JP2005306160A - Method and device for presuming road surface friction coefficient, vehicle control method, and device therefor - Google Patents

Method and device for presuming road surface friction coefficient, vehicle control method, and device therefor Download PDF

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JP2005306160A
JP2005306160A JP2004124331A JP2004124331A JP2005306160A JP 2005306160 A JP2005306160 A JP 2005306160A JP 2004124331 A JP2004124331 A JP 2004124331A JP 2004124331 A JP2004124331 A JP 2004124331A JP 2005306160 A JP2005306160 A JP 2005306160A
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friction coefficient
road surface
surface friction
tread
vibration
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JP4439985B2 (en
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Yasumichi Wakao
泰通 若尾
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Bridgestone Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To enhance the running stability of a vehicle by presuming accurately the road surface friction coefficient in precision in a short time without using a method of frequency analysis. <P>SOLUTION: This method comprises a high frequency component extracting means 13 which extracts the high frequency components from the information of the vibratory waveform sensed by an acceleration sensor 11, a vibratory amplitude sensing means 15 to sense the amplitude of the high frequency component at its time of kicking out, a wheel speed sensing means 12 to sense the wheel speed, a vibratory amplitude correcting means 16 to correct the presumed road surface friction coefficient with the wheel speed, and a road surface friction coefficient presuming means 17 which presumes the size of the road surface friction coefficient by comparing the corrected amplitude with the preset threshold. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、車両の走行時におけるタイヤと路面間の摩擦係数を推定するための方法とその装置に関するものである。   The present invention relates to a method and apparatus for estimating a coefficient of friction between a tire and a road surface when a vehicle is traveling.

自動車の走行安定性を高めるため、走行時のタイヤと路面との間の摩擦係数（路面摩擦係数）を精度良く推定し、車両制御へフィードバックすることが求められている。特に、制駆動や操舵といった危険回避の操作を起こす前に、予めタイヤの走行状態や路面摩擦係数を推定することができれば、例えば、ＡＢＳブレーキやこれを応用した車体姿勢制御装置のより高度な制御等が可能になり、安全性が一段と高まることが予想される。
従来、路面摩擦係数を推定する方法としては、タイヤの微少スリップ率変化とタイヤ前後力との関係から推定する手法（例えば、特許文献１参照）や、車輪速信号に現れるタイヤ共振周波数から推定する方法（例えば、特許文献２参照）などが提案されている。
特開２００１−２５３３３４号公報 特開平９−７６８９８号公報 In order to improve the running stability of an automobile, it is required to accurately estimate a friction coefficient (road surface friction coefficient) between a tire and a road surface during driving and feed back to vehicle control. In particular, if the tire running state and the road surface friction coefficient can be estimated in advance before a risk avoidance operation such as braking / driving or steering is performed, for example, more advanced control of an ABS brake or a vehicle body posture control device using the brake is applied. It is expected that safety will be further enhanced.
Conventionally, as a method of estimating a road surface friction coefficient, a method of estimating from a relationship between a minute slip ratio change of a tire and a tire longitudinal force (see, for example, Patent Document 1) or a tire resonance frequency appearing in a wheel speed signal is used. A method (for example, refer to Patent Document 2) has been proposed.
JP 2001-253334 A JP-A-9-76898

しかしながら、上記従来の方法では、得られた信号を周波数解析する必要があるため、対象とする信号が弱い場合や周波数ピークの変化が小さいといった理由により、推定値を算出するのに必要な時間が車両挙動変化の時定数に比べて長くなってしまうといった問題点があった。例えば、算出に１秒かかるとすると、車両が７０ｋｍ/ｈｒ(約２０ｍ／ｓ)で走行中に急制動する場合、２０ｍ手前の２０ｍ分の路面摩擦係数平均値しか推定できないので、一部氷結している路面等、路面摩擦係数が一様でない路面を想定した場合、２０ｍの位置誤差は致命的となる。この誤差は車速が速いほど大きくなる。
また、周波数解析を用いないで方法としては、ＡＢＳ制動時の制動力と車輪加速度との関係から路面摩擦係数を推定する方法も考えられるが、この場合には、制動を一度かけなければ路面摩擦係数が判明しないといった問題点があった。 However, in the above conventional method, since it is necessary to frequency-analyze the obtained signal, the time required to calculate the estimated value due to the fact that the target signal is weak or the change in the frequency peak is small. There is a problem that the time constant of the vehicle behavior change becomes longer. For example, if it takes 1 second to calculate, if the vehicle suddenly brakes while driving at 70 km / hr (about 20 m / s), only the average value of the road surface friction coefficient for 20 meters before 20 meters can be estimated. When assuming a road surface with a non-uniform road surface friction coefficient, such as a road surface, a position error of 20 m is fatal. This error increases as the vehicle speed increases.
Further, as a method without using frequency analysis, a method of estimating the road surface friction coefficient from the relationship between the braking force and the wheel acceleration at the time of ABS braking is also conceivable. There was a problem that the coefficient was not found.

本発明は、従来の問題点に鑑みてなされたもので、周波数解析の手法を用いることなく、正確にかつ短時間で路面摩擦係数を精度良く推定して、車両の走行安全性を向上させることを目的とする。   The present invention has been made in view of the conventional problems, and accurately estimates a road surface friction coefficient in a short time without using a frequency analysis technique, thereby improving the running safety of the vehicle. With the goal.

本発明者らは、鋭意検討の結果、タイヤトレッドが接地面から離れる手前で、トレッド−路面間に、タイヤ−路面間の摩擦力に依存する滑りが発生すること、及び、上記滑りが加振源となってトレッドに振動が発生することを把握した。そこで、上記トレッドの振動を検出することにより、精度良くかつ速やかに路面摩擦係数を推定することができることを見出し本発明に到ったものである。
詳細には、タイヤの回転伴ってトレッドが接地する際には、それまでは略円筒面であったタイヤは圧縮されて平面状に変形し、トレッドが接地面から離れるときには、圧縮が解放されて平面状から略円筒状に戻る。このトレッドへの圧縮が解放される時点、すなわちトレッドが接地面から離れる手前で、トレッド−路面間に滑りが発生する。この滑りはタイヤ−路面間の摩擦力に依存し、周方向変形が支配的なトレッド中心近傍では、路面摩擦係数が低いと上記圧縮が滑らかに解放されるので、トレッドの振動は小さい。逆に、路面摩擦係数が大きいと、滑る際に力が必要なため、反作用としてトレッドの振動が大きくなる。一方、トレッド端部では、路面摩擦係数が低いほど幅方向の変形量が大きいため、トレッドの振動は大きくなり、路面摩擦係数が大きいと変形量が小さくなるため、トレッドの振動が小さくなる。したがって、このようなタイヤトレッド部の振動を検出することにより、路面摩擦係数を正確に推定することが可能となる。
すなわち、本願の請求項１に記載の発明は、タイヤと路面との間の摩擦係数である路面摩擦係数を推定する方法であって、接地面からトレッドが離れる際に発生するトレッドの振動挙動を検出して路面摩擦係数を推定するようにしたことを特徴とする。 As a result of intensive studies, the present inventors have found that a slip depending on the friction force between the tire and the road surface is generated between the tread and the road surface before the tire tread is separated from the contact surface, and the slip is excited. As a source, we understood that the tread vibrates. Thus, the present inventors have found that the road surface friction coefficient can be estimated accurately and quickly by detecting the vibration of the tread.
Specifically, when the tread contacts the ground as the tire rotates, the tire that has been a substantially cylindrical surface until then is compressed and deformed into a flat surface, and when the tread leaves the ground surface, the compression is released. It returns from a flat shape to a substantially cylindrical shape. Slip occurs between the tread and the road surface when the compression to the tread is released, that is, before the tread leaves the ground surface. This slip depends on the frictional force between the tire and the road surface. In the vicinity of the tread center where the circumferential deformation is dominant, if the road surface friction coefficient is low, the compression is released smoothly, so the vibration of the tread is small. On the other hand, if the road surface friction coefficient is large, a force is required for sliding, so that vibration of the tread increases as a reaction. On the other hand, at the tread end, the lower the road surface friction coefficient, the larger the deformation amount in the width direction. Therefore, the tread vibration increases. When the road surface friction coefficient is large, the deformation amount decreases, so the tread vibration decreases. Therefore, it is possible to accurately estimate the road surface friction coefficient by detecting such vibration of the tire tread portion.
That is, the invention according to claim 1 of the present application is a method for estimating a road surface friction coefficient, which is a friction coefficient between a tire and a road surface, and the vibration behavior of the tread generated when the tread is separated from the ground surface. It is characterized by detecting and estimating the road surface friction coefficient.

請求項２に記載の発明は、請求項１に記載の路面摩擦係数の推定方法において、トレッド中心近傍のトレッド振動を検出して上記路面摩擦係数を推定するようにしたことを特徴とする。
請求項３に記載の発明は、請求項２に記載の路面摩擦係数の推定方法において、トレッド端部のトレッド振動を検出して上記路面摩擦係数を推定するようにしたことを特徴とする。
請求項４に記載の発明は、請求項１〜請求項３のいずれかに記載の路面摩擦係数の推定方法において、上記トレッド振動のうち、路面摩擦係数の大きさの影響がより顕著に現れる高周波成分を抽出し、上記高周波振動成分から路面摩擦係数を推定するようにしたことを特徴とする。
請求項５に記載の発明は、請求項１〜請求項４のいずれかに記載の路面摩擦係数の推定方法において、測定対象となるタイヤを搭載した車輪の速度を検出し、上記推定された路面摩擦係数を上記車輪速度に応じて補正するようにしたことを特徴とする。 The invention according to claim 2 is characterized in that, in the estimation method of the road surface friction coefficient according to claim 1, the road surface friction coefficient is estimated by detecting tread vibration in the vicinity of the center of the tread.
According to a third aspect of the present invention, in the road surface friction coefficient estimating method according to the second aspect, the road surface friction coefficient is estimated by detecting a tread vibration at a tread end portion.
According to a fourth aspect of the present invention, in the method for estimating a road surface friction coefficient according to any one of the first to third aspects, a high frequency in which the influence of the size of the road surface friction coefficient is more prominent among the tread vibrations. A component is extracted, and a road surface friction coefficient is estimated from the high frequency vibration component.
According to a fifth aspect of the present invention, in the road surface friction coefficient estimating method according to any one of the first to fourth aspects, the speed of a wheel on which a tire to be measured is mounted is detected, and the estimated road surface is measured. The friction coefficient is corrected according to the wheel speed.

また、請求項６に記載の発明は、走行中の車両のタイヤ−路面間の摩擦係数を推定する装置であって、トレッドの内面側に配設された振動検出手段と、この振動検出手段で検出された振動の高周波振動成分を抽出する手段と、この抽出された高周波成分の大きさから路面摩擦係数を推定する路面摩擦係数推定手段とを備えたものである。
請求項７に記載の発明は、請求項６に記載の路面摩擦係数推定装置において、上記振動検出手段をトレッド中心近傍またはトレッド中心近傍とトレッド端部の両方に配設したものである。
請求項８に記載の発明は、請求項６または請求項７に記載の路面摩擦係数推定装置において、上記高周波振動成分抽出手段を、ウエーブレットフィルタから構成したものである。
請求項９に記載の発明は、請求項６〜請求項８のいずれかに記載の路面摩擦係数推定装置において、車輪速検出手段を設けるとともに、上記検出された車輪側を用いて上記推定された路面摩擦係数を補正する補正手段を備えたものである。 According to a sixth aspect of the present invention, there is provided a device for estimating a coefficient of friction between a tire and a road surface of a running vehicle, comprising vibration detecting means disposed on the inner surface side of the tread, and the vibration detecting means. Means for extracting the high frequency vibration component of the detected vibration and road surface friction coefficient estimating means for estimating the road surface friction coefficient from the magnitude of the extracted high frequency component are provided.
A seventh aspect of the present invention is the road surface friction coefficient estimating apparatus according to the sixth aspect, wherein the vibration detecting means is disposed in the vicinity of the tread center or in the vicinity of the tread center and at the end of the tread.
The invention according to claim 8 is the road surface friction coefficient estimating apparatus according to claim 6 or claim 7, wherein the high-frequency vibration component extracting means is constituted by a wavelet filter.
According to a ninth aspect of the present invention, in the road surface friction coefficient estimating device according to any one of the sixth to eighth aspects, the wheel speed detection means is provided, and the estimation is performed using the detected wheel side. A correction means for correcting the road surface friction coefficient is provided.

また、請求項１０に記載の発明は、車両の走行状態を制御する装置であって、請求項６〜請求項９のいずれかに記載の路面摩擦係数推定装置と、上記推定された路面摩擦係数を用いて、緊急制御時の初期制動力の最大値を設定する手段とを備えたものである。
請求項１１に記載の発明は、車両の走行状態を制御する方法であって、接地面からトレッドが離れる際に発生する、トレッド中心近傍あるいはトレッド端部のトレッドの振動挙動を検出してタイヤと路面との間の路面摩擦係数を推定するとともに、この推定された路面摩擦係数を用いて、当該車両の緊急制御時における初期制動力の最大値を設定して、上記車両の制動力を制御するようにしたことを特徴とする。 The invention according to claim 10 is an apparatus for controlling the running state of the vehicle, wherein the road surface friction coefficient estimating device according to any one of claims 6 to 9 and the estimated road surface friction coefficient. And a means for setting the maximum value of the initial braking force at the time of emergency control.
The invention according to claim 11 is a method for controlling the running state of the vehicle, and detects the vibration behavior of the tread near the tread center or at the end of the tread that occurs when the tread leaves the ground contact surface. Estimating the road surface friction coefficient with the road surface, and using the estimated road surface friction coefficient, setting the maximum initial braking force during emergency control of the vehicle to control the braking force of the vehicle It is characterized by doing so.

本発明によれば、接地面からトレッドが離れる際に発生するトレッドの振動の挙動、特に、路面摩擦係数の大きさの影響がより顕著に現れる、トレッド中心近傍のトレッド振動の高周波成分を抽出し、上記高周波振動成分から路面摩擦係数を推定するようにしたので、周波数解析の手法を用いることなく、正確にかつ短時間で路面摩擦係数を精度良く推定することができる。このとき、上記推定された路面摩擦係数を上記車輪速度に応じて補正することにより、路面摩擦係数の推定精度を更に向上させることができる。上記推定された路面摩擦係数を用いて、緊急制御時の初期制動力の最大値を設定するようにすれば、制動開始前に適切な初期制動力を設定することができるので、車両の走行安全性を著しく向上させることができる。   According to the present invention, the high frequency component of the tread vibration in the vicinity of the tread center where the behavior of the tread vibration generated when the tread is separated from the ground contact surface, particularly the influence of the road surface friction coefficient appears more prominently is extracted. Since the road surface friction coefficient is estimated from the high-frequency vibration component, the road surface friction coefficient can be accurately estimated in a short time without using a frequency analysis method. At this time, it is possible to further improve the estimation accuracy of the road surface friction coefficient by correcting the estimated road surface friction coefficient according to the wheel speed. If the maximum value of the initial braking force at the time of emergency control is set using the estimated road friction coefficient, an appropriate initial braking force can be set before the start of braking. Property can be remarkably improved.

以下、本発明の最良の形態について、図面に基づき説明する。
図１は、本最良の形態に係わる路面摩擦係数推定装置１０の構成を示す機能ブロック図で、同図において、１１はタイヤ周方向の振動を検出する振動検出手段である加速度センサで、本例では、図２に示すように、上記加速度センサ１１を、タイヤ２０のタイヤトレッド２１の内側でインナーライナー部２２の中心近傍に、その検出方向が周方向（タイヤ回転方向）になるように取付け、タイヤトレッド２１の幅中心部の周方向振動を検出するようにしている。
また、１２は車輪の回転速度を検出する車輪速検出手段で、この車輪速検出手段１２としては、例えば、磁気抵抗素子を用いトランスミッションの回転を検出するタイプのものなど、周知の車輪速センサを使用することができる。
１３は上記加速度センサ１１の検出したタイヤ振動の情報から、その高周波成分を抽出する高周波成分抽出手段で、本例では、この高周波成分抽出手段として、ウエーブレットフィルタを用いている。上記ウエーブレットフィルタは、画像処理等で用いられているウエーブレット変換を用いたフィルタで、元の波形データの情報を損なわずに所定の周波数帯域の信号を抽出するもので、これにより、従来のハイパスフィルタを用いた場合に比較して、効率よく低周波成分を除去することができる。
１４は上記加速度センサ１１の振動レベルの時間変化から、タイヤトレッド２１が接地した時間及び上記タイヤトレッド２１が接地面から離れた時間を検出する接地・蹴り出し時間検出手段、１５は上記高周波成分抽出手段１３で抽出されたタイヤ振動の高周波成分の振幅を検出する振動振幅検出手段、１６は上記検出された振幅を上記車輪速検出手段１２で検出された車輪速に応じて補正する振動振幅補正手段、１７は上記補正された振動振幅と予め設定された閾値と比較して路面摩擦係数を推定する路面摩擦係数推定手段である。 Hereinafter, the best mode of the present invention will be described with reference to the drawings.
FIG. 1 is a functional block diagram showing the configuration of a road surface friction coefficient estimating apparatus 10 according to the best mode. In FIG. 1, reference numeral 11 denotes an acceleration sensor which is a vibration detecting means for detecting vibration in the tire circumferential direction. Then, as shown in FIG. 2, the acceleration sensor 11 is mounted on the inner side of the tire tread 21 of the tire 20 in the vicinity of the center of the inner liner portion 22 so that the detection direction thereof is a circumferential direction (tire rotation direction). The circumferential vibration at the center of the width of the tire tread 21 is detected.
Reference numeral 12 denotes a wheel speed detecting means for detecting the rotational speed of the wheel. As the wheel speed detecting means 12, for example, a known wheel speed sensor such as a type that detects the rotation of the transmission using a magnetoresistive element is used. Can be used.
Reference numeral 13 denotes high-frequency component extraction means for extracting high-frequency components from the tire vibration information detected by the acceleration sensor 11, and in this example, a wavelet filter is used as the high-frequency component extraction means. The wavelet filter is a filter using wavelet transform used in image processing or the like, and extracts a signal in a predetermined frequency band without damaging the information of the original waveform data. Compared with the case where a high-pass filter is used, low frequency components can be efficiently removed.
14 is a grounding / kicking-out time detecting means for detecting the time when the tire tread 21 is grounded and the time when the tire tread 21 is separated from the ground surface from the time variation of the vibration level of the acceleration sensor 11; Vibration amplitude detection means for detecting the amplitude of the high-frequency component of the tire vibration extracted by means 13, and vibration amplitude correction means 16 for correcting the detected amplitude in accordance with the wheel speed detected by the wheel speed detection means 12. , 17 is road surface friction coefficient estimating means for estimating the road surface friction coefficient by comparing the corrected vibration amplitude with a preset threshold value.

次に、上記構成の路面摩擦係数推定装置１０を用いて路面摩擦係数を推定する方法について説明する。
図３（ａ）及び図４（ａ）の破線は、それぞれ、上記タイヤ２０を装着した車両を、ドライアスファルト路面（μ≒１）及び低摩擦係数路面（μ≒０．２）に一定速度で進入した際の上記加速度センサ１１で検出された振動波形の一例を示す図で、実線は上記振動波形の低周波成分を表わす。また、図３(ｂ)及び図４（ｂ）の破線は、それぞれ高周波成分抽出手段１３を用いて抽出した上記振動波形の高周波成分を表わす。
図から明らかなように、上記加速度センサ１１で検出された振動波形の振幅は、高摩擦係数路面であるドライアスファルト路面と低摩擦係数路面とで大きく異なっており、特に、蹴り出し部の高周波成分の振幅の差異が著しい。
そこで、高周波成分抽出手段１３により、上記加速度センサ１１で検出したタイヤの振動の情報から高周波成分を抽出し、振動振幅検出手段１５にて、上記高周波成分の蹴り出し時の振幅を検出し、路面摩擦係数推定手段１７にて、上記振幅の大きさと予め設定された閾値とを比較すれば、上記振動波形のデータを周波数分析することなく、路面摩擦係数の大小を正確に推定することができる。 Next, a method for estimating the road surface friction coefficient using the road surface friction coefficient estimation device 10 having the above-described configuration will be described.
The broken lines in FIGS. 3 (a) and 4 (a) indicate that the vehicle equipped with the tire 20 is placed on the dry asphalt road surface (μ≈1) and the low friction coefficient road surface (μ≈0.2) at a constant speed, respectively. It is a figure which shows an example of the vibration waveform detected by the said acceleration sensor 11 at the time of approach, and a continuous line represents the low frequency component of the said vibration waveform. Also, the broken lines in FIG. 3B and FIG. 4B represent the high frequency components of the vibration waveform extracted using the high frequency component extracting means 13, respectively.
As is apparent from the figure, the amplitude of the vibration waveform detected by the acceleration sensor 11 differs greatly between the dry asphalt road surface, which is a high friction coefficient road surface, and the low friction coefficient road surface. The difference in amplitude is remarkable.
Therefore, the high-frequency component extraction means 13 extracts the high-frequency component from the tire vibration information detected by the acceleration sensor 11, and the vibration amplitude detection means 15 detects the amplitude of the high-frequency component when it is kicked, and the road surface. If the friction coefficient estimating means 17 compares the magnitude of the amplitude with a preset threshold value, it is possible to accurately estimate the magnitude of the road surface friction coefficient without frequency analysis of the vibration waveform data.

ところで上記振幅の大きさ、すなわち、接地時にトレッドへの作用する圧縮力の大きさは、路面摩擦係数だけでなく、路面とタイヤとの衝突速度の大きさにも依存する。すなわち、図５に示すように、車輪速が大きいと路面との衝突速度が大きい。そこで、上記高周波成分の振幅の大きさの要因を、路面摩擦係数によるものと車輪速によるものとに分離するため、振動振幅検出手段１５にて検出して振動振幅を車輪速検出手段１２にて検出した車輪速により補正し、しかる後に、路面摩擦係数推定手段１７にて予め設定された閾値と比較して路面摩擦係数を推定するようにすれば、路面摩擦係数の推定精度を向上させることができる。
なお、上記高周波成分の振幅の大きさを車輪速により補正する代わりに、上記閾値を車輪速により変更しても同様の結果を得ることができる。 By the way, the magnitude of the amplitude, that is, the magnitude of the compressive force acting on the tread at the time of contact depends on not only the road surface friction coefficient but also the magnitude of the collision speed between the road surface and the tire. That is, as shown in FIG. 5, when the wheel speed is high, the collision speed with the road surface is high. Therefore, in order to separate the factor of the amplitude of the high-frequency component into that due to the road surface friction coefficient and that due to the wheel speed, the vibration amplitude is detected by the vibration amplitude detecting means 15 and the vibration amplitude is detected by the wheel speed detecting means 12. If the road surface friction coefficient is corrected by the detected wheel speed and then compared with a threshold value set in advance by the road surface friction coefficient estimating means 17, the estimation accuracy of the road surface friction coefficient can be improved. it can.
Note that the same result can be obtained even if the threshold value is changed by the wheel speed instead of correcting the amplitude of the high-frequency component by the wheel speed.

このように、本最良の形態によれば、加速度センサ１１で検出された振動波形の情報から高周波成分を抽出するとともに、上記高周波成分の蹴り出し時の振幅を検出し、上記振幅の大きさと予め設定された閾値とを比較して路面摩擦係数の大小を推定するようにしたので、振動波形のデータを周波数分析することなく、路面摩擦係数を正確に推定することができる。
また、車輪速検出手段１２にて車輪速を検出し、この車輪速により上記推定された路面摩擦係数を補正するようにしたので、路面摩擦係数の推定精度を更に向上させることができる。
また、本手法は、タイヤの転動時におけるトレッドの振動のみを用いて路面摩擦係数を推定するようにしているため、スリップ率が実質ゼロの通常走行時においても、路面摩擦係数を正確に推定することができる。したがって、上記構成の路面摩擦係数推定装置１０と、上記推定された路面摩擦係数を用いて、緊急制御時の初期制動力の最大値を設定する手段を備えた車両制御装置を構成することにより、例えば、ＡＢＳ制動時における制動開始前に適切な初期制動力を設定することができるので、車両の走行安全性を著しく向上させることができる。 Thus, according to this best mode, the high-frequency component is extracted from the information of the vibration waveform detected by the acceleration sensor 11 and the amplitude at the time of kicking out the high-frequency component is detected. Since the magnitude of the road surface friction coefficient is estimated by comparing with the set threshold value, the road surface friction coefficient can be accurately estimated without frequency analysis of vibration waveform data.
In addition, since the wheel speed is detected by the wheel speed detecting means 12 and the estimated road surface friction coefficient is corrected based on the wheel speed, the estimation accuracy of the road surface friction coefficient can be further improved.
In addition, because this method estimates the road surface friction coefficient using only the tread vibration during tire rolling, the road surface friction coefficient can be accurately estimated even during normal driving with a slip rate of virtually zero. can do. Therefore, by configuring the vehicle surface friction coefficient estimating device 10 having the above-described configuration and a vehicle control device including means for setting the maximum value of the initial braking force during emergency control using the estimated road surface friction coefficient, For example, since an appropriate initial braking force can be set before the start of braking during ABS braking, the traveling safety of the vehicle can be significantly improved.

なお、上記最良の形態では、加速度センサ１１で検出された振動波形の情報から高周波成分を抽出して路面摩擦係数の推定する場合について説明したが、図３（ａ）と図４（ａ）とを比較すれば明らかなように、低周波成分についても、高摩擦係数路面と低摩擦係数路面の振幅の大きさは異なっているので、低周波成分を別途抽出し、上記閾値とは異なる閾値を用いて、上記低周波成分の振幅の大きさを閾値とを比較すれば、路面摩擦係数の大小を推定することができる。
また、上記例では、タイヤ２０のインナーライナー部２２の中心近傍に加速度センサを取付けてタイヤトレッド２１の幅中心部の周方向振動を検出するようにしたが、上記中心近傍とは逆の変形をするトレッド端部の振動についても検出し、上記中心部のデータと組合わせて路面摩擦係数の大きさを推定するようにすれば、路面摩擦係数を更に正確に推定することができる。 In the above-described best mode, the case where the high-frequency component is extracted from the information of the vibration waveform detected by the acceleration sensor 11 and the road surface friction coefficient is estimated has been described. FIG. 3 (a) and FIG. 4 (a) As is clear from the above, since the amplitude of the high friction coefficient road surface and the low friction coefficient road surface are different for the low frequency component, the low frequency component is extracted separately, and a threshold value different from the above threshold value is obtained. If the magnitude of the amplitude of the low frequency component is compared with a threshold value, the magnitude of the road surface friction coefficient can be estimated.
In the above example, an acceleration sensor is attached in the vicinity of the center of the inner liner portion 22 of the tire 20 to detect the circumferential vibration of the center portion of the tire tread 21. If the vibration of the tread end portion to be detected is detected and combined with the data of the center portion to estimate the magnitude of the road surface friction coefficient, the road surface friction coefficient can be estimated more accurately.

また、上記例では、加速度センサ１１が１個の場合について説明したが、２個以上設置してもよい。本発明では、車両が周長を進む毎に路面摩擦係数を推定してことになるので、従来のように時間間隔ではなく、車両の進む距離毎にデータを更新できるので、更新間隔が時間に依存しないという利点を有する。したがって、センサの数を増やせは、それだけ更新距離を短くできる。
また、本例では、加速度センサ１１をタイヤインナーライナー部に配置したが、タイヤの接地面に近いトレッドゴム内に加速度センサ１１を配置してもよい。 Moreover, although the case where the number of the acceleration sensors 11 was one was demonstrated in the said example, you may install two or more. In the present invention, since the road surface friction coefficient is estimated every time the vehicle travels along the circumference, the data can be updated for each distance traveled by the vehicle, not the time interval as in the prior art. It has the advantage of not relying on it. Therefore, increasing the number of sensors can shorten the update distance accordingly.
In this example, the acceleration sensor 11 is disposed in the tire inner liner portion. However, the acceleration sensor 11 may be disposed in the tread rubber near the tire contact surface.

以上説明したように、本発明によれば、周波数解析の手法を用いることなく、正確にかつ短時間で路面摩擦係数を精度良く推定することができるので、上記推定された路面摩擦係数を用いて、緊急制御時の初期制動力の最大値を設定するなど、上記情報を車両制御へフィードバックすることにより、車両の走行安定性を格段に向上させることができる。   As described above, according to the present invention, it is possible to accurately and accurately estimate the road surface friction coefficient in a short time without using the frequency analysis method. Therefore, the estimated road surface friction coefficient is used. By feeding back the above information to the vehicle control, such as setting the maximum value of the initial braking force during emergency control, the running stability of the vehicle can be significantly improved.

本発明の最良の形態に係わる路面摩擦係数推定装置の構成を示す機能ブロック図である。It is a functional block diagram which shows the structure of the road surface friction coefficient estimation apparatus concerning the best form of this invention. 加速度センサの装着位置の一例を示す図である。It is a figure which shows an example of the mounting position of an acceleration sensor. ドライアスファルト路面における振動レベルの時間変化を示す図である。It is a figure which shows the time change of the vibration level in a dry asphalt road surface. 低摩擦係数路面における振動レベルの時間変化を示す図である。It is a figure which shows the time change of the vibration level in a low friction coefficient road surface. 車輪速と高周波振動成分の振幅との関係を示す図である。It is a figure which shows the relationship between a wheel speed and the amplitude of a high frequency vibration component.

符号の説明Explanation of symbols

１０ 路面摩擦係数推定装置、１１ 加速度センサ、１２ 車輪速検出手段、
１３ 高周波成分抽出手段、１４ 接地・蹴り出し時間検出手段、
１５ 振動振幅検出手段、１６ 振動振幅補正手段、１７ 路面摩擦係数推定手段、
２０ タイヤ、２１ タイヤトレッド、２２ インナーライナー部。 DESCRIPTION OF SYMBOLS 10 Road surface friction coefficient estimation apparatus, 11 Acceleration sensor, 12 Wheel speed detection means,
13 High-frequency component extraction means, 14 Grounding / kicking time detection means,
15 vibration amplitude detection means, 16 vibration amplitude correction means, 17 road surface friction coefficient estimation means,
20 tires, 21 tire treads, 22 inner liner parts.

Claims (11)

接地面からトレッドが離れる際に発生するトレッドの振動挙動を検出し、タイヤと路面との間の摩擦係数である路面摩擦係数を推定するようにしたことを特徴とする路面摩擦係数の推定方法。   A method for estimating a road surface friction coefficient, comprising detecting a vibration behavior of a tread generated when the tread is separated from a ground surface and estimating a road surface friction coefficient that is a friction coefficient between a tire and a road surface. トレッド中心近傍のトレッド振動を検出して上記路面摩擦係数を推定するようにしたことを特徴とする請求項１に記載の路面摩擦係数の推定方法。   2. The method for estimating a road surface friction coefficient according to claim 1, wherein the road surface friction coefficient is estimated by detecting tread vibration in the vicinity of the tread center. トレッド端部のトレッド振動を検出して上記路面摩擦係数を推定するようにしたことを特徴とする請求項２に記載の路面摩擦係数の推定方法。   3. The method for estimating a road surface friction coefficient according to claim 2, wherein the road surface friction coefficient is estimated by detecting tread vibration at a tread edge. 上記トレッド振動の高周波成分を抽出し、上記高周波振動成分から路面摩擦係数を推定するようにしたことを特徴とする請求項１〜請求項３のいずれかに記載の路面摩擦係数の推定方法。   4. The road friction coefficient estimation method according to claim 1, wherein a high frequency component of the tread vibration is extracted and a road friction coefficient is estimated from the high frequency vibration component. 測定対象となるタイヤを搭載した車輪の速度を検出し、上記推定された路面摩擦係数を上記車輪速度に応じて補正するようにしたことを特徴とする請求項１〜請求項４のいずれかに記載の路面摩擦係数の推定方法。   The speed of a wheel on which a tire to be measured is mounted is detected, and the estimated road surface friction coefficient is corrected according to the wheel speed. The estimation method of the road surface friction coefficient of description. トレッドの内面側に配設された振動検出手段と、この振動検出手段で検出された振動の高周波振動成分を抽出する手段と、この抽出された高周波成分の大きさから路面摩擦係数を推定する路面摩擦係数推定手段とを備えたことを特徴とする路面摩擦係数推定装置。   A vibration detecting means disposed on the inner surface side of the tread, a means for extracting a high frequency vibration component of vibration detected by the vibration detecting means, and a road surface for estimating a road surface friction coefficient from the magnitude of the extracted high frequency component A road surface friction coefficient estimating device comprising: a friction coefficient estimating means. 上記振動検出手段をトレッド中心近傍またはトレッド中心近傍とトレッド端部の両方に配設したことを特徴とする請求項６に記載の路面摩擦係数推定装置。   7. The road surface friction coefficient estimating device according to claim 6, wherein the vibration detecting means is disposed in the vicinity of the tread center or both in the vicinity of the tread center and the tread end. 上記高周波振動成分抽出手段を、ウエーブレットフィルタから構成したことを特徴とする請求項６または請求項７に記載の路面摩擦係数推定装置。   The road surface friction coefficient estimating apparatus according to claim 6 or 7, wherein the high-frequency vibration component extracting means comprises a wavelet filter. 車輪速検出手段を設けるとともに、上記検出された車輪側を用いて上記推定された路面摩擦係数を補正する補正手段を備えたことを特徴とする請求項６〜請求項８のいずれかに記載の路面摩擦係数推定装置。   9. The vehicle according to claim 6, further comprising a correction unit that provides a wheel speed detection unit and corrects the estimated road friction coefficient using the detected wheel side. Road friction coefficient estimation device. 請求項６〜請求項９のいずれかに記載の路面摩擦係数推定装置と、上記推定された路面摩擦係数を用いて、緊急制御時の初期制動動力の最大値を設定する手段とを備えたことを特徴とする車両制御装置。   A road surface friction coefficient estimating device according to any one of claims 6 to 9, and means for setting a maximum value of initial braking power during emergency control using the estimated road surface friction coefficient. A vehicle control device. 接地面からトレッドが離れる際に発生する、トレッド中心近傍あるいはトレッド端部のトレッドの振動挙動を検出してタイヤと路面との間の路面摩擦係数を推定するとともに、この推定された路面摩擦係数を用いて、当該車両の緊急制御時における初期制動力の最大値を設定して、上記車両の制動力を制御するようにしたことを特徴とする車両制御方法。   The road surface friction coefficient between the tire and the road surface is estimated by detecting the vibration behavior of the tread near the tread center or at the end of the tread that occurs when the tread is separated from the ground contact surface, and the estimated road surface friction coefficient is A vehicle control method characterized in that a maximum value of an initial braking force during emergency control of the vehicle is set to control the braking force of the vehicle.
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