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Sea state affects the coasts of all maritime regions, and it impacts anthropic infrastructures and influences the activities carried out in the sea as well as in its proximity. Sea-state monitoring is therefore important for a number of reasons, including the need to validate weather forecast models and study the impact of sea waves on anthropic infrastructures such as ports. In this letter, we combined the measurements of sea state collected with Ocean Seismic Integrated System (OS-IS), a seismic-based system developed by AGI (Assist in Gravitation and Instrumentation) srl and INGV (National Institute for Geophysics and Volcanology), with those obtained using a Wave Radar system. The aim was to prove that this combination could enhance the efficacy and reliability of sea monitoring, thanks to the complementarity of the two types of measurements in terms of area covered and spatial resolution. More specifically, the sea-state parameters provided by OS-IS were compared with those provided by a Wave Radar system. OS-IS data were collected from three microseismic stations installed near the Gulf of La Spezia, on the Ligurian Coast, whereas the Wave Radar system was installed at the center of the Cinque Terre National Park at about 12 km from the OS-IS system. The comparison between the measurements of significant wave height (Hs) and peak period (Tp) showed a good agreement, with a correlation index close to 0.9. The residual difference highlights the complementarity of the two systems and the potential of an integrated system that includes both. In particular, OS-IS provides measurements over large, offshore areas, whereas the Wave Radar System provides high spatial-resolution measurements over areas near the coast.

Rotary encoders are used in many applications that require monitoring or controlling mechanical systems such as robots. Typically, small rotary encoders have poor resolution; this is unfortunate for applications such as robotics in medical surgery procedures. For example, in an articulated robotic endoscope, miniaturization is mandatory and, when automation is desired, high accuracy to track the shape and pose of the device is required; small (few millimeters) and accurate (few hundred arcsec) rotary encoders are thus needed. Previously, we introduced a novel concept of a miniaturizable angular sensor, called ASTRAS (Angular Sensor for TRAcking System). This was presented as a basic element of a tracking system for articulated endoscopes. The principle of measurement of ASTRAS is based on processing a shadow image cast by a shadow mask onto an image sensor. The characterization of the first prototype of ASTRAS was very promising, however, its angular range of about ±30 degrees was too limiting for many practical applications. In this work, we present an extension of the concept mentioned above to a rotary encoder that can measure one full rotation of 360 degrees thus the name is ASTRAS360. Its working principle bases on encoding the shadow image using colored light to distinguish different angular sectors. The identification of the sector corresponds to a coarse angular measurement, which is afterward refined using the same technique as in ASTRAS. We implemented this concept, realizing a prototype and an algorithm to calculate the angle from the shadow image. The experiments demonstrated the validity of this concept and showed encouraging results with a precision of ∼0.6 arcsec and 6σ-resolution of 3.6 arcsec corresponding to 19 bits., Sensors and Actuators A: Physical, 312, ISSN:0924-4247, ISSN:1873-3069

Robot-assisted and computer-guided minimally-invasive procedures represent a turning point in Minimally-Invasive Surgery (MIS) because they overcome significant limitations found in current state-of-the-art manual MIS procedures (e.g. imprecise motion, hand tremor, fatigue of the surgeon, limited workspace/maneuverability, etc.). Importantly, robotic systems can only reach the required high accuracy and precision when a tracking system with the corresponding accuracy and precision level for the surgical tool’s end-effector enables closed-loop feedback control. Herein, we present a tracking system meeting the above required high accuracy and precision called ASTRAS (Angular Sensor for TRAcking Systems). In this paper, the working principle and performance of ASTRAS are presented and characterized respectively. ASTRAS is arranged in a way that a tilt of a mirror produces a shift of a shadow cast on an image sensor. Since the mechanical constraints between the light source, mirrors, shadow mask, and image sensor are known, the angle can be derived from the measured shadow shift. The working principle of ASTRAS allows the measurement of 2 degrees of freedom at once. Additionally, the commercial availability of small image sensors (∼1 × 1 × 0.5 mm3) allows implementing ASTRAS in the future as a down-scaled version in surgical tools such endoscopes. The characterization of ASTRAS was performed with an experimental setup evaluating the angular measurement performance in one degree of freedom. The results revealed a precision of ∼3·10−6 rad, a thermal stability of 1.9·10-5 rad/°C, a long term drift 10-5rad/day, and a linearity error of ∼10-4 rad. Future developments will focus on implementing a miniaturized prototype and making a chain of sensors to use in articulated devices.

This work was done in the framework of the MIRACLE project devoted to the development of a flexible, articulated robotic endoscope to perform laser osteotomies (bone cutting). In order to control this robot with the required accuracy of 0.2 mm at the tip position, a tracking system needs to feed back the pose of the tip and the shape of the endoscope. One of the possible designs of such a robotic endoscope is based on an articulated device that can be tracked by measuring the bending angle at each joint. Recently, we presented (Iafolla et al., 2018) a novel angular sensor called ASTRAS (Angular Sensor for TRAcking Systems), which measures a one degree of freedom rotation by processing a shadow image cast through a shadow mask onto an image sensor. One ASTRAS will be placed at each joint of the articulated robotic endoscope in order to measure their bending angles. The planned diameter of the MIRACLE endoscope is 10 mm and it will contain several components such as the optical fiber for the laser, irrigation and sucking systems, and robot control mechanisms. However, the latest version of ASTRAS covered a volume of 40x40x55 mm3. For this reason, the most demanding requirement for the design of the final ASTRAS sensor is its miniaturization to fit the sensor inside the joint of the endoscope. Consequently, in this contribution, we investigated the possibility of miniaturizing ASTRAS and assess its limitations due to some fundamental aspects. In particular, we built a prototype based on a NanEye camera by AMS (1x1x0.5 mm3) and a micro-milled shadow mask with 0.08 mm wide slits. The tests of this prototype showed encouraging results and will be discussed. In particular, at such small dimensions, there are no unexpected optical effects (e.g. optical diffraction due to the mask) worsening the measurement. Indeed, the precision of 5 arcsec and the linearity error of 23 arcsec RMS are comparable to those of the previous bigger prototype. Further considerations and concepts related to the miniaturization of ASTRAS are also discussed in this paper.

The main objective of this work is to develop a miniaturized, high accuracy, single-turn absolute, rotary encoder called ASTRAS360. Its measurement principle is based on capturing an image that uniquely identifies the rotation angle. To evaluate this angle, the image first has to be classified into its sector based on its color, and only then can the angle be regressed. Inspired by machine learning, we built a calibration setup, able to generate labeled training data automatically. We used these training data to test, characterize, and compare several machine learning algorithms for the classification and the regression. In an additional experiment, we also characterized the tolerance of our rotary encoder to eccentric mounting. Our findings demonstrate that various algorithms can perform these tasks with high accuracy and reliability; furthermore, providing extra-inputs (e.g. rotation direction) allows the machine learning algorithms to compensate for the mechanical imperfections of the rotary encoder., Measurement, 169, ISSN:0263-2241, ISSN:1873-412X

We report a temperature-compensated FBG-based 3D shape sensor with an average positioning error of 1.4 %. The sensor consists of three single-mode fibers with four arrays of FBGs, which are glued on a substrate.

In the last ten years many proposals and studies have been advanced for a far-IR kilometer baseline interferometer. This paper shows the results of FISICA (Far Infrared Space Interferometer Critical Assessment), an FP7 program of the European Community. In particular, we focus on an innovative strategy to cover the plane of observation with a minimal propellant consumption. Results of some numerical simulations, carried out for a three-booms configuration, are provided.

The European project “Wind, Ports, and Sea” (VPM), funded by the European Cross-border Programme “Italy-France Maritime 2007–2013”, aims to improve the safety conditions and to reduce the hazards by the development of a coupled monitoring and forecast system of the sea-state outside the main harbors of the Northern Tyrrhenian and Ligurian Seas. In particular, the sea and wind forecasts are evaluated by using a numerical model specifically implemented for this project and the monitoring system is made of measuring stations installed on the coast near the harbor areas. The Port Authority of La Spezia has implemented a pilot project based on a new method, called OS-IS (Ocean Seismic-Integrated Solution, [1]), for the inland remote monitoring of the sea. The key advantage of OS-IS is that is installed inland, inside a building, and there are no parts in the sea. The core elements of the system are high sensitivity accelerometers and specifically developed algorithms for the evaluation of the sea state using the micro-seismic signals on the basis of mathematical models and fitting calibration factors. After more than one year since the first installation, OS-IS has shown a high level of reliability and the validity of the measurements has been demonstrated by comparison with those of the buoys. In the following, the installed systems will be shortly described and compared with the conventional methods.