Scarica (PDF – 6.19 MB)

Figure 17: The Sick LMS200 laser sensor.
(0.25 ◦ , 0.5 ◦ , 1 ◦ ) and maximum scan angle (100 ◦ /180 ◦ ). Each scan is
executed in clockwise mode. Measurement data are available in real
time for further evaluation via RS232/RS422 serial interface.
Laser sensors are usually very accurate (each distance measure has
an accuracy of some millimeters) and reliable. Though, they can be
deceived by transparent or very dark surfaces, which do not adequately
reflect laser light to the receiver, and generate outliers. Besides, laser
sensors obviously cannot detect objects which do not intersect their
scan plane.
Stereo cameras The STH-MDCS2-VAR-C (figure 18) is a low power
compact digital stereo camera system, which can be connected to a PC
via IEEE 1394. Each camera has a resolution of 1.3 megapixel, and it
is equipped with a fixed focus lens (4.5 mm). The CCD sensors of the
cameras provide a good noise immunity. Capturing parameters (e.g.
exposure gain, frame rate, resolution) are adjustable.
The cameras are mounted on a rigid support, which permits to set
the cameras baseline to any value in the range 5-20 cm. Their optical
axes are maintained parallel. The cameras are positioned on the top
layer of the robot, about 95 cm above the ground. They are pointed
towards the direction in front of the robot, and they are slightly tilted
towards the ground.
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