Relationship between measurement uncertainty and verifiability of geometric specifications: the case study of drilled hole orthogonality

In mechanical design, geometrical specifications and dimensional tolerances are commonly used to avoid final product malfunction and to allow for assembly integration. Geometric specification usage, in particular, has many manufacturing and durability implications, the feasibility of their measurement and verification, however, is often neglected and the influence of measurement uncertainty in their evaluation underestimated. Often geometrical specifications are defined without considering measurement uncertainties, or measurability at all: it is not uncommon to find approved specifications prescribing unverifiable geometry, or dimension tolerances that exceed state-of-art measurements. This article explores the case study of orthogonality between a circular hole and the plane on which it is drilled, evaluated using a Coordinate Measuring Machine. Such specification is defined, according to ISO 14253, as the angle between the plane normal and cylinder axis. Uncertainty of points coordinates obtained can, however small, play a key role in the final evaluation of orthogonality: if the specified tolerance is thigh enough it is also possible to have misalignment uncertainty higher than the tolerance itself. The authors propose the results of a mathematical and numerical model, meant to help the designer to define specification to assess the relationship between cylinder-plane misalignment measurability, CMM uncertainty and features dimensions

Bridge's vehicular loads characterization through Weight-In-Motion (WIM) systems. The case study of Brescia

The growing traffic flow and the increase in transported masses negatively affect infrastructural safety. Several authors have characterized traffic loads on bridges in the American and Chinese context using Weigh-in-Motion (WIM) systems. Conversely, very few studies have been carried out in Europe and, as far as the authors know, none in Italy. This study covers this gap by providing a statistical analysis of raw WIM data collected on a main bridge near the city of Brescia (Italy). First, the traffic flow and the characteristics of vehicles were gathered by a WIM device. Second, some descriptive statistics were performed by computing the probabilistic distributions of numerous vehicular attributes. Third, as a novelty element, a K-means based Clustering technique was adopted on a wide set of vehicular features to detect heavy vehicle clusters. The results showed the existence of three main clusters: two predominately composed by lightly overloaded ordinary vehicles and construction machinery, respectively, and one by mass exceptional vehicles. This study considers a broader set of vehicular parameters than previous ones and then, provides a deeper understanding. Moreover, it shows that axle mass limits violations are noteworthy among mass exceptional vehicles in Italy highlighting the need of improving weight enforcement. These knowledges will be crucial for a rational organisation of the existing assets

Kinematic performance of micro-mobility vehicles during braking: experimental analysis and comparison between e-kick scooters and bikes

According to the Italian legislation, e-kick scooters and bikes are considered a single category of vehicles and can travel on the same infrastructures with the same rules; however, their kinematic behavior is very different. The adoption of a bike as a vehicle for covering short distances i.e., within 5 km is widely known both at the kinematic level and for its use by users. Conversely, e-kick scooters are "unknown" vehicles both for their kinematic characteristics and for their use by users. A handful of studies have shown how the behavior of e-kick scooters and bikes is very different; however, there are not many studies that analyze the different kinematic behavior of e-kick scooters and bikes. This study presents an experimental analysis that evaluates braking behavior by comparing e-kick scooters and traditional bikes according to several vehicle speeds. These analyzes help build a probabilistic mathematical model for estimating the stopping space of e-kick scooters and bikes. The availability of this model is crucial for the design of safe intersections between cycle paths and roads intended for motor vehicle traffic. Moreover, this model may reveal insights that could challenge the recent European regulations that equated e-kick scooters as bikes

Urban policies and planning approaches for a safer and climate friendlier mobility in cities: Strategies, initiatives and some analysis

How can urban policies and planning approaches help in achieving a safer mobility and carbon reduction in the transport sector? The attention of planners and policy makers towards the promotion of sustainability and reduction of environmental impacts has grown in recent years. This paper investigates the role that Urban Planning plays in the long term towards a safer and climate friendlier mobility, highlighting the need for integrated approaches gathering spatial planning and mobility management. After a review of several urban policies and planning strategies, initiatives, and approaches, mainly based on the urban scale, the paper presents an urban regeneration case study leading to an increase of pedestrian accessibility at the neighborhood level. This can be seen as a support tool to foster sustainable, safe, and climate friendly mobility in cities. The results of the performed analysis show a dependency of accessibility from two different factors: the distribution of services and the capillarity of the soft mobility network, which can contribute to creating a more walkable space

Comparing the vibrational behaviour of e-kick scooters and e-bikes: Evidence from Italy

E-kick scooters are currently among the most popular emerging electric-powered Personal micro–Mobility Vehicles (e-PMVs) and have recently been equated to e-bikes. However, even if the dynamic behaviour of e-bikes is well studied, much less has been done to understand the behaviour of e-kick scooters. Furthermore, comparisons between the two vehicles have rarely been investigated and only based on mechanical models. This study covers this gap by proposing a novel framework that evaluates the vibrational behaviours of both vehicles when driven by different users and exposed to the pavement irregularities, using both real and simulated data. The experimental data are collected equipping an e-kick scooter and an e-bike with Inertial Measurement Units, and then processed by ISO 2631–1 method to obtain an objective evaluation of the comfort. Next, the experimental data are expanded to include uncertainty applying a Monte Carlo Simulation based on a two-layer feed-forward Artificial Neural Network. Afterwards, several statistical analyses are performed to understand the key factors affecting the vibrational magnitude (and their extent) for each vehicle. This framework was tested in an Italian city (Brescia) along urban paths with five different pavement surfaces. The results showed that the e-kick scooter appears to be globally more solicited than the e-bike in terms of vibrational magnitude. Moreover, pavement surface, sensor position, user gender, user height, and travel speed are identified as crucial factors explaining the vibrational magnitude for both vehicles. The overall findings challenge the recent European regulations that equated e-kick scooters with bikes. These findings may help public administrations in planning the circulation of e-bikes and e-kick scooters in cities and recommend that manufacturers improve the e-kick scooter design by including shock absorbers to increase comfort

Techniques for on-board vibrational passenger comfort monitoring in public transport

Traffic calming devices on urban streets, such as elevated pedestrian crossings, speed bumps and roundabouts, are increasingly used, therefore bus passengers on-board comfort assessment is an actual problem. In order to measure vibrational on-board comfort for public transport standing passengers related to traffic calming, an acquisition system called ASGCM (Autonomous System for Geo-referenced Comfort Measurements) has been developed, taking as a reference the European regulations on rail transports. Thanks to ASGCM, each measurement of vibration, on-ground velocity and acceleration is linked with geographical information resulting from a GPS, so a map of a comfort index, as well as statistical surveys and correlation between on-board comfort and traffic calming, can be directly obtained using a Geographic Information System (GIS), querying a centralized remote database developed ad-hoc. A large number of experimental tests has been performed in order to define a vibrational comfort index and to collect a large statistics that allows a significant comparison between different infrastructures and their characterization. The proposed technique can also be useful for diagnostics purposes, such as vehicles comparison and vehicle and road maintenance state monitorin

Laser interferometry for straightness measurements in a weakly controlled environment

Abstract: Straightness measurements for the geometrical inspection of machining tools have been operated in a weakly controlled environment (concerning temperature, pressure, humidity and induced mechanical vibrations) with reference to industrial manufacturing departments. Measurements have been performed by means of a Wollaston prism laser interferometer. A first experimental characterization of this instrumentation has been operated by repeatability tests conducted in controlled and not controlled environments, considering different relative positions for the interferometer and the laser head. Then a calibration diagram has been constructed, assessing the accuracy and the instrumental uncertainty in the case of displacement measurements in a plane perpendicular to the laser beam direction. In a second stage a suitable method has been developed to estimate the uncertainty level associated to straightness measures operated by the laser interferometric technique and also by traditional instrumentation, such as taut-wire and microscope and precision level. Measurement uncertainty is estimated by means of the Monte Carlo Method and according to standards. Measures obtained by the laser interferometric method prove to be affected by higher levels of uncertainty than those coming from traditional approaches