Luca Pugi

Preliminary design and fast prototyping of an Autonomous Underwater Vehicle propulsion system

The Mechatronics and Dynamic Modelling Laboratory of the Department of Industrial Engineering, University of Florence, as a partner of THESAURUS (Italian acronym for ‘TecnicHe per l’Esplorazione Sottomarina Archeologica mediante l’Utilizzo di Robot aUtonomi in Sciami’) project, has developed an innovative low-cost, multirole autonomous underwater vehicle, called Tifone. This article deals with the adopted methodologies for the autonomous underwater vehicle design: in particular, the main focus of this study is related to its propulsion system. According to the expected performances and requirements of THESAURUS project, the vehicle has to maintain good autonomy and efficiency (typical features of an autonomous underwater vehicle), with high manoeuvrability and hovering capabilities, which are more common of remotely operated vehicles. Moreover, cooperative underwater exploration and surveillance involve the use of a swarm of vehicles. In particular, the optimization of costs versus benefits is achieved through the design of a fleet of three multirole vehicles. Each autonomous underwater vehicle has five controlled degrees of freedom, thanks to four thrusters and two propellers: in this article, the preliminary design criteria concerning the vehicle and the design and testing of its actuation system are described.

HIL simulation of WSP systems on MI-6 test rig

In this article, a multi-purpose platform for Hardware In the Loop (HIL) testing of safety relevant railway subsystems, such as odometry boards or wheel slide protection systems, is shown. The rig, called MI-6, is a product of the cooperation of Trenitalia with researchers of Dip. Energetica Sergio Stecco (University of Florence). In this work, special attention has been paid to vehicle real-time model optimization according to customer specifications (Trenitalia) and to simulate artificially degraded adhesion between rolling surfaces where conventional adhesion models have poor performances or require unaffordable computational resources for real-time applications. In this article, a heuristic model based on energetic considerations and a wide archive of experimental test (courtesy of Trenitalia Società per Azioni) is presented. Also some simulation results and comparison with the experimental data are shown.

A railway vehicle multibody model for real-time applications

Hardware in the loop (HIL) techniques are widely used for fast prototyping of control systems, electronic and mechatronic devices. In the railway field, several mechatronic on board subsystems are often tested and calibrated following the HIL approach. The accuracy of HIL tests depends on how the simulated virtual environment approximates the physical conditions. As the computational power available on real-time hardware grows, the demand for more complex and realistic models of railway vehicles for real-time application increases. In past research activities, the authors worked on the implementation of simplified real-time models for several applications and in particular for an HIL test rig devoted to the type approval of wheel slide protection systems. The activity has then been focused on the development of a three-dimensional model of the dynamics of a railway vehicle for more complex applications. The paper summarises the features and the results of the study.

Design and Experimental Results of an Active Suspension System for a High-Speed Pantograph

In high-speed trains, current collection from the overhead line is assured by an articulated suspension system called the dasiadasiapantographpsilapsila Contact wires and overhead line are flexible systems that are subjected to oscillations that have to be compensated for a satisfactory quality of current collection. In high-speed railway applications, this technical problem is very important since higher traveling speed involves higher oscillations of the catenary. A feasible solution to improve current collection quality is to optimize the dynamical response of the pantograph suspension system through an active or semiactive suspension system. The authors of this paper have worked and cooperated with a team composed of members of Trenitalia SPA (main Italian railway company), Ital-certifer (an Italian R&D agency), and many Italian Universities (Universita di Firenze, Politecnico di Milano, Universita di Pisa, and Universita di Napoli) to the development of a prototype of an innovative railway pantograph for Italian high-speed lines. The authors have designed the layout of the control system (actuation system, sensors, drive and control algorithm, etc.). The proposed control strategy has been successfully calibrated with experimental tests. Testing procedures and experimental results are shown in order to demonstrate the feasibility of the proposed solution and performances achieved by the first Trenitalia prototype, the T2006 pantograph.

Cooperative localization of a team of AUVs by a tetrahedral configuration

This paper investigates the principles of a Cooperative Localization Algorithm for a team of at least three Autonomous Underwater Vehicles (AUVs) with respect to a surface support ship, without the use of Ultra-Short Baseline (USBL). It is assumed that each AUV is equipped with a low-cost Inertial Measurement Unit (IMU), a compass and a depth sensor, but only one of them has a high accuracy navigation sensor such as the Doppler Velocity Log (DVL). The surface boat locates itself by means of Global Positioning System (GPS). Range measurements provided by acoustic modems allow to avoid an unbounded error growth in the position estimate of each AUV. A geometric method, based on a tetrahedral configuration to obtain a deterministic fix for position, is proposed. This method allows to extend the advantages of the use of the DVL to the position estimate of other vehicles not equipped with DVL. The paper addresses also some of the problems related to the limitations of acoustic communication. The algorithm has been implemented and tested in simulations for a fleet of three AUVs and a surface support ship. An innovative cooperative localization algorithm for AUVs has been designed.Acoustic modems for communication are used as sensors of relative distance.The method is based on geometric relationships of a tetrahedral configuration.The algorithm performance are tested through a complete simulation model.A periodic reset of the estimation error is obtained for all the AUVs of the team.

Experimental campaign on a servo-actuated pantograph

Many interesting technical problems arise from the development of high speed trains current collection is one of the more important. The dynamic behaviour of a pantograph-catenary system make the electrical contact between the catenary and the contact-shoe unreliable. An insufficient quality of current collection causes a lot of negative consequences such as: insufficient current pick up, excessive wear of contact shoes and wires, power and control electronics malfunction, high EMI. Many Researchers have investigated the problem of optimum current pick up and many different solutions have been proposed in the past years. Since 1993 the Researchers of University of Florence have proposed the idea of a servo-actuated pantograph. The purpose of these studies was the development of a system including sensors and actuators able to regulate the value of relevant variables, such as contact force, at an optimum level researchers of Italian Railways found the proposal of a servo-actuated pantograph very interesting so the two groups began to co-operate. After the development of simulation models to evaluate performance and robustness of some control techniques for a servo-actuated pantograph, the authors arranged an experimental campaign in order to verify the results of simulations and to develop a first prototype of servo-actuated pantograph. This paper describes some simulation and experimental results obtained during the campaign which is currently going on.

Feasibility of Degraded Adhesion Tests in a Locomotive Roller Rig

Abstract In railway applications, the testing of on-board components is necessary to optimize the efficiency of the systems and to allow high safety levels. In order to reduce the time and the cost of the testing phase, the use of dedicated test rigs is being increased. The current paper summarizes some studies for the realization of a full-scale locomotive roller rig. The main mechanical and control problems that arise in the design of this type of test rig have been highlighted, and in particular, the feasibility of tests with degraded adhesion conditions between the wheel and the rail is simulated.

Typhoon at CommsNet13: Experimental experience on AUV navigation and localization

The CommsNet 2013 experiment took place in September 2013 in the La Spezia Gulf, North Tyrrhenian Sea. Organized and scientifically led by the NATO S&T Org. Ctr. for Maritime Research and Experimentation (CMRE, formerly NURC), with the participation of several research institutions, the experiment included among its objectives the evaluation of on-board acoustic Ultra-Short Base Line (USBL) systems for navigation and localization of Autonomous Underwater Vehicles (AUVs). The ISME groups of the Universities of Florence and Pisa jointly participated to the experiment with one Typhoon class vehicle. This is a 300 m depth rated AUV with acoustic communication capabilities originally developed by the two groups for archaeological search. The CommsNet 2013 Typhoon, equipped with an acoustic modem/USBL head, navigated within the fixed nodes acoustic network deployed by CMRE. This allows the comparison between inertial navigation, acoustic self-localization and ground truth represented by GPS signals (when the vehicle was at the surface). The preliminary results of the experiment show that the acoustic USBL self-localization is effective, and it has the potential to improve the overall vehicle navigation capabilities.

Evaluation of odometry algorithm performances using a railway vehicle dynamic model

In modern railway Automatic Train Protection and Automatic Train Control systems, odometry is a safety relevant on-board subsystem which estimates the instantaneous speed and the travelled distance of the train; a high reliability of the odometry estimate is fundamental, since an error on the train position may lead to a potentially dangerous overestimation of the distance available for braking. To improve the odometry estimate accuracy, data fusion of different inputs coming from a redundant sensor layout may be used. Simplified two-dimensional models of railway vehicles have been usually used for Hardware in the Loop test rig testing of conventional odometry algorithms and of on-board safety relevant subsystems (like the Wheel Slide Protection braking system) in which the train speed is estimated from the measures of the wheel angular speed. Two-dimensional models are not suitable to develop solutions like the inertial type localisation algorithms (using 3D accelerometers and 3D gyroscopes) and the introduction of Global Positioning System (or similar) or the magnetometer. In order to test these algorithms correctly and increase odometry performances, a three-dimensional multibody model of a railway vehicle has been developed, using Matlab-Simulink™, including an efficient contact model which can simulate degraded adhesion conditions (the development and prototyping of odometry algorithms involve the simulation of realistic environmental conditions). In this paper, the authors show how a 3D railway vehicle model, able to simulate the complex interactions arising between different on-board subsystems, can be useful to evaluate the odometry algorithm and safety relevant to on-board subsystem performances.

A scaled roller test rig for high-speed vehicles

Scaled roller rigs are quite widespread among railway research centres, and several examples are described in the literature. Due to their low costs and ease of use compared with full-scale counterparts, these types of rigs are used for a wide range of studies concerning dynamical stability, comfort, mechatronic subsystem and wear. Furthermore, scaled roller rigs can be a powerful education tool for railway engineering students. In this paper, the design and the main features of the scaled rolled rig that will be installed in the Mechatronics and Dynamic Modeling Laboratory of the University of Florence located in Pistoia, Italy, are described. The main feature of the proposed rig will be the simulation of degraded adhesion conditions. This feature is very important for hardware-in-the loop testing of many safety relevant on-board subsystems like wheel slide protection systems, traction and stability controls, odometry and automatic train protection and control.