JP2005346304A - Road parameter calculation device and vehicle behavior control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a road parameter calculation device capable of accurately finding out curvature or a radius of a curve by effectively removing noise components of white line recognition at the time of calculating the curvature of a traveling route or the radius of a curve by using an image recognition result, and to provide a vehicle behavior control device using the road parameter calculation device. <P>SOLUTION: The time variation Δχ (calculated by step S2) of curvature χ is compared with a threshold Δχ limit, and when the variation Δχ is large, the variation Δχ is limited (steps S7 to S9). When the curvature χ is small (the radius of a curve is large), the limit value Δχ limit is set to a small value (B<C) and changed in accordance with vehicle speed Vn. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention acquires an image of a lane in which the host vehicle travels, identifies a traveling lane of the host vehicle from the acquired image, and calculates a road curvature or a curve radius, and a vehicle behavior using the same The present invention relates to a control device.

  There has been proposed a vehicle steering assist device that supports traveling of a vehicle along a travel lane (see, for example, Patent Document 1). In this support apparatus, first, an image of a lane in which the host vehicle travels is acquired using a CCD camera or the like. By detecting a road marking line (white line) that divides the travel lane by image recognition processing from the acquired image, travel lane information that the host vehicle should travel is acquired. Based on the acquired travel lane information, a steering torque necessary for steering is obtained and an appropriate steering assist torque is applied to assist the driver in steering.

In such a vehicle steering assist device, the shape parameter of the travel lane is used as a control parameter in calculating the steering assist torque. As the shape parameter, in the technique of Patent Document 1, the curvature of the road (the reciprocal of the curve radius) is used as the shape parameter, and the steering assist torque corresponding to the curvature is applied by feedforward control.
JP 2001-10518 A

  Here, the curve radius of the road is geometrically calculated based on the position information of the lane marking obtained by image recognition, and the curvature is obtained by taking the reciprocal thereof. Therefore, the detection accuracy of the curvature and the curve radius depends on the position recognition accuracy of the white line, but it is difficult to detect the partition line position with high accuracy for the following reason.

  First, if the geometric relationship between the road and the vehicle changes due to the gradient of the road, the inclination of the vehicle, etc., the position recognition accuracy of the lane markings decreases. Further, when the recognition process is performed from the captured image, it is handled as digital data having a predetermined number of pixels. However, it is difficult to increase the position recognition accuracy due to the limitation of the resolution at this time. On the other hand, increasing the resolution of the image increases the amount of calculation processing and requires a high-speed processing device, so the resolution cannot be increased too much. Furthermore, it is affected by sunshine, lighting conditions, weather conditions, and so on.

  As a result, it is difficult to improve the accuracy of the lane marking position information, and the obtained curvature and curve radius include noise components. When feed-forward control of the steering assist torque is performed, this noise component may generate a vibrational lateral acceleration, which may reduce the lane tracking performance of the vehicle.

  Therefore, the present invention provides a road parameter that can accurately determine the curvature or curve radius by effectively removing the noise component of white line recognition when determining the curvature or curve radius of the traveling road using the image recognition result. It is an object to provide a calculation device and a vehicle behavior control device using the calculation device.

  In order to solve the above problems, the road parameter calculation device according to the present invention acquires a lane image in which the host vehicle travels, recognizes the travel lane by image processing, and obtains the curvature or curve radius of the travel lane from the recognition result. The road parameter calculation device includes means for limiting the time change amount of the determined road curvature or curve radius to a limit value or less and outputting the result as a calculation result. This limit value is obtained when the road curvature is small or the curve It is characterized in that it is set to become smaller as the radius is larger.

  That is, a guard is applied and output so that the time change amount of the road curvature or the curve radius is within the limit value. At this time, the guard value is decreased as the road curvature is smaller (corresponding to the case where the curve radius is larger), so that the amount of time change is not increased. Here, the estimation of the curve radius by white line recognition is obtained geometrically based on the amount of deviation of the recognized white line from the straight line. Therefore, when the amount of deviation is large, that is, when the curve radius is small and the curvature is large, the estimation accuracy is reduced when the amount of deviation is small, that is, when the curve radius is large and the curvature is small. To do. In the present invention, the guard value is made different according to the tendency of accuracy.

  The faster the vehicle speed, the shorter it will pass through the same road section. For this reason, even with respect to the same road section, the time change amount of the curvature or the curve radius varies depending on the traveling speed. Accordingly, it is preferable that vehicle speed detection means for detecting the vehicle speed of the vehicle is further provided, and this limit value is set to be larger as the traveling speed of the host vehicle is higher when the road curvature or the curve radius is the same. In particular, when the road curvature or the curve radius is the same, the limit value may be directly proportional to the traveling speed of the host vehicle.

  When the road curvature exceeds the first curvature value, or when the curve radius is less than the first curve radius, the limit value may be set to a limit value based on the road structure standard. As described above, when the curve radius is small and the curvature is large, the accuracy of curve estimation is relatively maintained. On the other hand, since there is usually no steep curve exceeding the road structure standard, the guard value is set to a value based on the road structure standard to remove the noise component.

  A vehicle behavior control device according to the present invention includes any one of the above road parameter calculation devices and means for controlling the vehicle behavior based on the determined road curvature. The vehicle behavior control means is a device that controls the vehicle according to the curve state, and includes an automatic steering or steering assist device, a brake control device, a driving force control device, and the like.

  According to the present invention, by limiting the amount of time change in road curvature or curve radius, unnatural fluctuations such as curvature and curve radius can be suppressed. For example, when there is a vibration (noise) component due to uncertainties in white line recognition, it is possible to suppress the influence of this noise component, and the stability of vehicle behavior control using road curvature and curve radius・ Controllability is improved.

  Furthermore, by appropriately setting the guard value according to the vehicle speed, it becomes possible to acquire a stable road parameter regardless of the traveling state, and it is possible to ensure the stability and controllability of the vehicle behavior control.

  When the road curvature exceeds the first curvature value, or when the curve radius is less than the first curve radius, this limit value is set to a value based on the road structure standard, which contradicts the road structure. Since excessive changes in curve radius and curvature can be eliminated, the reliability of the acquired road parameters is improved.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.

  An embodiment of a vehicle behavior control device according to the present invention (including a road parameter calculation device according to the present invention) will be described below. A configuration diagram of a vehicle 1 including the vehicle behavior control device of the present embodiment is shown in FIG. The vehicle 1 includes an electronic control unit (ECU) 2, and vehicle behavior control (lane keeping control) is executed by the ECU 2. As shown in FIG. 1, the vehicle 1 includes a steering wheel 3. The steering wheel 3 is disposed in the vehicle interior of the vehicle 1 and steers steered wheels (here, left and right front wheels FR, FL) when operated by a driver. The steering wheel 3 is fixed to one end of the steering shaft 4. The steering shaft 4 rotates as the steering wheel 3 rotates.

  A rack bar 6 is connected to the other end of the steering shaft 4 via a steering gear box 5. The steering gear box 5 has a function of converting the rotational movement of the steering shaft 4 into the linear movement of the rack bar 6 in the axial direction. Both ends of the rack bar 6 are connected to the hub carriers of the wheels FL and FR via the knuckle arm 7. Because of this configuration, the wheels FL and FR are steered via the steering shaft 4 and the steering gear box 5 (rack bar 6) when the steering wheel 3 is rotated.

  Further, a CCD camera 8 for imaging the front is built in the rearview mirror (see FIG. 2). The CCD camera 8 photographs the surrounding situation in a predetermined area ahead through the front window 30 of the vehicle 1. Specifically, a moving image of the situation around the traveling lane 51 where the vehicle 1 on the road 50 is traveling is taken. An image processing unit 9 is connected to the CCD camera 8. The image data of the surrounding situation photographed by the CCD camera 8 is supplied to the image processing unit 9. The image processing unit 9 performs image processing on image data from the CCD camera 8 and travel lanes (travel route = lane) based on road marking lines (hereinafter referred to as white lines) drawn on the road on which the vehicle 1 travels. ) Is detected. In the captured image or video, the brightness difference between the road surface and the white line drawn on it is large, so the white line that divides the driving lane is relatively easy to detect by edge detection etc. and detects the lane ahead of the vehicle Convenient for

  The image processing unit 9 is connected to the ECU 2 described above. Based on the detected lane, the image processing unit 9 calculates the curve curvature (χ = 1 / R) of the forward travel route, the offset D of the vehicle 1 with respect to the lane (the center in the longitudinal direction of the vehicle), as shown in FIG. This corresponds to the amount of lateral deviation between the axis 1a and the tangent line 51a at the vehicle center of gravity of the center line of the travel lane 51.) and the yaw angle θ (the center axis 1a in the vehicle longitudinal direction and the center line of the travel lane 51 Corresponding to the angle formed with the tangent line 51a) is detected by calculation, and the result is sent to the ECU 2. Note that the curve curvature, the offset D, and the yaw angle θ may all be positive and negative, and the sign indicates the direction and direction. As a method for detecting various information amounts (curve curvature χ, vehicle offset D / yaw angle θ) of the forward travel route based on the image, a known method can be used.

  A steering angle sensor 10 and a vehicle speed sensor 11 are also connected to the ECU 2. The steering angle sensor 10 outputs a signal corresponding to the steering angle of the steering wheel 3. The vehicle speed sensor 11 is a wheel speed sensor attached to each wheel, and generates a pulse signal at a cycle corresponding to the speed of the vehicle 1. The vehicle speed sensor 11 functions as vehicle speed detection means. It is also possible to obtain a vehicle speed by attaching a sensor for detecting the longitudinal acceleration of the vehicle body as the vehicle speed detection means and integrating the output over time. The output signal of the steering angle sensor 10 and the output signal of the vehicle speed sensor 11 are respectively supplied to the ECU 2. The ECU 2 detects the steering angle based on the output signal of the steering angle sensor 10 and detects the vehicle speed based on the output signal of the vehicle speed sensor 11.

  In addition, a yaw rate sensor 12 and a navigation system 13 are also connected to the ECU 2. The yaw rate sensor 12 is disposed near the center of gravity of the vehicle 1, detects the yaw rate around the center of gravity vertical axis, and sends the detection result to the ECU 2. The navigation system 13 is a device for detecting the position of the vehicle 1 using GPS or the like. The navigation system 13 also has a function of detecting a situation such as a curve curvature (χ) and a gradient in front of the vehicle 1. The ECU 2 uses the navigation system 13 to grasp the position of the vehicle 1 and the road situation expected to travel.

  Further, a motor driver 14 is also connected to the ECU 2. The motor driver 14 is connected to a motor (actuator) 15 disposed in the steering gear box 5 described above. Although not shown, a ball screw groove is formed on a part of the outer peripheral surface of the rack bar 6, and a ball nut having a ball screw groove corresponding to the ball screw groove on the inner peripheral surface of the rotor of the motor 15. Is fixed. A plurality of bearing balls are accommodated between the pair of ball screw grooves, and when the motor 15 is driven, the rotor rotates to assist the axial movement of the rack bar 6, that is, the steering.

  The motor driver 14 supplies a drive current to the motor 15 in accordance with a command signal from the ECU 2. The motor 15 applies a steering torque corresponding to the drive current supplied from the motor driver 14 to the rack bar 6. The ECU 2 supplies a command signal to the motor driver 14 according to the logic described later and drives the motor 15 to displace the rack bar 6 and steer the wheels FL and FR.

  Further, a warning lamp 16 and a warning buzzer 17 are connected to the ECU 2. The warning lamp 16 is arranged at a position where a passenger in the passenger compartment can visually recognize and lights up according to a command signal from the ECU 2. Further, the alarm buzzer 17 emits a sound into the vehicle interior according to a command signal from the ECU 2. The ECU 2 drives the warning lamp 16 and the alarm buzzer 17 according to the logic described later, and alerts the occupant.

  Next, lane keeping control (vehicle behavior control) will be described together with road parameter calculation. FIG. 4 is a block diagram showing the operation of the lane keeping control, and FIG. 5 is a flowchart of the change rate limitation in the road parameter calculation.

  First, the front situation of the vehicle 1 is imaged by the CCD camera 8 (lower right in FIG. 2), and the situation (curve curvature χ) of the traveling lane 51 and the vehicle 1 are detected by the image processing unit 9 based on the captured image. An offset D and a yaw angle θ are calculated. The curve curvature χ is obtained by geometrically obtaining the curvature R of the forward curve from the captured image and taking the reciprocal thereof. As a geometrical calculation method, it may be performed with reference to the lateral displacement amount of the white line in front of the host vehicle 1 at a predetermined distance and the inclination of the tangent line of the white line in front of the host vehicle 1 at a predetermined distance.

Further, the target offset and yaw angle with respect to the travel route are determined in advance as the target offset D ₀ and the target yaw angle θ ₀ .

In calculating the control amount to the motor driver 14, it is necessary to calculate the yaw rate ω as the control amount. The yaw rate omega is obtained as the sum of the yaw rate omega _theta compensating the yaw rate omega _d and the yaw angle theta for compensating the offset D in the yaw rate omega _r based on the curve curvature chi.

First, based on the vehicle 1 ahead of the curve curvature chi, obtains the yaw rate omega _r necessary for running along the vehicle 1 on the curve. First, the change rate limiting means 20 calculates a correction value χc of the curve curvature χ. The change rate limiting means 20 and the image processing unit 9 constitute a road parameter calculation device according to the present invention. Note that the change rate limiting means 20 may be incorporated in the image processing unit 9, or a portion for detecting white line information is configured in the image processing unit 9, so that the road parameter calculation and the change rate limiting means 20 are separated. You may comprise, and you may incorporate these in ECU2. Furthermore, the image processing unit 9 and the ECU 2 can be integrated.

  Here, the change rate limiting operation will be described in detail with reference to FIG. This processing operation is repeatedly executed at every predetermined time step. First, the curvature χ and the vehicle speed Vn are read (step S1). Next, a difference Δχ between the curvature χ read at the current time step and the value of χ old which is the curvature correction value at the previous time step is obtained (step S2). This corresponds to the amount of time change in curvature. Then, it is determined whether or not the reciprocal of the absolute value of the curvature correction value χold is greater than or equal to the threshold value A. This corresponds to determining whether or not the correction value of the curve radius at the previous time step is equal to or greater than the threshold value A (first curve radius). Instead, the same result is obtained even if it is determined whether or not the absolute value of χold is equal to or less than the threshold value 1 / A (first road curvature).

  If the determination result is YES and it is determined that the curve radius is large (the road curvature is small), a value obtained by multiplying the vehicle speed Vn by a predetermined coefficient B is set as the road curvature change limit value Δχlimit (step S4). On the other hand, if the determination result is NO and it is determined that the curve radius is small (the road curvature is large), a value obtained by multiplying the vehicle speed Vn by a predetermined coefficient C is set as the road curvature change limit value Δχlimit (step S5). ). As shown in FIG. 6, C> B is set.

  When Δχlimit is set in steps S4 and S5, the absolute value of Δχ, which is the amount of change in curvature obtained in step S2, is compared with Δχlimit (step S6). If the absolute value of Δχ is greater than or equal to Δχlimit, the sign of Δχ is further examined (step S7). If Δχ is positive in step S7, that is, χ obtained by the image processing unit 9 at the current time step has increased by Δχlimit or more than the previous correction value χold, the value obtained by adding Δχlimit to χold is the current correction value. Set to χc (step S8). On the other hand, if Δχ is negative in step S7, that is, χ obtained by the image processing unit 9 at the current time step has decreased by Δχlimit or more than the previous correction value χold, the value obtained by subtracting Δχlimit from χold is the current value. The correction value χc is set (step S9). If it is determined in step S6 that the absolute value of Δχ is less than Δχlimit, it means that the amount of time change from the previous correction value χold of χ obtained in the image processing unit 9 is as small as ± Δχlimit. In step S10, χ obtained by the image processing unit 9 is stored in χc.

  After obtaining χc in steps S8 to S10, χold is rewritten with χc (step S11), the obtained χc is output (step S12), and the process is terminated.

  The recognition accuracy of the curve radius R obtained by the image processing unit 9 decreases as the curve radius increases. This is due to a change in the geometric relationship between the vehicle and the road, a change in the image acquisition status, and the like in addition to the resolution of the image based on the image processing. For this reason, the raw data of the curvature χ obtained from the curve radius R obtained by the image processing unit 9 changes in a vibration manner as shown by a thin line in FIG. When the steering assist torque is controlled using the curvature χ that changes in vibration as described later, the assist torque also changes in vibration, and this increases and the vehicle behavior becomes unstable, and the operation fee is increased. The ring will drop.

  Therefore, in the present invention, by applying a limit value Δχlimit to the amount of time change of the curvature, as shown by a thick line in FIG. 7, the vibration component is removed, the occurrence of inadvertent vibration is suppressed, and the vehicle behavior is suppressed. In addition to stabilization, the operation feeling is improved.

  This vibration component is more likely to occur when the curve radius / curvature recognition accuracy decreases and the curve radius is large (curvature is small). Therefore, when the curve radius is large / curvature is small, the vibration is reduced with a small limit value. When the curve radius is small / curvature is large, on the other hand, when the curve radius is small / curvature is large, the control value is improved by increasing the limit value and weakening the suppression amount of vibration component generation. ing.

  Here, the coefficient C that defines the limit value of the time change amount when the curve radius is small / curvature is large may be set to a value based on a road structure standard according to laws and regulations. This is because such a determination result exceeding the standard is considered to deviate from the actual situation.

The obtained χ c is input to a feed forward controller (F / F controller) 21 and a yaw rate ω _r related to the curve curvature χ is calculated according to a predetermined characteristic.

The yaw rate ω _d required to compensate the offset D (converge to the target value) is calculated by multiplying the deviation (D ₀ −D) between the offset D and the target offset D ₀ by the coefficient Kd.

The yaw rate ω _θ necessary for compensating the yaw angle θ (converging to the target) is calculated by multiplying the deviation (θ ₀ −θ) between the yaw angle θ and the target yaw angle θ ₀ by a coefficient K _θ. .

  The target yaw rate ω is calculated by adding the three yaw rates calculated in this way. This target yaw rate ω is converted into the target lateral acceleration G using the vehicle speed Vn detected by the vehicle speed sensor 11, and the turning amount = motor required to generate the target lateral acceleration G by the torque calculator 22. A driving torque T of 15 is calculated.

  The ECU 2 instructs the motor driver 14 to drive the motor 15 according to the obtained drive torque T. As a result, the left and right front wheels FR and FL are steered, and the vehicle 1 is turned to maintain the lane. When the vehicle 1 turns, the CCD camera 8 captures the front situation again, and the above is repeated.

  In the above description, the limit value of Δχlimit is obtained by multiplying a predetermined coefficient by the vehicle speed. The purpose of this is to compensate for the fact that the amount of time change in curvature (curve radius) changes greatly as the vehicle speed increases even when traveling on the same road. However, when the vehicle speed region to be controlled is limited, the control can be performed using a certain limit value regardless of the vehicle speed.

  In the above example, the example in which the coefficient is set in two stages has been described. However, the coefficient may be set in multiple stages, or as shown by the solid line and the broken line in FIG. It may be changed in stages. In this case, the coefficient of the limit value corresponding to the curvature or the curve radius may be stored in the change rate limiting means in the map format or the function format, and read out and set.

  Here, the case where the time change amount of the curvature is limited has been described as an example, but the time change amount of the curve radius may be limited. Since both are in a relationship that one is the reciprocal of the other, the same result can be obtained regardless of which one is limited.

  In the above description, an example of application to a steering assist device that supports traveling along a travel lane has been described. However, based on the state of an automatic steering device and a curve, braking force distribution of a brake and distribution of driving force to driving wheels are performed. The present invention can also be suitably applied to a device for controlling.

It is a lineblock diagram of vehicles 1 provided with a vehicle behavior control device of this embodiment. It is a figure explaining the acquisition condition of the driving lane by the CCD camera of this embodiment. It is a figure explaining a road parameter. It is a block diagram which shows operation | movement of lane keeping control. It is a flowchart of the change rate restriction | limiting in road parameter calculation. It is a figure which shows an example of the coefficient used for the setting of the change limit value of a road curvature. It is a figure which compares and shows the raw data of road curvature, and the data after the process by this invention. It is a figure which shows another example of the setting of the coefficient used for the setting of the change limit value of a road curvature.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... ECU, 3 ... Steering wheel, 4 ... Steering shaft, 5 ... Steering gear box, 6 ... Rack bar, 7 ... Knuckle arm, 8 ... Camera, 9 ... Image processing part, 10 ... Steering angle sensor, DESCRIPTION OF SYMBOLS 11 ... Vehicle speed sensor, 12 ... Yaw rate sensor, 13 ... Navigation system, 14 ... Motor driver, 15 ... Motor, 16 ... Warning lamp, 17 ... Alarm buzzer, 20 ... Change rate limiting means, 21 ... Feed forward controller, 22 ... Torque Arithmetic unit, 30 ... front window, 50 ... road, 51 ... travel lane, D ... offset, G ... target lateral acceleration, R ... curve radius, T ... drive torque, Vn ... vehicle speed, θ ... yaw angle, χ ... curve curvature , Ω ... Yaw rate.

Claims (5)

In a road parameter calculation device that acquires a lane image in which the host vehicle travels, recognizes the travel lane by image processing, and obtains the curvature or curve radius of the travel lane from the recognition result,
A means for limiting the time change amount of the determined road curvature or curve radius to a predetermined limit value or less and outputting as a calculation result;
The road parameter calculation device according to claim 1, wherein the limit value is set so as to be smaller when the road curvature is smaller or when the curve radius is larger. Vehicle speed detecting means for detecting the vehicle speed is further provided,
2. The road parameter calculation apparatus according to claim 1, wherein when the road curvature or the curve radius is the same, the limit value is set larger as the traveling speed of the host vehicle is higher.   3. The road parameter calculation apparatus according to claim 2, wherein the limit value is directly proportional to the traveling speed of the host vehicle when the road curvature or the curve radius is the same.   The limit value is set to a limit value based on a road structure standard when a road curvature exceeds a first curvature value or when a curve radius is less than a first curve radius. The road parameter calculation apparatus in any one of 1-3. The road parameter calculation device according to any one of claims 1 to 4,
A vehicle behavior control apparatus comprising: means for controlling vehicle behavior based on the determined road curvature.

Images