JP3555244B2 - Anti-skid control device - Google Patents

Description

となり、路面μの変化量（＝μ_２ −μ_１ ）は、車輪加速度とホイールシリンダ圧の変化量ΔＰｗにより算出されることが分かる（図１１参照）。
【００４４】
かくて、前記アンチスキッドアクチュエータｉ（図１図示のＡＢＳ油圧回路）の特性も活用して、路面μの変化は、その時間間隔内ではＷ等の要素部分は一定で変化しない（あるいは、短時間内ではほぼ一定で実質変化しない）とする条件の下、上記の他の変化パラメータ値を知ることで、これらに応じたものとして式４に基づき演算されることとなる。
一方、車輪のスリップ量は、例えば、従来既知の方法同様に車輪速より算出され、時間当たりのスリップ量の変化量も算出されるものである（同図参照）。
【００４５】
そして、路面μの変化量、スリップ量の変化量が得られると、このスリップ量の変化量と路面μの変化量よりスリップ変化に対する路面μの変化が分かり、その履歴をみればμ−Ｓ特性が推定できる（同図参照）。
また、μ−Ｓ特性が分かればμピークをとるスリップ量が推定可能となり、アンチスキッド制御は車輪のスリップをそのスリップ量に合わせるように制御（可変制御））すればよくなる。つまり、実際の路面において、その路面μ特性に応じた最適なスリップ量に車輪を制御できるようになる（路面μ推定手段ｆ、制御内容変更手段ｇ）。
【００４６】
制動時の路面μの状態が、その制動場面の路面いかんでたとえ大きく異なっても、以上に原理を示したような路面μ推定、制御変更を伴う本アンチスキッド制御であれば、常に、路面μに応じた最適な制御が可能で、しかも、廉価なシステムを用いても充分なアンチスキッド性能を発揮することができる。
【００４７】
更にまた、上記式４中のホイールシリンダ圧の変化量ΔＰｗ（同右辺分子中のｋ・ｒ・Ｒ値に対する乗算値（＝Ｐｗ_２ −Ｐｗ_１ ）の値として、前記駆動パルス・デューティ比演算手段ｅ（コントローラ５０）によってなされる、増圧と減圧の組み合わせの態様により制御時の制御量推定を行うことで所定周期ごとの電磁弁駆動パルスのデューティ比を演算する場合におけるその演算処理過程で算出され、用いられる当該推定増圧量値が適用可能で、こうするときは、別途新たにホイールシリンダ圧センサを付加しないで済む等のことは勿論、かかる絞りによる緩増圧効果利用した１ｃｈ当たり１電磁弁による廉価なＡＢＳシステムとの組み合わせの効果はより大であり、この点でも、廉価なシステムで路面μに応じた最適な制御を行わせ得て、充分なアンチスキッド性能を発揮させられ、その実効性は一層上がるものとなる。
【００４８】
図４乃至図６は、コントローラ５０により実行される、上記の駆動パルス・デューティ比演算処理、及び路面μ推定並びに制御内容変更処理を含むアンチスキッド制御プログラムの一例のフローチャートである。この処理は、図示せざるオペレーティングシステムで一定時間毎の定時割り込みによって遂行される。
また、図７，８は、それぞれ増圧量推定、減圧量推定のため用いるアクチュエータモデルの一例を示す特性図であり、その特性データについては、コントローラ５０の記憶回路に予め格納しておくことができる。また、図９乃至図１２は、本制御内容の説明に供する図である。
【００４９】
以下、これらの図も参照して説明するに、図４の制御プログラムは、車輪速の読込み、車輪加速度の算出、疑似車体速の算出、緩増圧中か否かの判別、路面μ変化量（Ｋｓ）の算出、μピーク推定、Ｋｓ＝Ｋｓｏの設定、目標スリップ率（Ｓ^＊ ）の算出、目標増減圧量（ΔＰ^＊ ）演算、ソレノイドバルブ・駆動パルスデューティ比演算ルーチン、及び駆動パルス出力の各処理（ステップＳ１００〜Ｓ１１０）からなる。本実施例では、車輪速のＦ／ＢによるＰＤ制御にてＡＢＳ制御するものとしている。
【００５０】
図４において、まず、ステップＳ１００では、車輪速センサ５１〜５４からの信号に基づき、各車輪速Ｖｗｉ（ｉ＝１〜４）を読み込む。
次に、ステップＳ１０１において車輪速Ｖｗｉより車輪加速度Ｖｗｄを算出する。本実施例では、例えば３０ｍｓｅｃ間の速度差から求めることにする。
【００５１】
続くステップＳ１０２では、疑似車体速Ｖｉを算出する。
本実施例では、通常のＡＢＳで用いられる方法でＶｉを算出することにする。即ち、ここでは、各輪の車輪速Ｖｗにフィルタをかけ、より車体速度に近い値Ｖｗｆｉ（ｉ＝１〜４）を各輪で算出し、制動時／非制動時などの条件により、各Ｖｗｆｉから最も大きいものを選択するなどして最も車体速度に近いＶｗｆ（車体速中間値と呼ぶ）を算出し、更にこのＶｗｆをもとに疑似車体速度Ｖｉを求めることとする。
【００５２】
次に、本プログラム例では、ステップＳ１０２に続くステップＳ１０３にてホイールシリンダ圧（Ｗ／Ｃ圧）が緩増圧中か否かにより、路面μを推定するか否かを選択する。
本実施例では、該チェックに当たっても、後述するＷ／Ｃ圧の制御信号ＤＴ（ＤＴは、パルス出力周期Ｔ、例えば５０ｍｓｅｃ中のアウトレットバルブを閉じている時間であって、例えばＤＴ＝１０ｍｓｅｃなどとして定義する）を有効に利用し、活用することができ、かかるＤＴ値が、パルス出力周期Ｔに等しいか否か、即ちＤＴ＝Ｔが成立するか否かにより選択する。ＤＴ＝Ｔの時は、アウトレットバルブは閉じっぱなしになるため、周期Ｔの間は緩増圧中となる。
【００５３】
しかして、ステップＳ１０３のチェックの結果、ＤＴ＝Ｔの時は、ステップＳ１０４以下に進み、路面μの変化量を算出する等する一方、ＤＴ≠Ｔの時はステップＳ１１０に進み、スリップ率に対する路面μの変化量Ｋｓを或る設定所期値Ｋｓｏとし、その後ステップＳ１０６の処理に進む。
【００５４】
ステップＳ１０４においては、スリップ率に対する路面μの変化量Ｋｓを算出する。
本実施例では、一定時間毎の定時割り込みごとに算出されている車輪速Ｖｗと車輪加速度Ｖｗｄと擬似車体速度Ｖｉ、及び緩増圧中のホイールシリンダ圧変化量ΔＰｗ／ｃ（本プログラム例では、後述するソレノイドバルブ駆動パルス・デューティ比演算ルーチン内で算出されることとなるＷ／Ｃ圧（Ｐｗ／ｃｉ）の増圧量ΔＰｉｎｃ値（前回値）が用いられる）より路面μ変化量を算出する。
【００５５】
まず、前述の原理説明に準じ、以下の計算により一定時間内の路面μ変化量（＝μ_２ −μ_１ ）を求める（図３，１１）。
【数５】
Ｉ・（ｄ／ｄｔ）ω_１ ＝μ_１ ・Ｗ・Ｒ−ｋ・Ｐｗ／ｃ_１ ・ｒ ・・・５
【数６】
Ｉ・（ｄ／ｄｔ）ω_２ ＝μ_２ ・Ｗ・Ｒ−ｋ・Ｐｗ／ｃ_２ ・ｒ ・・・６
（ここで、Ｗ，Ｒ，ｋ，ｒは、ほぼ一定とみなす）
【数７】

【００５６】
次に、以下の計算により一定時間内のスリップ率変化量（＝Ｓ_２ −Ｓ_１ ）を、車輪速Ｖｗと擬似車体速度Ｖｉより求める（図１１）。
【数８】

以上より、スリップ率に対する路面μの変化量Ｋｓ＝（μ_２ −μ_１ ）／（Ｓ_２ −Ｓ_１ ）が求められる。
【００５７】
次に、本プログラム例では、続くステップＳ１０５においてμピークを推定する。
本実施例では、上記ステップＳ１０４で求めた路面μ変化量Ｋｓが負の値（または前記所定の設定値Ｋｓｏ以下）になる時のスリップ率Ｓｏの時のμをμピークと推定する。
【００５８】
図１１は、μピーク推定の原理も表し、ここでは、比較的に乾燥したドライ路とかなり低μ値のウエット路の場合の異なる２種のμ−Ｓ特性が例示されており、かつ、それぞれで最大μのスリップ率も図示のように異なるものとなっている。
図で、特性上、例えば各スリップ率Ｓ_１ ，Ｓ_２ ，Ｓ_３ ，Ｓ_４ 点、及びそれらに対応する路面μのポイントに注目すると、上記ドライ路特性の場合、μピークは、スリップ率Ｓ_１ 〜Ｓ_２ ，Ｓ_２ 〜Ｓ_３ ，Ｓ_３ 〜Ｓ_４ の範囲のうち、スリップ率Ｓ_３ 〜Ｓ_４ 部分にあることが分かり、路面μ変化量Ｋｓ値は、スリップ率Ｓ_２ 〜Ｓ_３ とスリップ率Ｓ_３ 〜Ｓ_４ との間では、符号が転換しており（ここでは、前者の部分は（μ_３ −μ_２ ）／（Ｓ_３ −Ｓ_２ ）でＫｓ＞０であるが、後者の部分は（μ_４ −μ_３ ）／（Ｓ_４ −Ｓ_３ ）でＫｓ＜０となり、負の値を示す）、最大μはそのスリップ率Ｓ_３ 〜Ｓ_４ 範囲にあることが分かる。
【００５９】
一方、上記ウエット路特性の場合、上記ドライ路の特性に比し、各スリップ率Ｓ_１ ，Ｓ_２ ，Ｓ_３ ，Ｓ_４ 点に対応する路面μがそれぞれ図示の如くの値μ_１ ′，μ_２ ′，μ_３ ′，μ_４ ′である結果、μピークは、低スリップ率側にずれた特性のものとなっており、スリップ率Ｓ_２ 〜Ｓ_３ 部分にあるが、このような場合も、上記に準じ得られる路面μ変化量Ｋｓ値を用いることで、最大μはそのスリップ率Ｓ_２ 〜Ｓ_３ 範囲にあることが分かり、μピーク推定は同様に行われる。
従って、実際の制動場面での路面が、これらいずれのμ−Ｓ特性であっても、その路面μの状態に対応して、スリップ率に対する路面μの変化の度合いを示すＫｓ値をみることで、μピークのスリップ率の推定ができる。
そして、このような推定が行えると、基本的には、ＡＢＳ作動時、常に、実際のスリップ率がその該当する対応μ−Ｓ特性上の最大μのスリップ率近傍となるように、ＡＢＳ制御を行わせることができる。
【００６０】
図４に戻り、ステップＳ１０６に進むと、本ステップでは、目標スリップ率Ｓ^＊ を算出する。本実施例では、ステップＳ１０５で求めたμピーク時のスリップ率Ｓｏより目標スリップ率Ｓ^＊ ＝ｍｉｎ（Ｓｏ，Ｓｏｌｍｉｔ）として求める。ここで、μピークがスリップ率の非常に大きなところにある路面への対策として（このような路面では、前後力は発生するが横力が小さくなり過ぎ、舵が効きにくくなる傾向を呈する）、目標スリップ率Ｓ^＊ を算出する際にＳｏに最大値の制限Ｓｏｌｉｍｔを設けたものである。
従って、ここでは、かかるリミットチェック処理も含められ、その結果、上記μピーク推定で得られることとなる値Ｓｏ（実際のＡＢＳ作動時のその対応路面に応じ、推定μ−Ｓ特性ごと（例えば、図１１のそれぞれの特性ごと）、異なる値を示すこととなる可変値）と、上記値Ｓｏｌｍｉｔ（所定の固定値）との２つのうち、いずれか小さい方の値のものが、目標値Ｓ^＊ として選択されることなる（具体的には、ステップＳ１０５で得られる値Ｓｏが値Ｓｏｌｍｉｔを下まっわていれば、そのまま値Ｓｏが、また値Ｓｏが値Ｓｏｌｍｉｔを越えることとなる場合にあってはその値Ｓｏに代え値Ｓｏｌｍｉｔが、それぞれ、選ばれるようにすることができる）。
μピーク推定に基づく目標スリップ率の設定をする態様で本制御を実施するとき、このようにもすると、更に、よりきめ細かな制御が可能となる。
【００６１】
次に、ステップＳ１０７にて、目標増減圧量ΔＰ^＊ を算出する。
本実施例では、アンチスキッド制御は、上述したように例えばＰＤ制御とする。
簡単に説明すると、上記ステップＳ１００〜Ｓ１０２で得られた各輪の車輪速Ｖｗと疑似車体速Ｖｉと車輪加速度Ｖｗｄより、次式９に従って目標増減圧量ΔＰ^＊ を算出する。
【数９】
ΔＰ^＊ ＝ｋｐ×（Ｖｗ^＊ −Ｖｗ）＋ｋｄ×（Ｖｗｄ^＊ −Ｖｗｄ） ・・・９
【００６２】
ここに、ｋｐ，ｋｄは、それぞれ制御ゲイン（比例制御ゲイン，微分制御ゲイン）であり、走行状態に応じて変更される。
また、Ｖｗ^＊ は、車輪速の目標値であり、ここでは、上記ステップＳ１０６で求めた目標スリップ率の値Ｓ^＊ を用いて、例えばＶｗ^＊ ＝Ｖｉ×Ｓ^＊ として求める。
また、Ｖｗｄ^＊ は、車輪加速度の目標値であり、ここでは例えばＶｗｄ^＊ ＝１．２ｇなどとして求める。
【００６３】
こうして、μピークをとるスリップ率Ｓｏに着目しこれを推定して、それに合わせて目標値Ｖｗ^＊ が設定、変更されることでＡＢＳ制御の目標増減圧量ΔＰ^＊ が適切に設定される。そして、以下の処理でアウトレットバルブに対するデューティ比制御が実行されていくときは、常に、路面μがピークとなるスリップを目標に制御可能ともなる。
【００６４】
即ち、上述の如くに目標増減圧量ΔＰ^＊ を演算したら、該算出値ΔＰ^＊ を用い（図６ステップＳ２０９参照）、次のステップＳ１０８において、アウトレットバルブ１３〜４３として各チャンネルに設けられている電磁弁への駆動パルス出力処理（ステップＳ１０９）のため、ソレノイドバルブ駆動パルス・デューティ比を演算し、これに基づき、ステップＳ１０９実行ごと駆動パルスを出力することにより、アウトレットバルブのデューティ制御を実行する。
上記ソレノイドバルブ駆動パルス・デューティ比演算ルーチンの一例を示したたものが、図５，６である。
本実施例では、常に増圧した後減圧することで該当チャンネルのＷ／Ｃ圧を制御するものとする。
【００６５】
図５において、まず、ステップＳ２００にてマスターシリンダ圧を推定する。本実施例では、ブレーキＳＷ５５のｏｎ信号にて、或る傾きでＭ／Ｃ圧を立ち上げ、例えば最大Ｍ／Ｃ圧を１６ＭＰａとし、最大Ｍ／Ｃ圧まで上昇するものとする。ここで、更に精度を向上させるために、ＡＢＳ作動中は、その減速度などに応じてＭ／Ｃ圧を修正するなどとしてもよい。
次に、ステップＳ２０１にてＷ／Ｃ圧（Ｐｗ／ｃｉ）の推定を行う。
本実施例では、後述する方法で算出された前回のパルスデューティ比より、Ｗ／Ｃ圧を推定するものとする（次のステップ以降参照）。
【００６６】
そして、ステップＳ２０２以降でソレノイドバルブ駆動パルス・デューティ比を算出する。
詳しく説明すると、まず、ステップＳ２０２でパルス・デューティ比ＤＴの初期値を設定する。
本プログラム例では、ＤＴ＝０とする。
なお、前述もしたが、ＤＴは、パルス出力周期Ｔ（例えばＴ＝５０ｍｓｅｃ）中のアウトレットバルブを閉じている時間を表し、例えば、ＤＴ＝１０ｍｓｅｃなどとして定義するものであり、よって、この場合は、上記初期値のとき、つまり、ＤＴ＝０の場合はフル減圧（Ｔ＝５０ｍｓｅｃの全期間、開位置をとり、バルブは開きっぱなし）ということになる。そしてまた、ＤＴ≠０のとき、例えばＤＴ＝１０ｍｓｅｃの場合なら、これは、上記周期Ｔ＝５０ｍｓｅｃ中、１０ｍｓｅｃの間はアウトレットバルブは閉位置をとり、４０ｍｓｅｃの間は開位置をとることを意味することになる。
【００６７】
次に、ステップＳ２０３では、値ＤＴが０か否かを判断する。ここで、ＤＴ＝０の場合は、上記のようにフル減圧なので、ステップＳ２０４に進み、増圧量ゼロ、即ちΔＰｉｎｃ＝０とする。しかして、ステップＳ２０６へ処理を進める。これに対し、ＤＴ≠０（ＤＴ＝Ｔを含む）の場合は、増圧も（もしくは増圧（緩増圧）のみ）行うのでステップＳ２０５に進み、増圧量の推定を行う。
【００６８】
この処理内容は、次のようである。
即ち、ステップＳ２０５では、例えば図７のようなアクチュエータモデル（特性）により、Ｍ／Ｃ圧と現在のＷ／Ｃ圧とデューティ比ＤＴより増圧量ΔＰｉｎｃを算出する。かかる値ΔＰｉｎｃは、次のステップＳ２０６、及び後述のステップＳ２０９での演算に適用されるものであるが、本例では、例えばＤＴ＝５ｍｓｅｃの時の特性を基本として、そのアクチュエータモデル（特性）を持ち、Ｍ／Ｃ圧と現在のＷ／Ｃ圧よりＤＴ＝５ｍｓｅｃの時の増圧量ΔＰｉｎｃを算出し、例えばＤＴ＝１０ｍｓｅｃの時は、その２倍とするなどしてモデルの簡略化を行っている。
【００６９】
ここで、本実施例では、更には、ＤＴ＝Ｔの時の増圧量ΔＰｉｎｃが、次回ループでの路面μ推定に用いられるΔＰｗ／ｃ値（前記式７）となる。
本例にあっては、路面μ推定に使用されるＷ／Ｃ圧の変化量は、こうして上記のＤＴ＝Ｔのときの推定増圧量がそのまま利用できる。
【００７０】
次にステップＳ２０６では、Ｗ／Ｃ圧Ｐｗ／ｃｉとステップＳ２０５にて推定された増圧量ΔＰｉｎｃとから増圧後のＷ／Ｃ圧Ｐｗ／ｃｉＭ（推定中間値と呼ぶ）を推定する。
つまり、
【数１０】
増圧後のＷ／Ｃ圧Ｐｗ／ｃｉＭ＝Ｐｗ／ｃｉ＋ΔＰｉｎｃ ・・・１０
より増圧後のＷ／Ｃ圧を算出する。
【００７１】
次に、ステップＳ２０７では、次式１１より、パルス出力周期Ｔからデューティ比ＤＴを減算することにより、減圧時間ＤＴＤを算出する。
【数１１】
ＤＴＤ＝Ｔ−ＤＴ ・・・１１
【００７２】
そして、ステップＳ２０８にて減圧量の推定を行う。
本実施例では、例えば図８のようなアクチュエータモデル（特性）により、ステップＳ２０６で推定した推定中間値Ｐｗ／ｃｉＭと上記で求めた減圧時間ＤＴＤより減圧量ΔＰｄｅｃを算出する。算出値ΔＰｄｅｃは、前記増圧量ΔＰｉｎｃとともに、次のステップＳ２０９での演算に適用される。
ここに、図８の如く、減圧側も増圧側（ステップＳ２０５，図７）と同じく、例えば減圧時間ＤＴＤ＝５ｍｓｅｃの時の特性を基本として、例えばＤＴＤ＝１０ｍｓｅｃの時は、その２倍とするなどしてモデルの簡略化を行っている。
【００７３】
しかして、上述のようにして推定増圧量と推定減圧量を得たら、次のステップＳ２０９以降（図６）では、現在のデューティ比ＤＴが適切かどうかを判断する。
まず、ステップＳ２０９では、前記ステップＳ１０７（図４）で算出の目標増減圧量ΔＰ^＊ と、上記ステップＳ２０５，Ｓ２０８でそれぞれ求めた推定増圧量ΔＰｉｎｃと推定減圧量ΔＰｄｅｃとのトータルの変化量（つまりΔＰｉｎｃ−ΔＰｄｅｃ）との差であるΔＰｎを、
【数１２】
ΔＰｎ＝ΔＰ^＊ −（ΔＰｉｎｃ−ΔＰｄｅｃ） ・・・１２
により計算する。
【００７４】
次いでステップＳ２１０では、この差値ΔＰｎの正負を判断する。 かかる判断の結果、ΔＰｎ≦０が成立しないとき、つまり、ΔＰｎが正の場合は、現在のデューティ比ＤＴでは目標の増減圧量まで増減圧されていない（減圧分が多い）ことになるため、ステップＳ２１１に進み、更に、ＤＴ＜Ｔか否かをチェックする。
その結果、ＤＴ＜Ｔであったなら、つまり、増圧時間がパルス出力周期Ｔに達しておらず、まだ増圧分を増やせる状態ならば、ステップＳ２１２に進み、デューティ比をインクリメントして前記ステップＳ２０３（図５）の上流に戻し、こうしてインクリメントした後の当該デューティ比を適用して、前述した処理に従い、もう一度推定し直す。この場合、ステップＳ２０３→Ｓ２０５→Ｓ２０６→Ｓ２０７→Ｓ２０８→Ｓ２０９という処理が繰り返えされ、その過程で、ステップＳ２１０、及び該当するときは更にステップＳ２１１の判別が行われることとなる。
【００７５】
なお、ここで、ステップＳ２１２では、１だけインクリメント（ＤＴ＝ＤＴ＋１）しているが、ステップＳ２０５で適用するアクチュエータモデル（特性）の基本をＤＴ＝５ｍｓｅｃ（図７）とした場合には、当該インクリメント処理では５インクリメントするようにする（この点については、後述のステップＳ２１４でデクリメント処理の場合に関しても同様である）。
【００７６】
こうして、ＤＴ＜ＴならばＤＴのインクリメントをする。ＤＴ＝Ｔならば、これ以上ＤＴは大きくできないので、ＤＴ＝Ｔ（緩増圧）に決定される。
このようにして本演算ルーチンを終了する場合は、ステップＳ１０９（図４）では、これに従い、周期Ｔ＝５０ｍｓｅｃの全期間にわたりアウトレットバルブが閉位置をとるよう、その駆動パルス出力の態様を設定して出力処理を実行することになる。
【００７７】
ステップＳ２０９で前記差値ΔＰｎが演算されてステップＳ２１０へと進む場合において、逆にΔＰｎが負またはゼロの場合は、現在のデューティで十分に目標の増減圧量が可能であると判断できるために、ステップＳ２１３以下へ処理を進めて本演算ルーチンを終了するものである。
【００７８】
本プログラム例では、一つ前のΔＰｎ−１値（目標増減圧量ΔＰ^＊ と上で求めた推定増圧量ΔＰｉｎｃと推定減圧量ΔＰｄｅｃとのトータル変化量との差）と、現在のΔＰｎ（今回値）を比較して、小さいほうを選択する。つまり、ステップＳ２０３で｜ΔＰｎ｜≧｜ΔＰｎ−１｜の場合は、前回のデューティ比を選択するように、ステップＳ２１４にて値ＤＴをデクリメントする。このようにすると、アンチスキッド制御に必要な目標量ΔＰ^＊ （ステップＳ１０７）に対し、前記式１２による差値として、｜ΔＰｎ｜≧｜ΔＰｎ−１｜となるために一つ前のデューティ比を選択した方が、目標量ΔＰ^＊ に近い値に制御できるからである。よって、こうしてデューティ比ＤＴが設定されるときは、デクリメント処理が行われることから、一つ前のデューティ比に相当するパルスデューティ比ＤＴがステップＳ１０９（図４）の処理に適用され、結果、それに従った駆動パルスが出力されてデューティ制御が実行されることとなり、アンチスキッド制御において目標量ΔＰ^＊ に合わせた液圧制御が行われる。
【００７９】
逆に、｜ΔＰｎ｜＜｜ΔＰｎ−１｜の場合（これは、上記とは逆に、式１２により演算される差値は、今回演算値の方が小さくなることを意味する）は、パルスデューティ比ＤＴとしては、一つ前の前回デューティ比相当にものに設定するよりも、今回のデューティ比でデューティ制御した方が、目標量ΔＰ^＊ に近い値に制御できることから、今回デューティ比を選択するためにステップＳ２１４のデクリメントは行わずに、本ルーチンを終了し、図４のステップＳ１０９の処理に進み、駆動パルスを出力して、今回ループでの制御を終了するものである。
この場合も、上記のようにして、目標により近い値に制御できるパルスデューティ比ＤＴが設定され、これが駆動パルス出力処理に適用される結果、適切なアウトレットバルブデューティ制御が実行されることとなり、アンチスキッド制御において目標量ΔＰ^＊ に合わせた液圧制御を行うことができる。
【００８０】
図９に、アウトレットバルブデューティ制御を行った場合の一例を示す。
説明するに、いま、現在のＷ／Ｃ圧をＰｗ／ｃｏ、現在の時刻をｔｏとする。ＤＴ＝０の時は（この時をｎ＝０とする）、周期Ｔの間、時刻ｔ＋Ｔまで減圧しつづける。この場合、目標増減圧量ΔＰ^＊ と推定増圧量ΔＰｉｎｃと推定減圧量ΔＰｄｅｃとのトータル変化量との差ΔＰｎは、ΔＰｏ＝ΔＰ^＊ ＋ΔＰｄｅｃ（ｏ）となり、ΔＰｏ＞０でＤＴ＜Ｔのため（図６、ステップＳ２１０，２１１）、ＤＴをインクリメント（同ステップＳ２１２）して再度推定をやり直す。これを繰り返し、例えばＤＴ＝ｎ−１の時は、まず、増圧量ΔＰｉｎｃ（ｎ−１）を推定し、推定中間値Ｐｗ／ｃＭｎ−１を算出し、ΔＰｎ−１を求める。この時、推定される最終的なＷ／Ｃ圧をＰｗ／ｃｎ−１とする。この時も、ΔＰｎ−１＞０でＤＴ＜Ｔのため、更に推定をやり直す。
次のＤＴ＝ｎの時も、同様に、Ｐｗ／ｃＭｎ、ΔＰｎを求める。この時は、はじめてΔＰｎ≧０となり、既述のとおり、次のステップ（同ステップＳ２１３）で、ＤＴ＝ｎの場合の｜ΔＰｎ｜とＤＴ＝ｎ−１の場合の｜ΔＰｎ−１｜の大きさを比較し、どちらを選べばより目標に近い値に制御できるか判断する。
図の例の場合は、図に示すように、｜ΔＰｎ｜≦｜ΔＰｎ−１｜のため、ＤＴ＝ｎが選択される。この場合、アウトレットバルブデューティ制御は、前述のようにその選択に従って実行されることになる。
【００８１】
なお、本プログラム例に従い、上記のような駆動パルスデューティ比演算（ステップＳ１０８、図５，６）の実行によりＡＢＳアクチュエータの制御が行われるときは、アンチスキッド制御による増減圧指令である目標増減圧量ΔＰ^＊ （ステップＳ１０７）に対し、アウトレットバルブ駆動パルスのオフ／オンに応じた増圧時の増圧量ΔＰｉｎｃの推定とその後の減圧時の減圧量ΔＰｄｅｃの推定を行うことで、各周期Ｔごとの液圧を推定しながら駆動パルスデューティ比ＤＴを演算する処理を行うことができ、常に液圧を推定しながら任意の液圧に制御可能となる。このため、基本的には、絞りによる緩増圧モードと減圧モードの２モード制御でも、制御性を良くする等のことから、たとえ液圧を保持することが要求されてもこれに容易に応え得て、必要に応じ、例えば図１０のように任意の液圧での保持（増減圧の組み合わせによる保持モード）も可能となり（図中、Ｉ_ＳＯＬ は、アウトレットバルブの駆動パルスを示す）、実質的に、１チャンネル当たり１個の電磁弁であるアウトレットバルブに対する駆動パルスのデューティ比制御をもって、３モードＡＢＳ制御も可能で、簡単かつ廉価な構成で効果的なＡＢＳ制御が行えるものである。
【００８２】
従ってまた、既述の本出願人による先の提案のアンチスキッド制御装置の場合と同様、車輪ロック回避のブレーキ液圧制御を実現する場合において装置構成及び制御の改善が図られ、液圧保持等のため格別のスイッチ手段を新たに付加しないでも済み、それ故サイズアップ／コストアップ等をも招かずに、かつまた電磁弁は１チャンネル当たり１個でも足り、しかも、新たにハードを付け加えるとしたら必要となるであろうその付加部分に対するフェイルセーフ対策を施す必要もない分も、有利である。
【００８３】
そして、これに加えて、本実施例にあっては、そのような絞りによる緩増圧効果を利用したアンチスキッド装置において、目標増減圧量ΔＰ^＊ を設定するのに、緩増圧中の増圧量と車輪のスリップ変化量より路面μ変化量を演算し、路面μ推定を行い、μピークをとるスリップ率Ｓｏに着目してアンチスキッド制御内容を変更するよう（ステップＳ１０４〜Ｓ１０６）、制御することで路面μに応じた最適な制御が行われる。
【００８４】
図１２は、上記の本実施例制御が実行された場合の一例を示す、諸量のタイミングチャートである。
図（ａ）〜（ｄ）は、それぞれ、ＡＢＳ作動時における車輪速Ｖｗ、疑似車体速Ｖｉ、スリップ率Ｓ、路面μ変化量Ｋｓ、及びＷ／Ｃ圧Ｐｗ／ｃの変化、推移を表しており、これによって、実際の路面において、その路面μ特性に応じた最適なスリップ量に制御できる。
先に図１１では２種の代表的なμ−Ｓ特性を示したが、車輪の状態の判断方法として既述したような手法（制御しきい値または目標値を、アンチスキッド装置を個々の車両に適用する時にチューニングにより或る値に設定して、制御時、これとの比較で判断する方法）を専ら採用するシステムのものにあっては、例えば、こうした図１１のようにμ−ｓ特性の異なる路面であっても、スリップ量と車輪加速度をもとに、一律、その或る設定された目標スリップ量に合わせて制御されることとなって、必ずしも最大μのスリップを有効に活用していたとはいえないのに対し、本制御によれば、常に路面μがピークとなるスリップを目標に制御可能となり、結果、そのドライ路、ウエット路のどのような路面状態でも最適に制御され、ＡＢＳ制御をより最適に行うことができるとともに、これにより、Ｗ／Ｃ圧の込め過ぎや抜き過ぎによる減速度減少や舵の効き低下といったこと等も防ぐことができる。
【００８５】
特に、制御モードを、急減圧と緩増圧の２モードを基本にする１チャンネル当たり１個の２位置弁のＡＢＳの場合、緩増圧がないが故に、もし必要以上に一度大きく減圧してしまったとすると、Ｗ／Ｃ圧の増圧が遅いため、その分、減速度不足などの問題が生じ、そのとき、急増圧モードを有する場合のようにはリカバリーも効きにくい。従って、この点から、減圧時、必要最小限の減圧を行うことが重要になってくるのであり、そのためには路面μが推定できることが大きなポイントとなってくるところ、本制御に従えば、そのような要求にも容易に応えられ、２モードＡＢＳでも減速度不足などの事態を適切に回避することができるものである。
【００８６】
更に、その場合に、路面μ推定のための路面μ変化量を計算するのに用いる緩増圧中の増圧量を、上述の駆動パルスデューティ比ＤＴ演算（ステップＳ１０８）における推定増圧量（ΔＰｉｎｃ）値として用いるような技術と組み合わせると、Ｗ／Ｃ圧を検出する液圧センサを新たなハードとして付加せずに済むことは既に述べたとおりであり、この点のおいても、それに要するコスト増やそのセンサ付加に起因するフェイルセーフ対策をも施す必要がない分も、なお一層有利であって、より廉価なシステムで充分なアンチスキッド性能を発揮する、一層改良されたアンチスキッド制御装置を実現することができる。
【００８７】
なお、本発明は、以上の実施例等に限定されるものではない。
例えば、上記制御では、ホイールシリンダ圧の増減サイクルからみると前回のホイールシリンダ圧の増減圧サイクルの増圧時に推定した路面μをもとに今回の増圧時での制御を決定するが、前回１回の推定に応じてのみ路面μを推定するのではなく、数回の推定の平均などにより制御用の目標スリップ量を求めるものとしてもよい。
【００８８】
また、例えば、上記例では路面μ推定を行い、μピークをとるスリップ率Ｓｏに着目してＡＢＳ制御を行っているが、μピーク自体に着目し、路面μに応じた制御変更を行ってもよい。例えば、低μ時は、目標増減圧量ΔＰ^＊ を算出する場合に、車輪加速度の目標値Ｖｗｄ^＊ をＶｗｄ^＊ ＝１．２ｇ＋β（βは路面μピークにより変更）などとして求めるとしてもよい。
【００８９】
また、例えば、駆動パルスデューティ比演算処理と組み合わせる場合において、上記例では、電磁弁駆動パルスのオフ／オンに応じた増圧時の増圧量の推定とその後の減圧時の減圧量の推定を行うものであったが、これは、例えば電磁弁駆動パルスのオン／オフに応じた減圧時の減圧量の推定とその後の増圧時の増圧量の推定を行う態様でもよく、その他の更に改良された態様のものにも広く適用可能である。
い。
【００９０】
また、上記では４チャンネルＡＢＳを例としたが、そのほか３チャンネルＡＢＳでも同様に本発明は適用できることは勿論である。
また、例えば、インレットバルブとアウトレットバルブによるＡＢＳアクチュエータの好適例を図１に示したが、それは、図示のものに限られるものではない。
【００９１】
【発明の効果】
本発明によれば、制動時の車輪ロック回避のアンチスキッド制御において、絞りによる緩増圧効果を利用する１チャンネル当たり１電磁弁構成の場合に、緩増圧中の増圧量と車輪のスリップ変化量より路面μ変化量を演算し、それを基に路面μを推定し、これに応じてアンチスキッド制御内容を変更することができ、絞りによる緩増圧効果を利用する場合における、短時間での緩増圧時の増圧速度はほぼ一定とみなせ単位時間当たりの増圧量が一定になるという特性を活かした路面μ推定も可能で、適切に路面μに応じた最適な制御を行わしめ得て、廉価なシステムを用いても充分なアンチスキッド性能を発揮させるよう制御することができるアンチスキッド制御装置を提供することができる。
【００９２】
この場合において、好ましくは、前記電磁弁は２位置弁とする構成として、本発明は実施でき、また、好ましくは、前記電磁弁が、アンチスキッド制御時、その閉弁位置ではホイールシリンダのブレーキ液を抜き、その閉弁位置では該ブレーキ液の抜きを遮断するよう、供給されるパルス信号により駆動制御されるソレノイドバルブであり、マスターシリンダから該ホイールシリンダへ至る経路には、上流側と下流側との差圧により駆動されるバルブであって、絞りによりアンチスキッド制御の緩増圧を行うバルブを有する構成として、本発明は実施できる。好ましくはまた、車輪速センサからの出力より車輪速を演算する車輪速演算手段と、車輪速より車体速を推定する車体速推定手段と、車輪速より車輪加速度を演算する車輪加速度演算手段と、それら車輪速と車輪加速度と推定された車体速より増減圧量を演算する手段と、駆動パルスを出力する駆動パルス出力手段とを備えるよう構成して、本発明は実施できる。
【００９３】
また、請求項２記載の如く、路面μ変化量の履歴より路面μを推定するよう構成して、本発明は実施でき、同様に上記を実現することができる。この場合は、その履歴をみることで、適切なμ−Ｓ特性の推定ができる。
【００９４】
また、請求項３記載の如く、推定手段よりμピークをとるスリップ率を推定し、それに応じてアンチスキッド制御の目標スリップ量もしくはスリップ量しきい値か、目標車輪加速度もしくは車輪加速度しきい値かのいずれかの変更をするよう構成して、本発明は実施でき、同様に上記を実現することができる。
加えて、この場合は、例えば、ドライ路やウエット路等の異なるμ−Ｓ特性の路面での対応性に優れ、最大μのスリップを有効に活用し得て、路面μがピークとなるスリップを目標に制御可能となり、ホイールシリンダ液圧の込め過ぎや抜き過ぎによる減速度減少や舵の効き低下の防止などにも効果的である。
【００９５】
また、請求項４の場合は、その駆動パルスデューティ比演算手段を更に備えるようにするとともに、前記緩増圧中の増圧量に、該演算手段による推定増圧量が適用されるよう構成して本発明は実施でき、同様に上記を実現することができるとともに、この場合にあっては、更に、その駆動パルスデューティ比演算手段を備えることで、常に液圧を推定しながら任意の液圧の制御可能となり、１チャンネル当たり１個の電磁弁に対する上記駆動パルスのデューティ制御をもって、例えば任意の液圧での保持も可能な保持モードも簡単かつ容易に達成できるなど、より効果的なアンチスキッド制御を実現できる上、かかるデューティ比演算での処理過程で算出される当該推定増圧量が路面μ推定に用いられることから、新たにホイールシリンダ圧センサを付加しないでも済み、それに要するコスト増やそのセンサ付加に起因するフェイルセーフ対策をも施すといったような必要がない分も、なお一層有利であって、より廉価なシステムで充分なアンチスキッド性能を発揮するアンチスキッド制御装置を実現することができる。
【図面の簡単な説明】
【図１】本発明の一実施例の構成を示すシステム図である。
【図２】同例での制御内容の基本構成の一例を表す機能ブロック図である。
【図３】路面μ推定等の原理説明に供する図である。
【図４】同例のコントローラにより実行される制御プログラムの一例を示すフローチャートである。
【図５】同プログラムにおけるソレノイド・バルブ駆動パルス・デューティ比演算ルーチンの一例にして、その一部を示すフローチャートである。
【図６】同じく、他の一部を示すフローチャートである。
【図７】同ルーチンに適用できる、増圧量推定のために用いるアクチュエータモデルの一例を示す図である。
【図８】同じく、同ルーチンに適用できる、減圧量推定のために用いるアクチュエータモデルの一例を示す図である。
【図９】同じく、その駆動パルスデューティ比演算ルーチンによる制御の説明に供する線図である。
【図１０】液圧の保持をも行わせた場合での、２モードＡＢＳ制御の概要を例示する図である。
【図１１】μピークの推定、路面μ変化量等の説明の用に供する説明図である。
【図１２】制御内容の説明に供するタイミングチャートの一例である。
【図１３】μ−Ｓ特性の各種例を示す図である。
【符号の説明】
１ ブレーキペダル
２ ブースタ
３ リザーバ
４ マスターシリンダ
５ モータ
６，７ ポンプ
８，９ リザーバ
１０，２０ 左右前輪
１１，２１，３１，４１ ホイールシリンダ
１２，２２，３２，４２ インレットバルブ（メカ式）
１３，２３，３３，４３ アウトレットバルブ（電磁弁）
３０，４０ 左右後輪
５０ コントローラ
５１，５２，５３，５４ 車輪速センサ
５５ ブレーキスイッチ（ＳＷ）[0001]
[Industrial applications]
The present invention relates to a vehicle anti-skid control device.
[0002]
[Prior art]
An anti-skid system (ABS) for controlling the brake fluid pressure of a vehicle is effective in avoiding wheel lock during braking on a low μ road or the like, but as an actuator and control in such a system. 2. Description of the Related Art An actuator using two solenoid valves per channel (a so-called three-mode ABS in which each mode of pressure reduction, holding, and pressure increase is performed by a combination of valve opening and closing) is known. There is also a type in which one 3-position valve is provided as one solenoid valve per channel.
As described above, various ABS device configurations have been proposed, but with the spread of anti-skid devices, a more inexpensive system has been desired.
[0003]
Under these circumstances, an anti-skid control device of the type having two two-position valves per channel (one per channel may be used for a three-position valve) and one two-position valve per channel The present applicant has previously proposed a technique relating to an improved anti-skid control device according to Japanese Patent Application No. 6-279242. This is a two-mode ABS that uses the slow pressure increase effect of the throttle, and only one solenoid valve per channel is sufficient, and the device configuration and control are improved.
[0004]
[Problems to be solved by the invention]
On the other hand, the anti-skid device usually includes, for example, a wheel speed sensor to obtain control information necessary for ABS control based on detected wheel speed information, and many systems adopt this. . In this case, the vehicle speed can be estimated from the sensed wheel speed, and the wheel acceleration can be calculated from the wheel speed.The state of the wheel is determined based on the slip amount and the wheel acceleration obtained from the vehicle speed and the wheel speed. The brake pressure can be controlled according to the state of the wheels.
[0005]
As described above, the ABS system can perform feedback (F / B) control based on the wheel speed. In this case, as a method of determining the wheel state, a certain set control threshold (or target value) and a predetermined control threshold (or target value) are used. The threshold value is set by tuning when the anti-skid device is applied to each vehicle.
[0006]
However, at the time of brake fluid pressure control for avoiding wheel lock during braking, the actual state of the road surface μ is various and constant as shown in FIG. 13 (so-called μ-S characteristic (friction coefficient-slip amount characteristic)). Not something. The coefficient of friction between the road surface and the tire differs depending on the condition of the road surface during braking and the like, and as shown in the figure, generally, in a dry state (dry road), the friction coefficient is large (2 in the upper side in the figure). Two characteristics), and in a wet state (such as a wet road), it is small (the two characteristics on the lower side in the figure).
As described above, since the state of the road μ is not constant, if a certain control threshold value is set, for example, by the above-described tuning, a certain degree of control can be performed. There is a problem that optimal control is no longer performed.
For this reason, it is conceivable that the road surface μ is estimated and anti-skid control is performed more optimally. However, it is more preferable to satisfy such a requirement at the same time as a more inexpensive system is desired as described above. In addition, it is intended to realize this and to optimize the control according to the road surface μ.
[0007]
In particular, in the case of an anti-skid device of the type of one two-position valve per channel as described above, the control mode of the brake fluid is such that the conventional actuator capable of holding has three modes of pressure reduction, holding, and pressure increasing. While five basic modes (rapid pressure reduction, gentle pressure reduction, holding, slow pressure increase, rapid pressure increase) can be performed, two modes of pressure reduction (rapid pressure reduction) and slow pressure increase are basically used.
[0008]
However, in the case of such a type, since there is no sudden increase in pressure, if the pressure is inappropriately reduced once in an ABS operation or in a braking situation, the increase in pressure is slow, resulting in insufficient deceleration. In some cases, recovery is effective if there is a sudden increase in pressure, but such recovery is difficult to expect because of a gradual increase in pressure.
Therefore, it is important to perform the minimum necessary decompression. For that purpose, if the road surface μ can be appropriately estimated and the optimal control can be performed, it is effective for further improving the effectiveness of the ABS control for such a type of system. It becomes.
[0009]
The present invention is based on the above considerations, and in anti-skid control using the gradual pressure increase effect of the throttle, it is possible to perform optimal control appropriately in accordance with the road surface μ, and to achieve sufficient anti-skid control even with a low-cost system. This is to realize a control device that can exhibit skid performance.
Another object of the present invention is to provide an improved anti-skid control device capable of further improving the anti-skid control device according to the above-mentioned proposal of the present applicant.
[0010]
[Means for Solving the Problems]
According to the present invention, the following anti-skid control device is provided.
That is, an anti-skid device controlled by one solenoid valve per channel using a slow pressure increase effect by a throttle,
Estimating means for calculating a road surface μ change amount from the pressure increase amount during the gradual pressure increase and a wheel slip change amount, and estimating a road surface μ-slip ratio characteristic based on the road surface μ change amount;
Control changing means for changing the contents of anti-skid control according to the estimating means;
An anti-skid control device characterized by comprising:
[0011]
Further, in the above, the estimating means estimates the road surface μ-slip ratio characteristic from the history of the road surface μ change amount,
An anti-skid control device characterized in that:
[0012]
Further, the change of the control content is as follows:
The slip ratio having the μ peak is estimated by the estimating means, and either the target slip amount or the slip amount threshold value of the anti-skid control or the target wheel acceleration or the wheel acceleration threshold value is changed accordingly. ,
An anti-skid control device characterized in that:
[0013]
Further, in response to the pressure increase / decrease command of the anti-skid control, by estimating the pressure increase amount or the pressure decrease amount at the time of pressure increase or pressure decrease, and estimating the pressure decrease amount or the pressure increase amount at the time of the subsequent pressure decrease or pressure increase, A drive pulse duty ratio calculating unit that calculates a duty ratio of a drive pulse output to the solenoid valve while estimating a hydraulic pressure for each cycle, further comprising:
The pressure increase amount estimated by the calculation means is applied to the pressure increase amount during the gradual pressure increase.
An anti-skid control device characterized in that:
[0014]
[Action]
In the anti-skid control device of the present invention, in anti-skid control for avoiding wheel lock during braking, the braking of the control target wheel is controlled by a configuration of one solenoid valve per channel utilizing a gradual pressure increasing effect by a throttle. In this case, the estimating means and the control changing means are provided to calculate the road surface μ change amount from the pressure increase amount during the gradual pressure increase and the wheel slip change amount, and based on the calculated road surface μ-slip ratio characteristic (μ -S characteristic), and the anti-skid control content is changed accordingly.
[0015]
Therefore, by providing such an estimating means and a control changing means, in the case of using the gradual pressure increase effect by the throttle, the pressure increase rate at the time of the gradual pressure increase in a short time is regarded as substantially constant, and the pressure increase amount per unit time It is also possible to estimate the road surface μ-slip ratio characteristics utilizing the characteristic that the road surface becomes constant, and it is possible to perform optimal control appropriately according to the road surface μ, and to achieve sufficient anti-skid performance even when using an inexpensive system. It is possible to achieve control to make it work.
[0016]
In the anti-skid control device of the present invention, preferably, the solenoid valve can be a two-position valve. Also, preferably, the solenoid valve is driven by a pulse signal supplied so as to drain the brake fluid from the wheel cylinder at the valve closing position during anti-skid control and to shut off the brake fluid at the valve closing position. A solenoid valve that is controlled, and a valve that is driven by a differential pressure between the upstream side and the downstream side in a path from the master cylinder to the wheel cylinder, and that performs a gentle pressure increase in anti-skid control by a throttle. Can be provided.
Preferably, further, a wheel speed calculating means for calculating a wheel speed from an output from a wheel speed sensor, a vehicle speed estimating means for estimating a vehicle speed from the wheel speed, a wheel acceleration calculating means for calculating a wheel acceleration from the wheel speed, It can be configured to include means for calculating the amount of pressure increase / decrease from the wheel speed, the wheel acceleration, and the estimated vehicle speed, and drive pulse output means for outputting a drive pulse.
[0017]
Further, the estimating means is configured to estimate the road surface μ-slip ratio characteristic from the history of the road surface μ change amount, so that the anti-skid control device of the present invention can be implemented, and if the above can be realized similarly Close. In this case, it is possible to estimate the appropriate μ-S characteristic by looking at the history.
[0018]
The control content is changed by estimating the slip ratio at which the μ peak is obtained by the estimating means, and determining whether the target slip amount or the slip amount threshold value of the anti-skid control, the target wheel acceleration or the wheel acceleration threshold value is accordingly determined. The anti-skid control device of the present invention can be implemented by making any of the modifications described above, and the same can be realized similarly. In addition, in this case, for example, it is excellent in correspondence with a road surface having different μ-S characteristics such as a dry road and a wet road, and the maximum μ slip can be effectively utilized, and the slip at which the road μ reaches a peak is reduced. It becomes possible to control to the target, and it is also effective in preventing a decrease in deceleration and a decrease in rudder effectiveness due to excessively injecting and extracting the wheel cylinder hydraulic pressure.
[0019]
Further, in response to the pressure increase / decrease command of the anti-skid control, by estimating the pressure increase amount or the pressure decrease amount at the time of pressure increase or pressure decrease, and estimating the pressure decrease amount or the pressure increase amount at the time of the subsequent pressure decrease or pressure increase, A drive pulse duty ratio calculating means for calculating a duty ratio of a drive pulse to be output to the solenoid valve while estimating a hydraulic pressure for each cycle is further provided, and the pressure increase amount during the gradual pressure increase is calculated. The anti-skid control device of the present invention can be implemented so that the estimated pressure increase amount by means is applied, and it is possible to realize the same as above.
[0020]
In this case, by further providing the drive pulse duty ratio calculation means, it is possible to control any hydraulic pressure while constantly estimating the hydraulic pressure, and it is possible to control the drive pulse for one solenoid valve per channel. With the duty control, more effective anti-skid control can be realized, for example, a holding mode capable of holding at an arbitrary hydraulic pressure can be easily and easily achieved, and the duty ratio is calculated in the process of the duty ratio calculation. Since the estimated pressure increase amount is used for estimating the road surface μ-slip ratio characteristic, it is not necessary to newly add a wheel cylinder pressure sensor, and a cost increase required for the sensor and a fail-safe measure due to the addition of the sensor are taken. It is even more advantageous because there is no need for it, and it provides sufficient anti-skid performance with a cheaper system. It is possible to realize a Nchisukiddo controller.
[0021]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing the configuration of one embodiment of the present invention.
In this embodiment, the vehicle to be applied is a four-channel anti-skid system (4ch ABS) that can independently control the left and right brake fluid pressures (brake fluid pressure) for both front and rear wheels.
[0022]
In the figure, 1 is a brake pedal, 2 is a booster as a brake booster, 3 is a reservoir, 4 is a master cylinder (M / C), 10, 20 are the left and right front wheels of the vehicle, 30, 40 are The left and right rear wheels are shown.
Each wheel 10, 20, 30, 40 includes a wheel cylinder (W / C) 11, 21, 31, 41, and an actuator for avoiding wheel lock is provided between the master cylinder 4 and the wheel cylinder. Provided.
[0023]
In the illustrated example, the channels for each wheel have inlet valves 12, 22, 32, 42 and outlet valves 13, 23, 33, 43, and the reservoirs 8, 9 and the pumps 6, 7 driven by the motor 5 And an anti-skid device that connects these to the piping as shown in the drawing to form an ABS hydraulic circuit. In the brake fluid pressure system from the master cylinder 4 to the wheel cylinders 11 to 41, in the front wheel (front) brake system, the master cylinder fluid path connects the inlet valves 12 and 22 to the inlet valves 12 and 22, respectively. From the front to the respective wheel cylinders 11 and 21 of the front wheels 10 and 20 via the liquid paths on the respective wheel cylinder sides. Similarly, in the rear wheel (rear) brake system, the master cylinder fluid path is connected to each of the inlet valves 32, 42, and from the inlet valves 32, 42 through the fluid path on each wheel cylinder side, the rear wheel 30 is connected. , 40 to the respective wheel cylinders 31, 41.
[0024]
Each of the wheel cylinder fluid paths connected to each of the front wheel wheel cylinders 11 and 21 is branched from the middle thereof, and these branch fluid paths are connected to the front wheel reservoir 8 through the outlet valves 13 and 23, respectively. Through to the master cylinder fluid path on the upstream side. Similarly, the wheel cylinder fluid passages connected to the wheel cylinders 31 and 41 of the rear wheels also branch from the middle, respectively, and these branch fluid passages are connected to the rear wheel reservoir 9 through outlet valves 33 and 43, respectively. It is connected to the master cylinder fluid path on the upstream side through the rear wheel pump 7.
[0025]
Here, each of the inlet valves 12, 22, 32, and 42 is an inlet valve driven by a differential pressure between the upstream side (the master cylinder side) and the downstream side (each wheel cylinder side), and creates a gradual pressure increase by a throttle. In addition, each of the outlet valves 13, 23, 33, and 43 is a two-position solenoid valve for ON / OFF control here.
One such outlet valve is provided for each channel, and is normally (in a state where the solenoid is not energized) at the first position shown in the drawing and is connected between the valve input / output ports, and accordingly, the corresponding reservoirs 8, 9 And a two-port two-position solenoid valve that takes a second position to connect the input and output ports when switching, and thus a position to connect the wheel cylinders to the corresponding reservoirs 8,9. This is used to reduce the wheel cylinder pressure by conducting the brake fluid of the corresponding wheel cylinder to the reservoir during anti-skid control.
In the control of this embodiment, the inlet valves (mechanical type) 12, 22, 32, 42 are inserted into the path between the master cylinder 4 and the wheel cylinders 11, 21, 31, 41, and the outlet valves 13, 23, By performing duty control described later as drive control for the wheels 33 and 43, the brake fluid pressure (brake fluid pressure P) of each of the wheel cylinders 11, 21, 31, and 41 of the corresponding wheel is individually controlled in the corresponding channel. .
[0026]
In the case of the illustrated example, the inlet valves 12, 22, 32, and 42 assume a position where the throttle does not act in a state where no differential pressure is generated between the upstream side and the downstream side. In addition, the outlet valves 13, 23, 33, 43 maintain the illustrated closed position when OFF. In such a state, when the hydraulic pressure from the master cylinder 4 is supplied to each wheel cylinder by depressing the brake pedal 1, the master cylinder pressure is transmitted as it is through the master cylinder fluid path, each inlet valve, and the wheel cylinder fluid path. Therefore, the brake hydraulic pressure can be increased toward the master cylinder hydraulic pressure, which is the original pressure, and each wheel is individually braked to perform normal braking.
[0027]
At the time of such braking, when the outlet valves 13, 23, 33, 43 of the respective channels are operated so as to open and close, the branch fluid paths to the corresponding reservoirs 8, 9 are opened at the valve opening position, and the corresponding wheel is opened. The brake fluid of the cylinder is guided to the reservoir and drained. In addition, during the period in which the valve is closed, the communication with the reservoir is cut off to cut off the brake fluid pressure.
Thus, by such opening / closing drive control of the outlet valve, a reduced pressure state is established in which the brake fluid pressure is released to the corresponding reservoir and reduced.
[0028]
The brake fluid accumulated in the reservoirs 8 and 9 due to the pressure reduction is returned to the upstream of the inlet valves 12, 22, 32 and 42 by the pumps 6 and 7 driven by the motor 5. Then, the returned brake fluid is used for pressure increase.
When the pressure in the corresponding fluid passage on the wheel cylinder side becomes lower than the fluid passage on the master cylinder side due to the pressure reduction by the operation of the outlet valves 13, 23, 33, 43, the inlet valves 12, 22, 32, 42 are moved upstream and downstream. The differential cylinder is operated by generating a pressure difference, whereby the communication between the master cylinder 4 and the corresponding wheel cylinder is switched to a communication with a throttle, and the wheel cylinder pressure is gradually increased.
[0029]
The outlet valves 13, 23, 33, 43 and the pump driving motor 5 of the anti-skid device are controlled by the output signal of the controller 50. Signals from wheel speed sensors 51, 52, 53, 54 for speed detection are input, respectively.
In this embodiment, a signal of a brake switch (SW) 55 is also input to the controller 50.
[0030]
The controller 50 includes an input detection circuit, a calculation processing circuit, a storage program for storing a control program such as anti-skid control executed by the calculation processing circuit, a calculation result, and the like, and outlet valves 13, 23, 33, 43 and an output circuit for supplying a control signal to the motor 5.
[0031]
In this embodiment, the gradual pressure increase effect of the throttles of the inlet valves 12, 22, 32, 42 for each channel, which is a mechanical valve mechanism driven by a differential pressure, is used. This is an anti-skid device in which the hydraulic pressure of the control target wheel is controlled by one outlet valve 13, 23, 33, 43, which is a solenoid valve. When braking, the controller 50 locks the wheel based on input information. The anti-skid control is executed by controlling the driving of the outlet valves 13, 23, 33, 43 in order to prevent the above.
Therefore, in the present apparatus, a drive pulse is output to the solenoid valves provided for each wheel to reduce and slowly increase the wheel cylinder hydraulic pressure.
In the case of the four-channel four-sensor ABS control as in this example, basically, when the wheel speed information is obtained for each of the four front, rear, left and right wheels, the vehicle speed is estimated from the wheel speed, and the wheel acceleration is used. Furthermore, the wheel acceleration is also calculated from the wheel speed for each wheel, the target pressure increase / decrease amount is obtained from the wheel speed, the wheel acceleration, and the vehicle speed, and the wheel cylinder hydraulic pressure of the corresponding wheel is controlled, so that braking is performed. Can be controlled to avoid wheel lock.
[0032]
Further, as described above, the controller 50 is configured to use one outlet valve 13, 23, 33, 43 of one 2-position valve per channel, and has a slow pressure increasing mode and a pressure decreasing mode. Even if the ABS controls the valve based on the pulse signal, the ABS control can perform a holding mode of maintaining the brake fluid pressure at a desired fluid pressure as well as reducing and increasing the pressure as necessary. The arithmetic processing circuit also executes a process of calculating the duty ratio of the drive pulse for the outlet valves 13, 23, 33, 43, and controls the drive.
[0033]
In this case, the controller 50 also calculates the duty ratio of the driving pulse while estimating the hydraulic pressure so that the hydraulic pressure can be controlled to an arbitrary hydraulic pressure by estimating the hydraulic pressure. It also has various functions.
[0034]
In other words, the duty ratio of the drive pulse is calculated while estimating the hydraulic pressure for each cycle by estimating the hydraulic pressure in each cycle by estimating the hydraulic pressure for each cycle in response to the pressure increase / decrease command for driving the outlet valve. The outlet valve is controlled in accordance with the duty ratio.However, in accordance with the road surface condition during braking, the amount of pressure increase during slow pressure increase and wheel slip The road surface μ change amount is calculated from the change amount, the road surface μ is changed based on the calculated change amount, and control for changing the anti-skid control content is performed so that the ABS control is more appropriately performed.
In this case, for the pressure increase amount during the gradual pressure increase used as the basis for calculating the road surface μ change amount, the estimated pressure increase amount value at the time of pressure increase in the duty ratio calculation of the drive pulse is preferably applied. Can be.
Preferably, in the control of the change of the ABS control, the slip ratio at which the μ peak is obtained is estimated by the road surface μ estimating means, and the target slip amount (or the slip amount threshold value) and the target wheel acceleration of the ABS control are accordingly adjusted. (Or the wheel acceleration threshold).
[0035]
FIG. 2 is a block diagram showing an example of the outline of the function of the embodiment system shown in FIG. 1 for such ABS control.
As shown in the figure, a wheel speed calculating means a for calculating a wheel speed from an output from a wheel speed sensor (4 sensors) provided for each wheel to be controlled, a vehicle speed estimating means b for estimating a vehicle speed from the wheel speed, and a A wheel acceleration calculating means c for calculating wheel acceleration, a pressure increasing / decreasing amount calculating means d for calculating a pressure increasing / decreasing amount based on the wheel speed, the wheel acceleration and the estimated vehicle speed, and a drive pulse output means h for outputting a drive pulse. An anti-skid device provided with a drive pulse / duty ratio calculating means e, and a road surface μ estimating means f and a control content changing (anti-skid control changing) means g.
[0036]
The road surface μ estimating means f is an estimating means for calculating the road surface μ from the pressure increase amount during the gradual pressure increase and the slip change amount, and estimating the road surface μ based on the calculated road surface μ. It functions as changing means for changing the contents of the anti-skid control according to the estimating means f.
Preferably, the drive pulse / duty ratio calculation means e is provided with a pressure increase / decrease command in anti-skid control (including a control content changed by the control content changing means g, for example, a target slip is changed). On the other hand, the estimation of the pressure increase (or pressure reduction) amount at the time of pressure increase (or pressure reduction) according to the off / off (or on / off) of the solenoid valve driving pulse, and the subsequent pressure reduction (or pressure increase) at the time of pressure reduction (or pressure increase) By estimating the pressure increase) amount, the duty ratio of the solenoid valve drive pulse can be calculated while estimating the hydraulic pressure for each cycle.
[0037]
Here, the parts of the wheel speed calculating means a, the vehicle body speed estimating means b, the wheel acceleration calculating means c, the pressure increasing / decreasing amount calculating means d, and the drive pulse output means f constitute a known normal anti-skid control system. However, in contrast to the anti-skid control system, the anti-skid control device according to the present embodiment further includes the drive pulse / duty ratio calculation means e, and further has the improved anti-skid control system. The control device has an improved configuration provided with the road surface μ estimating means f and the anti-skid control content changing means g, and has an anti-skid (ABS) of a 1ch1 electromagnetic valve utilizing a gentle pressure increase effect by a throttle. In this configuration, the actuator g (4 ch) is combined.
The driving pulse duty ratio calculating means e is configured to include the pressure increase amount estimating section and the pressure reducing estimating section as described above, and the driving pulse output means f follows the duty ratio obtained by the driving pulse duty ratio calculating means e. A drive pulse is output to the anti-skid actuator g to control the brake fluid pressure P of the corresponding wheel, and thus the wheel cylinder pressure.
Preferably, the road surface μ estimating means f can estimate the road surface μ from the history of the road surface μ change amount.
[0038]
In the present embodiment, the wheel speed calculating means a, the vehicle speed estimating means b, the wheel acceleration calculating means c, and the pressure increasing / decreasing amount calculating means d include the wheel speed sensors 51 to 54 of FIG. It consists of. The controller 50 also includes a drive pulse / duty ratio calculation unit e, a drive pulse output unit f, a road surface μ estimation unit f, and a control content change unit g. The anti-skid actuator g further includes an outlet valve 13 as a solenoid valve. , 23, 33, and 43, the ABS hydraulic circuit shown in FIG. 1 between the master cylinder 4 and the wheel cylinders 11, 21, 31, and 41.
[0039]
Here, the principle content and the like of the above configuration regarding the estimation of the road surface μ and the change control of the anti-skid control based on the estimation will be described as follows with reference to FIG.
The control of the above-described configuration according to the present invention is applicable to an ABS system controlled by one solenoid valve per channel using the slow pressure increase effect by the throttle. In this case, the slow pressure increase effect by the throttle is used. First, the anti-skid device is based on the idea that the pressure increasing speed at the time of gentle pressure increase in a short time can be regarded as substantially constant. Specifically, the pressure increasing speed can be regarded as substantially constant in such a manner, but the characteristic of the actuator that the pressure increasing rate is constant = the pressure increasing amount per unit time is constant. The road surface μ is estimated.
[0040]
FIG. 3 shows a model for analyzing the equation of motion of the wheel. Considering the equation of motion of each wheel at the time of braking, this is as follows.
(Equation 1)
I · (d / dt) ω = μ · W · R−k · Pw · r 1
However,
I; Wheel inertia
(D / dt) ω: wheel angular acceleration
μ; road surface μ
W; wheel load
R; wheel radius
k; brake specification coefficient (pat μ, wheel cylinder area, etc.)
Pw: Wheel cylinder pressure
r; rotor effective diameter
[0041]
Although the equation of motion of the wheel is expressed as described above, the absolute value (value Pw) of the wheel cylinder pressure is required to calculate the road surface μ from the equation 1, and the wheel cylinder pressure sensor for detecting the wheel cylinder pressure Without it, the calculation becomes difficult, and when a pressure sensor is attached, problems such as cost and reliability arise.
Therefore, secondly, taking such points into consideration, at a certain time interval (for example, at a certain time t1 and a certain time t2 at a predetermined time interval), a motion equation is set and a difference is obtained. Considering the case where the change of μ is calculated, it is as follows.
[0042]
That is, in this case, at each time point,
(Equation 2)
I · (d / dt) ω ₁ = Μ ₁ ・ W ・ R−k ・ Pw ₁ ・ R ・ ・ ・ 2
(Equation 3)
I · (d / dt) ω ₂ = Μ ₂ ・ W ・ R−k ・ Pw ₂ ・ R ・ ・ ・ 3
Hold respectively.
Here, W, R, k, and r are assumed to be substantially constant.
[0043]
Accordingly, from the above, the road surface μ (= μ ₁ ) And road surface μ at time t2 (= μ ₂ ) Difference (μ ₂ −μ ₁ ), That is, the degree of change
(Equation 4)

And the amount of change in the road surface μ (= μ ₂ −μ ₁ ) Is calculated from the wheel acceleration and the change amount ΔPw of the wheel cylinder pressure (see FIG. 11).
[0044]
Thus, by utilizing the characteristics of the anti-skid actuator i (the ABS hydraulic circuit shown in FIG. 1), the change of the road surface μ is such that the element portions such as W do not change within the time interval (or, Under the condition that it is substantially constant and does not substantially change), by knowing the other change parameter values described above, the calculation is performed based on Equation 4 in accordance with them.
On the other hand, the slip amount of the wheel is calculated from the wheel speed, for example, in the same manner as a conventionally known method, and the amount of change in the slip amount per time is also calculated (see the same figure).
[0045]
When the change amount of the road surface μ and the change amount of the slip amount are obtained, the change amount of the road surface μ with respect to the slip change can be determined from the change amount of the slip amount and the change amount of the road surface μ. Can be estimated (see the figure).
Further, if the μ-S characteristic is known, the slip amount at which the μ peak is obtained can be estimated, and the anti-skid control can be performed by performing control (variable control) so that the wheel slip is adjusted to the slip amount. That is, on the actual road surface, the wheels can be controlled to the optimum slip amount according to the road surface μ characteristic (road surface μ estimating means f, control content changing means g).
[0046]
Even if the state of the road surface μ at the time of braking is greatly different depending on the road surface in the braking scene, if the anti-skid control with the road surface μ estimation and control change as described above is the principle, the road surface μ is always The anti-skid performance can be adequately controlled even if an inexpensive system is used.
[0047]
Furthermore, the change amount ΔPw of the wheel cylinder pressure in the above equation 4 (the multiplication value (= Pw ₂ -Pw ₁ ), The control pulse estimating means e (controller 50) estimates the control amount at the time of control in the form of a combination of pressure increase and pressure reduction, thereby obtaining the electromagnetic valve drive pulse for each predetermined period. The estimated pressure increase amount value calculated and used in the calculation process in the case of calculating the duty ratio is applicable. In such a case, it is needless to say that a new wheel cylinder pressure sensor need not be added separately. The effect of combination with an inexpensive ABS system using one solenoid valve per channel utilizing the slow pressure increasing effect of the throttle is greater. In this regard, an inexpensive system can perform optimal control according to the road surface μ. As a result, sufficient anti-skid performance can be exhibited, and its effectiveness is further improved.
[0048]
FIGS. 4 to 6 are flowcharts of an example of an anti-skid control program that is executed by the controller 50 and includes the above-described drive pulse / duty ratio calculation processing, road surface μ estimation, and control content change processing. This process is performed by a periodic interrupt at a fixed time interval in an operating system (not shown).
7 and 8 are characteristic diagrams showing an example of an actuator model used for estimating the pressure increase amount and the pressure decrease amount, respectively. The characteristic data may be stored in the storage circuit of the controller 50 in advance. it can. FIGS. 9 to 12 are diagrams for explaining the control contents.
[0049]
Hereinafter, the control program shown in FIG. 4 will be described with reference to these drawings. The control program shown in FIG. 4 reads the wheel speed, calculates the wheel acceleration, calculates the pseudo vehicle speed, determines whether or not the vehicle is under the gradual pressure increase, and determines the amount of change in the road surface μ. (Ks) calculation, μ peak estimation, setting of Ks = Kso, target slip ratio (S ^* ), The target pressure increase / decrease amount (ΔP ^* ) Calculation, a solenoid valve / drive pulse duty ratio calculation routine, and drive pulse output processing (steps S100 to S110). In the present embodiment, the ABS control is performed by the PD control based on the wheel speed F / B.
[0050]
4, first, in step S100, each wheel speed Vwi (i = 1 to 4) is read based on signals from the wheel speed sensors 51 to 54.
Next, in step S101, a wheel acceleration Vwd is calculated from the wheel speed Vwi. In the present embodiment, for example, it is determined from the speed difference between 30 msec.
[0051]
In a succeeding step S102, a pseudo vehicle speed Vi is calculated.
In the present embodiment, Vi is calculated by a method used in normal ABS. That is, here, a filter is applied to the wheel speed Vw of each wheel, a value Vwfi (i = 1 to 4) closer to the vehicle speed is calculated for each wheel, and each Vwfi is calculated according to conditions such as braking / non-braking. Then, Vwf (referred to as the vehicle body speed intermediate value) closest to the vehicle body speed is calculated, for example, by selecting the largest vehicle speed, and the pseudo vehicle body speed Vi is obtained based on this Vwf.
[0052]
Next, in the example of the program, in step S103 following step S102, it is selected whether or not to estimate the road surface μ based on whether or not the wheel cylinder pressure (W / C pressure) is gradually increasing.
In the present embodiment, even if the check is performed, a W / C pressure control signal DT (DT is a time during which the outlet valve is closed during a pulse output period T, for example, 50 msec, for example, DT = 10 msec, etc.) The definition is made based on whether the DT value is equal to the pulse output period T, that is, whether DT = T holds. When DT = T, since the outlet valve is kept closed, the pressure is being slowly increased during the period T.
[0053]
As a result of the check in step S103, when DT = T, the process proceeds to step S104 and thereafter to calculate the amount of change in the road surface μ, and when DT ≠ T, the process proceeds to step S110, where The change amount Ks of μ is set to a predetermined desired value Kso, and then the process proceeds to step S106.
[0054]
In step S104, the amount of change Ks of the road surface μ with respect to the slip ratio is calculated.
In the present embodiment, the wheel speed Vw, the wheel acceleration Vwd, the pseudo vehicle body speed Vi, and the wheel cylinder pressure change amount ΔPw / c during the gradual increase in pressure are calculated for each of the periodic interruptions at predetermined time intervals. The amount of change in the road surface μ is calculated from the pressure increase ΔPinc value (previous value) of the W / C pressure (Pw / ci), which is calculated in a solenoid valve drive pulse / duty ratio calculation routine described later. .
[0055]
First, according to the principle described above, the following calculation calculates the amount of change in the road surface μ within a certain time (= μ ₂ −μ ₁ ) (FIGS. 3 and 11).
(Equation 5)
I · (d / dt) ω ₁ = Μ ₁ ・ W ・ Rk ・ Pw / c ₁ ・ R ・ ・ ・ 5
(Equation 6)
I · (d / dt) ω ₂ = Μ ₂ ・ W ・ Rk ・ Pw / c ₂ ・ R ・ ・ ・ 6
(Here, W, R, k, and r are regarded as substantially constant)
(Equation 7)

[0056]
Next, the slip ratio change amount (= S ₂ -S ₁ ) Is determined from the wheel speed Vw and the pseudo vehicle speed Vi (FIG. 11).
(Equation 8)

From the above, the variation amount Ks of the road surface μ with respect to the slip ratio = (μ ₂ −μ ₁ ) / (S ₂ -S ₁ ) Is required.
[0057]
Next, in the present program example, the μ peak is estimated in the following step S105.
In the present embodiment, the μ at the slip rate So when the road μ change amount Ks obtained in step S104 becomes a negative value (or the predetermined set value Kso or less) is estimated as the μ peak.
[0058]
FIG. 11 also illustrates the principle of μ peak estimation, which illustrates two different μ-S characteristics for a relatively dry road and a wet road with a much lower μ value, and , The slip ratio of the maximum μ is also different as shown in the figure.
In the figure, the characteristics show, for example, each slip ratio S ₁ , S ₂ , S ₃ , S ₄ Paying attention to the points and the corresponding points on the road μ, in the case of the above-mentioned dry road characteristics, the μ peak shows the slip ratio S ₁ ~ S ₂ , S ₂ ~ S ₃ , S ₃ ~ S ₄ Of the slip ratio S ₃ ~ S ₄ It can be understood that the road surface μ change amount Ks value is the slip ratio S ₂ ~ S ₃ And slip rate S ₃ ~ S ₄ The sign has changed between (here, the former part is (μ ₃ −μ ₂ ) / (S ₃ -S ₂ ) And Ks> 0, but the latter part is (μ ₄ −μ ₃ ) / (S ₄ -S ₃ ), Ks <0, indicating a negative value), and the maximum μ is the slip ratio S ₃ ~ S ₄ It turns out that it is in the range.
[0059]
On the other hand, in the case of the wet road characteristics, the slip ratio S is smaller than that of the dry road. ₁ , S ₂ , S ₃ , S ₄ The road surface μ corresponding to the point has the value μ as shown in the figure. ₁ ′, Μ ₂ ′, Μ ₃ ′, Μ ₄ ′, The μ peak has a characteristic shifted to the low slip ratio side, and the slip ratio S ₂ ~ S ₃ However, even in such a case, the maximum μ can be adjusted to the slip ratio S by using the road surface μ change amount Ks value obtained according to the above. ₂ ~ S ₃ It can be seen that it is in the range, and the μ peak estimation is performed similarly.
Therefore, regardless of the μ-S characteristic of the road surface in the actual braking scene, the Ks value indicating the degree of change of the road surface μ with respect to the slip ratio is determined in accordance with the state of the road surface μ. , Μ peak rate can be estimated.
When such estimation can be performed, the ABS control is basically performed such that the actual slip rate is always near the maximum μ slip rate on the corresponding μ-S characteristic during the ABS operation. Can be done.
[0060]
Returning to FIG. 4, when the process proceeds to step S106, in this step, the target slip ratio S ^* Is calculated. In the present embodiment, the target slip ratio S is calculated from the slip ratio So at the time of μ peak obtained in step S105. ^* = Min (So, Solmit). Here, as a countermeasure against a road surface in which the μ peak has a very large slip ratio (in such a road surface, a longitudinal force is generated but a lateral force becomes too small, and the steering tends to be less effective). Target slip ratio S ^* When calculating So, a limit Solim of the maximum value is provided to So.
Therefore, here, such a limit check process is also included, and as a result, the value So obtained by the μ peak estimation (for each estimated μ-S characteristic according to the corresponding road surface at the time of actual ABS operation (for example, The smaller one of the two values of each characteristic in FIG. 11), a variable value that indicates a different value), and the value Solmit (predetermined fixed value) is the target value S ^* (Specifically, if the value So obtained in step S105 is less than the value Solmit, the value So is directly changed, and if the value So exceeds the value Solmit, Can be selected instead of the value So, respectively.
When the present control is performed in such a manner that the target slip ratio is set based on the μ peak estimation, finer control can be performed in this manner.
[0061]
Next, in step S107, the target pressure increase / decrease amount ΔP ^* Is calculated.
In this embodiment, the anti-skid control is, for example, PD control as described above.
In brief, the target pressure increase / decrease amount ΔP is calculated from the wheel speed Vw, the pseudo vehicle body speed Vi, and the wheel acceleration Vwd of each wheel obtained in steps S100 to S102 according to the following equation 9. ^* Is calculated.
(Equation 9)
ΔP ^* = Kp × (Vw ^* −Vw) + kd × (Vwd ^* -Vwd) 9
[0062]
Here, kp and kd are control gains (proportional control gain and differential control gain), respectively, and are changed according to the running state.
Also, Vw ^* Is the target value of the wheel speed, and here, the value S of the target slip ratio obtained in step S106 ^* Using, for example, Vw ^* = Vi × S ^* Asking.
Also, Vwd ^* Is a target value of the wheel acceleration, here, for example, Vwd ^* = 1.2 g or the like.
[0063]
In this manner, the slip ratio So having the μ peak is focused on and estimated, and the target value Vw is adjusted accordingly. ^* Is set or changed, the target pressure increase / decrease amount ΔP of the ABS control is set. ^* Is set appropriately. Then, when the duty ratio control for the outlet valve is performed in the following processing, it is possible to always control the slip with the road surface μ peaking as a target.
[0064]
That is, as described above, the target pressure increase / decrease amount ΔP ^* Is calculated, the calculated value ΔP ^* (See step S209 in FIG. 6). In the next step S108, the solenoid valve drive pulse duty is output for the drive pulse output process to the solenoid valves provided in each channel as the outlet valves 13 to 43 (step S109). The duty ratio of the outlet valve is executed by calculating the ratio and outputting a drive pulse each time step S109 is executed based on the ratio.
FIGS. 5 and 6 show an example of the solenoid valve drive pulse / duty ratio calculation routine.
In this embodiment, the W / C pressure of the corresponding channel is controlled by always increasing the pressure and then reducing the pressure.
[0065]
In FIG. 5, first, a master cylinder pressure is estimated in step S200. In the present embodiment, it is assumed that the M / C pressure rises at a certain slope in response to the on signal of the brake SW 55, for example, the maximum M / C pressure is set to 16 MPa, and the maximum M / C pressure rises to the maximum M / C pressure. Here, in order to further improve the accuracy, the M / C pressure may be corrected according to the deceleration during the ABS operation.
Next, in step S201, the W / C pressure (Pw / ci) is estimated.
In the present embodiment, it is assumed that the W / C pressure is estimated from the previous pulse duty ratio calculated by a method described later (see the following steps).
[0066]
Then, in step S202 and thereafter, the solenoid valve drive pulse / duty ratio is calculated.
More specifically, first, in step S202, an initial value of the pulse duty ratio DT is set.
In this program example, DT = 0.
Note that, as described above, DT represents the time during which the outlet valve is closed during the pulse output period T (for example, T = 50 msec), and is defined as, for example, DT = 10 msec. In the case of the above initial value, that is, in the case of DT = 0, it means that the pressure is fully reduced (the open position is maintained and the valve is kept open for the entire period of T = 50 msec). Further, when DT ≠ 0, for example, in the case of DT = 10 msec, this means that in the period T = 50 msec, the outlet valve is in the closed position for 10 msec, and is in the open position for 40 msec. Will do.
[0067]
Next, in step S203, it is determined whether the value DT is 0. Here, when DT = 0, since the pressure is full as described above, the process proceeds to step S204, and the pressure increase amount is set to zero, that is, ΔPinc = 0. Then, the process proceeds to step S206. On the other hand, if DT ≠ 0 (including DT = T), the pressure is increased (or only the pressure is increased (slowly increased)), so that the process proceeds to step S205 to estimate the increased pressure amount.
[0068]
The contents of this processing are as follows.
That is, in step S205, the pressure increase amount ΔPinc is calculated from the M / C pressure, the current W / C pressure, and the duty ratio DT by using, for example, an actuator model (characteristic) as shown in FIG. The value ΔPinc is applied to the calculation in the next step S206 and a later-described step S209. In this example, for example, based on the characteristic when DT = 5 msec, the actuator model (characteristic) is And the pressure increase amount ΔPinc at DT = 5 msec is calculated from the M / C pressure and the current W / C pressure. For example, when DT = 10 msec, the pressure increase amount ΔPinc is doubled to simplify the model. ing.
[0069]
Here, in the present embodiment, the pressure increase amount ΔPinc at the time of DT = T is the ΔPw / c value (the above-described equation 7) used for estimating the road surface μ in the next loop.
In the present example, as the variation of the W / C pressure used for estimating the road surface μ, the estimated pressure increase amount when DT = T can be used as it is.
[0070]
Next, in step S206, the W / C pressure Pw / ciM (referred to as an estimated intermediate value) after pressure increase is estimated from the W / C pressure Pw / ci and the pressure increase amount ΔPinc estimated in step S205.
That is,
(Equation 10)
W / C pressure after pressure increase Pw / ciM = Pw / ci + ΔPinc 10
The W / C pressure after the pressure increase is calculated.
[0071]
Next, in step S207, the pressure reduction time DTD is calculated by subtracting the duty ratio DT from the pulse output period T from the following equation (11).
(Equation 11)
DTD = T−DT 11
[0072]
Then, the pressure reduction amount is estimated in step S208.
In the present embodiment, the pressure reduction amount ΔPdec is calculated from the estimated intermediate value Pw / ciM estimated in step S206 and the pressure reduction time DTD obtained as described above, for example, using an actuator model (characteristic) as shown in FIG. The calculated value ΔPdec is applied to the calculation in the next step S209 together with the pressure increase amount ΔPinc.
Here, as shown in FIG. 8, the depressurization side is basically the same as the depressurization time (step S205, FIG. 7), for example, the characteristics when the depressurization time DTD = 5 msec. For example, the model is simplified.
[0073]
When the estimated pressure increase amount and the estimated pressure decrease amount are obtained as described above, it is determined whether or not the current duty ratio DT is appropriate in the next step S209 and thereafter (FIG. 6).
First, in step S209, the target pressure increase / decrease amount ΔP calculated in step S107 (FIG. 4) is used. ^* ΔPn, which is the difference between the estimated pressure increase amount ΔPinc and the estimated change amount ΔPdec obtained in steps S205 and S208, respectively (that is, ΔPinc−ΔPdec),
(Equation 12)
ΔPn = ΔP ^* − (ΔPinc−ΔPdec) 12
Is calculated by
[0074]
Next, in step S210, it is determined whether the difference value ΔPn is positive or negative. If ΔPn ≦ 0 is not established as a result of this determination, that is, if ΔPn is positive, it means that the current duty ratio DT has not increased or decreased to the target increase / decrease amount (there is a large amount of decrease). The process advances to step S211 to check whether DT <T.
As a result, if DT <T, that is, if the pressure increase time has not reached the pulse output period T and the pressure increase amount can still be increased, the process proceeds to step S212, where the duty ratio is incremented and Returning to the upstream of S203 (FIG. 5), the duty ratio after the increment is applied, and the estimation is performed again according to the processing described above. In this case, the processing of steps S203 → S205 → S206 → S207 → S208 → S209 is repeated, and in the process, the determination of step S210 and, if applicable, further step S211 are performed.
[0075]
Here, in step S212, the increment is incremented by one (DT = DT + 1). However, if the basic actuator model (characteristic) applied in step S205 is DT = 5 msec (FIG. 7), the increment is made. In the process, the value is incremented by 5 (this is the same in the case of the decrement process in step S214 described later).
[0076]
Thus, if DT <T, DT is incremented. If DT = T, DT cannot be increased any more, so DT = T (slow pressure increase) is determined.
When the present calculation routine is terminated in this way, in step S109 (FIG. 4), the form of the drive pulse output is set so that the outlet valve takes the closed position over the entire period of T = 50 msec. Output processing.
[0077]
When the difference value ΔPn is calculated in step S209 and the process proceeds to step S210, on the contrary, if ΔPn is negative or zero, it can be determined that the target pressure increase / decrease amount is sufficiently possible with the current duty. , The process proceeds to step S213 and thereafter, and the present arithmetic routine ends.
[0078]
In this program example, the previous ΔPn-1 value (the target pressure increase / decrease amount ΔP ^* (The difference between the estimated pressure increase amount ΔPinc and the estimated total pressure change amount ΔPdec) and the current ΔPn (current value), and the smaller one is selected. That is, if | ΔPn | ≧ | ΔPn−1 | in step S203, the value DT is decremented in step S214 so as to select the previous duty ratio. By doing so, the target amount ΔP required for the anti-skid control ^* In contrast to (Step S107), it is better to select the immediately preceding duty ratio so that | ΔPn | ≧ | ΔPn−1 | ^* This is because it can be controlled to a value close to. Therefore, when the duty ratio DT is set in this way, the decrement process is performed, and the pulse duty ratio DT corresponding to the immediately preceding duty ratio is applied to the process of step S109 (FIG. 4), and as a result, The corresponding drive pulse is output to execute the duty control, and the target amount ΔP ^* Is performed in accordance with the hydraulic pressure.
[0079]
Conversely, if | ΔPn | <| ΔPn−1 | (this means that, contrary to the above, the difference value calculated by Expression 12 is smaller in the current calculation value) The duty ratio DT is set to the target amount ΔP by performing the duty control at the current duty ratio, rather than by setting the duty ratio DT to be equivalent to the immediately preceding duty ratio. ^* Therefore, the present routine is terminated without performing the decrement in step S214 to select the duty ratio this time, the process proceeds to the process in step S109 in FIG. Is terminated.
Also in this case, as described above, the pulse duty ratio DT that can be controlled to a value closer to the target is set, and this is applied to the drive pulse output processing. As a result, appropriate outlet valve duty control is executed, and Target value ΔP in skid control ^* The hydraulic pressure can be controlled in accordance with
[0080]
FIG. 9 shows an example in which outlet valve duty control is performed.
To explain, it is assumed that the current W / C pressure is Pw / co and the current time is to. When DT = 0 (n = 0 at this time), the pressure is reduced until time t + T during the period T. In this case, the target pressure increase / decrease amount ΔP ^* ΔPn between the total change amount of the estimated pressure increase amount ΔPinc and the estimated pressure decrease amount ΔPdec is ΔPo = ΔP ^* + ΔPdec (o). Since ΔPo> 0 and DT <T (FIG. 6, steps S210 and 211), DT is incremented (step S212) and the estimation is performed again. This is repeated, for example, when DT = n−1, first, the pressure increase amount ΔPinc (n−1) is estimated, the estimated intermediate value Pw / cMn−1 is calculated, and ΔPn−1 is obtained. At this time, the estimated final W / C pressure is set to Pw / cn-1. Also at this time, since DT <T when ΔPn−1> 0, the estimation is performed again.
When DT = n, Pw / cMn and ΔPn are similarly obtained. At this time, ΔPn ≧ 0 for the first time, and as described above, in the next step (the same step S213), the magnitude of | ΔPn | when DT = n and | ΔPn-1 | when DT = n−1 Then, it is determined which one can be selected to control the value closer to the target.
In the case of the example shown in the figure, DT = n is selected because | ΔPn | ≦ | ΔPn−1 | as shown in the figure. In this case, the outlet valve duty control is executed according to the selection as described above.
[0081]
When the ABS actuator is controlled by performing the above-described drive pulse duty ratio calculation (step S108, FIGS. 5 and 6) according to the present program example, the target pressure increase / decrease command which is the pressure increase / decrease command by the anti-skid control. Quantity ΔP ^* In contrast to (Step S107), the pressure increase amount ΔPinc at the time of pressure increase in accordance with the off / on of the outlet valve drive pulse and the pressure decrease amount ΔPdec at the time of the subsequent pressure decrease are estimated, whereby the fluid in each cycle T is obtained. A process of calculating the drive pulse duty ratio DT while estimating the pressure can be performed, and it is possible to control to an arbitrary hydraulic pressure while constantly estimating the hydraulic pressure. Therefore, basically, even in the two-mode control of the slow pressure increase mode and the pressure reduction mode using the throttle, the controllability is improved, and therefore, even if it is required to maintain the hydraulic pressure, it can be easily responded to this. Then, if necessary, for example, holding at an arbitrary liquid pressure (holding mode by a combination of increasing and decreasing pressure) as shown in FIG. _SOL Indicates a drive pulse of the outlet valve). In practice, the duty ratio control of the drive pulse for the outlet valve, which is one solenoid valve per channel, enables a three-mode ABS control, and has a simple and inexpensive configuration. Effective ABS control can be performed.
[0082]
Therefore, as in the case of the previously proposed anti-skid control device by the present applicant, when the brake fluid pressure control for avoiding the wheel lock is realized, the device configuration and control are improved, and the fluid pressure is maintained. Therefore, it is not necessary to add a special switch means, so that the size / cost is not increased, and only one solenoid valve is required for each channel, and if additional hardware is added. It is also advantageous that no fail-safe measures need to be taken for the additional parts that would be needed.
[0083]
In addition to this, in the present embodiment, in the anti-skid device utilizing the slow pressure increase effect of such a throttle, the target pressure increase / decrease amount ΔP ^* The anti-skid control content is calculated by calculating the road surface μ change amount from the pressure increase amount during gradual pressure increase and the wheel slip change amount, estimating the road surface μ, and paying attention to the slip ratio So that takes the μ peak. Is changed (steps S104 to S106), the optimal control according to the road surface μ is performed.
[0084]
FIG. 12 is a timing chart of various quantities showing an example when the above-described control of the present embodiment is executed.
FIGS. 7A to 7D respectively show changes and changes of the wheel speed Vw, the pseudo vehicle speed Vi, the slip ratio S, the road surface μ change amount Ks, and the W / C pressure Pw / c during the ABS operation. As a result, on an actual road surface, it is possible to control the slip amount to an optimum value according to the road surface μ characteristic.
Although two typical μ-S characteristics are shown in FIG. 11 above, the method (the control threshold value or the target value is determined by using the anti-skid device and the individual vehicle In the case of a system that exclusively adopts a method of setting to a certain value by tuning when applying to the control and making a comparison with this value during control), for example, the μ-s characteristic as shown in FIG. Even if the road surface is different, based on the slip amount and the wheel acceleration, it is controlled uniformly according to the set target slip amount, and the maximum μ slip is not necessarily used effectively. In contrast to this, according to this control, it is possible to control the slip at which the road surface μ becomes a peak, and as a result, optimal control is performed on any road surface condition of the dry road and the wet road, ABS control Ri it is possible to optimally perform, thereby, be such reduction effect of the deceleration decreases and rudder according rice too and vent too much W / C pressure and the like can be prevented.
[0085]
In particular, in the case of an ABS having one two-position valve per channel based on two modes of rapid pressure reduction and gentle pressure increase, the control mode is depressurized once more than necessary. If so, since the increase of the W / C pressure is slow, problems such as insufficient deceleration occur, and at that time, recovery is difficult to be effective as in the case of having a rapid increase mode. Therefore, from this point, when depressurizing, it becomes important to perform the necessary minimum depressurization. For that purpose, it is a big point that the road surface μ can be estimated. Such a request can be easily met, and a situation such as insufficient deceleration can be appropriately avoided even with the two-mode ABS.
[0086]
Further, in this case, the pressure increase amount during the gradual pressure increase used to calculate the road surface μ change amount for road surface μ estimation is determined by the estimated pressure increase amount (step S108) in the drive pulse duty ratio DT calculation (step S108). As described above, when combined with a technique used as a ΔPinc) value, it is not necessary to add a hydraulic pressure sensor for detecting the W / C pressure as a new hardware, as described above. There is no need to take fail-safe measures due to increased costs or additional sensors, so an even more improved anti-skid control device that exhibits sufficient anti-skid performance with a less expensive system Can be realized.
[0087]
Note that the present invention is not limited to the above embodiments and the like.
For example, in the above control, when considering the wheel cylinder pressure increase / decrease cycle, the control at the current pressure increase is determined based on the road surface μ estimated at the time of the previous wheel cylinder pressure increase / decrease cycle. Instead of estimating the road surface μ only in accordance with one estimation, the target slip amount for control may be obtained by averaging several estimations.
[0088]
Further, for example, in the above example, the road surface μ is estimated, and the ABS control is performed by focusing on the slip ratio So that takes a μ peak. However, the control change according to the road surface μ may be performed by focusing on the μ peak itself. Good. For example, at low μ, the target pressure increase / decrease amount ΔP ^* Is calculated, the target value Vwd of the wheel acceleration is calculated. ^* To Vwd ^* = 1.2g + β (β is changed depending on the road surface μ peak).
[0089]
Further, for example, in the case of combining with the drive pulse duty ratio calculation processing, in the above example, the estimation of the pressure increase amount at the time of pressure increase according to the OFF / ON of the solenoid valve drive pulse and the estimation of the pressure decrease amount at the time of the subsequent pressure decrease are performed. This is performed, for example, in a mode of estimating the amount of pressure reduction at the time of pressure reduction in accordance with ON / OFF of the solenoid valve drive pulse and estimating the amount of pressure increase at the time of subsequent pressure increase. It is widely applicable to the improved embodiment.
No.
[0090]
In the above description, a four-channel ABS is taken as an example, but it goes without saying that the present invention can be similarly applied to a three-channel ABS.
Also, for example, a preferred example of an ABS actuator having an inlet valve and an outlet valve is shown in FIG. 1, but it is not limited to the illustrated one.
[0091]
【The invention's effect】
According to the present invention, in the anti-skid control for avoiding wheel lock during braking, in the case of one solenoid valve per channel utilizing the slow pressure increase effect of the throttle, the pressure increase amount during the slow pressure increase and the wheel slip The amount of change in the road surface μ is calculated from the amount of change, the road surface μ is estimated based on the calculated amount, and the content of the anti-skid control can be changed accordingly. Can be regarded as almost constant at the time of gradual pressure increase, and the road surface μ can be estimated by making use of the characteristic that the pressure increase amount per unit time is constant, and optimal control appropriate for the road surface μ is performed appropriately. It is possible to provide an anti-skid control device which can be controlled to exert sufficient anti-skid performance even when using an inexpensive system.
[0092]
In this case, preferably, the present invention can be implemented as a configuration in which the electromagnetic valve is a two-position valve, and preferably, when the electromagnetic valve is in anti-skid control, the brake fluid of the wheel cylinder is in its closed position. The valve is a solenoid valve that is driven and controlled by a supplied pulse signal so as to shut off the drainage of the brake fluid at the valve closing position. The path from the master cylinder to the wheel cylinder includes an upstream side and a downstream side. The present invention can be implemented as a valve having a valve that is driven by a pressure difference between the valve and a valve that slowly increases the pressure in anti-skid control by a throttle. Preferably, further, a wheel speed calculating means for calculating a wheel speed from an output from a wheel speed sensor, a vehicle speed estimating means for estimating a vehicle speed from the wheel speed, a wheel acceleration calculating means for calculating a wheel acceleration from the wheel speed, The present invention can be implemented by including a means for calculating the amount of pressure increase / decrease from the wheel speed, the wheel acceleration, and the estimated vehicle speed, and a drive pulse output means for outputting a drive pulse.
[0093]
Further, the present invention can be implemented by estimating the road surface μ from the history of the road surface μ change amount as described in claim 2, and the above can be realized similarly. In this case, an appropriate μ-S characteristic can be estimated by looking at the history.
[0094]
Further, the slip ratio at which the μ peak is obtained is estimated by the estimating means, and the target slip amount or the slip amount threshold value of the anti-skid control, the target wheel acceleration or the wheel acceleration threshold value is determined accordingly. The present invention can be implemented by making any of the modifications described above, and the above can be similarly realized.
In addition, in this case, for example, it is excellent in correspondence with a road surface having different μ-S characteristics such as a dry road and a wet road, and the maximum μ slip can be effectively utilized, and the slip at which the road μ reaches a peak is reduced. The target can be controlled, which is effective in preventing a decrease in deceleration and a decrease in rudder effectiveness due to excessively injecting and extracting wheel cylinder hydraulic pressure.
[0095]
In the case of claim 4, the driving pulse duty ratio calculation means is further provided, and the pressure increase amount estimated by the calculation means is applied to the pressure increase amount during the gradual pressure increase. In this case, the present invention can be implemented, and the same can be realized in the same manner. In this case, by further providing the drive pulse duty ratio calculation means, it is More effective anti-skid, for example, the duty mode of the drive pulse for one solenoid valve per channel can easily and easily achieve a holding mode capable of holding at any hydraulic pressure. Control can be realized, and the estimated pressure increase calculated in the process of the duty ratio calculation is used for estimating the road surface μ. No additional sensor is required, and there is no need to take additional measures such as increased costs and fail-safe measures due to the addition of the sensor, which is even more advantageous and provides sufficient anti-skid performance with a less expensive system. An effective anti-skid control device can be realized.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a configuration of an embodiment of the present invention.
FIG. 2 is a functional block diagram illustrating an example of a basic configuration of control contents in the same example.
FIG. 3 is a diagram for explaining the principle of estimating a road surface μ and the like;
FIG. 4 is a flowchart illustrating an example of a control program executed by the controller of the example.
FIG. 5 is a flowchart showing a part of an example of a solenoid / valve drive pulse / duty ratio calculation routine in the same program.
FIG. 6 is a flowchart showing another part.
FIG. 7 is a diagram illustrating an example of an actuator model that can be applied to the routine and is used for estimating a pressure increase amount.
FIG. 8 is a diagram showing an example of an actuator model used for estimating a reduced pressure amount, which can be applied to the same routine.
FIG. 9 is a diagram for explaining control by a drive pulse duty ratio calculation routine.
FIG. 10 is a diagram exemplifying an outline of two-mode ABS control in a case where the hydraulic pressure is also maintained.
FIG. 11 is an explanatory diagram provided for explanation of μ peak estimation, road surface μ change amount, and the like.
FIG. 12 is an example of a timing chart for explaining control contents.
FIG. 13 is a diagram showing various examples of μ-S characteristics.
[Explanation of symbols]
1 brake pedal
2 Booster
3 reservoir
4 Master cylinder
5 Motor
6,7 pump
8, 9 reservoir
10,20 Left and right front wheels
11, 21, 31, 41 Wheel cylinder
12, 22, 32, 42 Inlet valve (mechanical type)
13,23,33,43 Outlet valve (solenoid valve)
30, 40 Left and right rear wheels
50 Controller
51,52,53,54 Wheel speed sensor
55 Brake switch (SW)

Claims (2)

An anti-skid device controlled by one solenoid valve per channel utilizing a gradual pressure increase effect by a throttle;
Estimating means for calculating a road surface μ change amount from the pressure increase amount during the gradual pressure increase and a wheel slip change amount, and estimating a road surface μ-slip ratio characteristic based on the road surface μ change amount;
Control change means for changing the content of anti-skid control according to the estimation means,
The estimating means estimates the road surface μ-slip ratio characteristic from the history of the road surface μ change amount,
The change of the control content is as follows:
The slip ratio having the μ peak is estimated by the estimating means, and either the target slip amount or the slip amount threshold value of the anti-skid control or the target wheel acceleration or the wheel acceleration threshold value is changed accordingly. ,
An anti-skid control device, characterized in that: An anti-skid device controlled by one solenoid valve per channel utilizing a gradual pressure increase effect by a throttle;
Estimating means for calculating a road surface μ change amount from the pressure increase amount during the gradual pressure increase and a wheel slip change amount, and estimating a road surface μ-slip ratio characteristic based on the road surface μ change amount;
Control changing means for changing the anti-skid control content according to the estimating means,
In response to the pressure increase / decrease command of the anti-skid control, the pressure increase or pressure decrease during pressure increase or pressure reduction is estimated, and then the pressure decrease or pressure increase during pressure reduction or pressure increase is estimated. Drive pulse duty ratio calculation means for calculating the duty ratio of the drive pulse output to the solenoid valve while estimating the hydraulic pressure for each,
The pressure increase amount estimated by the calculation means is applied to the pressure increase amount during the gradual pressure increase.
An anti-skid control device, characterized in that:

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