Novel Autonomous Navigation Algorithms in Dynamic and Unknown Environments

Because the range of mobile robot sensors is limited and navigation maps are not always accurate, autonomous navigation in dynamic and unknown environments is a big challenge. In this article, we propose two novel autonomous navigation algorithms, which are based on the analysis of three conditions for unobserved and uncertain environments during navigation.

The algorithm for a dynamic environment uses the “known space” and “free space” conditions. It corrects false obstacles in the map when the conventional path is stuck. The navigation algorithm for unknown environments uses the “unknown space” and “free space” conditions. We use the Monte Carlo method to evaluate the performance of our algorithms and the other methods. Experimental results show that our autonomous navigation algorithms are better than the others.     

A robustness study of a finite‐time/exponential tracking continuous control scheme for constrained‐input mechanical systems: Analysis and experiments

The closed‐loop analysis of a recently proposed continuous scheme for the finite‐time or exponential tracking control of constrained‐input mechanical systems is reformulated under the consideration of an input‐matching bounded perturbation term. This is motivated by the poor number of works devoted to support the so‐cited argument claiming that continuous finite‐time controllers are more robust than asymptotical (infinite‐time) ones under uncertainties and the limitations of their results. We achieve to analytically prove that, for a perturbation term with sufficiently small bound, the considered tracking continuous control scheme leads the closed‐loop error variable trajectories to get into an origin‐centered ball whose radius becomes smaller in the finite‐time convergence case, entailing smaller posttransient variations than in the exponential case. Moreover, this is shown to be achieved for any initial condition, avoiding to restrain any of the parameters involved in the control design, and under the suitable consideration of the nonautonomous nature of the closed loop. The study is further corroborated through experimental tests on a multi‐degree‐of‐freedom robotic manipulator, which do not only confirm the analytical result but also explore the scope or limitations of its conclusions under adverse perturbation conditions.     

The influence of Cu,Fe, Ni,Pb and Zn on gum formation in the Brazilian automotive gasoline

In this research work, the effect of different concentrations of copper, iron, lead, zinc and nickel ions on the tendency for gum formation in gasohol fuel is investigated. For that purpose, a gasohol sample has been doped with these five metals ions at concentration levels of 0.25, 1.0, 2.0 and 3.0 μg ml^− 1. Washed gum content tests have been carried out using ASTM D 381 on samples stored for 7, 14, and 28 days. The results show that gum formation is strongly affected by Cu and Fe, with a much weaker effect from Ni and Zn, and an almost negligible effect from Pb. A variance analysis (ANOVA) of the experimental results shows that an increase in metal concentration strongly increases the rate of gum formation for all metal ions investigated, particularly Cu and Fe, while an increase in storage time has only a much weaker effect, being negligible for Zn.     

The dietary score as a simplified methodology in processing and analyzing food consumption data

The purpose of this investigation was to evaluate the dietary score as a valid and rapid alternative procedure for the processing and analysis of food consumption data in Guatemala. The dietary score consists in assigning points to a diet based upon the number of servings the diet provides of each one of the eight groups in which food has been classified. The size of the serving for each food receiving points was estimated based on available data describing the food pattern of Guatemala. The caloric contribution of each of the eight groups to the total caloric intake was also calculated, and information on the caloric and nutrient needs of the Guatemalan population is discussed. In this communication, the dietary score was compared to the percentage of adequacy for energy and nutrients in 392 diets of women, and children between the ages of 24 and 60 months. Half of the dietaries were collected using the 24-hour recall method, while in the other half, the direct weighing method was used. Nutritional adequacy was estimated from food composition tables and based on the recommended energy and nutrient intake figures. In addition, by utilizing the adequacy indices for energy and nutrients, a binary variable was developed to describe the overall adequacy of the diet. This variable describes the probability a diet has of being adequate, given the dietary score obtained. In conclusion, the dietary score was found to be a valid, rapid and efficient alternative for the processing and evaluation of food consumption information, collected by means of either the direct weighing of foods or the 24-hour recall methods.     

Development of a discrete roughness index for longitudinal road profiles

Engineers of off-road equipment, on-road vehicles, pavement and tyres must assess the roughness of a terrain surface for the design of their products. A ubiquitous roughness index is the International Roughness Index (IRI), which quantifies the roughness of a section of road based on the average suspension travel for a particular vehicle at a prescribed speed. The Discrete Roughness Index (DRI) developed in this work addresses a fundamental limitation of the IRI. Specifically, the DRI is calculated for each discretely measured location along a terrain surface; furthermore, the DRI is applicable to vehicles travelling at varying speeds and parameters other than the Golden Quarter-Car on which the IRI is based. The development begins with a consistent discretisation of the terrain surface, vehicle response and the IRI. The Fractional Response Coefficient is then developed which serves a fundamental role in the development of the DRI. Finally, the DRI is developed and its properties are discussed through theory and simulation of the ASTM E1926-08 Profile. One important property of the average DRI is that it converges to the IRI as the distance between sampled points becomes smaller, for the particular case when the Golden Quarter-Car model is simulated at 80 kph. The DRI is a more general solution of the roughness estimation problem than the IRI; therefore, the IRI is a proper subset of the DRI in which the DRI is averaged over a section of road.     

Graphene‐Based Biosensors: Going Simple

The main properties of graphene derivatives facilitating optical and electrical biosensing platforms are discussed, along with how the integration of graphene derivatives, plastic, and paper can lead to innovative devices in order to simplify biosensing technology and manufacture easy‐to‐use, yet powerful electrical or optical biosensors. Some crucial issues to be overcome in order to bring graphene‐based biosensors to the market are also underscored.     

Effects of desiccation on the elastic wave velocities of clay-rocks

Compressional (P) and shear (S) wave velocities were measured in a set of clay-rock samples subjected to a desaturation phase during which the samples were dried at ambient temperature conditions, with a median relative humidity equal to 37%, followed by a heating phase during which the same samples were heated to five different temperature levels, ranging from 65 to 105 °C. The recorded data shows that when the degree of saturation is decreased, both P and S wave velocities increase, thereby lying in the range (0–50%). The increase in S wave velocity following desiccation, by as much as 10%, and the associated increase in dynamic shear modulus, suggests the presence of desiccation-driven hardening, which is commonly observed in clay soils. The existence of such a phenomenon, which is not observed in other sedimentary rocks over such a range of saturation values, proves that the classical models (e.g., the Biot–Gassmann equation) used to study the effect of saturating fluids, fail to correctly assess the influence of variations in water content on seismic velocities measured in clay-rocks.