Tether-based wind estimation
A method includes causing an aerial vehicle to deploy a tethered component to a particular distance beneath the aerial vehicle by releasing a tether connecting the tethered component to the aerial vehicle. The method also includes obtaining, from a camera connected to the aerial vehicle, image data that represents the tethered component while the tethered component is deployed to the particular distance beneath the aerial vehicle. The method additionally includes determining, based on the image data, a position of the tethered component within the image data. The method further includes determining, based on the position of the tethered component within the image data, a wind vector that represents a wind condition present in an environment of the aerial vehicle. The method yet further includes causing the aerial vehicle to perform an operation based on the wind vector.
1 . A computer-implemented method comprising:
causing an aerial vehicle to deploy a tethered component to a particular distance beneath the aerial vehicle by releasing a tether connecting the tethered component to the aerial vehicle;
obtaining, from a camera connected to the aerial vehicle, a plurality of images that are captured at a plurality of different times and represent the tethered component while the tethered component is deployed to the particular distance beneath the aerial vehicle;
determining, for each respective image of the plurality of images, a corresponding location of the tethered component within the respective image;
determining, based on the corresponding location of the tethered component within each respective image of the plurality of images, an average location of the tethered component over the plurality of different times;
determining, based on the average location of the tethered component, a wind vector that represents a wind condition present in an environment of the aerial vehicle; and
causing the aerial vehicle to perform an operation based on the wind vector.
2 . The computer-implemented method of claim 1 , wherein determining the corresponding location of the tethered component within the respective image comprises:
determining a corresponding location of a centroid of the tethered component within the respective image.
3 . The computer-implemented method of claim 1 , wherein causing the aerial vehicle to perform an operation based on the wind vector comprises:
adjusting at least one of a position or an orientation of the aerial vehicle in the environment based on the wind vector.
4 . The computer-implemented method of claim 1 , wherein determining the wind vector comprises:
determining a pixel distance between (i) the average location of the tethered component and (ii) a reference position associated with the plurality of images, wherein the reference position is expected to represent the tethered component in the absence of wind.
5 . The computer-implemented method of claim 4 , wherein determining the wind vector further comprises:
determining, based on the pixel distance, a field of view of the camera, and a resolution of the camera, a wind-induced angle formed between (i) the tethered component and (ii) a vertical line coincident with the reference position; and
determining the wind vector based on the wind-induced angle and one or more of (i) a weight of the tethered component, (ii) a density of air in the environment, (iii) a drag coefficient of the tethered component, or (iv) an area of a surface of the tethered component facing the wind vector.
6 . The computer-implemented method of claim 5 , wherein determining the wind-induced angle comprises:
determining the wind-induced angle further based on the particular distance to which the tethered component is deployed beneath the aerial vehicle.
7 . The computer-implemented method of claim 1 , wherein determining the wind vector comprises:
selecting the wind vector from a predetermined mapping that corresponds to the tethered component, wherein the predetermined mapping comprises, for each respective distance of one or more distances to which the tethered component is deployable beneath the aerial vehicle, a mapping between (i) a plurality of possible positions of the tethered component within the plurality of images and (ii) a plurality of possible wind vectors.
8 . The computer-implemented method of claim 7 , wherein:
the predetermined mapping comprises:
a first mapping between (i) a first plurality of possible vertical positions of the tethered component within the plurality of images and (ii) a first plurality of possible wind velocities along a first axis; and
a second mapping between (i) a second plurality of possible horizontal positions of the tethered component within the plurality of images and (ii) a second plurality of possible wind velocities along a second axis; and
selecting the wind vector from the predetermined mapping comprises:
selecting a first wind vector component using the first mapping;
selecting a second wind vector component using the second mapping; and
determining the wind vector based on the first wind vector component and the second wind vector component.
9 . The computer-implemented method of claim 1 , wherein the tethered component comprises a payload coupling apparatus configured to couple a payload to the tether.
10 . The computer-implemented method of claim 1 , wherein the tethered component comprises one or more of:
reflective paint configured to reflect light from the tethered component towards the camera to increase a visibility of the tethered component within the plurality of images;
a light emitter configured to emit light toward the camera, wherein the camera is configured to capture the plurality of images while the light emitter emits the light towards the camera;
a fiducial marker disposed on the tethered component, wherein determining the corresponding location of the tethered component within the respective image comprises detecting the fiducial marker within the respective image; or
a particular shape of the tethered component, and wherein determining the corresponding location of the tethered component within the respective image comprises detecting the particular shape within the respective image.
11 . The computer-implemented method of claim 1 , wherein the aerial vehicle further comprises a light emitter configured to emit light toward the tethered component, and wherein the camera is configured to capture each respective image of the plurality of images while the light emitter emits the light towards the tethered component.
12 . The computer-implemented method of claim 1 , wherein the particular distance beneath the aerial vehicle to which the tethered component is deployed is selected based on one or more of:
a size of the tethered component such that the tethered component is detectable within the plurality of images;
a field of view of the camera such that, when displaced by the wind vector, the tethered component is expected to be positioned within the field of view of the camera;
an extent of downwash generated by a propeller of the aerial vehicle;
damping of the tethered component at the particular distance; or
a likelihood of the tethered component, when deployed at the particular distance, striking the propeller of the aerial vehicle during movements of the aerial vehicle.
13 . The computer-implemented method of claim 1 , further comprising:
causing the aerial vehicle to attempt to hover in a fixed location while obtaining the plurality of images.
14 . The computer-implemented method of claim 1 , wherein determining the wind vector comprises:
determining a location change in the corresponding location of the tethered component across two or more images of the plurality of images; and
determining, based on the location change, at least one of (i) a wind speed change or (ii) a confidence value associated with the wind vector.
15 . A system comprising a processor configured to perform operations comprising:
causing an aerial vehicle to deploy a tethered component to a particular distance beneath the aerial vehicle by releasing a tether connecting the tethered component to the aerial vehicle;
obtaining, from a camera connected to the aerial vehicle, a plurality of images that are captured at a plurality of different times and represent the tethered component while the tethered component is deployed to the particular distance beneath the aerial vehicle;
determining, for each respective image of the plurality of images, a corresponding location of the tethered component within the respective image;
determining, based on the corresponding location of the tethered component within each respective image of the plurality of images, an average location of the tethered component over the plurality of different times;
determining, based on the average location of the tethered component, a wind vector that represents a wind condition present in an environment of the aerial vehicle; and
causing the aerial vehicle to perform an operation based on the wind vector.
16 . The system of claim 15 , wherein determining the corresponding location of the tethered component within the respective image comprises:
determining a corresponding location of a centroid of the tethered component within the respective image.
17 . The system of claim 15 , wherein determining the wind vector comprises:
determining a pixel distance between (i) the average location of the tethered component and (ii) a reference position associated with the plurality of images, wherein the reference position is expected to represent the tethered component in the absence of wind.
18 . A non-transitory computer-readable medium having stored thereon instructions that, when executed by a computing system, cause the computing system to perform operations comprising:
causing an aerial vehicle to deploy a tethered component to a particular distance beneath the aerial vehicle by releasing a tether connecting the tethered component to the aerial vehicle;
obtaining, from a camera connected to the aerial vehicle, a plurality of images that are captured at a plurality of different times and represent the tethered component while the tethered component is deployed to the particular distance beneath the aerial vehicle;
determining, for each respective image of the plurality of images, a corresponding location of the tethered component within the respective image;
determining, based on the corresponding location of the tethered component within each respective image of the plurality of images, an average location of the tethered component over the plurality of different times;
determining, based on the average location of the tethered component, a wind vector that represents a wind condition present in an environment of the aerial vehicle; and
causing the aerial vehicle to perform an operation based on the wind vector.
19 . The system of claim 17 , wherein determining the wind vector further comprises:
determining, based on the pixel distance, a field of view of the camera, and a resolution of the camera, a wind-induced angle formed between (i) the tethered component and (ii) a vertical line coincident with the reference position; and
determining the wind vector based on the wind-induced angle and one or more of (i) a weight of the tethered component, (ii) a density of air in the environment, (iii) a drag coefficient of the tethered component, or (iv) an area of a surface of the tethered component facing the wind vector.
20 . The system of claim 15 , wherein determining the wind vector comprises:
selecting the wind vector from a predetermined mapping that corresponds to the tethered component, wherein the predetermined mapping comprises, for each respective distance of one or more distances to which the tethered component is deployable beneath the aerial vehicle, a mapping between (i) a plurality of possible positions of the tethered component within the plurality of images and (ii) a plurality of possible wind vectors.