[Studies in Computational Intelligence 481] Artur Babiarz, Robert Bieda, Karol Jędrasiak, Aleksander Nawrat (auth.), Aleksander Nawrat, Zygmunt Kuś (eds.) - Vision Based Systemsfor UAV Applications (2013, Sprin

Object Tracking for Rapid Camera Movements in 3D Space 63
According to figure 6 we assume the following terms:
- the angle of a camera deviation from the vertical direction when the camera
is directed towards the object (before distortion) ;
- the angle of a camera deviation from the vertical direction when the camera
is not directed towards the object (after distortion);
When the first step of control algorithm is performed and the camera is set in an
(x, y) plane towards an object then it is possible to calculate a correction
angle in an plane. The location of the camera and the object on an
S plane after the correction on an (x, y) plane is presented in figure 7.
According to figure 7 we assume the following terms:
- the angle in a projection on the plane which defines direction towards the
object;
- the angle of a camera rotation in a projection on the plane which compensates
distortion.
The camera settings changes, which will occur after distortion, aim at turning the
camera head in such a way which allows the object to appear in the camera field
of view. Similarly, as it was presented in [25], we assume that when the object is
in the center of the field of view then 0 otherwise 0. is
a signal produced by the image processing system. Hence we assume that in the
moment of object position computing ( 0) the object is directly in the
axis of the camera. The first step of control algorithm comprises of computing of
the object location before distortion. The position of the object , , is calculated
on the basis of rangefinder data (distance d), GPS[30] and IMU
, , , , :
· sin 90°
· cos 90° 0°, 180° (1.1)
· sin 90°
· cos 90° 0°, 180° (1.2)
As was it mentioned above, it is assumed that during object position calculation
the object is in the center of the field of view. The aforementioned calculations are
processed during the helicopter flight when 0. The manifestation of
distortion is the loss of the object in the picture and considerable changes of the
object position or orientation. Then the helicopter control system turns the helicopter
to a nearly horizontal position. Afterwards , , , , are measured.
The goal of the control algorithm is to turn the camera towards the object.
Required values of camera tilt angles and are calculated on the basis of
the object and camera positions. These angles are calculated by the equations
stated below: