Determining control parameters for formation of multiple UAVs
According to a first aspect, it is provided a method for determining control parameters for controlling flight of a formation comprising at least two physically connected UAVs. The method is performed in a controller device and comprising the steps of: determining UAVs forming part of the formation; controlling each one of the UAVs, in sequence, to perform a lift off procedure in which the UAV lifts off ground and lands on ground; acquiring, for each lift off procedure, inertial data from Inertial Measurement Units, IMUs, of each one of the UAVs of the formation; estimating UAV connection parameters for each possible pair of UAVs of the formation based on the inertial data, the UAV connection parameter comprising at least one of relative orientation, absolute orientations and distance between the UAVs of the pair; and determining control parameters for controlling flight of the formation based on the estimated connection parameters.
1 . A method for controlling flight of a formation comprising at least two Unmanned Aerial Vehicles, UAVs, physically connected to each other, the method being performed in a controller device and comprising:
determining UAVs located on ground, wherein the UAVs are rigidly connected to each other with a fixed distance between each other, when forming part of, and maintaining a formation;
controlling each one of the UAVs to perform a respective lift off procedure in sequence, while maintaining the formation and the fixed distance between each other, each lift off procedure comprising that a respective UAV lifts off ground after which it lands on ground all while the other one or more UAVs remain on the ground during each lift off procedure;
acquiring, concurrently with each lift off procedure, when a respective UAV lifts off ground, inertial data from Inertial Measurement Units, IMUs, of each one of the UAVs of the formation;
estimating UAV connection parameters for each possible pair of UAVs of the formation based on the inertial data, acquired concurrently with each lift off procedure, the UAV connection parameter comprising at least one of relative orientation, absolute orientations and distance between the UAVs of the pair; and
controlling flight of each UAV of the formation, based on the connection parameters, estimated during the lift off procedures, while maintaining the formation.
2 . The method according to claim 1 , further comprising:
filtering the acquired inertial data, yielding filtered inertial data;
and wherein the UAV connection parameters are estimated based on the filtered inertial data.
3 . The method according to claim 2 , wherein the filtering comprises filtering to reduce bias.
4 . The method according to claim 2 , wherein the filtering comprises filtering to reduce drifting errors.
5 . The method according to claim 1 , wherein the acquiring comprises, for at least one of the UAVs, acquiring visual data from a visual sensor of the UAV, and wherein the AV connection parameters are estimated based on the visual data.
6 . The method according to claim 5 , wherein the filtering is based on the visual data.
7 . The method according to claim 5 , wherein the acquiring comprises acquiring visual data for all UAVs, respectively.
8 . The method according to claim 5 , further comprising comparing visual features of the visual data with a map containing visual features and their positions.
9 . The method according to claim 1 , wherein the estimating of UAV connection parameters comprises estimating relative orientation based on estimations of individual attitude of each UAV derived from its acceleration and angular velocity data of the inertial data.
10 . The method according to claim 9 , wherein the estimating comprises estimating a position of each UAV by double integrating acceleration, and wherein the distance between the UAVs of the pair is estimated based on the estimations of the individual attitude, estimations of position of each UAV of the UAVs of the pair, and an estimation of relative orientation between the UAVs of the pair.
11 . The method according to claim 1 , wherein all UAVs of the formation form part of a single plane.
12 . A controller device for controlling flight of a formation comprising at least two Unmanned Aerial Vehicles, UAVs, physically connected to each other, the controller device comprising:
a processor; and
a memory storing instructions that, when executed by the processor, cause the controller device to:
determine UAVs located on ground, wherein the UAVs are rigidly connected to each other with a fixed distance between each other, when forming part of, and maintaining a formation;
control each one of the UAV to perform a respective lift off procedure in sequence, while maintaining the formation and the fixed distance between each other, each lift off procedure comprising that a respective UAV lifts off ground after which it lands on ground all while the other one or more UAVs remain on ground during each lift off procedure;
acquire, concurrently with each lift off procedure, when a respective UAV lifts off ground, inertial data from Inertial Measurement Units, IMUs, of each one of the UAVs of the formation;
estimate UAV connection parameters for each possible pair of UAVs of the formation based on the inertial data, acquired concurrently with each lift off procedure, the UAV connection parameter comprising at least one of relative orientation, absolute orientations and distance between the UAVs of the pair; and
control flight of each UAV of the formation, based on the connection parameters, estimated during the lift off procedures, while maintaining the formation.
13 . The controller device according to claim 12 , further comprising instructions that, when executed by the processor, cause the controller device to:
filter the acquired inertial data, yielding filtered inertial data;
and wherein the instructions to estimate UAV connection parameters comprise instructions that, when executed by the processor, cause the controller device to estimate UAV connection parameters based on the filtered inertial data.
14 . The controller device according to claim 13 , wherein the instructions to filter comprise instructions that, when executed by the processor, cause the controller device to filter to reduce bias.
15 . The controller device according to claim 13 , wherein the instructions to filter comprise instructions that, when executed by the processor, cause the controller device to filter to reduce drifting errors.
16 . The controller device according to claim 12 , wherein the instructions to acquire comprise instructions that, when executed by the processor, cause the controller device to acquire, for at least one of the UAVs, visual data from a visual sensor of the UAV, and wherein the estimating UAV connection parameters is based on the visual data.
17 . The controller device according to claim 16 , wherein the filtering is based on the visual data.
18 . The controller device according to claim 16 , wherein the instructions to acquire comprise instructions that, when executed by the processor, cause the controller device to acquire visual data for all UAVs, respectively.
19 . The controller device according to claim 16 , further comprising instructions that, when executed by the processor, cause the controller device to compare visual features of the visual data with a map containing visual features and their positions.
20 . The controller device according to claim 12 , wherein the instructions to estimate UAV connection parameters comprise instructions that, when executed by the processor, cause the controller device to estimate relative orientation based on estimations of individual attitude of each UAV derived from its acceleration and angular velocity data of the inertial data.
21 . The controller device according to claim 20 , wherein the instructions to estimate comprise instructions that, when executed by the processor, cause the controller device to estimate a position of each UAV by double integrating acceleration, and to estimate the distance between the UAVs of the pair based on the estimations of the individual attitude, estimations of position of each UAV of the UAVs of the pair, and an estimation of relative orientation between the UAVs of the pair.
22 . The controller device according to claim 12 , wherein all UAVs of the formation form part of a single plane.
23 . A computer program for controlling flight of a formation comprising at least two Unmanned Aerial Vehicles, UAVs, physically connected to each other, the computer program comprising computer program code which, when run on a controller device causes the controller device to:
determine UAVs located on ground, wherein the UAVs are rigidly connected to each other with a fixed distance between each other, when forming part of, and maintaining a formation;
control each one of the UAV to perform a respective lift off procedure in sequence, while maintaining the formation and the fixed distance between each other, each lift off procedure comprising that a respective UAV lifts off ground after which it lands on ground all while the other one or more UAVs remain on the ground during each lift off procedure;
acquire, concurrently with each lift off procedure, when a respective UAV lifts off ground, inertial data from Inertial Measurement Units, IMUs, of each one of the UAVs of the formation;
estimate UAV connection parameters for each possible pair of UAVs of the formation based on the inertial data, acquired concurrently with each lift off procedure, the UAV connection parameter comprising at least one of relative orientation, absolute orientations and distance between the UAVs of the pair; and
control flight of each UAV of the formation based on the connection parameters, estimated during the lift off procedures, while maintaining the formation.
24 . A computer program product comprising a computer program according to claim 23 and a computer readable means on which the computer program is stored.