JP2010002334A - Road surface gradient estimating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a road surface gradient estimating device for accurately estimating a gradient angle of a road surface. <P>SOLUTION: The road surface gradient estimating device 10 for estimating the gradient angle of the road surface positioned by an own vehicle C based on a plurality of camera images due to a camera 1 includes: an extracting part 31 for extracting a static object common in each camera image as a characteristic point; a detecting part 32 for detecting a movement amount moved by the characteristic point extracted with the extracting part 31 over the plurality of the camera images; a calculating part 33 for calculating a pitch angle of the own vehicle C based on the movement amount detected with the detecting part 32; a G sensor 2 for obtaining a sensor value indicating acceleration of a vertical direction of the own vehicle C; and a correcting part 34 for calculating the gradient angle based on the sensor value obtained with the G sensor 2 and the pitch angle calculated with the calculating part 33. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a road surface gradient estimation device that estimates a gradient angle of a road surface on which a host vehicle is located.

  Conventionally, the gradient angle of the road surface on which the host vehicle is located is estimated by various methods. For example, Patent Document 1 describes that a gradient angle of a road surface is calculated and estimated by integrating detection signals obtained by an angular velocity sensor.

  On the other hand, it is also considered that the acceleration applied to the vehicle is measured by an acceleration sensor and the gradient angle is estimated based on the acceleration. Here, when front-rear pitching occurs in the vehicle, the measurement result by the acceleration sensor is affected by the pitching. Therefore, there is a possibility that the slope angle of the road surface cannot be accurately estimated using only the acceleration sensor.

For this reason, it is conceivable to detect the pitching angle of the vehicle (hereinafter referred to as the pitch angle) and then correct the measurement result by the acceleration sensor based on the pitch angle. For example, Patent Document 2 describes that a pitch angle is detected based on the width of a white line or a lane on a road surface photographed by a camera fixed to a vehicle.
JP-A-8-327378 JP-A-7-141486

  However, in the technique described in Patent Document 2, since the white line or the lane width on the road surface may not be photographed with high accuracy, the pitch angle detection result may not be robust. That is, there is a possibility that the pitch angle detection result is likely to vary. As a result, the slope angle of the road surface may not be accurately estimated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a road surface gradient estimation device that can estimate a road surface gradient angle with higher accuracy.

  That is, the road surface gradient estimation apparatus according to the present invention is a road surface gradient estimation apparatus that estimates a gradient angle of a road surface on which the host vehicle is located based on a plurality of captured images obtained by an imaging unit, and is a stationary common to each captured image. Extraction means for extracting an object as a feature point; calculation means for calculating a pitch angle of the host vehicle based on a movement amount by which the feature point extracted by the extraction unit moves over a plurality of captured images; And a detection unit that detects acceleration, and a calculation unit that calculates a gradient angle based on the vertical acceleration detected by the detection unit and the pitch angle calculated by the calculation unit.

  In the present invention, first, the extraction unit extracts a stationary object common to each captured image as a feature point, and the calculation unit calculates the pitch angle of the host vehicle based on the amount of movement of the feature point over a plurality of captured images. To do. Then, the calculating means calculates the gradient angle based on the vertical acceleration detected by the detecting means and the pitch angle.

  In this way, the pitch angle of the host vehicle is calculated based on the amount of movement of the feature points across the plurality of captured images without detecting the pitch angle based on the width of the white line or lane on the road surface, and A gradient angle is calculated based on the direction acceleration and the pitch angle. For this reason, the calculated pitch angle is less likely to vary than when the pitch angle is detected based on the width of the white line or lane on the road surface. From this, it becomes possible to estimate the gradient angle of the road surface with higher accuracy.

  The calculating means detects the movement amount of the feature point and calculates the pitch angle based on the movement amount when the number of captured images from which the feature point has been extracted by the extracting means is equal to or greater than a predetermined number. Is also preferable. As a result, a stationary object that is common to a predetermined number or more of the captured images is extracted as a feature point, so that the amount of movement of the feature point can be accurately detected.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the road surface gradient estimation apparatus which can estimate the road surface gradient angle more accurately.

  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 understanding of the description, the same components in the drawings are denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  First, the configuration of a road surface gradient estimation apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a road surface gradient estimation apparatus 10 according to the present embodiment.

  The road surface gradient estimation device 10 is attached to the host vehicle C (for example, a passenger car), and estimates the gradient angle of the road surface on which the host vehicle C is located based on a plurality of camera images (captured images) by the camera 1 (imaging means). It is a device to do. More specifically, the road surface gradient estimation device 10 extracts feature points in a plurality of camera images, detects the movement amount of the feature points, and calculates the pitch angle of the road surface based on the movement amount. The road surface gradient estimation device 10 is based on the vertical acceleration (or the road surface gradient angle based on this acceleration) of the host vehicle C measured by an acceleration sensor (hereinafter referred to as G sensor) and the pitch angle. To calculate the gradient angle.

  The road surface gradient estimation device 10 includes a camera 1, a G sensor 2 (detection means), and an ECU 3 (abbreviation of Electronic Control Unit, that is, an electronic control device) connected to each of the camera 1 and the G sensor 2. Note that the host vehicle C to which the road surface gradient estimation device 10 is attached includes various sensors 4 to 6 connected to the ECU 3 and a brake 7.

  Here, the ECU 3 includes an extraction unit 31 (extraction unit), a detection unit 32 (calculation unit), a calculation unit 33 (calculation unit), and a correction unit 34 (calculation unit). The functions of the extraction unit 31, the detection unit 32, the calculation unit 33, and the correction unit 34 are realized by the ECU 3. The ECU 3 is a unit whose main component is a microcomputer including a CPU, a ROM, a RAM, and the like. The various sensors 4 to 6 are the steering angle sensor 4, the wheel speed sensor 5, and the brake pressure sensor 6. The brake pressure sensor 6 is connected to the brake 7.

  The camera 1 is a fish-eye camera using a semiconductor element such as a CCD or a CMOS, and has a relatively wide angle lens. For this reason, the camera 1 can acquire a camera image by performing wide-angle imaging of the periphery of the host vehicle C. For example, the camera 1 faces a direction in which the road surface gradient estimation device 10 estimates the road surface gradient angle. The direction in which the gradient angle of the road surface is estimated is not particularly limited. For example, the direction is the forward direction of the host vehicle C (that is, the direction from the ECU 3 to the camera 1 in FIG. 1) (that is, the extraction unit 31 in FIG. 1). When detecting the pitch angle around the axis in the direction from the correction unit 34 to the correction unit 34), the camera 1 moves the vehicle C forward, backward, or laterally (that is, from the extraction unit 31 to the correction unit 34 in FIG. 1). (However, it is oriented in a direction perpendicular or parallel to the axis in the direction from the extraction unit 31 to the correction unit 34 in FIG. 1). Data of the camera image acquired by the camera 1 is transmitted to the extraction unit 31 of the ECU 3.

  The G sensor 2 is a behavior observation sensor that periodically measures the vertical acceleration of the host vehicle C (for example, the center of gravity of the host vehicle C) and acquires a sensor value indicating the acceleration. The G sensor 2 measures accelerations (including gravitational acceleration) in all directions such as the vertical direction of the host vehicle C (that is, the direction penetrating the paper surface of FIG. 1) and the horizontal direction (that is, the direction parallel to the paper surface of FIG. 1). be able to. Usually, the direction of acceleration measured by the G sensor 2 is the vertical direction of the host vehicle C. The G sensor 2 may perform calculation of the gradient angle based on the sensor value after acquiring the sensor value.

  The extraction unit 31 is a part that extracts a stationary object common to each camera image as a feature point and stores it in the ECU 3 with respect to a plurality of camera images acquired by the camera 1. A feature point is a characteristic point determined by the ECU 3 to match an image pattern stored in advance in the ROM or RAM of the ECU 3. The ECU 3 performs template matching based on a comparison of luminance for each pixel in which the camera image and the image pattern correspond to each other. An image pattern is a pattern of stationary objects that can be patterned, such as traffic lights, signs, and buildings. Note that the image pattern may not be stored in advance in the ROM or RAM of the ECU 3, and in this case, the vehicle C can be acquired from a database in a storage device outside the vehicle by using communication means that can communicate with the outside of the vehicle. You may comprise.

  The detection unit 32 is a part that detects the amount of movement (that is, the movement distance) that the feature point extracted by the extraction unit 31 moves over a plurality of camera images and stores it in the ECU 3. The detection unit 32 calculates a change amount related to the movement of the feature point in the vertical direction or the like in the camera image within a predetermined number (that is, within a predetermined time). For example, when the moving direction of the feature point has an upward component in the camera image, the amount of movement is calculated along with the magnitude of the upward component as + (plus), while the downward component If this is the case, the downward component is-(minus) and calculated along with the size of the component. When there are a plurality of feature points common to a plurality of camera images, a movement amount is calculated for each feature point.

  The calculation unit 33 is a part that calculates the pitch angle of the host vehicle C based on the movement amount detected by the detection unit 32 and stores it in the ECU 3. For example, with respect to each feature point, the calculation unit 33 assumes that the pitch angle is 0 (zero) when the movement amount is 0 (zero), and the pitch angle becomes-(+) as the movement amount increases in the + (plus) direction. It may be calculated that the pitch angle becomes smaller in the minus direction, and the pitch angle becomes larger in the plus (plus) direction as the movement amount becomes smaller in the minus (minus) direction.

  The correction unit 34 calculates the gradient angle based on the sensor value acquired by the G sensor 2 (or the gradient angle of the road surface based on this sensor value) and the pitch angle calculated by the calculation unit 33 and stores it in the ECU 3. It is a part to be made. More specifically, the correcting unit 34 subtracts the pitch angle calculated by the calculating unit 33 from the sensor value acquired by the G sensor 2 (or the gradient angle of the road surface based on the sensor value), thereby obtaining the pitch of the sensor value. Perform correction based on corners. A value obtained as a result of the correction operation performed by the correction unit 34 is calculated as an estimation result of the gradient angle by the road surface gradient estimation device 10. In addition, the correction | amendment part 34 may perform the further correction | amendment based on the data transmitted from the below-mentioned various sensors 4-6.

  The steering angle sensor 4 is a sensor that detects the direction of the wheel (for example, the front wheel) of the host vehicle C. Data on the direction of the wheel detected by the steering angle sensor 4 is transmitted to the ECU 3.

  The wheel speed sensor 5 is a sensor that detects the rotational speed of the wheel (for example, the front wheel) of the host vehicle C. Data regarding the rotational speed detected by the wheel speed sensor 5 is transmitted to the ECU 3.

  The brake pressure sensor 6 is a sensor that detects a pressure when the brake 7 is depressed. Data regarding the pressure detected by the brake pressure sensor 6 is transmitted to the ECU 3.

  Next, a series of processes executed by the road surface gradient estimation apparatus 10 will be described with reference to FIG. FIG. 2 is a flowchart for explaining a series of processes executed by the road surface gradient estimation apparatus 10. The processing shown in the flowchart of FIG. 2 is mainly performed by the camera 1, the G sensor 2, and the ECU 3, and at a predetermined timing from when the road surface gradient estimation device 10 is turned on until it is turned off. Repeatedly executed.

  First, the ECU 3 acquires an image pattern from the ROM or RAM (step S01). Then, the camera 1 captures a wide-angle image of the periphery of the host vehicle C and acquires a camera image (step S02).

  Next, the extraction part 31 extracts the stationary object common to each camera image as a feature point using an image pattern regarding the several camera image acquired by the camera 1 (step S03). Then, the detection unit 32 determines whether or not the number of camera images subjected to the extraction process by the extraction unit 31 is equal to or greater than a predetermined number (that is, a set number set in advance in the ECU 3) (step S04). . If a predetermined number or more of camera images have not yet been processed, the process returns to step S03 and proceeds. On the other hand, if a predetermined number or more of camera images have already been processed, the process proceeds to step S05 described later.

  In step S05, the detection unit 32 detects the amount of movement of the feature points extracted by the extraction unit 31 within a certain time over a plurality of camera images (step S05). And the calculation part 33 calculates the pitch angle of the own vehicle C based on the movement amount detected by the detection part 32 (step S06). Next, the correction unit 34 calculates a gradient angle based on the sensor value acquired by the G sensor 2 (or the road surface gradient angle based on the sensor value) and the pitch angle calculated by the calculation unit 33 (that is, Correction calculation based on the pitch angle of the sensor value is performed (step S07). And the value of the result calculated by the correction | amendment part 34 is calculated as an estimated value of the gradient angle by the road surface gradient estimation apparatus 10 (step S08).

  Continuously, the effect of this embodiment is demonstrated. According to this embodiment, first, the extraction unit 31 extracts a stationary object common to each camera image as a feature point, and the detection unit 32 detects the amount of movement of the feature point over a plurality of camera images. Then, the calculation unit 33 calculates the pitch angle of the host vehicle C based on the amount of movement, and uses the sensor value acquired by the G sensor 2 (or the gradient angle of the road surface based on the sensor value) and the pitch angle. Based on this, the correction unit 34 calculates the gradient angle, and this calculation result is used as the estimated value of the gradient angle.

  Thus, without detecting the pitch angle based on the width of the white line or lane on the road surface, the pitch angle of the host vehicle C is calculated based on the amount of movement of the feature point across the plurality of camera images, and The gradient angle is calculated based on the sensor value acquired by the G sensor 2 (or the gradient angle of the road surface based on the sensor value) and the pitch angle, and the calculation result becomes the estimated value of the gradient angle. For this reason, the calculated pitch angle is less likely to vary than when the pitch angle is detected based on the width of the white line or lane on the road surface. From this, it becomes possible to estimate the gradient angle of the road surface with higher accuracy.

  Furthermore, since a stationary object common to a predetermined number or more of camera images is extracted as a feature point, the amount of movement of the feature point can be detected with high accuracy.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments. For example, in the above embodiment, the ECU 3 includes the extraction unit 31, the detection unit 32, the calculation unit 33, and the correction unit 34. However, these may be configured separately and independently.

1 is a schematic configuration diagram of a road surface gradient estimation apparatus according to the present embodiment. It is a flowchart for demonstrating a series of flows of the process performed with a road surface gradient estimation apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Camera, 2 ... G sensor, 3 ... ECU, 4 ... Steering angle sensor, 5 ... Wheel speed sensor, 6 ... Brake pressure sensor, 7 ... Brake, 10 ... Road surface gradient estimation apparatus, 31 ... Extraction part, 32 ... Detection Part, 33 ... calculating part, 34 ... correcting part, C ... own vehicle.

Claims (2)

A road surface gradient estimation device that estimates a gradient angle of a road surface on which the host vehicle is located based on a plurality of captured images by an imaging unit,
Extraction means for extracting a stationary object common to each captured image as a feature point;
Calculating means for calculating a pitch angle of the host vehicle based on a movement amount by which the feature points extracted by the extracting means move across the plurality of captured images;
Detecting means for detecting acceleration in the vertical direction of the host vehicle;
A computing means for computing the gradient angle based on the vertical acceleration detected by the detecting means and the pitch angle calculated by the calculating means;
A road surface gradient estimation device comprising: When the number of captured images from which the feature points have been extracted by the extraction unit is equal to or greater than a predetermined number, the calculation unit detects the movement amount of the feature points and calculates the pitch angle based on the movement amount. The road surface gradient estimation device according to claim 1, wherein the road surface gradient estimation device is calculated.

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