Enrico Ravina

Experimental modal analysis of bows

The vibration performances of bow instruments are usually studied developing numerical and experimental modal analyses of the body of the instrument or of their parts (tailpiece, bridge, fingerboard, neck). The dynamic contribution of the bow is less considered, but the mutual actions generated between bow and strings are conditioned by the mechanical features of the bow. The paper analyzes the dynamic behaviour of different kind of bows (clip‐in frog and screw‐driven frog) and different geometries (baroque, modern,...) through experimetal modal analyses. Bows are instrumented with micro‐accelerometers and excited by a micro‐hammer. Frequency Response Functions up to 2500 Hz allow a good characterization of the bow and show significant differences about the modal shapes. The study is integrated with the experimental strain analysis, based on micro strain gauges glued on the body; the very small dimensions of the transducers (2.5 mm) allow, from one side, a not intrusive analysis but, from another side, require specific contrivances of mounting. Details on the integrated experimentations are focussed and discussed.

An experimental workbench for innovative pneumatic units co-operating under distributed control

Abstract The paper describes the most relevant aspects of research activity, still under development, concerning the analysis of the performance of advanced co-operating pneumatic units and components driven by different distributed control systems. Field bus, Actuator–Sensor interface (ASi) and servo-positioning strategies are applied to flexible and innovative pneumatic devices, in order to test the behaviour of different interconnected subsystems under simulated working conditions. An original approach oriented to the on-line monitoring and diagnostics of electrical and pneumatic components involved in the experimental workbench is described.

Team of Pneumatic ASi-Controlled Climber Robots for Ships Inspection

The paper describes the main features of a team of co-operant climber robots designed for autonomous inspections inside ships and offshore platforms. The autonomous units are conceived for monitoring of the status of internal metallic surfaces, taking into account the peculiarities related to the shape of the typical metallic structures characterizing the marine field. The team consists of four units at least, pneumatically powered and controlled by Actuator-Sensor-interface technology (ASi). The number of the team units can be modified as a function of the inspection. Each unit is equipped with video-camera and ultrasonic thickness measurement device; other sensors and transducers can be added and handled, depending on the inspection requirements.

An Oil-Hydraulic Workbench for Advanced Dynamic Testing

The paper refers on a polyvalent oil-hydraulic testbench, designed and realized in order to develop a wide and diversified range of static and dynamic tests on mechanical components and structural elements. The testbench is an experimental mechatronic unit, integrating mechanical equipment, electronic devices and elaboration and control systems, aided by virtual instrumentation. In order to describe the main features and potentialities of the proposed testbench, the paper refers on tests of specific mechanical devices (shock absorbers) and of samples of structural elements (glued junctions). The possible and potential applications of the proposed workbench are very wide and oriented to validation, experimental identification, advanced testing and diagnostics in mechanical field.© 2006 ASME