Multi-robot olfactory search in structured environments

This paper presents a cooperative distributed approach for searching odor sources in unknown structured environments with multiple mobile robots. While searching and exploring the environment, the robots independently generate on-line local topological maps and by sharing them with each other they construct a global map. The proposed method is a decentralized frontier based algorithm enhanced by a cost/utility evaluation function that considers the odor concentration and airflow at each frontier. Therefore, frontiers with higher probability of containing an odor source will be searched and explored first. The method also improves path planning of the robots for the exploration process by presenting a priority policy. Since there is no global positioning system and each robot has its own coordinate reference system for its localization, this paper uses topological graph matching techniques for map merging. The proposed method was tested in both simulation and real world environments with different number of robots and different scenarios. The search time, exploration time, complexity of the environment and number of double-visited map nodes were investigated in the tests. The experimental results validate the functionality of the method in different configurations.     

Synthesis of Fractional-order PI Controllers and Fractional-order Filters for Industrial Electrical Drives

This paper introduces an electrical drives control architecture combining a fractional-order controller and a setpoint pre-filter. The former is based on a fractional-order proportional-integral (PI) unit, with a non-integer order integral action, while the latter can be of integer or non-integer type. To satisfy robustness and dynamic performance specifications, the feedback controller is designed by a loop-shaping technique in the frequency domain. In particular, optimality of the feedback system is pursued to achieve input-output tracking. The setpoint pre-filter is designed by a dynamic inversion technique minimizing the difference between the ideal synthesized command signal (i.e., a smooth monotonic response) and the prefilter step response. Experimental tests validate the methodology and compare the performance of the proposed architecture with well-established control schemes that employ the classical PIbased symmetrical optimum method with a smoothing pre-filter.      

Experimental studies on chemical concentration map building by a multi-robot system using bio-inspired algorithms

In this article we describe implementations of various bio-inspired algorithms for obtaining the chemical gas concentration map of an environment filled with a contaminant. The experiments are performed using Khepera III and miniQ miniature mobile robots equipped with chemical gas sensors in an environment with ethanol gas. We implement and investigate the performance of decentralized and asynchronous particle swarm optimization (DAPSO), bacterial foraging optimization (BFO), and ant colony optimization (ACO) algorithms. Moreover, we implement sweeping (sequential search algorithm) as a base case for comparison with the implemented algorithms. During the experiments at each step the robots send their sensor readings and position data to a remote computer where the data is combined, filtered, and interpolated to form the chemical concentration map of the environment. The robots also exchange this information among each other and cooperate in the DAPSO and ACO algorithms. The performance of the implemented algorithms is compared in terms of the quality of the maps obtained and success of locating the target gas sources.     

Nanobiosensors based on individual olfactory receptors

The animal olfactory system represents the gold standard of biosensors, due to its ability to identify and discriminate thousands of odorant compounds with very low thresholds. Using olfactory receptors (ORs) as sensing elements instead of chemical sensors, biosensors would benefit the naturally optimized molecular recognition of odorants to develop a new generation of bioelectronic noses. The purpose of SPOT-NOSED European project was the development of nanobiosensors based on single ORs anchored between nanoelectrodes, to mimic the performances of natural olfactory system. Nanobiosensors arrays could then increase odorant sensitivity or widen the odorant detection spectrum. ORs were expressed in yeasts plasmic membrane, and their functionality tested in whole yeasts. Then, nanosomes bearing the ORs were prepared from S. cerevisiae, and Surface Plasmon Resonance was performed on nanosomes for quantitative evaluation of OR response to odorant stimulation. ORs retain full activity and discrimination power in immobilized nanosomes, thus allowing their use in the fabrication of the nanobiosensors. Nanoelectrodes were fabricated using conventional photolithography and focused ion beam milling, with sizes in adequation with the nanosomes. ORs borne by nanosomes were specifically immobilized onto conducting substrates via mixed Self Assembled Monolayers, neutravidin and specific antibody to the ORs. The process was optimized by microcontact printing, and the anchored nanovesicles visualized by Atomic Force Microscopy. A transimpedance preamplifier suited for low-noise wide-bandwidth measurements was designed to be directly connected to the nanoelectrodes. Electrochemical Impedancemetric Spectroscopy detected significant changes upon electrodes functionalization, grafting of ORs carried by nanosomes, and ORs conformational change induced by odorant binding.     

Chemical characterisation of Nephrops norvegicus from Portuguese coast

BACKGROUND: Among seafood products, crustaceans are an important group owing to their nutritional benefits and high market value. The aim of this study was to evaluate the proximate composition as well as essential and non‐essential elements in the edible muscle of Nephrops norvegicus (Norway lobster). RESULTS: The studied crustacean showed a high protein level of about 210 g kg^?1 and a mineral level of about 24 g kg^?1. The pattern for the elements studied was Cl > Na > K > P > S > Ca > Mg > Br > Fe > Sr ≈ Zn > Cu > Mn > Rb > Se > Ni > Cr. Regarding non‐essential elements, the average total Hg content was 0.40 mg kg^?1, but two samples exceeded the legal limit set by the European Union (EU) for Hg in crustaceans (0.50 mg kg^?1). The levels of Pb and Cd found in all samples were below the EU limits (0.50 mg kg^?1 for both metals). CONCLUSION: Nephrops norvegicus is a good source of protein and contains most minerals at levels sufficient to satisfy the dietary reference intake. The amounts of Pb and Cd are not a concern. Hg levels indicate some contamination; however, taking into account the type of consumption of this species, it can be concluded that this does not represent a risk in terms of the human diet. Copyright © 2009 Society of Chemical Industry     

Cover Image,Volume 97, Issue 13

The cover image, by Márcia Carvalho et al., is based on the Review Cowpea: a legume crop for a challenging environment, DOI: 10.1002/jsfa.8250 . Photo Credit: Eduardo Rosa.