Mobile Spatial Coordinate Measuring System Research Articles

Analysing uncertainty contributions in dimensional measurements of large-size objects by ultrasound sensors

According to the ever-increasing interest in metrological systems for dimensional measurements of large-size objects in a wide range of industrial sectors, several solutions based on different technologies, working principles, architectures and functionalities have been recently designed. Among these, a distributed flexible system based on a network of low-cost ultrasound (US) sensors – the Mobile Spatial coordinate Measuring System (MScMS) – has been developed. This article presents a possible approach to assess the system uncertainty referring to the measured point coordinates in the 3D space, focusing on the sources of measurement uncertainty and the related propagation law.

A wireless sensor network-based approach to large-scale dimensional metrology

In many branches of industry, dimensional measurements have become an important part of the production cycle, in order to check product compliance with specifications. This task is not trivial especially when dealing with large-scale dimensional measurements: the bigger the measurement dimensions are, the harder is to achieve high accuracies. Nowadays, the problem can be handled using many metrological systems, based on different technologies (e.g. optical, mechanical, electromagnetic). Each of these systems is more or less adequate, depending upon measuring conditions, user's experience and skill, or other factors such as time, cost, accuracy and portability. This article focuses on a new possible approach to large-scale dimensional metrology based on wireless sensor networks. Advantages and drawbacks of such approach are analysed and deeply discussed. Then, the article briefly presents a recent prototype system – the Mobile Spatial Coordinate-Measuring System (MScMS-II) – which has been developed at the Industrial Metrology and Quality Laboratory of DISPEA – Politecnico di Torino. The system seems to be suitable for performing dimensional measurements of large-size objects (sizes on the order of several meters). Owing to its distributed nature, the system – based on a wireless network of optical devices – is portable, fully scalable with respect to dimensions and shapes and easily adaptable to different working environments. Preliminary results of experimental tests, aimed at evaluating system performance as well as research perspectives for further improvements, are discussed.

Ultrasound Transducers for Large-Scale Metrology: A Performance Analysis for Their Use by the MScMS

The Mobile Spatial coordinate Measuring System (MScMS) is a distributed wireless-sensor-network-based system used to perform dimensional measurements of large-scale objects. The system consists of a wireless mobile probe with ultrasonic (US) transceivers, the position of which is determined using a distributed constellation of US transceivers arranged around the measuring area. These US transceivers, which are known as Crickets, transmit US signals to each other and measure their time of flight (TOF) to determine the mutual distances. The MScMS is able to calculate the Cartesian coordinates of the object surface points touched by the wireless mobile probe. This paper aims to experimentally evaluate the performance of the US transducers on each of the MScMS Crickets. The experiments are designed and performed by means of a statistical factorial plan to identify the most important factors affecting the transducers' performance on TOF measurements. Particular attention is given to the error derived by the US signal attenuation and the method of US pulse detection. The results are analyzed in detail and fully interpreted. Finally, some considerations about possible actions to improve the MScMS measuring system are given.

An empirical regressive model to improve the metrological performance of mobile spatial coordinate measuring systems

The mobile spatial coordinate measuring system (MScMS) is a system to perform dimensional measurements of large-scale objects. It consists of a wireless measuring probe with ultrasonic (US) transceivers, the position of which is determined using a distributed constellation of analogous transceivers arranged around the measuring area. The principle is to measure the time-of-flight (TOF) of the US signals exchanged between pairs of transceivers and, consequently, to obtain an estimate of their distances. The accuracy of TOF measurements can be attributed to many factors; the most influential are those associated with US signal attenuation. The purpose of this paper is to build an experimental correction model to reduce the MScMS’ error in TOF measurements. First, a two-way block design, which is based on exploratory experiments, is created to show that transmitter—receiver distance and relative orientation between US transceivers have significant effects on TOF measurement error. Next, an empirical regressive model is constructed on the basis of additional detailed experiments. After performing an extensive experimental validation, the model is automatically implemented by MScMS, with an iterative procedure. The most important benefit of such a model is an important reduction in the dispersion and an improved accuracy associated with TOF measurements.

Network localization procedures for experimental evaluation of mobile spatial coordinate measuring system (MScMS)

Large scale metrology refers to dimensional measurement of objects or features of perhaps a ten of meters or more in size. Alternatively, large scale metrology could be said to apply to any dimensional measurement where the metrology instrument has to be brought to the object rather than vice versa. Recent approaches seem to turn their attention towards distributed metrology systems made of multiple components with small dimensions spread around the measuring area. In general, these components are able to form a wireless network of sensors that allows rapid dimensional measurements to be performed in relation to large-size objects, with typical dimensions of several decametres. The portability, flexibility, and ease of installation of wireless sensor networks (WSNs) make these systems attractive for many industries manufacturing large scale products. This paper proposes different WSN localization procedures designed for the mobile spatial coordinate measuring system, a distributed metrology system developed at the industrial metrology and quality laboratory of DISPEA—Politecnico di Torino.

Mobile Spatial coordinate Measuring System (MScMS) – introduction to the system

In many industrial fields (for example, automotive and aerospace) dimensional measurements of large size objects should be easily and rapidly taken. Nowadays, the problem can be handled using many metrological systems, based on different technologies (optical, mechanical, electromagnetic, etc.). Each of these systems is more or less adequate, depending on measuring conditions, a user's experience and skill, or other factors like time, cost, dimensions, accurateness, portability, etc. In general for measuring medium-large size objects, portable systems can be preferred to fixed systems. Transferring the measuring system to the measured object place is often more practical than vice-versa. The purpose of this paper is to introduce a new system called Mobile Spatial coordinate Measuring System (MScMS). The system has been designed to perform dimensional measurements of medium-large size objects. MScMS is made up of three basic parts: a ‘constellation’ of wireless devices, liberally distributed around the working area; a mobile probe to register the coordinate points of the measured object; and a PC to store data sent by the mobile probe – via Bluetooth – and to process them by means of ad hoc application software. MScMS is easily adaptable to different measuring environments and does not require complex procedures for installation, start-up or calibration. This document presents the system hardware/software/firmware architecture and functionalities and describes the peculiarities and metrological performances of MScMS first prototype, which has been developed at the industrial metrology and quality laboratory of DISPEA – Politecnico di Torino. Finally, the most critical aspects of MScMS are illustrated and the research perspectives for future improvements are given.

A comparison of two distributed large-volume measurement systems: The mobile spatial co-ordinate measuring system and the indoor global positioning system

Advances in the area of industrial metrology have generated new technologies that are capable of measuring components with complex geometry and large dimensions. However, no standard or best-practice guides are available for the majority of such systems. Therefore, these new systems require appropriate testing and verification in order for the users to understand their full potential prior to their deployment in a real manufacturing environment. This is a crucial stage, especially when more than one system can be used for a specific measurement task. In this paper, two relatively new large-volume measurement systems, the mobile spatial co-ordinate measuring system (MScMS) and the indoor global positioning system (iGPS), are reviewed. These two systems utilize different technologies: the MScMS is based on ultrasound and radiofrequency signal transmission and the iGPS uses laser technology. Both systems have components with small dimensions that are distributed around the measuring area to form a network of sensors allowing rapid dimensional measurements to be performed in relation to large-size objects, with typical dimensions of several decametres. The portability, reconfigurability, and ease of installation make these systems attractive for many industries that manufacture large-scale products. In this paper, the major technical aspects of the two systems are briefly described and compared. Initial results of the tests performed to establish the repeatability and reproducibility of these systems are also presented.

On-line diagnostics in the Mobile Spatial coordinate Measuring System (MScMS)

Abstract Mobile Spatial coordinate Measuring System (MScMS) is a wireless-sensor-network based system developed at the industrial metrology and quality engineering laboratory of DISPEA – Politecnico di Torino. It has been designed to perform simple and rapid indoor dimensional measurements of large-size volumes (large-scale metrology). It is made up of three basic parts: a “constellation” of wireless devices (Crickets), a mobile probe, and a PC to store and elaborate data. Crickets and mobile probe utilize ultrasound (US) transceivers in order to evaluate mutual distances. The system makes it possible to calculate the position – in terms of spatial coordinates – of the object points “touched” by the probe. Acquired data are then available for different types of elaboration (determination of distances, curves or surfaces of measured objects). In order to protect the system against causes of error such as, for example, US signal diffraction and reflection, external uncontrolled US sources (key jingling, neon blinking, etc.), or software non-acceptable solutions, MScMS implements some statistical tests for on-line diagnostics. Three of them are deeply analyzed in this paper: “energy model-based diagnostics”, “distance model-based diagnostics”, and “sensor physical diagnostics”. For each measurement, if all these tests are satisfied at once, the measured result may be considered acceptable with a specific confidence coefficient. Otherwise, the measurement is rejected. After a general description of the MScMS, the paper focuses on the description of these three on-line diagnostic tools. Some preliminary results achieved by the system prototype are also presented and discussed.

Mobile spatial coordinate measuring system (MScMS) and CMMs: a structured comparison

In many branches of industry, most of manufacturing efforts are directed toward producing objects of specific forms and dimensions. Dimensional measurement is an important part of the production cycle, to check products compliance with specifications. For this, many substantial improvements in the existing technologies have been made, and new measuring systems have been introduced. This paper briefly introduces a recent measuring system—mobile spatial coordinate measuring system (MScMS)—which is suitable for performing dimensional measurements of large-size objects (dimension on the order of tens of meters). MScMS, thanks to its distributed wireless sensor network nature, is portable and can be easily arranged around the measured object. Furthermore, it does not require complex setup operations before being ready to perform measurements. After describing how the system works, we will compare it with well-tested and widespread instruments such as traditional coordinate measuring machines (CMMs), showing analogies and differences. The comparison is structured on the basis of different criteria, which are analyzed in detail in the first part of the paper. Although being able to perform similar measurements, CMMs and MScMS are different in technological features. CMMs are able to achieve higher level of accuracy, while MScMS is more flexible, cheap, and can be important to simplify the current measuring practices within large-scale industrial metrology. It can be concluded that these systems can easily coexist, as each system is suitable for specific applications.