Construction of glass waveguide refractive index profiles by the effective-index finite-difference method

A numerical method is applied to construct the refractive index profiles of optical waveguides from the measured effective indices (EI). The method is based on choosing a proper analytical function for the refractive index profile and searching its unknown parameters using the simplex search algorithm. Simultaneously, the finite-difference method (FDM) is used to solve the semi-vectorial Helmholtz equation for the guided modes effective indices. The method is applied successfully to two particular Ag⁺---Na⁺ ion-exchanged glass slab waveguides. The results are as accurate as those obtained from from commonly used IWKB-based method. The EI-FDM in principle can be applied to both slab and channel waveguides and does not require that the index profiles are monotonically decreasing, like most of IWKB-based methods. The relation between the induced refractive index and silver concentration profile, measured by SIMS, is found to be almost linear.     

Task-oriented motion planning for multi-arm robotic systems

In this paper a task-oriented motion planning approach for general cooperative multi-robot systems is proposed. In order to derive a meaningful task formulation, a taxonomy of cooperative multi-arm systems of industrial interest is devised. Then, a workpiece-oriented general formulation for cooperative tasks is proposed, where the user is asked to specify the motion of the system only at the workpiece level, while the motion of the single arms in the system is computed via kinematic transformations between the relevant coordinate frames. Based on this task formulation, an instructions set is derived to extend classical programming languages for industrial robots to general multi-robot systems. In order to test the approach, a software environment has been built, composed of an interpreter of the language and the motion planning software.     

Annual rates of ground deformation (1993–2010) at Campi Flegrei,Italy, revealed by Persistent Scatterer Pair (PSP) – SAR interferometry

Campi Flegrei is an active volcanic district located along the Eastern Tyrrhenian continental margin, Italy, and is worldwide known for dramatic ground deformation phenomena (bradyseism) recorded over the last centuries. The purpose of this article is to present the annual rates of ground deformation fields (average velocity, average acceleration, and combined annual velocity/acceleration) at Campi Flegrei, during almost two decades (years 1993–2010). The research work was conducted based on a temporal analysis and advanced mapping of Persistent Scatterer Pair (PSP) data, obtained from interferometric processing of radar satellite European Remote Sensing-1/2 and Environmental Satellite (ENVISAT) scenes of the study area. Patterns and trends of annual PSP velocity have provided a reconstruction of the spatial and temporal variability of ground deformation in terms of uplift and/or subsidence along the satellite line of sight (LOS). The analysis of annual PSP velocity and acceleration has revealed an intense dynamics of the Campi Flegrei caldera collapse-resurgence system, testified by the high PSP velocity and acceleration values, as well as the significant changes in the rates of ground deformation through time. The main results of this research indicate that the largest ground deformation is localized within and around the structural border of the Campi Flegrei caldera and suggest a systematic recurrence of opposite trends (uplift vs. subsidence) in the ground deformation of the inner caldera region with respect to the surrounding areas throughout the analysed time period.     

A non-iterative and effective procedure for simultaneous odometry and camera calibration for a differential drive mobile robot based on the singular value decomposition

Differential-drive mobile robots are usually equipped with video cameras for navigation purposes. In order to ensure proper operational capabilities of such systems, several calibration steps are required to estimate the video-camera intrinsic and extrinsic parameters, the relative pose between the camera and the vehicle frame and the odometric parameters of the vehicle. In this paper, simultaneous estimation of the aforementioned quantities is achieved by a novel and effective calibration procedure. The proposed calibration procedure needs only a proper set of landmarks, on-board measurements given by the wheels encoders, and the camera (i.e., a number of properly taken camera snapshots of the set of landmarks). A major advantage of the proposed technique is that the robot is not required to follow a specific path: the vehicle is asked to roughly move around the landmarks and acquire at least three snapshots at some approximatively known configurations. Moreover, since the whole calibration procedure does not use external measurement devices, it can be used to calibrate, on-site, a team of mobile robots with respect to the same inertial frame, given by the position of the landmarks’ tool. Finally, the proposed algorithm is systematic and does not require any iterative step. Numerical simulations and experimental results, obtained by using a mobile robot Khepera III equipped with a low-cost camera, confirm the effectiveness of the proposed technique.     

An integrated approach to fault diagnosis for a class of chemical batch processes

This paper deals with the problem of fault diagnosis for a class of chemical reactions taking place in a jacketed batch reactor. An integrated diagnosis scheme, using redundant temperature measurements and a bank of state observers, is adopted to detect, isolate and identify faults. A unified framework is developed to take into account faults affecting sensors, actuators and process. Redundant sensor measurements, together with the estimates provided by two isolation observers, are processed by a Decision Making System, providing information about the faulty sensor as well as healthy measurements. Then, healthy measurements are processed by a bank of adaptive observers, aimed at detecting, isolating and identifying actuator and process faults. In order to test the effectiveness of the approach, a detailed simulation case study is developed.     

A numerical study of erbium doped active LiNbO3waveguides by the beam propagation method

A numerical investigation of active waveguides realized on lithium niobate crystals using erbium as active element is presented. A software package is implemented to simulate the propagation of electromagnetic waves in graded-index active waveguides using an active vectorial beam propagation method (ABPM), which enables to calculate the optical field evolution along the propagation axis. A comparative study of the optical signal gain evolution as function of erbium concentration profiles obtained by various doping methods is presented. The optimal doping method, leading to the maximum gain, is determined     

The Tricept robot: dynamics and impedance control

The Tricept is a novel industrial robot characterized by a hybrid kinematic design featuring a three-degrees-of-freedom (3-DOF) structure of parallel type and a 3-DOF spherical wrist. In this work the authors focus on the derivation of a dynamic model to be used for both simulation and control purposes. Two different approaches are discussed and compared in terms of inverse dynamics computation. Then, a model-based control is derived aimed at enforcing a 6-DOF impedance behavior at the end effector to manage interaction with the environment. Simulation results are presented to evaluate the accuracy of an approximate dynamic model computation as well as to test the effectiveness of the proposed impedance control strategy.