JP2009274507A - Vehicular turning characteristic estimation device and turning characteristic estimation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain behavior of a vehicle from an estimated stability factor with a small calculation amount and small storage capacity. <P>SOLUTION: This vehicular turning characteristic estimation device includes: a stability factor estimator estimating the present stability factor of the vehicle from vehicle speed, backward/forward acceleration, a yaw rate, lateral acceleration, a steering angle of the vehicle; a reference stability factor storage part preset with a reference stability factor to the vehicle; a stability factor difference calculation part calculating a stability factor difference that is a difference between the present stability factor and the reference stability factor; and a turning characteristic estimation part estimating a turning characteristic of the vehicle by referring to a turning characteristic data table. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle turning characteristic estimation device and a turning characteristic estimation method for predicting a change in vehicle characteristics from an estimated current stability factor.

  In a conventional turning characteristic estimation device, a transfer function between an actual yaw rate detected by a sensor and a reference yaw rate γ (s) obtained by Laplace transform of an expression derived from a two-wheel model of a vehicle is used as a first-order lag transfer function. The stability factor and the time constant coefficient are obtained by the successive least square method using the ARX model (see, for example, Patent Document 1).

なお、式（１）においてＶは車速、Ｌはホイールベース、Ｋｈはスタビリティファクタ、Ｔｐは車速依存の時定数をもつ一次遅れ系の車速Vにかかる係数（以下、時定数係数と呼ぶ）、δ（ｓ）、Ｇｙ（ｓ）はそれぞれ車輪の実舵角、車両の横加速度をラプラス変換したものである。

In Equation (1), V is the vehicle speed, L is the wheel base, Kh is the stability factor, Tp is a coefficient relating to the vehicle speed V of the first-order lag system having a time constant dependent on the vehicle speed (hereinafter referred to as a time constant coefficient), δ (s) and Gy (s) are Laplace transforms of the actual steering angle of the wheel and the lateral acceleration of the vehicle, respectively.

JP 2004-26073 A (pages 4-5, FIG. 5)

  In the technique of Patent Document 1, since the transfer function is estimated as a first-order lag transfer function and the stability factor and the time constant coefficient are obtained, the actual steering angle δ, the vehicle speed V, the lateral acceleration Gy, the actual yaw rate γ, Six data of stability factor Kh and time constant coefficient Tp must be stored in the buffer for two or more control cycles, and the number of data stored in the above control keeps increasing as the control cycle continues, and with a small number of data As a result, accuracy is not obtained, and as a result, a large storage capacity and calculation amount are required. For example, it is difficult to implement in an ECU generally used in electric power steering (hereinafter referred to as EPS). was there.

  The present invention has been made to solve the above-described problems. In order to estimate the gain or phase from the steering angle to the yaw rate, the estimated stability factor and the pre-stored reference stability factor are provided. Because the deviation data table is used, the required buffers are only 4 in total, including the calculated value of the stability factor used during the stability factor estimation, the two turning state flags, and the number n of control cycles followed by the stable turning state. Therefore, an object of the present invention is to provide a vehicle turning characteristic estimation device and a turning characteristic estimation method for estimating a change in vehicle turning characteristics even with an inexpensive ECU generally used for EPS.

  A turning characteristic estimation device for a vehicle according to the present invention includes a steering angle detection unit that detects a steering angle of the vehicle, a lateral acceleration detection unit that detects a lateral acceleration of the vehicle, and a yaw rate detection unit that detects a yaw rate of the vehicle. Longitudinal acceleration detection means for detecting longitudinal acceleration of the vehicle, vehicle speed detection means for detecting vehicle speed of the vehicle, steering angle detection means, lateral acceleration detection means, yaw rate detection means, longitudinal acceleration detection means, vehicle speed detection A stability factor estimator that estimates the current vehicle stability factor from the vehicle steering angle, lateral acceleration, yaw rate, longitudinal acceleration, and vehicle speed detected by each means, and a standard set in advance for each vehicle A standard stability factor storage unit storing stability factors, and a stability estimated by the stability factor estimator. A stability factor deviation calculation unit for calculating a deviation between the stability factor and the reference stability factor stored in the reference stability factor storage unit, and data storing vehicle turning characteristics for each of the stability factor deviations By referring to the table, the turning characteristic of the vehicle is estimated by the turning characteristic estimation unit that estimates the turning characteristic of the vehicle.

  According to the present invention, it is not necessary to perform transfer function parameter estimation or the like by estimating the turning characteristics of the vehicle from the deviation between the stability factor estimated by the stability factor estimator and the reference stability factor. This brings about an unprecedented remarkable effect that it is possible to reduce the calculation amount and the storage capacity necessary for estimating the turning characteristics.

Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram showing an embodiment of a turning characteristic estimation device for a vehicle according to the present invention.
In FIG. 1, 10a, 10b, 10c, and 10d indicate the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel of the vehicle 12, respectively. Further, as the steering wheel 11 rotates, the left and right front wheels 10a and 10b, which are steered wheels, are steered.
The vehicle 12 includes a steering angle sensor 21 that detects the steering angle θ of the steering wheel 11, a lateral acceleration sensor 22 that detects the lateral acceleration Gy of the vehicle, a yaw rate sensor 23 that detects the yaw rate γ of the vehicle, and a longitudinal acceleration vehicle Gx of the vehicle. A longitudinal acceleration sensor 24 for detecting the vehicle speed and a vehicle speed sensor 25 for detecting the vehicle speed V are provided.

As shown in FIG. 1, the steering angle θ detected by the steering angle sensor 21, the lateral acceleration Gy detected by the lateral acceleration sensor 22, the actual yaw rate γ detected by the yaw rate sensor 23, and the longitudinal acceleration sensor 24 are detected. The longitudinal acceleration Gx and the vehicle speed V detected by the vehicle speed sensor 25 are input to the turning characteristic estimation device 30.
The turning characteristic estimation device 30 is for estimating the turning characteristic of a vehicle. A stability factor estimator 31 for estimating the current vehicle stability factor (hereinafter, estimated stability factor) is preset for each vehicle. A reference stability factor storage unit 32 for storing a stability factor (reference stability factor), a stability factor deviation calculation unit 33 for calculating a deviation between the estimated stability factor and the reference stability factor, and a vehicle turning characteristic from the deviation And a turning characteristic estimator 34 for estimating.

FIG. 2 is a flowchart showing a procedure for estimating the turning characteristic of the vehicle by the turning characteristic estimation device 30. The input signal is read (S10) and input to the stability factor estimator 31. The stability factor estimator 31 may use a known technique such as JP-A-2005-104346.

In general, the stability factor A _gen is m for the vehicle, L for the wheel base, K _f for the front wheel cornering power, K _r for the rear wheel cornering power, l _{f for} the distance from the vehicle center of gravity to the front wheel, and the rear wheel for the rear wheel. Is _expressed by the following equation (2).

When the cornering power of the front and rear wheels is changed or when a load is loaded, the stability factor of the vehicle changes according to the above equation. As shown in FIG. 3, the yaw rate gain and the phase delay are Therefore, the yaw rate gain or the phase delay is obtained as described below.

The input to the stability factor estimator 31, the steering angle θ, the lateral acceleration Gy, the actual yaw rate γ, the longitudinal acceleration Gx, the vehicle speed V and the steering angular velocity ω obtained by time differentiation of the steering angle θ is the magnitude of the yaw rate γ. A first condition (| γ |> Yaw _SB ) that γ | is larger than a predetermined value (threshold value) Yaw _SB set in advance, and a predetermined value (threshold value) in which the magnitude | Gx | of the longitudinal acceleration Gx is set in advance. Gx second condition that less than _ST and _{(| | Gx <Gx ST)} , the magnitude of the lateral acceleration Gy | Gy | third condition that lies within a range set in advance _{(Gy SB <| Gy | <} Gy and _ST), the magnitude of the vehicle speed V | V | a <V _ST), the magnitude of the steering angular velocity omega | | fourth condition that (V _SB <lies is within a preset range | V omega | is preset and predetermined value fifth condition that less than (threshold) and _{(| | ω <ω ST)} , the steering angle θ Magnitude | theta | is a predetermined value sixth condition that is greater than _{(threshold) (θ SB <| θ |} ) and, when the both are satisfied the conditions of, referred to as a stable turning state The stability factor A calculated by the following equation (3) is accumulated and stored during the control cycle in which these conditions are satisfied.

ここでＧはステアリングギア比、Ｌは車両のホイールベースを表す。

Here, G represents a steering gear ratio, and L represents a vehicle wheel base.

Further, while the stable turning continues, the counter n is incremented by 1 per control cycle, and the number of control cycles in which the stable turn is continued is counted.
Then, even if one of the first to sixth conditions is not satisfied, that is, by dividing the calculated value of the stability factor accumulated when the stable turn is completed by n, an average value of the stability factor during the stable turn is obtained. Is output as an estimated value of the stability factor (S20). The reference stability factor stored in the reference stability factor storage unit 32 is output to the stability factor deviation calculation unit 33 (S30), and the estimated stability estimated by the stability factor estimator 31 from the reference stability factor. By reducing the factor, the deviation of the stability factor is calculated in the stability factor deviation calculating unit 33 (S40), and the stability factor deviation is input to the turning characteristic estimating unit 34.
The turning characteristic estimation unit 34 stores a data table of yaw rate gain or phase lag created by changing the vehicle stability factor, and is calculated by the stability factor deviation calculation unit 33 as shown in FIG. Based on the deviation, the yaw rate gain or phase delay is estimated by referring to the data table of the stability factor deviation and the yaw rate gain, or the stability factor deviation and the yaw rate phase delay (S50).

With this configuration, it is possible to estimate the yaw rate gain or phase lag at all frequencies by calculating the deviation between the estimated stability factor and the reference stability factor and referring to the data table of the yaw rate gain or phase lag It becomes.

Further, in this configuration, the longitudinal acceleration Gx is not the value detected by the longitudinal acceleration sensor 24, but the value obtained by differentiating the vehicle speed V detected by the vehicle speed detecting means 25 is used in the vehicle traveling direction on the road surface. Since it is not affected by the gradient, a more accurate longitudinal acceleration value is obtained.

Embodiment 2. FIG.
Further, in the turning characteristic estimation unit 34, among the deviations of the stability factor and the yaw rate gain or the phase delay at all frequencies as shown in FIG. 3, the sudden steering region in which the yaw rate gain or the phase delay varies depending on the deviation of the stability factor. For example, by limiting to the shaded area of 0.5 to 1.5 Hz shown in FIG. 4, several frequencies (for example, 0.5 Hz, 1.0 Hz, 1.. 5Hz), the horizontal axis is the stability factor deviation, the vertical axis is the yaw rate gain or phase delay, and the yaw rate gain or phase delay between each frequency is interpolated to interpolate the yaw rate from the stability factor deviation. Estimate gain or phase lag.

With this configuration, it is possible to estimate the yaw rate gain or phase delay from the stability factor deviation with only a few data tables (three in this configuration) in the sudden steering region where the influence of the yaw rate gain or phase delay is large. It is possible to reduce the man-hours for creating the table and the amount of calculation.
In this configuration, any number of data tables may be used. For example, five data tables may be used to increase accuracy.

The block diagram of the vehicle and turning characteristic estimation apparatus by Embodiment 1 or 2 of this invention is shown. It is a flowchart which shows the turning characteristic estimation apparatus by Embodiment 1 or 2 of this invention. It is a Bode diagram which shows the change of a yaw rate gain and a phase delay by the change of the stability factor deviation by Embodiment 1 or 2 of this invention. It is an example of the explanatory view which shows the sudden steering area | region in the Bode diagram of the yaw rate gain and phase delay by the change of the stability factor deviation by Embodiment 2 of this invention. It is an example of the graph which shows the change of the stability factor deviation in the specific frequency of the rapid steering area | region by the Embodiment 2 of this invention, a yaw rate gain, and a phase delay.

Explanation of symbols

10a left front wheel, 10b right front wheel, 10c left rear wheel, 10d right rear wheel, 11 steering wheel, 12 vehicle, 21 steering angle sensor, 22 lateral acceleration sensor, 23 yaw rate sensor, 24 longitudinal acceleration sensor, 25 vehicle speed sensor, 30 turn Characteristic estimation device, 31 Stability factor estimator, 32 Reference stability factor storage unit, 33 Stability factor deviation calculation unit, 34 Turning characteristic estimation unit.

Claims (4)

Steering angle detection means for detecting the steering angle of the vehicle;
Lateral acceleration detecting means for detecting lateral acceleration of the vehicle;
Yaw rate detection means for detecting the yaw rate of the vehicle;
Longitudinal acceleration detecting means for detecting longitudinal acceleration of the vehicle;
A vehicle having vehicle speed detecting means for detecting the vehicle speed of the vehicle;
The current vehicle stability is determined from the vehicle steering angle, lateral acceleration, yaw rate, longitudinal acceleration, and vehicle speed detected by the steering angle detection means, lateral acceleration detection means, yaw rate detection means, longitudinal acceleration detection means, and vehicle speed detection means. A stability factor estimator for estimating the factor;
A reference stability factor storage unit storing a reference stability factor set in advance in the vehicle;
A stability factor deviation calculation unit that calculates a stability factor deviation that is a deviation between the stability factor estimated by the stability factor estimator and the reference stability factor stored in the reference stability factor storage unit;
A turning characteristic estimation unit for estimating a turning characteristic of the vehicle by referring to a turning characteristic data table in which the turning characteristic of the vehicle for each stability factor deviation is stored;
An apparatus for estimating turning characteristics of a vehicle. The vehicle turning characteristic estimation apparatus according to claim 1, wherein the turning characteristic of the vehicle is a yaw rate gain or a phase delay. 3. The turning characteristic at the time of sudden steering is estimated by estimating the turning characteristic at a plurality of frequencies during sudden steering, and interpolating the turning characteristic between the estimated plurality of frequencies. The turning characteristic estimation device for a vehicle according to claim 1. Steering angle detection means for detecting the steering angle of the vehicle;
Lateral acceleration detecting means for detecting lateral acceleration of the vehicle;
Yaw rate detection means for detecting the yaw rate of the vehicle;
Longitudinal acceleration detecting means for detecting longitudinal acceleration of the vehicle;
Vehicle speed detection means for detecting the vehicle speed of the vehicle;
A stability factor estimator;
A reference stability factor storage unit;
A stability factor deviation calculator,
A turning characteristic estimation unit;
In a vehicle having
The stability factor is estimated from the vehicle steering angle, lateral acceleration, yaw rate, longitudinal acceleration, and vehicle speed detected by the steering angle detection means, lateral acceleration detection means, yaw rate detection means, longitudinal acceleration detection means, and vehicle speed detection means, respectively. To estimate the current vehicle stability factor,
In the reference stability factor storage unit, a reference stability factor stored in advance in the vehicle is stored,
In the stability factor deviation calculator, the deviation between the estimated current vehicle stability factor and the reference stability factor is calculated,
A turning characteristic estimation method for estimating a turning characteristic of a vehicle by referring to a turning characteristic data table in which the turning characteristic of the vehicle for each deviation is stored in the turning characteristic estimation unit.

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