Showing papers in "IEEE Instrumentation & Measurement Magazine in 2007"

Microwave and millimeter wave nondestructive testing and evaluation - Overview and recent advances

Abstract: This article focuses on three recent applications of microwave and millimeter wave NDTE 2) corrosion and precursor pitting detection in painted aluminum and steel substrates; and 3) detection of flaws in spray-on foam insulation and the acreage heat tiles of the Space Shuttle through focused and synthetic imaging techniques. These applications have been performed at the Applied Microwave Nondestructive Testing Laboratory (amntl) at the University of Missouri-Rolla.

The Potential of Haptics Technologies

Abstract: In spite of the significant recent progress, the incorporation of haptics into virtual environments is still in its infancy due to limitations in the hardware, the cost of development, as well as the level of reality they provide. Nonetheless, we believe that the field will one day be one of the groundbreaking media of the future. It has its current holdups but the promise of the future is worth the wait. The technology is becoming cheaper and applications are becoming more forthcoming and apparent. If we can survive this infancy, it will promise to be an amazing revolution in the way we interact with computers and the virtual world. The researchers organize the rapidly increasing multidisciplinary research of haptics into four subareas: human haptics, machine haptics, computer haptics, and multimedia haptics

UWB short-range radar sensing - The architecture of a baseband, pseudo-noise UWB radar sensor

Abstract: The pioneers of radio science made their first trials of wireless information transmission and demonstrated localization of a steel vessel by radio waves more than 100 years ago. Back then, the world of radio frequencies was organized in a very simple way. The researchers could use any frequency band. There was no interference by others and no controlling government bodies. Since then, governmental authorities have established tight regulations that have split up the available frequency band into small partitions for exclusive use. This article discusses the architecture of a baseband, pseudo-noise UWB radar and gives some examples of applications

Genetic algorithms for autonomous robot navigation

Abstract: Engineers and scientists use instrumentation and measurement equipment to obtain information for specific environments, such as temperature and pressure. This task can be performed manually using portable gauges. However, there are many instances in which this approach may be impractical; when gathering data from remote sites or from potentially hostile environments. In these applications, autonomous navigation methods allow a mobile robot to explore an environment independent of human presence or intervention. The mobile robot contains the measurement device and records the data then either transmits it or brings it back to the operator. Sensors are required for the robot to detect obstacles in the navigation environment, and machine intelligence is required for the robot to plan a path around these obstacles. The use of genetic algorithms is an example of machine intelligence applications to modern robot navigation. Genetic algorithms are heuristic optimization methods, which have mechanisms analogous to biological evolution. This article provides initial insight of autonomous navigation for mobile robots, a description of the sensors used to detect obstacles and a description of the genetic algorithms used for path planning.

An introduction to FFT and time domain windows

Abstract: This paper includes a brief tutorial on digital spectrum analysis and FFT-related issues to form spectral estimates on digitized signals. Some review of the DFT has been presented, and some discussion on the computational advantages of the FFT calculation has also been presented. Finally, the main considerations on windowing and window characteristics have been briefly discussed.

Microwave Measurements Part II Non-linear Measurements

Abstract: By convention, radio frequency (RF) and microwave frequencies range between 30 MHz and 300 GHz. Conversely, this means their wavelengths range between 10 m and 1 mm. Intense research in radar development during World War II extended the RF spectrum beyond the usual applications in radio communications. The use of shorter wavelengths resulted in laboratory equipment with proportionally smaller dimensions to generate, convey, transmit, and detect higher-frequency signals. Wavelengths shorter than 1 mm require equipment too small to be realized. Voltage, current, and impedance concepts lose their conventional meanings when the operating wavelength is approximately equal to the dimensions of the structures under test. The behavior of propagating electromagnetic waves must then be analyzed in terms of electric and magnetic field. Unfortunately, no simple and direct way exists to measure these quantities, so we must resort to indirect methods. In the following sections, we briefly review the concept and need for measurements of scattering parameters. We also describe the two key instruments for microwave measurements: VNAs and spectrum analyzers.

An Introduction to FFT and Time Domain Windows Part 11 in a series of tutorials in instrumentation and measurement

Abstract: A student in a digital signal processing class once asked an insightful set of questions. They went something like this: "Professor, can you explain why we spend so much of our time describing signals in the frequency domain? We first examined circuits in terms of their sinusoidal steady-state response. We then went on to study Fourier series and Fourier transforms, and we are now studying sampled data Fourier transforms, and the Discrete Fourier transform, all based on sinusoids and sampled data sinusoids. Why not use other basis functions? What is so special about sinusoids?" Great questions! We wish we had thought to ask them! The answers are simple. Many of the dynamic systems we analyze, synthesize, design, develop, and operate can be approximated by linear time invariant systems modeled by linear, constant-coefficient, differential equations, So now the question is, "What does that mean?" It means this: it we differentiate a sinusoid, it is still a sinusoid. If we form a weighted sum of derivatives of a sinusoid, the sum is still a sinusoid. The sinusoid never stops being a sinusoid. No other wave shape can make that claim! The sinusoids preserve their identity in a linear system; the system can change the sinusoid's amplitude and phase but it cannot change its basic structure. Sinusoids are eigenfunctions of linear, constant-coefficient, differential equations. As such, the sinusoids can be used to analyze and characterize the linear system. The collection of amplitude and phase changes experienced by sinusoids of different frequencies passing through the system compactly describes the system. We call this description its frequency response. The frequency response is intimately tied to the system's transfer function and its differential equation. The Fourier transform is a Iso used to describe signals in the time or spatial domains. We limit our discussion here to time domain descriptions. Signals of interest are decomposed into a set of complete orthonormal basis functions, the real sines and cosines, or, equivalently, the set of complex exponentials [3]. The classic Fourier transform is the mechanism that performs this decomposition, leading to a frequency domain description of the signal. There are several advantages to analyzing signals in the frequency domain.

A Tour of the Tour of the Hilbert-Huang Transform: An Empirical Tool for Signal Analysis

Abstract: The HHT provides an alternative tool for signal analysis. Case studies in applying the HHT technique for bearing degradation monitoring and machine tool breakage detection have demonstrated its effectiveness for revealing the non-stationary and non-linear features hidden in dynamic signals. In addition to the application illustrated in this article, the HHT technique has shown to be effective in other applications, such as biomedical engineering [8], [9], system identification [10], [11], environmental monitoring [12], or financial analysis [13]. Because of its empirical nature, rigorous mathematical proof of this technique has remained an active research topic. More interesting reports are to be expected on the application of this technique for solving various types of real-world problems.

Measurement of microwave power - A review of techniques used for measurement of high-frequency RF power

Abstract: Measurement of the signal amplitude of radio frequency (RF) waves is an important function in a wide range of applications. Some of these applications are signal-level adjustment and verification for radar and communication radio and measurements made to control and ensure safety in industrial and home microwave heating processes. Frequencies that are normally considered to be "microwave" are typically those above 1 GHz, although the same power measurement techniques used at 1 GHz are successfully applied at lower frequencies. Common commercial coaxial RF power instruments will, for example, often be calibrated over a range of 10 MHz to 26.5 GHz, with calibrations at frequencies as low as 9 kHz and as high as 50 GHz used at times. This article introduces and reviews the techniques used for measurement of high-frequency RF power and for establishing traceability of the measurements to national standard units

Advanced Optical Sensors for Power and Energy Systems Applications

Abstract: We have highlighted how optical sensors can be exploited to solve many measurement problems within selected power and energy systems applications. Clearly, their development is defined at present by the industry demand, often unsatisfied with the functionality and performance of electrical instrumentation. In these cases, the overall gain from being able to monitor a plant will outweigh the higher cost associated with optical measurement systems. However, as the technology advances and costs decrease, it is hoped that photonic sensors will make their way into more areas of industry and become as widely accepted as a simple strain gauge or thermocouple. We hope that this article will provide a useful perspective and will inspire a renewed interest in photonic sensors among a broad range of researchers, engineers, and industrial end-users involved in the field of instrumentation and measurement

Approximations to Error Functions

Abstract: This paper addresses approximations to error functions and points out three representative approximations, each with its own merits. Cody's approximation is the most computationally intensive of the three, it is not overly so, and there is no arguing over its accuracy. The other two approximations are much simpler computationally, and they both yield accuracies that would be considered more than sufficient in most practical situations. Absolute relative error provides an effective measure of goodness, and, for approximations to the Q-function, it also places a loose bound on the absolute error in the approximation. Cody's approximation is an effective surrogate for the true error function; the values provided by that approximation match the actual values of the error function to within roughly the precision of double-precision floating point arithmetic.

Applying test driven development to embedded software

Abstract: Test driven development (TDD) is increasing in information technology applications and product development; however, it has not been widely applied in embedded software development. Embedded developers face many challenges. TDD can help overcome some of these challenges, but TDD has to be adapted for embedded systems development. TDD is an important software development practice that can help embedded developers deliver higher quality products. The embedded TDD cycle can help take hardware availability off the software critical path, enabling steady progress with or without hardware. TDD can be used for embedded development in C and C++. Java may also be an option for some embedded systems, and Java is better suited for TDD, as the tools for Java support are much more advanced.

Electronic Prognostics - A Case Study Using Switched-Mode Power Supplies (SMPS)

Abstract: This paper describes the process, used to develop prognostics algorithms for a commercially available switched-mode power supply (SMPS) using corroborative evidence sources. The process begins with a Pareto analysis indicating the primary modes of failure. Critical components are identified using a three-tier failure mode and effects analysis (FMEA) by investigating device, circuit, and system parameters sensitive to degradation. Once acceleration factors, or sources of degradation, are known damage accumulation failure models for each critical component are derived from highly accelerated life tests (HALT). Then, healthy components are systematically degraded to varying levels of severity by performing highly accelerated stress testing (HAST). These components are used in seeded fault tests to identify system-level parameters sensitive to device damage. Features extracted from data recorded during seeded fault tests are used to derive feature-based failure models. Finally, reasoning and data fusion algorithms are applied to both models to generate corroborative remaining useful life (RUL) predictions.

Micrtowave measurements. Part I: Linear measurements

Abstract: By convention, radio frequency (RF) and microwave frequencies range between 30 MHz and 300 GHz. Conversely, this means their wavelengths range between 10 m and 1 mm. Intense research in radar development during World War II extended the RF spectrum beyond the usual applications in radio communications. The use of shorter wavelengths resulted in laboratory equipment with proportionally smaller dimensions to generate, convey, transmit, and detect higher-frequency signals. Wavelengths shorter than 1 mm require equipment too small to be realized. Voltage, current, and impedance concepts lose their conventional meanings when the operating wavelength is approximately equal to the dimensions of the structures under test. The behavior of propagating electromagnetic waves must then be analyzed in terms of electric and magnetic field. Unfortunately, no simple and direct way exists to measure these quantities, so we must resort to indirect methods. In the following sections, we briefly review the concept and need for measurements of scattering parameters. We also describe the two key instruments for microwave measurements: VNAs and spectrum analyzers.

A Bayesian Approach to Sensor Fusion in Autonomous Sensor and Robot Networks

Abstract: This article describes some of the current challenges in autonomous sensor and robot networks, with special focus on issues concerning the fusion of information from several sensors to improve the accuracy in the cooperative localization of objects or to help the wide-sense networked sensors to self-localize. Although many other approaches exist, the focus is on Bayesian approaches to sensor fusion and state estimation.

Robots with Sensitive Feet

Abstract: Research has shown that human balance control is dependant on force feedback provided by pressure sensed by the human sole Consequently, for the vital functions of walking and standing on our legs, our sensitive feet play a very prominent role However, biped robots have rarely been provided with sensing in the soles of their feet, except for a few cases where the forces at two or three points are measured We have built a pilot system to measure foot-sole pressure for a robot's feet during walking It uses resistive force sensor arrays to help create pressure maps of the sole

Navigation Aids for the Visually Impaired: From Artificial Codification to Natural Sensing

Abstract: The article discusses the application of new methods and the development of more convenient assisting devices for the visually impaired. Emphasis is given to several design aspects.

Autonomous Navigation: Achievements in Complex Environments

Abstract: During the past decade, an explosion of interest in the estimation of an autonomous robot's location state and that of its surroundings, known as simultaneous localization and map building (SLAM), is evident. The goal of an autonomous vehicle performing SLAM is to build a map incrementally by using the uncertain information extracted from its sensors, while simultaneously using that map to localize itself with respect to a reference coordinate frame. To demonstrate the state of the art in autonomous navigation, this article focuses on outdoor research work within complex, semi-structured environments with an array of vehicles, using RADAR and laser range finders. Two classes of sensors that we use to get information are proprioceptive sensors and exteroceptive sensors. This paper focuses on sensor data interpretation, information extraction, and data association.

Finite Arithmetic Considerations for the FFT Implemented in FPGA-Based Embedded Processors in Synthetic Instruments

Abstract: An important trend in the synthetic instrument community is the development of products around the capabilities of field programmable gate array (FPGA) based embedded processors. It is assumed here that signals arrive at the FPGA input at high data rates, low to medium data bit width, and low to medium signal-to-noise ratio. As a consequence of the processing that reduces signal bandwidth, the data bit width is increased in concert with the increased signal-to-noise ratio resulting from the reduced bandwidth. The FPGA has the unique capability to allocate its internal resources in an optimal way to best match the dynamic range of the sampled data signal at various points in the signal flow path. Since the fast Fourier transform (FFT) is primarily a tool in the synthetic instrument, the effect of fixed point arithmetic on its performance is reviewed, and suggested bit width assignments for FFT algorithms are presented. Computational noise in the FFT is due to finite bit width input data, finite bit width sine-cosine tables, finite bit width multipliers and accumulators, and distributed scaling between data passes. The noise generated by these contributors is not uniform over the frequency band and a number of mechanisms to minimize the noise contribution to the measurement process performed by the synthetic instrument are presented.

An Autonomous Unmanned Ground Vehicle for Non-Destructive Testing of Fiber-Reinforced Polymer Bridge Decks

Abstract: The use of fiber-reinforced polymer (FRP) composite bridge decks is increasing in many civil engineering applications because of its many useful properties. The traditional reinforced concrete bridge decks have steel reinforcing bars embedded in concrete. Because of the use of deicing salt on the bridges to melt snow and ice in winter, the reinforcing bars tend to corrode, thus reducing the life span of the reinforced concrete bridge decks by half (from about 50 yr to about 25 yr). The FRP composite decks are made of noncorrosive material and offer a higher strength-to-weight ratio as compared to the reinforced concrete decks. It is highly important that engineers know how to detect subsurface defects that can form in FRP decks, which may cause serious structural degradation and endanger structural integrity. Both infrared thermography (IRT) and ground penetrating radar (GPR) have shown promise in the field of non-destructive detection of defects. Instead of performing both analysis methods individually, it would be more cost effective for someone to conduct both IRT and GPR at the same time. Research at West Virginia University has produced an unmanned ground vehicle (UGV) that will acquire data from both GPR and IRT systems to create a combined defect map of the FRP bridge deck to better analyze the results. Thus, the proposed UGV enables rapid data acquisition from the FRP bridge deck in an automated and non-destructive fashion, which minimizes human error. The UGV also incorporates data analysis algorithms, which help in producing a detailed map showing the layout of defects on the bridge deck.

A model-based approach to sequential fault diagnosis - A best student paper award winner at IEEE Autotestcon 2005

Abstract: Fault diagnosis is crucial for the reduction of test and integration time as well as downtime of complex systems. In this article, we present a model-based approach to derive tests and test sequences for sequential fault diagnosis. This approach offers advantages over methods that are based on test coverage of explicit fault states, represented in matrix form. Functional models are more easily adapted to design changes and constitute a complete information source for test selection on a given abstraction level. We introduce our approach and implementation with a theoretical example. We demonstrate its practical use in three case studies, and for these cases we obtain cost reductions of up to 59% compared to the matrix-based approach

A Wireless Hydrocarbon Pollution Measuring and Monitoring System

Abstract: The goal of the proposed system is to protect sensitive areas of the country from hydrocarbon pollution with the use of a global system for mobile communications/general packet radio service (GSM/GPRS) accessed from mobile observation points (MOPs). The primary applications of this system are detection of leaks from an underground or aboveground storage tank (UST/AST), monitoring waste water discharge/ monitoring bilge water, monitoring water quality, monitoring groundwater, monitoring oil-water separators, monitoring storm drain effluents, and static soil gas headspace analysis. The basic version of the system is equipped with: a GPS position locator, a contamination probe sensitive to hydrocarbons, and a GSM/GPRS connection with the central www server

instrumentation notes - A USB-Enabled, FLASH-Disk-Based Data Logger

Abstract: A data logger is a device for measuring and storing data. It is an all-purpose piece of measurement equipment that finds use in an extremely wide range of applications. In principle, a data logger is a relatively simple piece of equipment; as always, the devil is in the details. A well-constructed data logger should be a joy to work with; a poorly designed data logger can easily drive an engineer to tears. Data loggers, in one form or another, have existed for many years. In this article, we describe a reasonably easy to implement data logger that makes measurements using a microcontroller's on-chip analog-to-digital converter (ADC) and makes use of two rather new technologies. Our data logger stores data on a removable FLASH disk, and it knows how to communicate with a computer using the universal serial bus (USB) standard

Universal Magnetic Circuit for Resolvers with Different Speed Ratios [Instrumentation Notes]

Abstract: This paper proposes a universal magnetic circuit for resolvers with different speed ratios. A resolver is an electromechanical transducer that converts the angular position of a rotor into an electric signal. The analysis and test results led to the conclusion that by using an appropriate magnetic material and assuring high-precision manufacturing it is possible to obtain high-precision resolvers with electrical error well below 1 minute of arc. Also it was proved that by using a single type of magnetic circuit it is possible to create multipole, two-speed resolvers. This system is used to improve both accuracy and resolution of angle measurement.

In-Situ, Real-Time Detector for Faults in Solder Joint Networks of Operational, Fully-Programmed Field Programmable Gate Arrays (FPGAs)

Abstract: Introduced is an innovative, in-situ solder-joint built-in self-test (SJ BISTtrade) to detect high-resistance damage to solder-joint networks of fully operational field programmable gate arrays (FPGAs) in ball-grid array (BGA) packages such as a XILINXreg FG1152/FG1156. FPGAs are used in all manner and kinds of control systems in both defense and commercial applications.