Path planning in formation and collision avoidance for multi-agent systems

This paper investigates, in a centralized manner, the motion planning problem for a team of unicycle-like mobile robots in a known environment. In particular, a multi-agent collision-free patrolling and formation control algorithm is presented, which combines outcomes of: (i) stability analysis of hybrid systems, (ii) algebraic geometry, and (iii) classical potential functions. The objective is achieved by designing a Lyapunov-based hybrid strategy that autonomously selects the navigation parameters. Tools borrowed from algebraic geometry are adopted to construct Lyapunov functions that guarantee the convergence to the desired formation and path, while classical potential functions are exploited to avoid collisions among agents and the fixed obstacles within the environment. The proposed navigation algorithm is tested in simulation and then validated by using the robots of a remote accessible robotic testbed

Evaluation of the composition of continuously-cultivated Arthrospira (Spirulina) platensis using ammonium chloride as nitrogen source

We evaluated the performance of continuous cultivations as well as to establish relationships between the rate of nitrogen source supply and protein and lipid contents along with fatty acid distribution in continuously-cultivated A. platensis

Biomass composition of Arthrospira platensis during cultivation on industrial process water and harvesting

Microalgae have the ability to utilize nutrients from wastewater and use it for biomass production. The effluent from a biogas process was tested as a nutrient source for blue-green microalga Arthrospira platensis cultivation and compared with conventional synthetic medium. Cultivation was carried out in four different concentrations of industrial process water (25, 50, 75, and 100%). The biomass was then harvested by microfiltration, and centrifugation followed by freeze drying. Variations in biomass composition were studied, in order to investigate effects of industrial process water on A. platensis over 30 days of cultivation. Applied harvesting techniques were evaluated for their effect on physiochemical properties of the biomass. Arthrospira platensis was able to grow in all tested wastewater concentrations except 100%, however, increase of wastewater concentration in medium resulted in a decreased growth rate. Partial substitution of synthetic Zarrouk medium with 25% of wastewater showed no adverse effect on chemical composition of the biomass including high protein content (45–58% dry weight) and favorable fatty acid composition (42–45% PUFAs of total fatty acids). Evaluation by optical microscopy showed that microfiltration caused cell rupture at the moderate level while centrifugation had more severe effect on A. platensis. Effect of centrifugal forces and shear stress on A. platensis cells was confirmed by detecting lower lipid content in samples after applying both microfiltration and centrifugation due to cell content leakage

Fed-batch cultivation of Arthrospira platensis using carbon dioxide from alcoholic fermentation and urea as carbon and nitrogen sources

It was evaluated the Arthrospira platensis cultivation using CO2 from alcoholic fermentation and either urea or nitrate as nitrogen source at different light intensities (60 64 I 64 240 \u3bcmol photons m-2 s-1). Whereas the CO2 source (pure CO2 or from alcoholic fermentation) did not influence the maximum cell concentration (Xm), cell productivity (PX) and nitrogen-to-cell conversion factor (YX/N), the use of urea instead of nitrate led to higher YX/N values. Xm and PX increased when I was increased from 60 to 120-240 \u3bcmol photons m-2 s-1. Using CO2 from alcoholic fermentation, the best performance (Xm = 2952 \ub1 35 mg L-1, PX = 425 \ub1 5.9 mg L-1 d-1 and YX/N = 15 \ub1 0.20 mg mg-1) was obtained at I = 120 \u3bcmol photons m-2 s-1 with urea. The results obtained in this work demonstrate that urea and CO2 from alcoholic fermentation could be simultaneously used in large-scale cultivations to reduce the environmental impact associated to the release of this greenhouse gas as well as the production cost of cyanobacteria