Adaptive Tracking Scheme Research Articles

High-throughput imaging surface plasmon resonance biosensing based on an adaptive spectral-dip tracking scheme.

Imaging-based spectral surface plasmon resonance (λSPR) biosensing is predominantly limited by data throughput because of the multiplied data capacity emerging from 2-dimensional sensor array sites and the many data points required to produce an accurate measurement of the absorption dip. Here we present an adaptive feedback approach to address the data throughput issue in λSPR biosensing. A feedback loop constantly tracks the dip location while target-molecule binding occurs at the sensor surface. An adaptive window is then imposed to reduce the number of data points that each pixel has to capture without compromising measurement accuracy. Rapid wavelength scanning is performed with a liquid crystal tunable filter (LCTF). With the use of a feedback loop, our demonstration system can produce a dip measurement within 700ms, thus confirming that the reported λSPR approach is most suitable for real-time micro-array label-free biosensing applications.

Adaptive tracking control for uncertain switched nonlinear systems in nonstrict-feedback form

This paper investigates an adaptive tracking problem of a class of uncertain switched nonlinear systems in nonstrict-feedback form with arbitrary switchings. Switched nonstrict-feedback nonlinearities, switched control coefficient functions, and external disturbances are considered and assumed to be unknown. Compared with existing literature, a main contribution of this paper is to design a common adaptive control scheme in the presence of unknown switched nonstrict-feedback nonlinearities related to all state variables and arbitrary switchings. Based on the common Lyapunov function method and the dynamic surface design technique, a common adaptive tracking scheme is constructed and the finite-time stability of the controlled closed-loop system is analyzed. It is shown that the tracking errors converge to an adjustable neighborhood of the origin in finite time. Finally, simulation results are provided to show the effectiveness of the proposed methodology.

A Novel Adaptive Real-time Tracking Scheme for Underwater Networks

Location information of mobile submersibles is critical to underwater networks. A considerable amount of researches have been carried out on non-real-time tracking to suffice many scenarios, while the lack of real-time tracking motivates more efforts to be addressed in Real-time underwater applications. In this paper a novel adaptive Real-time tracking scheme is presented, which can adaptively adjust the length of factor graph and then construct the resulting partial factor graph to track the positions of mobile submersibles. Since the proposed scheme tailors the basic factor graph into a partial factor graph with much shorter length in time, it makes the Real-time tracking feasible. Meanwhile, adaptively constructing the appropriate partial factor graph according to accuracy requirement of localization, can obtain high accuracy for localization and tracking. Simulation results using real sea-trail data show that our proposed scheme can adaptively trade off Real-time requirement and localization accuracy, achieving 12% to 61% improvement for tracking performance in the corresponding scenarios, when comparing with the classic TDoA (Time Difference of Arrival) localization method.

An Adaptive Phase Tracking Scheme of OFDM Wireless Communication System

This paper proposes a new phase tracking algorithm for the 802.11a system. Since this system illuminates the basic structure of 802.11a system, and introduces the OFDM frame generation principle based the transmitter, phase error estimation and channel estimation. On the basis of this, this paper presents a phase tracking scheme based on adaptive Kalman filter, and then simulates the process based on 802.11a system. The result indicates that the BER has been improved because of this adaptive phase tracking scheme.

Simple Adaptive Asymptotic Tracking Scheme for Parametric Strict-Feedback Nonlinear Systems with Additive Disturbance

We consider the same class of systems in a previous paper, that is, a class of parametric strict-feedback nonlinear systems with additive disturbance. By using the backstepping technique, adaptive control algorithm is developed. Unlike the existing control schemes for systems with additive disturbance, no knowledge is assumed on two times continuous differentiability of the disturbance. Also, the developed backstepping controller does not require the uncertain parameters to be restricted within a known interval. Furthermore, overestimation of the system parameters is removed by employing the tuning functions method. It is shown that the proposed controller guarantees not only the stability in the sense of Lyapunov definition, but also the asymptotic tracking.

태양광 시스템을 위한 가변 조정계수 기반의 적응형 MPPT 제어 기법

An adaptive maximum power point tracking (MPPT) scheme employing a variable scaling factor is presented. A MPPT control loop was constructed analytically and the magnitude variation in the MPPT loop gain according to the operating point of the PV array was identified due to the nonlinear characteristics of the PV array output. To make the crossover frequency of the MPPT loop gain consistent, the variable scaling factor was determined using an approximate curve-fitted polynomial equation about linear expression of the error. Therefore, a desirable dynamic response and the stability of the MPPT scheme were maintained across the entire MPPT voltage range. The simulation and experimental results obtained from a 3 KW rated prototype demonstrated the effectiveness of the proposed MPPT scheme.

Backstepping control for periodically time-varying systems using high-order neural network and Fourier series expansion

An adaptive backstepping tracking scheme is developed for a class of strict-feedback systems with unknown periodically time-varying parameters and unknown control gain functions. High-order neural network (HONN) and Fourier series expansion (FSE) are combined into a new function approximator to model each uncertain term in the system. The dynamic surface control (DSC) approach is used to solve the problem of ‘explosion of complexity’ in the backstepping design procedure. Nussbaum gain function (NGF) is employed to deal with the unknown control gain functions. The uniform boundedness of all closed-loop signals is guaranteed. The tracking error is proved to converge to a small residual set around the origin. Two simulation examples are provided to demonstrate the effectiveness of the control scheme designed in this paper.

Decentralized Backstepping Adaptive Output Tracking of Interconnected Nonlinear Systems

In this paper, we propose a new totally decentralized adaptive output tracking scheme for a class of nonlinear interconnected systems by using a backstepping approach. In the design, a smooth function is introduced to compensate for the effects of interactions from other subsystems. It is shown that the designed local adaptive controllers can ensure all the signals in the closed loop system are bounded. A root mean square type of bound is obtained for the tracking error as a function of design parameters. This implies that the transient tracking error performance can be adjusted by choosing suitable design parameters.

Robust adaptive tracking control of uncertain discrete time systems

In this paper, the problem of robust adaptive tracking for uncertain discrete-time systems is considered from the slowly varying systems point of view. The class of uncertain discrete-time systems considered is subjected to both 𝓁∞ to 𝓁∞ bounded unstructured uncertainty and external additive bounded disturbances. A priori knowledge of the dynamic model of the reference signal to be tracked is not completely known. For such problem, an indirect adaptive tracking controller is obtained by frozen-time controllers that at each time optimally robustly stabilize the estimated models of the plant and minimize the worst-case steady-state absolute value of the tracking error of the estimated model over the model uncertainty. Based on 𝓁∞ to 𝓁∞ stability and performance of slowly varying system found in the literature, the proposed adaptive tracking scheme is shown to have good robust stability. Moreover, a computable upper bound on the size of the unstructured uncertainty permitted by the adaptive system and a computable tight upper bound on asymptotic robust steady-state tracking performance are provided. Copyright © 2005 John Wiley & Sons, Ltd.

Direct pole placement adaptive tracking of non-minimum phase systems

In this paper, we propose a direct pole placement adaptive tracking scheme for non-minimum-phase, open-loop stable, linear plants with time delays. This controller utilizes the internal model principle to eliminate steady-state tracking error for signals with known distinct frequencies. The controller order depends only on the number of frequencies in the reference input, but not on the order of the plant. It is shown that with sufficiently small loop gain, the controller can guarantee stable closed loop, and asymptotic tracking.

A Comparison of Adaptive Location Tracking Schemes in Personal Communications Networks

Various tracking strategies for the location of a mobile user in a cell system have been introduced in literature. Up to now they have been evaluated using simple mobility models that do not take into account the various directions in which users often move. In this paper we present a comprehensive study of distance-based, movement-based and multilayer strategies, from which it emerges that the effectiveness of these techniques depends not only on the call-to-mobility rate, a parameter typically referred to in literature, but also on the directional characteristics of the user mobility model.

Performance analysis for an adaptive filter code-tracking technique in direct-sequence spread-spectrum systems

This paper investigates tracking of direct-sequence spread-spectrum (DS/SS) signals based on an adaptive filtering technique. It is shown that a previously proposed hardware for code acquisition is also capable of code-tracking, and, hence, by performing both acquisition and tracking with the same circuitry, a significant simplification in the overall DS/SS receiver structure is gained. Analytical results show that the proposed scheme has a good tracking performance, as measured by the hold-in time and the false alarm penalty time, and is less sensitive to variations in the signal-to-noise ratio (SNR) compared to conventional delay-locked loops (DLLs). Moreover, simulation results show that the proposed adaptive filter tracking scheme has a smaller residual tracking error than that produced by a conventional maximum-likelihood estimator (MLE).

Adaptive Regulation of Manipulators Using Only Position Measurements

This article considers the motion-control problem for uncertain robot manipulators in the case where only joint-position mea surements are available, and proposes an adaptive controller as a solution to this problem. The proposed control strategy is general and computationally effrcient, requires very little infor mation regarding the manipulator model or the payload, and ensures that the position-regulation error possesses desirable convergence properties: semiglobal asymptotic convergence if no external disturbances are present, and semiglobal con vergence to an arbitrarily small neighborhood of zero in the presence of bounded disturbances. It is shown that the adaptive controller can be modified to provide accurate trajectory track ing control through the introduction of feedforrvard elements in the control law. The adaptive regulation and tracking schemes have been implemented in laboratory experiments with an IMI Zebra Zero manipulator. These experiments demonstrate that accurate and robust motion control can be achieved by using the proposed approach.

Gadolinium-enhanced high-resolution MR angiography with adaptive vessel tracking: preliminary results in the intracranial circulation.

To overcome problems associated with poor contrast between vessels and background tissue in time-of-flight magnetic resonance angiography, the role of intravenous gadopentetate dimeglumine in conjunction with a postprocessing adaptive vessel tracking scheme was studied. Vessel tracking makes it possible to discriminate arteries from veins, to prevent problems associated with other bright tissues on maximum-intensity projections, and to increase the signal-to-noise ratio. Short, asymmetric, velocity-compensated field echoes were used in conjunction with high-resolution imaging techniques to spatially discriminate between adjacent vessels and stationary background tissue. Gadopentetate dimeglumine was shown to be useful for visualization of small vessels, aneurysms, and regions of slow flow, when used with this post-processing scheme.

Systematic design of adaptive controllers for feedback linearizable systems

A systematic procedure for the design of adaptive regulation and tracking schemes for a class of feedback linearizable nonlinear systems is developed. The coordinate-free geometric conditions, which characterize this class of systems, do not constrain the growth of the nonlinearities. Instead, they require that the nonlinear system be transformable into the so-called parametric-pure feedback form. When this form is strict, the proposed scheme guarantees global regulation and tracking properties, and substantially enlarges the class of nonlinear systems with unknown parameters for which global stabilization can be achieved. The main results use simple analytical tools, familiar to most control engineers. >