detecting the pressure reduction of the tire can be improved.

  Hereinafter, a tire identification device and method according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an embodiment of a tire identification device of the present invention, and FIG. 2 is a block diagram showing an electrical configuration of the tire identification device in FIG.

  As shown in FIG. 1, the tire identification device according to one embodiment of the present invention is a rotation that periodically detects the rotational speeds of the wheel tires provided in the tires FL, FR, RL, and RR of a four-wheel vehicle. A wheel speed sensor 1 serving as speed detection means is provided, and the output of the wheel speed sensor 1 is transmitted to a control unit 2 such as ABS. A satellite signal is transmitted from the GPS receiver 4 to the control unit 2. In addition, you may provide the initialization switch 3 operated by a driver | operator when changing a tire.

  As the wheel speed sensor 1, a sensor that generates a rotation pulse by using an electromagnetic pickup or the like and measures the rotation speed from the number of pulses can be used.

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

  In the present embodiment, the control unit 2 receives the wheel speed calculation means for calculating the average wheel speed of the drive wheel from the measured value by the wheel speed sensor 1 and the GPS receiver 4 mounted on the vehicle. Acceleration calculating means for calculating the speed and acceleration of the vehicle from satellite signals, mileage calculating means for calculating the mileage of the vehicle, and calculating a slip ratio of the driving wheel from the average driving wheel speed and the vehicle speed. Slip ratio calculating means, moving average calculating means for moving and averaging the acceleration and slip ratio of the vehicle, and moving averaged vehicle acceleration and slip ratio data until the calculated travel distance reaches a predetermined distance And a regression coefficient calculation means for obtaining a first-order regression coefficient and a correlation coefficient of acceleration and slip ratio, and a vehicle acceleration and a drive wheel slit. Based on the longitudinal stiffness of the tire obtained from the primary regression coefficient of the relationship between flop rate, and a tire identification means for identifying a tire that is currently mounted. In the present embodiment, the vehicle averaged acceleration and slip ratio data until the travel distance calculated by the speed calculation means for calculating the vehicle speed reaches a predetermined distance is accumulated and calculated, and the vehicle Although obtaining the primary regression coefficient and correlation coefficient of acceleration and driving wheel slip ratio will be described, the present invention is not limited to this, and instead of the travel distance, accumulation time or accumulated data is used. The linear regression coefficient and the correlation coefficient between the moving average vehicle acceleration and the slip ratio can also be obtained by using the number or the like. In this case, in place of the travel distance calculating means, there is provided an accumulated number calculating means for calculating the accumulated time or the number of accumulated data, and the acceleration and slip of the vehicle averaged using the accumulated time or the accumulated data number. A calculation means for obtaining a linear regression coefficient and a correlation coefficient with the rate is provided.

  Generally, a winter tire is a tire whose tread pattern or material is changed so that it can run on a snowy road. A tire having a display such as “SEASON”, and a summer tire are tires having no such display in the sidewall portion, unlike a winter tire. In this specification, a summer tire and a winter tire are used. This difference includes not only the presence / absence of such display but also the difference in the pattern rigidity of the tread. That is, a tire having a large pattern rigidity that affects vehicle control and tire pressure detection accuracy is a summer tire, and a tire having a small pattern rigidity is a winter tire.

  In the present embodiment, the rotational speed of the four-wheel tire is detected in 0.1 seconds or less, preferably 0.05 seconds or less. The vehicle speed and mileage are calculated from the satellite signal of the GPS receiver. The vehicle speed can be calculated as the rate of change from the position information of the GPS receiver. Alternatively, the vehicle speed may be calculated from the Doppler shift frequency of the GPS received radio wave. In general, calculating the velocity from the Doppler shift frequency is more accurate than calculating the velocity from the position information. Vehicle acceleration can be calculated as the rate of change of vehicle speed. Although the acceleration of the vehicle can be measured by an acceleration sensor, it is preferable from the viewpoint of cost to differentiate and calculate the vehicle speed. The slip ratio can be calculated from, for example, (wheel speed / vehicle speed-1).

  Then, the acceleration and slip ratio of the vehicle are obtained by moving average at each sampling time as an average value of data for a fixed time, for example, data of at least 0.1 second, and this moving average value (a fixed number of data) Slip rate and vehicle acceleration).

  Further, the vehicle-accelerated vehicle acceleration and slip ratio data are accumulated until the travel distance reaches a predetermined distance, and the first-order regression between the slip ratio and the vehicle acceleration is performed using the accumulated data. Find coefficients and correlation coefficients.

  Hereinafter, the operation of the tire identification device according to the present embodiment will be described along procedures (a) to (h).

(a) The wheel speeds (V1 _n , V2 _n , V3 _n , V4 _n ) are calculated from the rotational speeds of the four-wheel tires FL, FR, RL and RR of the vehicle. Here, the subscript n represents the order of the time series.

For example, the wheel speed data at a certain point of each wheel tire FL, FR, RL, RR of the vehicle obtained from a sensor such as an ABS sensor is set as wheel speeds V1 _n , V2 _n , V3 _n , V4 _n .

(b) Next, average wheel speeds (Vf _n , Vd _n ) of the driven wheels and the drive wheels are calculated.
For front wheel drive, wherein the average wheel speed Vf _n of the following wheels and the driving wheels at a certain time, the Vd _n of the following (1), obtained by (2).
Vf _n = (V3 _n + V4 _n ) / 2 (1)
Vd _n = (V1 _n + V2 _n ) / 2 (2)

In the case of four-wheel drive, only the average wheel speed of the drive wheels is calculated by the following equation.
_{Vd n = (V1 n + V2} n + V3 n + V4 n) / 4 ··· (3)

(c) Next, the mileage per unit time of the vehicle is calculated by the following equation (4).
DIST = Vn × Δt (4)
Here, Δt is a time interval (sampling time) between the vehicle speeds V _n and V _n−1 calculated from the satellite signal. Alternatively, the travel distance may be obtained by integrating the change (distance) of the GPS position information.

(d) Next, the acceleration Af _n of the vehicle is calculated.
From the vehicle speed V _n and the preceding vehicle speed V _n−1 , the acceleration Af _{n of} the vehicle in units of gravitational acceleration is obtained by the following equation (5).
Af _n = (V _n −V _n−1 ) / Δt / g (5)
Here, Δt is the time interval (sampling period) between the wheel speeds Vf _n and Vf _n−1 calculated from the wheel speed data, and g is the gravitational acceleration. The sampling period needs to be 0.1 second or less in order to reduce the variation in data and to determine in a short time. More preferably, it is 0.05 second or less.

(e) Next, the slip ratio is calculated according to the value of the acceleration Af _n of the vehicle.
First, in the acceleration state (Af _n > 0), the driving wheel locks and the vehicle slips (Vd _n = 0, V _n ≠ 0) or in the deceleration state (Af _n <0), the vehicle stops. Assuming that the drive wheels cannot cause wheel spin (V _n = 0, Vd _n ≠ 0), the slip ratio S _n is calculated from the following equation (6).
S _n = (Vd _n −V _n ) / Vd _n (6)
When Vd _n = 0 or V _n = 0, it is not included in the data.

(f) Next, the vehicle acceleration and slip ratio data are subjected to moving average processing at every sampling time.
When obtaining a regression line, the reliability of the obtained regression coefficient is poor unless there is a certain number of data. Therefore, by sampling data every sampling time, for example, every several tens of ms, and moving average the data obtained with this sampling time, it is possible to reduce the data variation without reducing the number of data. it can. Here, N is the number of data.

For slip rate,
MS _n = (S ₁ + S ₂ +... + S _n ) / N (7)
MS _{n + 1} = (S ₂ + S ₃ +... + S _{n + 1} ) / N (8)
MS _{n + 2} = (S ₃ + S ₄ +... + S _{n + 2} ) / N (9)
For vehicle acceleration,
MAf _n = (Af ₁ + Af ₂ +... + Af _n ) / N (10)
MAf _{n + 1} = (Af ₂ + Af ₃ +... + Af _{n + 1} ) / N (11)
MAf _{n + 2} = (Af ₃ + Af ₄ +... + Af _{n + 2} ) / N (12)

(g) Subsequently, data (moving averaged vehicle acceleration and slip ratio) is accumulated until the travel distance reaches a predetermined distance. Then, the linear regression coefficient of the slip ratio and the acceleration of the vehicle, that is, the regression coefficient K1 with respect to the vehicle acceleration of the slip ratio and the regression coefficient K2 with respect to the slip ratio of the vehicle acceleration are respectively expressed by the following equations (13), Obtained from (14).

The correlation coefficient R is
R = K1 × K2 (15)
It becomes.

(h) A predetermined number of regression coefficients K1 or regression coefficients K2 (hereinafter referred to as regression coefficient K1) having a correlation coefficient R obtained by the above procedure equal to or greater than a predetermined value (for example, 0.9) are accumulated, and an average thereof The value is obtained and used as a tire identification coefficient. If the correlation coefficient R is less than a predetermined value, the regression coefficient data is discarded. Furthermore, a value obtained by multiplying the average value of the regression coefficient K1 by the vehicle constant Wr / W may be used as the tire identification coefficient. Here, W is the vehicle weight and Wr is the driving wheel load. This is because the driving force F (F = W × Af _n ) required for acceleration of the vehicle body is determined by the frictional force between the driving wheel and the road surface, so that F = μ × Wr using the friction coefficient μ of the road surface, Af _n = μ × Wr / W. Therefore, the difference between the vehicles can be corrected by multiplying by the vehicle constant Wr / W. However, the vehicle constant is 1 for a four-wheel drive vehicle. It is also possible to continuously obtain and update the tire identification coefficient during traveling. In that case, when a regression coefficient having a correlation coefficient R equal to or greater than a predetermined value is obtained, a tire identification coefficient is first calculated, and the tire identification coefficients obtained so far are averaged. As a result, it is possible to cope with changes with time of the tire. That is, it is possible to cope with the case where the winter tire is worn or the hardness of the tread rubber is increased due to aging. For example, when the tire identification coefficient obtained first is 0.059 and then a new tire identification coefficient 0.057 is obtained, the tire identification coefficient is (0.059 + 0.057) /2=0.058. It becomes. Further, when a new tire identification coefficient 0.055 is obtained, the tire identification coefficient is (0.059 + 0.057 + 0.055) /3=0.057. And when this tire identification coefficient is 0.05 or more, it can be set as a winter tire. This threshold value (0.05) is obtained from the experimental value so far.

  The tire stiffness can be determined by comparing with a determination value set in advance for each vehicle.

  Also, the tire stiffness does not change suddenly, so there is no need to calculate it constantly, but the stiffness changes due to wear on the tread or aging of the rubber. It is desirable to calculate and determine For example, tire identification may be performed every 1000 km or every month.

  Next, the tire identification device of the present invention will be described based on examples, but the present invention is not limited to such examples.

Example 1
First, summer tires or winter tires were mounted on a four-wheel drive vehicle.
The vehicle used was a Subaru Legacy.
The summer tire was SP9000 manufactured by Sumitomo Rubber Industries, Ltd., and the winter tire (studless tire) was DS-2 manufactured by Sumitomo Rubber Industries.
A VBOX made by Racelogic was used as the GPS sensor, and the sampling period was set to 0.05 seconds.

Then, according to the above procedure, the wheel speed was calculated from the respective rotational speeds of the four-wheel tires of the vehicle, and the average wheel speed Vd of the driving wheels (four wheels because this example is a four-wheel driving vehicle) was obtained. Next, the vehicle speed V and the acceleration A of the vehicle were calculated from the satellite signal received by the GPS sensor. In this embodiment, the vehicle speed is calculated from the Doppler shift frequency of the GPS received radio wave. The slip ratio S was calculated from the drive wheel average wheel speed Vd and the vehicle acceleration A.
S = (Vd−V) / Vd

  A linear regression coefficient K1 and a correlation coefficient R of the slip ratio with respect to the acceleration of the vehicle with a traveling distance of every 1000 m were obtained. At this time, 10 regression coefficients K1 when the correlation coefficient R was 0.9 or more were accumulated, and the tire was identified from the average value.

  FIG. 3 shows the relationship between the vehicle acceleration and the slip ratio and its regression line.

  The primary regression coefficient of the slip ratio with respect to the vehicle acceleration in the case of the summer tire was 0.0282. The primary regression coefficient in the case of winter tires (studless tires) was 0.0761. The range of the primary regression coefficient for each tire stiffness is set for each vehicle in advance, and the type of tire is determined by comparison with the stiffness level of the tire being mounted. For example, in the case of the legacy of this embodiment, the range of the linear regression coefficient is set as shown in Table 1 below.

  Comparing Table 1 and the linear regression coefficient, it can be seen that summer tires and studless tires can be correctly determined.

  Depending on the stiffness level, for example, the factors used for the calculation of the low air pressure warning device are updated. Also, by periodically detecting the stiffness level, the factor is automatically updated even when the tire wears out or when the stiffness of the studless tire becomes harder due to aging, etc. I was able to.

Comparative Example FIG. 4 shows the result when the vehicle acceleration and the slip ratio are calculated using only the wheel speed without using the GPS sensor and the same vehicle and tire as in the example.

The average wheel speed of the four wheels was taken as the vehicle speed, and the vehicle acceleration was calculated from the vehicle speed. The slip ratio S was calculated as a ratio between the average wheel speed Vf of the front wheels and the average wheel speed Vr of the rear wheels.
S = (Vr−Vf) / Vr

  The linear regression coefficient of the vehicle acceleration with respect to the slip ratio was calculated, but there was almost no difference in the regression coefficient due to the difference in tires, and in either case there was no correlation between the slip ratio and the vehicle acceleration (ie, the phase The number of relationships was small.

It is a block diagram which shows one Embodiment of the tire identification device of this invention. It is a block diagram which shows the electric constitution of the tire identification apparatus in FIG. In the Example of this invention, it is the graph which plotted the slip ratio of the driving wheel with respect to the vehicle acceleration calculated from GPS receiving information. In the comparative example of this invention, it is the graph which plotted the value which remove | divided the wheel speed difference of a front wheel and a rear wheel by the rear-wheel wheel speed with respect to the vehicle acceleration calculated from the wheel speed.

Explanation of symbols

1 Wheel speed sensor
2 Control unit
3 Initialization switch
4 GPS receivers FL, FR, RL, RR Tire

Claims (3)

Rotation speed detection means for detecting the rotation speed of the wheel mounted on the vehicle, wheel speed calculation means for calculating the average wheel speed of the drive wheels from the rotation speed, and a GPS receiver mounted on the vehicle. Acceleration calculation means for calculating the speed and acceleration of the vehicle from satellite signals; slip ratio calculation means for calculating a slip ratio of the drive wheel from the average wheel speed of the drive wheel and the vehicle speed; acceleration of the vehicle; A tire identification device comprising: tire identification means for identifying a currently mounted tire based on a tire front-rear stiffness obtained from a first-order regression coefficient in relation to a slip ratio. A step of detecting a rotational speed of a wheel mounted on the vehicle, a step of calculating an average wheel speed of driving wheels from the rotational speed, a vehicle speed and a satellite signal received by a GPS receiver mounted on the vehicle, and Calculating the vehicle acceleration, calculating the driving wheel slip ratio from the driving wheel average wheel speed and the vehicle speed, and linear regression of the relationship between the vehicle acceleration and the driving wheel slip ratio. And a step of identifying a currently mounted tire based on the longitudinal rigidity of the tire obtained from the coefficient. A computer for identifying a tire mounted on a vehicle is received by a wheel speed calculating means for calculating an average wheel speed of driving wheels from a rotation speed of a wheel mounted on the vehicle, and a GPS receiver mounted on the vehicle. Acceleration calculating means for calculating the speed and acceleration of the vehicle from the satellite signal, slip ratio calculating means for calculating the slip ratio of the driving wheel from the average wheel speed and the vehicle speed, and the acceleration and driving wheel of the vehicle A tire identification program for functioning as a tire identification means for identifying a currently installed tire based on a tire front-rear stiffness obtained from a linear regression coefficient in relation to the slip ratio.

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