JP5848137B2 - Road curvature estimation system - Google Patents

Description

DESCRIPTION OF EMBODIMENTS Referring to FIG. 1, a predictive collision detection system 10 incorporated in a host vehicle 12 detects a radar system 14 for detecting an object outside the host vehicle 12 and the movement of the host vehicle 12. A set of sensors, including a yaw rate sensor 16, for example, a gyro sensor and a speed sensor 18. The yaw rate sensor 16 and the speed sensor 18 obtain the measured values of the yaw rate and speed of the host vehicle 12, respectively. A radar system 14, such as a Doppler radar system, includes an antenna 20 and a radar processor 22, which generates an RF signal that is transmitted by the antenna 20 and reflected by objects in its field of view. . The radar processor 22 demodulates the associated reflected RF signal received at the antenna 20 to detect a signal responsive to one or more objects illuminated by the RF signal transmitted by the antenna 20. For example, the radar system 14 obtains measured values of target distance, distance change rate, and azimuth angle at fixed coordinates of the host vehicle 12.

  Referring to FIG. 2, the antenna 20 generates a radar beam 23 of RF energy, which is responsive to the beam control element 24 for electrons throughout the azimuth range, eg, ± γ, eg, ± 50 °. The distance range of this radar beam is, for example, about 100 meters from the host vehicle 12, which is detected sufficiently in advance from the expected collision with the host vehicle 12. Actions that the host vehicle 12 may mitigate so as to be far enough to allow it to do so, thereby avoiding an expected collision or reducing the resulting damage or injury Is adapted to make it possible to take Radar processor 22, yaw rate sensor 16, and speed sensor 18 are operably connected to signal processor 26, which operates according to an associated predictive collision detection algorithm to detect an object, such as target vehicle 36 (FIG. 3). And if so, the action to be taken accordingly, for example the associated alarm system 28 or safety system 30 (eg the front airbag system) Such as activating, or using the vehicle control system 32 (e.g., an associated braking or steering system) to take avoidance actions, thereby avoiding or reducing the consequences of an anticipated collision, etc. One or more actions are also determined.

  Referring to FIG. 3, the host vehicle 12 is shown moving along a straight or curved multi-lane road 34 and the target vehicle 36 moves in the opposite direction toward the host vehicle 12. Is shown. In general, there may be any number of target vehicles 36 that fit on the road 34, each moving in the same or opposite direction as the host vehicle 12. These target vehicles 36 may be in a hosting lane 38 or in a neighboring lane 40 that is adjacent to or spaced apart from the host lane 38 but generally parallel thereto. For the purpose of analysis, it is assumed that the host vehicle 12 moves stably along the center line 41 of its lane 38 without wobbling within the lane, and the road curvature of all parallel lanes 38, 40 is the same. . Assuming that the road curvature is small, the difference between the heading angle of the host vehicle 12 and the heading angle of any detectable target vehicle 36 is less than 15 °.

、および方位角ηの計測値に加えて、これらすべての計測値の対応する誤差共分散マトリックスを使用して、ホスト固定座標系において各サンプリング時に、好ましくは誤差をできる限り少なくして、各ターゲットの２次元位置、速度および加速度

を推定する。 Referring to FIG. 4, the predicted collision detection system 10 is mounted on the host vehicle 12 and the measured values of the speed U ^h and the yaw rate ω ^h of the host vehicle 12 from the speed sensor 18 and the yaw rate sensor 16 respectively. Target distance r and distance change rate for all target vehicles 36 from the radar system 14

And the corresponding error covariance matrix of all these measurements in addition to the measured values of azimuth η and each target in the host fixed coordinate system, preferably with as little error as possible, at each sampling. Two-dimensional position, velocity and acceleration

Is estimated.

  The predictive collision detection system 10 is 1) a road curvature estimation subsystem 42 that estimates the curvature of the road 34 using measurements from host vehicle motion sensors, i.e., yaw rate sensor 16 and speed sensor 18, 2) radar beam. 23, an unconstrained target state estimation subsystem 44 that estimates the state of the target illuminated by the radar processor 22 and detected by the radar processor 22; 3) the target lane 38, 40 for each possible lane 38, 40; A constrained target state estimation subsystem 46 that estimates the constrained state for the target, assuming that it is constrained on the road, either within or in the neighboring lane 40; 4) the best estimate of the target state is unconstrained A target that is in a target state or constrained by one of the constraints A target state determination subsystem 48 to determine if it is a get state; and 5) an unconstrained target state estimate is fused with the appropriate constraints identified by the target state determination subsystem 48, thereby generating a fusion target state Target state fusion subsystem 50. The best estimate of the target state—either the unconstrained target state or the fusion target state—is then used by the decision or control subsystem to determine if the host vehicle 12 is at risk of colliding with the target. If so, determine what is the best action to mitigate the result, for example, either the alarm system 28, the safety system 30, or the vehicle control system 32, or a combination thereof It is executed by the action of. Where possible, the use of the road 34 geometry as a constraint on the target dynamics provides a more accurate estimate of the target state, thereby improving the reliability of the responsive behavior. .

Referring to FIG. 5, a method 500 for detecting a target state, i.e., a dynamic state variable, in terms of the host vehicle 12, is shown, for example, by the signal processor 26, steps (502), ( 504), the speed U ^h and yaw rate ω ^h of the host vehicle 12 relative to the road 34 are read from the speed sensor 18 and the yaw rate sensor 16, respectively. Then, in step (506), the curvature parameter of the road 34 and its associated covariance are estimated using the first Kalman filter 52 and the second Kalman filter 54, which are the states of the host vehicle 12 (ie, , The host vehicle 12 dynamic state variables) and their associated covariances, respectively, and then the road 34 curvature parameters and their associated covariances, respectively, where the road 34 curvature parameters and associated That covariance is subsequently used by the constrained target state estimation subsystem 46 to generate the associated constrains for the possible target vehicle 36 potential locations.

ここで、Ｒは区間の半径である。一般に、平坦な道路３４の部分に対して、曲率変化は、道路３４に沿った距離ｌの関数として、いわゆるクロソイド（clothoid）モデルによって、次式のように記述することができる：

ここで、Ｃ_１＝１／Ａ^２であり、Ａはクロソイドパラメータと呼ばれる。
図６を参照すると、ヘディング方向を定義する、ヘディング角θは次式で定義される：

式（２）を式（３）に代入すると、次式が得られる。

A correctly designed and constructed road 34 can be described by a set of parameters including curvature, where the curvature of the section of road 34 is defined by:

Here, R is the radius of the section. In general, for a portion of a flat road 34, the curvature change can be described by the so-called clothoid model as a function of the distance l along the road 34:

Here, C ₁ = 1 / A ² and A is called a clothoid parameter.
Referring to FIG. 6, the heading angle θ, which defines the heading direction, is defined by the following equation:

Substituting equation (2) into equation (3) yields:

ヘディング角θが１５°の範囲であること、すなわち｜θ｜＜１５°を仮定すると、式（５）および式（６）は、次のように近似される。

Referring to FIG. 6, the equation of the road 34, that is, the road equation in the xy coordinates is given by the following equation.

Assuming that the heading angle θ is in the range of 15 °, that is, | θ | <15 °, the equations (5) and (6) are approximated as follows.

Thus, the road 34 is modeled by an incremental road equation with curvature coefficients (or parameters): C ₀ and C ₁ . This incremental road equation accounts for a wide range of road shapes such as: (1) straight road 34: C ₀ = 0 and C ₁ = 0, 2) circular road 34: C ₁ = 0, and 3) heading General road 34 having an arbitrary shape with a change in angle θ of less than 15 °: C ₀ > 0.
The road curvature parameters C ₀ , C ₁ are based on the assumption that the host vehicle 12 moves along the center line 41 of the road 34 or the associated host lane 38 (yaw rate sensor 16 and It is estimated using data from the speed sensor 18).

のデータから計算することができる。しかしながら、一般的に、それぞれヨーレートセンサ１６および速度センサ１８からのヨーレートω^ｈおよび速度Ｕ^ｈの計測値はノイズが多い。第１のカルマンフィルタ５２によって実現されるホスト状態フィルタは、ヨーレートω^ｈおよび速度Ｕ^ｈの関連するノイズの多い計測値から、

の推定値を生成するのに有益であり、その後に、第２のカルマンフィルタ５４によって実現される曲率フィルタを使用して、曲率パラメータＣ_０、Ｃ_１の平滑化された推定値が生成される。ホスト状態フィルタに対するホスト車両１２の運動力学は、所定の組の動力学方程式（この場合には一定速度）に従い、これらは次のように与えられる。

また、ここでＴはサンプリング周期であり、上添え字(-)^ｈは、フィルタがホストフィルタであることを指示するために使用され、Ｕ^ｈおよびω^ｈは、ホスト車両１２の速度およびヨーレートの計測値である。第１のカルマンフィルタ５２は、図４に示すように、ホスト状態

およびその誤差共分散

を推定するために実現される。 The road curvature parameters C ₀ , C ₁ are responsive to measurements of the yaw rate ω ^h and speed U ^h of the host vehicle 12 from available host vehicle 12 motion sensors,

It can be calculated from the data. However, generally, the measured values of the yaw rate ω ^h and the speed U ^h from the yaw rate sensor 16 and the speed sensor 18 are noisy, respectively. The host state filter implemented by the first Kalman filter 52 is derived from the noisy measurements associated with the yaw rate ω ^h and the velocity U ^h ,

Is then used to generate a smoothed estimate of the curvature parameters C ₀ , C ₁ using a curvature filter implemented by the second Kalman filter 54. The kinematics of the host vehicle 12 with respect to the host state filter follows a predetermined set of dynamic equations (in this case constant speed), which are given as follows:

Where T is the sampling period, the superscript (-) ^h is used to indicate that the filter is a host filter, and U ^h and ω ^h are the speed and yaw rate of the host vehicle 12 It is a measured value. As shown in FIG. 4, the first Kalman filter 52

And its error covariance

Is realized to estimate

との関係は、以下のように導かれる。 The host state estimate from the first Kalman filter 52, i.e., the host state filter, is then input to a second Kalman filter 54, i.e., a curvature coefficient (or parameter) filter, to generate a composite measurement. Used, where the associated Kalman filters 52, 54 operate according to the Kalman filter filtering process described in more detail in the appendix below. Road curvature parameters C ₀ , C ₁ and host state variables

The relationship with is derived as follows.

ここで、

、すなわちホスト車両１２のヨーレートであり、

、すなわちホスト車両１２の速度であることに注目して、式（２）のクロソイドモデルを式（１２）に代入すると、次式が得られる。

From equation (4), the radius R of road curvature is generally expressed as a function of distance l along the road, R (l), as shown in FIG. Differentiating both sides of equation (4) gives the following equation.

here,

That is, the yaw rate of the host vehicle 12,

That is, paying attention to the speed of the host vehicle 12, substituting the clothoid model of Expression (2) into Expression (12), the following expression is obtained.

式（１４）の両辺の微分をとると次式を得る。

Ｃ_１の定義を使用して、式（２）から、Ｃ_１は、ホスト状態によって次のように表わすことができる。

Clothoid parameter C ₀ is given the value of the curvature C at l = 0 or the following formula.

Taking the derivative of both sides of equation (14) yields:

Using the definition of C _1, from equation (2), C ₁ can be expressed by the host state as follows.

を生成する、第２のカルマンフィルタ５４、すなわち曲率フィルタのためのシステム方程式は、以下のように与えられる。

Δｔは第２のカルマンフィルタ５４の更新時間周期であり、計測値ベクトル

の要素の値は、曲率フィルタの状態変数―すなわち、クロソイドパラメータＣ_０、Ｃ_１―の対応する値によって与えられる。 Curvature estimate

The system equation for the second Kalman filter 54, that is, the curvature filter, that yields is given by:

Δt is the update time period of the second Kalman filter 54, and the measured value vector

Are given by the corresponding values of the state variables of the curvature filter, ie the clothoid parameters C ₀ , C ₁ .

は、推定状態

から以下のように変換され、

関連する計測値の共分散は、次式で与えられる。

Measured value,

Is the estimated state

Is converted to

The covariance of the associated measurement is given by

It should be understood that other systems and methods for estimating the curvature parameters of the road 34 can be substituted into the road curvature estimation subsystem 42 for those described above. For example, a road curvature parameter may be estimated from an image of the road 34 by a visual system instead of or in conjunction with the above-described system based on measurements of velocity U ^h and yaw rate ω ^h from associated motion sensors. it can. Further, it should be understood that the yaw rate can be in various ways or using various means, for example, but not limited to, a yaw gyro sensor, a steering angle sensor, a differential wheel speed sensor, or a GPS sensor, A combination or a function of measurements from them (eg, inter alia, a function of steering angular velocity) can be measured or identified.

の計測値、および方位角ηの計測値がレーダープロセッサ２２から読み取られて、拡張カルマンフィルタ５６、すなわち主フィルタへの入力として使用され、このフィルタは、ステップ（５１０）において、非拘束ターゲット状態―すなわち、ターゲットの動力学状態変数―の推定値を生成し、この推定値は、ホスト車両１２と一緒に移動する、ホスト車両１２の局所座標系（すなわち、ホスト固定座標系）における相対値である。ステップ（５１２）において、非拘束ターゲット状態、すなわちターゲット速度および加速度は、図３に示すように、現在時刻における、ホスト車両１２に固定された絶対座標系の絶対座標に変換され、それによって、拘束ターゲット状態の推定値を生成するために、以下に記述する関連する拘束方程式に使用されるときに、道路拘束式がその中で導出され、それに対して関連する曲率パラメータが一定であると仮定される、絶対座標系に整合させられる。絶対座標系は、現在時刻における空間内の移動座標系を重ね合わせ、それによって、ステップ（５１２）における変換は、速度および加速度に関係する補正項―ホスト車両１２の運動を説明する―を、ｘおよびｙ方向の両方で、対応するターゲット推定値に加算することによって実現される。 Referring again to FIG. 5, in step (508), the target distance r, the distance change rate.

And the azimuth angle η measurement are read from the radar processor 22 and used as input to the extended Kalman filter 56, the main filter, which in step (510) is the unconstrained target state—ie , Generating an estimate of the target dynamic state variable—the estimate is a relative value in the local coordinate system of the host vehicle 12 (ie, the host fixed coordinate system) that moves with the host vehicle 12. In step (512), the unconstrained target state, i.e., target velocity and acceleration, is converted into absolute coordinates in an absolute coordinate system fixed to the host vehicle 12 at the current time, as shown in FIG. When used in the associated constraint equation described below to generate an estimate of the target state, the road constraint equation is derived therein, and the associated curvature parameter is assumed to be constant. Matched to the absolute coordinate system. The absolute coordinate system superimposes the moving coordinate system in space at the current time, so that the transformation in step (512) is a correction term relating to speed and acceleration—explaining the motion of the host vehicle 12— This is achieved by adding to the corresponding target estimate in both the y and y directions.

The result of the coordinate transformation in step (512) of the output from the extended Kalman filter 56 is then partitioned into the following parts, corresponding to the x and y positions of the target vehicle 36 with respect to the host vehicle 12, respectively. The character 1 means an unconstrained state of the target vehicle 36.

  Referring again to FIG. 5, following steps (506) and (512), various constraints are applied to the possible trajectory of the target vehicle 36 in steps (514) to (524), described in more detail below. By testing, it is determined whether the target vehicle 36 is likely moving according to one of the possible constraints. For example, assuming that the restraint is from a set of lanes including host lane 38 and possible neighboring lanes 40, target vehicle 36 likely to be moving according to one of the possible restraints. Is likely moving on either the host lane 38 or one of the possible neighboring lanes 40. In step (524), the hypothesis that the target vehicle 36 is moving over one of the host lanes 38 or potential neighboring lanes 40 is tested for each potential lane. If this hypothesis is not satisfied for one of the possible lanes, in step 526 the target state is assumed to be an unconstrained target state, which is then followed by a subsequent predictive collision detection analysis and Used for responding control. Otherwise, from step (524), in step (528), the target state is identified by target state fusion subsystem 50 as an unconstrained target state and most likely in step (524). Calculated as a fusion with the associated constraint state.

  Consider the process from step (514) to step (524) to determine whether and if the target is constrained by a constraint and what is the most likely constraint. Previously, the process of fusing the unconstrained target state with the constrained state will first be described for the case of the target vehicle 36 moving in the same lane as the host vehicle 12. It is assumed that the host vehicle 12 stably moves within the lane along the center line of the lane 38 without wobbling, and that the road curvature of all the parallel lanes 38 and 40 is the same, and the absolute coordinate system Are fixed on the host vehicle 12 at the current time, these constraints are applied in the y direction, and the y direction state variable is derived from a road equation that is a function of the x direction state variable.

Assuming that the target vehicle 36 is moving in the same lane as the host vehicle 12 and using a road constraint having an estimated coefficient (or parameter), at step (514), the constraint state variable is the lateral power The academic variables are given as follows.

最後に、ターゲット状態の構成推定値（composed estimate）は、以下のようになる。

In step (528), two y-coordinate estimates, one from the main filter and the other from the road constraint, are merged as follows.

Finally, the target state's composed estimate is:

Next, when it is determined in step (530) that the target vehicle 36 is traveling on the host lane 38 from step (514) to step (524), this configuration estimated value is the estimated value of the target state. Will be output.
The process from step (514) to step (524) to determine if the target is likely to be constrained by a constraint, and if so, what is the most likely constraint According to the assumption that the target follows the same road 34, if it is known that the target vehicle 36 is traveling on a particular lane, the estimated road parameters for that lane are estimated for the target dynamics. It would be desirable to use it as a constraint in the main filter. However, knowledge of whether the target vehicle 36 is currently in that lane is usually not available, especially when the target is moving on the curved road 34. Since the road equation (8) is only for the host lane 38 in the host central coordinate system, constraint filtering requires knowing which lane the target is in, and different constraints for different lanes. An equation is needed.

ここで、Ｂはレーンの幅、ｍは記述しようとするレーンを表わす（ｍ＝０はホストレーン８０に対応、ｍ＝１は右近傍レーン４０に対応、ｍ＝−１は左近傍レーンに対応する、など）。ターゲットレーン位置の事前知識なしに、多重拘束システム（いわゆる多重モデルシステムに類似する）を形成する多重拘束条件のそれぞれが試験されて、拘束条件のいずれかが活性であれば、そのどれが活性であるかが判定される。多重拘束（ＭＣ）システムは、有限の数Ｎ^Ｃの拘束の１つを受ける。任意の時間において、１つの拘束条件だけが有効であり得る。そのようなシステムは、ハイブリッドと呼ばれる―すなわちそれらは連続（ノイズ）状態変数に加えて、不連続の数の拘束条件の両方を有する。 Neglecting the difference in road curvature parameters between these parallel lanes, ie assuming that the curvature of each lane is the same, the road equation for any lane can be written as:

Here, B represents the width of the lane, m represents the lane to be described (m = 0 corresponds to the host lane 80, m = 1 corresponds to the right neighbor lane 40, and m = -1 corresponds to the left neighbor lane. Etc.). Without prior knowledge of the target lane position, each of the multiple constraints forming a multiple constraint system (similar to a so-called multiple model system) is tested and if any of the constraints is active, It is determined whether there is any. Multiple constraint (MC) system is subject to one of the constraints of the number ^{N C} of finite. Only one constraint may be effective at any given time. Such systems are called hybrids--that is, they have both a continuous (noise) state variable and a discrete number of constraints.

ここで、

は、ｔ_ｋで終了するサンプリング周期中に有効な、時間ｔ_ｋにおける拘束条件を表わす。
拘束条件：可能性のあるＮ^Ｃ拘束条件の中で

：拘束条件

を使用する時間ｔ_ｋにおける状態推定

：拘束条件

下における時間ｔ_ｋにおける共分散マトリックス

：ターゲットが時間ｔ_ｋ−１において拘束条件ｊに従っている確率 In order to facilitate the solution of this problem, the following definitions and modeling assumptions are made.
Constraint equation:

here,

It is effective during a sampling period which ends at t _k, representing the constraint condition at the time t _k.
Among the possible N ^C constraints: constraints

:Restraint condition

State estimation at time t _k using

:Restraint condition

Covariance matrix at time t _k below

: Probability that the target complies with constraint j at time t _k−1

マルコフ連鎖を―２つ以上の可能性のある拘束状態を有するシステムに対して―実現するために、それぞれの走査時間において、ターゲットが拘束状態ｉから状態ｊに移行する確率ｐ_ｉｊがあることを仮定する。これらの確率は、前もって分かっていると仮定し、以下に示す確率移行マトリックスで表わすことができる。

が正しい（

が有効である）旧確率は、

ここで、Ｚ^０は旧情報であり、正しい拘束は、仮定されたＮ^Ｃの可能性のある拘束条件の中にあるので、

The constrained jump process is a Markov chain with the following known transition probabilities:

In order to realize a Markov chain—for a system with more than one possible constraint state—at each scan time, there is a probability p _ij that the target will transition from constraint state i to state j. Assume. These probabilities are assumed to be known in advance and can be represented by the probability transition matrix shown below.

Is correct (

Is the old probability)

Here, Z ⁰ is the old information, correct restraint, since in the constraint conditions that might postulated N ^C,

を計測値として使用して、Ｎ^Ｃの拘束条件状態推定値（constraint-conditioned state estimates）を組み合わせて更新する。多重拘束（ＭＣ）推定アルゴリズムの一態様において、拘束状態推定出力は、すべての拘束条件状態推定値の複合組合せである。この拘束状態推定が正当である場合，すなわち拘束状態推定が、非拘束状態推定に対応する、例えば一致する、場合には、ターゲット状態は、拘束および非拘束の状態推定を融合することによって与えられ、そうでない場合には、ターゲット状態は非拘束状態推定によって与えられる。多重拘束（ＭＣ）推定アルゴリズムのこの態様は、以下のステップを含む。 The constrained target state estimation subsystem 46 determines whether the target state corresponds to a possible constrained state, and if so, identifies the most likely constrained state.
A multiple constraint (MC) estimation algorithm is used to estimate the unconstrained state along with the likelihood function and probability calculation associated with each constraint.

The use as a measurement value, and updates combined constraints state estimate of N ^C a (constraint-conditioned state estimates). In one aspect of a multiple constraint (MC) estimation algorithm, the constraint state estimation output is a composite combination of all constraint condition state estimates. If this constrained state estimate is valid, i.e., the constrained state estimate corresponds to, for example, coincides with the unconstrained state estimate, the target state is given by fusing the constrained and unconstrained state estimates. Otherwise, the target state is given by unconstrained state estimation. This aspect of the multiple constraint (MC) estimation algorithm includes the following steps:

ここで、

であり、Ｂはレーンの幅である。言い換えると、拘束状態推定値は、ターゲット車両３６が位置する可能性のある、それぞれの可能性のあるレーンの中心線のｙ位置に対応、例えば、一致する。 1. Estimating state variables from multiple constraints: In step (514), using the multilane road equation (34) to replace the first row of equation (25), the multiple constraint state estimate is given by .

here,

And B is the width of the lane. In other words, the constrained state estimate corresponds to, for example, the y position of each possible lane centerline where the target vehicle 36 may be located.

ここで、

は式（２７）および式（２８）によって与えられ、

は式（２４）から、

は曲率フィルタから得られる。 The associated covariance is given by

here,

Is given by equation (27) and equation (28),

From equation (24)

Is obtained from a curvature filter.

を用いて、次式のように得られる。

2. Restriction condition update: In step (516), restriction condition j = 1,. . . For each N ^C , in addition to the constraint likelihood function, the state estimate and covariance are updated subject to valid constraints. The updated state estimate and covariance corresponding to constraint j are measured values.

Is obtained as follows.

において、次式のように求められ、

ここで、ガウス分布Ｎ（；，）は平均値

および関連する共分散

を有する。 3. Likelihood calculation: In step (518), constraints j = 1,. . . For each of N ^C , assuming a Gaussian distribution of measurements around the constraint state estimate, the likelihood function corresponding to constraint j is the value of the unconstrained target state estimate.

In the following equation,

Where the Gaussian distribution N (;,) is the mean value

And related covariances

Have

ここで、拘束ｊが有効である移行の後の確率

は次式

で与えられ、正規化定数は以下で与えられる。

4). Constraint probability equation: In step (520), the update constraint probability is expressed as constraint j = 1,. . . For each of N ^C , it is calculated as

Where the probability after the transition that the constraint j is valid

Is

And the normalization constant is given by

5. Overall state estimation and covariance: In step (522), the latest constraint state estimate and covariance are given by:

The output of the estimator from step (522) in the above algorithm is then used as an unconstrained estimate in the fusion process described by equations (29) and (30), and the result of equation (33) Instead of, the result of equation (52) is used in equation (32).
Imposing road constraints on the target dynamic state variable when the target vehicle 36 is not following the road 34 or changing lanes results in an inaccurate estimate, which is related to May be worse than using constraint estimates. However, correct road constraints may appear inappropriate due to noise-related estimation errors. Therefore, if the restraint is appropriate, for example, if the target vehicle 36 is following a particular lane, those restraints are effectively maintained, and if they are not appropriate, the target vehicle 36 is removed from that lane, for example. It is beneficial to incorporate means that can quickly remove them if they deviate. Unconstrained target state estimation plays a useful role in road constraint validation because it provides independent target state estimates.

のように、

の推定値として表わされ、ここで

は真のターゲット状態であり、

は、道路３４（またはレーン）に沿って移動するターゲットの真の状態である。ステップ（５２４）において、「同一ターゲット」仮説が検証される、すなわち

One approach is to test the hypothesis that unconstrained target state estimation satisfies the road constraint formula, or equivalently, and that the constraint and unconstraint estimates correspond to the same target. It is. Optimal testing requires the use of all available target state estimates in the history up to time t _k and is generally not practical. One practical approach is sequential hypothesis testing, in which tests are performed based only on the latest state estimates. According to the notation used above, the difference between the constrained and unconstrained target state estimates (y direction only) is

like,

Expressed as an estimate of where

Is the true target state,

Is the true state of the target moving along the road 34 (or lane). In step (524), the “same target” hypothesis is verified, ie

は、拘束からの誤差

と独立であると仮定する。差

の共分散は、仮説Ｈ_０の下で、次式で与えられる。

Main filter error

Is the error from the constraint

And are independent. difference

Covariance, under the hypothesis H _0, is given by the following equation.

閾値は次のように選択され、

ここでαは所定の誤差許容値である。ここで留意すべきことは、上記のガウス誤差仮定に基づいて、

は、ｎ_ｙ自由度のカイ二乗分布を有することである。この閾値の選択は、重要な設計因子であり、特定の応用要求に基づくべきである。道路車両衝突予測において、ホストレーン３８内のターゲットは、衝突コースにあるとみなされ、近傍レーン４０の１つにおけるターゲットよりもより危険であると考えられる。 Assuming that the estimation error is Gaussian, the test for H ₀ vs. H ₁ is as follows:
Adopt H _{0 in the} following cases

The threshold is selected as follows:

Here, α is a predetermined error tolerance. Note that based on the Gaussian error assumption above,

Is to have a chi-square distribution of n _y degree of freedom. The selection of this threshold is an important design factor and should be based on specific application requirements. In road vehicle collision prediction, the target in the host lane 38 is considered to be on the collision course and is considered more dangerous than the target in one of the nearby lanes 40.

  Thus, since constraint filtering can provide an accurate target state estimate, it is desirable to have a high threshold (low error tolerance) for targets in the host lane 38, as opposed to “ The “lane change” operation does not pose a threat to the host vehicle 12. On the other hand, the target in the neighboring lane 40 is usually regarded as an overtaking vehicle. Although constrained filtering can further reduce the false alarm rate, such a target “change lane” operation (to host lane 38) will pose a real threat to host vehicle 12. Therefore, if the false alarm rate is already sufficiently low, it is desirable to give a low threshold (high error tolerance) to targets in neighboring lanes.

を有する拘束方程式は、時間ｔ_ｋ（現在時間）において、ターゲットが存在する可能性の最も高いレーンに対応する。この最も可能性の高いレーンをｌ_ｔで表わすと、次のようになる。

Based on the above analysis, the hypothesis testing method efficiently uses different thresholds for targets in different lanes, and the multi-constraint filtering algorithm provides knowledge about the lane where the target is likely to currently exist To do. Assuming there are N ^C possible lanes on road 34 and each lane is described by a constraint equation, the highest probability for the target

Corresponds to the lane where the target is most likely present at time t _k (current time). When representing the most probable lane l _t, as follows.

で表わされ、これは

の推定値であり、ここで

は真のターゲット状態であり、

は、レーンｌ_ｔに沿って移動するターゲットの真の状態である。 The difference between the unconstrained state estimate and the l _t restraint state estimate (only in the y direction) is

This is represented by

Where

Is the true target state,

Is the true state of the target which moves along the lane l _t.

拘束推定誤差は次式で与えられる。

The test for the “same target” hypothesis is then:

The constraint estimation error is given by the following equation.

ここで、

であり、閾値は次のようになり、

ここで、

である。 Assuming that the estimation error is an independent Gaussian distribution, the H ₀ vs. H ₁ test is:
Adopt H _{0 in the} following cases

here,

And the threshold is

here,

It is.

Such a lane adaptation hypothesis testing scheme allows the target state estimation output to be quickly switched to unconstrained estimation when the target vehicle 36 deviates from its current lane, and at the same time the target estimation accuracy in the host lane 38. Is substantially improved by constraint filtering.
In another aspect of the multiple constraint (MC) estimation algorithm, the constraint state estimate used for hypothesis testing is most likely a separate constraint target state estimate, rather than a composite combination of all constraint target state estimates. (Ie, with a “winner takes everything” strategy). If this most probable constrained state estimate is correct, i.e., the most probable state estimate corresponds, for example, to an unconstrained state estimate, then the target state is most likely It is given by fusing a highly likely constrained state estimate and an unconstrained state estimate, otherwise the target state is given by an unconstrained state estimate.

  In yet another aspect of the multiple constraint (MC) estimation algorithm, a hypothesis test is performed for each of the constraint state estimates. If no hypothesis is adopted, the target state is given by unconstrained state estimation. If one of the hypotheses passes, the target state is given by fusing the corresponding constrained and unconstrained state estimates. If more than one hypothesis is adopted, the most likely restraint state is identified by voting on results from multiple approaches or by repeating hypothesis testing with different relevant thresholds. The

  In general, the number of constraints (i.e., the number of road lanes) can vary over time, as do the parameters associated therewith, e.g., the width of the road lane, Absorb changes in the environment. For example, in one movement, the host vehicle 12 is divided into one lane road, two lane road including oncoming traffic, three lane road including central route change lane, four lane road including two lane oncoming traffic, or multiple lane division. There is a possibility of driving on freeways.

  Road vehicle tracking simulations using constrained and unconstrained filtering were performed for four scenarios. In all scenarios, the host vehicle 12 is moving at 15.5 m / sec, and the target vehicle is approaching on the same road 34 at 15.5 m / sec. The initial target position was assumed to be 125 meters away from the host in the x direction and the lane width for all lanes was 3.6 meters. The measurement value variance of the vehicle speed sensor was 0.02 m / s, and the variance of the gyroscope yaw rate measurement value was 0.0063 rad / s. The dispersion of measured values of radar distance, distance change rate, and azimuth were 0.5 m, 1 m / s, and 1.5 °, respectively. Simulation results were then generated from 100 Monte Carlo runs of the associated tracking filter.

In the first scenario, the host vehicle 12 and the target vehicle 36 are moving on a straight road 34 (C ₀ = 0 and C ₁ = 0), and the target vehicle 36 moves toward the host vehicle in the same lane. It was moving. FIGS. 8a-d show the results of target state estimation and road curvature estimation for the unconstrained filtering scheme and the constrained filtering scheme, and FIGS. The RMS error of lateral position, lateral velocity and lateral acceleration is shown. The estimation error from constraint filtering has been substantially reduced. When the target vehicle 36 is more than 65 meters away from the host vehicle 12 before 48 radar scans, constraint filtering reduces the error by more than 40 percent in the target lateral velocity estimate and 60 percent in the lateral acceleration estimate. A reduction of the error exceeding was obtained. When the target vehicle 36 is at a distance of less than 65 meters from the host vehicle 12, this is more appropriate for collision prediction, with a lateral position estimation error of over 50 percent, and a lateral velocity and side of over 90 percent. The acceleration estimation error was reduced by constraint filtering.

In the second scenario, the host vehicle 12 and the target vehicle 36 move on a curved road 34 (C ₀ = −10 ⁻⁵ and C ₁ = −3 × 10 ⁻⁵ ), and the target vehicle 36 is in the same lane. It was moving toward the host vehicle. FIGS. 10a to 10d show the results of target state estimation and curvature estimation of the unconstrained filtering method and the constrained filtering method, and FIGS. 11a and 11b show the average lateral position and lateral of the target vehicle 36 of the unconstrained and constrained filtering method. The RMS error of velocity and lateral acceleration is shown. When the target vehicle 36 was less than 65 meters from the host vehicle 12, the estimation error from constraint filtering was substantially reduced after about 48 radar scans. When the target vehicle 36 is at a distance of about 100 meters from the host vehicle 12, the estimation error was the same for constrained filtering and unconstrained filtering before 20 radar scans.

  For a target vehicle 36 located at a distance between 100 meters and 65 meters from the host vehicle 12, constrained filtering results in an approximately 30 percent reduction in lateral velocity and lateral acceleration estimation errors, and the target vehicle 36 is When at a distance of less than 65 meters from the host vehicle 12, constrained filtering reduced errors in excess of 50 percent in lateral position estimation errors and errors in over 90 percent in lateral velocity and lateral acceleration estimation errors. When the target vehicle 36 is far away, the constraint filtering is not improved because of the estimation error of the road curvature parameter, which is proportional to the distance between the host vehicle 12 and the target vehicle 36. A restraint error was generated. This is more apparent in the case of the curved road 34, where the curvature estimation error is larger, which increases the lane position ambiguity of the distant target vehicle 36.

In the third scenario, the host vehicle 12 and the target vehicle 36 are moving on a straight road (C ₀ = 0 and C ₁ = 0), and the target vehicle 36 first approaches in the left neighboring lane. It is in. At t = 2.2 seconds (55 radar scans), the target vehicle 36 begins to deviate from the lane and reroutes toward the host lane 38, thereby colliding at t = 4 seconds (100 radar scans). There has occurred. FIGS. 12a to 12d show the target state estimation results and the lateral position and lateral velocity RMS errors of the unconstrained filtering scheme and the constrained filtering scheme. The error tolerance levels for the constraint validity hypothesis test (Equation (70)) were selected as α≈1 for the host lane 38 and α = 0.5 for all neighboring lanes 40.

  Constraint filtering without validation produces a substantially lower estimation error before the target vehicle 36 changes course, but after the target vehicle 36 begins to change course from that lane (left neighbor lane), The associated target state estimation result is incorrect and its RMS error is much larger than that of unconstrained filtering, which is incorrect after the target vehicle 36 begins to deviate from the lane. Means that it was not released quickly. On the other hand, the performance of constrained filtering with validation is substantially similar to that of unconstrained filtering, producing a slightly lower estimation error before the target vehicle 36 turns away and the target vehicle 36 After starting to deviate from the lane, it shows the target state estimation and RMS error, which is the same as unconstrained filtering, meaning that the road restraint was released quickly.

The fourth scenario is similar to the third scenario, the only difference is that the vehicle is not a straight road but a curved road 34 (C ₀ = −10 ⁻⁵ , C ₁ = −3 × 10 ⁻⁵ ) That was above. The target vehicle 36 begins to depart at t = 2.2 seconds and has a collision at t = 4 seconds. FIGS. 13a-d show the target state estimation results and the lateral position and lateral velocity RMS error for the constrained and unconstrained filtering schemes. The error tolerance level was the same as in the third scenario, and the results and findings were similar to those in the third scenario. The road restraint was quickly removed by the proposed restraint validation after the target vehicle 36 began to depart from the lane. In general, considering that the estimation accuracy of the target vehicle 36 lateral dynamics is often limited by low radar angular resolution, the overall accuracy of the target vehicle 36 lateral dynamics estimation by constraint filtering Improvement was substantial.

  Thus, the simulation results of road vehicle tracking on both straight and curved roads 34 show that when the target vehicle 36 is in the host lane 38, the predictive collision detection system 10 effectively estimates the estimated error in the target vehicle 36 lateral dynamics. It can be reduced. When the target vehicle 36 performs an operation to enter the host lane 38 from a nearby lane, the predictive collision detection system 10 quickly detects this operation and releases the road restraint, otherwise avoids an erroneous restraint result. To do. Considering that the lateral dynamics estimation is often poor when the radar angular resolution is low, the predictive collision detection system 10 substantially improves the estimation accuracy of the target vehicle 38 lateral dynamics, This is beneficial for early and reliable road vehicle collision prediction.

でモデル化でき、ここで、関連する比例定数Ｃ_α―コーナリング剛性とも呼ばれる―は、α＝０におけるスリップ角αに対するコーナリング力Ｆ_ｙの勾配として定義される。 Referring to FIG. 14, according to another aspect, the predictive collision detection system 10 represents a steering angle δ of one or more steered wheels 60 or provides a responsive measure thereto. An angle sensor 58 is further included. For example, referring to FIG. 15, the steering angle δ of a specific steered wheel 60, for example, one front wheel, is an angle between the longitudinal axis 62 of the vehicle 12 and the heading direction 64 of the steered wheel 60. Reference numeral 64 denotes a direction in which the steering wheel 60 rotates. In a turning state, in response to the steered wheel 60 being steered at the steering angle δ, the steered wheel 60 generates a lateral slip when rotating, thereby differing from the heading direction 64 by the associated slip angle α, as a result. The traveling direction 66 is generated. Due to the action between the associated tire and the road, a lateral cone ring force F _y is generated, for example proportional to the slip angle α, which turns the vehicle 12 and this cornering force is: formula

Where the associated proportionality constant C _α , also called cornering stiffness, is defined as the slope of the cornering force F _y with respect to the slip angle α at α = 0.

  In general, for a vehicle 12 having two laterally shifted steering wheels 60, the associated steering angle δ between the different steering wheels 60—inner and outer with respect to the turn—will be different. However, referring to FIG. 16a, for a vehicle 12 traveling at a relatively high longitudinal speed, the turning radius R is substantially larger than the wheel base L of the vehicle 12, in which case different steering wheels 60 are used. It can be assumed that the associated slip angle α is relatively small so that the difference between the slip angles for the inner and outer steered wheels 60 is negligible. Therefore, for the purpose of explaining the cornering behavior, the vehicle 12 is a two-wheeled vehicle comprising one front wheel 63 and one rear wheel 65, each corresponding to a composite of related front wheels or rear wheels of the vehicle 12 ( In this model, different steering wheels 60 at the front or rear of the vehicle are modeled as a single steering wheel 60 that is steered at an associated steering angle α. Each wheel of the motorcycle model 68—the front wheel 63 and the rear wheel 65—is identical to the associated slip angle α, as are all (eg both) corresponding wheels of the actual vehicle 12. It is assumed that a lateral force is generated.

ここで、Ｆ_ｙｆおよびＦ_ｙｒは、それぞれ前輪６３および後輪６５における横力である。重心ＣＧまわりの車両１２のヨー回転加速度は無視できるものと仮定して、前部横力および後部横力によって生じるモーメントの合計はゼロに等しく、その結果として、

となり、ここで、ｂおよびｃは、それぞれ重心ＣＧから前輪６３および後輪６５への距離である。 For a vehicle 12 having a longitudinal velocity U following a curved path having a radius of rotation R, the total lateral force, ie, the cornering force F _y, is: Is equal to the product of

Here, F _yf and F _yr are lateral forces at the front wheel 63 and the rear wheel 65, respectively. Assuming that the yaw rotational acceleration of the vehicle 12 about the center of gravity CG is negligible, the sum of the moments caused by the front and rear side forces is equal to zero, and as a result,

Where b and c are distances from the center of gravity CG to the front wheel 63 and the rear wheel 65, respectively.

ここで、ｂおよびｃは、それぞれ重心ＣＧから前輪６３および後輪６５への距離であり、Ｗ_ｒは、後輪６５によって支えられる車両１２の重量である。したがって、後輪６５における横力Ｆ_ｙｒは、後輪６５によって支えられる車両質量の部分（Ｗ_ｒ／ｇ）と、後輪６５における横加速度との積で与えられる。 Next, the lateral force F _{yr at} the rear wheel 65 is given as follows by substituting Equation (74) into Equation (73).

Here, b and c is the distance to the front wheels 63 and rear wheels 65 from the center of gravity CG, respectively, _{W r} is the weight of the vehicle 12 which is supported by the rear wheels 65. Accordingly, the lateral force F _yr at the rear wheel 65 is given by the product of the vehicle mass portion (W _r / g) supported by the rear wheel 65 and the lateral acceleration at the rear wheel 65.

ここでＷ_ｆは、前輪６３によって支えられる車両１２の重量である。
それぞれ前輪６３および後輪６５における横力Ｆ_ｙｆ、Ｆ_ｙｒが与えられると、関連するスリップ角α_ｆ、α_ｒが、式（７２）、（７５）および（７６）から次のように得られる。

Similarly, the lateral force F _yf at the front wheel 63 is given by the product of the vehicle mass portion (W _f / g) supported by the front wheel 63 and the lateral acceleration at the front wheel 63 as follows.

Here, W _f is the weight of the vehicle 12 supported by the front wheels 63.
_Given the lateral forces F _yf and F _{yr at the} front wheel 63 and the rear wheel 65 respectively, the associated slip angles α _f and α _r are obtained from equations (72), (75) and (76) as follows: .

式（７９）に、式（７７）、（７８）からα_ｆおよびα_ｒを代入すると次式が得られる。

これは、次式のようにも表わされる。

ここで、
δ＝前輪における操舵角（ラジアン）
Ｌ＝ホイールベース（ｍ）
Ｒ＝回転半径（ｍ）
Ｕ＝縦速度（ｍ／ｓｅｃ）
ｇ＝重力加速度定数＝９．８１ｍ／ｓｅｃ^２
Ｗ_ｆ＝フロントアクスル上の荷重（ｋｇ）
Ｗ_ｒ＝リアアクスル上の荷重（ｋｇ）
Ｃ_αｆ＝フロントタイヤのコーナリング剛性（ｋｇ_ｙ／ｒａｄ）
Ｃ_αｒ＝リアタイヤのコーナリング剛性（ｋｇ_ｙ／ｒａｄ）
Ｋ＝アンダーステア勾配（ｒａｄ／ｇ）
ａ_ｙ＝横加速度（ｇ） From the geometric shape shown in FIG. 16b, the steering angle δ is given by:

Substituting α _f and α _r from equations (77) and (78) into equation (79) yields the following equation:

This is also expressed as:

here,
δ = Steering angle at the front wheels (radians)
L = Wheelbase (m)
R = turning radius (m)
U = Vertical speed (m / sec)
g = gravity acceleration constant = 9.81 m / sec ²
W _f = Load on front axle (kg)
W _r = Load on rear axle (kg)
C _αf = cornering rigidity of front tire (kg _y / rad)
C _αr = Rear tire cornering stiffness (kg _y / rad)
K = understeer gradient (rad / g)
a _y = lateral acceleration (g)

Equations (80) and (81) describe the relationship between the steering angle δ and the lateral acceleration a _y = U ² / (gR). The coefficient K = [W _f / C _αf −W _r / C _αr ] _—which represents the sensitivity of the steering angle α to the lateral acceleration _ay and is also referred to as an understeer gradient—is composed of two terms, each term being a wheel It is the ratio between the upper loads W _f , W _r (front or rear) and the corresponding cornering stiffness C _αf , C _αr of the associated tire. Depending on the value of the understeer slope K, the cornering behavior of the vehicle 12 is either neutral steer, understeer or oversteer depending on whether K is zero, greater than zero or less than zero. being classified.

したがって、一定半径旋回に対して、縦速度が変化するときに操舵角δに変化はない。
アンダーステアを示す車両１２に対して、

したがって、一定半径旋回に対して、縦速度Ｕが増大すると、アンダーステア勾配Ｋと横加速度ａ_ｙの積に比例して、操舵角αを増大させる必要がある。 For vehicle 12 showing neutral steer,

Therefore, the steering angle δ does not change when the vertical speed changes for a constant radius turn.
For vehicle 12 showing understeer,

Therefore, when the vertical speed U increases for a constant radius turn, it is necessary to increase the steering angle α in proportion to the product of the understeer gradient K and the lateral acceleration _ay .

したがって、一定半径旋回に対して、縦速度Ｕが増加すると、アンダーステア勾配Ｋと横加速度ａｙとの積に比例して、操舵角αを減少させる必要があることになる。
操舵角αで操舵される車両１２は、ヨーレートωを発生し、このヨーレートは、縦速度Ｕおよび回転半径Ｒと次式で関係づけられる。

For vehicle 12 showing oversteer,

Therefore, when the vertical speed U increases with respect to a constant radius turn, it is necessary to decrease the steering angle α in proportion to the product of the understeer gradient K and the lateral acceleration ay.
The vehicle 12 steered at the steering angle α generates a yaw rate ω, and this yaw rate is related to the vertical speed U and the rotation radius R by the following equation.

これを使用して、例えば車両１２はニュートラルステア挙動を示すと仮定して、関連する誤差分散間の関係を求めることができる。例えば、ニュートラルステアの場合、Ｋ＝０であり、したがって式（８４）は、

When solving for the radius of rotation R from equation (79) and substituting into equation (83), the following relationship is obtained between yaw rate ω and steering angle δ.

Using this, for example, assuming that the vehicle 12 exhibits neutral steer behavior, the relationship between the associated error variances can be determined. For example, for neutral steer, K = 0, so equation (84) is

縦速度Ｕおよび操舵角αが独立であると仮定すると、

The error variance of ω is given by

Assuming that the vertical velocity U and the steering angle α are independent,

これから、式（８７）に代入すると次式となり、

ここで、σ_Ｕおよびσ_δは、縦速度Ｕおよび操舵角δの誤差分散である。 For neutral steer conditions, from equation (85):

From this, substituting into equation (87) gives

Here, σ _U and σ _δ are error variances of the vertical speed U and the steering angle δ.

これから、曲率誤差分散

と、操舵角誤差分散

との関係は、次式で与えられる。

For a constant turning radius R, from equation (2), C = C ₀ and from equations (13), (88), for neutral steer conditions,

From now on, curvature error variance

And steering angle error variance

Is given by the following equation.

  The steering angle sensor 58 can be implemented in a variety of ways, including but not limited to, adapted to measure the rotation of the steering shaft, or input to the steering box, such as the pinion of the rack and pinion steering box, Angular position sensors—for example, shaft encoders, rotary potentiometers or rotary transformers / synchronizers—or linear position sensors adapted to measure the rack position of a rack and pinion steering box. The steering angle sensor 58 can also be shared with another vehicle control system, such as a road following control system or a suspension control system. The steering angle sensor 58 can be used to complement the yaw rate sensor 16 and can beneficially provide independent information regarding vehicle operation. In addition, the gyroscope yaw rate sensor 16 is more accurate and sensitive to vehicle operation than the steering angle sensor 58 when each is used to generate a measure of yaw angle. The angle δ measurement error is substantially independent of the longitudinal speed U compared to the gyroscope yaw rate sensor 16 where the associated yaw rate ω measurement error is related to the vehicle speed.

ここで、ωは真のヨーレート、ω_ｍはヨーレート計測値、ｂはドリフトを含むジャイロバイアス、ｂ_ｍは平均ジャイロバイアスである。 The curvature error variance associated with the steering angle δ measurement can be compared to that associated with the yaw rate ω to identify conditions under which one measurement is more accurate than the other. The error variance of the yaw rate ω measured by the gyroscope yaw rate sensor 16 is given as follows.

Here, ω is a true yaw rate, ω _m is a yaw rate measurement value, b is a gyro bias including drift, and b _m is an average gyro bias.

は、以下に説明する式（９７）によって与えられる。式（９１）および式（９７）を等式化し、式（９４）から

を代入することによって、操舵角δ計測値に関連する曲率誤差分散は、ヨーレートω計測値に関連する曲率誤差分散と、以下の条件において等しくなる。

Curvature error variance of yaw rate ω

Is given by equation (97) described below. Equations (91) and (97) are equalized and from Equation (94)

, The curvature error variance related to the steering angle δ measurement value becomes equal to the curvature error variance related to the yaw rate ω measurement value under the following conditions.

、ｂｍ＝２．５９２６、Ｌ＝３．２メートルである―を定義しており、このスイッチング曲線は、一態様において、道路曲率パラメータを求める場合に、操舵角δまたはヨーレートωのいずれを使用するかを決定するのに使用することができる。例えば、図１８を参照すると、ステップ（５０２）において、車両１２の縦速度Ｕは速度センサ１８から読み取られる。次いで、ステップ（１８０２）において、縦速度Ｕが速度閾値Ｕ^Ｔよりも大きい場合には、道路曲率パラメータはヨーレートωを用いて求められ、ここで速度閾値Ｕ^Ｔパラメータは式（９５）によって与えられ、図１７に操舵角δ計測値の誤差分散

の関数として示してあり、その後者は所与の操舵角センサ５８に対して一定であると仮定される。より詳細には、ステップ（１８０２）から、車両１２のヨーレートωが、ヨーレートセンサ１６から読み取られ、ステップ（５０６）において、道路曲率パラメータＣ_０、Ｃ_１が、（Ｕ，ω）から上述のように推定される。 Equation (95) is a switching curve—for example, as shown in FIG.

, Bm = 2.5926, L = 3.2 meters—this switching curve, in one aspect, uses either the steering angle δ or the yaw rate ω when determining the road curvature parameter. Can be used to determine. For example, referring to FIG. 18, the longitudinal speed U of the vehicle 12 is read from the speed sensor 18 in step (502). Then, in step 1802, if the vertical velocity U is greater than the speed threshold U ^T is the road curvature parameters determined using a yaw rate omega, where speed threshold U ^T parameter is given by equation (95) FIG. 17 shows the error variance of the measured steering angle δ.

The latter is assumed to be constant for a given steering angle sensor 58. More specifically, from step (1802), the yaw rate ω of the vehicle 12 is read from the yaw rate sensor 16, and in step (506), the road curvature parameters C ₀ and C ₁ are as described above from (U, ω). Is estimated.

Rather, from the case longitudinal velocity U of the vehicle 12 is less than the speed threshold ^{U T} step (1802), in step (1804), the steering angle δ is read from the steering angle sensor 58, then, step ( 1806), road curvature parameters C ₀ , C ₁ are estimated from (U, ω), where the yaw rate ω measurement value input to the first Kalman filter 52 (host state filter) is obtained using equation (84). It can be obtained from the steering angle δ and the longitudinal speed U. If the vertical velocity U is equal to the speed threshold ^{U T,} the step (506) and the estimated value of road curvature parameter _C 0, _{C 1} from step (1806) will have a same error variance, any An estimate can also be used.

は、実質的にほとんどの場合に、実質的にＵよりも小さいので、Ｕは非確率（non-random）変数と仮定することができる。 The error variance and covariance of the road curvature parameters C ₀ and C ₁ used by the associated second Kalman filter 54 of the road curvature estimation subsystem 42, ie the curvature filter, generally depends on the amount of 1 / U, Here, U is the vertical speed of the vehicle 12. No analytical solution is currently known for the exact mean and variance of 1 / U, where U is a Gaussian random variable. Instead, the distribution of U

Is substantially less than U in most cases, so U can be assumed to be a non-random variable.

Therefore, various items of variance and covariance of road curvature parameters C ₀ and C ₁ can be derived as follows.

を求める。例えば、速度センサ１８は、車両１２の縦速度

を車両速度の測度として提供し、ヨーレートセンサ１６または操舵角センサ５８のいずれか、または両方は、ヨーレート

または操舵角

のいずれか、または両方を車両ヨーの測度として提供し、ここで計測値のサンプルｋは、対応するサンプリング時間における、サンプリングデータシステムによって提供される。例えば、やはり図４に示してある一態様において、車両ヨーの測度は、ヨーレートセンサ１６からのヨーレート

によって与えられ、ここでヨーレート

および縦速度

は、ホスト状態フィルタ５２．１の第１のカルマンフィルタ５２に直接、入力される。 Referring to FIG. 19, the road curvature estimation subsystem 42 can be implemented in various ways. In general, the road curvature estimation subsystem 42 includes a host state filter 52.1 and a curvature filter 54.1 that processes measures responsive to vehicle speed and vehicle yaw to Corresponding host status

Ask for. For example, the speed sensor 18 is used for the vertical speed of the vehicle 12.

As a measure of vehicle speed, either the yaw rate sensor 16 or the steering angle sensor 58, or both,

Or steering angle

Either or both are provided as a measure of vehicle yaw, where a sample k of measurements is provided by a sampling data system at a corresponding sampling time. For example, in one aspect also shown in FIG. 4, the measure of vehicle yaw is the yaw rate from yaw rate sensor 16.

Given by and here yaw rate

And vertical speed

Is directly input to the first Kalman filter 52 of the host state filter 52.1.

の絶対値に応じて、ヨーレートセンサ１６からのヨーレート

または操舵角センサ５８からの操舵角

のいずれかによって与えられる。車両１２の縦速度Ｕが、速度閾値Ｕ^Ｔより小さい場合には、ヨーレートプロセッサ６８―例えば、信号プロセッサ２６内に具現化される―は、第１のカルマンフィルタ５２への入力のための、ヨーレート

を、例えば式（８５）および縦速度

を使用して、操舵角

から計算する。 In another aspect, the vehicle yaw measure is determined according to the process illustrated in FIG.

According to the absolute value of the yaw rate from the yaw rate sensor 16

Or the steering angle from the steering angle sensor 58

Given by either. Longitudinal velocity U of the vehicle 12, when a smaller speed threshold U ^T is the yaw rate processor 68- example, are embodied in the signal processor 26 - is for the input to the first Kalman filter 52, the yaw rate

For example, equation (85) and longitudinal speed

Use the steering angle

Calculate from

が第１のカルマンフィルタ５２に入力される。さらに別の態様においては、操舵角センサ５８およびヨーレートプロセッサ６８が、ヨーレートセンサ１６の便益なしに、使用される。さらに別の態様においては、操舵角センサ５８からの操舵角

が第１のカルマンフィルタ５２に直接、入力される。さらに別の態様においては、車両１２の縦速度Ｕが、速度閾値Ｕ^Ｔよりも小さい場合には、操舵角５８センサ５８からの操舵角

は、第１のカルマンフィルタ５２に直接、入力され、この第１のカルマンフィルタは、操舵角

を関連する状態変数として使用するように適合されている。また、車両１２の縦速度Ｕが速度閾値Ｕ^Ｔ以上である場合には、ヨーレートセンサ１６からのヨーレート

は第１のカルマンフィルタ５２に入力され、この第１のカルマンフィルタは、ヨーレート

を関連する状態変数として使用するように適合されている。 Otherwise, if 12 vertical velocity U of the vehicle is greater than the speed threshold U ^T is the yaw rate from the yaw rate sensor 16

Is input to the first Kalman filter 52. In yet another aspect, steering angle sensor 58 and yaw rate processor 68 are used without the benefit of yaw rate sensor 16. In yet another aspect, the steering angle from the steering angle sensor 58 is

Is directly input to the first Kalman filter 52. In yet another embodiment, if the longitudinal velocity U of the vehicle 12 is less than the speed threshold U ^T is the steering angle from the steering angle 58 sensor 58

Is directly input to the first Kalman filter 52, and the first Kalman filter has a steering angle.

Is adapted to be used as an associated state variable. Further, when the vertical velocity U of the vehicle 12 is equal to or higher than the speed threshold U ^T is the yaw rate from the yaw rate sensor 16

Is input to the first Kalman filter 52, which is the yaw rate.

Is adapted to be used as an associated state variable.

およびその関連する共分散マトリックス

を含む―に変換し、その第２のカルマンフィルタの出力は、道路曲率推定サブシステム４２の出力として使用されるか、またはそれは、第２の曲率プロセッサ７４を使用して、道路曲率パラメータＣ_０、Ｃ_１およびその関連する共分散に変換される。例えば、第１の曲率プロセッサ７２および第２の曲率プロセッサ７４ならびに曲率推定器７０のホスト状態フィルタ５２．１は、信号プロセッサ２６内に具現することができる。 In general, the associated state and variance outputs of host state filter 52.1 are processed by curvature estimator 70 to obtain estimates of road curvature parameters C ₀ , C ₁ and the associated error covariance. In general, the curvature estimator 70 includes a first curvature processor 72 that computes the associated state and covariance output of the host state filter 52.1 as road curvature parameters C ₀ , C _1. Or other relevant configuration-measurement vector that is used directly as output of the road curvature estimation subsystem 42 or input to the second Kalman filter 54 of the curvature filter 54.1

And its associated covariance matrix

And the output of the second Kalman filter is used as the output of the road curvature estimation subsystem 42 or it uses the second curvature processor 74 to determine the road curvature parameter C ₀ , Converted to C ₁ and its associated covariance. For example, the first curvature processor 72 and the second curvature processor 74 and the host state filter 52.1 of the curvature estimator 70 can be implemented in the signal processor 26.

として第２のカルマンフィルタ５４へ入力するために、ホスト状態

から道路曲率パラメータＣ_０、Ｃ_１を計算する。同様に、第１の曲率プロセッサ７２は、例えば、式（２１）、（２２）に従って、ホスト状態ベクトルの共分散

から計測値ベクトルの関連する共分散

を計算する。 According to the first aspect, the curvature estimator 70 includes a first curvature processor 72 and a second Kalman filter 54, and the first curvature processor 72 is a measured value vector, for example, according to equation (21).

As the host state to input to the second Kalman filter 54

To calculate road curvature parameters C ₀ and C ₁ . Similarly, the first curvature processor 72 may calculate the covariance of the host state vector according to, for example, equations (21) and (22)

To the associated covariance of the measurement vector

Calculate

ここで、ｑ＝６×１０^−７、Ｔ_ｋはサンプリング時間間隔であり、関連するＲマトリックスの分散および共分散要素は、式（９７）、（１０２）、（１０９）によって与えられる。次いで、道路曲率推定サブシステム４２の出力は、第２のカルマンフィルタ５４の出力によって与えられる。また、曲率推定器７０の第１の態様を図４に示してあり、第１の曲率プロセッサ７２の動作は、その第１のカルマンフィルタ５２と第２のカルマンフィルタ５４の間の相互接続において暗黙的である。 An associated second Kalman filter 54 is shown in FIG. 20, and the associated vector and matrix referenced in the appendix are given by:

Where q = 6 × 10 ⁻⁷ , T _k is the sampling time interval, and the associated R matrix variance and covariance elements are given by equations (97), (102), (109). The output of the road curvature estimation subsystem 42 is then given by the output of the second Kalman filter 54. Also, a first aspect of the curvature estimator 70 is shown in FIG. 4, and the operation of the first curvature processor 72 is implicit in the interconnection between the first Kalman filter 52 and the second Kalman filter 54. is there.

ここでＬはスライドウィンドの長さ、

であり、またｑ＝２×１０^−７である。関連するＲマトリックスの分散および共分散は、式（９７）、（１０２）、（１０９）によって与えられる。 The second aspect of curvature estimator 70 is a modification of the first aspect, in which case second Kalman filter 54 is adapted to incorporate a sliding window in the associated filtering process. The length of the sliding window is adapted to avoid excessive delays due to the wind process, for example, in one aspect, includes about 5 samples. The associated vector and matrix of the associated second Kalman filter 54—referred to in the appendix—are given by:

Where L is the length of the sliding window,

And q = 2 × 10 ⁻⁷ . The dispersion and covariance of the associated R matrix is given by equations (97), (102), (109).

に従って、道路曲率パラメータＣ_０、Ｃ_１に応答性を有するように適合させることができる。このルールによって、道路の直線部分に対応して、Ｃ_０およびＣ_１の両方が比較的小さい場合に、より大きいウィンド長さ―例えば、２５サンプルの大きさ―が与えられる。ウィンド長さＬは、道路の曲線部または移行部に対応して、Ｃ_０またはＣ_１のいずれかが大きい場合に、小さくなる。さらに、急激な車両の操作に対応するために、ウィンド長さＬの後続の増加を１ステップ当たり１サンプルに限定することにより、操作が終了するときに、先行サンプルが曲率推定器７０からの出力に悪影響を与えないようにして、ウィンド長さＬを急激に減少させることができる。ウィンド長さＬが変化すると、第２のカルマンフィルタ５４内の関連するＦ、Ｑ、およびＲのマトリックスも変更される。 The third aspect of the curvature estimator 70 is a modified form of the second aspect, and the length L of the slide window is adaptive. For example, the window length is, for example, the following rule:

Thus, the road curvature parameters C ₀ and C ₁ can be adapted to be responsive. This rule gives a larger window length—for example, a size of 25 samples—when both C ₀ and C ₁ are relatively small, corresponding to the straight part of the road. The window length L becomes small when either C ₀ or C ₁ is large corresponding to the curve or transition portion of the road. Further, by limiting the subsequent increase in the window length L to one sample per step to accommodate sudden vehicle operations, the preceding sample is output from the curvature estimator 70 when the operation ends. The window length L can be rapidly reduced without adversely affecting the window. As the window length L changes, the associated F, Q, and R matrix in the second Kalman filter 54 is also changed.

として入力するために、ホスト状態

から道路曲率パラメータＣ_０および

を計算し、第２の曲率プロセッサ７４は、第２のカルマンフィルタ５４の出力を、曲率推定器７０の曲率推定値としてＣ_０および

に変換する。関連する第２のカルマンフィルタ５４を図２１に示してあり、付録において参照されている、関連するベクトルおよびマトリックスは、次式で与えられ、

ここでｑ＝０．０１、Ｔ_ｋはサンプリング時間間隔であり、関連するＲマトリックスの分散要素および共分散要素は、式（９７）、（１０６）、（１１２）によって与えられる。 According to the fourth aspect, the curvature estimator 70 includes a first curvature processor 72, a second Kalman filter 54, and a second curvature processor 74, wherein the first curvature processor 72 is a second Kalman filter 54. Measured value vector

Host state to enter as

To road curvature parameter C ₀ and

The second curvature processor 74 uses the output of the second Kalman filter 54 as C ₀ and the curvature estimate of the curvature estimator 70.

Convert to The associated second Kalman filter 54 is shown in FIG. 21 and the associated vector and matrix referenced in the appendix are given by:

Where q = 0.01, T _k is the sampling time interval, and the associated dispersion and covariance elements of the R matrix are given by equations (97), (106), (112).

ここで、Ｌはスライドウィンド長さであり、

であって、ｑ＝４×１０^−４である。関連するＲマトリックスの分散および共分散は、式（９７）、（１０６）、（１１２）によって与えられる。 The fifth aspect of the curvature estimator 70 is a modification of the fourth aspect, in which the second Kalman filter 54 is adapted to incorporate a sliding window into the associated filtering process. The length of the sliding window is adapted to avoid excessive delays caused by the wind process, for example, in one aspect, includes about 5 samples. The associated vector and matrix of the associated second Kalman filter 54 —referred to in the appendix—are given by:

Where L is the sliding window length,

And q = 4 × 10 ⁻⁴ . The dispersion and covariance of the associated R matrix is given by equations (97), (106), (112).

The sixth aspect of the curvature estimator 70 is a modified form of the fifth aspect, and the length L of the slide window is adaptive. For example, the window length can be adapted to be responsive to the road curvature parameters C ₀ , C ₁ , for example, according to the rules of equation (117). This rule results in a larger window length L—for example, a size of 25 samples—when both C ₀ and C ₁ are relatively small, for example corresponding to a straight section of the road. The window length L decreases when either C ₀ or C ₁ is large corresponding to the curve or transition of the road—for example, the size of one sample. Further, by limiting the subsequent increase in the window length L to one sample per step to accommodate a sudden vehicle operation, the preceding sample is output to the curvature estimator 70 when the operation ends. The window length L can be rapidly reduced without adversely affecting the window. As the window length L changes, the associated F, Q, and R matrix in the second Kalman filter 54 is also changed.

から道路曲率パラメータＣ_０、Ｃ_１を計算する。
第８の態様によれば、曲率推定器７０は、第１の曲率プロセッサ７２を含み、この第１の曲率プロセッサは、ホスト状態フィルタ５２．１からのホスト状態

の軌跡のカーブフィットによって、クロソイドモデルの道路曲率パラメータＣ_０、Ｃ_１を求める。ホスト車両１２の位置、速度および加速度の各成分は、以下のように計算される。

According to a seventh aspect, the curvature estimator 70 includes a first curvature processor 72, which does not use the second Kalman filter 54 as an output of the road curvature estimation subsystem 42. , Host status

To calculate road curvature parameters C ₀ and C ₁ .
According to an eighth aspect, the curvature estimator 70 includes a first curvature processor 72, which is the host state from the host state filter 52.1.

The road curvature parameters C ₀ and C ₁ of the clothoid model are obtained by the curve fitting of the trajectory. The position, velocity and acceleration components of the host vehicle 12 are calculated as follows.

式（１２２）から（１２９）までを使用して、ｘ_ｋ、ｙ_ｋおよびそれらの微分を求めた後に、式（１２９）から（１３１）を使用して、カーブフィットによって道路曲線パラメータＣ_０、Ｃ_１について解を求め、この場合に、サンプリングデータポイント―例えば、一態様においては１２サンプルポイント―を使用してカーブフィットに使用するための関連するカーブの平滑さを向上させる。 Then, from the clothoid model and equation (8):

After obtaining x _k , y _k and their derivatives using equations (122) through (129), using equations (129) through (131), the road curve parameters C ₀ , A solution is determined for C ₁ , in which case sampling data points—for example, 12 sample points in one aspect—are used to improve the smoothness of the associated curve for use in curve fitting.

この規則によって、Ｃ_０およびＣ_１の両方が、例えば、道路の直線区間に対応して、比較的小さい場合に、より大きなウィンド長さＬ―例えば、２５サンプルの大きさ―が得られる。ウィンド長さＬは、道路の曲線部または移行部に対応してＣ_０またはＣ_１のいずれかが大きい場合に、小さくなる―例えば２サンプルの大きさになる。さらに、急激な車両の操作に対応するために、ウィンド長さＬの後続の増加を１ステップ当たり１サンプルに限定することにより、操作が終了するときに、先行サンプルが曲率推定器７０からの出力に悪影響を与えないようにして、ウィンド長さＬを急激に減少させることができる。 The ninth aspect of the curvature estimator 70 is a modification of the eighth aspect, where the length L of the sliding window is adaptive. For example, the window length can be adapted to respond to road curvature parameters C ₀ , C ₁ , for example, according to the following equation:

This rule results in a larger window length L—for example, a size of 25 samples—when both C ₀ and C ₁ are relatively small, for example corresponding to a straight section of the road. The window length L decreases when either C ₀ or C ₁ is large corresponding to the curve or transition of the road—for example, 2 samples. Further, by limiting the subsequent increase in the window length L to one sample per step to accommodate sudden vehicle operations, the preceding sample is output from the curvature estimator 70 when the operation ends. The window length L can be rapidly reduced without adversely affecting the window.

The above first to ninth aspects of the road curvature estimation subsystem 42 are based on a road curvature clothoid model, where the road curvature C varies linearly with respect to the path length along the road. And different types of roads (eg, straight, circular or generally curved) are represented by different values of clothoid road curvature parameters C ₀ , C ₁ . The clothoid model results in a simpler form for straight (C ₀ = C ₁ = 0) and circular (C ₁ = 0) road sections. Different aspects of the road curvature estimation subsystem 42 can be used under different conditions. For example, in one aspect of the predictive collision detection system 10 in which the sampling rate of the yaw rate sensor 16 is relatively low, the seventh aspect of the curvature estimator 70 is that the longitudinal speed U of the host vehicle 12 is more than a threshold, for example, about 11 m / sec. And the ninth aspect of curvature estimator 70 is used at higher speeds. The ratio of average prediction error to average prediction distance can be used to compare and evaluate various aspects of the curvature estimator 70.

に対応して、Ｃ＝Ｃ_０となる。したがって、道路は、多重モデルシステム８２によって表わされ、この場合には、特定の道路区間は、有限の数ｒのモデルの１つによって特徴づけられる。例えば、図２３において、多重モデルシステム８２には、ｒ＝３モデルが組み込まれて、それぞれのモデルは、別個の対応する曲率推定器７０．１、７０．２、７０．３内に具現される。 In general, a high-speed road can be modeled as a set of different types of interconnected road sections, each represented by a different road model. For example, FIG. 22 shows that the first road segment 76 of a straight line having a straight route—represented by C = 0—has a third-order route—represented by a clothoid model C = C ₀ + C ₁ x— It is connected to a second road section 78 and is further connected to a third road section 80 having a quadratic curve path—represented by C = C ₀ .
Referring to FIG. 23, according to the tenth aspect of the road curvature estimation subsystem 42, different types of roads are represented by different models, rather than using a single generic clothoid model, whereby Improved accuracy of estimation for road segments characterized by models with fewer degrees of freedom, obtained by constraining one or more coefficients of the clothoid model for less degrees of freedom . For example, for a straight road section 76, the clothoid model corresponds to a route equation of y = 0, C = 0-> C ₀ = C ₁ = 0, and for a quadratic curve road section 80, The clothoid model is a path equation

In response to, the _C = C _0. Thus, the road is represented by a multiple model system 82, where a particular road segment is characterized by one of a finite number r of models. For example, in FIG. 23, the multiple model system 82 incorporates r = 3 models, each model embodied in a separate corresponding curvature estimator 70.1, 70.2, 70.3. .

  Each curvature estimator 70.1, 70.2, 70.3 is generally constructed as shown in FIG. 19 and is adapted to process the output of the host state filter 52.1. In FIG. 23, a common host state filter 52.1 is shown for all of the curvature estimators 70.1, 70.2, 70.3, but different curvature estimators 70.1, 70.2, 70. .3 can also utilize different aspects of the corresponding host state filter 52.1, for example, only one yaw rate sensor 16 is used in one aspect of the host state filter 52.1, and in another aspect, the yaw rate sensor 16 And a steering angle sensor 58 are used. For example, the first curvature estimator 70.1 incorporates a straight road model, and the second curvature estimator 70.2 incorporates a circular arc or quadratic curve road model to provide a third curvature estimation. The vessel 70.3 incorporates a clothoid road model suitable for general high-speed roads.

円形アークまたは２次曲線道路モデルは、以下の特徴がある。

ここで、Ｔ_ｋはサンプリング周期、

は推定ホスト速度であり、ｑ＝０．０００５である。 More specifically, the straight road model has the following characteristics.

A circular arc or quadratic curve road model has the following characteristics.

Where T _k is the sampling period,

Is the estimated host speed, q = 0.0005.

ここで、Ｔ_ｋはサンプリング周期であり、

は推定ホスト速度であり、ｑ＝０．００２５である。
多重モデルシステム８２は、連続（ノイズ）不確定性ならびに不連続（「モデル」または「モード」）不確定性の両方を有し、そのためにハイブリッドシステムと呼ばれる。多重モデルシステム８２は、ベース状態モデル、モード状態、およびモードジャンププロセスによって特徴づけられると仮定される。 The clothoid road model has the following characteristics:

Where T _k is the sampling period,

Is the estimated host speed, q = 0.005.
Multiple model system 82 has both continuous (noise) uncertainty as well as discontinuous ("model" or "mode") uncertainty and is therefore referred to as a hybrid system. The multi-model system 82 is assumed to be characterized by a base state model, mode state, and mode jump process.

ここで、Ｍ（ｋ）は、ｋで終了するサンプリング周期中に有効である、時間ｋにおけるモードを表わす。
モード状態、またはモードは、ｒ個の可能性のあるモードの１つと仮定され、

ここで、システムの構造および／または関連するノイズ成分の統計は、以下のように、異なるモードに対して異なる可能性がある。

１つのモードから別のモードへの移行を支配する、モードジャンププロセスは、以下のように、既知の移行確率を有するマルコフ連鎖によって特徴づけられると仮定される。

The base state model is assumed to be characterized as follows:

Here, M (k) represents the mode at time k that is valid during the sampling period ending with k.
The mode state, or mode, is assumed to be one of r possible modes,

Here, the structure of the system and / or the associated noise component statistics may be different for different modes, as follows.

The mode jump process, which governs the transition from one mode to another, is assumed to be characterized by a Markov chain with a known transition probability as follows:

  Curvature estimators 70.1, 70.2, 70.3 operate in parallel, and the output therefrom is operative with a curvature processor 84—which can be implemented, for example, in signal processor 26—. Combined, the curvature processor generates a single estimate of road curvature and associated covariance according to an interacting multiple model algorithm 2400 (IMM). In general, the interactive multiple model algorithm 2400 is useful for tracking one or both of maneuvering targets and / or non-maneuvering targets with moderate computational complexity, where the operations are: Modeled as a switching of the target state model governed by the underlying Markov chain. Different state models can have different structures, and the associated process noise statistics for different state models can be different. The interactive multiple model algorithm 2400 operates in the same manner as an exact Bayesian filter, but requires substantially less computational power. Each model has a corresponding filter that is processed by the curvature processor 84 according to an interactive multiple model algorithm.

Referring to FIG. 24, the interaction multiple model algorithm 2400 is started in step (2402) with the initialization of each mode conditioned filter in the current cycle, and the mode condition estimate and the previous cycle covariance Are mixed using the mixing probability. Each filter uses a mixture estimate at the start of each cycle, and the mixture is determined by the probability of switching between models. Each model, i.e. j = 1,. . . , R, the initial estimate and covariance of filter j are given by

および共分散

を得る。
次いで、ステップ（２４０６）において、それぞれのモードに対する、伝播されたモード条件推定値および共分散が結合されて、以下が得られる。

Then, in step (2404), the mode condition state is determined for each model, i.e. j = 1,. . . , R are propagated by the Kalman filter matched to the j-th mode M _j (k), and the state at time k

And covariance

Get.
Then, in step (2406), the propagated mode condition estimates and covariances for each mode are combined to obtain:

および共分散

を与え、それによってフィルタｊに対応する尤度関数が次式で得られる。

Then, in step (2408), for each of the r parallel filters, state estimates and covariances are calculated, conditioned on valid modes, and conditioned on the corresponding mode likelihood function. The Kalman filter matched to the j th mode, M _j (k) uses the measured value z (k) to

And covariance

Thus, the likelihood function corresponding to the filter j is obtained by the following equation.

次いで、モード確率が、各モード、すなわちｊ＝１，．．．，ｒに対して、以下のように更新される。

Then, in step (2410), the model probabilities μ _j (k) are determined for each mode, ie j = 1,. . . , R are updated in parallel to obtain a likelihood that each model is correct. The mixing probability is calculated for all combinations of (i, j) for (i, j = 1, ..., r) as follows:

The mode probability is then determined for each mode, i.e. j = 1,. . . , R are updated as follows.

Then, in step (2412), the overall state estimate and the covariance—the output of the interaction multiple model algorithm 2400—are calculated by combining the model condition state estimate and the covariance as follows:

ここで、

はホストフィルタからの状態誤差共分散マトリックスであり、Ｊ_ＣＸは次式で与えられるヤコビアンマトリックスである。

For each of the three related mode condition Kalman filters, the measured value and its noise covariance used as input to the interactive multiple model algorithm 2400 curvature filter are given by:

here,

Is a state error covariance matrix from the host filter, and J _CX is a Jacobian matrix given by the following equation.

The Markov model is realized by assuming that there is a probability p _ij that the target will transition from mode state i to state j at each scan time. It is assumed that these probabilities are known in advance and can be represented, for example, as a model probability transition matrix as follows.

例えば、関連する誤差共分散

を有する、

を提供し、ここで、ｘおよびｙは車両の世界絶対座標、例えば、世界測地システムＷＧＳ（world geodetic system）の緯度と経度である。車両ナビゲーションシステム８６は、また、標高および時間情報、および／または計測値の関連する速度を提供することもできる。 With reference to FIGS. 1 and 25, according to another aspect of the road curvature estimation subsystem 42 ′, the predictive collision detection system 10 includes a vehicle navigation system 86 and associated map operatively coupled to the signal processor 26. A system 88 is further included. For example, the vehicle navigation system 86 includes a GPS navigation system that includes at least a quadratic curve vehicle position measure that indicates a current vehicle position on a road surface.

For example, the associated error covariance

Having

Where x and y are the world's absolute coordinates of the vehicle, for example, the latitude and longitude of the world geodetic system (WGS). The vehicle navigation system 86 may also provide elevation and time information and / or associated speed of measurements.

は、マップシステム８８と一緒に使用されて、ホスト車両１２に対する道路の位置および曲率座標を特定し、ここでマップシステム８８には、絶対座標系におけるディジタルマップデータベースと、ホスト車両１２がその上に位置する道路の―世界絶対座標における―車両位置測度

を、上記の道路曲率およびターゲット状態推定に使用された座標系における、ホスト絶対座標に変換するためのアルゴリズムとが組み込まれている。したがって、マップシステム８８は、以下の変換を行い、

ここで、（ｘ，ｙ）は、車両ナビゲーションシステム８６からの車両位置測度

の世界絶対座標であり、

は、［ｘ，ｙ］に最も近い道路の中心の座標を包含するベクトルであり、

は、ベクトル

における道路中心点座標に対応する曲率パラメータを包含する配列である。 Vehicle position measure

Is used in conjunction with the map system 88 to identify the location and curvature coordinates of the road relative to the host vehicle 12, where the map system 88 includes a digital map database in an absolute coordinate system and the host vehicle 12 thereon. Vehicle position measure of the road that is located-in world absolute coordinates-

Is incorporated into the host absolute coordinates in the coordinate system used for the road curvature and target state estimation described above. Therefore, the map system 88 performs the following conversion:

Where (x, y) is the vehicle position measure from the vehicle navigation system 86

World absolute coordinates,

Is a vector containing the coordinates of the center of the road closest to [x, y]

Is a vector

Is an array including curvature parameters corresponding to the road center point coordinates.

は、道路の中心上のポイントを表わし、

は、そのポイントにおける道路の曲率パラメータを表わす。

の誤差共分散は、

であり、

の誤差共分散は、関連するマップデータにおけるノイズまたは誤差を表わす

によって与えられる。マップシステム８８は、道路位置座標および関連する曲率パラメータ情報の両方を記憶するか、またはその情報が必要なときに、記憶された道路中心の位置座標から曲率パラメータを計算することができる。車両ナビゲーションシステム８６からのホスト車両１２位置と、ホストフィルタ５２．１から、または車両ナビゲーションシステム８６から、あるいはその両方からの情報に基づくホスト車両１２のヘディングが与えられると、世界絶対座標は、並進（translation）と回転の組合せによって、ホスト車両絶対座標に変換することができる。 Therefore,

Represents a point on the center of the road,

Represents the curvature parameter of the road at that point.

The error covariance of is

And

The error covariance of represents the noise or error in the associated map data

Given by. The map system 88 can store both road position coordinates and associated curvature parameter information, or calculate curvature parameters from the stored road center position coordinates when that information is needed. Given the host vehicle 12 position from the vehicle navigation system 86 and the heading of the host vehicle 12 based on information from the host filter 52.1 and / or the vehicle navigation system 86, the world absolute coordinates are translated. (Translation) and rotation can be converted into absolute coordinates of the host vehicle.

が与えられると、一態様においては、マップシステム８８は、関連するマップデータベースを使用して、以下の選択基準

を満足する関連するマップデータベース内の道路を発見することによって、ホスト車両１２が存在する可能性が最も高い道路を特定し、ここで、Ｔは選択閾値、

は、車両位置測度

に最も近い道路上の点である。２つ以上の道路が選択基準を満足する場合には、別の道路曲率推定システム４２によって推定された曲率

とマップシステム８８のマップデータベースから予期される道路それぞれの曲率

とを比較することによって、最も可能性の高い道路が選択されるとともに、車両位置測度

にもっと近い点の曲率

が、他方の曲率推定システム４２からの推定曲率

に最も近い、マープデータベースからの道路が、マップデータベースからの最も可能性の高い道路として選択され、その最も近い点における関連する曲率は、以下のように与えられる。

More specifically, vehicle position measures

In one aspect, the map system 88 uses the associated map database to select the following selection criteria:

To identify the road where the host vehicle 12 is most likely to be present, where T is the selection threshold,

Is a vehicle position measure

Is the closest point on the road. If two or more roads meet the selection criteria, the curvature estimated by another road curvature estimation system 42

And the curvature of each road expected from the map database of the map system 88

The most likely road is selected and the vehicle location measure

Curvature of points closer to

Is the estimated curvature from the other curvature estimation system 42

The road from the map database that is closest to is selected as the most likely road from the map database, and the associated curvature at that closest point is given by:

は、対応する曲率フィルタ５４．１’の関連するカルマンフィルタ５４’に対する計測値として使用され、この計測値は、対応するマップベース道路曲率推定値

および関連する共分散

を生成するのに使用される。 Referring to FIG. 25, the curvature from the map system 88 of the point on the road that is closest to the position of the host vehicle 12 from the vehicle navigation system 86.

Is used as a measure for the associated Kalman filter 54 ′ of the corresponding curvature filter 54.1 ′, which is the corresponding map-based road curvature estimate.

And related covariances

Used to generate

を使用して、道路３４の道路曲率の推定値を求めることができる。ｔ番目のターゲットの運動学は、以下に示す一定加速度運動力学方程式によって与えられると仮定し、これは補助フィルタ９０．１の拡張カルマンフィルタ９内に具現化され、

ここで、Ｔはサンプリング周期、上添え字(・)^ｔは特定のターゲットを表わし、上添え字(・)^ａは、フィルタが補助であることを示すのに使用される。 Referring to FIG. 26, according to another aspect of the road curvature estimation subsystem 42 ″, based on the assumption that under normal driving conditions, the target vehicle 26 is assumed to follow the road 34, the radar Measured by sensor 14-the associated trajectory of the target vehicle 36

Can be used to determine an estimate of the road curvature of the road 34. Assume that the kth target kinematics is given by the constant acceleration kinematics equation shown below, which is embodied in the extended Kalman filter 9 of the auxiliary filter 90.1:

Here, T is the sampling period, the superscript (•) ^t represents a specific target, and the superscript (•) ^a is used to indicate that the filter is auxiliary.

は非線形であり、次式で与えられる。

拡張カルマンフィルタ９０は、関連するヤコビアンマトリックスを使用して、非線形計測関数

の線型化を行い、ターゲット状態

の推定値、およびそれに関連する誤差共分散

をもたらし、これらは、関連する計測プロセッサ９２によって変換され、それによって計測入力

および関連する誤差共分散

を、関連する曲率フィルタ９４．１の関連するカルマンフィルタ９４に供給する。計測入力

および関連する誤差共分散

は次式で与えられる。

Related measurement functions

Is nonlinear and is given by:

The extended Kalman filter 90 uses a related Jacobian matrix to generate a nonlinear measurement function.

Linearize the target state

Estimate and associated error covariance

Which are converted by the associated measurement processor 92 and thereby the measurement input

And the associated error covariance

To the associated Kalman filter 94 of the associated curvature filter 94.1. Measurement input

And the associated error covariance

Is given by:

で与えられ、関連する計測マトリックス

は以下のように与えられる。

The system equation of the related Kalman filter 94 of the related curvature filter 94.1 is:

The associated measurement matrix given in

Is given by:

The auxiliary filter 92.1 and the curvature filter 94.1 of the road curvature estimation subsystem 42 ″ operate according to the appendix.
Referring to FIG. 27, according to another aspect, the predictive collision detection system 10.1 includes a plurality of road curvature estimation subsystems 42.1, 42.2,. . . 42. N, each of which is in accordance with any one of the various aspects of the road curvature estimation subsystem 42, 42 ′ or 42 ″ described above, eg, as shown in FIGS. 4, 19, 23, 25, 26. To work. For example, in one aspect, the predictive collision detection system 10.1 incorporates a first road curvature estimation subsystem 42.1 and a second road curvature estimation subsystem 42.2 to provide a first road The curvature estimation subsystem 42.1 is a road curvature estimation subsystem 42 that is responsive to host vehicle measurements, and the second road curvature estimation subsystem 42.2 is from the vehicle navigation system 86 and associated map system 88. A road curvature estimation subsystem 42 'responsive to measured values.

で与えられ、ここでＲ_Ｃ０、Ｒ_Ｃ１およびＲ_Ｃは、それぞれＣ_０、Ｃ_１およびＣの誤差共分散である。
第２の道路曲率推定サブシステム４２．２から、対応する曲率推定は、Ｃ_ｇ（ｌ）で与えられ、対応する誤差分散はＲ_ｇで与えられ、ここでＲ_ｇは一般に一定のスカラーである。 From the first road curvature estimation subsystem 42.1, the curvature estimate and the associated error covariance at a distance l from the current position along the road 34 are respectively

Where R _C0 , R _C1 and R _C are the error covariances of C ₀ , C ₁ and C, respectively.
From the second road curvature estimation subsystem 42.2, the corresponding curvature estimation is given by C g _(l), the corresponding error variance is given by R _g, where R _g is generally constant scalar .

ここで、ＧおよびＧ_ｇは重みであり、次式で与えられる。

The error covariance associated with the curvature estimate is combined by the road curvature fusion subsystem 96, for example, as follows.

Here, G and G _g are weights and are given by the following equations.

The fusion curvature C _f (l) and the associated error covariance R _f (l) are used by other processes, for example, to improve the estimation of the position of the host vehicle 12 or target vehicle 36 or for collision prediction. be able to. For example, in the embodiment of FIG. 27, the fusion curvature C _f (l) and the associated error covariance R _f (l) are input to the constrained target state estimation subsystem 46 to estimate the constrained target state, where The constrained target state estimation subsystem 46 and the associated unconstrained target state estimation subsystem 44, the target state determination subsystem 48, and the target state fusion subsystem 50 operate in accordance with the embodiment shown in FIG.

  In the foregoing detailed description, certain aspects are described in detail and illustrated in the accompanying drawings, but various modifications and changes may be made to these details in light of the overall teachings of the disclosure. One skilled in the art will understand that it can be created. Accordingly, the specific arrangements disclosed are for purposes of illustration only and are not limiting on the scope of the invention, which includes all that can be derived from the description herein. The full scope of the claims and all equivalents should be given.

ここで、

はシステム状態ベクトル、Ｆ_ｋは、システムマトリックスであり、

は、各状態変数に対応するノイズ変数の関連するベクトルであり、各ノイズ変数は、平均値０と、関連する分散ベクトルＲ_ｋの対応する要素によって与えられる分散Ｑ_ｋとを有する。 Appendix-Description of Kalman Filtering A Kalman filter is used to estimate from a set of noisy measurements the state of a motion system exposed to noise and the associated covariance.
The motor system is defined by the following equation.

here,

Is the system state vector, F _k is the system matrix,

Is an associated vector of noise variables corresponding to each state variable, each noise variable having a mean value of 0 and a variance Q _k given by the corresponding element of the associated variance vector R _k .

ここで、

はシステム計測値ベクトル、Ｈ_ｋは計測マトリックスであり、

は各計測変数に対応するノイズ変数の関連するベクトルであり、各ノイズ変数は、平均値０と、関連する分散ベクトルＲ_ｋの対応する要素によって与えられる分散とを有する。関連する共分散マトリックスＲ_ｋの要素の値は、関連する動作条件を代表する組に対して、関連するシステムを代表する計測値を分析することにより、事前に求めることができる。関連する共分散マトリックスＱ_ｋの要素の値は、モデリング誤差を説明する。一般に、関連するマトリックスＦ_ｋ、Ｑ_ｋ、Ｈ_ｋ、Ｒ_ｋは時間と共に変化することができる。 The state of motion of the relevant system measurements is given as follows:

here,

Is the system measurement vector, H _k is the measurement matrix,

Is the associated vector of noise variables corresponding to each measurement variable, each noise variable having a mean value of 0 and the variance given by the corresponding element of the associated variance vector R _k . The values of the elements of the associated covariance matrix R _k can be determined in advance by analyzing the measured values representative of the relevant system against a set representative of the relevant operating conditions. Values of the elements of the associated covariance matrix Q _k describes the modeling error. In general, the associated matrices F _k , Q _k , H _k , R _k can change over time.

と、状態

の初期値および時間ｋ−１における関連する共分散

が与えられると、カルマンフィルタを使用して、時間ｋにおける関連する状態

および関連する共分散

が推定される。
フィルタリングプロセスにおける第１のステップは、時間ｋにおける状態

および関連する共分散

の推定値を、時間ｋ−１の推定値に基づいて、以下ように計算することである。

Measured value at time k

And state

Initial value and associated covariance at time k−1

Given the associated state at time k using the Kalman filter

And related covariances

Is estimated.
The first step in the filtering process is the state at time k

And related covariances

Is calculated based on the estimated value of time k−1 as follows.

および関連する共分散マトリックスＳ_ｋを、以下のように予測することである。

次のステップは、状態ベクトル

および関連する共分散

を更新するために使用される、ゲインマトリックスＧ_ｋを以下のように計算することである。

最後に、状態ベクトル

および関連する共分散マトリックス

が、時間ｋにおいて、関連する計測値

に応答して、以下のように推定される。

The next step is the measured value at time k

And the associated covariance matrix S _k is predicted as follows:

The next step is the state vector

And related covariances

Is used to update the gain matrix G _k as follows:

Finally, the state vector

And related covariance matrices

Is the relevant measurement at time k

Is estimated as follows.

It is a block diagram which shows the hardware relevant to a prediction collision detection system. It is a figure which shows the range of the radar beam used with a prediction collision detection system. It is a figure which shows the driving scenario aiming at showing operation | movement of a prediction collision detection system. It is a block diagram which shows the signal processing algorithm relevant to the hardware of a prediction collision detection system. It is a flowchart which shows the signal processing algorithm relevant to a prediction collision detection system. It is a figure which shows the geometric shape used in order to specify the curvature parameter of a road. It is a figure which shows the geometric shape of an arc. It is a figure which shows the example of estimation of the target position with respect to a straight road. It is a figure which shows the example of estimation of the road curvature parameter with respect to a straight road. It is a figure which shows the example of estimation of the lateral speed with respect to a straight road. It is a figure which shows the example of estimation of the road curvature parameter with respect to a straight road. FIG. 9 is a diagram illustrating an example of a target state RMS error due to unconstrained filtering on a straight road corresponding to FIGS. It is a figure which shows the example of the target state RMS error by the constraint filtering on a straight road corresponding to FIG. It is a figure which shows the example of estimation of the target position with respect to a curved road. It is a figure which shows the example of estimation of the road curvature parameter with respect to a curved road. It is a figure which shows the example of estimation of the lateral speed with respect to a curved road. It is a figure which shows the example of estimation of the road curvature parameter with respect to a curved road.

FIG. 10 is a diagram illustrating an example of a target state RMS error by unconstrained filtering on a curved road corresponding to FIGS. 10a to 10d. It is a figure which shows the example of the target state RMS error by the restriction | limiting filtering on a curved road corresponding to FIG. It is a figure which shows the example of the estimation of the target position with respect to a straight road including a lane change. It is a figure which shows the example of the estimation of the road curvature parameter with respect to a straight road including a lane change. It is a figure which shows the example of estimation of the lateral speed with respect to a straight road including a lane change. It is a figure which shows the example of the estimation of the road curvature parameter with respect to a straight road including a lane change. It is a figure which shows the example of the estimation of the target position with respect to a curved road including a lane change. It is a figure which shows the example of the estimation of the road curvature parameter with respect to a curved road including a lane change. It is a figure which shows the example of the estimation of the lateral speed with respect to a curved road including a lane change. It is a figure which shows the example of the estimation of the road curvature parameter with respect to a curved road including a lane change. FIG. 6 is a block diagram illustrating hardware associated with another aspect of a predictive collision detection system. It is a free body figure which shows the steered wheel. It is a figure which shows the geometric shape of the two-wheeled vehicle model of the vehicle in turning. FIG. 16b shows the geometry of the steered wheel shown in FIG. 16a. It is a figure which shows a switching curve. FIG. 18 is a flowchart showing a process related to the switching curve shown in FIG. 17. FIG. It is a block diagram which shows the road curvature estimation subsystem for estimating a road curvature from a host vehicle state estimated value. It is a figure which shows the curvature filter relevant to the 1st aspect of a curvature estimator.

It is a figure which shows the curvature filter relevant to the 4th aspect of a curvature estimator. It is a figure which shows the road model relevant to various kinds of roads. It is a block diagram which shows the 10th aspect of a road curvature estimation subsystem. It is a flowchart which shows an interaction multiple model algorithm. FIG. 6 is a block diagram illustrating a curvature estimation subsystem that is responsive to vehicle position and associated road curvature data from an associated map system. FIG. 3 is a block diagram illustrating a curvature estimation subsystem that responds to radar measurements of a target vehicle on a road. FIG. 3 is a block diagram illustrating a predictive collision detection system including a plurality of road curvature estimation subsystems and associated road curvature fusion subsystems.

Claims (1)

a. A first road adapted to estimate a first set of at least one first curvature parameter in response to a measure of a host vehicle's longitudinal velocity on the road and a measure of the host vehicle's yaw rate; In response to a measure of a second set of at least one second curvature parameter from a map database responsive to a measure of the position of the host vehicle, a curvature estimation subsystem, the second set of at least one second It adapted to estimate a curvature parameter of the second road curvature estimation subsystem and adapted to estimate a third at least one third curvature parameters set in response to the image of the road A plurality of road curvature estimation subsystems selected from a third road curvature estimation subsystem; and b. An error covariance associated with the first set of at least one first curvature parameter, an error covariance associated with the second set of at least one second curvature parameter, or the third set of A processor adapted to combine at least two of the error covariances associated with the at least one third curvature parameter to produce a fusion curvature and an associated error covariance;
A road curvature estimation system including
The third road curvature estimation subsystem is:
i. A visual sensor adapted to generate the image of the road; and ii. The road image in response to the adapted to generate the third set of at least one third the estimate, including the curvature estimator, the road curvature estimation system.

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