Search

With the increase of planetary exploration missions and thereby the resultant increase of extraterrestrial rovers deployed, their mobility performance meets new challenges. Wheel-soil interaction plays an important role in the movement of these rovers. Our research addresses the study of this interactions in the first moments of the trajectory. The investigations reported so far, focus on long-distance motion (approx. 20-30 cm). However, the authors believe that the firsts interactions are crucial for the future performance of the motion. Here, by means of a device that allows multiple and precise repetitions of a wheel rolling experiment at controlled gravities, we characterize the movement of a wheel on sandy soil, in the gravity of Mars. Our study reveals that gravity influences the performance of the wheel, under these conditions. The experiments show that, as the gravity decreases, the rolling efficiency also decreases. [ABSTRACT FROM AUTHOR]

The precise and continuous tracking of millimetric-sized walkers—such as ants—is quite important in behavioral studies. However, due to technical limitations, most studies concentrate on trajectories within areas no more than 100 times bigger than the size of the walker or longer trajectories at the expense of either accuracy or continuity. Our work describes a scientific instrument designed to push the boundaries of precise and continuous motion analysis up to 1000 body lengths or more. It consists of a mobile robotic platform that uses digital image processing techniques to track the targets in real time by calculating their spatial position. During the experiments, all the images are stored and afterwards processed to estimate with higher precision the path traced by the walkers. Some preliminary results achieved using the proposed tracking system are presented. [ABSTRACT FROM AUTHOR]

The traditional diagnosis method of Rheumatoid Arthritis (RA) consists in the evaluation of hands and feet radiographs. However, still for medical specialists it turns out to be a complex task because many times the correct diagnosis of the disease depends on the detection of very subtle changes for the human eye. In this work, we developed a system based on Artificial Intelligence (Al), using Convolutional Neural Networks (CNN) for the automatic detection of RA from hand radiographs. The model efficiency is measured with 15 cases achieving an accuracy of 100%. Results of the experiments conducted, showed a superior performance compared to similar state-of-the-art systems reported in the consulted bibliography. This model would be useful for Cuban medicine as a diagnosis tool. [ABSTRACT FROM AUTHOR]

We introduce an instrument for a wide spectrum of experiments on gravities other than our planet's. It is based on a large Atwood machine where one of the loads is a bucket equipped with a single board computer and different sensors. The computer is able to detect the falling (or rising) and then the stabilization of the effective gravity and to trigger actuators depending on the experiment. Gravities within the range 0.4 g-1.2 g are easily achieved with acceleration noise of the order of 0.01 g. Under Martian gravity, we are able to perform experiments of approximately 1.5 s duration. The system includes features such as WiFi and a web interface with tools for the setup, monitoring, and data analysis of the experiment. We briefly show a case study in testing the performance of a model Mars rover wheel in low gravities. [ABSTRACT FROM AUTHOR]

This article discusses the challenges associated with motion tracking of insects. The authors comment on the various methods of insect tracking, including studies of bees, ants, and spiders. They examine the development of tracking algorithms to detect insect movement, including methods such as optical flow, color matching, and template matching.

The sedimentation of solid objects into granular matter near boundaries is an almost virgin field of research. Here we describe in detail the penetration dynamics of a cylindrical object into a quasi-2D granular medium. By tracking the trajectory of the cylinder as it penetrates the granular bed, we characterize two distinct kinds of motion: its center of mass moves horizontally away from the lateral wall, and it rotates around its symmetry axis. While the repulsion is caused by the loading of force chains between the intruder and the wall, the rotation can be associated to the frictional forces between the grains and the intruder. Finally, we show the analogies between the sedimentation of twin intruders released far from any boundaries, and that of one intruder released near a vertical wall. [ABSTRACT FROM AUTHOR]

Impact crater experiments in granular media traditionally involve loosely packed sand targets. However, this study investigates granular impact craters on both loosely and more tightly packed sand targets. We report experiments that consistently adhere to power-law scaling laws for diameter as a function of impacting energy, similar to those reported by other groups for their experiments utilizing both solid and granular projectiles. In contrast, we observe significant deviations in the depth versus energy power law predicted by previous models. To address this discrepancy, we introduce a physical model of uniaxial compression that explains how depth saturates in granular collisions. Furthermore, we present an energy balance alongside this model that describes the energy transfer mechanisms acting during crater formation. We found a better way to transfer vertical momentum to horizontal degrees of freedom as the impact surface compacts, resulting in shallow craters on compacted sandbox targets. Our results reveal depth-to-diameter aspect ratios from approximately 0.051 to 0.094, allowing us to interpret the shallowness of planetary craters at the light of the uniaxial compression mechanism proposed in this work.