1,720,977 research outputs found
Theoretical insights on the influence of the experimental plan in the calibration of multicomponent force and moment transducers
Full text linkIn recent years, the increasing demand of multicomponent force and moment transducers led the necessity to develop specific calibration procedures. Sensitivity and exploitation terms of these transducers are usually expressed in matrix form to evaluate cross-talks between the different components. According to the seminal work of Ronald Fisher in 1926, to provide accurate results, calibrations shall be performed with different combinations of forces and moments in order to minimize the correlation between them. In this work, a theoretical investigation, based on an ideal transducer, on the influence of the experimental plan in the evaluation of exploitation matrix terms and the associated uncertainties as function of the number of measurements and the correlation between the applied forces and moments is performed. It is found that at decreasing number of measurements and increasing correlations between the applied forces and moments, uncertainties increase, while exploitation matrix terms are poorly affected by the chosen experimental plan
Dynamic calibration system for seismometers: Traceability from 0.03 Hz up to 30 Hz
Full text linkMechanical calibration and traceability of seismometers in operating conditions are still a technical challenge, since very low-frequency ranges (below 0.1 Hz) are involved, and sensors under investigation are generally heavy and bulky. Recently, within the vibration metrology field, some pioneering works proposed to evaluate the seismometers’ sensitivity by applying laboratory mechanical calibration procedures, against primary or secondary standards, according to the ISO 16063 methods. By following this path, at INRIM, it has been developed a suitable system for short period horizontal and vertical ground velocity calibration of 3-axis seismometers. The calibration system allows to directly evaluate the sensitivities of the 2 axes perpendicular to the gravity field, with respect to the horizontal ground velocity (S-waves), and to derive the sensitivity of the vertical axis, parallel to the gravity field, with respect to the vertical ground velocity (P-waves), in the frequency range between 0.03 Hz and 30 Hz
Perspectives and limits on the use of commercial low-cost digital MEMS accelerometers in gravimetry
Full text linkThe value of the acceleration due to gravity is of interest in a wide range of fields, from geophysics, geodesy, water-floor monitoring, and hazard forecasting to oil, gas and mineral exploration. For this purpose, relative or absolute gravimeters have been developed and used for decades. While absolute gravimeters are mainly used in monitoring stations or as reference, relative gravimeters are those actually used to determine the relative variations of the local gravitational field given their smaller dimension, lighter weight, and better reading resolution, despite the high costs and the difficulty in being used under severe environmental conditions. In the last years, the advent of micro-electromechanical-systems (MEMS), in particular MEMS accelerometers, has opened up the doors to new measuring possibilities at very low-costs. As a consequence, different international research groups focused their efforts to develop relative MEMS gravimeters and showed that this technology might be really useful for monitoring the gravitational field. However, their current production is limited to a few specimens and prototypes that cannot be exploited on a large scale at the present day. For this reason, this work investigates the possibilities and the limits in the use of commercial digital MEMS accelerometers as relative gravimeters. The digital MEMS accelerometers investigated in this work are two commercial low-cost digital MEMS accelerometers (STM, model LSM6DSR, and Sequoia, model GEA). The first is composed of an accelerometer sensor, a charge amplifier, and an analog-to-digital converter and is connected by a serial cable to a separated external microcontroller (ST, model 32F769IDISCOVERY), in which other electronic components are integrated. The second is composed of the sensing element and the analog-to-digital converter. Both are connected to the computer via USB cable. The two devices are included in a thermally insulated case, in which a resistive heater and a resistance thermometer (PT1000), connected in loop, are placed in order to guarantee temperature stability during use. The system, installed on a tilting table to ensure higher accuracy in the evaluation of local g, is calibrated in static conditions by comparison to the absolute gravimeter IMGC-02 at a specific measurement location at INRIM. Calibration is repeated several times over a period of a few weeks in order to evaluate repeatability, reproducibility and stability over time. Despite the promising future prospects of this technology, at present, the levels of precisions are low compared to the ones required by most of geodynamics applications
Accurate coil springs axial and transverse stiffness measurements with multicomponent testing machines
Full text linkAccurate characterization of coil springs, typically in terms of axial and transverse stiffness, is crucial in many applications, in particular in automotive engineering, such as suspensions, vibration reduction, seating, exhaust valves, gear engagement controls, transmission hose, fuel panels, car trunks, and engine hoods. These measurements are usually performed in spring testing machines along the vertical axis in quasi-static conditions. However, when springs are stressed along the main vertical axis, side forces, bending and torsion moments are generated, thus have to be evaluated. For this reason, a hexapod-shaped multicomponent force and moment transducer has been recently devised, realized and integrated into standard spring testing machines capable to measure the displacement along the main and transverse axes. In this way, forces, moments and displacement components generated by the springs can be measured and axial and transverse stiffness derived. In this work, two multicomponent spring testing machines with the hexapod-shaped force and moment transducer are described and measurements on different large coil springs are presented
Static, continuous and dynamic calibration of force transducers: A comparative study on a low-force strain-gauge measuring device
Full text linkCurrent ISO 376 standard focuses on static calibration of force transducers, overlooking time and frequency influences, crucial in real-world applications such as automotive, aerospace, and healthcare, where mechanical and materials testing is essential for product quality and safety. As a result, novel calibration guidelines have been proposed to extend calibration to continuous and dynamic loading conditions. The paper examines the calibration results of a 200 N high-precision strain-gauge force transducer under static, continuous, and dynamic conditions. While sensitivities across these conditions are generally compatible, uncertainties in continuous and dynamic calibrations are notably higher, which could impact material testing and related applications. If continuous and dynamic sensitivity uncertainties dropped to the static uncertainty level, compatibility would be compromised because of significant differences between the three. It's unclear whether these discrepancies arise mainly from the intrinsic characteristics of the transducer in continuous dynamic conditions or from the inability to reach the transducer capacity force values during dynamic calibration
Metrological traceability for the absolute gravity Italian network
Full text linkThe Absolute Gravity Italian Network project aims to update the Italian gravity network that nowadays is framed to IGSN71, established in 1971. The focal point of the project is to define a new reference for gravity with absolute gravity observations performed according to the international standardised methodology detailed in the document “CCM-IAG Strategy for Metrology in Absolute Gravimetry” (2015). IAG resolution No. 2 and subsequent, moreover establish the need to satisfy the metrological traceability also for Absolute Gravity measurements. This can be exploited by different methods such as reference sites, international comparisons of absolute gravimeters and calibration by comparison. Measurements have been performed in appropriate sites distributed across the Italian country. The collected and validated data will be stored in an open database, as the absolute gravity database maintained by the Bureau Gravimétrique International/Bundesamt fuer Kartographie und Geodaesie when will be operative, contributing to feed the new International Terrestrial Gravity Reference System. All the gravimeters used in the measurements participated to the international comparisons organised by CCM and/or EURAMET TC-M obtaining compatible results. However, in order to validate the results and to ensure traceability to the SI, additional comparisons between the absolute gravimeters used in the measurements have been performed just before the measurement campaign. The primary Italian reference instrument is the absolute gravimeter IMGC-02, developed and maintained by INRiM with an expanded measurement uncertainty of 8.5 μGal. The comparison sites are both located at INRiM and are provided with solid basements that guarantee good measurement repeatability and low floor noise which could ensure the final uncertainty. This paper shows the results of these measurements
Sensorization of Soft Robot Joints for Accurate and Durable Bending Measurement
Full text linkIn the practical implementation of soft robots, accurately tracking the deformation of links (or joints) is crucial for obtaining proper control. Therefore, there is a need for lightweight, durable, and cost-effective solutions to monitor the movement of soft segments. This study proposes sensor-equipped flexible joints capable of measuring the angle between the segments of a robotic finger, considering pure in-plane bending. Initially, these joints were simulated to assess their mechanical behavior and the feasibility of accommodating strain gauges to measure differential strain, which correlates with angle measurements. Based on the simulation results, three types of sensor-equipped joints with distinct mechanical properties were developed. These joints were characterized in terms of angle measurement accuracy and durability. The experimental evaluation assessed that maximum error, compared to an accurate reference angle measured using a MEMS accelerometer, was less than 1.5°. Durability tests demonstrated that joint performance remained stable over more than 3500 bending cycles, during which the joints were bent up to approximately 65°; the measured angle drift remained below 2°
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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