Simple Tuning Research Articles

Towards Automated Microfluidic‐based Platforms: Optimizing Hydrogenation Efficiency of Nitrobenzene through π–π Interactions in Pd Nanoparticles on Covalent Organic Frameworks

AbstractMicroplatform with timed automata has been leveraged for guiding the preparation of molecules, whereas the requirement of handling expertise and sophisticated instrument is inevitable in combination with heterogeneous catalysis. Here we report a microfluidic‐based autolab with open structures, called Put & Play Automated Microplatform (PPAM). It shows the efficient hydrogenation performance of palladium nanoparticles on the triphenylene‐based covalent organic frameworks (Pd/TP‐COFs) in which the π–π interactions of TP rings in the vicinity of Pd is optimized by easy change‐over of catalyst and simple tuning of reactor geometries in PPAM. Using experiment/simulation of the Pd/TP‐COFs coating (PCC) and mixing (PCM) across PPAM with different channel sizes, the turnover frequencies are 60 times the commonly used batch reactor, and aniline productivity of 8.8 g h−1 is achieved in 0.09 cm3. This work will raise awareness about the benefits of the catalyst‐loaded microplatform in future materials performance campaigns.

Towards Automated Microfluidic-based Platforms: Optimizing Hydrogenation Efficiency of Nitrobenzene through π-π Interactions in Pd Nanoparticles on Covalent Organic Frameworks.

Microplatform with timed automata has been leveraged for guiding the preparation of molecules, whereas the requirement of handling expertise and sophisticated instrument is inevitable in combination with heterogeneous catalysis. Here we report a microfluidic-based autolab with open structures, called Put & Play Automated Microplatform (PPAM). It shows the efficient hydrogenation performance of palladium nanoparticles on the triphenylene-based covalent organic frameworks (Pd/TP-COFs) in which the π-π interactions of TP rings in the vicinity of Pd is optimized by easy change-over of catalyst and simple tuning of reactor geometries in PPAM. Using experiment/simulation of the Pd/TP-COFs coating (PCC) and mixing (PCM) across PPAM with different channel sizes, the turnover frequencies are 60 times the commonly used batch reactor, and aniline productivity of 8.8 g h-1 is achieved in 0.09 cm3 . This work will raise awareness about the benefits of the catalyst-loaded microplatform in future materials performance campaigns.

Organic-Cation Modulated Assembly Behaviors of a Ureidopyrimidone-Grafting Cluster.

Ureidopyrimidone (UPy) is an important building block for constructing functional supramolecular polymers and soft materials based on their characteristic quadruple hydrogen bonds. While the evidence from the single-crystal X-ray diffraction data for the existence of linear hydrogen bonding has still been absent up to now. To obtain the crystals of UPy-containing molecules with high quality, enhanced rigidity and crystallinity are expected. Herein, an inorganic Anderson-Evans type cluster [Mn(OH)6Mo6O18]3-, which can provide suitable stiffness and charge, is used as a linker to covalently anchor two UPy units. The prepared organic-inorganic polyanion with three negative charges has a linear architecture, which is prone to form an infinite one-dimensional structure based on the supramolecular forces. The results indicate that the combination models of UPy units can be conveniently modulated by organic counter cations with different sizes, and therefore three unreported models are observed under various conditions. The present study gives a unique understanding of the intermolecular interactions in UPy-based supramolecular polymers and also provides a simple tuning method, which benefits the construction of functional materials and the adjustment of their properties.

Robust 2DoF PI tuning rules for integrating processes with dead time via frequency response model matching

The integrating characteristics are commonly found in composition control and level control of a distillation column in chemical processes. This paper presents a simple and intuitive robust tuning method of two-degree-of-freedom (2DoF) proportional-integral (PI) controller for integrating processes with dead time. The frequency response model matching approach is utilized with performance and robustness considerations for both regulatory and servo control issues. The regulatory control issue aims at matching the frequency response of the closed-loop system with that of the reference model for disturbance rejection, where the feedback controller parameters are calculated by solving a group of overdetermined algebraic equations subject to a robustness constraint evaluated by the maximum sensitivity. The target of the servo response is to follow a prescribed set-point reference trajectory, with the set-point weighting factor tuned to satisfy a defined tracking performance metric. A curve fitting procedure is utilized to generate analytical tuning rules in terms of the process model parameters and the desired robustness specification. It is shown that, apart from giving more exact achievement of the control system robustness, the tuning rules presented work well for a wider range of process dynamics than the existing methods. Illustrative examples are given to show the effectiveness of the proposed method.

A simplified model of flexible power point tracking algorithms in double-stage photovoltaic systems

Traditionally, photovoltaic (PV) systems have been operated using maximum power point tracking algorithms, which force the PV arrays to produce the maximum available power at all times. Nevertheless, distribution system operators are increasingly asking for flexible power point tracking (FPPT) algorithms, which allow the regulation of the PV power to a predefined reference value. FPPTs are difficult to tune and often have non-linear behavior. It complicates the modeling of PV systems for power system stability studies. This paper proposes a simplified model that reproduces the dc-side dynamics of a double-stage FPPT-controlled PV system. In addition to its simple tuning, the key advantage of the proposed model is that it can be easily translated into differential equations, which can be used in stability analyses. The proposed model is validated on a temporal simulation as well as a small-signal stability study.

An Alternative Nonlinear Lyapunov Redesign Velocity Controller for an Electrohydraulic Drive

This research aims at developing control law strategies that improve the performances and the robustness of electrohydraulic servosystems (EHSS) operation while considering easy implementation. To address the strongly nonlinear nature of the EHSS, a number of control algorithms based on backstepping approach is intensively used in the literature. The main contribution of this paper is to consider an alternative approach to synthetize a Lyapunov redesign nonlinear EHSS velocity controller. The proposed control law design is based on an appropriate choice of the control lyapunov function (clf), the extension of the Sontag formula and the construction of a nonlinear observer. The clf includes all the three system variable states in a positive define function. The Sontag formula is used in the time derivative of our clf in order to ensure an asymptotic stabilizing controller for regulating and tracking objectives. A nonlinear observer is developed in order to bring to the proposed controller the estimated values of the first and the second time output derivatives. The design, the tuning implementation and the performances of the proposed controller are compared to those of its equivalent backstepping controller. It is shown that the proposed controller is easier to design with simple implementation tuning while the backstepping controller has several complex design steps and implementation tuning issue. Moreover, the best performances especially under disturbance in the viscous damping are achieved with the proposed controller.

Design of Robust Polynomial Beamformers Using Worst Case Performance Optimization via Alternating Direction Method of Multipliers

This paper studies the design of robust polynomial beamformers (RPBs) for microphone arrays, which enable dynamic beam steering via simple online parameter tuning, under the criterion of worst-case performance optimization (WCPO). Although the WCPO criterion has been widely adopted in the design of various robust beamformers, conventional approaches using the WCPO criterion may not be applicable to the RPB design, due to the conservativeness problem resulting from the special structure of polynomial beamformers. In this paper, we propose to design the RPBs based on the semidefinite programming (SDP) using the WCPO criterion. Nevertheless, the resulting design optimization problems are highly computationally demanding. To overcome the computational difficulty, we then propose to solve the high-dimensional optimization problems for the RPB design using the alternating direction method of multipliers (ADMM) algorithm. By introducing auxiliary variables in the framework of ADMM, the original high-dimensional optimization problems are decomposed into several subproblems which are easier to handle. The algorithms to solve the corresponding subproblems are developed. Simulation and real-world experimental results show that the proposed SDP-based RPB design performs much better than its existing counterpart. Moreover, the computational efficiency can be significantly improved by using the proposed ADMM algorithm while the existing solution is very time-consuming and even fails.

Active voltage damping method with negative DC link current feedback in electric and hybrid electric transmissions

Electric and hybrid electric transmissions in traction drive have a limited capacity power source. Since the traction drive operates in the torque source mode, the DC link voltage becomes unstable and goes into oscillatory mode. This leads to the software protection reaction which prevents the traction inverter overvoltage breakdown. The transition boundary to the oscillatory mode is determined by the power and the value of the capacitance installed in the electric transmission DC link. To increase reliability of the traction inverters, large-capacity electrolytic capacitors are replaced with small-capacity film capacitors which makes the system more prone to oscillations. To solve this problem, active damping methods are used allowing changing the engine dynamic characteristics by means of the control system. The software methods with power and torque proportional control are most widely used. Proportional power control is the simplest method in which the traction drive simulates an RL load. The torque proportional control method adjusts the torque reference according to the change in the DC link voltage. This paper proposes a new negative DC link feedback method. In this case, the torque is adjusted dynamically depending on the current consumed by the traction inverter from the electric transmission common DC link. Mathematical modeling methods were used to compare the known and proposed methods of DC link voltage active damping. Mathematical models have been developed in the MATLAB Simulink environment which makes it possible to investigate the damping capacity at various values of the power consumed by the traction inverter. It is shown that the proposed method with negative DC link current feedback demonstrated tuning simplicity. In comparison with proportional power and torque control methods, the proposed option is robust when setting parameters, provides a large damping coefficient over the entire range of traction drive power, and has a short duration of the transient process. The proposed method can be used to suppress DC link voltage oscillations on any type of hybrid electric and all-electric vehicles traction inverters and ensures stable and reliable equipment operation.

Development and research of the control system of the electric drive of panoramic windscreen wipers

BACKGROUND: The issue of coordinated control of vehicles windscreen wipers, not linked to each other with mechanical joints, is related to aiming to make the equipment more compact. Modern microprocessor controlling are helpful to solve this issue with use of electric drive as well as problems of logical control and interaction with high-level controlling equipment.
 AIMS: The comprehensive solution of the issue of coordinated control of movement of panoramic windscreen wipers without mechanical links as well as the solution of secondary problems of control with use of tools of electric drive considering various factors.
 METHODS: The algorithm of windscreen wipers movement coordination in nontracking system of automatic stabilization of electric motors rotation velocities with positioning in trajectories control points. Among the factors, necessary to consider in development, there are design of mechanism of windscreen wipers, the characteristic of mechanical load on them, type and location of sensors, required dynamics and accuracy of coordinates adjustment, behavior of electromagnetic processes in power converter and restriction of computing capabilities of a microcontroller.
 RESULTS: The electric drive ensures visually balanced coordinated movement of windscreen wipers, which is resistant to load change caused by the condition of the windscreen as well as torques of gravity force acting on the windscreen wipers. The logical control based on discrete switches ensures selection of the movement mode, whereas the connection through digital circuits ensures data exchange with the controlling equipment. Technical solutions ensuring simple tuning of the electric drive are implemented.
 CONCLUSIONS: The given solution of issues of coordination of windscreen wipers movement, automatic adjustment of coordinates considering dynamics of movement control, logical control and coupling with the high-level controlling equipment has practical value for development of various control systems.

Tuning Directed Photooxidation-Induced Conversion of Pyrrole-Based Styryl Coumarin Dual-Color Photoconverters.

Invited for the cover of this issue is the group of Mayeul Collot at the University of Strasbourg (CNRS). The image depicts the effect of simple chemical tuning on coumarin dyes to tune and improve the DPIC photoconversion mechanism. Read the full text of the article at 10.1002/chem.202203933.

Hybrid Dielectric-Plasmonic Nanoantenna with Multiresonances for Subwavelength Photon Sources

The enhancement of the photoluminescence of quantum dots induced by an optical nanoantenna has been studied considerably, but there is still significant interest in optimizing and miniaturizing such structures, especially when accompanied by an experimental demonstration. Most of the realizations use plasmonic platforms, and some also use all-dielectric nanoantennas, but hybrid dielectric-plasmonic (subwavelength) nanostructures have been very little explored. In this paper, we propose and demonstrate single subwavelength hybrid dielectric-plasmonic optical nanoantennas coupled to localized quantum dot emitters that constitute efficient and bright unidirectional photon sources under optical pumping. To achieve this, we devised a silicon nanoring sitting on a gold mirror with a 10 nm gap in-between, where an assembly of colloidal quantum dots is embedded. Such a structure supports both (radiative) antenna mode and (nonradiative) gap mode resonances, which we exploit for the dual purpose of out-coupling the light emitted by the quantum dots into the far-field with out-of-plane directivity, and for enhancing the excitation of the dots by the optical pump. Moreover, almost independent control of the resonance spectral positions can be achieved by simple tuning of geometrical parameters such as the ring inner and outer diameters, allowing us to conveniently adjust these resonances with respect to the quantum dots emission and absorption wavelengths. Using the proposed architecture, we obtain experimentally average fluorescence enhancement factors up to $654\times$ folds mainly due to high radiative efficiencies, and associated with a directional emission of the photoluminescence into a cone of $\pm 17\degree$ in the direction normal to the sample plane. We believe the solution presented here to be viable and relevant for the next generation of light-emitting devices.

Electrically tunable mode-locked fiber laser using laser induced graphene assisted long-period fiber grating

We demonstrate an electrically tunable all-fiber mode-locked erbium-doped fiber laser using a long-period fiber grating (LPFG) assisted by laser induced graphene heaters (LIG-H). Wavelength tunability is achieved by the temperature-dependent transmission spectrum of the LPFG. The central wavelength can be continuously tuned from 1549.00 nm to 1563.63 nm with a spectral tuning range of 14.63 nm. The graphene on polyimide (PI) paper is fabricated using a 10.6 μm CO2 laser, which has a maximum operating temperature of around 500 °C. The proposed LPFG-based electrical tunability of mode-locked fiber laser provides a novel, repeatable, simple, and cost-effective laser tuning technique.

Two Decentralized Dynamic State Estimation Schemes for Multimachine Power Systems with Transmission Losses

This article addresses the problem of estimating the state of a multimachine power system (MPS). To work with power networks with lossy transmission lines, a variation of the classical third-order MPS is proposed by considering generators’ electrical power injected into the grid as a state variable. Based on a linear decentralized estimation model (tailored for a specific purpose), the state variables of generators (load angle, relative speed, and electrical power) together with terminal voltage magnitudes are estimated in a decentralized fashion through two new robustly convergent linear Luenberger estimators, one based on load angle measurement and the other based on relative speed measurement. The new MPS estimation model includes a set of robustly quick observable states, one per machine, which allows capturing the interaction with other generators, transmission line losses, unknown disturbances, and model errors. The result is a design superior to other related estimation techniques such as the extended Kalman filter (EKF) or Sliding Modes Perturbation Observer (SMPO) in terms of (i) a conventional-like simple pole placement-based tuning, (ii) low online computational load and disturbance rejection capability, and (iii) small gain-based convergence assessment. The performance of the proposed state estimation scheme is illustrated in a 3-machine power system under different operational conditions.

Lightweight Micro-Expression Recognition on Composite Database

The potential of leveraging micro-expression in various areas such as security, health care and education has intensified interests in this area. Unlike facial expression, micro-expression is subtle and occurs rapidly, making it imperceptible. Micro-expression recognition (MER) on composite dataset following Micro-Expression Grand Challenge 2019 protocol is an ongoing research area with challenges stemming from demographic variety of the samples as well as small and imbalanced dataset. However, most micro-expression recognition (MER) approaches today are complex and require computationally expensive pre-processing but result in average performance. This work will demonstrate how transfer learning from a larger and varied macro-expression database (FER 2013) in a lightweight deep learning network before fine-tuning on the composite dataset can achieve high MER performance using only static images as input. The imbalanced dataset problem is redefined as an algorithm tuning problem instead of data engineering and generation problem to lighten the pre-processing steps. The proposed MER model is developed from truncated EfficientNet-B0 model consisting of 15 layers with only 867k parameters. A simple algorithm tuning that manipulates the loss function to place more importance on minority classes is suggested to deal with the imbalanced dataset. Experimental results using Leave-One-Subject-Out cross-validation on the composite dataset show substantial performance increase compared to the state-of-the-art models.

A microstructure tuning strategy on hollow carbon nanoshells for high-efficient oxygen reduction reaction in direct formate fuel cells

The microstructure of carbon supports for electrocatalysts plays a crucial role in dispersing active sites, establishing oxygen/ion transport channels, and thus determining the oxygen reduction reaction (ORR) activity. A facile and simple microstructure tuning strategy is adopted to synthesize hollow carbon nanoshells (CNSs) with tuneable microstructure in this study. The CNSs with expected macroporous (300–966 nm) and mesoporous (2–5 nm) structures were achieved by adjusting heating ramp rates during pyrolysis. The CNS prepared at 1 °C min−1 (CNS-1) possesses a well-developed mesoporous/macroporous structure, which is conducive to dispersing iron phthalocyanine during the synthesis and establishing triple-phase interfaces in the catalyst layer during the ORR. Therefore, the electrocatalyst (Fe–N/CNS-1), derived from the CNSs-1, exhibits a 44 mV higher half-wave potential (0.879 V vs. RHE) in a rotating disk electrode and a 14% higher maximum power density (16.1 mW cm−2) in a membrane-less direct formate fuel cell than that of Pt/C. This study delivers a promising microstructure tuning strategy for carbon supports to construct high-efficient ORR electrocatalysts.

Model-Free VRFT-Based Tuning Method for PID Controllers

The main objective of this work was to develop a tuning method for PID controllers suitable for use in an industrial environment. Therefore, a computationally simple tuning method is presented based on a simple experiment on the process without requiring any input from the user. Essentially, the method matches the closed-loop response to the response obtained in the steady-state change experiment. The proposed method requires no prior knowledge of the process and, in its basic form, only the measurement of the change in the steady state of the process in the manually or automatically performed experiment is needed, which is not limited to step-like process input signals. The user does not need to provide any prior information about the process or any information about the closed-loop behavior. Although the control loop dynamics is not defined by the user, it is still known in advance because it is implicitly defined by the process open-loop response. Therefore, no exaggerated control signal swings are expected when the reference signal changes, which is an advantage in many industrial plants. The presented method was designed to be computationally undemanding and can be easily implemented on less powerful hardware, such as lower-end PLC controllers. The work has shown that the proposed model-free method is relatively insensitive to process output noise. Another advantage of the proposed tuning method is that it automatically handles the tuning of highly delayed processes, since the method discards the initial process response. The simplicity and efficiency of the tuning method is demonstrated on several process models and on a laboratory thermal system. The method was also compared to a tuning method based on a similar closed-loop criterion. In addition, all necessary Matlab/Octave files for the calculation of the controller parameters are provided online.

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.

Enhanced Voltage Regulation for PV Power Conversion Using Quasi-Proportional Resonant Extended State Observer

Extended state observer (ESO) is a promising control technology thanks to its robustness against model inaccuracy. This article expands the application of an ESO-based control scheme to digitally regulate a grid-tied photovoltaic (PV) power converter. It focuses on mitigating the steady-state disturbance resulting from the dc to single-phase ac conversion and dynamic disturbances caused by solar irradiance and voltage reference changes. The development is based on an in-depth analysis of PV power systems regarding the nonlinear and time-variant features. Thanks to the disturbance rejection loop, the active damping function is naturally offered, which boosts the system damping without extra sensors or complex model-based tuning. A new ESO scheme, namely quasi-proportional resonant ESO, is developed by the frequency-domain analysis, which enables the precise tracking and rejection of fast-varying sinusoidal disturbance at the targeted frequency. The advantages include simple and intuitive tuning, easy implementation, and enhanced transient and steady-state control performance. A 1.5-kW laboratory platform is built to verify the effectiveness and practicality of the proposed control scheme.

Simple Tuning of Arbitrary Controllers using Governors

The paper proposes a preliminary idea to an intuitive and straightforward mechanism for tuning arbitrary controllers and changing the closed-loop performance. While the structure and parameters of the original controller are kept unchanged, the inputs to the nominal controller are modified such that the closed-loop response becomes slower or faster. Such a governor setup implementation is advantageous, especially when re-tuning the original controller is impractical or impossible. The practicability and versatility of this approach is presented using several examples spanning from simple loops with PID controllers to complex nonlinear closed-loop systems with optimal and approximated explicit MPC.

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.