JP3809519B2 - Road surface condition estimation method - Google Patents

Road surface condition estimation method Download PDF

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JP3809519B2
JP3809519B2 JP2001111367A JP2001111367A JP3809519B2 JP 3809519 B2 JP3809519 B2 JP 3809519B2 JP 2001111367 A JP2001111367 A JP 2001111367A JP 2001111367 A JP2001111367 A JP 2001111367A JP 3809519 B2 JP3809519 B2 JP 3809519B2
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road
temperature
heat
amount
measurement value
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JP2002311157A (en
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博朗 北川
晃之 中村
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国土交通省国土技術政策総合研究所長
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【0001】
【発明の属する技術分野】
本発明は、湿潤、積雪、凍結等の路面状態を把握するための方法に係り、特に、低コストで、路面状態推定を自動化し、かつ局地的な判断が可能な路面状態推定方法に関するものである。
【0002】
【従来の技術】
道路交通において、湿潤、積雪、凍結等の路面状態が生じると、スリップ事故が発生しやすい。このため湿潤、積雪、凍結等の危険な路面状態を速やかに検知して自動車の運転手に注意を促す必要がある。しかし、長距離に及ぶ道路を常に巡回監視するのは、人手、コストの面で困難であるため、このような路面状態を把握する手段として路面状態検出センサが用いられる。
【0003】
従来の路面状態検出センサは、主に2つに分けられる。
【0004】
第1のグループは、道路表面(路面)に赤外線または電磁波を照射し、路面からの反射率を計測するものである。このセンサでは、道路近傍に赤外線照射装置、受光装置および信号処理装置を設置し、道路への入射光と反射光との強度比が路面状態によって異なることを用いて路面状態を推定する。
【0005】
第2のグループとしては、道路近傍の気象量及び路面温度を計測するセンサが挙げられる。路面温度計測には、熱電対、赤外放射温度計等の単点計測用のセンサに加えて、多点計測が可能で長距離の温度を計測するのに適した光ファイバ温度レーダを用いる手法も提案されている。このセンサは、道路管理担当者が過去の知見に基づいて路面状態を推定するときの判断材料として用いられる。
【0006】
【発明が解決しようとする課題】
赤外線または電磁波を照射する方式のセンサを用いて路面状態を道路の長手方向に沿って連続的に把握するためには、多数のセンサを設置する必要があり、コストがかかる。
【0007】
一方、気象量と路面温度とを計測する場合は、気象量観測地がある程度の広域に対して適用可能であること、および光ファイバ温度レーダが長距離に敷設可能であることから低コストである。しかし、路面状態を判断する道路管理担当者に経験が求められること、及び危険と判断する地域を限定することが難しいという問題がある。
【0008】
そこで、本発明の目的は、上記課題を解決し、低コストで、路面状態推定を自動化し、かつ局地的な判断が可能な路面状態推定方法を提供することにある。
【0009】
【課題を解決するための手段】
上記目的を達成するために本発明は、路面下に埋設した光ファイバ温度レーダにより計測した地中温度計測値に基づき地中側から路面に流入する熱量(We)を求め、道路近傍に設置した気象計(気温計、湿度計、日射計、雪雨量計、風速計、放射収支計を含む)により計測した大気の温度、日射強度などの気象量計測値と、前記地中温度計測値から算出し、あるいは前記光ファイバ温度レーダなどの温度計測器で計測した路面温度(Te)とに基づき大気側から路面に流入する熱量(Wa)を求め、前記路面温度(Te)と、前記気象量計測値の気温計測値、相対湿度計測値、風速計測値とに基づき路面上の水分の蒸発による蒸発熱(Wev)を求め、地中側から路面に流入する熱量(We)と大気側から路面に流入する熱量(Wa)の差と、前記蒸発熱(Wev)とから湿潤判定値(Y)を求めて、路面の湿潤状態を判定し、前記地中温度計測値及び前記気象量計測値と、前記湿潤判定値(Y)とに基づき路面の状態を推定するものである。
【0010】
路面への薬剤散布がない場合は、前記路面温度(Te)とその時間当たりの変化量(ΔTe)とから路面の積雪状態を判定し、路面への薬剤散布がある場合は、前記路面温度(Te)と前記変化量(ΔTe)と上記蒸発熱(Wev)と積雪の融解または凝固による潜熱量(δW)とから路面の積雪状態を判定してもよい。
【0014】
【発明の実施の形態】
以下、本発明の一実施形態を添付図面に基づいて詳述する。
【0015】
本発明の原理は、2つの異なる方法で求めた路面への流入熱量から路面状態を求めるものである。まず、2つの熱量計算方法について説明する。
【0016】
第1の方法は、道路近傍に気象計(気温計、湿度計、日射計、雪雨量計、風速計、放射収支計を含む)を設置して、これらの気象量計測値から路面に流入する熱量を求めるものである。
【0017】
ここで、路面の熱収支関係は、概念的には図1の内容で表される。路面の熱収支は、大気からの熱伝達、大気赤外放射と路面赤外放射、日射エネルギの吸収、及び道路内部熱伝達に分類することができる。本発明では、第1の方法を用いて、道路内部熱伝達を除いた道路の上側(大気側)から流入する熱量の総和Waを計算する。実際には、濡れ路面の乾燥、積雪の融解等の路面上水分の相変化に伴う熱移動(潜熱伝達)も存在するが、この熱量を検出することが本発明の目的であるため、ここでは潜熱伝達は考慮しない。
【0018】
Wa=[大気からの熱伝達]+[大気赤外放射と路面赤外放射]+[日射エネルギの吸収]
上記の各熱量を気象量計測値から求める計算式を以下に示す。
(1)大気からの熱伝達
大気からの熱伝達Q1は、大気と路面との接触による熱移動であり、次式で求める。
【0019】
Q1=hT ×(Ta−Te)×A (式1)
ただし、 hT :熱伝達係数
Ta:大気の温度
Te:路面温度
A:熱が伝わる面積
である。
(2)大気赤外放射と路面赤外放射
大気から路面に対する放射Q2と、路面から大気に対する放射Q3との計算は、それぞれ次の式で表される。
【0020】
Q2=εa×σ×Ta4 (式2)
Q3=εr×σ×Te4 (式3)
ただし、 εa:大気の放射率
Ta:大気の温度
εr:路面の放射率
Te:路面温度
σ:ステファン・ボルツマン定数
である。
(3)日射エネルギの吸収
日射量と路面の日射吸収率とから、路面に吸収される日射エネルギQ4を算出する。
【0021】
Q4=(1−r)×I (式4)
ただし、 r:路面のアルベト数
I:日射強度
である。
【0022】
よって、
Wa=Q1+Q2+Q3+Q4
により、大気側から路面に流入する熱量の総和Waを求めることができる。
【0023】
第2の方法は、地中に埋設した光ファイバ温度レーダによる地中温度計測値に基づき、地中側から路面に流入する熱量(第1の方法で除外した道路内部熱伝達による流入熱量)を求めるものである。
【0024】
大気側から路面への流入熱量ΔWがΔW* の時、道路に埋設した光ファイバで計測した地中温度Tf がΔt時間当たりΔTf だけ変化したとする。このとき、ΔTf は、ΔW=0の時の光ファイバ埋設位置fでの温度変化量δTf0と、大気側から路面へ熱量ΔW* が流入してきたときの温度変化量δTf との和で表すことができる。
【0025】
ΔTf =δTf0+δTf (式5)
式5において、ΔW=0の時の光ファイバ埋設位置fでの温度変化量δTf0は、次の方法により求める。地中から路面への流入熱W2 は、地中内部の温度分布から求まる。ここでは、地中から路面への流入熱W2 を基底温度T0 から求める方式で説明する。
【0026】
基底温度T0 を利用する方式は、地中深いところ(数10m程度の深さ)の温度が年間を通してほぼ一定になるということを利用するものであり、この温度を基底温度T0 とすると、路面から地中深いところまでの熱等価回路は図2で表すことができる。即ち、地表の測定点から所定の深さごとに地中温度の測定点があるとき、各測定点間には熱抵抗が存在し、各測定点には熱容量が存在し、地表の測定点には大気側から路面への流入熱W1 が入力される。
【0027】
熱量計算は、計算刻み時間Δtごとに行う。地中を図2に示すような階層構造と見なす場合、地表を1番目としたときk番目の階層における地中温度Tk は式6であらわされる。
【0028】
ここで、 R=Δh/λT
C=ρ・Cp ・ΔhD
ただし、
R:当該階層の熱抵抗
C:当該階層の熱容量
ΔhD :道路下深さ方向の刻み幅
λT :当該階層における熱伝導率
ρ:当該階層における地中物質の密度
p :当該階層における面積当たり熱容量
k :階層を表す添字変数(123 ,…)
である。
【0029】
ここで、境界条件は式7、式8で表される。
【0030】
(T1 −T2 )/R1 =W1 (式7)
n =T0 (式8)
式5から式8までの式を解くことで、光ファイバ埋設位置fにおける温度変化量δTf0を求めることができる。
【0031】
次に、図3に示すように、路面から光ファイバ埋設位置fへ流入する熱量と、それに伴う光ファイバ埋設位置fの温度変化量が直線で近似できる範囲内で路面に対する流入熱の変化量ΔWを任意の値ΔWz として与える。このとき、光ファイバ埋設位置fでの仮の温度変化量ΔTfzは、式7のW1 にΔWz を代入して式6から式8までの式を解くことで求めることができる。温度変化量ΔTfzは、ΔW=0の時の光ファイバ埋設位置fでの温度変化量δTf0と、任意に定めた路面への流入熱量ΔWz によって与えられる温度変化量δTfzとの和で表すことができる。
【0032】
ΔTfz=δTf0+δTfz (式9)
よって、W=0の時の光ファイバ埋設位置fでの温度変化量δTf0と仮の温度変化量ΔTfzとが上記までに求められるので、温度変化量δTfzが求まる。
【0033】
また、図3に示す直線関係を仮定しているので、式10の関係が成り立つ。
【0034】
δTf /ΔW* =δTfz/ΔW (式10)
式9、式10から、路面に流入する熱量ΔW* を求める式11が得られる。
【0035】
ΔW* =(ΔWz /δTfz)・δTf (式11)
式11において、δTf は実際の光ファイバ埋設位置fでの温度変化量δTfzは、式9から得られ、また、ΔWz は任意に定めることのできる値であることから、実際の熱量の変化量ΔW* を算出することができる。このようにして求めた熱量ΔW* が地中側から路面への流入熱Weである。
【0036】
上記の計算に必要となる地中の熱定数は、地中の物質の組成によって一定なので、事前に熱流計を用いて計測しておけば、地中側から路面への流入熱Weを正確に算出することができる。
【0037】
次に、第1の方法で求めた熱量Waと第2の方法で求めた熱量Weとを用いて路面状態を推定する手法を以下に述べる。
【0038】
まず、第1の方法で求めた熱量Wa及び熱量Weを用いて、路面の湿潤状態を判定する方法を述べる。路面上の水分の厚みをhW (t)とすると、水分の厚みhW (t)と蒸発熱Wev(t)との関係は式12で表すことができる。
【0039】
W (t)=hW 0−Wev(t)/λW (式12)
ここで、Wev(t)は式13により気象量より求められる値である。
【0040】
ただし、
W 0:降雨直後の路面に溜った水分の厚み
λW :水の蒸発潜熱
α,β:定数
v:風速
H:相対湿度
Te:路面温度
Ta:気温
P(Te):温度Teにおける水分の飽和水蒸気圧
P(Ta):温度Taにおける水分の飽和水蒸気圧
である。
【0041】
このように、本発明では、路面上の水分の蒸発による蒸発熱Wevを路面水分厚hW 0、風速v、路面温度Te、相対湿度H、気温Taの測定値(一部推定値も含む)と既知の諸量とから求める。
【0042】
湿潤状態では、大気側から路面への流入熱Wa、大地(地中側)から路面への流入熱We、蒸発熱Wevの間には、以下の関係式が成立する。
【0043】
Wa−We=Wev (式14)
ここで、湿潤判定値Yとして式15を導入する。
【0044】
Y=(Wa−We)/Wev (式15)
湿潤判定値Yは、理論的に、湿潤状態では1、乾燥状態及び凍結状態では0となるので、この値をモニタしていると湿潤の有無が判定できる。即ち、本発明では、大気側から路面への流入熱Wa、地中側から路面への流入熱We、路面上の水分の蒸発による蒸発熱Wevを用いて湿潤判定値Yを求め、この湿潤判定値Yにより路面の湿潤状態を判定する。
【0045】
次に積雪状態の判定方法を述べる。積雪状態の判定条件は、路面への薬剤散布がある場合とない場合とで異なる。路面への薬剤散布がない場合は、次の判定条件によって容易に積雪状態判定が可能である。
【0046】
Te=0℃ かつ ΔTe=0℃
ただし、
ΔTe:計測時間当たりの路面温度の変化量
である。
【0047】
このように、路面への薬剤散布がない場合は、路面温度Teを用い、路面温度Teが時間経過によらず0℃を維持していることで積雪状態が判定できる。
【0048】
薬剤散布が有り得る場合は、まず、積雪判定値Zを式16で定義する。
【0049】
Z=ΔTe/ΔTc (式16)
ただし、
ΔTe:計測時間当たりの路面温度の上昇値(測定値)
ΔTc:大気側からの流入熱Waが流入したときの路面温度の上昇値(計算値)
である。路面温度の変化量であるΔTe及びΔTcは、路面への流入熱We及びWaにそれぞれほぼ比例する。これらの比例関係(ΔTeがWeに比例、ΔTcがWaに比例)によって、ほぼΔTe/ΔTc=We/Waとなる。従って、
Z=We/Wa (式16´)
と表すことができる。
【0050】
また、湿潤状態の判定に用いた湿潤判定値Yについて考えると、積雪の融解または凝固に使われる潜熱量をδWとすれば、
となり、湿潤判定値Yは、積雪状態では
Y=1以上 融解過程(δWが負)のとき
Y=1以下 凝固過程(δWが正)のとき
となる。
【0051】
次に、大気側から路面への流入熱Waと地中側から路面への流入熱Weとの差をΔWとすると、
となる。ここで、δWは、融解過程において正、凝固過程において負となる。
【0052】
式16´、式18から、積雪判定値Zは、次のように表すことができる。
【0053】
式19から以下の条件によって、積雪状態判定を行うことができる。
【0054】
の条件が考えられる。結局、積雪が継続する条件は、
条件1=We<0かつTf<TeかつδW>0かつWev>0かつZ≧1、
条件2=We<0かつTf>TeかつδW>0かつWev<0かつ|δW|>|Wev|かつ(Wev+δW)/We>0かつZ<1、
条件3=We>0かつTf<TeかつδW>0かつWev>0かつZ<1、
条件4=We>0かつTf>TeかつδW<0かつWev>0かつ|δW|>|Wev|かつ(Wev+δW)/We<0かつZ>1、
の4つの条件であり、条件1〜4のいずれかが満たされている場合は、積雪状態と判定する。
【0055】
このように、本発明では、路面への薬剤散布がない場合は、路面温度Teを用い、路面温度Teが時間経過によらず0℃を維持しているかどうか積雪状態を判定し、路面への薬剤散布がある場合は、路面温度の変化方向(熱量Weの正負)と、水の凝固点Tfに対する路面温度Teの高低と、蒸発熱Wevの正負と、積雪の融解または凝固による潜熱量δWの正負とから路面の積雪状態を判定する。
【0056】
次に、凍結状態の判定方法を述べる。熱的には凍結状態と乾燥状態とでは、ほぼ同じ挙動が生じる。即ち、凍結状態でも乾燥状態でも、積雪判定値Z=ほぼ1、かつ湿潤判定値Y=ほぼ0となる。凍結状態と乾燥状態とを区別するためには、現時点に至るまでの過去の路面状態の時系列を用いる。この時系列で前回の状態を基準にする。即ち、積雪判定値Z=ほぼ1、かつ湿潤判定値Y=ほぼ0であるとき、前回の状態が湿潤状態であれば、今回は乾燥状態に移行すると考える。また、積雪判定値Z=ほぼ1、かつ湿潤判定値Y=ほぼ0であるとき、路面温度Teが前回、前々回の路面温度Teとほぼ同じであれば遷移状態と考え、さらに路面への流入熱ΔWが負の値であれば冷却過程であると考え、冷却過程の遷移状態であれば、次回は凍結状態に移行すると考える。
【0057】
様々の路面状態において計算した判定値Y,Zをそれぞれ横軸、縦軸にとりプロットすると、各路面状態に対応した領域を図4のように示すことができる。この図に即して各路面状態の特長を次に述べる。
1)乾燥状態、凍結状態(定常状態)
Y=0,Z=1のポイントで示される。乾燥状態か凍結状態かの区別はトレンド(過去の路面状態の時系列)から判定することになる。
2)湿潤状態
Y=1,Z=0〜1(温度上昇過程のとき)の範囲か、Y=1,Z=1以上 (温度下降過程のとき)の範囲で示される。
3)積雪状態(薬剤なし)、凍結状態(遷移状態であって薬剤なし)
Z=0,Y=1以下(凝固過程のとき)の範囲か、Z=0,Y=1以上(融解過程のとき)の範囲で示される。
4)積雪状態(薬剤あり)、凍結状態(遷移状態であって薬剤あり)
薬剤を含んだ水の凝固点Tfと路面温度Teとの組み合わせによって、A〜Dの4つの領域に区分される。
【0058】
この4つの領域は、路面温度Teの時間的変化に対して図5のように区分される。即ち、路面温度Teが正の温度から負の温度に降下した後、凝固点Tfに至るまでは領域A、路面温度Teが凝固点Tfより下で降下すると領域B、路面温度Teが凝固点Tfより下で上昇すると領域C、路面温度Teが凝固点Tfより上で上昇し0度に至るまでは領域Dとなる。
【0059】
これまでに述べた路面状態の判定方法を実際に行った結果を図6に示す。対象期間は3日間で、その間に路面状態を目視観測した結果を図の上部に示してある。縦線縞模様を描いた期間は湿潤状態であり、その後の空白を描いた期間は乾燥状態であった。これに対して、潜熱相当の熱量比である湿潤判定値Yは、実線グラフで示したとおりに変化した。なお、図中WwはWevと同義である。この湿潤判定値Yに適切な閾値(ここでは0.1程度)を適用することで湿潤状態を判定することが可能である。
【0060】
本発明の路面状態推定方法を実施するためのシステム構成について図7を用いて説明する。このシステムは、対象となる道路4の近傍に設置された気象センサ1、路面下に埋設された光ファイバ2(光信号を温度分布値に変換する光ファイバ温度レーダを含む)、光ファイバ2により計測されたデータを信号線6を介して伝送する信号伝送装置3、気象センサ1により計測されたデータを信号線6を介して伝送する信号伝送装置5、計測データを受信する情報収集装置7、受信したデータに基づいて路面状態推定計算を行う路面状態推定装置8、その推定結果を出力する表示部9により構成される。
【0061】
気象センサ1は、電気的な出力が得られるものであれば、気象諸量の計測方式は特に限定されない。気象センサ1は、気温計、湿度計、日射計、雪雨量計、風速計、放射収支計などを総称したものであり、大気の温度Ta、相対湿度H、日射強度I、風速vなどを計測することができる。
【0062】
図示しないが路面上の塩分濃度を測定する塩分量計が設けられている。塩分量計で測定される塩分濃度によって、路面上の水分の凝固点Tfが計算される。また、塩分濃度によって、薬剤散布の有無を判定することができる。
【0063】
また、水膜厚hW (t)については、予めレーザレーダ等により路面粗さ(路面凹凸深さの平均値)を計測しておき、降雨時の雪雨量計の計測値が路面粗さ以下であれば雪雨量計の計測値を初期水膜厚hW 0とし、降雨時の雪雨量計の計測値が路面粗さを超えるときには、路面粗さを初期水膜厚hW 0とし、ある時間が経過した後の水膜厚hW (t)は式12で求める。
【0064】
路面温度Teは、前述した第2の方法で求めた路面への流入熱Weを用いて路面温度の変化量ΔTeが算出可能であるので、前回の路面温度TeにΔTeを加算することで今回の路面温度Teの値が求まる。ただし、システム起動時に限り、路面温度Teの初期値は路面温度が直接計測可能な温度計測器を使用して実測する。
【0065】
光ファイバ2の埋設位置は、図2の温度T1,T2,T3…の測定点のいずれかであり、実際の深さ位置は施工上の都合で決定することができる。
【0066】
信号伝送装置3、5は、無線伝送装置であってもよい。信号伝送装置3、5が無線伝送装置である場合の構成を図8に示す。図7と符号の同じ部材は同一部材である。図7との相違として、信号線6の代わりに受信アンテナ6が設置される。
【0067】
図7、図8のいずれの場合も、情報収集装置7は、気象センサ1及び光ファイバ2からの情報を受信し、データの種類や遅延時間等を考慮して必要なデータを路面状態推定装置8に与える。
【0068】
路面状態推定装置8は、これら入力データを用い、これまでに説明した計算式、手順に従い路面状態を判定する。
【0069】
【発明の効果】
本発明は次の如き優れた効果を発揮する。
【0070】
(1)長距離、広範囲での路面状態推定が従来より低コストで可能となる。
【図面の簡単な説明】
【図1】本発明の基本となる路面の熱収支の概念図である。
【図2】本発明において地中側から路面に流入する熱量を求めるための地中熱伝導の等価回路図である。
【図3】本発明で使用する地中側から路面に流入する熱量と地中温度変化量との関係図である。
【図4】本発明による判定値Y,Zと路面状態との関係図である。
【図5】本発明による路面温度変化と凝固点温度とによる路面状態判定区分を示した路面温度の時間変化図である。
【図6】本発明で実際に路面状態を判定したときの、熱量比及び路面状態の時間変化図である。
【図7】本発明の路面状態推定方法を実施するためのシステム構成の一例を示すブロック図である。
【図8】本発明の路面状態推定方法を実施するためのシステム構成の一例を示すブロック図である。
【符号の説明】
1 気象センサ(気象計)
2 光ファイバ(光ファイバ温度レーダ)
4 道路
8 路面状態推定装置
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for grasping road surface conditions such as wetness, snow accumulation, and freezing, and more particularly to a road surface state estimation method capable of automating road surface state estimation and local determination at low cost. It is.
[0002]
[Prior art]
In road traffic, when a road surface condition such as wetness, snow accumulation, or freezing occurs, a slip accident is likely to occur. For this reason, it is necessary to promptly detect the driver of the car by quickly detecting dangerous road surface conditions such as wetness, snow accumulation, and freezing. However, since it is difficult to constantly monitor a road over a long distance in terms of manpower and cost, a road surface state detection sensor is used as means for grasping such a road surface state.
[0003]
Conventional road surface condition detection sensors are mainly divided into two.
[0004]
The first group irradiates the road surface (road surface) with infrared rays or electromagnetic waves and measures the reflectance from the road surface. In this sensor, an infrared irradiation device, a light receiving device, and a signal processing device are installed in the vicinity of the road, and the road surface state is estimated using the fact that the intensity ratio between incident light and reflected light on the road varies depending on the road surface state.
[0005]
The second group includes sensors that measure the meteorological amount and road surface temperature near the road. For road surface temperature measurement, in addition to sensors for single point measurement such as thermocouples and infrared radiation thermometers, a method using an optical fiber temperature radar that is capable of multipoint measurement and suitable for measuring long-distance temperatures Has also been proposed. This sensor is used as a judgment material when a road management person estimates a road surface state based on past knowledge.
[0006]
[Problems to be solved by the invention]
In order to continuously grasp the road surface state along the longitudinal direction of the road using a sensor that irradiates infrared rays or electromagnetic waves, it is necessary to install a large number of sensors, which is costly.
[0007]
On the other hand, when measuring meteorological data and road surface temperature, it is low-cost because the meteorological observation site can be applied to a wide area and the optical fiber temperature radar can be installed over a long distance. . However, there is a problem that it is difficult for a road manager in charge of judging the road surface condition to have experience, and it is difficult to limit the area judged to be dangerous.
[0008]
Accordingly, an object of the present invention is to provide a road surface state estimation method that solves the above-described problems, automates road surface state estimation, and enables local determination at low cost.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention obtains the amount of heat (We) flowing into the road surface from the underground side based on the underground temperature measurement value measured by the optical fiber temperature radar buried under the road surface, and is installed near the road. Calculated from meteorological measurement values such as atmospheric temperature and solar radiation intensity measured by a meteorological meter (including a thermometer, hygrometer, solarimeter, snow rain gauge, anemometer, and radiation balance meter) and the underground temperature measurement value Alternatively, the amount of heat (Wa) flowing into the road surface from the atmosphere side is obtained based on the road surface temperature (Te) measured by a temperature measuring instrument such as the optical fiber temperature radar, and the road surface temperature (Te) and the meteorological amount measurement are obtained. The evaporation heat (Wev) due to the evaporation of moisture on the road surface is calculated based on the measured temperature value, relative humidity measurement value, and wind speed measurement value, and the amount of heat (We) flowing into the road surface from the ground and the atmospheric side to the road surface Difference in inflow heat (Wa) The wetness determination value (Y) is obtained from the evaporation heat (Wev), the wet state of the road surface is determined, and the ground temperature measurement value, the meteorological amount measurement value, and the wetness determination value (Y) are determined. Based on this, the road surface condition is estimated.
[0010]
When there is no chemical spraying on the road surface, the snow condition on the road surface is determined from the road surface temperature (Te) and the amount of change per hour (ΔTe), and when there is chemical spraying on the road surface, the road surface temperature ( Te) and the amount of change (.DELTA.Te) and may determine the snow conditions of the road surface because the heat of vaporization and (WEV) latent heat by melting or solidification of snow and (.delta.W).
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
[0015]
The principle of the present invention is to obtain the road surface state from the amount of heat flowing into the road surface obtained by two different methods. First, two calorific value calculation methods will be described.
[0016]
The first method is to install a meteorometer (including a thermometer, hygrometer, solarimeter, snow rain meter, anemometer, and radiation balance meter) near the road, and flow from these meteorological measurements into the road surface. The amount of heat is calculated.
[0017]
Here, the heat balance relation of the road surface is conceptually represented by the contents of FIG. The heat balance of the road surface can be classified into heat transfer from the atmosphere, atmospheric infrared radiation and road surface infrared radiation, absorption of solar radiation energy, and road internal heat transfer. In the present invention, the first method is used to calculate the sum Wa of the amount of heat flowing in from the upper side (atmosphere side) of the road excluding road internal heat transfer. Actually, there is heat transfer (latent heat transfer) associated with the phase change of moisture on the road surface, such as drying of wet road surfaces and melting of snow, but this is the purpose of the present invention to detect this amount of heat. Latent heat transfer is not considered.
[0018]
Wa = [heat transfer from the atmosphere] + [air infrared radiation and road surface infrared radiation] + [absorption of solar radiation energy]
The calculation formula for obtaining each of the above calories from the meteorological measurements is shown below.
(1) Heat transfer from the atmosphere Heat transfer Q1 from the atmosphere is a heat transfer caused by contact between the atmosphere and the road surface, and is obtained by the following equation.
[0019]
Q1 = h T × (Ta−Te) × A (Formula 1)
However, h T : Heat transfer coefficient Ta: Air temperature Te: Road surface temperature A: Area where heat is transmitted.
(2) Atmospheric infrared radiation and road surface infrared radiation Calculations of radiation Q2 from the atmosphere to the road surface and radiation Q3 from the road surface to the atmosphere Q3 are expressed by the following equations, respectively.
[0020]
Q2 = εa × σ × Ta 4 (Formula 2)
Q3 = εr × σ × Te 4 (Formula 3)
Where εa: atmospheric emissivity Ta: atmospheric temperature εr: road surface emissivity Te: road surface temperature σ: Stefan-Boltzmann constant.
(3) The solar energy Q4 absorbed on the road surface is calculated from the amount of solar radiation absorbed and the solar radiation absorption rate of the road surface.
[0021]
Q4 = (1-r) × I (Formula 4)
Where r: number of albeto on the road surface I: solar radiation intensity.
[0022]
Therefore,
Wa = Q1 + Q2 + Q3 + Q4
Thus, the sum Wa of the amount of heat flowing into the road surface from the atmosphere side can be obtained.
[0023]
The second method is based on the ground temperature measured by an optical fiber temperature radar embedded in the ground, and the amount of heat flowing into the road surface from the ground side (the amount of heat inflow due to road internal heat transfer excluded in the first method). It is what you want.
[0024]
Assume that the underground temperature T f measured with an optical fiber embedded in the road changes by ΔT f per Δt time when the amount of heat input ΔW from the atmosphere side to the road surface is ΔW * . In this case, [Delta] T f is the temperature change amount? T f0 of the optical fiber embedded position f in the case of [Delta] W = 0, the sum of the temperature change amount? T f at the time when the amount of heat from the atmosphere side to the road surface [Delta] W * has flowed Can be represented.
[0025]
ΔT f = δT f0 + δT f (Formula 5)
In Equation 5, the temperature change amount δT f0 at the optical fiber embedding position f when ΔW = 0 is obtained by the following method. The inflow heat W 2 from the underground to the road surface is obtained from the temperature distribution inside the underground. Here, a description will be given of a method in which the inflow heat W 2 from the underground to the road surface is obtained from the base temperature T 0 .
[0026]
The method using the base temperature T 0 uses that the temperature deep in the ground (depth of about several tens of meters) is almost constant throughout the year. If this temperature is the base temperature T 0 , The heat equivalent circuit from the road surface to the deep underground can be represented in FIG. That is, when there are ground temperature measurement points at a certain depth from the ground measurement points, there is a thermal resistance between each measurement point, and there is a heat capacity at each measurement point. Inflow heat W 1 from the atmosphere side to the road surface is input.
[0027]
The calorie calculation is performed every calculation step time Δt. When the underground is considered to have a hierarchical structure as shown in FIG. 2, the underground temperature T k in the k-th hierarchy is expressed by Equation 6 when the ground surface is first.
[0028]
Where R = Δh / λ T
C = ρ · C p · Δh D
However,
R: Thermal resistance of the layer C: Heat capacity Δh D of the layer: Step width λ T in the depth direction under the road λ: Thermal conductivity ρ in the layer ρ: Density of underground material in the layer C p : Area in the layer Per heat capacity
k : Subscript variable representing the hierarchy ( 1 , 2 , 3 , ...)
It is.
[0029]
Here, the boundary condition is expressed by Expression 7 and Expression 8.
[0030]
(T 1 −T 2 ) / R 1 = W 1 (Formula 7)
T n = T 0 (Formula 8)
By solving the equations 5 to 8, the temperature change amount δT f0 at the optical fiber embedded position f can be obtained.
[0031]
Next, as shown in FIG. 3, the amount of change ΔW in the inflow heat with respect to the road surface within a range in which the amount of heat flowing from the road surface to the optical fiber embedded position f and the accompanying temperature change amount of the optical fiber embedded position f can be approximated by a straight line. Is given as an arbitrary value ΔW z . At this time, the temporary temperature change ΔT fz at the optical fiber burying position f can be obtained by substituting ΔW z into W 1 of Equation 7 and solving Equations 6 to 8. The temperature change amount ΔT fz is the sum of the temperature change amount δT f0 at the optical fiber embedding position f when ΔW = 0 and the temperature change amount δT fz given by the heat amount ΔW z flowing into the road surface arbitrarily determined. Can be represented.
[0032]
ΔT fz = δT f0 + δT fz (Formula 9)
Therefore, since the temperature change amount δT f0 and the temporary temperature change amount ΔT fz at the optical fiber embedding position f when W = 0 are obtained as described above, the temperature change amount δT fz is obtained.
[0033]
Moreover, since the linear relationship shown in FIG. 3 is assumed, the relationship of Formula 10 is established.
[0034]
δT f / ΔW * = δT fz / ΔW (Formula 10)
From Expression 9 and Expression 10, Expression 11 for obtaining the amount of heat ΔW * flowing into the road surface is obtained.
[0035]
ΔW * = (ΔW z / δT fz ) · δT f (Formula 11)
In Equation 11, δT f is the temperature change amount δT fz at the actual optical fiber embedding position f, and ΔW z is a value that can be arbitrarily determined. The change amount ΔW * can be calculated. The amount of heat ΔW * obtained in this way is the inflow heat We from the underground side to the road surface.
[0036]
The underground thermal constant required for the above calculation is constant depending on the composition of the underground material, so if it is measured in advance using a heat flow meter, the inflow heat We from the underground side to the road surface can be accurately measured. Can be calculated.
[0037]
Next, a method for estimating the road surface state using the heat quantity Wa obtained by the first method and the heat quantity We obtained by the second method will be described below.
[0038]
First, a method for determining the wet state of the road surface using the heat amount Wa and the heat amount We obtained by the first method will be described. Assuming that the moisture thickness on the road surface is h W (t), the relationship between the moisture thickness h W (t) and the evaporation heat Wev (t) can be expressed by Equation 12.
[0039]
h W (t) = h W 0−Wev (t) / λ W (Equation 12)
Here, Wev (t) is a value obtained from the meteorological amount according to Equation 13.
[0040]
However,
h W 0: thickness of water accumulated on the road surface immediately after rain λ W : latent heat of evaporation α, β: constant v: wind speed H: relative humidity Te: road surface temperature Ta: air temperature P (Te): water content at temperature Te Saturated water vapor pressure P (Ta): Saturated water vapor pressure of water at temperature Ta.
[0041]
As described above, in the present invention, the evaporation heat Wev due to the evaporation of moisture on the road surface is obtained by measuring the road surface moisture thickness h W 0, the wind speed v, the road surface temperature Te, the relative humidity H, and the temperature Ta (including some estimated values). And known quantities.
[0042]
In the wet state, the following relational expression is established among the inflow heat Wa from the atmosphere side to the road surface, the inflow heat We from the ground (underground side) to the road surface, and the evaporation heat Wev.
[0043]
Wa-We = Wev (Formula 14)
Here, Expression 15 is introduced as the wetness determination value Y.
[0044]
Y = (Wa-We) / Wev (Formula 15)
Since the wetness determination value Y is theoretically 1 in the wet state and 0 in the dry state and the frozen state, the presence or absence of wetness can be determined by monitoring this value. That is, in the present invention, the wetness determination value Y is obtained using the inflow heat Wa from the atmosphere side to the road surface, the inflow heat We from the underground side to the road surface, and the evaporation heat Wev due to the evaporation of moisture on the road surface. The wet condition of the road surface is determined from the value Y.
[0045]
Next, a method for determining the snow cover state will be described. The conditions for determining the snow cover state differ depending on whether or not there is a chemical spray on the road surface. When there is no chemical spraying on the road surface, it is possible to easily determine the snowy state based on the following determination conditions.
[0046]
Te = 0 ° C and ΔTe = 0 ° C
However,
ΔTe: The amount of change in road surface temperature per measurement time.
[0047]
As described above, when there is no chemical spraying on the road surface, it is possible to determine the snowy state by using the road surface temperature Te and maintaining the road surface temperature Te at 0 ° C. regardless of the passage of time.
[0048]
In the case where there is a possibility of chemical spraying, first, the snow accumulation determination value Z is defined by Expression 16.
[0049]
Z = ΔTe / ΔTc (Formula 16)
However,
ΔTe: Increase in road surface temperature per measurement time (measured value)
ΔTc: Increase in road surface temperature when the incoming heat Wa from the atmosphere flows (calculated value)
It is. ΔTe and ΔTc, which are changes in the road surface temperature, are approximately proportional to the inflow heat We and Wa to the road surface, respectively. Due to these proportional relationships (ΔTe is proportional to We and ΔTc is proportional to Wa), ΔTe / ΔTc = We / Wa is substantially satisfied. Therefore,
Z = We / Wa (Formula 16 ')
It can be expressed as.
[0050]
Further, considering the wetness determination value Y used for the determination of the wet state, if the amount of latent heat used for melting or solidifying snow is δW,
The wet determination value Y is Y = 1 or more in the snow-covered state, Y = 1 or less when the melting process (δW is negative), and the solidification process (δW is positive).
[0051]
Next, when the difference between the inflow heat Wa from the atmosphere side to the road surface and the inflow heat We from the underground side to the road surface is ΔW,
It becomes. Here, δW is positive in the melting process and negative in the solidification process.
[0052]
From Equation 16 ′ and Equation 18, the snow cover determination value Z can be expressed as follows.
[0053]
The snow condition determination can be performed from Equation 19 under the following conditions.
[0054]
The following conditions can be considered. After all, the conditions for continued snowfall are:
Condition 1 = We <0 and Tf <Te and δW> 0 and Wev> 0 and Z ≧ 1
Condition 2 = We <0 and Tf> Te and δW> 0 and Wev <0 and | δW |> | Wev | and (Wev + δW) / We> 0 and Z <1,
Condition 3 = We> 0 and Tf <Te and δW> 0 and Wev> 0 and Z <1,
Condition 4 = We> 0 and Tf> Te and δW <0 and Wev> 0 and | δW |> | Wev | and (Wev + δW) / We <0 and Z> 1,
When any one of the conditions 1 to 4 is satisfied, it is determined that the snow is in a snowy state.
[0055]
As described above, in the present invention, when there is no chemical spraying on the road surface, the road surface temperature Te is used to determine whether or not the road surface temperature Te is maintained at 0 ° C. regardless of the passage of time. When there is a chemical spray, the change direction of the road surface temperature (positive or negative of the heat amount We), the level of the road surface temperature Te with respect to the freezing point Tf of water, the positive or negative of the evaporation heat Wev, and the positive or negative of the latent heat amount δW due to melting or solidification of snow. And determine the snow condition on the road.
[0056]
Next, a method for determining the frozen state will be described. Thermally, almost the same behavior occurs between the frozen state and the dried state. That is, in both the frozen state and the dry state, the snow accumulation determination value Z = 1 and the wetness determination value Y = 0. In order to distinguish between a frozen state and a dry state, a time series of past road surface conditions up to the present time is used. This time series is based on the previous state. That is, when the snow accumulation determination value Z = approximately 1 and the wetness determination value Y = approximately 0, if the previous state is a wet state, it is considered that the current state is shifted to the dry state. Further, when the snow cover judgment value Z = 1 and the wet judgment value Y = 0, the road surface temperature Te is considered to be a transitional state if the road surface temperature Te is substantially the same as the previous and previous road surface temperature Te, and further the inflow heat to the road surface If ΔW is a negative value, it is considered that the cooling process is in progress, and if it is in a transition state of the cooling process, it is considered that the next time it will shift to the frozen state.
[0057]
When the determination values Y and Z calculated in various road surface conditions are plotted on the horizontal axis and the vertical axis, respectively, a region corresponding to each road surface state can be shown as shown in FIG. The features of each road surface state will be described next with reference to this figure.
1) Dry state, frozen state (steady state)
This is indicated by the points Y = 0 and Z = 1. The distinction between a dry state and a frozen state is determined from a trend (a time series of past road surface conditions).
2) The wet state is Y = 1, Z = 0 to 1 (during the temperature rising process), or Y = 1, Z = 1 or more (during the temperature falling process).
3) Snow condition (no drug), frozen state (transition state, no drug)
Z = 0, Y = 1 or less (during solidification process) or Z = 0, Y = 1 or more (during melting process).
4) Snow cover state (with drug), frozen state (transition state with drug)
According to the combination of the freezing point Tf of the water containing the medicine and the road surface temperature Te, the water is divided into four regions A to D.
[0058]
These four regions are divided as shown in FIG. 5 with respect to temporal changes in the road surface temperature Te. That is, after the road surface temperature Te drops from a positive temperature to a negative temperature, until the solidification point Tf is reached, the region A, and when the road surface temperature Te falls below the freezing point Tf, the region B, the road surface temperature Te falls below the freezing point Tf. If it rises, it will become the area | region D until the area C and the road surface temperature Te rise above the freezing point Tf and reach 0 degree.
[0059]
FIG. 6 shows the result of actually performing the road surface condition determination method described so far. The target period is 3 days, and the results of visual observation of the road surface during that period are shown in the upper part of the figure. The period during which the vertical stripe pattern was drawn was wet, and the period during which the blank was drawn was dry. On the other hand, the wetness determination value Y, which is a heat quantity ratio corresponding to latent heat, changed as shown by the solid line graph. In the figure, Ww is synonymous with Wev. It is possible to determine the wet state by applying an appropriate threshold value (here, about 0.1) to the wet determination value Y.
[0060]
A system configuration for carrying out the road surface state estimation method of the present invention will be described with reference to FIG. This system includes a weather sensor 1 installed in the vicinity of a target road 4, an optical fiber 2 embedded under a road surface (including an optical fiber temperature radar that converts an optical signal into a temperature distribution value), and an optical fiber 2. A signal transmission device 3 for transmitting the measured data via the signal line 6, a signal transmission device 5 for transmitting the data measured by the weather sensor 1 via the signal line 6, an information collecting device 7 for receiving the measurement data, The road surface state estimation device 8 performs road surface state estimation calculation based on the received data, and the display unit 9 outputs the estimation result.
[0061]
As long as the weather sensor 1 can obtain an electrical output, the measuring method of various weather quantities is not particularly limited. The weather sensor 1 is a collective term for a thermometer, a hygrometer, a solar radiation meter, a snow and rain gauge, an anemometer, a radiation balance meter, etc., and measures the atmospheric temperature Ta, relative humidity H, solar radiation intensity I, wind speed v, etc. can do.
[0062]
Although not shown, a salinity meter for measuring the salinity concentration on the road surface is provided. The freezing point Tf of moisture on the road surface is calculated by the salinity concentration measured by the salinity meter. Moreover, the presence or absence of chemical spraying can be determined by the salinity concentration.
[0063]
Further, for the water film thickness h W (t), the road surface roughness (average value of the road surface unevenness depth) is measured in advance by a laser radar or the like, and the measured value of the snow rain gauge at the time of raining is less than the road surface roughness. Then, the measured value of the snow rain gauge is the initial water film thickness h W 0, and when the measured value of the snow rain gauge at the time of rainfall exceeds the road surface roughness, the road surface roughness is set as the initial water film thickness h W 0. The water film thickness h W (t) after the elapse of time is obtained by Expression 12.
[0064]
Since the road surface temperature Te can be calculated by using the inflow heat We into the road surface obtained by the second method described above, the road surface temperature change amount ΔTe can be calculated. Therefore, by adding ΔTe to the previous road surface temperature Te, The value of the road surface temperature Te is obtained. However, only when the system is activated, the initial value of the road surface temperature Te is actually measured using a temperature measuring device capable of directly measuring the road surface temperature.
[0065]
The buried position of the optical fiber 2 is one of the measurement points of the temperatures T1, T2, T3,... In FIG. 2, and the actual depth position can be determined for the convenience of construction.
[0066]
The signal transmission devices 3 and 5 may be wireless transmission devices. FIG. 8 shows a configuration when the signal transmission devices 3 and 5 are wireless transmission devices. The same members as those in FIG. 7 are the same members. As a difference from FIG. 7, a receiving antenna 6 is installed instead of the signal line 6.
[0067]
7 and 8, the information collecting device 7 receives information from the weather sensor 1 and the optical fiber 2, and takes necessary data in consideration of the type of data and delay time, etc. Give to 8.
[0068]
The road surface state estimation device 8 uses these input data to determine the road surface state according to the calculation formulas and procedures described so far.
[0069]
【The invention's effect】
The present invention exhibits the following excellent effects.
[0070]
(1) Long-distance and wide-range road surface state estimation is possible at a lower cost than before.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a heat balance of a road surface that is the basis of the present invention.
FIG. 2 is an equivalent circuit diagram of underground heat conduction for determining the amount of heat flowing into the road surface from the underground side in the present invention.
FIG. 3 is a relationship diagram between the amount of heat flowing into the road surface from the underground side used in the present invention and the amount of underground temperature change.
FIG. 4 is a relationship diagram between determination values Y and Z according to the present invention and road surface conditions.
FIG. 5 is a time change diagram of road surface temperature showing road surface state determination classification based on road surface temperature change and freezing point temperature according to the present invention.
FIG. 6 is a time change diagram of a heat quantity ratio and a road surface state when the road surface state is actually determined in the present invention.
FIG. 7 is a block diagram showing an example of a system configuration for carrying out the road surface state estimation method of the present invention.
FIG. 8 is a block diagram showing an example of a system configuration for carrying out the road surface state estimation method of the present invention.
[Explanation of symbols]
1 Weather sensor (meteorometer)
2 Optical fiber (optical fiber temperature radar)
4 Road 8 Road surface condition estimation device

Claims (2)

路面下に埋設した光ファイバ温度レーダにより計測した地中温度計測値に基づき地中側から路面に流入する熱量(We)を求め、
道路近傍に設置した気象計(気温計、湿度計、日射計、雪雨量計、風速計、放射収支計を含む)により計測した大気の温度、日射強度などの気象量計測値と、前記地中温度計測値から算出し、あるいは前記光ファイバ温度レーダなどの温度計測器で計測した路面温度(Te)とに基づき大気側から路面に流入する熱量(Wa)を求め、
前記路面温度(Te)と、前記気象量計測値の気温計測値、相対湿度計測値、風速計測値とに基づき路面上の水分の蒸発による蒸発熱(Wev)を求め、
地中側から路面に流入する熱量(We)と大気側から路面に流入する熱量(Wa)の差と、前記蒸発熱(Wev)とから湿潤判定値(Y)を求めて、路面の湿潤状態を判定し、前記地中温度計測値及び前記気象量計測値と、前記湿潤判定値(Y)とに基づき路面の状態を推定することを特徴とする路面状態推定方法。
Obtain the amount of heat (We) flowing into the road surface from the underground side based on the underground temperature measurement value measured by the optical fiber temperature radar buried under the road surface ,
Meteorological measurements such as atmospheric temperature and solar radiation intensity measured by a meteorometer (including a thermometer, hygrometer, solarimeter, snow rain gauge, anemometer, and radiation balance meter) installed near the road, and the underground Calculated from the temperature measurement value, or based on the road surface temperature (Te) measured by a temperature measuring instrument such as the optical fiber temperature radar , to determine the amount of heat (Wa) flowing into the road surface from the atmosphere side,
Based on the road surface temperature (Te) and the air temperature measurement value, the relative humidity measurement value, and the wind speed measurement value of the meteorological measurement value, a heat of evaporation (Wev) due to evaporation of moisture on the road surface is obtained,
A wetness determination value (Y) is obtained from the difference between the amount of heat (We) flowing into the road surface from the underground side and the amount of heat (Wa) flowing into the road surface from the atmosphere side and the heat of evaporation (Wev), and the wet state of the road surface And estimating the road surface state based on the ground temperature measurement value, the meteorological quantity measurement value, and the wetness determination value (Y) .
路面への薬剤散布がない場合は、前記路面温度(Te)とその時間当たりの変化量(ΔTe)とから路面の積雪状態を判定し、路面への薬剤散布がある場合は、前記路面温度(Te)と前記変化量(ΔTe)と上記蒸発熱(Wev)と積雪の融解または凝固による潜熱量(δW)とから路面の積雪状態を判定することを特徴とする請求項に記載の路面状態推定方法。When there is no chemical spraying on the road surface, the snow condition on the road surface is determined from the road surface temperature (Te) and the amount of change per hour (ΔTe), and when there is chemical spraying on the road surface, the road surface temperature ( The road surface condition according to claim 1 , wherein a snow condition on the road surface is determined from Te), the amount of change (ΔTe) , the heat of evaporation (Wev), and the latent heat quantity (δW) due to melting or solidification of snow. Estimation method.
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