Sensors and Methods for Mobile Robot Positioning
Sensors and Methods for Mobile Robot Positioning
Sensors and Methods for Mobile Robot Positioning
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Chapter 4: <strong>Sensors</strong> <strong>for</strong> Map-Based <strong>Positioning</strong> 107<br />
4.1.2.2 RIEGL Laser Measurement Systems<br />
RIEGL Laser Measurement Systems, Horn, Austria, offers a number of commercial products (i.e.,<br />
laser binoculars, surveying systems, “speed guns,” level sensors, profile measurement systems, <strong>and</strong><br />
tracking laser scanners) employing short-pulse TOF laser ranging. Typical applications include lidar<br />
altimeters, vehicle speed measurement <strong>for</strong> law en<strong>for</strong>cement, collision avoidance <strong>for</strong> cranes <strong>and</strong><br />
vehicles, <strong>and</strong> level sensing in silos. All RIEGL products are distributed in the United States by<br />
RIEGEL USA, Orl<strong>and</strong>o, FL.<br />
LD90-3 Laser Rangefinder<br />
The RIEGL LD90-3 series laser rangefinder (see Figure 4.16) employs a near-infrared laser diode<br />
source <strong>and</strong> a photodiode detector to per<strong>for</strong>m TOF ranging out to 500 meters (1,640 ft) with diffuse<br />
surfaces, <strong>and</strong> to over 1,000 meters (3,281 ft) in the case of co-operative targets. Round-trip<br />
propagation time is precisely measured by a quartz-stabilized clock <strong>and</strong> converted to measured<br />
distance by an internal microprocessor using one of two available algorithms. The clutter suppression<br />
algorithm incorporates a combination of range measurement averaging <strong>and</strong> noise rejection<br />
techniques to filter out backscatter from airborne particles, <strong>and</strong> is there<strong>for</strong>e useful when operating<br />
under conditions of poor visibility [Riegl, 1994]. The st<strong>and</strong>ard measurement algorithm, on the other<br />
h<strong>and</strong>, provides rapid range measurements without regard <strong>for</strong> noise suppression, <strong>and</strong> can subsequently<br />
deliver a higher update rate under more favorable environmental conditions. Worst-case range<br />
measurement accuracy is ±5 centimeters (±2 in), with typical values of around ±2 centimeters (±0.8<br />
in). See Table 4.8 <strong>for</strong> a complete listing of the LD90-3's features.<br />
The pulsed near-infrared laser is Class-1 eye safe under all operating conditions. A nominal beam<br />
divergence of 0.1 degrees (2 mrad) <strong>for</strong> the LD90-3100 unit (see Tab. 4.9 below) produces a<br />
20 centimeter (8 in) footprint of illumination at 100 meters (328 ft) [Riegl, 1994]. The complete<br />
system is housed in a small light-weight metal enclosure weighing only 1.5 kilograms (3.3 lb), <strong>and</strong><br />
draws 10 W at 11 to 18 VDC. The st<strong>and</strong>ard output <strong>for</strong>mat is serial RS-232 at programmable data<br />
Figure 4.16: The RIEGL LD90-3 series laser rangefinder. (Courtesy of Riegl<br />
USA.)
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