Noise Tracking Research Articles

이동통신 단말기 카메라의 손떨림 보정 장치의 H∞제어

Article history: This study proposes a closed-loop shaping control method with H∞ optimization for optical image stabilization (OIS) in mobile phone cameras. The image stabilizer is composed of a horizontal stage constrained by ball bearings and actuated by the magnetic force from voice coil motors. The displacement of the stage is measured by Hall effect sensors. From the OIS frequency response experiment, the transfer function models of the stage and Hall effect sensor were identified. The weight functions were determined considering the tracking performance, noise attenuation, and stability with considerable margins. The H∞ optimal controller was executed using closed-loop shaping and limiting the controller order, which should be less than 6 for real-time implementation. The control algorithm was verified experimentally and proved to operate as designed.

The Simulation of Speech Enhancement Based on Variable Leaky LMS Algorithm

In order to eliminate the speech signal fading induced by noise, this paper proposes a new variable leaky LMS algorithm on the basis of the adaptive filter in combination with the advantages of the leakage LMS algorithm and the variable step size LMS algorithm, and analyzes its principle. After the new algorithm is used to simulate speech with noise, the result shows that the proposed algorithm has a good ability to suppress Gaussian noise and excellent tracking performance, proving the correctness of the algorithm and the feasibility of simulation.

Design and Realization of an Embedded Control Fin Drive

The huge developments in embedded systems in addition to its availability for civilian applications in low cost, size and weight attract the researchers in the field of navigation, guidance and control all over the world towards the embedded flight control and autopilots. One of the flight control subsystems is the control fin drive that is responsible of the flying vehicle fins motion control. This paper is devoted to the design and implementation of embedded control fin drive that can be utilized with different guided vehicles such as guided missiles, guided munitions, and unmanned aerial vehicles (UAVs). The design includes calibration of available actuators and feedback sensors in addition to the design of conditioning networks, interfacing and classical controller to stabilize this subsystem and achieve the performance requirements. Also, the design justified against disturbance and measurement noises. The tests conducted with the designed hardware and the available actuator via the Hardware in the Loop (HIL) simulation show good performance concerning tracking, disturbance rejection and measurement noise. However, the controller necessitates extra tuning to become less sensitive to noises, which is the objective for future work.

A robust anomaly based change detection method for time-series remote sensing images

Time-series remote sensing images record changes happening on the earth surface, which include not only abnormal changes like human activities and emergencies (e.g. fire, drought, insect pest etc.), but also changes caused by vegetation phenology and climate changes. Yet, challenges occur in analyzing global environment changes and even the internal forces. This paper proposes a robust Anomaly Based Change Detection method (ABCD) for time-series images analysis by detecting abnormal points in data sets, which do not need to follow a normal distribution. With ABCD we can detect when and where changes occur, which is the prerequisite condition of global change studies. ABCD was tested initially with 10-day SPOT VGT NDVI (Normalized Difference Vegetation Index) times series tracking land cover type changes, seasonality and noise, then validated to real data in a large area in Jiangxi, south of China. Initial results show that ABCD can precisely detect spatial and temporal changes from long time series images rapidly.

Improved PI controller based on predictive functional control for liquid level regulation in a coke fractionation tower

Due to limitations of hardware, cost and so on, the application of proportional-integral-derivative (PID) control is more convenient than predictive control. However, predictive control usually has better performance than traditional PID control, thus it is important to combine the advantages of these two control algorithms. A novel PI controller optimized by predictive functional control (PFC) is proposed and tested on liquid level in the industrial coke fractionation tower in this paper. Since this kind of process always shows the integrating behavior, a P controller is first used for it to generate a self-balancing generalized process, then the PFC based PI control is designed for the generalized process. The resulting controller displays the performance of both PFC and PI control with easy implementation in practice. The performance of the proposed PI controller is compared with traditional PI controller in terms of regulatory/servo set-point tracking, disturbance rejection and measurement noise issues, from which results show that the proposed PI controller provides better performance than traditional PI controller.

Quantification of Directional Migration by a Characteristic Directionality Time

Many cell types can bias their direction of locomotion by coupling to external cues. Characteristics such as how fast a cell migrates and the convolution of its migration path can be quantified to provide metrics that determine which biochemical and biomechanical factors affect directional cell migration, and by how much. To be useful, these metrics should be reproducible from one experimental setting to another, and the resulting quantitative analysis should describe the underlying processes that occur in the system. In this work, several metrics used to characterize cell migration, such as turning angle distribution and straightness index, are evaluated in the context of reproducibility and quantitative interpretability. We discuss how these existing metrics can be modified to be more reproducible, and introduce a new metric called directionality time that can be used to characterize convolution of the migration path. Directionality time is measured based on fitting the slope of the mean squared displacement in log-log coordinates. We apply three selected random walk models to demonstrate that the functional form of the fit equation is approximately model invariant. Directionality time is reproducible because the numeric result takes into account tracking noise and is independent of the time interval of path measurement, the two variables that tend to change from one experiment to another. The robustness of this metric is tested via computer simulation and against experiment data of neutrophils directionally migrating towards a chemoattractant.

Motion Control of Vehicles with Trailers Using Transverse Function Approach

This paper is focused on analysis of the control solution using the transverse function approach. The controller considered here is designed for a nonholonomic vehicle with on-axle passive trailers. The main problem investigated is the optimal parametrization of the transverse functions in order to ensure low sensitivity to the measurement noise and high tracking accuracy. Theoretical analysis referring to transverse function scaling using dilation is illustrated by results of extensive numerical simulations. Taking into account these results the controller properties are considered. Finally, possibility of the controller implementation is discussed.

Using fuzzy logic control for the robust carrier tracking loop in a Global Positioning System/Inertial Navigation System tightly integrated system

The noise bandwidth is an important parameter on the Global Positioning System (GPS) tracking loop; the larger the bandwidth the better the high dynamic performance, but the thermal noise suppression capability is reduced. In a GPS/Inertial Navigation System (INS) tightly integration system, the GPS receiver’s carrier phase lock loops (PLLs) are aided by the Doppler shift from the INS, which can reduce user most dynamics. So the noise bandwidth can be narrowed to decrease the thermal noise tracking errors. However, due to the inertial sensor errors, the external INS-derived Doppler shift information are not completely accurate, therefore a Doppler-aiding error-induced phase error source must exist. The part of tracking error is derived in this paper. Other error sources are still present, so the bandwidth of PLLs cannot be set arbitrarily. This paper applies one artificial intelligence technique, the fuzzy logic controller (FLC), to calculate the PLL noise bandwidth on-line. Simulation results prove that the proposed FLC-based software receiver does achieve a superior tracking ability over conventional tracking loops in complicated conditions. In addition, the proposed algorithm works in the real-time mode and can be used in many practical applications.

Statistical Energy Analysis of Subway Wheel/Track Noise

Dividing wheel-track system of subway into a series of sub-systems, the statistical energy analysis (SEA) model of wheel/track system is established. The factors affecting the wheel/track noise, such as modal density, damping loss factors, coupling loss factors, are gotten by theoretical analysis combined with experiments. The calculated results show that the track noise is about 4.5 dB(A) higher than the wheel noise at 160 km/h, and the wheel noise is reduced by 2.8 dB(A) at 160 km/h and by 2.3 dB(A) at 90 km/h by attaching damped layer plates to the wheels, but the total reduction is only 0.9 dB(A) at 160 km/h and 0.4 dB(A) at 90 km/h, so the attempts to reduce the total noise should exert noise control measures on the track, not on the wheel.

Tracking Underwater Noise Sources with the Use of a Passive Method

It is possible to track a source of noise by determining the intensity of sound that informs about the sound energy ow direction. One of the methods of determining the sound intensity of acoustic signals is the so-called gradient method in which the pressure is measured with the use of two hydrophones placed close to each other. Tetrahedral antenna consists of four hydrophones spaced at regular tetrahedron vertices so that distances between hydrophones are the same. The tetrahedral antenna determines six virtual points in the middle of each edge and allows using sound intensity calculation algorithm to determine the noise source bearing. In our experiment, the antenna was located 23 meters below the sea surface and a source of noise was moving over it. The object that was moving along a straight line with a speci c course was equipped with a GPS receiver. This allowed comparison of the obtained targeting results with the real track of moving object. The paper presents the object tracking algorithm which was implemented in the MATLAB environment as well as some of the results of research carried out on passive source noise tracking.

Femtoampere integrated current preamplifier for low noise and wide bandwidth electrochemistry with nanoelectrodes

The direct tracking of the potential-induced modulation of the double layer capacitance (100mV bias steps resulting in 1.2fF variations) of Pt nanoelectrodes (100nm diameter) in physiological solution with sub-fF resolution and 10ms response time is reported. This result is an example of the enhanced performance achieved thanks to an integrated CMOS current preamplifier used as an add-on for standard bench-top electrochemical instrumentation. The chip provides a current amplification of 103 over the wide frequency range DC-2MHz and can be placed at the input of a current-to-voltage converter to reach higher gains. Thanks to its millimetric size it drastically reduces the input stray capacitance of the connection cables to the electrode, offering superior noise performance such as 0.55fA (rms) current resolution with 1Hz bandwidth demonstrated in the detection of 1.5fA current steps. The improvement in performance of state-of-art commercial potentiostats is also reported: the largest measurable impedance is increased by two orders of magnitude (up to 100GΩ with only 10mV applied and 0.125s averaging time) and the impedance noise in time tracking is reduced 35 times. This module has been developed for nano-electrochemical and bio-sensing applications but can be profitably used in all the situations in which few electrons are exchanged at the interface, either since the electrode area is nanometric or since the concentration of the redox species is extremely low.

Increasing Precision for Extended Reach 3D Manipulation

Object selection and manipulation in 3D immersive environments generally suffers from a lack of precision, primarily due to hand instability and tracking noise. Typically the lack of precision is exacerbated as the user begins to use techniques that allow distant interaction, such as Ray Casting, HOMER, and Go-Go. This problem can be addressed using velocity-based hand scaling such as PRISM, which has been applied to Ray Casting and HOMER previously. We present a study of the combination of Go-Go and PRISM. In our research, we have found that Go-Go + PRISM yields a nearly 2:1 improvement in precision over traditional Go-Go interaction when attempting to align two objects at a distance under time constraints

Environment dependent noise tracking for speech enhancement

Numerous efforts have focused on the problem of reducing the impact of noise on the performance of various speech systems such as speech recognition, speaker recognition, and speech coding. These approaches consider alternative speech features, improved speech modeling, or alternative training for acoustic speech models. This study presents an alternative viewpoint by approaching the same problem from the noise perspective. Here, a framework is developed to analyze and use the noise information available for improving performance of speech systems. The proposed framework focuses on explicitly modeling the noise and its impact on speech system performance in the context of speech enhancement. The framework is then employed for development of a novel noise tracking algorithm for achieving better speech enhancement under highly evolving noise types. The first part of this study employs a noise update rate in conjunction with a target enhancement algorithm to evaluate the need for tracking in many enhancement algorithms. It is shown that noise tracking is more beneficial in some environments than others. This is evaluated using the Log-MMSE enhancement scheme for a corpus of four noise types consisting of Babble (BAB), White Gaussian (WGN), Aircraft Cockpit (ACN), and Highway Car (CAR) using the Itakura-Saito (IS) (Gray et al. in IEEE Trans. Acoust. Speech Signal Process. 28:367---376, 1980) quality measure. A test set of 200 speech utterances from the TIMIT corpus are used for evaluations. The new Environmentally Aware Noise Tracking (EA-NT) method is shown to be superior in comparison with the contemporary noise tracking algorithms. Evaluations are performed for speech degraded using a corpus of four noise types consisting of: Babble (BAB), Machine Gun (MGN), Large Crowd (LCR), and White Gaussian (WGN). Unlike existing approaches, this study provides an effective foundation for addressing noise in speech by emphasizing noise modeling so that available resources can be used to achieve more reliable overall performance in speech systems.

LQG Servo Controller for the Current Control of $LCL$ Grid-Connected Voltage-Source Converters

This paper presents a current control scheme for a voltage-source converter connected to the grid through an <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$LCL$</tex></formula> filter. The proposed current control is based on the linear quadratic (LQ) Gaussian (LQG) servo controller technique, which combines the LQ regulator and the Kalman filter (KF). The use of the KF instead of a Luenberger estimator improves the quality of the estimation of state variables in noisy environments, increasing the noise immunity of the control loop. This paper focuses on giving some criteria and practical hints to choose both the KF and LQ design parameters to achieve null steady-state tracking error, channel decoupling, and noise immunity. Furthermore, this paper analyzes the steady-state KF approximation that allows a significant decrement in the computational complexity of the algorithm at nearly no cost in accuracy. Simulation and experimental results prove the correct operation of the proposed LQG current control and the possible advantages of using KF to estimate the state vector.

Knowledge-based Closed-loop Control of Blood Glucose Concentration in Diabetic Patients and Comparison with H∞ Control Technique

In this paper, fuzzy-based closed-loop controller is applied to obtain a robust controller for blood glucose regulation in type I diabetes mellitus patients. The control technique incorporates expert knowledge about treatment of disease by using Mamdani-type fuzzy logic controller to robustly stabilize the blood glucose concentration in normoglycemic level. Controller performance is considered in terms of its ability to reject the multiple meals, on an averaged nonlinear patient model. Robustness of the controller is tested over a group of patients with model parameter varying considerably from the average model. The controller provides the possibility of more accurate control of blood glucose level in the patient in spite of uncertainty in model parameters and measurement noise. The proposed controller has showed superiority over other classical control techniques. A comparative study is presented with well-known conventional H∞ control technique. Simulation results show the superiority of the proposed scheme in terms of reference tracking, disturbance rejection, and measurement noise in comparison with other approaches.

An embedded optical tracking system for motion-corrected magnetic resonance imaging at 7T

Prospective motion correction using data from optical tracking systems has been previously shown to reduce motion artifacts in MR imaging of the head. We evaluate a novel optical embedded tracking system. The home-built optical embedded tracking system performs image processing within a 7 T scanner bore, enabling high speed tracking. Corrected and uncorrected in vivo MR volumes are acquired interleaved using a modified 3D FLASH sequence, and their image quality is assessed and compared. The latency between motion and correction of the slice position was measured to be (19 ± 5) ms, and the tracking noise has a standard deviation no greater than 10 μm/0.005° during conventional MR scanning. Prospective motion correction improved the edge strength by 16 % on average, even though the volunteers were asked to remain motionless during the acquisitions. Using a novel method for validating the effectiveness of in vivo prospective motion correction, we have demonstrated that prospective motion correction using motion data from the embedded tracking system considerably improved image quality.

Optimized Carrier Tracking Loop Design for Real-Time High-Dynamics GNSS Receivers

Carrier phase estimation in real-time Global Navigation Satellite System (GNSS) receivers is usually performed by tracking loops due to their very low computational complexity. We show that a careful design of these loops allows them to operate properly in high-dynamics environments, that is, accelerations up to 40 g or more. Their phase and frequency discriminators and loop filter are derived considering the digital nature of the loop inputs. Based on these ideas, we propose a new loop structure named Unambiguous Frequency-Aided Phase-Locked Loop (UFA-PLL). In terms of tracking capacity and noise resistance UFA-PLL has the same advantages of frequently used coupled-loop schemes, but it is simpler to design and to implement. Moreover, it can keep phase lock in situations where other loops cannot. The loop design is completed selecting the correlation time and loop bandwidth that minimize the pull-out probability, without relying on typical rules of thumb. Optimal and efficient ways to smooth the phase estimates are also presented. Hence, high-quality phase measurements—usually exploited in offline and quasistatic applications—become practical for real-time and high-dynamics receivers. Experiments with fixed-point implementations of the proposed loops and actual radio signals are also shown.

Unbiased MMSE-Based Noise Power Estimation With Low Complexity and Low Tracking Delay

Recently, it has been proposed to estimate the noise power spectral density by means of minimum mean-square error (MMSE) optimal estimation. We show that the resulting estimator can be interpreted as a voice activity detector (VAD)-based noise power estimator, where the noise power is updated only when speech absence is signaled, compensated with a required bias compensation. We show that the bias compensation is unnecessary when we replace the VAD by a soft speech presence probability (SPP) with fixed priors. Choosing fixed priors also has the benefit of decoupling the noise power estimator from subsequent steps in a speech enhancement framework, such as the estimation of the speech power and the estimation of the clean speech. We show that the proposed speech presence probability (SPP) approach maintains the quick noise tracking performance of the bias compensated minimum mean-square error (MMSE)-based approach while exhibiting less overestimation of the spectral noise power and an even lower computational complexity.

A 12.8-Gb/s/link Tri-Modal Single-Ended Memory Interface

This paper presents a tri-modal asymmetric memory controller interface that achieves 12.8-Gbps single-ended (SE) signaling over 3" stripline FR4 traces. The controller can be configured to communicate with commercially available GDDR5 and DDR3 memories at 6.4 and 1.6 Gbps, respectively, with no package change. The interface is equipped with a compact voltage-mode driver with 1-tap pre-emphasis, in the WRITE direction, and a linear equalizer (LEQ) and 1-tap decision feedback equalizer (DFE), in the READ direction, to compensate for channel inter-symbol interference (ISI). The receiver front-end contains a supply noise tracking scheme to mitigate reference voltage (VREF) noise. A tri-VCO PLL and an efficient global clock distribution scheme support a wide range of operating frequencies at low power consumption. Finally, the interface also incorporates two overhead links per byte for data-bus encoding (DBE) experiments to mitigate simultaneous switching noise (SSN). Implemented in a 40-nm CMOS process, the × 16 tri-modal interface achieves an energy efficiency of better than 5.0 mW/Gbps per data link at 12.8 Gbps.

Robust ℋ2/ℋ∞/reference model dynamic output-feedback control synthesis

This article presents a new strategy to design robust model matching dynamic output-feedback controllers that guarantee tracking response specifications, disturbance rejection and noise attenuation. The proposed synthesis methodology, based on a multi-objective optimisation problem, can be applied to uncertain continuous or discrete-time linear time-invariant systems with polytopic uncertainty, leading to both full-order and reduced-order robust-performance dynamic controllers. The objective functions represent the ℋ∞-norm of the difference between the closed-loop transfer function matrix, from the reference signals and the plant outputs and the reference model matrix, the ℋ∞-norm of the closed-loop transfer function matrix from the disturbances and the plant outputs and the ℋ2-norm of the closed-loop transfer function matrix from the measurement noises and the control inputs. An integral control action is also introduced in order to achieve zero steady-state error. In the case of MIMO systems, the proposed strategy can be applied to decouple the closed-loop control system choosing an appropriated reference model matrix. Two examples are presented to illustrate both SISO and MIMO systems control synthesis.