JP3756978B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

【００４０】
【数２】

【００４１】
【数３】

【００４２】
【数４】

【００４３】
ここで、数３に示される適応パラメータθハットは、ゲインを決定するスカラ量ｂ0 ハット^-1(k) 、操作量を用いて表現される制御要素ＢR ハット(Z^-1, k)および制御量を用いて表現される制御要素Ｓハット（Z ^-1, k)からなり、それぞれ数５から数７のように表される。
【００４４】
【数５】

【００４５】
【数６】

【００４６】
【数７】

【００４７】
パラメータ調整機構はこれらのスカラ量や制御要素の各係数を同定・推定し、前記した数３に示す適応パラメータθハットとして、ＳＴＲコントローラに送る。パラメータ調整機構は、プラントの操作量ｕ（ｉ）および制御量ｙ（ｊ）（ｉ，ｊは過去値を含む）を用いて目標値と制御量との偏差が零となるように適応パラメータθハットを算出する。適応パラメータθハットは、具体的には数８のように計算される。数８で、Γ(k) は適応パラメータの同定・推定速度を決定するゲイン行列（ｍ＋ｎ＋ｄ次）、ｅアスタリスク(k) は同定・推定誤差を示す信号で、それぞれ数９および数１０のような漸化式で表される。尚、数１０においてＤ（ｚ^-1）は設計者が与える所望の漸近安定な多項式であり、この例では１に設定される。
【００４８】
【数８】

【００４９】
【数９】

【００５０】
【数１０】

【００５１】
また数９中のλ１(k) ，λ２(k) の選び方により、種々の具体的なアルゴリズムが与えられる。例えば、λ１(k) ＝１，λ２(k) ＝λ（０＜λ＜２）とすると漸減ゲインアルゴリズム（λ＝１の場合には最小自乗法）、λ１(k) ＝λ１（０＜λ１＜１），λ２(k) ＝λ２（０＜λ２＜λ）とすると可変ゲインアルゴリズム（λ２＝１の場合には重み付き最小自乗法）、λ１(k) ／λ２(k) ＝σとおき、λ３が数１１のように表されるとき、λ１(k) ＝λ３(k) とおくと固定トレースアルゴリズムとなる。また、λ１(k) ＝１，λ２(k) ＝０のとき固定ゲインアルゴリズムとなる。この場合は数９から明らかな如く、Γ(k) ＝Γ(k-1) となり、よってΓ(k) ＝Γの固定値となる。燃料噴射ないし空燃比などの時変プラントには、漸減ゲインアルゴリズム、可変ゲインアルゴリズム、固定ゲインアルゴリズム、および固定トレースアルゴリズムのいずれもが適している。尚、数１１においてtrΓ(0) はΓの初期値のトレースである。
【００５２】
【数１１】

【００５３】
ここで、図４にあっては、前記したＳＴＲコントローラ（適応制御器）と適応パラメータ調整機構とは燃料噴射量演算系の外におかれ、検出空燃比KACT(k) が目標空燃比KCMD(k-d’) （ここでｄ’は先にも触れたが、KCMDがKACTに反映されるまでの無駄時間を示し、よって無駄時間制御周期前の目標空燃比を意味する）に適応的に一致するように動作してフィードバック補正係数KSTR(k) を演算する。即ち、ＳＴＲコントローラは、適応パラメータ調整機構によって適応的に同定された係数ベクトルθハット(k) を受け取って目標空燃比KCMD(k-d’）に一致するようにフィードバック補償器を形成する。演算されたフィードバック補正係数KSTR(k) は各種補正項と共に基本噴射量Ｔimに乗算され、補正された燃料噴射量が出力燃料噴射量Ｔout(k)として制御プラント（内燃機関）に供給される。
【００５４】
このように、適応補正係数KSTR(k) および検出空燃比KACT(k) が求められて適応パラメータ調整機構に入力され、そこで適応パラメータθハット(k) が算出されてＳＴＲコントローラに入力される。ＳＴＲコントローラには入力として目標空燃比KCMD(k) が与えられ、検出空燃比KACT(k) が目標空燃比KCMD(k-d')に一致するように漸化式を用いて適応補正係数KSTR(k) を算出する。
【００５５】
適応補正係数KSTR(k) は、具体的には数１２に示すように求められる。
【００５６】
【数１２】

【００５７】
図５フロー・チャートに戻ると、次いでＳ１０６に進み、かく求めた適応補正係数KSTRをフィードバック補正係数KFB とする。
【００５８】
他方、Ｓ１００でフィードバック制御領域ではないと判断されたときはＳ１０８に進んで適応補正係数KSTRを１．０としてＳ１０６に進む。フィードバック補正係数は供給燃料量に乗算されてそれを補正することから、１．０としたことは換言すれば、フィードバック制御を行わないことを意味する。
【００５９】
またＳ１０２で前回フィードバック制御領域ではなかったと判断されるときは、オープンループ制御領域からフィードバック制御領域に突入したことになるので、Ｓ１１０に進んで適応補正係数KSTRが１ないしその近傍となるように適応制御則の内部変数を過去値も含めて設定する。
【００６０】
これについて説明すると、先に述べた適応パラメータ調整機構は、ζ(k-d) 、即ち、プラント入力ｕ(k) （＝KSTR(k) ）およびプラント出力ｙ(k) （＝KACT(k) ）の現在値および過去値をひとまとめにしたベクトルを入力し、その因果関係から適応パラメータθハット(k) を算出する。ここで用いるｕ(k) は今述べたように、供給燃料量の補正に使用される補正係数である。
【００６１】
このように、フィードバック制御領域外、即ち、適応制御領域外から適応制御を開始する場合、ζ(k-d) 、θハット(k-1) 、ゲイン行列Γ(k-1) などの内部変数の過去値がないと、正しい適応補正係数KSTRを演算することができないか、最悪の場合には発振してしまう恐れがある。
【００６２】
そこで、ｕ(k-i) ＝１（ｉ≧１）としたとき、適応補正係数KSTRが１ないしその近傍となるように、適応パラメータθハット(k) を設定すると共に、ζ(k-d) を数１３のように設定する。尚、ゲイン行列Γ(k-1) は適応速度を決定する値なので、初期値などの所定の行列値とする。
【００６３】
【数１３】

【００６４】
より具体的には、適応補正係数KSTRは数１２のように演算されるので、そこで適応補正係数KSTRが１ないしその近傍となるようなθハット(k-1) およびζ(k-d) を考える。
【００６５】
例えば目標空燃比KCMD(k-d' ) が１のとき、KSTR(k-1) ＝KSTR(k-2) ＝KSTR(k-3) ＝１．０とおき、適応パラメータθハット(k) の制御要素などの要素の初期値を
ｒ1 ＝０．１
ｒ2 ＝０．０５
ｒ3 ＝０．０５
ｓo ＝０．３
ｂo ＝０．５
とすると、検出空燃比KACT(k) が１のとき、適応補正係数KSTRは、
KSTR＝（１−０．１×１−０．０５×１−０．０５×１−０．３× KACT(k) ) ／０．５
となり、検出空燃比KACT(k) ≒１のとき、適応補正係数KSTR≒１となる。
【００６６】
これは、適応補正係数KSTR(k-i) （ｉ≧１）が１ないしその近傍、即ち、ほとんどフィードバック補正を行っていない状態で検出空燃比KACT(k-j) ( ｊ≧１）よりもずっと過去の目標空燃比KCMD(k-d' ) に一致して安定に制御されていた過去の状態を人為的に作り出していることに相当する。
【００６７】
これによってフィードバック制御を開始するときも同じ値から開始することになり、制御量がハンチングすることなく、空燃比のスパイクなどが生じることがなく、制御の安定性を向上する。尚、適応パラメータθハットの要素の初期値は、目標空燃比に応じて持ち替えても良い。
【００６８】
図３フロー・チャートに戻ると、次いでＳ２８に進んで基本燃料噴射量（供給燃料量）Ｔimに、目標空燃比補正係数KCMDM （目標空燃比KCMD（当量比）に吸入空気の充填効率補正を加えて得た値）と求めたフィードバック補正係数KFB と各種補正係数KTOTALとを乗算して補正すると共に、加算項TTOTALを加算して補正し、先に述べたように出力燃料噴射量Ｔout を決定し、次いでＳ３０に進んで出力燃料噴射量Ｔout を操作量としてインジェクタ２２に出力する。
【００６９】
ここで、各種補正係数KTOTALは水温補正など乗算で行う各種の補正係数の積算値を意味し、加算項TTOTALは気圧補正など加算値で行う補正係数の合計値を示す（但し、インジェクタの無効時間などは出力燃料噴射量Ｔout の出力時に別途加算されるので、これに含まれない）。
【００７０】
尚、Ｓ１８で否定されたときは空燃比がオープンループ制御となるので、Ｓ３２に進んでフィードバック補正係数KFB の値を１．０とし、Ｓ２８に進んで出力燃料噴射量Ｔout を求める。またＳ１２でクランキングと判断されたときはＳ３４に進んでクランキング時の燃料噴射量Ｔicr を検索し、Ｓ３６に進んで検索値に基づいて始動モードの式に従って出力燃料噴射量Ｔout を算出すると共に、Ｓ１４でフューエルカットと判断されたときは、Ｓ３８に進んで出力燃料噴射量Ｔout を零とする。
【００７１】
ここでＳ２０の無駄時間ｄ’の算出を説明する。
【００７２】
図６はその算出作業を示すサブルーチン・フロー・チャートであるが、同図の説明に入る前に、図７を参照してこの無駄時間を具体的に説明する。
【００７３】
同図は、目標空燃比KCMDから検出空燃比KACTへの無駄時間ｄ’を正確に反映させた適応制御器の目標値KCMD(k-d' ) 、即ち、適応補正係数KSTRの演算で用いる目標値（数１２参照）を用いた場合の検出空燃比KACTの挙動を示すタイミング・チャートである。この場合、KCMDからｄ’遅れてKACTが追従する。これによって所期の制御性を実現することができる。従って、この実施の形態においては、先ず目標値に応じて無駄時間ｄ’を変えるようにする。
【００７４】
次いで、意図的に無駄時間ｄ’を変えてドライバビリティなどを向上させる場合について述べると、意図的に変える無駄時間をｄ”とすると、
ｄ’＜ｄ”
と設定する。図８にそれを示す。
【００７５】
同図に示す如く、意図的に無駄時間を本来的な適正な値ｄ’と相違させているので、応答性は悪化する。これは、適応制御器が目標値の変化を実際の無駄時間より遅く反映させるからである。従って、検出値はなまされた値となり、リーンバーン機関などで目標空燃比を大幅に変化させるときなどは、このように意図的に適応制御器の応答性を低下させることで、かえってトルクショックが低減し、ドライバビリティが向上する。
【００７６】
上記を前提として図６フロー・チャートを説明すると、先ずＳ２００において目標値KCMD(k) に応じて、より詳しくは数１２に示す適応補正係数KSTRの演算で用いる目標空燃比KCMD(k-d' ) の無駄時間ｄ’を設定する。即ち、検出された空燃比に対応する時間、より具体的には時刻(k-d')前の目標値が現在時刻(k) の値として検出されたように、両者を対応させる。これによって、本来的に意図する制御性を挙げることができる。
【００７７】
次いでＳ２０２に進んで目標空燃比の今回値KCMD(k) と前回値KCMD(k-1) の差DKCMD 、即ち、目標空燃比がリッチ側に変化したかリーン側に変化したかを判別するために差分を求め、Ｓ２０４に進んで求めた差DKCMD が基準値DKCMDREFを超えているか否か判断する。ここでは基準値DKCMDREFを適宜設定することで、目標空燃比がリッチ方向へ変化したか否か判断する。
【００７８】
Ｓ２０４で肯定されるときはＳ２０６に進んで適正な無駄時間ｄ’に正の値ａを加算し、Ｓ２０８に進んでカウンタＣの値をインクリメントする。そして次回以降のプログラム起動時（制御周期）にＳ２０４で肯定される限りＳ２０６，Ｓ２０８に進んでカウンタ値をインクリメントし続け、Ｓ２１０でカウンタ値が所定値ＣREF を超えたと判断されるとＳ２１２に進んでカウンタＣの値を零にリセットする。このとき、上記から明らかな如く、適応補正係数KSTRは無駄時間をｄ”として演算されるので、KACTの挙動は、カウンタ値ＣREF に相当する期間にわたって、図８に示す如くなまされたものとなる。
【００７９】
この実施の形態は上記の如く、先ずＳ２００において目標値KCMD(k) に応じて適応補正係数KSTRの演算で用いる目標空燃比KCMD(k-d' ) の無駄時間ｄ’を適正に設定するようにしたので、ＬＡＦセンサの応答性に応じて所期の検出値を得ることができ、本来的に予定する制御性を得ることができる。従って、その目的を達成するにはＳ２００のみで足り、Ｓ２０２以下は不要である。
【００８０】
更に、今述べた適正な無駄時間を故意に増加してKACTの挙動がなまされるようにしたので、リーンバーン機関において空燃比がリーン側からリッチ方向に変化するときなど、機関の出力トルクが平滑化されてショックが低減され、ドライバビリティを向上させることができる。
【００８１】
図９はこの発明の第２の実施の形態を示す、図６の部分フロー・チャートである。
【００８２】
第２の実施の形態では、図６フロー・チャートのＳ２０６に相当するＳ２０６ａにおいて無駄時間を適正値ｄ’から正の値ｂを減算することで無駄時間を減少させるようにした。図１０にそのときのKACTの挙動を示す。図示の如く、KACTは逆にオーバーシュートする。
【００８３】
従って、例えば、燃料の吸気管付着補正を行うに際し、機関回転数および吸気圧力Ｐｂに対して常温において付着補正値を予めマップ値として設定しておき、検出回転数などから検索するとき、そのマップを低水温時にも代用する場合などにおいては
ｄ’＞ｄ”
とすることにより、図１０に示す如く、意図的に過補正にすることで付着補正の不足を補うことができる。
【００８４】
上記は、第１の実施の形態の
ｄ’＜ｄ”
のアンダーシュート特性と対をなすものであるので、第１の実施の形態ないし第２の実施の形態の特性を任意に選択することにより、空燃比のスパイクを任意に打ち消すように動作させることが可能となることも意味する。
【００８５】
また第１の実施の形態の始めで述べたように本来的に適正な無駄時間ｄ’を与えることで所期のKACTの挙動を得ることもでき、その全てを含む意味で請求項において「運転状態に応じて」と記載した。またここでの詳細な説明は省略するが、排気マニホルド２４の容積を可変にするとき、ないしは可変バルブタイミング機構３００の特性を変化させるときなども、それに応じて無駄時間を調整する必要があるが、その際にも上記を用いることができる。
【００８６】
尚、第１および第２の実施の形態においてフィードバック補正係数として適応制御則を用いた適応補正係数のみ用いたが、それ以外にＰＩＤ制御則を用いた低応答のＰＩＤ補正係数を用意し、フィードバック制御領域において適宜切り換えるようにしても良い。
【００８７】
また第１および第２の実施の形態では目標値を空燃比としたが、燃料噴射量そのものを目標値としても良い。
【００８８】
また第１および第２の実施の形態においてフィードバック補正係数KSTRを乗算係数（項）として求めたが、加算項であっても良い。
【００８９】
また第１および第２の実施の形態においてスロットル弁１６をパルスモータで作動したが、アクセルペダルと機械的にリンクさせ、アクセルペダルの動きに応じて作動しても良い。
【００９０】
また第１および第２の実施の形態において適応制御器としてＳＴＲを例にとって説明したが、ＭＲＡＣＳ（モデル規範型適応制御）を用いても良い。
【００９１】
【発明の効果】
請求項１項にあっては、制御性を向上させることができると共に、逆に意図的に変えることでドライバビリティなどを向上させることができる。
【００９２】
また、目標空燃比が特に大きく変化するような状態であっても、その空燃比の変動に対して適切な所定時間を与えて制御性を向上させることができると共に、その過渡状態では所定時間を意図的に変えることで、ドライバビリティを向上させることができる。
【図面の簡単な説明】
【図１】この発明に係る内燃機関の燃料噴射制御装置を全体的に示す概略図である。
【図２】図１の装置の制御ユニットの構成を詳細に示すブロック図である。
【図３】図１の装置の動作を示すフロー・チャートである。
【図４】図１の装置の動作を機能的に示すブロック図である。
【図５】図３フロー・チャートのフィードバック補正係数KFB の演算作業を示すサブルーチン・フロー・チャートである。
【図６】図３フロー・チャートの無駄時間の算出作業を示すサブルーチン・フロー・チャートである。
【図７】図６フロー・チャートの算出作業を説明する、目標値に対する検出値の挙動を示すタイミング・チャートである。
【図８】図６フロー・チャートの算出作業を説明する、図７と同様な目標値に対する検出値の挙動を示すタイミング・チャートである。
【図９】この発明の第２の実施の形態を示す、図６フロー・チャートの部分図である。
【図１０】図９フロー・チャートの算出作業を説明する、図７と同様な目標値に対する検出値の挙動を示すタイミング・チャートである。
【符号の説明】
１０ 内燃機関
２２ インジェクタ
３４ 制御ユニット
５４ 広域空燃比センサ（ＬＡＦセンサ）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine.
[0002]
[Prior art]
In fuel injection control or air-fuel ratio control of an internal combustion engine, a PID control law is generally used, and a P term (proportional term), I term (integral term), and D term are used as deviations between a target value and an operation amount (control target output). The feedback correction coefficient (feedback gain) is obtained by multiplying by (differential term). Recently, the feedback correction coefficient is obtained by using modern control theory as in the technique described in Japanese Patent Laid-Open No. 4-209940, for example. Has also been proposed.
[0003]
[Problems to be solved by the invention]
By the way, when modern control theory such as an adaptive control law is used and feedback control is performed using the supplied fuel amount as the operation amount so that the air-fuel ratio or the fuel amount matches the target value, the response of the sensor for detecting the air-fuel ratio is It changes when the air-fuel ratio is the stoichiometric air-fuel ratio and when it is lean.
[0004]
For this reason, for example, when the target air-fuel ratio changes greatly in a lean burn engine or the like, the dead time (the aforementioned predetermined period) from when the target air-fuel ratio is changed until the output of the air-fuel ratio sensor changes greatly changes. In principle, the controllability of the adaptive controller deteriorates unless the dead time is met.
[0005]
Therefore, a first object of the present invention is to provide a fuel injection control device for an internal combustion engine in which the controllability is improved by changing the dead time of the target value used for calculation by the adaptive controller in accordance with the operating state of the internal combustion engine. It is to provide.
[0006]
In other words, the above means that the controllability or responsiveness can be intentionally lowered by changing the dead time of the target value used for the calculation by the adaptive controller. For example, when switching from lean to the stoichiometric air-fuel ratio in a lean burn engine, it is possible to reduce torque shock by gradually following the change in the target air-fuel ratio, which is desirable in terms of drivability.
[0007]
Therefore, a second object of the present invention is to improve the drivability and the like by intentionally changing the dead time of the target value used for calculation by the adaptive controller according to the operating state of the internal combustion engine. A fuel injection control device is provided.
[0008]
[Means for Solving the Problems]
In order to achieve the first and second objects described above, according to claim 1, an operating state detecting means for detecting an operating state including an exhaust air-fuel ratio exhausted from the internal combustion engine, and supply of the internal combustion engine Supply fuel amount determining means for determining a fuel amount, and the detected exhaust air-fuel ratio using the supplied fuel amount as an operation amount, Equivalent to wasted time In a fuel injection control device for an internal combustion engine, comprising: a feedback correction coefficient calculating means for calculating a feedback correction coefficient using an adaptive controller so as to coincide with a target air-fuel ratio before a predetermined time, whether or not the target air-fuel ratio has been changed When it is determined that the change has been made, the predetermined time is Deliberately from the right value It was configured to increase or decrease.
[0010]
[Action]
In the first aspect, the detected exhaust air-fuel ratio is determined by using the supplied fuel amount as an operation amount. Equivalent to wasted time In a fuel injection control device for an internal combustion engine, comprising: a feedback correction coefficient calculating means for calculating a feedback correction coefficient using an adaptive controller so as to coincide with a target air-fuel ratio before a predetermined time, whether or not the target air-fuel ratio has been changed When it is determined that the change has been made, the predetermined time is Deliberately from the right value Since it is configured to increase or decrease, the controllability can be improved, and conversely, the drivability can be improved by intentionally changing the controllability.
[0011]
Here, the predetermined “ Time “Between” is used to include the number of predetermined crank angle intervals, or all periods indicated by time, time, and the like.
[0012]
Also Since the target value is configured to be an air-fuel ratio, even if the target air-fuel ratio changes particularly greatly, a predetermined value appropriate for the fluctuation of the air-fuel ratio is obtained. Time The controllability can be improved by giving a gap, and in the transient state, Time By deliberately changing the interval, drivability can be improved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0014]
FIG. 1 is an overall view showing a fuel injection control device for an internal combustion engine according to the present invention.
[0015]
In the figure, reference numeral 10 denotes an OHC in-line four-cylinder internal combustion engine. The intake air introduced from the air cleaner 14 disposed at the tip of the intake pipe 12 is adjusted with the surge tank 18 while the flow rate is adjusted by the throttle valve 16. It flows into the first to fourth cylinders via two intake valves (not shown) through the intake manifold 20. An injector 22 is provided near the intake valve (not shown) of each cylinder to inject fuel. The air-fuel mixture injected and integrated with the intake air is ignited by a spark plug (not shown) in each cylinder and burned to drive a piston (not shown).
[0016]
The exhaust gas after combustion is discharged to an exhaust manifold 24 through two exhaust valves (not shown), purified by a catalyst device (three-way catalyst) 28 via an exhaust pipe 26, and discharged outside the engine. . As described above, the throttle valve 16 is mechanically separated from the accelerator pedal (not shown), and is controlled through the pulse motor M to an opening degree corresponding to the depression amount of the accelerator pedal and the operating state. The intake pipe 12 is provided with a bypass path 32 that bypasses the throttle valve 16 in the vicinity of the position where the throttle valve 16 is disposed.
[0017]
The internal combustion engine 10 is provided with an exhaust gas recirculation mechanism 100 that recirculates exhaust gas to the intake side via a recirculation path 121, and is connected between the intake system and the fuel tank 36, and a canister / purging mechanism 200 is provided. However, since the mechanism has no direct relation with the gist of the present application, the description is omitted.
[0018]
The internal combustion engine 10 further includes a so-called variable valve timing mechanism 300 (shown as V / T in FIG. 1). The variable valve timing mechanism 300 is described in, for example, Japanese Patent Application Laid-Open No. 2-275043. The valve timing V / T of the engine is set to two timings according to the operating state such as the engine speed Ne and the intake pressure Pb. Switching between characteristics Lo V / T and Hi V / T. However, since this is a known mechanism, further explanation is omitted. The switching of the valve timing characteristics includes an operation of stopping one of the two intake valves.
[0019]
In FIG. 1, a crank angle sensor 40 for detecting a crank angle position of a piston (not shown) is provided in a distributor (not shown) of the internal combustion engine 10, and a throttle opening degree for detecting the opening degree of the throttle valve 16. An absolute pressure sensor 44 for detecting the intake pressure Pb downstream of the sensor 42 and the throttle valve 16 as an absolute pressure is also provided.
[0020]
Further, an atmospheric pressure sensor 46 for detecting the atmospheric pressure Pa is provided at an appropriate position of the internal combustion engine 10, and an intake air temperature sensor 48 for detecting the temperature of intake air is provided on the upstream side of the throttle valve 16. A water temperature sensor 50 for detecting the engine cooling water temperature is provided at an appropriate position. Further, a valve timing (V / T) sensor 52 (not shown in FIG. 1) for detecting a valve timing characteristic selected by the variable valve timing mechanism 300 via hydraulic pressure is also provided. Further, in the exhaust system, a wide area air-fuel ratio sensor 54 is provided in an exhaust system collecting portion downstream of the exhaust manifold 24 and upstream of the catalyst device 28. These sensor outputs are sent to the control unit 34.
[0021]
FIG. 2 is a block diagram showing details of the control unit 34. The output of the wide area air-fuel ratio sensor 54 is input to the detection circuit 62, where appropriate linearization processing is performed, and a detection signal having a linear characteristic proportional to the oxygen concentration in the exhaust gas is output in a wide range from lean to rich. (Hereinafter, this wide-range air-fuel ratio sensor is referred to as “LAF sensor”).
[0022]
The output of the detection circuit 62 is input into the CPU via the multiplexer 66 and the A / D conversion circuit 68. The CPU includes a CPU core 70, a ROM 72, and a RAM 74, and the output of the detection circuit 62 is A / D converted at predetermined crank angles (for example, 15 degrees) and sequentially stored in one of the buffers in the RAM 74. Similarly, an analog sensor output such as the throttle opening sensor 42 is taken into the CPU via the multiplexer 66 and the A / D conversion circuit 68 and stored in the RAM 74.
[0023]
The output of the crank angle sensor 40 is shaped by the waveform shaping circuit 76, and then the output value is counted by the counter 78, and the count value is input into the CPU. In the CPU, the CPU core 70 calculates a control value as will be described later according to a command stored in the ROM 72, and drives the injector 22 of each cylinder via the drive circuit 82. Further, the CPU core 70 is connected to the solenoid valve 90 (opening / closing of the bypass passage 32 for adjusting the secondary air amount), the exhaust recirculation control solenoid valve 122, and the canister / purge control solenoid via the drive circuits 84, 86, 88. The valve 225 is driven.
[0024]
FIG. 3 is a flowchart showing the operation of the control device according to the present invention. The program shown in FIG. 3 is started at a predetermined crank angle.
[0025]
In the illustrated apparatus, as shown in the block diagram of FIG. 4, the exhaust air-fuel ratio (shown as KACT (k) in the figure) detected using the supplied fuel quantity (shown as basic injection quantity Tim in the figure) as the manipulated variable is the target. A feedback correction coefficient (KSTR (in the figure is shown in the figure) using a recurrence type control law (STR type adaptive controller, shown in the figure as STR controller) so as to match the air-fuel ratio (indicated in the figure as KCMD (k)). A means for calculating k) is provided. For convenience of calculation, both the detected air-fuel ratio KACT and the target air-fuel ratio KCMD are actually indicated by an equivalent ratio, that is, Mst / M = 1 / λ (Mst: stoichiometric air-fuel ratio, M = A / F (A: air consumption, F: fuel consumption), λ: excess air ratio).
[0026]
In the following, the engine speed Ne and the intake pressure Pb detected at S10 are read out, and the routine proceeds to S12 where it is determined whether or not cranking is performed, and when the determination is negative, the routine proceeds to S14 where it is determined whether or not a fuel cut has occurred. The fuel cut is performed in a predetermined operating state, for example, when the throttle valve opening is in a fully closed position and the engine speed is equal to or greater than a predetermined value, the fuel supply is stopped, and the injection amount is controlled in an open loop. The
[0027]
If it is determined in S14 that the fuel cut is not performed, the process proceeds to S16, and a basic fuel injection amount Tim is calculated by searching a map from the detected engine speed Ne and intake pressure Pb. Next, the routine proceeds to S18, where it is determined whether activation of the LAF sensor 54 is completed. For example, the difference between the output voltage of the LAF sensor 54 and the center voltage thereof is compared with a predetermined value (for example, 0.4 v), and it is determined that the activation is completed when the difference is smaller than the predetermined value.
[0028]
When it is determined that the activation is completed, the process proceeds to S20, and a dead time d ′ is calculated. The dead time referred to here corresponds to the above-described predetermined period, and the dead time of the target value (target air-fuel ratio KCMD (kd ′)) used for calculating the feedback correction coefficient (adaptive correction coefficient KSTR) by the adaptive controller, that is, Time or period of the target value corresponding to the detected value Between It means time.
[0029]
In this embodiment, since the control cycle is synchronized with the crank angle of the internal combustion engine, the dead time d ′ is specifically expressed by the number of TDC cycles based on a predetermined period represented by the crank angle. is doing. Of course, when the control cycle is determined in synchronization with the timer, the dead time d ′ is a value counted by the timer. In Become. In any case, the dead time d ′ may be expressed using any of the TDC number, the ignition number, the absolute time, the crank angle, and the like.
[0030]
For convenience of understanding, this calculation work is performed after the feedback correction coefficient calculation is described.
[0031]
Continuing with the description of the flow chart of FIG. 3, the program then proceeds to S22 to read the LAF sensor detection value (sensor output), and proceeds to S24 to detect the detected air-fuel ratio KACT (k) (k: sampling time of the discrete system). Then, the process proceeds to S26 to calculate the feedback correction coefficient KFB.
[0032]
FIG. 5 is a subroutine flow chart showing the work.
[0033]
In the following, it is determined in S100 whether or not it is a feedback control region. This is performed in a separate routine (not shown), and is controlled in an open loop, for example, when the amount is fully increased or when the engine speed is high, or when the exhaust gas recirculation mechanism operates and the operating state changes suddenly.
[0034]
When the result in S100 is affirmative, the routine proceeds to S102, where it is determined whether or not the previous time, that is, the previous activation (previous control cycle) of the program shown in the flowchart of FIG. Then, the feedback correction coefficient KSTR based on the adaptive control law (hereinafter, this correction coefficient is referred to as “adaptive correction coefficient”) is calculated.
[0035]
This will be described below. The adaptive controller shown in FIG. 4 is based on the adaptive control technique previously proposed by the present applicant. It consists of an adaptive controller comprising an STR (self-tuning regulator) controller and an adaptive (control) parameter adjustment mechanism for adjusting the adaptation (control) parameter (vector). The STR controller is a target of a feedback system for fuel injection amount control. A value and a controlled variable (plant output) are input, a coefficient vector identified by the adaptive parameter adjustment mechanism is received, and an output is calculated.
[0036]
In such adaptive control, one of the adjustment rules (mechanisms) of adaptive control is I.I. D. There is a parameter adjustment rule proposed by Landau et al. This method transforms the adaptive control system into an equivalent feedback system consisting of linear and nonlinear blocks, and for the nonlinear blocks, Popov's integral inequality for input and output is established, and the linear block is adjusted to be strongly positive and real. It is a technique that guarantees the stability of the adaptive control system by determining the law. In other words, in the parameter adjustment law proposed by Landau et al., The adjustment law (adaptive law) expressed in a recursive form is stabilized by using at least one of Popov's superstability theory or Lyapunov's direct method. Guarantees sex.
[0037]
This method is described in, for example, “Compute Roll” (Corona Publishing Co., Ltd.) No. 27, 28-41, or "Automatic Control Handbook" (Ohm) 703-707, "A Survey of Model Reference Adaptive Techniques-Theory and Ap-plications" ID LANDAU "Automatica" Vol. 10, pp 353-379, 1974, "Unification of Discrete Time Explicit Model Reference Adaptive ControlDesigns" IDLANDAU et al. "Automatica" Vol. 17, No. 4, pp. 593-611, 1981, and "Combining Model Reference Adaptive Controllers and Stochastic Self-tuning Regulators "ID LANDAU" Automatica "Vol. 18, No. 1, pp. 77-84, 1982, is known in the art.
[0038]
In the adaptive control technique of the illustrated example, this Landau et al. Adjustment rule is used. As will be described below, Landau et al.'S adjustment law uses a transfer function B (Z ^-1 ) / A (Z ^-1 The adaptive parameter θ hat (k) identified by the parameter adjustment mechanism is expressed by a vector (transposed vector) as shown in Equation 3 when the polynomial in the denominator numerator of Further, the input ζ (k) to the parameter adjusting mechanism is determined as shown in Equation 4. Here, a case where m = 1, n = 1, d = 3, that is, a plant having a dead time corresponding to three control cycles in the primary system is taken as an example.
[0039]
[Expression 1]

[0040]
[Expression 2]

[0041]
[Equation 3]

[0042]
[Expression 4]

[0043]
Here, the adaptive parameter θ hat shown in Equation 3 is a scalar quantity b 0 hat that determines the gain. ^-1 (k), a control element BR hat (Z ^-1 , k) and the control element S hat (Z ^-1 , k), which are expressed as Equations 5 to 7, respectively.
[0044]
[Equation 5]

[0045]
[Formula 6]

[0046]
[Expression 7]

[0047]
The parameter adjustment mechanism identifies and estimates the scalar quantities and the coefficients of the control elements, and sends them to the STR controller as the adaptive parameter θ hat shown in Equation 3 above. The parameter adjustment mechanism uses the plant manipulated variable u (i) and the controlled variable y (j) (i and j include past values) so that the deviation between the target value and the controlled variable becomes zero. Calculate the hat. Specifically, the adaptive parameter θ hat is calculated as shown in Equation 8. In Equation 8, Γ (k) is a gain matrix (m + n + d order) that determines the identification / estimation speed of the adaptive parameter, and e asterisk (k) is a signal indicating the identification / estimation error. It is expressed by a recurrence formula. In Equation 10, D (z ^-1 ) Is a desired asymptotically stable polynomial given by the designer, and is set to 1 in this example.
[0048]
[Equation 8]

[0049]
[Equation 9]

[0050]
[Expression 10]

[0051]
Various specific algorithms are given depending on how to select λ1 (k) and λ2 (k) in equation (9). For example, if λ1 (k) = 1, λ2 (k) = λ (0 <λ <2), then the gradual gain algorithm (least square method when λ = 1), λ1 (k) = λ1 (0 <λ1) <1), λ2 (k) = λ2 (0 <λ2 <λ), variable gain algorithm (weighted least square method when λ2 = 1), λ1 (k) / λ2 (k) = σ , Λ3 is expressed as Equation 11, a fixed trace algorithm is obtained by setting λ1 (k) = λ3 (k). When λ1 (k) = 1 and λ2 (k) = 0, the fixed gain algorithm is used. In this case, as apparent from Equation 9, Γ (k) = Γ (k−1), and therefore, Γ (k) = Γ is a fixed value. For time-varying plants such as fuel injection or air-fuel ratio, any of a gradual gain algorithm, a variable gain algorithm, a fixed gain algorithm, and a fixed trace algorithm are suitable. In Equation 11, trΓ (0) is a trace of the initial value of Γ.
[0052]
## EQU11 ##

[0053]
Here, in FIG. 4, the STR controller (adaptive controller) and the adaptive parameter adjustment mechanism are outside the fuel injection amount calculation system, and the detected air-fuel ratio KACT (k) is the target air-fuel ratio KCMD ( k-d ') (where d' indicates the dead time until KCMD is reflected in KACT, which means the target air-fuel ratio before the dead time control period, as mentioned earlier) The feedback correction coefficient KSTR (k) is calculated by operating so as to match. That is, the STR controller receives the coefficient vector θ hat (k) adaptively identified by the adaptive parameter adjustment mechanism, and forms a feedback compensator so as to match the target air-fuel ratio KCMD (k−d ′). The calculated feedback correction coefficient KSTR (k) is multiplied by the basic injection amount Tim together with various correction terms, and the corrected fuel injection amount is supplied to the control plant (internal combustion engine) as the output fuel injection amount Tout (k).
[0054]
In this way, the adaptive correction coefficient KSTR (k) and the detected air-fuel ratio KACT (k) are obtained and input to the adaptive parameter adjustment mechanism, where the adaptive parameter θ hat (k) is calculated and input to the STR controller. The STR controller is given a target air-fuel ratio KCMD (k) as an input, and an adaptive correction coefficient KSTR using a recurrence formula so that the detected air-fuel ratio KACT (k) matches the target air-fuel ratio KCMD (k−d ′). Calculate (k).
[0055]
Specifically, the adaptive correction coefficient KSTR (k) is obtained as shown in Equation 12.
[0056]
[Expression 12]

[0057]
Returning to the flowchart of FIG. 5, the process then proceeds to S106, and the adaptive correction coefficient KSTR thus obtained is set as the feedback correction coefficient KFB.
[0058]
On the other hand, when it is determined in S100 that it is not the feedback control region, the process proceeds to S108, the adaptive correction coefficient KSTR is set to 1.0, and the process proceeds to S106. Since the feedback correction coefficient is multiplied by the supplied fuel amount to correct it, setting it to 1.0 means that feedback control is not performed.
[0059]
If it is determined in S102 that the previous feedback control region is not reached, it means that the feedback control region has been entered from the open loop control region, so that the process proceeds to S110 and the adaptive correction coefficient KSTR is adapted to be 1 or in the vicinity thereof. Set internal variables for control laws including past values.
[0060]
To explain this, the adaptive parameter adjustment mechanism described above has ζ (kd), that is, plant input u (k) (= KSTR (k)) and plant output y (k) (= KACT (k)). The vector which puts together the present value and the past value is inputted, and the adaptive parameter θ hat (k) is calculated from the causal relationship. U (k) used here is a correction coefficient used for correcting the amount of supplied fuel, as described above.
[0061]
Thus, when starting adaptive control outside the feedback control region, that is, outside the adaptive control region, the past of internal variables such as ζ (kd), θ hat (k-1), gain matrix Γ (k-1), etc. If there is no value, the correct adaptive correction coefficient KSTR cannot be calculated, or in the worst case, oscillation may occur.
[0062]
Therefore, when u (ki) = 1 (i ≧ 1), the adaptive parameter θ hat (k) is set so that the adaptive correction coefficient KSTR is 1 or in the vicinity thereof, and ζ (kd) is expressed by the following equation (13). Set as follows. Since the gain matrix Γ (k−1) is a value that determines the adaptive speed, it is set to a predetermined matrix value such as an initial value.
[0063]
[Formula 13]

[0064]
More specifically, since the adaptive correction coefficient KSTR is calculated as shown in Equation 12, let us consider θ hat (k−1) and ζ (kd) such that the adaptive correction coefficient KSTR is 1 or in the vicinity thereof.
[0065]
For example, when the target air-fuel ratio KCMD (kd ') is 1, KSTR (k-1) = KSTR (k-2) = KSTR (k-3) = 1.0 and the adaptive parameter θ hat (k) is controlled. The initial value of an element such as an element
r1 = 0.1
r2 = 0.05
r3 = 0.05
so = 0.3
bo = 0.5
Then, when the detected air-fuel ratio KACT (k) is 1, the adaptive correction coefficient KSTR is
KSTR = (1-0.1 × 1-0.05 × 1-0.05 × 1-0.3 × KACT (k)) / 0.5
Thus, when the detected air-fuel ratio KACT (k) ≈1, the adaptive correction coefficient KSTR≈1.
[0066]
This is because the adaptive correction coefficient KSTR (ki) (i.gtoreq.1) is 1 or in the vicinity thereof, that is, in the state where almost no feedback correction is performed, the target far past the detected air-fuel ratio KACT (kj) (j.gtoreq.1). This corresponds to artificially creating a past state that has been stably controlled in accordance with the air-fuel ratio KCMD (kd ′).
[0067]
As a result, the feedback control is started from the same value, the control amount is not hunted, the air-fuel ratio spike is not generated, and the stability of the control is improved. Note that the initial value of the element of the adaptive parameter θ hat may be changed according to the target air-fuel ratio.
[0068]
Returning to the flow chart of FIG. 3, the program then proceeds to S28, and the basic fuel injection amount (supplied fuel amount) Tim is added to the target air-fuel ratio correction coefficient KCMDM (target air-fuel ratio KCMD (equivalent ratio) to the intake air charging efficiency correction). The value is obtained by multiplying the feedback correction coefficient KFB and the various correction coefficients KTOTAL, and adding the addition term TTOTAL to correct it to determine the output fuel injection amount Tout as described above. Next, the routine proceeds to S30, where the output fuel injection amount Tout is output to the injector 22 as the operation amount.
[0069]
Here, the various correction coefficients KTOTAL means the integrated value of various correction coefficients performed by multiplication such as water temperature correction, and the addition term TTOTAL indicates the total value of correction coefficients performed by additional values such as atmospheric pressure correction (however, the invalid time of the injector) Etc. are not included because they are added separately when the output fuel injection amount Tout is output).
[0070]
When the result in S18 is negative, the air-fuel ratio becomes open loop control, so the routine proceeds to S32, the value of the feedback correction coefficient KFB is set to 1.0, and the routine proceeds to S28 to determine the output fuel injection amount Tout. If it is determined that cranking is determined in S12, the process proceeds to S34 to search for the fuel injection amount Ticr at the time of cranking, and the process proceeds to S36 to calculate the output fuel injection amount Tout according to the equation of the start mode based on the search value. If it is determined in S14 that the fuel cut has occurred, the routine proceeds to S38, where the output fuel injection amount Tout is set to zero.
[0071]
Here, the calculation of the dead time d ′ in S20 will be described.
[0072]
FIG. 6 is a subroutine flow chart showing the calculation work. Prior to the description of FIG. 6, the dead time will be specifically described with reference to FIG.
[0073]
The figure shows the target value KCMD (kd ') of the adaptive controller that accurately reflects the dead time d' from the target air-fuel ratio KCMD to the detected air-fuel ratio KACT, that is, the target value used in the calculation of the adaptive correction coefficient KSTR ( 13 is a timing chart showing the behavior of the detected air-fuel ratio KACT when using the equation (12). In this case, KACT follows d ′ behind KCMD. As a result, the desired controllability can be realized. Therefore, in this embodiment, first, the dead time d ′ is changed according to the target value.
[0074]
Next, a case where the dead time d ′ is intentionally changed to improve drivability will be described. If the dead time changed intentionally is d ″,
d '<d "
And set. This is shown in FIG.
[0075]
As shown in the figure, since the dead time is intentionally made different from the proper appropriate value d ′, the responsiveness is deteriorated. This is because the adaptive controller reflects the change in the target value later than the actual dead time. Therefore, the detected value becomes a smoothed value, and when the target air-fuel ratio is significantly changed in a lean burn engine or the like, the response of the adaptive controller is intentionally lowered in this way, so that the torque shock is rather reduced. And drivability is improved.
[0076]
The flow chart of FIG. 6 will be described on the premise of the above. First, in step S200, the target air-fuel ratio KCMD (kd ') used in the calculation of the adaptive correction coefficient KSTR shown in Equation 12 according to the target value KCMD (k) is described. A dead time d ′ is set. That is, the time corresponding to the detected air-fuel ratio, more specifically, the target value before the time (k−d ′) is detected as the value of the current time (k), and both are made to correspond. Thereby, the controllability originally intended can be given.
[0077]
Next, the routine proceeds to S202, where the difference DKCMD between the current value KCMD (k) of the target air-fuel ratio and the previous value KCMD (k-1), that is, whether the target air-fuel ratio has changed to the rich side or the lean side has been determined. Then, the process proceeds to S204, where it is determined whether or not the difference DKCMD obtained exceeds the reference value DKCMDREF. Here, it is determined whether the target air-fuel ratio has changed in the rich direction by appropriately setting the reference value DKCMDREF.
[0078]
When the result in S204 is affirmative, the program proceeds to S206, in which a positive value a is added to the appropriate dead time d ′, and the program proceeds to S208, where the value of the counter C is incremented. Then, as long as the affirmative determination is made in S204 at the next program start (control cycle), the process proceeds to S206 and S208 to continue incrementing the counter value. If it is determined in S210 that the counter value exceeds the predetermined value CREF, the process proceeds to S212. The value of the counter C is reset to zero. At this time, as apparent from the above, the adaptive correction coefficient KSTR is calculated with the dead time d ″, so that the behavior of KACT is as shown in FIG. 8 over a period corresponding to the counter value CREF. Become.
[0079]
In this embodiment, as described above, first, in S200, the dead time d ′ of the target air-fuel ratio KCMD (kd ′) used in the calculation of the adaptive correction coefficient KSTR is appropriately set according to the target value KCMD (k). Therefore, an intended detection value can be obtained according to the responsiveness of the LAF sensor, and the controllability that is originally planned can be obtained. Therefore, only S200 is required to achieve the object, and S202 and subsequent steps are unnecessary.
[0080]
Furthermore, since the appropriate dead time just described has been intentionally increased so that the behavior of KACT is improved, the engine output torque is reduced when the air-fuel ratio changes from the lean side to the rich direction in a lean burn engine. Smoothing can reduce shock and improve drivability.
[0081]
FIG. 9 is a partial flow chart of FIG. 6 showing a second embodiment of the present invention.
[0082]
In the second embodiment, the dead time is reduced by subtracting the positive value b from the appropriate value d ′ in S206a corresponding to S206 in the flowchart of FIG. FIG. 10 shows the behavior of KACT at that time. As shown, KACT overshoots in reverse.
[0083]
Therefore, for example, when performing fuel intake pipe adhesion correction, an adhesion correction value is set in advance as a map value at room temperature with respect to the engine speed and intake pressure Pb, and when searching from the detected engine speed, the map When substituting for even at low water temperatures
d '> d "
Thus, as shown in FIG. 10, it is possible to compensate for the lack of adhesion correction by intentionally over-correcting.
[0084]
The above is the first embodiment
d '<d "
Therefore, by arbitrarily selecting the characteristics of the first or second embodiment, it is possible to operate so as to arbitrarily cancel the air-fuel ratio spike. It also means that it becomes possible.
[0085]
In addition, as described at the beginning of the first embodiment, it is possible to obtain the desired KACT behavior by inherently providing an appropriate dead time d ′. According to the state ". Although detailed description is omitted here, it is necessary to adjust the dead time accordingly when the volume of the exhaust manifold 24 is made variable or when the characteristics of the variable valve timing mechanism 300 are changed. In this case, the above can be used.
[0086]
In the first and second embodiments, only the adaptive correction coefficient using the adaptive control law is used as the feedback correction coefficient. In addition, a low-response PID correction coefficient using the PID control law is prepared, and the feedback is performed. You may make it switch suitably in a control area.
[0087]
In the first and second embodiments, the target value is the air-fuel ratio, but the fuel injection amount itself may be the target value.
[0088]
In the first and second embodiments, the feedback correction coefficient KSTR is obtained as a multiplication coefficient (term), but it may be an addition term.
[0089]
In the first and second embodiments, the throttle valve 16 is operated by a pulse motor. However, the throttle valve 16 may be mechanically linked with an accelerator pedal and operated according to the movement of the accelerator pedal.
[0090]
In the first and second embodiments, STR is described as an example of the adaptive controller, but MRACS (model reference adaptive control) may be used.
[0091]
【The invention's effect】
According to the first aspect, the controllability can be improved, and conversely, the drivability can be improved by intentionally changing the controllability.
[0092]
Also Even if the target air-fuel ratio changes particularly greatly, a predetermined value appropriate for the fluctuation of the air-fuel ratio is obtained. Time The controllability can be improved by giving a gap, and in the transient state, Time By intentionally changing the interval, drivability can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall fuel injection control device for an internal combustion engine according to the present invention.
FIG. 2 is a block diagram showing in detail the configuration of a control unit of the apparatus of FIG.
3 is a flowchart showing the operation of the apparatus of FIG.
4 is a block diagram functionally showing the operation of the apparatus of FIG.
FIG. 5 is a subroutine flow chart showing a calculation operation of a feedback correction coefficient KFB in the flow chart of FIG. 3;
6 is a subroutine flow chart showing a calculation operation of dead time in the flow chart of FIG.
FIG. 7 is a timing chart illustrating the behavior of the detected value with respect to the target value, explaining the calculation work of the flow chart of FIG. 6;
8 is a timing chart for explaining the calculation work of the flow chart of FIG. 6 and showing the behavior of the detected value with respect to the target value similar to FIG.
FIG. 9 is a partial view of the flow chart of FIG. 6 showing a second embodiment of the present invention.
FIG. 10 is a timing chart for explaining the calculation work of the flowchart of FIG. 9 and showing the behavior of the detected value with respect to the target value similar to FIG.
[Explanation of symbols]
10 Internal combustion engine
22 Injector
34 Control unit
54 Wide-area air-fuel ratio sensor (LAF sensor)

Claims (1)

a. An operating state detecting means for detecting an operating state including an exhaust air-fuel ratio exhausted from the internal combustion engine;
b. A fuel supply amount determining means for determining a fuel supply amount of the internal combustion engine;
And c. Feedback correction coefficient calculation means for calculating a feedback correction coefficient using an adaptive controller so that the detected exhaust air-fuel ratio matches the target air-fuel ratio before a predetermined time corresponding to a dead time with the supplied fuel amount as an operation amount When,
In the fuel injection control device for an internal combustion engine, comprising: determining whether the target air-fuel ratio has been changed, and deliberately increasing or decreasing the predetermined time from an appropriate value when it is determined that the target air-fuel ratio has been changed. A fuel injection control device for an internal combustion engine.

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