PROBABILISTIC MODEL OF LASER RANGE FINDER FOR THREE DIMENSIONAL GRID CELL IN CLOSE RANGE ENVIRONMENT

The probabilistic model of a laser scanner presents an important aspect for simultaneous localization and map-building (SLAM). However, the characteristic of the beam of the laser range finder under extreme incident angles approaching 900 has not been thoroughly investigated. This research paper reports the characteristic of the density of the range value coming from a laser range finder under close range circumstances where the laser is imposed with a high incident angle. The laser was placed in a controlled environment consisting of walls at a close range and 1000 iteration of scans was collected. The assumption of normal density of the metrical data collapses when the beam traverses across sharp edges in this environment. The data collected also shows multimodal density at instances where the range has discontinuity. The standard deviation of the laser range finder is reported to average at 10.54 mm, with 0.96 of accuracy. This significance suggests that under extreme incident angles, a laser range finder reading behaves differently compared to normal distribution. The use of this information is crucial for SLAM activity in enclosed environments such as inside piping grid or other cluttered environments. KEYWORDS:   Hokuyo UTM-30LX; kernel density estimation; probabilistic model

Range Information Characterization of the Hokuyo UST-20LX LIDAR Sensor

This paper presents a study on the data measurements that the Hokuyo UST-20LX Laser Rangefinder produces, which compiles into an overall characterization of the LiDAR sensor relative to indoor environments. The range measurements, beam divergence, angular resolution, error effect due to some common painted and wooden surfaces, and the error due to target surface orientation are analyzed. It was shown that using a statistical average of sensor measurements provides a more accurate range measurement. It was also shown that the major source of errors for the Hokuyo UST-20LX sensor was caused by something that will be referred to as “mixed pixels”. Additional error sources are target surface material, and the range relative to the sensor. The purpose of this paper was twofold: (1) to describe a series of tests that can be performed to characterize various aspects of a LIDAR system from a user perspective, and (2) present a detailed characterization of the commonly-used Hokuyo UST-20LX LIDAR sensor

Cross Hallway Detection and Indoor Localization Using Flash Laser Detection and Ranging

A flash LADAR is investigated as a source of navigation information to support cross-hallway detection and relative localization. To accomplish this, a dynamic, flexible simulation was developed that simulated the LADAR and the noise of a LADAR system. Using simulated LADAR data, algorithms were developed that were shown to be effective at detecting cross hallways in simulated ideal environments and in simulated environments with noise. Relative position was determined in the same situations. A SwissRanger SR4000 flash LADAR was then used to collect real data and to verify algorithm performance in real environments. Hallway detection was shown to be possible in all real data sets, and the relative position-finding algorithm was shown to be accurate when compared to the absolute accuracy of the LADAR. Thus, flash LADAR is concluded to be an effective source for indoor navigation information

Multi-robot behaviors with bearing-only sensors and scale-free coordinates

This thesis presents a low-cost multi-robot system for large populations of robots, a new coordinate system for the robot based on angles between robots and a series of experiments validating robot performance. The new robot platform, the r-one will serve as an educational, outreach and research platform for robotics. I consider the robot's bearing-only sensor model, where each robot is capable of measuring the bearing, but not the distance, to each of its neighbors. This work also includes behaviors demonstrating the efficiency of this approach with this bearing-only sensor model. The new local coordinate systems based on angular information is introduced as scale-free coordinate system . Each robot produces its own local scale-free coordinates to determine the relative positions of its neighbors up to an unknown scaling factor. The computation of scale-free coordinates is analyzed with hardware and simulation validation. For hardware, the scale-free algorithm is tailored to low-cost systems with limited communication bandwidth and sensor resolution. The algorithm also uses a noise sensitivity model to reduce the impact of noise on the computed scale-free coordinates. I validate the algorithm with static and dynamic motion experiments

Conception et intégration d'un capteur LIDAR 3D pour la navigation autonome des robots mobiles en terrain inconnu

Résumé L’étude de la planète Mars suscite un intérêt grandissant au sein de la communauté scientifique. Étant donné la distance séparant la Terre de cet astre, ainsi que l’environnement particulièrement hostile y régnant, son exploration tire avantage de l’utilisation de robots mobiles (rovers). Les fenêtres de communication peu nombreuses de même que les délais importants justifient le déploiement d’intelligence artificielle sur ces plates-formes mobiles afin de maximiser leur autonomie. L’un des enjeux primordiaux est alors la capacité que possèdent de tels robots de naviguer de façon autonome et donc de percevoir l’environnement au moyen de systèmes de vision avancés.Le projet de recherche dont il est question dans ce mémoire s’articule autour de ce thème et est réalisé en collaboration avec l’Agence spatiale canadienne (ASC). L’objectif principal vise la conception d’un système de vision tridimensionnelle permettant à un robot mobile de naviguer de façon autonome. Il concerne plus particulièrement la conception, l’intégration et l’étude de CORIAS (COntinuous Range and Intensity Acquisition System), un système de vision utilisant la technologie lidar (LIght Detection And Ranging). Le système en question utilise comme capteur principal un lidar LMS111 de la compagnie SICK. L’appareil développé au cours de cette recherche répond non seulement à l’objectif principal, mais il est également doté des caractéristiques suivantes : • La reproduction tridimensionnelle de l’environnement s’effectue dans un rayon maximum de 20 mètres. • L’acquisition des données se fait à raison d’un débit maximal de 27 050 points par seconde. • Le temps requis pour balayer complètement l’environnement avec des paramètres d’opération typiques (une résolution de 0,25° en élévation et de 0,50° en azimut) est d’environ 29 secondes. • Le système peut transmettre les mesures d’intensité associées aux points acquis.• Les résolutions verticale (élévation) et horizontale (azimut) sont configurables et assez fines pour détecter des obstacles.• Le système présente un niveau raisonnable de protection face aux conditions environnementales hostiles (poussière, pluie, neige, etc).----------Abstract The study of Mars is of growing interest among the scientific community. Given the large distance between this planet and the Earth, as well as the hostile environment prevailing there, its exploration takes advantage of using rovers. The rare communication windows, along with the important delays occuring during communications, justify artificial intelligence deployment on these mobile platforms in order to maximize their autonomy. Hence, one of the crucial issues is the ability the rover has to autonomously navigate and thus, to properly detect its environment with the help of advanced vision systems. The research project discussed in this thesis focuses on this theme and is done in collaboration with the Canadian Space Agency (CSA). The main objective is to design a three-dimensional vision system enabling a mobile robot to navigate autonomously. It relates more particularly to the design, integration and study of CORIAS (COntinuous Range and Intensity Acquisition System), a vision system using lidar (LIght Detection And Ranging). The system uses a LMS111, manufactured by SICK, as its main sensor. The device developed in this research project not only meets the main objective, but it also has the following characteristics:• The three-dimensional reproduction of the environment is performed within a 20 meter radius.• The maximum data acquisition rate is 27 050 points per second.• The time required to complete a full-coverage scan performed with typical operation parameters (0,25° elevation and 0,50° azimuth resolutions) is around 29 seconds.• The system is able to transmit the intensity measurements associated with the acquired points.• Vertical (elevation) and horizontal (azimuth) resolutions are configurable and fine enough to detect obstacles.• The system has a reasonable level of protection against bad weather conditions (dust, rain, snow, etc.).CORIAS only requires a 24 volts DC power supply and an Ethernet link to be operated. It can be installed easily on a large variety of platforms. The rover’s on-board computer is responsible for communicating with the vision system and provides the commands it needs to accomplish. The microcontroller, which is the central part of the system, operates on Linux and acts as a TCP-IP server