A New Radar Sensor for Mobile Robot Localization and Mapping in Extensive Outdoor Environment. First Results

_2IK0Z5R10 In this paper we present a new sensor for mobile robot dedicated to obstacle detection, localization and mapping in extensive outdoor environments. Radar scanner principle. The sensor is b ased on microwave radar technology. Laser and video based sensors are common visually based sensors, particularly well adapted in indoor environments. But these systems are affected by visibility conditions that are often poor in outdoor environments: day/ night cycles change illumination; weather phenomena (fog, rain, etc.); dust clouds; etc. Sonar is an other common sensor not affected by visibility restrictions, but it is mainly affected by a limited maximum range and a poor angular resolution due to its beamwidth. Faced with these limitations, millimeter-wave radar provides an alternative solution for environmental imaging and overcomes the shortcoming of laser, video and sonar sensors. The developed radar uses a frequency modulation continuous wave (FMC W) principle: the transmit frequency is modulated with a linear law (triangular or sawtooth). If there is a target at a distance R, an echo signal will return after a time delay τ = 2 R / c. The measured beat frequency F b , wh ich appears at the receiver, re presents the difference between the emitted frequency and the frequency received after reflection on the target, and is proportional to R. The radar is equipped with a rotating antenna in order to achieve a complete 360° monitoring around the vehicle, with an angular resolution of 1°, in the range 3-100 m. The antenna angular rate ω = 360°/s and allows to construct one radar image each second. Microwave architecture, electronic cards (modulator, filter/ampl ifier, DC alimentation) and signal processing unit are integrated in the same housin g. D ata acquisition and signal processing ar e achieved with a Pentium M processor board. Computed radar data can be visualized directly on the radar (via a display connector), or transmitted for further treatments through an Ethernet link. Simultaneous Localizatio n And Mapping. Global Positioning S ystem (GPS) is a satellite based localization system, capable of providing a global location estimate at any point on the planet. But an exclusive use of GPS for outdoor localization is hazardous because off different problems: the necessity to have direct line-of-sight between the satellite and the GPS receiver; the level of precision necessary for autonomous navigation (less than one meter) requires simultaneous line-of-sight of at least five satellites; reflection of the satellite …