JP2006199242A - Behavior controller of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle behavior controller capable of performing zero point calibration of the yaw rate even during the travel. <P>SOLUTION: The vehicle behavior controller controls the vehicle behavior according to the behavioral information of the vehicle detected by a yaw rate sensor or the like. The controller comprises a rectilinear movement determining means for determining whether the vehicle travels straightly based on the image photographed by an image photographing means for photographing an image in front of the vehicle, and a zero point calibration means for matching the output value of the yaw rate sensor with zero when the vehicle is determined to travel straightly by the rectilinear movement determining means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle behavior control device, and more particularly to a vehicle behavior control device capable of calibrating a zero point drift of a yaw rate sensor.

  A vehicle may be provided with a yaw rate sensor in order to improve stability when the vehicle is running (for example, prevention of lateral slipping). The yaw rate sensor detects a rotational angular velocity (hereinafter referred to as a yaw rate) about an axis (rolling axis) that passes through the center of gravity of the vehicle and extends in the front-rear direction of the vehicle, and sends the signal to a vehicle control device that controls the behavior of the vehicle. To do.

  However, since the yaw rate sensor has a property that the zero point drifts as the temperature changes and time passes (hereinafter referred to as zero point drift), it is necessary to adjust the zero point periodically.

  The zero point calibration of the yaw rate sensor is possible by making the output value coincide with zero when the vehicle is stopped and no yaw rate is generated. However, since the output characteristics of the yaw rate sensor change while the vehicle is traveling, it is desirable to perform the output characteristics not only when the vehicle is stopped but also when the vehicle is traveling.

  For this reason, a standard yaw rate is calculated based on the steering angle detected by the steering angle sensor and the vehicle speed detected by the vehicle speed sensor. When the standard yaw rate is zero, it is estimated that no yaw rate has occurred, and the yaw rate sensor An invention for matching an output value to zero (zero point calibration) has been proposed (see, for example, Patent Document 1).

Further, the yaw rate is calculated based on the difference between the left and right wheel speeds detected by the wheel speed sensor, and when the yaw rate calculated based on the wheel speed difference is zero, it is estimated that no yaw rate has occurred and the yaw rate sensor An invention for matching an output value to zero (zero point calibration) has been proposed (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 5-314397 Japanese Patent Laid-Open No. 11-23606

  However, in the method described in Patent Document 1, since it is necessary to mount the steering angle sensor and detect the steering angle with high accuracy, if the accuracy of mounting the steering angle sensor and detecting the steering angle is poor, there is an error in the reference yaw rate. There is a limit to the accuracy of zero point calibration based on the reference yaw rate.

  In the method described in Patent Document 2, the effective diameters of the left and right tires do not necessarily match due to dimensional errors in manufacturing tires and wheels, inconsistencies in air pressure, inconsistencies in wear levels, and mounting of different diameter tires. An error is likely to occur in the yaw rate calculated based on the difference, and the accuracy of zero point calibration based on the yaw rate is limited.

  In view of the above problems, an object of the present invention is to provide a vehicle behavior control device capable of calibrating the zero point of the yaw rate even while traveling.

  In view of the above problems, the present invention was photographed by an image photographing means for photographing an image ahead of a vehicle in a vehicle behavior control device that controls the behavior of the vehicle in accordance with vehicle behavior information detected by a yaw rate sensor or the like. A straight-ahead determining means for determining whether or not the vehicle is traveling straight based on the image; and a zero-point calibration means for matching the output value of the yaw rate sensor to zero when the straight-ahead determining means determines that the vehicle is traveling straight. It is characterized by having.

  According to the present invention, a vehicle capable of calibrating the zero point of the yaw rate even during traveling by determining whether or not the vehicle is traveling straight on the basis of an image ahead of the vehicle captured by image capturing means such as a camera. A behavior control device can be provided.

  In one embodiment of the present invention, a white line detecting unit that detects a white line from an image photographed by the image photographing unit, and a vehicle when traveling on a predetermined traveling lane divided by the white line detected by the white line detecting unit. Yaw rate calculation means for calculating a yaw rate, and the straight travel determination means determines that the vehicle is traveling straight when the yaw rate calculated by the yaw rate calculation means is equal to or less than a predetermined threshold value. .

  In one embodiment of the present invention, the yaw rate calculation means includes a travel line estimation means for estimating a travel line in the travel lane, a travel direction of a vehicle at a predetermined position on the travel line estimated by the travel line estimation means, Yaw angle calculating means for calculating the yaw angle of the vehicle based on the traveling direction of the vehicle, and calculating the yaw rate based on the yaw angle calculated by the yaw angle calculating means and the traveling speed of the vehicle. It is characterized by.

  Further, in one aspect of the present invention, the straight travel determination unit includes a yaw rate integration unit that integrates the yaw rate calculated by the yaw rate calculation unit, and an average yaw rate calculation unit that calculates an average during integration of the yaw rate integrated by the yaw rate integration unit. And the zero point calibration means makes the output value of the yaw rate sensor coincide with zero when the average of the yaw rates calculated by the average yaw rate calculation means is equal to or greater than a predetermined threshold value.

  It is possible to provide a vehicle behavior control device capable of calibrating the zero point of the yaw rate even during traveling.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a functional configuration diagram of the vehicle behavior control device of the present embodiment.

  An image processing device 3, a yaw rate sensor 4, a wheel speed sensor 5, and a steering angle sensor 6 are connected to the vehicle behavior control device 7. The vehicle behavior control device 7 is connected to an engine ECU 8, a brake ECU 9, and an active steering 11.

  The yaw rate sensor 4 detects a rotational angular velocity around an axis (rolling axis) that passes through the center of gravity of the vehicle and extends in the front-rear direction of the vehicle, that is, a yaw rate (hereinafter referred to as a sensor yaw rate), and sends it to the vehicle behavior control device 7. The yaw rate sensor 4 may detect the yaw rate of the vehicle by any principle. For example, the Coriolis force generated when the vehicle rotates is used to detect the vibration of the vibrator of the polycrystalline silicon thin film. It is configured to detect as a change.

  The wheel speed sensor 5 is provided in each wheel, and sends a pulse signal corresponding to the wheel speed to the vehicle behavior control device 7. The rudder angle sensor 6 detects the rudder angle of the steered wheels and sends a signal corresponding to the rudder angle to the vehicle behavior control device 7. The vehicle behavior control device 7 can acquire the speed of the host vehicle and the rotation speed of each wheel based on the signal of the wheel speed sensor 5, and can acquire the steering angle of the vehicle based on the signal of the steering angle sensor 6.

  An image captured by the front camera 2 is sent to the image processing device 3. The front camera 2 is composed of a solid-state image sensor such as a CCD or a CMOS, and is installed, for example, in the vicinity of a room mirror in a passenger compartment to capture a predetermined range in front of the vehicle.

  The image processing apparatus 3 includes a white line detection unit 13, a yaw rate calculation unit 14, a travel line estimation unit 15, and a yaw angle calculation unit 16. A process in which the image processing apparatus 3 processes the image and calculates the yaw rate will be described with reference to FIG.

  FIG. 2 shows an example of a travel lane in which the host vehicle travels and a target travel line L. In FIG. 2, the vehicle 10 is traveling in the current traveling position B1. The white line detection means 13 of the image processing apparatus 3 first detects a white line that divides the travel lane of the vehicle 10. The white line detection means 13 searches for an area having brightness and contrast equal to or higher than a predetermined threshold from the bottom of the image upward based on the brightness and contrast of the image. If it is a white line, a rectangular region appears continuously or at a predetermined interval from the bottom of the image to the top, and if a rectangular shape equal to or greater than the predetermined threshold is detected, it is detected as a white line. By searching a number of such white line candidate points at each of the upper and lower positions of the image, the white line on the road ahead of the host vehicle can be recognized far.

  When the left and right white lines that define the driving lane in front of the host vehicle can be recognized (or estimated), the driving line estimation means 15 can, for example, set the center of the driving lane in front of the host vehicle as a straight line or curve connecting the midpoints of the left and right white lines When a white line is detected only on the line or on the right side or left side of the host vehicle, the target travel line L along which the host vehicle travels is estimated along the white line in consideration of the vehicle width and the like from the detected white line.

  When the target travel line L is estimated, the traveling direction of the vehicle at the predetermined position B2 when traveling on the target traveling line L can be estimated. Therefore, the yaw angle calculation means 16 is based on the difference from the current traveling direction of the vehicle 10. The change α (yaw angle) in the direction of travel of the vehicle can be calculated.

  Next, the yaw rate calculation means 14 detects the traveling speed by differentiating the distance from the white line detected based on the image data with respect to time. The yaw rate calculation means 14 calculates the image yaw rate of the host vehicle based on the yaw angle α and the traveling speed when traveling on the target travel line L (hereinafter, the yaw rate calculated based on the image data is referred to as an image yaw rate). . The traveling speed of the vehicle may be detected from the wheel speed sensor 5 or the like. Assuming that the traveling speed is constant, the larger the yaw angle α, the larger the image yaw rate is calculated, and the smaller the yaw angle α, the smaller the image yaw rate is calculated.

  Since the actual travel line slightly deviates from the target travel line L, the yaw rate calculation means 14 calculates the image yaw rate by correcting the deviation between the actual travel line and the target travel line L using image data, the steering angle, and the like. Is preferred. The image processing device 3 sends the calculated image yaw rate to the vehicle behavior control device 7 continuously or at predetermined time intervals.

  The vehicle behavior control device 7 includes a straight traveling determination unit 11, a zero point calibration unit 12, a white line detection unit 13, a yaw rate calculation unit 14, a travel line estimation unit 15, a yaw angle calculation unit 16, a yaw rate integration unit 17, and an average yaw rate calculation. It is configured to have means 18. The vehicle behavior control device 7 may include the white line detection unit 13, the yaw rate calculation unit 14, the travel line estimation unit 15, and the yaw angle calculation unit 16 included in the image processing device 3.

  The vehicle behavior control device 7 detects the running state of the vehicle based on the image yaw rate sent from the image processing device 3. The detection of the traveling state of the vehicle is how much the vehicle is traveling at a yaw rate. When the image yaw rate is zero or close to zero, the straight traveling determination means 11 of the vehicle behavior control device 7 causes the vehicle to travel straight ahead. It is determined that

  Moreover, since the sensor yaw rate detected by the yaw rate sensor 4 is sent to the vehicle travel control device 7, the sensor yaw rate can be monitored together with the image yaw rate. By the way, the detected value by the yaw rate sensor 4 has a property that the zero point drifts with temperature change and the passage of time (hereinafter referred to as zero point drift). Therefore, it can be determined that the average sensor yaw rate calculated when the straight traveling determination unit 11 determines that the vehicle is traveling straight ahead based on the image yaw rate is due to zero point drift.

  When the zero point is drifting, the yaw rate integration means 17 integrates the sensor yaw rate calculated by the yaw rate calculation means 14 for a predetermined time (hereinafter referred to as measurement time A), and the average yaw rate calculation means 18 The average of the sensor yaw rate integration time is calculated. By calculating the average, it is possible to reduce the variation in the detection value of the yaw rate sensor and calculate the zero point drift.

  When the average zero point drift is calculated, the zero point calibration means 12 matches the output value sent from the yaw rate sensor 4 to zero. This calibrates the zero point drift of the yaw rate sensor. To match the zero point of the sensor yaw rate to zero, the output value of the yaw rate sensor 4 may be increased or decreased by the amount corresponding to the zero point drift, or a reset signal that causes the yaw rate sensor 4 to set the output value to zero. May be sent.

  The target travel line L estimated by the travel line estimation means 15 is sent to the vehicle behavior control device 7, and the vehicle behavior control device 7 can cause the vehicle to travel according to the target travel line L. The vehicle behavior control device 7 outputs a control signal for traveling on the target travel line L to the engine ECU 8, the brake ECU 9, and the active steering 11 that can perform a forced steering operation.

  The engine ECU 8 adjusts the opening of the engine throttle based on the speed regulation and the current travel speed, the brake ECU 9 adjusts the wheel cylinder pressure according to the distance between the preceding vehicle and the like, and the active steering 11 The steering is steered so as to travel on the target travel line L.

  Further, the vehicle behavior control device 7 reduces the opening degree of the engine throttle when detecting the side slip of the front wheel or the rear wheel of the wheel based on the steering angle, the sensor yaw rate, the wheel speed of each wheel, the lateral acceleration of the vehicle, or the like. In addition to sending a signal to the engine ECU 8, the braking force of each wheel is controlled according to the turning direction and the side-sliding wheel to control the posture of the vehicle during traveling.

  Further, the vehicle behavior control device 7 increases or decreases the wheel cylinder pressure of each wheel so that the slip ratio of the wheel does not exceed a predetermined value when the wheel tends to be locked during braking. ) Function. Furthermore, when slipping of driving wheels occurs during transmission or acceleration, other well-known vehicle controls such as the function of traction control (TRC) are performed by appropriately controlling the wheel cylinder pressure of each wheel and the opening of the engine throttle. Realize.

  Based on the above configuration, a calibration procedure in which the vehicle behavior control apparatus calibrates the zero point of the yaw rate sensor will be described with reference to the flowchart of FIG. The calibration procedure of zero point calibration in FIG. 3 starts when the engine starts.

  First, the image processing device 3 sends the calculated image yaw rate to the vehicle behavior control device 7 continuously or at predetermined time intervals. The vehicle behavior control device 7 monitors the image yaw rate and determines whether or not the image yaw rate is equal to or less than a predetermined threshold value GY (S11). The case where the image yaw rate is equal to or less than the threshold value GY is a case where it is determined that the image yaw rate is sufficiently small and the vehicle is traveling straight ahead. If the image yaw rate is not equal to or less than the threshold value GY (No in step S11), the vehicle is in a traveling state other than straight traveling such as turning, so the calibration procedure in FIG. 3 ends. Note that the image processing apparatus 3 may determine whether the vehicle is traveling straight ahead.

  When the image yaw rate is equal to or lower than the threshold (Yes in step S11), the vehicle behavior control device 7 monitors the sensor yaw rate detected by the yaw rate sensor 5, and determines whether the sensor yaw rate is equal to or lower than a predetermined threshold SY. (S12). Since the sensor yaw rate may take a negative value and deviate, the sensor yaw rate compared with the threshold value SY in step S12 is the absolute value of the sensor yaw rate.

  By determining whether or not the sensor yaw rate is equal to or less than the threshold value SY, it can be confirmed whether or not the vehicle is traveling straight ahead by the sensor yaw rate. Therefore, it can be reliably determined that the vehicle is traveling straight ahead by steps S11 and S12. If the absolute value of the sensor yaw rate is not equal to or less than the threshold value SY (No in step S12), it is determined that the vehicle is in a traveling state other than straight traveling such as turning traveling, and the calibration procedure in FIG.

  When the absolute value of the sensor yaw rate is equal to or less than the threshold value SY (Yes in step S12), the yaw rate integration unit 17 integrates the sensor yaw rate value during the measurement time A (S13). FIG. 4 shows an example of the relationship between time and sensor yaw rate. Since the vehicle is running straight ahead, the sensor yaw rate shows a value that slightly fluctuates while showing a value close to zero. The yaw rate integration unit 17 integrates the sensor yaw rate by repeating the addition of the sensor yaw rate as shown in FIG.

  When the measurement time A has elapsed, the average yaw rate calculation means 18 calculates the average value of the sensor yaw rate at the measurement time A (S14). The average yaw rate calculation means 18 calculates the average of the sensor yaw rates by dividing the accumulated sensor yaw rate by the number of additions.

  Next, the vehicle behavior control device 7 determines whether or not the average absolute value of the sensor yaw rate is greater than or equal to the threshold value CY (S15). The threshold value CY (<SY) is a yaw rate value at which it is determined that the yaw rate sensor has drifted to zero and that calibration is preferable.

  When the average absolute value of the sensor yaw rate is equal to or greater than the threshold value CY (Yes in step S15), the zero point calibration unit 12 of the vehicle behavior control device 7 matches the output value sent from the yaw rate sensor 4 with zero (S16). . This calibrated the zero point drift. If the zero point drift is calibrated, vehicle behavior control such as vehicle attitude control can be performed more accurately.

  If the average absolute value of the sensor yaw rate is not equal to or greater than the threshold value CY (No in step S15), the drift amount is not so large as to calibrate the zero point drift, so the integrated sensor yaw rate is reset (S17), The calibration procedure of 3 is completed.

  According to the present embodiment, since it is determined whether or not the vehicle is traveling straight on the basis of the image taken by the front camera 2, the vehicle is surely affected without being affected by road surface conditions, crosswinds, tire conditions, and the like. It can be detected that the vehicle is traveling straight ahead. Since the zero point drift of the yaw rate sensor can be calibrated even while traveling, the zero rate of the yaw rate sensor can be maintained even when traveling for a long time on highways and suburban roads or when traveling at low speeds such as during traffic jams. The point drift can be calibrated. Accordingly, the opportunity for calibration of the yaw rate sensor can be increased, and even when the running state continues for a long time, the behavior of the vehicle can be detected accurately, and the controllability and reliability of the vehicle behavior can be improved. .

It is a functional lineblock diagram of a vehicle behavior control device. It is an example of the driving | running lane which the own vehicle drive | works. It is an example of the flowchart figure which shows the calibration procedure in which a vehicle behavior control apparatus calibrates the zero point of a yaw rate sensor. It is an example of the relationship between time and a sensor yaw rate.

Explanation of symbols

2 Front camera 3 Image processing device 4 Yaw rate sensor 5 Wheel speed sensor 6 Rudder angle sensor 7 Vehicle behavior control device 8 Engine ECU
9 Brake ECU
11 Active steering

Claims (4)

In a vehicle behavior control device that controls the behavior of a vehicle according to vehicle behavior information detected by a yaw rate sensor or the like,
Straight-ahead determination means for determining whether or not the vehicle is traveling straight on the basis of an image photographed by an image photographing means for photographing an image ahead of the vehicle;
When it is determined that the vehicle is traveling straight by the straight traveling determination unit, a zero point calibration unit that matches the output value of the yaw rate sensor with zero;
A vehicle behavior control device comprising: White line detection means for detecting a white line from an image photographed by the image photographing means;
Yaw rate calculation means for calculating the yaw rate of the vehicle when traveling on a predetermined travel lane divided by the white line detected by the white line detection means,
The straight traveling determination unit determines that the vehicle is traveling straight when the yaw rate calculated by the yaw rate calculation unit is a predetermined threshold value or less.
The vehicle behavior control device according to claim 1. The yaw rate calculating means includes
Traveling line estimation means for estimating a traveling line in the traveling lane;
A yaw angle calculation means for calculating a yaw angle of the vehicle based on the travel direction of the vehicle at a predetermined position on the travel line estimated by the travel line estimation means and the current travel direction of the vehicle;
Calculating the yaw rate based on the yaw angle calculated by the yaw angle calculating means and the traveling speed of the vehicle;
The vehicle behavior control device according to claim 2. The straight traveling determination means includes
Yaw rate integration means for integrating the yaw rate calculated by the yaw rate calculation means;
Average yaw rate calculating means for calculating an average during integration of the yaw rate integrated by the yaw rate integrating means,
The zero point calibration means matches the output value of the yaw rate sensor to zero when the average yaw rate calculated by the average yaw rate calculation means is a predetermined threshold value or more.
The vehicle behavior control device according to claim 3.

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