Simple Tuning Scheme Research Articles

An Output-Feedback Controller for a Single Machine Infinite Bus Power System

The stability of a Single Machine Infinite Bus (SMIB) is enhanced through a nonlinear (NL) observer-based controller driven by load angle measurement with a constructive framework: (i) based on input-output feedback linearising control strategy, (ii) with assignable pole closed-loop (CL) linear dynamics, (iii) with a linear geometric (G) (Luenberger with integral action to eliminate the output estimation mismatch) observer, and (iv) rejection of model parameter errors and unmeasured input disturbances coupled with a simple tuning scheme. As a result, the proposed observer-based controller has a more systematic design and priority assurance of robust functioning with a suitable trade-off between transient response, robustness concerning model exogenous disturbances, control effort, and a relatively simple conventional tuning scheme in comparison with the traditional industrial controllers as the Power System Stabilizer and Automatic Voltage Regulator (PSS/AVR). The proposed controller is tested with a representative example through numerical simulation and compared with the traditional control scheme PSS/AVR.

On adaptive attitude tracking control of spacecraft: A reinforcement learning based gain tuning way with guaranteed performance

This paper investigates the attitude tracking control problem of a rigid spacecraft subject to inertial uncertainties, uncertain space perturbations and actuator saturation. Firstly, a static inertial-matrix free attitude controller is designed to guarantee the appointed-time convergence and tracking accuracy indicators of the spacecraft. Then, two-layer critic-action NNs are used to tune and optimize the control gains adaptively to improve the robustness and tracking performance of the devised static attitude controller via exploring the reinforcement learning (RL) technique. Compared with the existing attitude control methods, the prominent advantage of our work is that the devised controller is inertial-matrix free with a simple RL-based adaptive parameter tuning scheme, which reduces the conservativeness of the traditional attitude controllers with fixed control gains and is also easy to be achieved. Finally, two groups of illustrative examples are organized to validate the effectiveness of the proposed attitude control method.

Wideband tunable REC-DFB laser array using thin-film heaters on the submount

A wideband wavelength-tunable 4×5 distributed feedback (DFB) semiconductor laser array based on the reconstruction-equivalent-chirp (REC) technique using a simple tuning scheme is demonstrated. It consists of 20 DFB lasers with 4×5 matrix interleaving distributions, two-level cascaded Y-branch optical combiners, and one active semiconductor optical amplifier (SOA), all in-series integrated on one chip. Unlike the traditional thermal-electric cooler (TEC)-based wavelength-tuning scheme, the tunable 4×5 REC-DFB laser array achieves a faster and broader continuous wavelength-tuning range using TaN thin-film heaters integrated on the AlN submount. By changing the injection current of the TaN resistor from 0 to 190 mA, the proposed tunable laser achieves a wavelength-tuning range of ∼2.5 nm per channel and a total tuning of over 50 nm. This study opens up new avenues for realizing cost-effective and wide-tuning-range semiconductor lasers.

Enhanced Tuning Performance of In-Series REC-DFB Laser Array

In this study, a tunable in-series multi-wavelength distributed feedback laser array (DFB-MLA) based on reconstruction-equivalent-chirp (REC) technique with simple wavelength tuning scheme is presented and experimentally demonstrated. Unlike traditional DFB laser tuned by thermal-electric cooler (TEC), the proposed laser tuned by injection current can realize faster wavelength-tuning and reduce TEC power consumption. By comparing the thermal influence of different structures of heatsink blocks, several optimized block structures are selected for appropriate thermal conductivity and controllable heat dissipation, resulting in a broad and continuous wavelength tuning range. The proposed in-series DFB-MLA on optimized heatsink achieves better tuning performance with a wavelength tuning range of ~2.4 nm per channel from 40 to 120 mA and stable output power of over 20 mW compared to the laser mounted on the standard heatsink block with the tuning range of 1.4 nm per channel. Furthermore, the tunable laser keeps good single-mode stability, with a side mode suppressing ratio (SMSR) of over 40 dB. Thus, this study provides a new perspective for designing a low-cost continuous tunable semiconductor laser with a simple tuning mechanism in the future.

Decentralized robust state estimation of multimachine power systems

The problem of online estimating the states of nonlinear (NL) Multimachine Power Systems (MPSs) is addressed within a constructive framework that combines notions and tools from electrical engineering and nonlinear estimation theory. First, the standard NL centralized model is realized as a set of linear decentralized robustly observable models, with augmented states that capture nonlinearity, parameter error, and intermachine state interaction. Then, based on the observability property of the decentralized model, a robustly convergent linear Geometric (Luenberger-like with integral action) estimator with simple tuning is constructed. With respect to previous MPS estimation techniques, the novelties are: (i) from a theoretical perspective, the comprehensiveness of the methodology, with model design, solvability in terms of observability, and robust functioning criteria coupled with a simple tuning scheme, and (ii) from an industrial applicability viewpoint, an online computation load considerably smaller than the one of the NL Extended Kalman Filter (EKF), and a tuning scheme appreciably simpler than the one of the NL sliding mode perturbation observer (SMPO). The proposed design methodology is illustrated through numerical simulation with a representative case example.

Improved Range Tunability of DFB Lasers Based on REC Technique Under Injection Current

Multi-wavelength distributed feedback laser array (DFB-MLA) based tunable semiconductor lasers have been widely used owing to the high mode stability and simple wavelength tuning scheme. In this paper, we proposed and experimentally demonstrated a matrix-grating tunable DFB laser array. And the reconstruction-equivalent-chirp (REC) technique is utilized to simplify grating fabrication and realize precise control of the grating phase. Traditionally, the laser is tuned by thermal-electric cooler (TEC), with large power consumption, slow wavelength tuning capability, and added device. To improve the wavelength tuning speed of laser, we varied laser's injection current instead of adjusting TEC's temperature. In addition, we analyzed the thermal influence of submount on the laser and then chose the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as the submount material for its low thermal conductivity and poor heat dissipation, resulting in wide wavelength tuning range via injection current. The DFB-MLA chip achieves a better tunable effect as the lasers can be tuned at 3.5-3.7 nm per channel from 50 to 120 mA with stable output power of over 3 mw as contrasted with the laser on the AlN submount being tuned at 1.4-1.5 nm per channel. And the chip has a side-mode suppressing ratio (SMSR) of over 35 dB and strong stability of wavelength in the repeated experiments. The proposed method may give a new way to realize the wide tuning range tunable DFB laser with a simple wavelength tuning mechanism in the future, especially for the applications of uncooled low-cost tunable lasers.

High Single-Mode Stability Tunable In-Series Laser Array With High Wavelength-spacing Uniformity

Multi-wavelength distributed feedback laser array based tunable semiconductor lasers have been widely used owing to their high mode stability and simple tuning scheme. Comparing with the in-parallel laser array, the in-series one can avoid a large power loss caused by the optical combiner. However, the single-mode stability of an in-series laser array is vulnerable to the reflections of other lasers. Here we experimentally demonstrated a tunable in-series laser array with high single-mode stability and high uniformity of wavelength spacing. To reduce the impact of such reflections, the Bragg gratings in different lasers were designed in phase, and the grating phase error was reduced by utilizing the reconstruction-equivalent-chirp technique. Besides, a three-section laser structure was applied in each laser to increase the priority of the dominant lasing mode. Four lasers with small wavelength-spacings of 2.5 nm were integrated in the in-series laser array. According to the measurement results of 40 in-series laser arrays (160 lasers), wavelength deviations of 90.6% lasers were within ±0.2 nm, average wavelength spacings of 97.5% of the measured laser arrays were deviated from the design within ±0.2 nm, and SMSRs of 96.3% lasers were above 45 dB. The output power was above 25 mW and the relative intensity noise was below -130 dB/Hz. Like the in-parallel laser array, the proposed laser array can be applied in either continuous wavelength tuning or fast channel switching. For the continuous wavelength tuning applications, the 10-nm tuning range was obtained with a temperature tuning range of less than 20 °C. For the fast channel switching applications, four channels with 2.5-nm spacing are available, and the switching time between two channels was less than 300 ns.

I/Q mismatch calibration of a transmitter using local quadrature oscillator

In this paper a calibration technique for I/Q mismatch of a transmitter is introduced. The calibration technique is based on the fact that all mismatches in I/Q paths can be modeled as the mismatch of the local oscillator quadrature outputs. Based on this fact, a simple tuning scheme for quadrature output of the oscillator is used to calibrate the mismatch of the I/Q transmitter. In addition to quadrature oscillator, gain mismatch of the I/Q paths and LO feedthorugh and leakage is calibrated by using a tunable linear Gm cell in the base band part. In order to demonstrate the proposed technique, a transmitter with 1.8GHz carrier frequency is designed with auxiliary blocks to extract and cancel out the I/Q mismatches. The simulation results in 0.18µm RFCMOS process show that the proposed technique can reduce amplitude of the image signal resulting from mismatches in I/Q paths about 18.5dB in the transmitter output.

Frustration tuning and perfect phase synchronization in the Kuramoto-Sakaguchi model.

We present an analysis of conditions under which the dynamics of a frustrated Kuramoto-or Kuramoto-Sakaguchi-model on sparse networks can be tuned to enhance synchronization. Using numerical optimization techniques, linear stability, and dimensional reduction analysis, a simple tuning scheme for setting node-specific frustration parameters as functions of native frequencies and degrees is developed. Finite-size scaling analysis reveals that even partial application of the tuning rule can significantly reduce the critical coupling for the onset of synchronization. In the second part of the paper, a codynamics is proposed, which allows a dynamic tuning of frustration parameters simultaneously with the ordinary Kuramoto dynamics. We find that such codynamics enhance synchronization when operating on slow time scales, and impede synchronization when operating on fast time scales relative to the Kuramoto dynamics.

A 1.3–2.08 GHz Filtering Power Divider With Bandwidth Control and High In-Band Isolation

This letter proposes a varactor-based filtering power divider that allows for reconfigurable operating frequency and bandwidth with high in-band isolation. A simple but effective tuning scheme was used to attain good impedance matching and isolation for all tunable states. Experimental results show that, for input return loss $>$ 16.6 dB, the center frequency and 1 dB constant absolute bandwidth can be tuned from 1.3 to 2.08 GHz and from 70 to 130 MHz, respectively. Moreover, this work demonstrates $>$ 26 dB output isolation, $ 0.23 dB magnitude imbalance, and $ phase imbalance. Measured and simulated results are in good agreement.

Electroabsorption-modulated widely tunable DBR laser transmitter for WDM-PONs.

We present an InP based distributed Bragg reflector (DBR) laser transmitter which has a wide wavelength tuning range and a high chip output power for wavelength division multiplexing passive optical network (WDM-PON) applications. By butt-jointing InGaAsP with 1.45 µm emission wavelength as the material of the grating section, the laser wavelength can be tuned for over 13 nm by the DBR current. Accompanied by varying the chip temperature, the tuning range can be further enlarged to 16 nm. With the help of the integrated semiconductor optical amplifier (SOA), the largest chip output power is over 30 mW. The electroabsorption modulator (EAM) is integrated into the device by the selective-area growth (SAG) technique. The 3 dB small signal modulation bandwidth of the EAM is over 13 GHz. The device has both a simple tuning scheme and a simple fabrication procedure, making it suitable for low cost massive production which is desirable for WDM-PON uses.

Narrow bandwidth and polarization independent design of hollow waveguide in-plane mirror with ultrawide tuning-range

A design of an integrated widely tunable in-plane micro-optical mirror based on a hollow waveguide (HWG) consisting of a high index contrast grating (HCG) and a dielectric multilayer distributed Bragg reflector (DBR) is proposed. The in-plane mirror is formed in a variable air-core HWG by loading a SiO(2) Bragg grating on the multilayer (DBR) mirror. Ultrawide tuning of 161 and 150 nm in Bragg wavelengths of TE and TM mode, respectively are reported in simulation with a simple tuning scheme and a single tuning parameter of variable air core. The presence of HCG in the proposed design causes a reduction from 88 nm (for DBR-DBR) to 48 nm (for HCG-DBR) in the 3 dB reflection-bandwidth of the proposed in-plane mirror. Also, a four-time reduction in the difference in the reflectivity of the Bragg wavelengths of TE and TM modes is reported because of the introduction of HCG into the hollow waveguide. The reflections of orthogonal polarizations and hence the polarization characteristics of the in-plane mirror are controlled by the combined effect of HCG and DBR.

On the Mode-Matched Control of MEMS Vibratory Gyroscope via Phase-Domain Analysis and Design

This paper investigates a novel method for the mode-matched control of a microelectromechanical systems (MEMS) vibratory gyroscope through a phase-domain analysis. Compared with the previous works, the proposed method presents a simple and robust automatic mode tuning scheme for sensitivity enhancement. In designing the mode-matched control loop, the resonant characteristics of the driving axis are used as the reference mode. Then, the phase difference between sense and drive modes at the resonant frequency of drive mode is used to generate a control signal for phase error regulation. For the control loop design, a linear phase-locked loop is adapted. Through the simulation using practical MEMS gyroscope parameters, the mode-matching performance and robustness of the designed control loop is demonstrated. It is also shown that coupling effect yields no degradation of output sensitivity. Finally, the experimental results obtained by implementing the electronics of mode-matched control verify the feasibility of the proposed method.

Breadth-First Signal Decoder: A Novel Maximum-Likelihood Scheme for Multi-Input–Multi-Output Systems

A number of decoding schemes have recently been proposed to perform maximum-likelihood (ML) detection for multi-input-multi-output (MIMO) systems. In this paper, employing a ldquobreadth-firstrdquo search algorithm for closet points in a lattice, we propose a novel ML decoding scheme called the breadth-first signal decoder (BSIDE). Through analysis and computer simulations, it is shown that the BSIDE has the same bit-error-rate performance as the conventional ML decoders while allowing significantly lower computational complexity. In addition, we introduce a simple tuning scheme that allows the BSIDE to have a performance-complexity tradeoff capability as necessary.

Ultra-cold atoms in an optical cavity: two-mode laser locking to the cavity avoiding radiation pressure

The combination of ultra-cold atomic clouds with the light fields of optical cavities provides a powerful model system for the development of new types of laser cooling and for studying cooperative phenomena. These experiments critically depend on the precise tuning of an incident pump laser with respect to a cavity resonance. Here, we present a simple and reliable experimental tuning scheme based on a two-mode laser spectrometer. The scheme uses a first laser for probing higher-order transversal modes of the cavity having an intensity minimum near the cavity’s optical axis, where the atoms are confined by a magnetic trap. In this way the cavity resonance is observed without exposing the atoms to unwanted radiation pressure. A second laser, which is phase locked to the first and tuned close to a fundamental cavity mode, drives the coherent atom-field dynamics.

Online Identification of Stator Transient Inductance in Rotor-Flux-Oriented Induction Motor Drive

In a rotor-flux-oriented induction motor drive, stator transient inductance is varied with the change of operating conditions. If the stator transient inductance is not tuned, the field orientation cannot be obtained. As a result, q-axis rotor flux does not become zero, and the performance is deteriorated. This paper shows the problems caused by the detuning of stator transient inductance and proposes a simple online tuning scheme of stator transient inductance for an indirect rotor flux-oriented induction motor drive. Stator transient inductance is estimated only by stator voltage and stator current. The proposed method is verified by simulation and experimental results.

Widely Tunable Twin-Guide Laser Diodes With Sampled Gratings: Design and Performance

The widely tunable twin-guide laser diode with sampled gratings is a monolithically integrated device that utilizes a vertical integration scheme to realize an electronically and widely tunable distributed feedback (DFB)-type laser. Owing to its DFB- type structure, it possesses many advantages, such as large continuous tuning ranges, simple wavelength tuning scheme, and promising dynamic characteristics. In this paper, we detail on the design of the sampled grating tunable twin-guide laser and discuss its performance. Recent devices achieve tuning ranges over 40 nm along with high side-mode suppression (ges35 dB) as well as large output power (ges10 mW).

NONLINEAR CONTROL OF CONTINUOUS POLYMER REACTORS VIA PASSIVATION

A nonlinear passive control to stabilize continuous free-radical solution polymer reactors is presented, with temperature, level and flow measurements. First, the state-feedback problem is addressed with a constructive control framework via passivation by backstepping, yielding the solvability conditions and the attainable closed-loop behavior, or the recovery target for the output-feedback (OF) design. The resulting OF control consists of volume and cascade temperature controllers, a ratio-type monomer controller, and an inventory-type MW controller. The temperature and monomer control components do not need polymerization kinetics and heat transfer models. The MW controller component only requires initiation and transfer rate constants. The proposed control technique has a systematic construction and a simple tuning scheme, and is tested with an industrial size reactor via simulations.

Testing robustness and performance of PSS–AVR schemes for synchronous generators using finite-element models

The design and tuning of power system stabilizers (PSS) and automatic voltage regulators (AVR) of synchronous generators is usually performed using low-order two-axis models. Remarkable robust characteristics and systematic construction can be obtained with the recent developments on linear and nonlinear control theory. However, the properties and performance of the control designs are also evaluated using low-order equivalent-circuit models because large synchronous machines are not readily available to designers and researches. This may lead to doubts about the controller behavior under true operating conditions. The main objective of this work is to show that robust control designs, obtained with small order models, keep their good performance characteristics when applied to the actual machine. In order to circumvent the lack of the real machine, a very detailed finite-element model is developed to represent turbine generators connected to large power systems. The numerical model incorporates simulation of rotor motion, iron magnetic nonlinearity and eddy currents in the solid rotors of turbine generators. The control design is performed using constructive nonlinear control, which gives a systematic controller construction coupled to a simple tuning scheme.

Backstepping design of composition cascade control for distillation columns

AbstractAlthough the cascade control of distillation columns had been extensively studied, some aspects still remain unexplored or unresolved. For instance, a unifying approach is needed to systematize the existing ad hoc controller constructions, to rigorously explain their remarkably robust property in using rather simple input‐output linear models, and to explore the possibility of improving their construction and functioning. Some of these problems are addressed by the recently developed backstepping‐passivation approach in constructive nonlinear control, yielding a systematic controller construction coupled to a simple tuning scheme that can be executed with standard tuning rules, a closed‐loop stability criterion, an explanation of the closed‐loop dynamics behavior, and controllers that perform better than existing ones. The applicability of the theoretical results and their controller construction‐tuning schemes are illustrated by considering the single‐ and dual‐point control cases of a binary acetone‐ethanol distillation column.