13 research outputs found
First results in terrain mapping for a roving planetary explorer
To perform planetary exploration without human supervision, a complete autonomous rover must be able to model its environment while exploring its surroundings. Researchers present a new algorithm to construct a geometric terrain representation from a single range image. The form of the representation is an elevation map that includes uncertainty, unknown areas, and local features. By virtue of working in spherical-polar space, the algorithm is independent of the desired map resolution and the orientation of the sensor, unlike other algorithms that work in Cartesian space. They also describe new methods to evaluate regions of the constructed elevation maps to support legged locomotion over rough terrain
Terrain Mapping for a Roving Planetary Explorer
The main task of perception for autonomous vehicles is to build a representation of the observed environment in order to carry out a mission. In particular, terrain modeling, that is modeling the geometry of the environment observed by the vehicle's semors, is crucial for autonomous underwater exploration. The purpose of this work is to analyze the components of the terrain modeling task, to investigate the algorithms and representations for this task, and to evaluate them in the context of real applications. Terrain representation is an issue that is of interest in many areas of mobile robotics, such as land vehicles, planetary explorers, etc. This paper surveys some of the ideas developed in those areas and their relevance to the underwater navigation problem. Terrain modeling is divided into three parts: structuring sensor data, extracting features, and merging and updating terrain models
Methods for Identifying Footfall Positions for a Legged Robot
We are designing a complete autonomous legged robot to
perfom planetary exploration without human supervision. This
robot must traverse unknown and geographically diverse areas in
order a collect samples of materials. This paper describes how a
geometric terrain representation from range imagery can be used
to identify footfall positions. First, we present previous research
aimed to determine footfall positions. Second, we describe several
methods for determining the positions for which the shape of the
terrain is nearest to the shape of the foot. Third, we evaluate and
compare the efficiency of these methods as functions of some parameters
such as particularities of the shape of the terrain. Fourth,
we introduce other methods that use thermal imaging in order to
differentiate material
First Results in Terrain Mapping for a Roving Planetary Explorer
To perform planetary exploration without human supervision, a complete autonomous rover must be able to model its environment while exploring its surroundings. We present a new algorithm to construct a geometric terrain representation from a single range image. The form of the representation is an elevation map that includes uncertainty, unknown areas, and local features. By virtue of working in spherical-polar space, the algorithm is independent of the desired map resolution and the orientation of the sensor, unlike other algorithms that work in Cartesian space. We also describe new methods to evaluate regions of the constructed elevation maps to support legged locomotion over rough terrain
Power Performance Evaluation of AlGaN/GaN HEMTs through Load Pull and Pulsed I-V Measurements
A systematic evaluation of power
performances of AlGaN/GaN HEMTs has been performed
by means of CW on wafer Load Pull measurements at X
band. Those measurements have been correlated to the
results obtained through I-V and S-parameters pulsed
measurements and a strong correlation has been found
between the two types of measurement. Power up to 6Watts
has been measured on a 1.2 mm device that can be further
improved if trapping effects can be removed. A non linear
electrical model of the 0.25x 1200 µm² transistor taken from
the I-V and the S-parameters pulsed measurements is
validated by CW load pull measures
Influence of passivation on High-Power AlGaN/GaN HEMT devices at 10GHz.
AlGaN/GaN high electron mobility
transistors (HEMTS on SiC) were characterized before and
after SiO2/Si3N4 passivation. DC, small signal, pulsed and
large signal measurements were performed. We discuss the
role and the influence of passivation on the device
performance and characteristics. A good correlation is
observed between pulsed and power measurements. At
10GHz, a 6.3W/mm power density with a 36% PAE at 2dB
of compression was obtained after passivation, while only
2.9W/mm before passivation