Compensation for overflight velocity when stabilizing an airborne camera
First Claim
1. A method for controlling the line of sight of a camera to remain fixed on a target, the camera being on an aircraft whose current position is moving at a velocity relative to a current position of the target, the method comprising:
- setting an initial line of sight for the camera that is aimed at the current position of the target;
calculating a transformation matrix CCE for transforming from the earth reference frame to the camera reference frame;
periodically determining a static adjustment including,calculating a position vector Δ
RE between the aircraft and the target in the earth reference frame as;
Δ
RE=RtargetE−
RaircraftE, wherein RtargetE represents the current position of the target and RaircraftE represents the current position of the aircraft,calculating a position vector Δ
RC between the aircraft and the target in the camera reference frame by transforming the position vector Δ
RE to the camera reference frame as Δ
RC=CCEΔ
RE,calculating a normalized position vector Δ
{tilde over (R)}C as wherein the normalized position vector indicates the difference between the actual line of sight of the camera and the line of sight needed to point to the target in the scan and tilt directions, andsetting the line of sight of the camera based at least in part on the normalized position vector Δ
{tilde over (R)}C;
periodically determining a dynamic adjustment including,calculating a velocity vector Δ
VE between the aircraft and the target in the earth reference frame as;
Δ
VE=VtargetE−
VaircraftE, wherein VtargetE represents the current velocity of the target and VaircraftE represents the current velocity of the aircraft,calculating a velocity vector Δ
VC between the aircraft and the target in the camera reference frame by transforming the velocity vector Δ
VE to the camera reference frame as Δ
VC=CCEΔ
VE,calculating a normalized velocity vector Δ
{tilde over (V)}C as wherein the normalized velocity vector indicates the angular velocity that the camera needs to move in the scan and tilt directions to compensate for overflight velocity, andsetting an angular velocity for moving the line of sight of the camera based at least in part on the normalized velocity vector Δ
{tilde over (V)}C;
maintaining the line of sight of the camera by combining the determined dynamic and static adjustments as the attitude of the aircraft changes relative to the current position of the target, including selling an adjustment A for the camera wherein A=Δ
{tilde over (R)}C*W+Δ
{tilde over (V)}C and wherein W represents a weighting factor based at least in part on the accuracy of the measurements used to calculate the dynamic and static adjustments.
2 Assignments
0 Petitions
Accused Products
Abstract
A method and system for maintaining the line of sight of an airborne camera fixed on a target by compensating for overflight velocity of the aircraft. The compensation system automatically commands an angular velocity of the line of sight to maintain the camera pointing at the target being overflown. This angular velocity of the line of sight is computed based upon the aircraft overflight velocity and upon a vector from the aircraft to the target. This automatic compensation for aircraft overflight velocity causes the line of sight to remain fixed upon the target. The compensation system drives a gimbal system upon which the camera is mounted to perform this compensation automatically.
-
Citations
28 Claims
-
1. A method for controlling the line of sight of a camera to remain fixed on a target, the camera being on an aircraft whose current position is moving at a velocity relative to a current position of the target, the method comprising:
-
setting an initial line of sight for the camera that is aimed at the current position of the target; calculating a transformation matrix CCE for transforming from the earth reference frame to the camera reference frame; periodically determining a static adjustment including, calculating a position vector Δ
RE between the aircraft and the target in the earth reference frame as;
Δ
RE=RtargetE−
RaircraftE, wherein RtargetE represents the current position of the target and RaircraftE represents the current position of the aircraft,calculating a position vector Δ
RC between the aircraft and the target in the camera reference frame by transforming the position vector Δ
RE to the camera reference frame as Δ
RC=CCEΔ
RE,calculating a normalized position vector Δ
{tilde over (R)}C aswherein the normalized position vector indicates the difference between the actual line of sight of the camera and the line of sight needed to point to the target in the scan and tilt directions, and setting the line of sight of the camera based at least in part on the normalized position vector Δ
{tilde over (R)}C;periodically determining a dynamic adjustment including, calculating a velocity vector Δ
VE between the aircraft and the target in the earth reference frame as;
Δ
VE=VtargetE−
VaircraftE, wherein VtargetE represents the current velocity of the target and VaircraftE represents the current velocity of the aircraft,calculating a velocity vector Δ
VC between the aircraft and the target in the camera reference frame by transforming the velocity vector Δ
VE to the camera reference frame as Δ
VC=CCEΔ
VE,calculating a normalized velocity vector Δ
{tilde over (V)}C aswherein the normalized velocity vector indicates the angular velocity that the camera needs to move in the scan and tilt directions to compensate for overflight velocity, and setting an angular velocity for moving the line of sight of the camera based at least in part on the normalized velocity vector Δ
{tilde over (V)}C;maintaining the line of sight of the camera by combining the determined dynamic and static adjustments as the attitude of the aircraft changes relative to the current position of the target, including selling an adjustment A for the camera wherein A=Δ
{tilde over (R)}C*W+Δ
{tilde over (V)}C and wherein W represents a weighting factor based at least in part on the accuracy of the measurements used to calculate the dynamic and static adjustments.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
-
-
15. A calibration system for controlling the orientation of a device to remain fixed on a target, the device being on a vehicle that is moving relative to a target, comprising:
-
a component that sets an initial line of sight for the camera that is aimed at the current position of the target; a component that calculates a transformation matrix CCE for transforming from the earth reference frame to the camera reference frame; a component that periodically determines a static adjustment by, calculating a position vector Δ
RE between the vehicle and the target in the earth reference frame as;
Δ
RE=RtargetE−
RaircraftE, wherein RtargetE represents the current position of the target and RaircraftE represents the current position of the vehicle,calculating a position vector Δ
RC between the vehicIe and the target in the camera reference frame by transforming the position vector Δ
RE to the camera reference frame as Δ
RC=CCEΔ
RE,calculating a normalized position vector Δ
{tilde over (R)}C as
wherein the normalized position vector indicates the difference between the actual line of sight of the camera and the line of sight needed to point to the target in the scan and tilt directions, andsetting the line of sight of the camera based at least in part on the normalized position vector Δ
{tilde over (R)}C;a component that periodically determines a dynamic adjustment by, calculating a velocity vector Δ
VE between the vehicle and the target in the earth reference frame as;
Δ
VE=VtargetE−
VaircraftE, wherein VtargetE represents the current velocity of the target and VaircraftE represents the current velocity of the vehicle,calculating a velocity vector Δ
VC between the vehicle and the target in the camera reference frame by transforming the velocity vector Δ
VE to the camera reference frame as Δ
VC=CCEΔ
VE,calculating a normalized velocity vector Δ
{tilde over (V)}C as
wherein the normalized velocity vector indicates the angular velocity that the camera needs to move in the scan and tilt directions to compensate for overflight velocity, andsetting an angular velocity for moving the line of sight of the camera based at least in part on the normalized velocity vector Δ
{tilde over (V)}c; anda component that maintains the line of sight of the camera by combining the determined dynamic and static adjustments as the attitude of the vehicle changes relative to the current position of the target, including setting an adjustment A for the camera wherein A=Δ
{tilde over (R)}C*W+Δ
{tilde over (V)}C and wherein W represents a weighting factor based at least in part on the accuracy of the measurements used to calculate the dynamic and static adjustments.- View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
-
Specification