Fabio Bartolini

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.

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.

Pantograph-catenary interaction model comparison

The interaction between pantograph and catenary is the present problematic of current collection in electrical railways. Current collection enhancement is a key requirement for train speed-up in railway industry. Several models have been proposed in this sense to investigate the dynamic response of pantograph-overhead contact line. This paper presents a review of different pantograph and catenary models. More attention is paid to catenary models in order to evaluate its implementation on a real-time system. The accuracy is compared based on European Standard EN50318–2000 and the computation time between all realized models is also discussed.

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.

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.

A numerical model of a HIL scaled roller rig for simulation of wheel–rail degraded adhesion condition

Scaled roller rigs used for railway applications play a fundamental role in the development of new technologies and new devices, combining the hardware in the loop (HIL) benefits with the reduction of the economic investments. The main problem of the scaled roller rig with respect to the full scale ones is the improved complexity due to the scaling factors. For this reason, before building the test rig, the development of a software model of the HIL system can be useful to analyse the system behaviour in different operative conditions. One has to consider the multi-body behaviour of the scaled roller rig, the controller and the model of the virtual vehicle, whose dynamics has to be reproduced on the rig. The main purpose of this work is the development of a complete model that satisfies the previous requirements and in particular the performance analysis of the controller and of the dynamical behaviour of the scaled roller rig when some disturbances are simulated with low adhesion conditions. Since the scaled roller rig will be used to simulate degraded adhesion conditions, accurate and realistic wheel–roller contact model also has to be included in the model. The contact model consists of two parts: the contact point detection and the adhesion model. The first part is based on a numerical method described in some previous studies for the wheel–rail case and modified to simulate the three-dimensional contact between revolute surfaces (wheel–roller). The second part consists in the evaluation of the contact forces by means of the Hertz theory for the normal problem and the Kalker theory for the tangential problem. Some numerical tests were performed, in particular low adhesion conditions were simulated, and bogie hunting and dynamical imbalance of the wheelsets were introduced. The tests were devoted to verify the robustness of control system with respect to some of the more frequent disturbances that may influence the roller rig dynamics. In particular we verified that the wheelset imbalance could significantly influence system performance, and to reduce the effect of this disturbance a multistate filter was designed.

Comparison of different control approaches aiming at enhancing the comfort of a railway vehicle

In the last years magneto-rheological dampers have been successfully used to realize semi-active suspension systems for automotive applications. Due to their dimension flexibility and the wide range of forces they can exert, these devices can be used even for railway applications, such as in the present work. This paper is focused on the design, evaluation and comparison of different control strategies for semi-active suspension system on the secondary suspension stage of an high speed train. In particular, the classical simulation of mechanical impedance, also known as “skyhook damper”, and a “sliding mode” control exploiting the gradient projection method in order to cope with linear constraints on the forces, have been compared to a traditional passive suspension system. In order to test the proposed control strategies and to simplify the control gain refinement, a multi-body model of the railway vehicle have been built by means of Matlab/Simulink™. Moreover, in order to fairly compare the different control strategies, a performance index has been defined, which is based on the comfort test that is usually done on real trains.

Thesaurus: AUV teams for archaeological search. Field results on acoustic communication and localization with the Typhoon

The Thesaurus project, funded by the Tuscany Region, had among its goals the development of technologies and methodologies for archaeological search with Autonomous Underwater Vehicles working as a team in exploration missions. This has led to the design and realization of a new AUV class, the Typhoon, on the basis of the archaeological requirements, and of an appropriate acoustic simultaneous communication and localization scheme. The paper describes the project background, the technical characteristics of the Typhoon AUVs, and the field results in acoustic localization as obtained in the CommsNet13 cruise, led by the NATO CMRE (Centre for Maritime Research and Experimentation), to which the Thesaurus project teams of the University of Pisa and Florence took part. In particular, the fields result reports the performance of acoustic localization through on-board USBL communicating with fixed modems placed in initially unknown locations.

Design and optimization of a semi-active suspension system for railway applications

The present work focused on the application of innovative damping technologies in order to improve railway vehicle performances in terms of dynamic stability and comfort. As a benchmark case-study, the secondary suspension stage was selected and different control techniques were investigated, such as skyhook, dynamic compensation, and sliding mode control. The final aim was to investigate which control schemes are suitable for optimal exploitation of the non-linear behavior of the actuators. The performance improvement achieved by adoption of the semi-active dampers on a standard high-speed train was evaluated in terms of passenger comfort. Different control strategies have been investigated by comparing a simple SISO (single input single output) regulator based on the skyhook damper approach with a centralized regulator. The centralized regulator allows for the estimation of a near optimal set of control forces that minimize car-body accelerations with respect to constraints imposed by limited performance of semi-active actuators. Simulation results show that best results is obtained using a mixed approach that considers the simultaneous applications of model based and feedback compensation control terms.

Real-time simulation of pantograph-catenary interaction

The current collection enhancement is a key requirement for train speedup in railway industries. However, pantograph-catenary interaction is the present challenge of enhancing current collection in electrical railways. In the literature, the application of active pantograph control is considered as a means to improve the pantograph dynamics and to reduce the contact force vibration. Due to track test high cost, control strategies are validated in the initial phase through laboratory tests and as a result, a real-time catenary model can be developed. Based on model developed, control strategies can be examined on a pantograph-in-the-loop (PIL) configuration including a real-time platform by means of which the dynamic behavior of catenary is emulated in real-time. This paper investigates the implementation of pantograph-catenary interaction on a real-time platform based on “Opal-RT” technology equipped with a quad-core main processor. The European standard EN50318-2000 is used for the validation of the catenary model.