JP2020046243A - Altitude measuring device, flying vehicle, altitude measuring method, and program - Google Patents

Abstract

To provide an altitude measuring device, a flying vehicle, an altitude measuring method, and a program with which it is possible to measure the altitude of a flying vehicle without installing a special measurer in the flying vehicle.SOLUTION: The altitude measuring device of an embodiment comprises an image acquisition unit, an imaging angle acquisition unit, an attitude angle acquisition unit, and an altitude derivation unit. The image acquisition unit acquires the image information of a horizontal line image imaged from the flying vehicle and including at least a horizontal line. The imaging angle acquisition unit acquires an imaging angle that is the angle formed by the attitude direction of the flying vehicle and the imaging direction. The attitude angle acquisition unit acquires an attitude angle that is the angle formed by the horizontal plane and the attitude direction of the flying vehicle. The altitude derivation unit derives, on the basis of the horizontal line image, an error angle that is the angle formed by the imaging direction and the horizontal line as seen from the imaging position of the horizontal line image, and derives the altitude of the flying vehicle on the basis of the error angle, the imaging angle and the attitude angle.SELECTED DRAWING: Figure 2

Description

  Embodiments of the present invention relate to an altitude measurement device, a flying object, an altitude measurement method, and a program.

  In order to control the flying object in the altitude direction with high accuracy, it is necessary to accurately obtain the altitude. Conventionally, altitude was calculated by integrating the acceleration of a flying object. However, it is difficult to obtain the acceleration with high accuracy, and there is also a problem of drift caused by accumulation of errors due to the integration operation. In order to solve these problems, it is conceivable to install a dedicated measuring instrument such as a radio altimeter, but since the mounting capacity of the flying object is limited, it is necessary to install a special measuring instrument for measuring altitude Was difficult.

JP-B-59-14163 JP-A-60-239684

  The problem to be solved by the present invention is to provide an altitude measuring device, a flying object, an altitude measuring method, and a program capable of measuring the altitude of the flying object without mounting a special measuring device on the flying object. To provide.

  The altitude measurement device according to the embodiment includes an image acquisition unit, an imaging angle acquisition unit, a posture angle acquisition unit, and an altitude derivation unit. The image acquisition unit acquires image information of a horizon image including at least a horizon imaged from a flying object. The imaging angle acquisition unit acquires an imaging angle, which is an angle between the attitude direction of the flying object and the imaging direction when the horizontal line image is captured. The attitude angle acquisition unit acquires an attitude angle that is an angle between a horizontal plane and the attitude direction of the flying object at the time when the horizontal line image is captured. The altitude deriving unit, based on the horizon image, derives an error angle that is an angle between the imaging direction and the direction of the horizon viewed from the imaging position of the horizon image, the error angle, the imaging angle, The altitude of the flying object is derived based on the attitude angle.

FIG. 2 is a block diagram showing a configuration example of a flying object 1 on which the altitude measurement device 40 of the embodiment is mounted. FIG. 2 is a block diagram illustrating a configuration example of an altitude measurement device 40 according to the embodiment. FIG. 4 is a diagram illustrating an error angle θerr, an imaging angle θg, and a posture angle θs according to the embodiment. FIG. 4 is a diagram illustrating a horizontal line angle θσ according to the embodiment. 5 is a flowchart illustrating an operation example of the altitude measurement device 10 of the embodiment. FIG. 9 is a block diagram showing a configuration example of an altitude measurement device 40A according to a modification of the embodiment.

  Hereinafter, an altitude measurement device, a flying object, an altitude measurement method, and a program according to an embodiment will be described with reference to the drawings. Hereinafter, a case where the flying object flies over the ocean will be described as an example, but the present invention can also be applied to a case where the flying object flies over the ground.

  FIG. 1 is a block diagram illustrating a configuration example of a flying object 1 on which the altitude measurement device 40 of the embodiment is mounted. The flying object 1 captures a target with an image seeker, for example, and follows the target direction. The flying object 1 includes, for example, an image sensor 10, an angle sensor 20, a rate sensor 30, an altitude measurement device 40, a switch (SW) 50, and a target following unit 60. The rate sensor 30 is an example of a “posture angle sensor”.

  The image sensor 10 is mounted on, for example, the tip of the flying object 1 and captures an image of a region in the flight direction. In the present embodiment, the image sensor 10 captures an image of at least a region including a horizontal line. The image captured by the image sensor 10 is an example of a “horizontal line image”. Note that the image sensor 10 may be an infrared camera or a camera using visible light.

  The angle sensor 20 is provided, for example, on a gimbal that maintains the imaging direction of the image sensor 10 in a predetermined direction, and has an imaging angle θg (FIG. 9) that is an angle between the attitude direction of the flying object 1 and the imaging direction of the image sensor 10. 3).

  The rate sensor 30 is, for example, a sensor mounted on the flying object 1 for measuring angular velocities in three axial directions. The rate sensor 30 measures an attitude angle θs (see FIG. 3), which is an angle between the horizontal plane and the attitude direction of the flying object 1.

  The altitude measurement device 40 derives the altitude of the flying object 1 based on the image captured by the image sensor 10, the imaging angle θg measured by the angle sensor 20, and the attitude angle θs measured by the rate sensor 30. . The method by which the altitude measurement device 40 derives the altitude of the flying object 1 will be described later in detail.

  The target following unit 60 includes an image captured by the image sensor 10, an imaging angle θg measured by the angle sensor 20, an attitude angle θs measured by the rate sensor 30, and a flying object measured by the altitude measurement device 40. The flying direction of the flying object 1 is controlled based on the altitude of the flying object 1. For example, if the target tracking unit 60 determines that the target cannot be recognized from the image captured by the image sensor 10, the target tracking unit 60 moves the flying object 1 in the altitude direction and searches for the target in a region having a different altitude.

  Further, the target following unit 60 controls the switch 50. The target following unit 60 opens the switch 50 when the flying object 1 satisfies the predetermined lock-on condition, and connects the switch 50 when the flying object 1 does not satisfy the predetermined lock-on condition. The predetermined lock-on state refers to, for example, a state in which the target following unit 60 has captured the target and can follow the target without using the altitude of the flying object 1. The target following unit 60 communicates with a control device that monitors the flying object 1 by radio or the like, for example, and is notified by the control device whether or not the lock-on state is established. Alternatively, when the target following unit 60 recognizes a target within a predetermined range from the image captured by the image sensor 10, the target tracking unit 60 may determine that the lock-on state is established.

  In the lock-on state, the target following unit 60 is recognized from the image based on the image captured by the image sensor 10, the imaging angle θg measured by the angle sensor 20, and the posture angle θs measured by the rate sensor 30. The flying direction of the flying object 1 is controlled in the direction of the target, and the flying object 1 follows the target.

  FIG. 2 is a block diagram illustrating a configuration example of the altitude measurement device 40 according to the embodiment. The altitude measurement device 40 includes, for example, an image acquisition unit 41, an imaging angle acquisition unit 42, a posture angle acquisition unit 43, a horizontal line angle derivation unit 44, and an altitude derivation unit 45.

  These functional units configuring the altitude measurement device 40 are realized, for example, by a processor such as a CPU executing a program (software). Some or all of these functional units may be realized by hardware such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or software. And hardware may cooperate with each other.

  The image acquiring unit 41 acquires image information from the image sensor 10 and outputs the acquired image information to the horizontal line angle deriving unit 44. The imaging angle acquisition unit 42 acquires the imaging angle θg from the angle sensor 20 and outputs the acquired imaging angle θg to the horizontal line angle derivation unit 44. The posture angle acquisition unit 43 acquires the posture angle θs from the rate sensor 30, and outputs the acquired posture angle θs to the horizontal line angle derivation unit 44.

  The horizontal line angle deriving unit 44 calculates a horizontal line angle θσ (see FIG. 4) based on the image from the image acquisition unit 41, the imaging angle θg from the imaging angle acquisition unit 42, and the posture angle θs from the posture angle acquisition unit 43. Derive. The horizontal line angle θσ is an angle between a horizontal plane passing through the flying object and a horizontal line direction looking down from the flying object 1.

  The altitude deriving unit 45 derives the altitude of the flying object 1 using the horizon angle θσ derived by the horizon angle deriving unit 44.

  A method in which the horizon angle derivation unit 44 derives the horizon angle θσ and a method in which the altitude derivation unit 45 derives the altitude of the flying object 1 will be described with reference to FIGS.

  FIG. 3 is a diagram illustrating an error angle θerr, an imaging angle θg, and a posture angle θs according to the embodiment. FIG. 3 schematically shows the flying state of the flying object 1 in the inertial coordinate system. As shown in this figure, an image sensor 10 is mounted on the tip of the flying object 1. The image sensor 10 is provided with an angle sensor 20 for measuring an imaging angle θg. A rate sensor 30 is mounted on the flying object 1, and measures the attitude angle θs. Hereinafter, an example in which an image is captured in a positional relationship having a horizontal line S in a direction forming an error angle θerr from the imaging direction will be described.

  FIG. 4 is a diagram illustrating the horizontal line angle θσ according to the embodiment. FIG. 4 schematically shows the geometric relationship among the flying object 1, the altitude h of the flying object 1, the horizontal line S, the radius R of the earth E, and the center C of the earth E as viewed from the cross section of the earth E. .

[Method by which the horizontal line angle deriving unit 44 derives the horizontal line angle θσ]
First, the horizontal line angle deriving unit 44 derives the error angle θerr based on the image from the image acquisition unit 41. As shown in this figure, the error angle θerr is the angle between the imaging direction and the horizontal line direction as viewed from the imaging position of the image.

  The horizontal line angle deriving unit 44 detects a horizontal line captured in the image. The horizontal line angle deriving unit 44 detects a contour in an image using a spatial filter used for detecting a contour such as a Sobel filter. The horizontal line angle deriving unit 44 calculates a matching degree at which the shape of the detected outline matches the shape of the previously assumed horizontal line. The horizontal line angle deriving unit 44 estimates that the matching level is equal to or more than a predetermined value and the matching level is the highest.

  The horizontal line angle deriving unit 44 detects the number of pixels corresponding to the linear distance from the image center to the horizontal line in the image. Then, the horizontal line angle deriving unit 44 obtains the angle of view of the image according to the camera parameters such as the lens characteristics and the focal length of the image sensor 10, and corresponds to the linear distance from the image center to the horizontal line based on the obtained angle of view. An angle corresponding to the number of pixels is defined as an error angle θerr.

Next, the horizontal line angle deriving unit 44 derives a horizontal line angle θσ.
As shown in FIG. 4, the horizontal line angle θσ is an angle between a horizontal plane passing through the flying object 1 and the direction of the horizontal line S looking down from the flying object 1 (imaging position). That is, the horizontal line angle θσ is an angle between the X-axis direction of the inertial coordinate system in FIG. The horizontal line angle deriving unit 44 derives the horizontal line angle θσ according to the following equation (1). Here, θσ is a horizontal line angle, θs is a posture angle, θg is an imaging angle, and θerr is an error angle.

  θσ = θs−θg−θerr (1)

[How the altitude deriving unit 45 derives the altitude of the flying object 1]
As shown in FIG. 4, the angle between the vertical direction as viewed from the flying object 1 and the vertical direction as viewed from the horizontal line S coincides with the horizontal line angle θσ due to the nature of a right triangle. That is, the relationship of the following equation (2) is established for the horizontal line angle θσ. Here, R is the radius of the earth E, and h is the altitude of the flying object 1.

  COS (θσ) = R / (R + h) (2)

The altitude deriving unit 45 derives the altitude h of the flying object 1 by solving the equation (2) for the altitude h, as shown in the following equation (3). Here, the radius R of the earth E is 6.3781 × 10 ⁶ [m].

  h = R × {1−COS (θσ)} / COS (θσ) (3)

FIG. 5 is a flowchart illustrating an operation example of the altitude measurement device 40 of the embodiment.
The altitude measurement device 40 acquires an image captured by the image sensor 10 (Step S1), and extracts a horizontal line from the acquired image (Step S2). Then, the altitude measurement device 40 calculates an error angle θerr according to the distance from the center of the image to the horizontal line in the image (step S3).

  On the other hand, the altitude measurement device 40 acquires the imaging angle θg at the time when the image is captured (Step S4). The altitude measurement device 40 acquires the posture angle θs at the time when the image is captured (step S5). Then, the altitude measurement device 40 derives the horizontal line angle θσ using the error angle θerr, the imaging angle θg, and the posture angle θs. Further, the altitude measurement device 40 derives the altitude h of the flying object 1 using the horizontal line angle θσ and the radius R of the earth E (step S7).

  Note that, in the above-described embodiment, the case where the image is acquired in the order of the image, the imaging angle θg, and the posture angle θs is exemplified, but the present invention is not limited to this. As long as each of the image, the posture angle θs, and the imaging angle θg can be acquired, the order of acquisition may be arbitrary. For example, the image, the posture angle θs, and the imaging angle θg may be acquired in this order, or the imaging angle θg, one of the image or the posture angle θs, and the other may be acquired, or the posture angle θs, the image or One of the imaging angles θg and the other may be acquired in the order of the imaging angles θg.

  As described above, the altitude measurement device 40 of the embodiment includes an image acquisition unit 41 that acquires image information of an image including at least a horizontal line, an imaging angle acquisition unit 42 that acquires an imaging angle θg, and a posture angle θs. Based on the posture angle acquisition unit 43 to be acquired and the horizontal line image, an error angle θerr which is an angle between the imaging direction and the horizontal line direction as viewed from the imaging position of the horizontal line image is derived, and the error angle θerr, the imaging angle θg, and An altitude deriving unit 45 that derives the altitude of the flying object 1 based on the attitude angle θs.

  As a result, the altitude measurement device 40 of the embodiment uses the detection values from the image sensor 10, the angle sensor 20, and the rate sensor 30, which are devices provided as standard on the flying object 1, and One altitude can be derived. That is, the altitude can be measured without mounting a special measuring device such as a radio altimeter on the flying object. Further, since the altitude measurement device 40 of the embodiment does not derive the altitude using the detection value of the acceleration sensor as in the related art, it is possible to eliminate the influence of the drift due to the acceleration sensor. In the present embodiment, since the altitude information is derived based on the angle information, the accuracy of the angle has a dominant effect on the accuracy of the altitude. For example, when the angle error is ± 0.01 [°], the altitude error is about ± 2.8 [m]. When the angle error is ± 0.1 [°], the altitude error is about ± 28 [m]. By obtaining the angle with a predetermined accuracy, the altitude can be derived with a desired accuracy.

  The flying object 1 of the embodiment includes an image sensor 10 that captures an image including at least a horizontal line from the flying object 1, an angle sensor 20 that measures an imaging angle θg, and a rate sensor 30 that measures an attitude angle θs. By providing the altitude measuring device 40 for deriving the altitude of the flying object 1 and the target tracking unit 60 for following the flying object 1 to the target, the flying object 1 is controlled in the altitude direction to search for the target. Is possible. In the flying object 1 of the embodiment, when the flying object 1 satisfies a predetermined lock-on condition, the target tracking unit 60 controls the direction of the flying object 1 without using altitude information, and The body may follow the goal. This makes it possible to reduce the load for deriving the altitude.

[Modification of Embodiment]
Next, a modified example of the embodiment will be described. In this modification, the altitude measurement device 40A determines the altitude of the flying object 1 using both the altitude derived according to the above-described embodiment and the altitude derived using the acceleration (hereinafter, referred to as an integral altitude). This is different from the above-described embodiment in the point. By determining the altitude of the flying object 1 using a plurality of altitudes derived by different techniques, the altitude can be derived more accurately. In the following description, functions different from those in the above-described embodiment will be described, and configurations equivalent to those in the above-described embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  FIG. 6 is a block diagram illustrating a configuration example of an altitude measurement device 40A according to a modification of the embodiment. The acceleration measured by the acceleration sensor 70 is input to the altitude measurement device 40A. The acceleration sensor 70 is mounted on the flying object 1 and measures the acceleration of the flying object 1 in three axial directions. The altitude measurement device 40A includes an acceleration acquisition unit 46, an integrated altitude derivation unit 47, and an integration unit 48.

  The acceleration obtaining unit 46 obtains the acceleration measured by the acceleration sensor 70 and outputs the obtained acceleration to the integrated altitude deriving unit 47. The integrated altitude deriving unit 47 derives an integrated altitude by integrating the acceleration from the acceleration acquiring unit 46 according to the following equation (4). Here, az is a vertical component of the acceleration, and is a value determined according to the measurement value of the acceleration sensor 70, the mounting angle of the acceleration sensor 70, and the attitude angle θs of the flying object 1. The attitude angle θs here may be a value measured by the rate sensor 30 or a value estimated from the attitude angle at the start of flying. At the start of the flight, the attitude angle is maintained until the flight stabilizes. Therefore, within a predetermined time from the start of the flight, the attitude angle at the start of the flight is defined as the attitude angle of the flying object 1 Can be estimated. G is the gravitational acceleration. C (0) is an integration constant, and here is the altitude at which the flying object 1 started flying.

    ∫∫ (az-g) dtdt + C (0) (4)

  The integration unit 48 determines the altitude of the flying object 1 using the altitude derived from the altitude deriving unit 45 (hereinafter, referred to as the angle altitude) and the integrated altitude derived by the integrated altitude deriving unit 47. The integrating unit 48 calculates, for example, a simple average of the angle altitude and the integrated altitude, and sets the calculated average value as the altitude of the flying object 1. Alternatively, the integrating unit 48 may weight each of the angle altitude and the integral altitude at a predetermined ratio as shown in the following equation (5) and perform an averaging operation to obtain the value as the altitude of the flying object 1. . Here, α is an arbitrary constant between 0 (zero) and 1. Also, h is the altitude of the flying object 1 determined by the integration unit 48, h1 is the angle altitude, and h2 is the integral altitude. The ratio α may be changed according to the elapsed time. For example, in the initial stage of the flight, α is set to a small value (for example, 0.1), the weight of the angle altitude is reduced, and the weight of the integral altitude is increased to determine the altitude of the flying object 1. When the flight is stabilized, α may be set to a large value (for example, 0.8), the weight of the angle altitude may be increased, and the weight of the integral altitude may be reduced. Thereby, it is possible to suppress the influence of the drift accompanying the integration at the integration altitude.

  h = α × h1 + (1−α) × h2 (5)

  In addition, the integration unit 48 may set one of the heights of the flying object 1 according to the values of the angle altitude and the integrated altitude. For example, the integration unit 48 acquires a control value of the flying direction of the flying object 1 by the target following unit 60. The integration unit 48 calculates the amount of change in each of the control value in the flight direction, the angle altitude, and the integrated altitude. For example, when the change amount of the integrated altitude is largely changed even though the change amount of the control value in the flight direction is substantially constant, the integration unit 48 generates an error due to the drift of the integrated altitude. Is determined, and the angle altitude is set as the altitude of the flying object 1.

  As described above, the altitude measurement device 40A according to the modified example of the embodiment includes an integrated altitude deriving unit 47 that derives the altitude of the flying object by integrating accelerations, and an altitude deriving unit 45 and an integrated altitude deriving unit 47. By providing an integrated unit 48 for determining the height of the flying object using the height of the flying object derived by each of them, determining the altitude of the flying object 1 using the height derived by a different method. And the altitude can be derived more accurately.

  According to at least one embodiment described above, the altitude measurement device according to the embodiment includes an image acquisition unit 41 that acquires image information of an image including at least a horizontal line, and an imaging angle acquisition unit 42 that acquires an imaging angle θg. A posture angle acquisition unit 43 that acquires the posture angle θs, and, based on the horizontal line image, derives an error angle θerr that is an angle between the imaging direction and the horizontal line direction viewed from the imaging position of the horizontal line image, and calculates the error angle θerr, An altitude deriving unit 45 that derives the altitude of the flying object 1 based on the imaging angle θg and the attitude angle θs. The altitude of the flying object 1 can be derived using the detection values from the angle sensor 20, and the rate sensor 30, and a special measuring instrument such as a radio altimeter can be provided on the flying object. Without mounting, it is possible to measure the altitude.

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Flying object, 10 ... Image sensor, 20 ... Angle sensor, 30 ... Rate sensor, 40 ... Altitude measurement device, 41 ... Image acquisition part, 42 ... Imaging angle acquisition part, 43 ... Attitude angle acquisition part, 44 ... Horizontal line Angle deriving unit, 45: altitude deriving unit, 46: acceleration obtaining unit, 47: integral altitude deriving unit, 48: integrating unit, 50: switch, 60: target following unit, 70: acceleration sensor

Claims (6)

An image acquisition unit that acquires image information of a horizon image including at least a horizon imaged from a flying object,
At the time when the horizon image is captured, an imaging angle acquisition unit that acquires an imaging angle that is an angle between the attitude direction and the imaging direction of the flying object,
At the time when the horizon image is captured, a posture angle acquisition unit that acquires a posture angle that is an angle between a horizontal plane and the posture direction of the flying object,
Based on the horizontal line image, derive an error angle that is an angle between the imaging direction and the direction of the horizontal line viewed from the imaging position of the horizontal line image, based on the error angle, the imaging angle, and the attitude angle An altitude deriving unit that derives the altitude of the flying object,
Altitude measurement device equipped with. An acceleration acquisition unit that acquires the acceleration of the flying object,
An integral altitude deriving unit that derives the altitude of the flying object by integrating the acceleration,
Using the altitude of the flying object derived by each of the altitude deriving unit and the integral altitude deriving unit, an integration unit that determines the altitude of the flying object,
The altitude measurement device according to claim 1, further comprising: An image sensor that captures a horizon image including at least a horizon from a flying object,
At the time when the horizon image is captured, an angle sensor that measures an imaging angle that is an angle between the attitude direction of the flying object and the imaging direction,
At the time when the horizon image is captured, a posture angle sensor that measures a posture angle that is an angle between a horizontal plane and a posture direction of the flying object,
The altitude of the flying object is measured using the horizontal line image captured by the image sensor, the imaging angle measured by the angle sensor, and the attitude angle measured by the attitude angle sensor. Altitude measuring device described in
The horizontal line image captured by the image sensor, the imaging angle measured by the angle sensor, the attitude angle measured by the attitude angle sensor, and the altitude of the flying object measured by the altitude measurement device Using, a target tracking unit that controls the flight direction of the flying object,
A flying object equipped with The target following unit measures the horizontal line image captured by the image sensor, the imaging angle measured by the angle sensor, and the attitude angle sensor when the self-propelled vehicle satisfies a predetermined lock-on condition. Using the attitude angle, the flying direction of the flying object is controlled to cause the flying object to follow a target,
The flying object according to claim 3. Altitude measurement device,
Image information of a horizon image including at least a horizon imaged from a flying object is acquired by an image acquisition unit,
At the time when the horizon image is captured, an imaging angle that is an angle between the attitude direction of the flying object and the imaging direction is acquired by an imaging angle acquisition unit,
At the time when the horizon image is captured, a posture angle that is an angle between a horizontal plane and the posture direction of the flying object is acquired by a posture angle acquisition unit,
Based on the horizontal line image, derive an error angle that is an angle between the imaging direction and the direction of the horizontal line viewed from the imaging position of the horizontal line image, based on the error angle, the imaging angle, and the attitude angle Derive the altitude of the flying object,
Altitude measurement method. For altitude measurement devices,
The image information of the horizon image including at least the horizon imaged from the flying object is acquired,
At the time when the horizon image is captured, an imaging angle that is an angle between the attitude direction of the flying object and the imaging direction is acquired,
At the time when the horizon image is captured, a posture angle which is an angle between a horizontal plane and the posture direction of the flying object is acquired,
Based on the horizontal line image, derive an error angle that is an angle between the imaging direction and the direction of the horizontal line viewed from the imaging position of the horizontal line image, based on the error angle, the imaging angle, and the attitude angle Deriving the altitude of the flying object,
program.

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