3 research outputs found
Aerial Manipulator Force Control Using Control Barrier Functions
This article studies the problem of applying normal forces on a surface,
using an underactuated aerial vehicle equipped with a dexterous robotic arm. A
force-motion high-level controller is designed based on a Lyapunov function
encompassing alignment and exerted force errors. This controller is coupled
with a Control Barrier Function constraint under an optimization scheme using
Quadratic Programming. This aims to enforce a prescribed relationship between
the approaching motion for the end-effector and its alignment with the surface,
thus ensuring safe operation. An adaptive low-level controller is devised for
the aerial vehicle, capable of tracking velocity commands generated by the
high-level controller. Simulations are presented to demonstrate the force
exertion stability and safety of the controller in cases of large disturbances
Optical Properties and Biochemical Indices of Marine Particles in the Open Mediterranean Sea: The R/V Maria S. Merian Cruise, March 2018
A rich data set on particulate matter optical properties and parameters (beam attenuation coefficient, volume concentration, particle size and PSD slope), accompanied by measurements of biochemical indices (particulate organic carbon, particulate nitrogen and their stable isotopic composition) was obtained from the surface to deep waters across the Mediterranean Sea, in March-April 2018. A decrease of beam attenuation coefficients, total particle volume concentrations, particulate organic carbon and nitrogen concentrations was noted towards the eastern Mediterranean Sea (EMed) in comparison to the western Mediterranean Sea (WMed). LISST-derived optical properties were significantly correlated with water mass characteristics. Overall, the most turbid water mass identified in the Mediterranean Sea was the Surface Atlantic water (AW), and the most transparent was the Transitional Mediterranean Water (TMW) in the Cretan Sea, whereas a general decrease in particulate matter concentration is observed from the WMed towards the EMed. Relatively depleted δ13C-POC values in the particle pool of the open Mediterranean Sea can be attributed to contribution from terrestrial inputs, mainly via atmospheric deposition. Throughout the entire water column, a significant positive correlation between particle beam attenuation coefficient and particulate organic carbon concentration is observed in the open Mediterranean Sea. Such relationship suggests the predominance of organic particles with biogenic origin. POC concentration and particle median diameter D50 are significantly and negatively correlated both in the WMed and the EMed Sea, confirming that small particles are POC-rich. At depth, a prominent decrease of most measured parameters was observed, with the exception of particle median diameter that increased substantially in the EMed towards the deep sea, suggesting potentially enhanced aggregation processes. The low particle size distribution slope ξ observed in the EMed, corresponding to larger particle populations, supports the above notion. Basin-wide Rayleigh-type isotopic fractionation in vertical profiles of δ15N-PN across the Mediterranean Sea, underlines the differences in the trophic characters of the two sub-basins and highlights the role of circulation changes on biogeochemical parameters and the redistribution of particulate matter as a source of nutrients in the water column
Optical Properties and Biochemical Indices of Marine Particles in the Open Mediterranean Sea: The R/V Maria S. Merian Cruise, March 2018
A rich data set on particulate matter optical properties and parameters
(beam attenuation coefficient, volume concentration, particle size and
PSD slope), accompanied by measurements of biochemical indices
(particulate organic carbon, particulate nitrogen and their stable
isotopic composition) was obtained from the surface to deep waters
across the Mediterranean Sea, in March-April 2018. A decrease of beam
attenuation coefficients, total particle volume concentrations,
particulate organic carbon and nitrogen concentrations was noted towards
the eastern Mediterranean Sea (EMed) in comparison to the western
Mediterranean Sea (WMed). LISST-derived optical properties were
significantly correlated with water mass characteristics. Overall, the
most turbid water mass identified in the Mediterranean Sea was the
Surface Atlantic water (AW), and the most transparent was the
Transitional Mediterranean Water (TMW) in the Cretan Sea, whereas a
general decrease in particulate matter concentration is observed from
the WMed towards the EMed. Relatively depleted delta C-13-POC values in
the particle pool of the open Mediterranean Sea can be attributed to
contribution from terrestrial inputs, mainly via atmospheric deposition.
Throughout the entire water column, a significant positive correlation
between particle beam attenuation coefficient and particulate organic
carbon concentration is observed in the open Mediterranean Sea. Such
relationship suggests the predominance of organic particles with
biogenic origin. POC concentration and particle median diameter D-50 are
significantly and negatively correlated both in the WMed and the EMed
Sea, confirming that small particles are POC-rich. At depth, a prominent
decrease of most measured parameters was observed, with the exception of
particle median diameter that increased substantially in the EMed
towards the deep sea, suggesting potentially enhanced aggregation
processes. The low particle size distribution slope xi observed in the
EMed, corresponding to larger particle populations, supports the above
notion. Basin-wide Rayleigh-type isotopic fractionation in vertical
profiles of delta N-15-PN across the Mediterranean Sea, underlines the
differences in the trophic characters of the two sub-basins and
highlights the role of circulation changes on biogeochemical parameters
and the redistribution of particulate matter as a source of nutrients in
the water column