JPH07112826B2 - Rear-wheel steering control method for four-wheel steering vehicle - Google Patents
Rear-wheel steering control method for four-wheel steering vehicleInfo
- Publication number
- JPH07112826B2 JPH07112826B2 JP59087094A JP8709484A JPH07112826B2 JP H07112826 B2 JPH07112826 B2 JP H07112826B2 JP 59087094 A JP59087094 A JP 59087094A JP 8709484 A JP8709484 A JP 8709484A JP H07112826 B2 JPH07112826 B2 JP H07112826B2
- Authority
- JP
- Japan
- Prior art keywords
- steering
- vehicle
- wheel
- coefficient
- wheel steering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D7/00—Steering linkage; Stub axles or their mountings
- B62D7/06—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins
- B62D7/14—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、ハンドルの回動による前輪の操舵に連動して
後輪をも操舵するようにした四輪操舵車の後輪操舵制御
方法に関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering control method for a four-wheel steering vehicle in which the rear wheels are also steered in conjunction with the steering of the front wheels by the turning of the steering wheel. .
従来から、車両の操安性を向上させる方法として、ハン
ドルの回動操作に対するヨーレートの応答の位相ずれを
低減することが提案されており、特開昭57−15066号公
報には、これを、ハンドルの回動操作による前輪の操舵
に連動して後輪を操舵することにより実現しようとする
四輪操舵車の後輪操舵制御方法が示されている。ここで
は、後輪を前輪操舵角速度に比例して操舵することによ
り、ハンドルの回動操作に対するヨーレートの応答の位
相ずれをヨー運動に関係した車両の固有振動数ωｎ付近
にてゼロにしているが、同固有振動数ωｎをはずれた周
波数においては前記位相ずれをゼロにできないという問
題、すなわち前記位相ずれをなくすことができないとい
う問題を持っている。特に、この位相ずれは、中高速走
行時においてハンドルの回動操作による車両の旋回に対
して操安性を悪化させる。Conventionally, as a method of improving the steerability of a vehicle, it has been proposed to reduce the phase shift of the response of the yaw rate to the turning operation of the steering wheel, which is disclosed in JP-A-57-15066. A rear-wheel steering control method for a four-wheel steering vehicle that is intended to be realized by steering the rear wheels in conjunction with the steering of the front wheels by the turning operation of the steering wheel is shown. Here, by steering the rear wheels in proportion to the front wheel steering angular velocity, the phase shift of the response of the yaw rate to the turning operation of the steering wheel is made zero near the natural frequency ωn of the vehicle related to the yaw motion. However, there is a problem that the phase shift cannot be zero at a frequency deviating from the same natural frequency ωn, that is, the phase shift cannot be eliminated. In particular, this phase shift deteriorates the steering stability with respect to the turning of the vehicle by the turning operation of the steering wheel during traveling at medium and high speeds.
本発明は、かかる問題に着目してなされたもので、その
目的は、中高速走行中の車両のハンドルの回動操作に対
するヨーレートの応答の位相ずれを前記固有振動数ωｎ
付近だけではなく、全周波数領域にわたってゼロにし得
てすなわち全周波数領域にわたってなくすことができる
ようにして、車両の操安性をより一層向上させることの
できる四輪操舵車の後輪操舵制御方法を提供することに
ある。The present invention has been made in view of such a problem, and an object thereof is to determine the phase shift of the response of the yaw rate to the turning operation of the steering wheel of the vehicle during traveling at middle and high speeds by the natural frequency ωn.
A rear-wheel steering control method for a four-wheel steering vehicle that can further improve the maneuverability of the vehicle by enabling it to be zero not only in the vicinity but also over the entire frequency range, that is, can be eliminated over the entire frequency range. To provide.
上記目的を達成するために、本発明の構成上の特徴は、
前輪操舵角速度ｆに係数ａを乗算した第１制御項ａ・
ｆと、前輪操舵角βｆに係数ｋを乗算した第２制御項
ｋ・βｆとの和である制御舵角ａ・ｆ＋ｋ・βｆに後
輪を操舵する車両の中高速走行時における後輪操舵制御
方法において、前記第１制御項ａ・ｆが後輪を前輪の
操舵方向とは逆方向に操舵する項として作用するように
前記係数ａの値を設定するとともに同係数ａの絶対値が
車速の増加にしたがって減少するように同係数ａの値を
設定し、かつ第２制御項ｋ・βｆが後輪を前輪の操舵方
向と同方向に操舵する項として作用するように前記係数
ｋの値を設定するとともに同係数ｋの絶対値が車速の増
加にしたがって増加するように同係数ｋの値を設定し
て、ハンドルの回動操作に対するヨーレートの応答の位
相ずれを車速とは無関係に全周波数領域にわたってなく
すようにしたことにある。In order to achieve the above object, the structural features of the present invention are
A first control term a · that is obtained by multiplying the front wheel steering angular velocity f by a coefficient a.
f and the rear wheel steering control during medium-high speed traveling of the vehicle in which the rear wheels are steered to the control steering angle a.f + k.βf, which is the sum of the second control term k · βf obtained by multiplying the front wheel steering angle βf by the coefficient k. In the method, the value of the coefficient a is set so that the first control term a · f acts as a term for steering the rear wheels in the direction opposite to the steering direction of the front wheels, and the absolute value of the coefficient a is the vehicle speed. The value of the coefficient a is set so as to decrease with an increase, and the value of the coefficient k is set so that the second control term k · βf acts as a term for steering the rear wheels in the same direction as the steering direction of the front wheels. The value of the coefficient k is set so that the absolute value of the coefficient k increases as the vehicle speed increases, and the phase shift of the yaw rate response to the turning operation of the steering wheel is set regardless of the vehicle speed. I tried to get rid of it.
上記のように構成した本発明においては、後輪を制御舵
角ａ・ｆ＋ｋ・βｆに制御するとともに、係数a,kの
値を上記のように設定して、ハンドルの回動操作に対す
るヨーレートの応答の位相ずれを車速とは無関係に全周
波数領域にわたってなくすようにしたので、車両の中高
速走行中においては車速が変化しても、あらゆる周波数
成分を有するハンドルの回動操作に対してヨーレートの
応答の位相ずれがなくなる。その結果、車両の中高速走
行中においては、ハンドルを急に回動したり、同ハンド
ルをゆっくり回動したり、車速が変化しても、車両に発
生するヨーレートをハンドルの回動操作に対して時間遅
れなく対応させることができるので、車両の操安性を大
幅に向上させることができる。In the present invention configured as described above, the rear wheels are controlled to the control steering angle a · f + k · βf, and the values of the coefficients a and k are set as described above, so that the yaw rate for the turning operation of the steering wheel is changed. Since the phase shift of the response is eliminated over the entire frequency range regardless of the vehicle speed, even if the vehicle speed changes during medium to high speed running, the yaw rate of the yaw rate can be changed when the steering wheel has any frequency component. There is no phase shift in the response. As a result, when the vehicle is running at medium to high speeds, the yaw rate generated in the vehicle is changed by the turning operation of the steering wheel even if the steering wheel is suddenly turned, the steering wheel is slowly turned, or the vehicle speed changes. Since it is possible to deal with the problem without delay, the maneuverability of the vehicle can be greatly improved.
このことを、ハンドルの回動操作により車両が直進状態
から定常円旋回状態に移行する場合を例にして説明して
おく。まず、ハンドルの回動操作の初期においては、第
２制御項ｋ・βｆが小さく前輪が操舵されていく過程に
おいて、後輪は第１制御項ａ・ｆに支配されて前輪の
操舵方向とは逆方向に操舵される。この後輪の操舵は、
車両のヨー運動をハンドルの回動方向に促進して車両に
発生するヨーレートの位相遅れをなくすので、車両の回
頭性（操縦性）が良好になる。一方、ハンドルの回動操
作から多少の時間が経過して前輪操舵角βｆが増加し始
めると、第２制御項ｋ・βｆが作用し始め、この第２制
御項ｋ・βｆは後輪を前輪の操舵方向と同方向に操舵し
て、ハンドルの回動操作に対して車両に発生するヨーモ
ーメントを抑制するように作用するので、安定した車両
挙動が得られる。さらに時間が経過して、ハンドルの回
動角が目標値に近づくとハンドルの回動速度は減少し、
車両のヨー運動をハンドルの回動方向に促進する第１制
御項ａ・ｆが減少してゼロになる。これにより、車両
の回頭のし過ぎが抑止され、ハンドルの保持と同時に、
車両を定常円旋回状態に移行できる。この定常円旋回状
態への移行後には、第２制御項ｋ・βｆが後輪を前輪の
操舵方向と同方向に前輪操舵角βｆに比例した舵角に保
持するので、車両はハンドルの操舵に対して低い感度で
ヨーレートを発生しながら旋回し続け、車両の走行安定
性が良好になる。そして、これらの一連の現象は、係数
a,kを車速に応じて変化させることにより車速が変化し
ても維持されるので、本発明によれば、中高速走行時に
おける車両の回頭性及び走行安定性が常に良好になる。This will be described by taking as an example a case where the vehicle shifts from a straight traveling state to a steady circular turning state by rotating the steering wheel. First, in the initial stage of the turning operation of the steering wheel, in the process in which the second control term k · βf is small and the front wheels are being steered, the rear wheels are dominated by the first control terms a · f and the steering direction of the front wheels is Steered in the opposite direction. This rear wheel steering is
Since the yaw motion of the vehicle is promoted in the turning direction of the steering wheel to eliminate the phase delay of the yaw rate generated in the vehicle, the turning performance (controllability) of the vehicle is improved. On the other hand, when the front wheel steering angle βf starts to increase after some time has passed from the turning operation of the steering wheel, the second control term k · βf starts to act, and the second control term k · βf causes the rear wheel to move forward. Since the steering is performed in the same direction as the steering direction to suppress the yaw moment generated in the vehicle in response to the turning operation of the steering wheel, stable vehicle behavior can be obtained. When the turning angle of the handle approaches the target value after a further time elapses, the turning speed of the handle decreases,
The first control terms a and f that promote the yaw motion of the vehicle in the turning direction of the steering wheel decrease to zero. This prevents excessive turning of the vehicle, and at the same time as holding the steering wheel,
The vehicle can be shifted to a steady circle turning state. After the transition to the steady circular turning state, the second control term k · βf keeps the rear wheels in the same steering direction as the front wheels at a steering angle proportional to the front wheel steering angle βf, so that the vehicle steers the steering wheel. On the other hand, the yaw rate is generated at a low sensitivity and the vehicle keeps turning while the traveling stability of the vehicle is improved. And these series of phenomena are
Since a and k are changed according to the vehicle speed to be maintained even if the vehicle speed changes, according to the present invention, the turning performance and traveling stability of the vehicle during medium-high speed traveling are always improved.
以下に本発明を図面に基づいて説明する。第１図は四輪
操舵車の操舵系を概略的に示した図であり、同操舵系に
おいては、ハンドル１を回動操作することにより、シャ
フト２、ピニオン３、ラックバー４、前輪ナックル５を
介して前輪タイヤ６が従来車と同様に操舵される。シャ
フト２には前輪操舵角βｆおよび前輪操舵角速度ｆを
検出するセンサ７が取付けられていて、同センサ７から
の信号は車速ｕを検出するセンサ８からの信号と共に後
輪舵角演算器９に入力される。演算器９では前輪操舵角
βｆ、前輪操舵角速度ｆおよび車速ｕに基づいて後輪
操舵角βｒが算出され、これが差動増幅器10に出力され
る。差動増幅器10は、後輪舵角検出器11で検出される後
輪実操舵角βroに対応する電圧と後輪演算操舵角βｒに
対応する電圧との差（βｒ−βro）を増幅器12に出力
し、増幅された（βｒ−βro）を制御信号として電気油
圧サーボ弁13を制御する。サーボ弁13はエンジン等によ
って駆動される油圧ポンプ14で発生する油圧のオイルシ
リンダ15への給排を制御し、後輪ナックル16を介して後
輪タイヤ17の操舵角を制御する。上記のごとく、後輪実
操舵角βroは、前輪操舵角βｆ、前輪操舵角速度ｆ及
び車速ｕに対応してフィードバック制御され、後述のご
とく、ハンドルの回動操作に対するヨーレートの応答の
位相ずれを生ずることなく車両を旋回運動させることが
可能となる。The present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a steering system of a four-wheel steering vehicle. In the steering system, a shaft 1, a pinion 3, a rack bar 4, a front knuckle 5 are operated by rotating a steering wheel 1. The front wheel tires 6 are steered via the same as in the conventional vehicle. A sensor 7 for detecting a front wheel steering angle βf and a front wheel steering angular velocity f is attached to the shaft 2, and a signal from the sensor 7 is sent to a rear wheel steering angle calculator 9 together with a signal from a sensor 8 for detecting a vehicle speed u. Is entered. The computing unit 9 calculates the rear wheel steering angle βr based on the front wheel steering angle βf, the front wheel steering angular velocity f and the vehicle speed u, and outputs this to the differential amplifier 10. The differential amplifier 10 supplies to the amplifier 12 the difference (βr−βro) between the voltage corresponding to the rear wheel actual steering angle βro detected by the rear wheel steering angle detector 11 and the voltage corresponding to the rear wheel calculated steering angle βr. The electro-hydraulic servo valve 13 is controlled by using the output and amplified (βr-βro) as a control signal. The servo valve 13 controls supply / discharge of hydraulic pressure generated by a hydraulic pump 14 driven by an engine or the like to / from an oil cylinder 15, and controls a steering angle of a rear wheel tire 17 via a rear wheel knuckle 16. As described above, the rear wheel actual steering angle βro is feedback-controlled in accordance with the front wheel steering angle βf, the front wheel steering angular velocity f and the vehicle speed u, and as described later, a phase shift of the yaw rate response to the turning operation of the steering wheel occurs. It is possible to make a turning motion of the vehicle without it.
しかして、ハンドル操作角に対する車両のヨーレートの
応答はよく知られている様に、伝達関数の形式で、次の
様に書ける。Then, as is well known, the response of the yaw rate of the vehicle to the steering angle can be written in the form of a transfer function as follows.
（α0,β，ζn,ωｎは車両により決まる定数、Ｓはラプ
ラス演算子） 上式（１）は分子に１次進め系、分母に２次遅れ系を有
しているため、全体としては１次遅れ系に相当する形と
なっており、高周波数領域での位相遅れが生じてしま
う。 (Α 0 , β, ζ n, ω n are constants determined by the vehicle, S is the Laplace operator) The above equation (1) has a first-order advance system in the numerator and a second-order lag system in the denominator, so overall Since it has a form corresponding to a first-order delay system, a phase delay occurs in a high frequency region.
従って、伝達関数▲Ｇｒ βｆ▼（ｓ）の分子を２次進め
系 S2＋２ζｒωrS＋ωr2 …（２） となる様に工夫し、しかも、 ζｒ＝ζｎ …（３） ωr2＝ωn2 …（４） の２つの条件を満足させることができれば、伝達関数▲
Ｇｒ βf1▼（ｓ）を下式（５）のように単なる比例要素
とすることができ、前記位相ずれを完全にゼロとするこ
とが可能となる。Therefore, the numerator of the transfer function ▲ G r βf ▼ (s) is devised so as to be the second-order advancing system S 2 + 2ζrωrS + ωr 2 (2), and ζr = ζn (3) ωr 2 = ωn 2 ((3)) If the two conditions of 4) can be satisfied, the transfer function ▲
G r βf 1 ▼ (s) can be a mere proportional element as shown in the following expression (5), and the phase shift can be made completely zero.
（α1,ζr,ωｒは車両により決まる定数） 本発明では、上記を実現させるために、第１図の演算器
９において下式（６）の演算を行わせるものである。 (Α 1 , ζr, ωr are constants determined by the vehicle) In the present invention, in order to realize the above, the computing unit 9 of FIG. 1 performs the computation of the following equation (6).
βｒ＝ａ・ｆ＋ｋ・βｆ …（６） 上式（６）の係数a,kに必要とされる条件を以下に説明
する。βr = a · f + k · βf (6) The conditions required for the coefficients a, k in the above equation (6) will be described below.
車両におけるロールの影響を無視した第４図の車両モデ
ルにおいて、車速をｕ、車両横速度をｖ、ヨーレートを
ｒ、前輪操舵角をβｆ、後輪操舵角をβｒ、ホイールベ
ースをＬ、前輪と車両重心との距離をLf、後輪と車両重
心との距離をLrで表し、かつ前輪タイヤの一輪当りのコ
ーナリングパワをCf、後輪タイヤの一輪当りのコーナリ
ングパワをCr、車両重心まわりの慣性モーメントをIz、
車両質量をＭとして、横方向及びヨーイング方向の運動
方程式をラプラス変換しマトリックスの形で表すと下式
（７）のようになる。In the vehicle model of FIG. 4 ignoring the effect of roll on the vehicle, the vehicle speed is u, the vehicle lateral speed is v, the yaw rate is r, the front wheel steering angle is βf, the rear wheel steering angle is βr, the wheel base is L, and the front wheel is The distance from the vehicle center of gravity is represented by Lf, the distance between the rear wheel and the vehicle center of gravity is represented by Lr, and the cornering power per front wheel tire is Cf, the cornering power per rear wheel tire is Cr, and the inertia around the vehicle center of gravity is The moment Iz,
When the vehicle mass is M and the equations of motion in the lateral direction and the yawing direction are Laplace transformed and expressed in the form of a matrix, the following equation (7) is obtained.
上式（７）の（Ｖ（ｓ）,R（ｓ））Ｔの係数行列を とおいて、（Ｖ（ｓ）,R（ｓ））Ｔについて解くと となる。 The coefficient matrix of (V (s), R (s)) T in the above equation (7) is If we solve for (V (s), R (s)) T Becomes
従って、車両の横速度ｖ、ヨーレートｒの前輪操舵角β
ｆに対する伝達関数は、 となる。ここで、ヨーレートｒの伝達関数▲Ｇｒ βｆ▼
（ｓ）を具体的に示すと、 ただし α１＝−2aCrLrM/（MIz） となり、伝達関数の分母、分子ともにＳの２次式で構成
できる。ここで、上式（３），（４）の条件を当てはめ
ると、係数a,kに関する連立方程式が求まり、これを解
くと、ハンドルの回動操作に対するヨーレートの応答の
位相ずれを完全にゼロとする係数a,kを求めることがで
きる。各係数a,kを具体的に解くと、下式（９），（1
0）のようになる。Therefore, the front wheel steering angle β for the vehicle lateral speed v and yaw rate r
The transfer function for f is Becomes Here, the transfer function of the yaw rate r ▲ G r βf ▼
Specifically showing (s), However, α 1 = −2aCrLrM / (MIz) Therefore, both the denominator and the numerator of the transfer function can be constructed by a quadratic expression of S. Here, by applying the conditions of the above equations (3) and (4), simultaneous equations regarding the coefficients a and k are obtained, and by solving them, the phase shift of the response of the yaw rate to the turning operation of the steering wheel becomes completely zero. It is possible to obtain the coefficients a and k that Solving each coefficient a, k concretely, the following equations (9), (1
It becomes like 0).
すなわち、各係数a,kは車速ｕをパラメータとして、簡
略な形で示すと、下式（９）′，（10）′のようにな
る。 That is, the respective coefficients a and k are represented by the following equations (9) 'and (10)' in a simplified form, using the vehicle speed u as a parameter.
（A,B,C,D,Eは定数） なお、当然のことながら、上式（９）′，（10）′は簡
略化された車両モデルを用いて算出したものであるた
め、A,B,C,D,Eのパラメータ値は、車両の諸パラメータ
から、算出される厳密な値を取るのではなく、実験等で
修正した値を用いることになるが、車速ｕに対する各係
数a,kの変化の関数の形は上式（９）′，（10）′のま
まである。 (A, B, C, D, E are constants) It should be noted that, as a matter of course, since the above equations (9) ′ and (10) ′ are calculated using the simplified vehicle model, The parameter values of B, C, D, and E do not take exact values calculated from the parameters of the vehicle, but use values corrected by experiments, etc. The form of the function of the change of k remains the above equations (9) 'and (10)'.
従って、前輪操舵角βｆをｋ倍した値と前輪操舵角速度
ｆをａ倍した値の和に対応させて後輪操舵角βｒを制
御するように、特に、各係数ａ及びｋを車速ｕに応じて となるように変化させるようにすれば、あらゆるハンド
ルの回動操作に対するヨーレートの応答の位相ずれを完
全にゼロにすることが可能となり、車両の操安性を大幅
に向上させることができる。Therefore, in order to control the rear wheel steering angle βr corresponding to the sum of the value obtained by multiplying the front wheel steering angle βf by k and the value obtained by multiplying the front wheel steering angular velocity f by a, in particular, the coefficients a and k are set according to the vehicle speed u. hand By changing so as to satisfy the following condition, the phase shift of the yaw rate response to any turning operation of the steering wheel can be made completely zero, and the steerability of the vehicle can be greatly improved.
また、第２図、第３図は、それぞれ各係数a,kの車速ｕ
に対する値を、ある車両を例にして計算して示したもの
である。第２図に示すように、係数ａは全車速域に渡っ
て後輪を前輪の操舵方向とは反対方向に操舵するための
負の値に設定されており、車速ｕが例えば０〜20Km/h程
度の極低車速域においては車速ｕの増加に従って係数ａ
の絶対値|a|は急激に増加する。そして、車速ｕが例え
ば20Km/h以上の極低車速域〜高車速域においては、車速
ｕの増加に従って係数ａの絶対値|a|は徐々に減少す
る。また、第３図に示すように、係数ｋは、後輪を前輪
の操舵方向とは反対方向に操舵するための負の値から、
後輪を前輪の操舵方向と同方向に操舵するための正の値
に車速ｕの増加にしたがって変化するように設定されて
いる。車速ｕが例えば０〜60Km/h程度の極低車速域〜中
車速域においては、係数ｋは絶対値の大きな負の値から
「０」に車速ｕの増加に従って比較的急激に変化する。
車速ｕが例えば60Km/h程度以上の中高車速域において
は、係数ｋは「０」から絶対値の小さな正の値に比較的
緩やかに変化する。Further, FIG. 2 and FIG. 3 show the vehicle speed u of each coefficient a, k.
Is a value calculated for a vehicle as an example. As shown in FIG. 2, the coefficient a is set to a negative value for steering the rear wheels in the direction opposite to the steering direction of the front wheels over the entire vehicle speed range, and the vehicle speed u is, for example, 0 to 20 km / In the extremely low vehicle speed range of about h, the coefficient a increases as the vehicle speed u increases.
The absolute value of | a | increases sharply. Then, in the extremely low vehicle speed range to the high vehicle speed range in which the vehicle speed u is, for example, 20 Km / h or more, the absolute value | a | of the coefficient a gradually decreases as the vehicle speed u increases. Further, as shown in FIG. 3, the coefficient k is calculated from a negative value for steering the rear wheels in the direction opposite to the steering direction of the front wheels.
It is set so as to change to a positive value for steering the rear wheels in the same direction as the steering direction of the front wheels as the vehicle speed u increases. In an extremely low vehicle speed range to a medium vehicle speed range in which the vehicle speed u is, for example, about 0 to 60 km / h, the coefficient k changes from a large negative absolute value to "0" relatively rapidly as the vehicle speed u increases.
In the medium and high vehicle speed range where the vehicle speed u is, for example, about 60 Km / h or more, the coefficient k changes from "0" to a positive value having a small absolute value relatively slowly.
そして、第３図から明らかなように低車速域では係数ｋ
の値が負となるため、低車速時において小さい半径での
旋回が可能となり、低車速時の操縦性、安定性を向上さ
せることができる。また、前述のハンドルの回動操作に
対してヨーレートの位相ずれを完全にゼロにして車両の
操安性を大幅に向上させることを、操安性が特に問題と
なる中高速走行時にハンドルの回動操作によって車両が
直進状態から定常円旋回状態に移行する場合を例にして
説明しておく。As is clear from FIG. 3, the coefficient k is low in the low vehicle speed range.
Since the value of is negative, it is possible to make a turn with a small radius at low vehicle speed, and it is possible to improve maneuverability and stability at low vehicle speed. In addition, it is necessary to make the yaw rate phase shift completely zero with respect to the turning operation of the steering wheel to significantly improve the steering performance of the vehicle. A case where the vehicle shifts from a straight traveling state to a steady circular turning state by a dynamic operation will be described as an example.
まず、ハンドルの回動操作の初期においては、後輪の制
御操舵角βｒ＝ａ・ｆ＋ｋ・βｆ中の第２制御項ｋ・
βｆが小さく前輪が操舵されていく過程において、後輪
は第１制御項ａ・ｆに支配されて前輪の操舵方向とは
逆方向に操舵される。この後輪の操舵は、車両のヨー運
動をハンドルの回動方向に促進して車両に発生するヨー
レートの位相遅れをなくすので、車両の回頭性（操縦
性）が良好になる。一方、ハンドルの回動操作から多少
の時間が経過して前輪操舵角βｆが増加し始めると、第
２制御項ｋ・βｆが作用し始め、この第２制御項ｋ・β
ｆは後輪を前輪の操舵方向と同方向に操舵して、ハンド
ルの回動操作に対して車両に発生するヨーモーメントを
抑制するように作用するので、安定した車両挙動が得ら
れる。さらに時間が経過して、ハンドルの回動角が目標
値に近づくとハンドルの回動速度は減少し、車両のヨー
運動をハンドルの回動方向に促進する第１制御項ａ・
ｆが減少してゼロになる。これにより、車両の回頭のし
過ぎが抑止され、ハンドルの保持と同時に、車両を定常
円旋回状態に移行できる。この定常円旋回状態への移行
後には、第２制御項ｋ・βｆが後輪を前輪の操舵方向と
同方向に前輪操舵角βｆに比例した舵角に保持するの
で、車両はハンドルの操舵に対して低い感度でヨーレー
トを発生しながら旋回し続け、車両の走行安定性が良好
になる。そして、これらの一連の現象は、係数a,kを車
速に応じて変化させることにより車速が変化しても維持
されるので、上記実施例によれば、中高速走行時におけ
る車両の回頭性及び走行安定性が常に良好になる。First, in the initial stage of the turning operation of the steering wheel, the second control term k · in the control steering angle βr = a · f + k · βf of the rear wheels.
In the process in which βf is small and the front wheels are being steered, the rear wheels are steered in the direction opposite to the steering direction of the front wheels under the control of the first control term a · f. The steering of the rear wheels promotes the yaw motion of the vehicle in the turning direction of the steering wheel and eliminates the phase delay of the yaw rate generated in the vehicle, so that the turning performance (controllability) of the vehicle is improved. On the other hand, when the front wheel steering angle βf begins to increase after some time has passed from the turning operation of the steering wheel, the second control term k · βf begins to act, and the second control term k · β
Since f operates by steering the rear wheels in the same direction as the steering direction of the front wheels and suppressing the yaw moment generated in the vehicle in response to the turning operation of the steering wheel, stable vehicle behavior can be obtained. When the turning angle of the steering wheel approaches the target value after a further lapse of time, the turning speed of the steering wheel decreases, and the first control term a · that accelerates the yaw motion of the vehicle in the turning direction of the steering wheel.
f decreases to zero. As a result, excessive turning of the vehicle is suppressed, and at the same time when the steering wheel is held, the vehicle can shift to a steady circular turning state. After the transition to the steady circular turning state, the second control term k · βf keeps the rear wheels in the same steering direction as the front wheels at a steering angle proportional to the front wheel steering angle βf, so that the vehicle steers the steering wheel. On the other hand, the yaw rate is generated at a low sensitivity and the vehicle keeps turning while the traveling stability of the vehicle is improved. Then, since these series of phenomena are maintained even if the vehicle speed changes by changing the coefficients a and k according to the vehicle speed, according to the above-described embodiment, the turning performance of the vehicle during middle-high speed traveling and The driving stability is always good.
なお、各係数a,kは、第２図及び第３図から明らかなよ
うに低車速域にて非常に大きい値となるため、実用面で
問題となる可能性が強い。従って、低車速域では各係数
a,kを上式（９）′，（10）′の関数形をとらず、小さ
な値に固定する等の修正方法も当然のことながら考えら
れる。It should be noted that each coefficient a, k has a very large value in the low vehicle speed range, as is clear from FIGS. 2 and 3, so that there is a strong possibility that this will cause a problem in practical use. Therefore, in the low vehicle speed range, each coefficient
As a matter of course, a correction method such as fixing a, k to a small value without taking the functional form of the above equations (9) 'and (10)' can be considered.
第１図は本発明を実施するに用いられる四輪操舵車の操
舵系を概略的に示す構成図、第２図及び第３図は各係数
a,kの具体的な数値例を示すグラフ、第４図は各係数a,k
を算出するために用いた車両モデル図である。 符号の説明 １……ハンドル、６……前輪タイヤ、7,8……センサ、
９……後輪舵角演算器、10……差動増幅器、11……後輪
舵角検出器、12……増幅器、13……電気油圧サーボ弁、
14……油圧ポンプ、15……オイルシリンダ、17……後輪
タイヤ、βｆ……前輪操舵角、βｒ……後輪操舵角、ｕ
……車速、a,k……係数。FIG. 1 is a block diagram schematically showing a steering system of a four-wheel steering vehicle used for carrying out the present invention, and FIGS. 2 and 3 show respective coefficients.
Graph showing specific numerical values of a and k. Fig. 4 shows the coefficients a and k.
FIG. 6 is a vehicle model diagram used for calculating Explanation of symbols 1 …… Handle, 6 …… Front wheel tire, 7,8 …… Sensor,
9 …… Rear wheel steering angle calculator, 10 …… Differential amplifier, 11 …… Rear wheel steering angle detector, 12 …… Amplifier, 13 …… Electro-hydraulic servo valve,
14 …… hydraulic pump, 15 …… oil cylinder, 17 …… rear wheel tire, βf …… front wheel steering angle, βr …… rear wheel steering angle, u
…… Vehicle speed, a, k …… coefficients.
Claims (1)
１制御項ａ・ｆと、前輪操舵角βｆに係数ｋを乗算し
た第２制御項ｋ・βｆとの和である制御舵角ａ・ｆ＋
ｋ・βｆに後輪を操舵する車両の中高速走行時における
後輪操舵制御方法において、前記第１制御項ａ・ｆが
後輪を前輪の操舵方向とは逆方向に操舵する項として作
用するように前記係数ａの値を設定するとともに同係数
ａの絶対値が車速の増加にしたがって減少するように同
係数ａの値を設定し、かつ第２制御項ｋ・βｆが後輪を
前輪の操舵方向と同方向に操舵する項として作用するよ
うに前記係数ｋの値を設定するとともに同係数ｋの絶対
値が車速の増加にしたがって増加するように同係数ｋの
値を設定して、ハンドルの回動操作に対するヨーレート
の応答の位相ずれを車速とは無関係に全周波数領域にわ
たってなくすようにしたことを特徴とする四輪操舵車の
後輪操舵制御方法。1. A control steering angle a which is the sum of a first control term a · f obtained by multiplying a front wheel steering angular velocity f by a coefficient a and a second control term k · βf obtained by multiplying a front wheel steering angle βf by a coefficient k.・ F +
In the rear wheel steering control method at the time of medium speed running of the vehicle in which the rear wheels are steered to k · βf, the first control terms a · f act as terms for steering the rear wheels in the direction opposite to the steering direction of the front wheels. As described above, the value of the coefficient a is set so that the absolute value of the coefficient a decreases as the vehicle speed increases, and the second control term k · βf sets the rear wheel to the front wheel. The value of the coefficient k is set so as to act as a term for steering in the same direction as the steering direction, and the value of the coefficient k is set so that the absolute value of the coefficient k increases as the vehicle speed increases. A rear-wheel steering control method for a four-wheel steering vehicle, characterized in that the phase shift of the yaw rate response to the turning operation of the vehicle is eliminated over the entire frequency range regardless of the vehicle speed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59087094A JPH07112826B2 (en) | 1984-04-27 | 1984-04-27 | Rear-wheel steering control method for four-wheel steering vehicle |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59087094A JPH07112826B2 (en) | 1984-04-27 | 1984-04-27 | Rear-wheel steering control method for four-wheel steering vehicle |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60229873A JPS60229873A (en) | 1985-11-15 |
| JPH07112826B2 true JPH07112826B2 (en) | 1995-12-06 |
Family
ID=13905361
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59087094A Expired - Lifetime JPH07112826B2 (en) | 1984-04-27 | 1984-04-27 | Rear-wheel steering control method for four-wheel steering vehicle |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07112826B2 (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60248481A (en) * | 1984-05-21 | 1985-12-09 | Toyota Central Res & Dev Lab Inc | Rear wheel steering angle control device of car |
| JPS6141676A (en) * | 1984-08-02 | 1986-02-28 | Toyota Central Res & Dev Lab Inc | Rear-wheel steering angle controller for vehicles |
| JPS61122080A (en) * | 1984-11-19 | 1986-06-10 | Toyota Central Res & Dev Lab Inc | Rear wheel steering angle controller for vehicle |
| JP2575618B2 (en) * | 1985-04-25 | 1997-01-29 | 株式会社豊田中央研究所 | Vehicle rear wheel steering angle control device |
| JPS62149560A (en) * | 1985-12-24 | 1987-07-03 | Nissan Motor Co Ltd | Steering angle control device for vehicle |
| JP2578142B2 (en) * | 1987-11-30 | 1997-02-05 | 日産自動車株式会社 | Auxiliary steering system for vehicles |
| JP2740176B2 (en) * | 1987-12-28 | 1998-04-15 | 日産自動車株式会社 | Vehicle rear wheel steering method |
| JPH0829670B2 (en) * | 1988-02-18 | 1996-03-27 | 日産自動車株式会社 | Front and rear wheel drive force distribution control vehicle auxiliary steering method |
| JP2549708B2 (en) * | 1988-07-05 | 1996-10-30 | 日産自動車株式会社 | Rear-wheel steering system for 4-wheel steering vehicle |
| JP2549709B2 (en) * | 1988-07-05 | 1996-10-30 | 日産自動車株式会社 | Rear-wheel steering system for 4-wheel steering vehicle |
| JP2982595B2 (en) * | 1993-12-27 | 1999-11-22 | 日産自動車株式会社 | Actual steering angle control device for vehicle |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58164477A (en) * | 1982-03-24 | 1983-09-29 | Nissan Motor Co Ltd | Rear-wheel steering controller |
| JPS60161263A (en) * | 1984-01-31 | 1985-08-22 | Nissan Motor Co Ltd | Control for rear-wheel steering |
-
1984
- 1984-04-27 JP JP59087094A patent/JPH07112826B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60229873A (en) | 1985-11-15 |
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