Active Compensation Scheme Research Articles

Finite region stability and networked predictive control for 2-D nonlinear time-delayed systems with quantization, packet dropouts and random disturbances

In this paper, we focus on the finite region stability (FRS) and networked predictive control (NPC) problems for two-dimensional (2-D) networked control systems (NCS) with time delays, quantization errors, packet losses and random disturbances described by the Roesser model. The random packet dropouts and disturbances are modeled as Bernoulli process, and the sufficient conditions of FRS and finite region boundedness (FRB) for 2-D NCS are obtained by using the expectation to process the Lyapunov function difference, so as to better study the transient performance of the systems. According to the recursive formula, an active compensation scheme for time delays of NPC is proposed, which takes into account quantization errors, packet losses, nonlinearity and interferences. Introducing FRS and FRB into 2-D NCS and considering the above factors in NPC scheme are new attempts made in this paper. An example is used to demonstrate the validity of the conclusions in the end.

A biphasic current-mode stimulator integrated circuit with a novel residual charge compensation mechanism

A mixed-signal four-channel biphasic current-mode functional electrical stimulator chip with a novel charge compensation circuit is presented in this paper. This chip can induce programmable biphasic current ranging from 10 μA to 2.56 mA for each channel. However, a significant problem with functional electrical stimulation is charge balancing (CB) due to anodic and cathodic current mismatch for process variation. Therefore, a novel compensation module including both passive and active charge compensation schemes are adopted in this chip. The charge compensation module autonomously adjusts the supply and compensation current to achieve fast compensation and low-power consumption simultaneously. The proposed biphasic stimulator is designed and fabricated in a 0.18 μm CMOS process with a die area of 2.27 mm × 1.99 mm. The measurement results from a test bench demonstrate the proposed circuit functionalities, and the standby power consumption of this chip is 193.7 μW. Besides, animal experiments on mice for seizure suppression with deep brain stimulation were performed to verify the efficacy and safety of the developed stimulation chip.

Experimental demonstration of a local active phase compensation method for a phase encoding quantum key distribution system.

An efficient phase stabilization method is required in quantum key distribution (QKD) systems for stability in practical applications. The existing active phase compensation method has limitations in multi-node network applications, especially in network-scale applications based on measurement-device-independent QKD systems. In this study, we propose a local active phase compensation scheme that can realize phase compensation independently for each interferometer node. We performed experimental demonstrations in the BB84 phase encoding system based on a Faraday-Michelson interferometer. The average QBER rates of the system under two different forms of the reference light were found to be 1.9% and 1.6%. This scheme can also be applied to other QKD systems and has potential for application in future quantum communication networks.

Transient Performance Analysis of Reactive Power Compensators at LCC-HVDC Station Feeding Weak AC System

This paper focuses on analyzing the dynamic performance of various reactive power compensators at weak LCC-HVDC terminals. Four scenarios based on combination of active and passive reactive power compensation schemes are presented. The comparative performance analysis of various compensators in different types of AC and DC system faults are evaluated using electromagnetic transient simulation program PSCAD/EMTDC. The analysis shows that fixed capacitor has poor performance and results in reducing effective short circuit ratio of system, while STATCOM on the other hand, increases AC system strength and has significant performance in areas like immunity to commutation failure, suppression of temporary overvoltage, AC bus voltage regulation and fault recovery time.

Phase-stabilized free-space link for optical frequency transfer

Optical frequency transfer through the atmosphere is needed for diverse free-space applications, e.g. coherent communication, optical clock comparison and relativity experiments. The task requires an appropriate optical link system that provides the multimodal abilities of not only pointing, acquisition, and tracking (PAT) but also phase noise suppression in the presence of air turbulence. Here, we describe a free-space optical (FSO) link system built over a 1.4 km outdoor path to transmit optical frequencies with a fast beam tracking capability together with an active feedback compensation scheme of the atmospheric phase noise. The FSO link is able to offer a frequency transfer stability of 3.51 × 10−19 at 100 s averaging, which suffices to deliver the current state-of-the-art optical clock signals.

Active fault-tolerant predictive control of networked systems subject to actuator faults and random communication constraints

ABSTRACT The fault-tolerant control problem is investigated for a linear networked system subject to an additive actuator fault as well as random network delays and packet dropouts in the backward and forward channels. To deal with the adverse effects of the actuator fault as well as those communication constraints, an active compensation scheme combining active fault-tolerant control and predictive control is proposed based on the simultaneous estimation of the system state and actuator fault. The obtained closed-loop system is a randomly switched system with bounded round-trip time delays, and the corresponding closed-loop stability condition is derived by using a switched Lyapunov approach. Simulation results for a networked DC motor system are provided to verify the proposed method.

Analytical Study and Thermal Compensation for Capacitive MEMS Accelerometer With Anti-Spring Structure

This paper presents the analytical modeling, calculation, experimental validation and feedback compensation of a capacitive MEMS accelerometer based on geometric anti-spring structure (GAS). According to the analytical thermal drift model, asymmetrical structure and the thermal variations in the operating environment result in accelerometer nonlinearity, temperature drift of scale factor (TDSF) and displacement bias (TDB), and were solved with a force-balanced capacitive readout, electronic active compensation and calibration system, respectively. The experimental characterization of the readout circuit indicates a high sensitivity, of $5.721~V/g$ , with a closed-loop nonlinearity of $30~ppm$ for $\pm 1g$ operating range. The proposed analytical thermal drift model,confirmed by finite element analyses (COMSOL Multiphysics), predicts the thermal drifts of the bias and sensitivity. Without active compensation and calibration, the thermal drifts of the resonance frequency, bias and scale factor, for a temperature range from $- 10\,\,{^{\circ }C}$ to $90~{^{\circ }C}$ , are measured to be, respectively, of $3361~ppm$ , $900~mg$ , and $2755~ppm$ ; after the calibration and the active compensation feedback, these values are reduced to $121~ppm$ , $109~\mu g$ , $52.1~ppm$ , respectively. The Allan deviation was measured, in order to verify the effectiveness of the compensation methods, showing an initial uncompensated drift of $151~\mu g$ in the temperature range from $- 10\,\,{^{\circ }C}$ to $90~{^{\circ }C}$ , which is reduced to $41.7~\mu g$ with DC-bias compensation. Therefore, the proposed force-balanced circuit, active compensation and calibration scheme, considerably reduces the temperature-induced drift of the capacitive MEMS accelerometer based on asymmetrical GAS. [2020-0070]

Performance of Interline Unified Power Quality Conditioner IUPQC With PI, Fuzzy and ANFIS Controllers

Several artificial intelligent control schemes are highly used in several applications, in that ANFIS controller has been greatly recognized due to enhanced performance over the classical PI and Fuzzy controllers. At present the multi-feeder power distribution system is deteriorated with continuity of supply and poor power quality standards. In this multi-feeder distribution system, it is a regular consumer related issue which is acquired due to malfunctioning of massive non-linear loads. These loads create the voltage or current imperfections on distribution networks which disrupts the power quality of distribution system. An efficient and reliable active compensation scheme is used for attaining enhanced power quality features at PCC of multi-feeder distribution system with effective control functions. The Multi-Feeder Unified Power Quality Compensator (MF-UPQC) is optimal choice for attaining enhanced power quality features and it is a combined shunt or series compensator driven by common DC-link. This paper recommends the Adaptive Neuro-Fuzzy Intelligent Controller (ANFIS) based prediction technique for generation of optimal switching states to enhance performance of proposed MF-UPQC to compensate all voltage-current PQ imperfections. The performance of proposed MF-UPQC is verified by classical PI, Fuzzy and proposed ANFIS control functions by using MATLAB/SIMULINK tool and results are conferred with proper comparisons.

Toward High Accuracy Positioning in 5G via Passive Synchronization of Base Stations Using Thermally-Insensitive Optical Fibers

Positioning accuracy in 5G networks (achieved via techniques based on observed time difference of arrival (OTDoA)) is limited by the synchronization error between the cellular base stations. Here, we demonstrate that these base stations can be synchronized entirely passively through the use of emerging forms of hollow core fiber (HCF) as the data transmission medium in the 5G front-haul network. This is possible due to the excellent thermal stability of HCF which allows the synchronization error among cellular base stations to be reduced significantly as compared to systems based on standard single mode fibers. Reducing this synchronization error is necessary to meet the strict timing requirements envisaged for 5G networks. We analyze the polarization mode dispersion, chromatic dispersion, and thermal stability of the HCF and give suggestions on how to use the HCF to balance overall radio over fiber (RoF) link performance in 5G front-haul networks. In a proof of concept experiment we show that HCF links enable the positioning error (calculated with the OTDoA method) to be reduced down to the centimeter level even when subject to tens of degrees Celsius temperature variations. This represents a 20-fold improvement over standard single mode fiber systems which would require active compensation schemes to achieve similar levels of time synchronization accuracy.

Stable radio frequency dissemination in a multi-access link based on passive phase fluctuation cancellation

We propose and experimentally demonstrate a novel scheme of stable radio frequency (RF) dissemination in a multi-access radio-over-fiber (ROF) link. Unlike the active compensation scheme based on a phase-locking loop, the proposed scheme provides fast responses and infinite dynamic ranges with a passive phase fluctuation cancellation (PPFC) approach. In our experiment, a 2.5-GHz signal is steadily distributed to a remote end through an arbitrary user site in a 25-km optical fiber link. The stability of the recovered signals at the user site and the remote end are evaluated. By using the phase correction scheme, the peak–peak phase excursion is reduced from 140 to 4 ps at the user site and 160 to 4 ps at the remote end, respectively. The achieved relative residual frequency instabilities are 1.4117×10−16∕104s and 1.6503×10−16∕104s at the user site and the remote end, respectively.

Loss-Free Negative-Index Metamaterials Using Forward Light Scattering in Dielectric Meta-Atoms

Negative-index metamaterials are significantly limited by their inherent losses. We demonstrate that a negative index without dissipative and reflective losses can be achieved in subwavelength dielectric cuboid arrays. We can avoid reflection by making dielectric cuboids exhibit the resonant forward scattering of light, while dissipative loss is inherently absent in dielectric materials. A joint study combining theoretical and experimental research demonstrates that loss-free negative-index metamaterials can be realized. They fulfill the criteria of negative refraction based on causality, while conventional active loss compensation schemes lead to the disappearance of negative refraction by causality.

Hybrid fiber links for accurate optical frequency comparison

We present the experimental demonstration of a local two-way optical frequency comparison over a 43-km-long urban fiber network without any requirement for measurement synchronization. We combined the local two-way scheme with a regular active noise compensation scheme that was implemented on another parallel fiber leading to a highly reliable and robust frequency transfer. This hybrid scheme allowed us to investigate the major limiting factors of the local two-way comparison. We analyzed the contributions of the interferometers at both local and remote locations to the phase noise of the local two-way signal. Using the ability of this setup to be injected by either a single laser or two independent lasers, we measured the contributions of the demodulated laser instabilities to the long-term instability. We show that a fractional frequency instability level of 10−20 at 10,000 s can be obtained using this simple setup after propagation over a distance of 43 km in an urban area.

A 5-/20-MHz BW Reconfigurable Quadrature Bandpass CT <inline-formula> <tex-math notation="LaTeX">$\Delta \Sigma $ </tex-math></inline-formula> ADC With AntiPole-Splitting Opamp and Digital <inline-formula> <tex-math notation="LaTeX">$I$ </tex-math></inline-formula>/<inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> Calibration

A dual-mode second-order reconfigurable quadrature bandpass continuous-time delta–sigma modulator is presented for a low-IF global navigation satellite system receiver to simplify the entire architecture. The proposed modulator is capable of supporting both narrowband of 5-MHz bandwidth (BW) and wideband of 20-MHz BW. An amplifier topology with active feed-forward and antipole-splitting compensation schemes is proposed. The flexible amplifiers in active- RC integrators and preamplifiers in comparators are implemented with power scaling technique to effectively adjust the power consumption for both BWs. A 1-bit digitally switched current digital-to-analog converter structure with gate-leakage compensation and low-latency dynamic element matching is proposed to cover large current variations and mitigate the gate-leakage issue. Digital $I$ / $Q$ self-calibration algorithm is realized to improve the image-rejection ratio (IRR). Implemented in 65-nm CMOS, the $\Delta \Sigma $ modulator achieves 67.8-/61.4-dB dynamic range, 65.9-/53.7-dB signal-to-noise-plus-distortion ratio, and >60-dB IRR after calibration across 5-/20-MHz BW with center frequencies of 4/12 MHz, respectively. Powered by a 1.2 V supply, the modulator only consumes 4.2/8.1 mW, resulting in measured figure-of-merits of 0.26/0.51 pJ/conversion step.

A geometric-sensitivity-difference based algorithm improves object depth-localization for diffuse optical tomography in a circular-array outward-imaging geometry

To improve object depth-localization for diffuse optical tomography (DOT) in a circular-array outward-imaging geometry that is subjected to strong sensitivity variation with respect to imaging depth. The authors introduce an alternative DOT image reconstruction approach that optimizes the data-model fit based on the paired measurements corresponding to two pairs of source-detector that share either the source or the detector, in comparison to the conventional method that optimizes the data-model fit based on the unpaired measurements corresponding to individual pairs of source-detector. This alternative approach, namely, geometric-sensitivity-difference (GSD) method, effectively reduces the variation of the reconstruction sensitivity with respect to imaging depth. The DOT image reconstruction based on GSD-scheme applied to same-source source-detector pairs is demonstrated using simulated and experimental continuous-wave measurements in a circular-array outward-imaging geometry, of which the native sensitivity varies strongly with respect to the depth. The outcomes of GSD-based image reconstruction are compared to those of two other methods: one is the conventional baseline method that utilizes the native sensitivity but does not involve depth-compensating scheme; and the other is a reference-compensation approach that employs active and depth-adapted compensation scheme to counteract the dependence of the reconstruction sensitivity with respect to imaging depth. The GSD method generally outperforms the other two methods in localizing the depth of single object, resolving two objects that are azimuthally separated, and estimating the optical property of single object or azimuthally separated dual objects. The GSD method, however, demands more computations due to an increase of the element size of the resulted sensitivity matrix and more matrix multiplications. The GSD method improves the depth localization in the circular-array outward-imaging geometry, by taking advantage of the paired measurements of two source-sharing source-detector-pairs to passively and effectively homogenize the sensitivity of the reconstruction with respect to imaging depth.

A fully on-chip area-efficient CMOS low-dropout regulator with fast load regulation

Fully integrated voltage regulators with fast transient response and small area overhead are in high demand for on-chip power management in modern SoCs. A fully on-chip low-dropout regulator (LDO) comprised of multiple feedback loops to tackle fast load transients is proposed, designed and simulated in 90 nm CMOS technology. The LDO also adopts an active frequency compensation scheme that only needs a small amount of compensation capacitors to ensure stability. Simulation results show that, by the synergy of those loops, the LDO improves load regulation accuracy to 3 μV/mA with a 1.2 V input and 1 V output. For a 100 mA load current step with the rise/fall time of 100 ps, the LDO achieves maximum output voltage drop and overshoot of less than 95 mV when loaded by a 600 pF decoupling capacitor and consumes an average bias current of 408 μA. The LDO also features a magnitude notch in both its PSRR and output impedance that provides better suppression upon the spectral components of the supply ripple and the load variation around the notch frequency. Monte Carlo simulations are performed to show that the LDO is robust to process and temperature variations as well as device mismatches. The total area of the LDO excluding the decoupling capacitor is about 0.005 mm2. Performance comparisons with existing solutions indicate significant improvements the proposed LDO achieves.

1316 アクティブフィルタ補償方式を用いた燃料電池と電気二重層キャパシタのハイブリッド制御システム(GS-8 動力エネルギーシステム)

1316 アクティブフィルタ補償方式を用いた燃料電池と電気二重層キャパシタのハイブリッド制御システム(GS-8 動力エネルギーシステム)

用于BB84相位编码量子密钥分发系统的不间断式主动相位补偿方案

用于BB84相位编码量子密钥分发系统的不间断式主动相位补偿方案

Actively Compensating for Data Packet Disorder in Networked Control Systems

Data packet disorder often occurs in networked control systems (NCSs), which, however, has not been taken into account in most literature to date. In this brief, the cause and effect of data packet disorder are analyzed, and an active compensation scheme is proposed to compensate for it. The proposed scheme is flexible to admit all the existing control approaches to be used and also derives a novel closed-loop system model of NCSs, which enables more reasonable and effective theoretical analysis of NCSs. The effectiveness of the proposed active compensation scheme is illustrated by a numerical example.

An effective active phase compensation method for quantum key distribution system

Quantum key distribution (QKD) system must be robust enough in practical communication. The system performance is notably affected by phase drift. For the fiber-based phase-encoded quantum key distribution system, the Faraday-Michelson QKD scheme can auto-compensate the birefringence of fiber, but phase drift caused by environment variations is still a serious problem in practical operation. In this paper, the major schemes to compensate for the phase drift are analyzed in detail and an “five-phase”effective active phase compensation method is proposed. The comparison with other two major active phase compensation schemes also given. The result shows that this method uses less time to acquire the parameter of phase drift with the same precision and it can be used in phase-encoded QKD systems without introducing additional devices.

Prototype Control System for Compensation of Superconducting Cavities Detuning Using Piezoelectric Actuators

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Pulsed operation of high gradient superconducting radio frequency (SCRF) cavities results in dynamic Lorentz force detuning (LFD) approaching or exceeding the bandwidth of the cavity of order of a few hundreds of Hz. The resulting modulation of the resonance frequency of the cavity is leading to a perturbation of the amplitude and phase of the accelerating field, which can be controlled only at the expense of RF power. Presently, at various labs, a piezoelectric fast tuner based on an active compensation scheme for the resonance frequency control of the cavity is under study. The tests already performed in the Free Electron Laser in Hamburg (FLASH), proved the possibility of Lorentz force detuning compensation by the means of the piezo element excited with the single period of sine wave prior to the RF pulse. The X-Ray Free Electron Laser (X-FEL) accelerator, which is now under development in Deutsche Elektronen—Synchrotron (DESY), will consists of around 800 cavities with a fast tuner fixture including the actuator/sensor configuration. Therefore, it is necessary to design a distributed control system which would be able to supervise around 25 RF stations, each one comprised of 32 cavities. The Advanced Telecomunications Computing Architecture (ATCA) was chosen to design, develop, and build a Low Level Radio Frequency (LLRF) controller for X-FEL. The prototype control system for Lorentz force detuning compensation was designed and developed. The control applications applied in the system were fitted to the main framework of interfaces and communication protocols proposed for the ATCA-based LLRF control system. The paper presents the general view of a designed control system and shows the first experimental results from the tests carried out in FLASH facility. Moreover, the possibilities for integration of the piezo control system to the ATCA standards are discussed. </para>