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

High Mobility HgTe Quantum Dot Films with Small Energy and Dynamic Disorder

The transport properties of HgTe colloidal quantum dot films are studied from 4 to 300 K with larger and more monodispersed quantum dots than previously. With nanocrystals of 14 nm diameter and 6.5% size distribution, a peak mobility of 65 cm2/(V s) is measured at 65 K for state-resolved transport in the 1Se state. Above 70 K, the mobility is band-like, but it follows the Marcus electron hopping model, while being far below the Mott–Ioffe–Regel limit. At 65 K, the average hopping time is as fast as 1 ps and getting close to the estimated dephasing time, or dynamic disorder, of the 1Se state, suggesting that coherence may exist for some neighboring dots. At lower temperatures, the mobility decreases for low bias, but it is temperature-independent for high bias due to field-driven transport. The Efros–Shklovskii variable range hopping model gives localization lengths of ∼100 nm, also suggesting large coherent domains. Twice lower mobility and shorter localization lengths are obtained with a 10 μm channel compared to a 2 μm channel, suggesting a possible percolation of the more conducting domains

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

Tiger AlGaN/GaN HEMT technology

International audienc

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