Require Hardware Modifications Research Articles

Configurable Controller for High-Resolution LED Display Systems

Light-emitting diode (LED) display systems are implemented in various resolutions and aspect ratios to satisfy various display requirements. The requisite resolution and aspect ratio can be obtained by combining the appropriate LED panels. However, using different types of LED panels require using different types of LED controllers to drive them, which constitutes a rather burdensome design constraint. In addition, a driving circuit inside an LED panel may be modified to improve the display quality by adopting a new driving scheme or new LED elements. Furthermore, it may sometimes be necessary to create a completely new LED panel. All of these situations require the design of new LED controllers. In this paper, we, therefore, propose a configurable LED controller that can be used with various types of LED panels without requiring hardware modification or redesign. The proposed LED controller consists of an application-specific instruction-set processor (ASIP) and custom hardware. The ASIP is software programmable, and the custom hardware is employed to obtain a high operating speed. Moreover, the function of the custom hardware can be configured through the ASIP software program for generating the necessary address sequence to read the image bit plane memory and, consequently, to accommodate the target LED panel. Therefore, the proposed LED controller provides the advantages of flexibility and high-speed operation. The proposed LED controller was implemented using Xilinx Virtex-5, and it successfully drove LED panels having 64 × 96, 96 × 80, and 128 × 64 pixels at refresh rates of 3125, 2232, and 1736 Hz, respectively. An analysis of the operational capability indicates that, at the same refresh rate, the field-programmable gate array prototype of the proposed controller drives 1.44 times more pixels per unit time than a state-of-the-art commercial controller.

Capacitance measurement method using sinusoidal voltage injection in isolating phase‐shifted full‐bridge DC–DC converter output stage

When it comes to the reliability of power electronics, wear-out caused by ageing of electrolytic capacitors is a major concern. The capacitor ageing presents indicators such as a decrease in the capacitance and an increase in the equivalent series resistance, the detection of which can be used for capacitor health monitoring. In this study, the measurement of the output stage capacitance in an isolating DC–DC converter output stage is shown, which is used to assess the capacitor condition. In addition to presenting the method, fundamental issues related to the traditional capacitor ageing detection are discussed. The proposed method uses a sinusoidal voltage injection into the output voltage, which generates a current through the output stage capacitor. The capacitance is evaluated by the capacitor impedance, which is defined by the amplitudes of the applied voltage and the resulting capacitor current with the injection signal frequency. The method does not require hardware modifications to the converter or the measurement system, and it is executed online during the converter operation. The results show that the method is able to detect changes in the output stage capacitance regardless of the load.

Quantitative information extraction from gas sensor data using principal component regression

This paper presents a novel use of the principal component analysis (PCA) and regression methods for quantitative feature extraction from gas sensor data. In this approach, PCA plots are interpreted by observing the locations of samples in the principal component domain. A trainable data processing system that also produces numerical output is designed to validate the method. The main advantages of this system are: 1) retrainability: once it is trained, it can be used for any gas set; 2) flexibility: adaptation to different targets does not require hardware modifications (if a sufficient number and variety of sensors are installed in the sensor cell); and 3) simplicity: all computations are performed with only linear operators, and hence the system does not require complex structures or powerful computation resources. Several experiments are conducted using two industrial gases (toluene and ethanol) to validate the approach. The new approach is also compared with two classic principal component regression (PCR) methods. The results show that the new approach performs better than the classic PCR approaches.

Quadrature Imbalance Compensation With Ellipse-Fitting Methods for Microwave Radar Physiological Sensing

Accurate displacement measurement using quadrature Doppler radar requires amplitudes and phase imbalance compensation. Previously, this imbalance calibration has required cumbersome hardware modifications and thus can only be performed in a laboratory setting. Recently, a data-based method that does not require hardware modifications has been proposed. This simplifies the calibration process and allows the calibration to be performed on-site periodically. The method is called ellipse fitting. In this paper, the different factors affecting imbalance estimation accuracy, namely, arc length, initial phase angle, and noise level were thoroughly investigated. The Levenberg-Marquardt (LM) algorithm is proposed for the first time to increase the estimation accuracy as compared to the previously suggested algebraic fitting. Comprehensive simulations and experimental data show that the algebraic fitting method results in biased estimates. The proposed LM method has also been demonstrated to be more robust to noise, varying arc lengths, and different initial angles. The LM method reaches sufficient imbalance estimation accuracy with an arc length of 40% and a noise level of 1.5%.

Enabling Human–Machine Interaction in Projected Virtual Environments Through Camera Tracking of Imperceptible Markers

Existing tracking methods designed for interacting with projection-based displays generally require visible artifacts to be introduced in the environment in order to guarantee effective stability and accuracy. For instance, in optical-oriented approaches, either the camera sensor or the reference pattern used for tracking are often located within the user's sight (or interfere with it), thus occluding portions of the scene or altering the perception of the virtual environment. Several ways to tackle these issues have been recently explored. Proposed approaches basically aim at making the presence of tracking references in the virtual space transparent to the user. However, such solutions introduce possibly critical constraints on required hardware or environment configuration. In this work, a novel tracking approach based on imperceptible fiducial markers is proposed. The approach relies on a hiding technique that allows digital images to be embedded in (and retrieved from) a projected scene by exploiting the properties of light polarization and additive color mixing. In particular, the virtual scene is obtained by overlapping the light beams of two projectors and by dealing with markers’ hiding via color compensation. A prototype setup has been deployed, where interaction with a flat surface projection environment has been evaluated in terms of tracking accuracy and artifacts avoidance performance by using a consumer camera equipped with a polarizing filter. Although the performed tests presented in this article represent only a preliminary and a partial evaluation of the proposed approach, they provided encouraging results indicating that the proposed technique could be possibly applied in more complex interaction scenarios still with limited hardware requirements.

Note: Simultaneous measurement of transverse speed and axial velocity from a single optical beam

A method is introduced for simultaneously measuring transverse speed and axial velocity using a single optical beam and a standard photon Doppler velocimetry (PDV) sensing architecture. This result is of particular interest given the recent, widespread use of PDV and the fact that optical velocimetry has thus far been limited to measuring motion in one dimension per probe. Further, this result demonstrates that both axial velocity data and transverse speed data (at least qualitative) may be obtained entirely through signal analysis; not requiring hardware modification. This result is immediately relevant to analyses of existing PDV data and to future efforts in high-speed optical velocimetry.

Dual-scan acquisition for accelerated continuous-wave EPR oximetry

Statistical analysis reveals that, given a fixed acquisition time, linewidth (and thus pO2) can be more precisely determined from multiple scans with different modulation amplitudes and sweep widths than from a single-scan. For a Lorentzian lineshape and an unknown but spatially uniform modulation amplitude, the analysis suggests the use of two scans, each occupying half of the total acquisition time. We term this mode of scanning as dual-scan acquisition. For unknown linewidths in a range [Γmin, Γmax], practical guidelines are provided for selecting the modulation amplitude and sweep width for each dual-scan component. Following these guidelines can allow for a 3–4 times reduction in spectroscopic acquisition time versus an optimized single-scan, without requiring hardware modifications. Findings are experimentally verified using L-band spectroscopy with an oxygen-sensitive particulate probe.

Enhancing active vibration control of pedestrian structures using inertial actuators with local feedback control

Active vibration control (AVC) via inertial actuators is considered a viable technique for the mitigation of excessive vibrations in civil engineering structures. In particular, several recent field trials have shown that this technique has the potential to be effective for the cancellation of human-induced vibrations in pedestrian structures. However, prior to the implementation of AVC using inertial actuators, several drawbacks have to be dealt with. The main disadvantages come from the dynamic behaviour of the inertial actuators employed for this application, which are: (i) their low frequency dynamics (that might interact with the structure dynamics), and (ii) their nonlinearities (stroke and force saturation). Thus, any control technique to be implemented has to tackle stability problems (caused by the low frequency response of the actuators) and stroke and force saturation, which might lead to poor vibration cancellation performance. To alleviate such drawbacks, this work proposes to use an AVC strategy based on two control loops: (i) a loop, closed within the actuator, designed to artificially modify the actuator frequency response according to its maximum stroke and force and the structure dynamics, and (ii) a loop designed to impart damping to the structure. This work focuses on the design process such that stability and actuator saturations are taken into account to improve the efficiency of a given inertial actuator when the AVC system is based upon velocity feedback. Experimental results on a full-scale concrete laboratory structure using a commercial actuator are presented to illustrate the performance of the AVC strategy proposed, which ensures adaptability to a given structure without requiring hardware modifications.

Predictive‐focus illumination for reducing photodamage in live‐cell microscopy

Due to photobleaching and phototoxicity induced by high-intensity excitation light, the number of fluorescence images that can be obtained in live cells is always limited. This limitation becomes particularly prominent in multidimensional recordings when multiple Z-planes are captured at every time point. Here we present a simple technique, termed predictive-focus illumination (PFI), which helps to minimize cells' exposure to light by decreasing the number of Z-planes that need to be captured in live-cell 3D time-lapse recordings. PFI utilizes computer tracking to predict positions of objects of interest (OOIs) and restricts image acquisition to small dynamic Z-regions centred on each OOI. Importantly, PFI does not require hardware modifications and it can be easily implemented on standard wide-field and spinning-disc confocal microscopes.

Software Controlled Adaptive Pre-Execution for Data Prefetching

Data prefetching mechanisms are widely used for hiding memory latency in data intensive applications. They mask the speed gap between CPUs and their memory systems by preloading data into the CPU caches, where accessing them is by at least one order of magnitude faster. Pre-execution is a combined prefetching method, which executes a slice of the original code preloading the code and its data at the same time. Pre-execution is often mentioned in the literature, but according to our knowledge, it has not been formally defined yet. We fill this void by presenting the formal definition of speculative and non-speculative pre-execution, and derive a lightweight software-based strategy which accelerates the main working thread by introducing an adaptive, non-speculative pre-execution helper thread. This helper thread acts as a perfect predictor, calculates memory addresses, prefetches the data and consumes cache misses early. The adaptive automatic control allows the helper thread to configure itself in run-time for best performance. The method is directly applicable to any data intensive application without requiring hardware modifications. Our method was able to achieve an average speedup of 10–30% in a real-life application.

Enhancing spectral efficiency and capacity in synchronous OCDMA by transposed-MPC

This paper investigates a newly proposed spreading code-set based on the prime code (PC) families referred to as ‘transposed modified prime codes (T-MPC)’ for the enhancement of spectral efficiency of synchronous incoherent optical code-division multiple-access (OCDMA) networks. This code family increased the code-set cardinality up to twice of existing PC families’ size. This also implies that a greater number of users can be accommodated by the network. Since there is no longer a time-shift feature in T-MPC like in conventional modified prime codes (MPC), the code is not predictable and thus even more secure. Since the code structure is similar to MPC, its deployment in a system/network already running MPC will not require hardware modification. Due to the higher code utilization factor of T-MPC, a greater number of users are accommodated under certain bit-error rate (BER) resulting in remarkable improvement in the spectral efficiency (SE) and capacity. The T-MPC compatibility with low-weight energy-efficient MPC construction is also investigated. The BER and SE performances are analyzed and compared with existing code families. The results indicated that the T-MPC employment can improve up to 50% higher spectral efficiency.

Unconstrained and Contactless Hand Geometry Biometrics

This paper presents a hand biometric system for contact-less, platform-free scenarios, proposing innovative methods in feature extraction, template creation and template matching. The evaluation of the proposed method considers both the use of three contact-less publicly available hand databases, and the comparison of the performance to two competitive pattern recognition techniques existing in literature: namely Support Vector Machines (SVM) and k-Nearest Neighbour (k-NN). Results highlight the fact that the proposed method outcomes existing approaches in literature in terms of computational cost, accuracy in human identification, number of extracted features and number of samples for template creation. The proposed method is a suitable solution for human identification in contact-less scenarios based on hand biometrics, providing a feasible solution to devices with limited hardware requirements like mobile devices.

Advantages of Selective Change-Driven Vision for Resource-Limited Systems

Selective change-driven (SCD) vision is a capture/processing strategy especially suited for vision systems with limited resources and/or vision applications with real-time constraints. SCD vision capture essentially involves delivering only the pixels that have undergone the greatest change in illumination since the last time they were read-out. SCD vision processing involves processing a limited pixel flow with similar results to the usual image flow, but with far lower bandwidth and processing requirements. SCD vision is based on pixel flow processing instead of traditional image flow processing. This complete change in the way video is processed and has a direct impact on the processing hardware required to deal with visual information. In this paper, we present the first CMOS sensor using the SCD strategy, along with a highly resource-limited system implementing an object tracking experiment. Results show that SCD vision outperforms traditional vision systems by at least one order of magnitude, with limited hardware requirements for the specific tracking experiment being tested.

Optimization of pulse train presaturation for CEST imaging in clinical scanners

Chemical exchange saturation transfer (CEST) imaging depends on the performance of radiofrequency saturation during the experiment. Scanner specifications, in particular limited pulse width and duty-cycle, and specific absorption rate guidelines restrict the full exploitation of CEST effects in clinical MR systems. The purpose of this study was to optimize techniques for effective pulse train presaturation for CEST imaging in a whole-body MR scanner. Theoretical analysis and simulations of the spectral properties of radiofrequency pulse trains demonstrated the significance of pulse width τ(P) and interpulse delay τ(D) for effective and selective labeling of a chemically exchanging proton pool. CEST experiments with model solutions, e.g., creatine dissolved in water, showed best performance of pulse trains with τ(P) = τ(D) = 100 msec, regarding minimum direct water saturation in z-spectra and distinct magnetization transfer ratio asymmetry that can be determined quantitatively. Saturation efficiency of trains of Gaussian-shaped radiofrequency pulses using this timing was evaluated in MR imagers with field strengths of 1.5, 3, and 7 T. The proposed saturation pulse train does not require hardware modifications, offers low specific absorption rate, and can be used in a standard clinical setup.

Frequency-Steered Acoustic Arrays: Application to Structural Health Monitoring of Composite Plates

This paper presents the design, characterization, and application of periodic piezoelectric actuator arrays for structural health monitoring. In the proposed array configuration, all elements are activated simultaneously to achieve strong frequency-dependent directional actuation, which allows beam steering through a sweep of the excitation frequency and limited hardware requirements. The array enables in situ monitoring of critical components through strongly focused actuation and directional scanning capabilities. The concept is illustrated for a selected design with quadrilateral topology on an isotropic plate. The application to composite panels is also specifically discussed by illustrating the complexity of the corresponding dispersion properties, which suggest design challenges for mode tuning. A quadrilateral design is tested for excitation of the A0 mode on a selected lay-up sequence to illustrate the generality of the proposed concept and its applicability to composites.

Two-dimensional periodic actuators for frequency-based beam steering

The paper investigates innovative designs of piezoelectric actuators for structural healthmonitoring (SHM). Periodic configurations are proposed as an effective means to provideactuators and sensors with strong, frequency dependent directional characteristics, whichallow beam steering through a sweep of the excitation frequency. The concept has thepotential to enable in situ monitoring of critical components through strongly focusedactuation (and/or sensing) and directional scanning capability, which may be achieved withvery limited hardware requirements. Beam steering is achieved by exploiting interferencephenomena generated by the spatial periodicity of the array and the simultaneousactivation of its components. Such interference phenomena produce waves withfrequency dependent directional characteristics, which allow directional scanning tobe performed simply through a frequency sweep. The need for beam-formingalgorithms and associated hardware is thus avoided. The concept is illustrated byconsidering 2D arrays of point sources of various topologies. The case of a thinmembrane supporting the propagation of SV waves is first presented to provide asimple frame work of analysis. The case of Lamb waves in a thin plate is thenconsidered to demonstrate the validity and the practicality of the proposed approach.

TU-D-304A-03: Temporal Resolution Improvement Using PICCS in MDCT Cardiac Imaging

Purpose: The current paradigm for temporal resolution improvement is to add more source‐detector units and/or increase the gantry rotation speed. The purpose of this letter is to present an innovative alternative method to improve temporal resolution by at least a factor of 2 for all MDCT scanners, without requiring hardware modification. Methods: The central enabling technology is a most recently developed image reconstruction method: Prior Image Constrained Compressed Sensing (PICCS). Using the method, cardiac CTimages can be accurately reconstructed using projection data acquired in an angular range of about 120 degrees, which is roughly 50% of the standard short‐scan angular range (∼240 degrees for an MDCT scanner). As a result, the temporal resolution of MDCT cardiac imaging can be universally improved by approximately a factor of 2. In order to validate the proposed method, two in vivo animal experiments were conducted using a state‐of‐the‐art 64‐slice CTscanner(GE Healthcare, Waukesha, WI) at different gantry rotation times and different heart rates. One animal was scanned at heart rate of 83 beat per minute (bpm) using 400ms gantry rotation time and the second animal was scanned at 94bpm using 350ms gantry rotation time respectively. Results: Cardiac coronary CTimaging can be successfully performed at high heart rates using a single source MDCT scanner with gantry rotation time of 400ms and 350ms. Conclusions: Using the proposed PICCS method, temporal resolution of cardiac CTimaging can be effectively improved by approximately a factor of two without modifying any scanner hardware. This potentially provides a new method for single source MDCT scanners to achieve motion artifact‐free coronary CTimaging for most patients without prescription of beta blocker. This method also enables dual source MDCT scanner to achieve higher temporal resolution without further hardware modifications.

Temporal resolution improvement using PICCS in MDCT cardiac imaging

The current paradigm for temporal resolution improvement is to add more source-detector units and/or increase the gantry rotation speed. The purpose of this article is to present an innovative alternative method to potentially improve temporal resolution by approximately a factor of 2 for all MDCT scanners without requiring hardware modification. The central enabling technology is a most recently developed image reconstruction method: Prior image constrained compressed sensing (PICCS). Using the method, cardiac CT images can be accurately reconstructed using the projection data acquired in an angular range of about 120 degrees, which is roughly 50% of the standard short-scan angular range (approximately 240 degrees for an MDCT scanner). As a result, the temporal resolution of MDCT cardiac imaging can be universally improved by approximately a factor of 2. In order to validate the proposed method, two in vivo animal experiments were conducted using a state-of-the-art 64-slice CT scanner (GE Healthcare, Waukesha, WI) at different gantry rotation times and different heart rates. One animal was scanned at heart rate of 83 beats per minute (bpm) using 400 ms gantry rotation time and the second animal was scanned at 94 bpm using 350 ms gantry rotation time, respectively. Cardiac coronary CT imaging can be successfully performed at high heart rates using a single-source MDCT scanner and projection data from a single heart beat with gantry rotation times of 400 and 350 ms. Using the proposed PICCS method, the temporal resolution of cardiac CT imaging can be effectively improved by approximately a factor of 2 without modifying any scanner hardware. This potentially provides a new method for single-source MDCT scanners to achieve reliable coronary CT imaging for patients at higher heart rates than the current heart rate limit of 70 bpm without using the well-known multisegment FBP reconstruction algorithm. This method also enables dual-source MDCT scanner to achieve higher temporal resolution without further hardware modifications.

Genetic Optimization for Pulsed-Power System Configuration

Pulsed-power systems traditionally have been designed to provide a pulse that is non programmable or requires hardware modifications to adjust the output waveform shape. Advancements in pulsed-power technologies are enabling system designs that allow for greater flexibility such as programmable current shaping. Material science, which uses current pulse shaping to obtain data for the equation of state analysis, is driving much of this work. The programming of pulsed-power systems through the use of simulations and manual curve fitting techniques can work well for systems that only have a few controllable parameters and are generating waveforms with simple spectral content. Complex systems with many controllable parameters become unmanageable for manual trial and error to be effective. This paper discusses the characterization and modeling of a scaled down programmable current adder directed at investigating technical issues that will be encountered in full-scale drivers. A discussion of the procedure used to optimize the adder current output, using genetic algorithms, is presented. The approach to system programmability presented in this paper will allow for a more simplified user interface and system control, as the requirements for flexibility and complexity in future systems increase.

An Embedded System for Position and Speed Measurement Adopting Incremental Encoders

This paper presents an embedded digital system for incremental encoders allowing for high dynamic performance and accuracy speed measurement in all the operating conditions for the application in digital servo drives. The idea aims at embedding processing capabilities inside traditional position transducers in order to develop a smart measuring system. The base processing algorithm employs a novel mixed time and frequency measurement technique of the encoder signals. The iterative formulation of the algorithm and the limited hardware requirements allows its implementation by means of a standard microcontroller (e.g., TMS320F24x) or by dedicated hardware. Communication between the smart sensor and the servo drive is preliminarily realized via high-speed serial peripheral interface.