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The visual tracking control system can be used in surveillance
motion of an unmanned driving plane and in the monitoring system
on boats to track surface objects. Also, it can be utilized in
automatic driving of an unmanned vehicle and in robot''s assembly
operation on a moving conveyor. To attain tracking control, it
must be done as follow. First, the vision system needs to
recognize a moving object from background. Second, the visual
servo control must keep the object motionless in the image
plane. To idenify the moving object, we detect the object
through a series consecutive images acquired by a camera and
estimate the position and velocity of the moving object. Then we
control a servo motor to align the camera with the interested
object in the picture frame. As the object is fixed in the
frame, we can enlarge the image to recognize the shape of the
target.This context presents an integrated control structure
including a visual sensory subsystem of image processing and a
servo control subsystem. The image ocessing subsystem uses the
windowing and the subsample method to accelerate the processing
speed. Meanwhile the servo control subsystem uses an image-based
feedback control to manipulate the motion of the camera to keep
the object in the center of image plane avoiding the task of
finding the object position in the world coordinate and the
environment calibration procedure. From our experiment setup,
in which a camera tracks a swinging ping-pong ball, the sy stem
response can attain near real time speed. Experiment results
show automatic tracking of a surface target with a vision sensor
is feasible and effective.
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