EETimes India - November 16, 2008 - (Page 9)

In Focus | Data acquisition Embedded system eases rail maintenance continued from page attached to the side of a vehicle, wobbles ±5° within a distance range of 1 to 5 metres under the control of a Blackfin processor. The profile of the neighbouring rail, which is expected within this scanning sector, is low-pass and median filtered and transformed from the polar into the Cartesian coordinate system. After applying some processing like vector-rotation and re-sampling, the profile passes through a pattern-matching algorithm. The goal is to find the exact vector to a characteristic geometric feature within the railhead. Due to the many obstacles like rocks or grass that are found on railways, this vector finally passes through a plausibility checker and a tracking algorithm to provide reliable and valid results. All this is done in a 5-Hz loop under real-time conditions. Longitudinal profiles—Highspeed eddy current sensors record both rail surfaces with micrometer accuracy (figure 3). A linear encoder processes signals from a magnetic ring that serves as an odometer and as a trigger for the AD sensor converters. This signal then goes through a FIR (Finite-Impulse-Response) filter with a bandpass topology reducing the spectrum to the characteristic wavelengths. On top of the surface profile, metallurgical irregularities such as partial hardenings and welding points are also recorded. Cross profiles—Laser technology is today’s state of the art non-contact measuring principle to get the exact cross section of a railhead. Depending on the required accuracy or capturing speed, either traversing laser beams or laser “curtains” (figure 4) are used to do the job. Raw profiles are linearised, scaled and spike filtered in real-time. Metering devices—Until some years ago, maintenance staff used many different metering devices identifying cracks and variances on the rails. Each methodology specialised in re- cording one specific rail defect and almost all these mechanical methods lacked precise and reproducible results. In recent years, industrial solutions providers like Schmid Engineering have incorporated embedding processor technology and methodology into design. Advancing these methods into the railway infrastructure business gradually empowered mobile and multi-functional rail measuring by smart metering devices. Rail monitor devices use state of the art measurement technology to simultaneously define the cross profile of the rail, the head height, track gauge, inclination, depth and ambient temperature, detected and logged at any specific location. Such a device continuously monitors and records longitudinal track parameters as an operator or vehicle pulls it along the rails. It carries several sensors to map problems like corrugations, holes, cracks, variations in rail gauge, and inclination. The collected information are processed and visualised on-site and stored to removable memory or wirelessly transmitted to an operator interface. At the heart of these test tools are Blackfin processors, which enable the convergence of MCU and DSP technology through dynamic power management for any given battery operation. The MCU part conveniently interfaces with scalable I/O like laser scanners, analogue and digital sensors, keyboards, TFTs, batteries/fuel gauge and removable media. The DSP part is dedicated to advanced digital algorithms like filtering, Fast Fourier Transform (FFT) or determination of the geometric residuals or other demanding computational tasks. Recent advancements in graphical system design tools like LabVIEW Embedded, meanwhile, offer a direct programming model for Blackfin processors with its high-level block diagram and dataflow-oriented language. This high-level ap- Figure 3: No-contact eddy current sensors pulsed by magnetic encoders acquire longitudinal rail profiles. Figure 4: Rail cross profiles are captured by high-speed laser scanners. proach, with ready-to-use mathematical analysis blocks and graphical multi-tasking, takes functionality to the next level of embedded design. M easuring machines— A multi-functional vehicle that is driven by a set of five interlinked Blackfin processors is able to record rail parameters up to 10 km of a railway section with 5-mm point-to-point resolution. Processor #1 allows user interaction over a keyboard and two TFT monitors. Processor #2 records track geometry and longitudinal profiles at high speed and embeds GPS information into the measurements which is received by Processor #3. To- gether with cross-sections that are captured by Processor #4, all the data is finally streamed to Processor #5, which stores the huge amount of data in RAM buffers to be eventually saved to binary files on removable media. Read the full article to know how this maintenance solution locates and maps defects, how it controls grind units to fix detected problems on the rails, and more. | Online Reduce sensor module cos t s with optimised sensor calibration Timely testing avoids cosmic ray damage to auto electronics EE Times-India | November 16-30, 2008 | www.eetindia.com http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/current sensor.HTM?ClickFromNewsletter_081116 http://www.embeddeddesignindia.co.in/ART_8800551459_2800006_TA_28cafe57.HTM?ClickFromNewsletter_081116 http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/FFT.HTM?ClickFromNewsletter_081116 http://www.embeddeddesignindia.co.in/article/sendInquiry.do?articleId=8800551459&catId=2800006?ClickFromNewsletter_081116 http://www.embeddeddesignindia.co.in/article/emailToFriend.do?articleId=8800551459&catId=2800006?ClickFromNewsletter_081116 http://www.eetindia.co.in/ART_8800539399_1800003_TA_b5d80fcf.HTM?ClickFromNewsletter_081116 http://www.eetindia.co.in/ART_8800549262_1800003_TA_7a340c55.HTM?ClickFromNewsletter_081116 http://www.eetindia.com

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EETimes India - November 16, 2008 Contents Farnell Embedded System Eases Rail Maintenance National Semiconductor Working With IT for Networked DAQ Digital Telemetry Advances Torque Measurement Events

EETimes India - November 16, 2008

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