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1、英文原文Coordinate Measuring MachiningOn-line diagnostics in the Mobile Spatial coordinate Measuring System (MScMS) Fiorenzo Franceschini, Maurizio Galetto, Domenico Maisano, Luca Mastrogiacomo Politecnico di Torino, Dipartimento di Sistemi di Produzione ed Economia dellAzienda (DISPEA), Corso Duca degl
2、i Abruzzi 24, 10129 - Torino, Italy Keywords: Mobile measuring system Coordinate metrology Dimensional measurements Large-scale metrology Wireless-sensor-networks Localization algorithms On-line diagnostics Abstract: Mobile Spatial coordinate Measuring System (MScMS) is a wireless-sensor-network bas
3、ed systemdeveloped 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
4、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 “touche
5、d” 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 sourc
6、es (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
7、 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 online diagnosti
8、c tools. Some preliminary results achieved by the system prototype are also presented and discussed. 1. Introduction In many industrial fields (for example, automotive and aerospace) dimensional measurements of large-size objects should be easily and rapidly taken 15. Nowadays, the problem can be ha
9、ndled using many metrological systems, based on different technologies (optical, mechanical, electromagnetic, etc.). These systems are more or less adequate, depending on measuring conditions, users experience and skill, cost, accuracy, portability, etc. In general formeasuring mediumlarge-size obje
10、cts, portable systems can be preferred to fixed ones. Transferring the measuring system to the measured object place is often more practical than the vice-versa 1. This paper analyzes the Mobile Spatial coordinate Measuring System (MScMS), which has been developed at the industrial metrology and qua
11、lity engineering laboratory of DISPEA Politecnicodi Torino 6. MScMS is a wireless-sensor-network based system, designed to perform dimensional measurements ofmediumlarge-size objects(for example, longerons of railway vehicles, airplane wings, fuselages,etc.). These objects can hardly be measured by
12、traditional coordinatemeasurement systems, such as, for example, Coordinate Measurement Machines (CMMs) because of their limited working volume 7,1. MScMS working principle is very similar to that of well-known NAVSTAR GPS (NAVigation Satellite Timing And Ranging Global Positioning System) 8. The ma
13、in difference is that MScMS is based on ultrasound (US) technology to evaluate spatial distances, instead of radiofrequency (RF).MScMSis easily adaptable to different measuring environments and does not require complex procedures for installation, start-up or calibration 6. The aim of this paper is
14、to describe the on-line diagnostics tools implemented in the system in order to continuously monitor measurement reliability. 2. The concept of “reliability of a measurement” If we refer to the field of CMMs, the concept of “on-line metrological performance verification” is strictly related to the n
15、otion of “on-line self-diagnostics” 5,9. In a same sense, this approach is “complementary” to that of uncertainty evaluation 1015. In general, the on-line measurement verification is a guarantee for the preservation of a measurement system characteristics (including accuracy, repeatability, and repr
16、oducibility) 16,17. The effect of a measuring system degradation is the production of “non-reliable measurements”. In general, we can define the concept of “reliability of a measurement” as follows. 3. MScMS technological and operating features MScMS prototype is made up of three main components (se
17、e Fig. 1) 6: - a constellation (network) of wireless devices (Crickets), opportunely arranged around the working area; - a measuring probe, communicating via ultrasound transceivers (US) with constellation devices in order to obtain the coordinates of the touched points; - a computing and controllin
18、g system (PC), receiving and processing data sent by the mobile probe, in order to evaluate objects geometrical features. The measuring probe is a mobile system hosting two wireless devices, a tip to touch the surface points of the measured objects and a trigger to activate data acquisition (see Fig
19、. 2) 6. Given the geometrical characteristics of the mobile probe, the tip coordinates can be univocally determined by means of the spatial coordinates of the two probe Crickets 6. 4. MScMS diagnostic system Fig. 5. An example of 2D massspring system. Three reference nodes (_x1, _x2, _x3) with known
20、 position are linked by springs to the point to be localized (_xP ). Being based upon US technology, MScMS is sensible to many influencing factors. US signals may be diffracted and reflected by obstacles interposed between two devices, external uncontrolled events can become undesirable US wave sour
21、ces and even positioning algorithms can lead to non-acceptable solutions. These and other potential causes of accidental measurement errors must be taken under control to assure proper levels of accuracy. With the aim of protecting the system, MScMS implements a series of statistical tests for on-li
22、ne diagnostics. Three of them are analyzed in the following sections: - “energy model-based diagnostics”; - “distance model-based diagnostics”; - “sensor physical diagnostics”. 5. Conclusion MScMSis an innovative wireless measuring systemcomplementar to CMMs. A prototype of this system has been deve
23、loped at the industrial metrology and quality engineering laboratory of DISPEA Politecnico di Torino. It is portable, not too much expensive, and suitable for large-scale metrology (uneasy on conventional CMMs). Some innovative aspects of the system concern its on-line diagnostics tools. When dealin
24、g with measurement systems, the importance of a good diagnostics of produced measures is crucial for applications in which errors can lead to serious consequences. The diagnostics tools described in this paper, all based on the concept of “reliability of a measurement”, enable MScMS user to reject m
25、easurements which do not satisfy a series of statistical acceptance tests with a given confidence coefficient. For eachmeasurement, if all these tests are satisfied at once, the measured result is considered acceptable. Otherwise, the measurement is rejected. After rejection, the operator is asked t
26、o redo the measurement, changing the orientation/positioning of the probe or, if it is necessary, beacons arrangement in the system network. In same cases, the system might force to repeat a measurement too many times, causing an excessive extension of the measurement duration. This problem can be o
27、vercome by changing the configuration of the constellation. Futurework, aswell as improving the power of the existing tools, will be aimed to enrich MScMS control system by implementing additional tools able to steer the operator during measurement. For example, suggesting the position of the probe
28、in the measuring volume, or proposing possible extensions of the network of beacons, or automatically filtering and/or correcting corrupted measurements. 6. Three coordinates measuring instrument profile Three dollars and name is mechanical measuring three coordinates an essential tool. Tri-ordinate
29、 measuring machine, it is to point to in one hexahedral space can behave, within the scope of geometry, length and circumferential indexing, etc, and the instrument measurement capabilities three coordinates measuring instrument or called three coordinates quantity bed. Tri-ordinate measuring instru
30、ment can be defined as a has can make three direction of detectors, can be in three mutually perpendicular guide rail to move, the probe contact or non-contact signal means such as the three shaft transmit system (as displacement measurement by optical ruler data processor or computer calculation, e
31、tc all point coordinates the needed parts (X, Y, Z) and various function measurement instrument. Tri-ordinate measuring instrument measurement function should include size accuracy, positioning accuracy, geometry precision and contour precision, etc. A few decades ago, three coordinates measuring in
32、strument industry is only few people know. Since the 1960s, because electronic, computer and sensor technology development, the three coordinates functions and application of measuring apparatus, also improved many, make the manufacturing industry can achieve high quality, high efficiency and multif
33、unctional etc measurement requirements. So quality management department can to size of workpiece geometry and outline, such as rapid and accurate measuring reach. Refer From mechanical speaking, coordinate measuring machine (three yuan) advantages are: 1 the key -, and technological progress coordi
34、nate measuring machine for the advancement of science and technology, make a coordinate measuring machine practical, and have many different measurement function. The key technological progress as follows: floating bearing, each face -axes air-float bearing mobile use, make head mobile smooth, measu
35、ring precision measurement can be very moving head; Optical linear feet, cooperate installed on the machine coordinate system, optical linear feet nubile can very precise coordinate measuring value; have to win Computer equipment, coordinate measuring machine adopts calculation method of obtaining m
36、easurements results, data processor and has the measuring software, increased the function of coordinate measuring machine. Due to the above three technological progress, make a coordinate measuring machine has the superior measurement function. 2, the advantages of coordinate measuring machine are
37、as follows: A, in space detection head along the X, Y, Z three axial movement, its are scrambling to right standard or polar said. B, workpiece cube of five sides are measurable, need not transform workpiece position, if installed with proper jigs and special measure head, sixth surface can also mea
38、sured. C, coordinate measuring machine operation and measure the work, do not need special technology can do the job D, can be in any position, set, and to work axis indirect measurement result calculated main algorithm, increasing the function and using the elastic measurement. E, using computer da
39、ta processor, quickly and accurately calculate the measured value, cooperate to teach program of CMM measuring Richard work automation. F, replace traditional measurement methods to improve the inspection accuracy, and for high precision products, can 100 percent inspection. G, complex workpiece and
40、 measure the difficulty of workpiece is high, can be measured accurately. H, sharply reduce inspection time, inspection charges, inspection human, increase measurement efficiency.ences Coordinate measuring machine type can be divided into: 1, right Angle coordinate system: including painting line ma
41、chine, cantilever, bridge posture; 2, joint coordinate system: joint coordinate measuring machine by differential, this type of measurement section coordinate system with measured along the surface of workpiece mobile, head to the joint Angle will guide the change by decoder, the angular measuring k
42、now each axis, the joint coordinates of homogeneous transformation type, can move through the axis quantity. (the market typically have: the epithet in three times yuan, video images, three times the CNC three yuan RMB, economical three yuan, optical image measuring instrument, longmen type three yu
43、an, CNC automatic big three yuan, schedule of non-contact three yuan, optical tri-ordinate measuring machine, three coordinates measuring instrument, three-dimensional coordinates, optical three yuan, probe type three times yuan, economical manual three yuan measuring machine, high precision automat
44、ic three yuan measuring machine, measuring type three yuan measuring machine, three yuan measuring machine, second yuan measuring instrument, three yuan measuring instrument, three yuan, activity bridge type three yuan measuring machine, fixed bridge type three yuan measuring instrument) Actually th
45、ree times by exposure to $workpiece surface can be divided into: touch coordinate measuring machine and contactless coordinate measuring machine. Coordinate measuring machine will contact with floating bearing introduced above, and the measuring of the head non-contact coordinate measuring machine r
46、efers to our present market called image type precision surveying and mapping three yuan. Its function generally have: 1, CNC electric desktop: (in a software function control working mesa, increase operation personnel use and operational convenience) 2, CNC automatic measurement: the set automatica
47、lly according to customers can be automatically measure the product size, measured values can be automatically forwarded to Excel generate statistics report. 3, SPC data conversion (process capability analysis) : can the measured data output to Excel analysis. 4, AutoCAD standard engineering drawing
48、 can be input: the standard engineering graphics directly AutoCAD input to the images of surveying and mapping apparatus software, make AutoCAD engineering drawings with actual workpiece appearance, comparing overlapping so as to find out the difference between workpieces and engineering drawing. 5,
49、 graphics output to AutoCAD and automatically adjust: according to the real-time image can be described according to the actual workpiece appearance according to the actual needs of the graphics to set automatically benchmark and right during transmission. 6, automatic take line, take round: need not with the artificially take line or round in a certain range, can be automatically capture software most accurate linear or circular. 8, scanning workpiece appearance
