Open-loop Conditions Research Articles

Design and Implementation Procedure of a High-Gain Three-Input Step-Up 1 kW Converter

The use of different sources to energize a load is convenient in many applications, particularly those where two or more renewable energy sources are employed, such as energy harvesting, hybrid vehicles, and off-grid systems. In these cases, a multi-input converter is able to admit sources with different characteristics and, if necessary, select the output power of each source. Several topologies of multi-input converters have been proposed to this aim; however, most of them are based on multistage designs, which decreases efficiency and increases control complexity, particularly when more than two sources are used. In this work, a three-input step-up converter, easy to control in open loop condition, is analyzed. A designed procedure is described, and experimental results are presented for a 1 kW power converter. The implemented converter results in a higher voltage gain and less storage element, keeping high efficiency compared to similar topologies. Using the procedure here proposed, this converter that was initially designed for photovoltaic applications is enabled to be used in medium- and high-power applications, for example, when renewable energy sources are used.

Electronic noise analysis and in-orbit resolution verification of an electrostatic accelerometer

Based on the working principle of the signal detection and servo feedback control of the electrostatic accelerometer, in this paper, the main electronic noise components affecting the measurements of the accelerometer are analyzed and the corresponding expressions are determined. The resolution of the designed electrostatic accelerometer is lower than 10[Formula: see text]m/s2/Hz[Formula: see text], which cannot be verified directly due to limitations imposed by the vibration of the ground environment. However, it can be evaluated indirectly by the testing of electronic noise under open-loop conditions. Through this process, the resolution of 3× 10[Formula: see text]m/s2/Hz[Formula: see text] of the Taiji-1 inertial sensor was verified and found to be in agreement with results obtained in orbit.

Closed-Loop Control of a Helmholtz Coil System for Accurate Actuation of Magnetic Microrobot Swarms

Magnetic microrobot swarms have attracted lots of research interests in the robotics field. Since the remote actuation of swarm can be affected by the accuracy of the external magnetic field, electro-magnetic systems capable of generating precise magnetic fields have great value. In this work, we propose a closed-loop control scheme for 3-axis Helmholtz coil system to improve the field generation performance. Each coil is connected to and driven by a commercial servo amplifier, and the mathematical model of the system is obtained by the sweeping frequency method. With the identified model, a current controller based on the model predictive control (MPC) is presented, the states of the system and the lumped disturbance are observed by a 4th-order super-twisting sliding mode observer (STSMO) for control input calculation and disturbance compensation. To evaluate the effectiveness of the proposed control scheme, we conduct experiments on a lab-made 3-axis Helmholtz coil system. Results indicate that the bandwidth of the system can be increased to 50 Hz, and the settling time can be reduced to 0.9 ms and 0.83 ms for the outer coil and middle coil, respectively. Moreover, rotating fields with different frequencies are generated with and without the proposed scheme to actuate magnetic vortex-like microswarms. The swarm deforms to an ellipse with shape ratio equals to 0.45 as the frequency increases in the open-loop condition, in contrast to which with the proposed control scheme shows a more accurate and controllable circular pattern.

Dynamics augmentation for high speed flying yacht hulls through PID control of foiling appendages

A numerical investigation is conducted in order to identify a PID control loop feedback scheme able to return dynamics augmentation and superior seakeeping characteristics in the application of high speed flying yacht hulls. An existing lumped parameters model based on general unsteady equations of motion is extended and implemented in combination with a regular basic ocean waves model, to conduct parametric studies and predict the overall performances of a specific engine-propelled flying yacht hull, both in calm and rough water conditions. The unsteady behavior of six foiling/maneuvering appendages is investigated, the hydrodynamic characteristics being based on a database generated through the use of computational fluid dynamics methods (CFD) coupled with static/dynamic-mesh schemes. Equations of motion and hydrodynamics are solved numerically by explicit time-integration method. By comparison with control open-loop conditions, the results show the effects of the use of PID controllers in such dynamic systems in terms of seakeeping performances and dynamics augmentation.

A Non-Pulsating Input Current Step-Up DC/DC Converter With Common Ground Structure for Photovoltaic Applications

Many of the High Gain Step-Up DC/DC converters proposed in the literature do not share common ground and have a pulsating or discontinuous input current, making the converter unsuitable for solar photovoltaic applications. In this article, a non-pulsating input current (NPIC) with a high-gain DC/DC step-up converter is proposed and analyzed in detail. The converter shares a common ground structure and a voltage conversion ratio more than twice that of the Traditional quadratic boost converter (TQBC). The converter has two switches that operate in phase, which makes it easy to control. Also, the voltage stress across all semiconductor devices is lower than the output voltage, which enhances the efficiency of the converter. The loss analysis is carried out with the PLECS software, integrating the real models of switches and diodes from the technical datasheet. To confirm and validate the functionality of the proposed converter, a 200 W hardware prototype is being developed in the laboratory. It was observed that the maximum efficiency was 94.5% with an input voltage of 16V. The converter achieves high gain at low duty cycles and has been shown to perform well in open loop conditions.

Coherent beam combining of a nine-fiber laser array using an all-optical ring cavity feedback loop based on diffractive optical element

Our study describes the development of coherent beam combining of an array of nine fiber lasers using an all-optical ring cavity feedback loop based on a diffractive optical element to achieve a single-aperture output. Nine 300-mW Yb-doped fiber amplifier beams arranged in a 1 × 9 end-cap array were combined to achieve a single-aperture beam with a power of 739 mW and a beam quality (M2) of 1.18 with 21.5% combining efficiency. The optical spectra, far-field distributions, and time-domain characteristics of the combined beams were investigated under open- and closed-loop conditions. Under open-loop conditions, the far-field coherent visibility changed constantly from 72.1% to 90.9% and the fluctuation intensity was strong. Under closed-loop conditions, the system achieved a steady state with a visibility of 98.6% and an average feedback intensity of 0.4 V, indicating the occurrence of phase locking. Furthermore, mode hopping was observed when there were more than four channels in a combination. However, the system interference pattern remained stable. Comprehensive research on the relevant literature indicated that novel filled-aperture CBC was achieved using an all-optical ring cavity feedback loop based on a DOE.

A self-attachable and self-alignable micro electromagnetic linear actuator

This paper presents the design, fabrication and characterization of a novel micro electromagnetic linear actuator, which exhibits two highlights: slider self-alignment and self-attachment capability. Such characters are realized by deliberately utilizing the attractive force between the permanent magnets (Nd2Fe14B) of the slider and nickel ferromagnetic cores embedded in the stator. Actuation is achieved via thrust from both meander micro copper coils and nickel ferromagnetic cores in the stator to the permanent magnets of the slider. The actuator is fabricated by the micro machining process. The surface magnetic property of the slider is simulated and experimentally measured. The eccentric experiment is conducted to evaluate the attraction force between the slider and stator, which proves its self-attachment characteristics. The device is actuated by two-phase sinusoidal currents with a 0.5 A amplitude under an open-loop condition. The slider demonstrates self-alignment movements before moving forward when misalignment occurs. The actuation experimental results show that the average velocity of the slider reaches 4 mm s–1 and 12 mm s–1 at 10 Hz and 30 Hz, respectively. Further increasing the input frequency to 50 Hz leads to the unsteady actuation state, indicating the actuator bandwidth is less than 50 Hz under an open-loop condition.

Fabrication and characterization of micro electromagnetic linear actuators

This paper on the reports design, fabrication and position monitoring of a micro electromagnetic linear actuator. The actuator consists of stator, slider, guide, sensors and affiliated jigs. Actuation is achieved through ampere force between two phase micro-coils (copper) on the stator and permanent magnets (thick NdFeB film) on the slider. During the slider’s movement in the guide slot, tunnelling magneto-resistance (TMR) sensors are utilized to sense the magnetic field to realize position monitoring. TMR is chosen because it owns advantages of small size, large sensitivity and easy integration with micro devices. Purpose of this research is to report the micro fabrication of thick magnet films and testify the possibility of using TMR as position monitoring sensors. Actuators are fabricated by micro-electro-mechanical system process (stator and guide) and precise machining (slider and jigs). Surface magnetic field generated by the slider, driving characteristics of the actuator as well as the position monitoring capabilities of TMR elements are simulated and experimented, respectively. The slider attains 60 mm s−1 speed by sinusoidal input signal at 300 Hz frequency and 0.2 A current magnitude. Actuation bandwidth is between 300 Hz and 500 Hz at open loop condition. The maximum position monitoring error in present work is 2.2% with 101 μm value for 4.5 mm stroke.

Fuzzy Logic Control Design On Buck Converter For Thermo Electric Air Cooler Power Supply

The air conditioning system that is commonly used today is an Air Conditioner (AC). Unfortunately, this system is a big contributor to global warming. Often times, we find that air conditioners are only used to cool only a small part of a room for individual comfort. Therefore, a new breakthrough is needed from a cooling system that does not use chemicals so that it is environmentally friendly, namely using the Thermo Electric Cooler (TEC) cooling module which utilizes the cold side of the Thermo Electric Cooler (TEC). The size of the DC input voltage on the Thermo Electric Cooler (TEC) is adjusted using a buck converter with fuzzy control. When the buck converter closed loop condition with fuzzy control has a rise time value, the settling time and error percentage have a relatively better value than the open loop condition. When the buck converter set point 40V, the minimum water temperature in the air cooler can be reached 220C, when the buck converter set point is 48V the minimum water temperature in the water cooler can be reached 190C, and when the buck converter set point is 56V the minimum water temperature in the air cooler can be reached 180C. When the water cooler uses air cooler by Peltier, the input air temperature and output air temperature decrease in temperature around 10C. this is caused by the evaporative effect caused by water cooled by the peltier.

Integrated Current Balancing Transformer Based Input-Parallel Output-Parallel LLC Resonant Converter Modules

The input-parallel output-parallel (IPOP) connected converter system allows the use of a low-power converter module for high-power applications. However, mismatches in the IPOP circuit parameters cause uneven current sharing between the constituent modules, which makes the IPOP system unreliable for practical use. Different techniques have been proposed so far; however, they cause an increase in magnetic volume, cost, component count, and complexity of the IPOP system. In this article, a reliable and efficient magnetic integration technique is proposed for the current sharing requirements of the IPOP system based on LLC resonant converter modules. The proposed integrated magnetic current balancing transformer (ICBT) based IPOP LLC resonant converter modules ensures both the input current sharing and output current sharing between constituent LLC modules, under the open-loop condition quite effectively. The proposed ICBT is the resonant inductors of LLC resonant converter modules, coupled to perform the function of current balancing as well as generates enough leakage inductances for resonance operation, simultaneously. Thus, it can reduce the overall magnetic volume and improves power density of the IPOP LLC modules. Moreover, the current sharing performances of the proposed ICBT in both the steady-state and dynamic-state are analyzed based on the magnetic and electrical model. To validate the performance of the proposed ICBT based IPOP two LLC modules, a 2.6-kW hardware prototype was designed, fabricated, and tested successfully.

Linear reversing control of semi-trailer trains based on hitch angle stable and feasible domain

A linear reversing control strategy based on the stable and feasible domains of a hitch angle is proposed to address the linear reversing problem with expectation caused by unstable open-loop conditions of semi-trailer trains during reverse driving. In the reversing process, the coupling relationship amongst the location parameters, such as hitch angle, semi-trailer posture angle and axis offset, including the influence of these parameters on the reversing stability and feasibility of semi-trailer trains, is analysed. The stable and feasible domains of the hitch angle when the semi-trailer is reversed in an expected straight line are determined. Based on this, the semi-trailer linear reversing control strategy is established. The tracking control of the linear reversing path is adopted by the variable universe fuzzy control, and the co-simulation based on ADAMS and MATLAB/Simulink and the subsequent actual vehicle experiment are conducted. Simulation and experimental results show that the proposed linear reversing control strategy of the semi-trailer based on the hitch angle stable and feasible domains can accurately realise the linear reverse-path tracking of the semi-trailer train, effectively avoiding the problems of jack-knife and trailer swing during the reversing process. Thus, the difficulty of the straight reverse operation is substantially reduced.

The effects of clinically-derived parametric data uncertainty in patient-specific coronary simulations with deformable walls.

Cardiovascular simulations are increasingly used for noninvasive diagnosis of cardiovascular disease, to guide treatment decisions, and in the design of medical devices. Quantitative assessment of the variability of simulation outputs due to input uncertainty is a key step toward further integration of cardiovascular simulations in the clinical workflow. In this study, we present uncertainty quantification in computational models of the coronary circulation to investigate the effect of uncertain parameters, including coronary pressure waveform, intramyocardial pressure, morphometry exponent, and the vascular wall Young's modulus. We employ a left coronary artery model with deformable vessel walls, simulated via an Arbitrary-Lagrangian-Eulerian framework for fluid-structure interaction, with a prescribed inlet pressure and open-loop lumped parameter network outlet boundary conditions. Stochastic modeling of the uncertain inputs is determined from intra-coronary catheterization data or gathered from the literature. Uncertainty propagation is performed using several approaches including Monte Carlo, Quasi Monte Carlo sampling, stochastic collocation, and multi-wavelet stochastic expansion. Variabilities in the quantities of interest, including branch pressure, flow, wall shear stress, and wall deformation are assessed. We find that uncertainty in inlet pressures and intramyocardial pressures significantly affect all resulting QoIs, while uncertainty in elastic modulus only affects the mechanical response of the vascular wall. Variability in the morphometry exponent used to distribute the total downstream vascular resistance to the single outlets, has little effect on coronary hemodynamics or wall mechanics. Finally, we compare convergence behaviors of statistics of QoIs using several uncertainty propagation methods on three model benchmark problems and the left coronary simulations. From the simulation results, we conclude that the multi-wavelet stochastic expansion shows superior accuracy and performance against Quasi Monte Carlo and stochastic collocation methods.

Dispersion characteristics of wave propagation in layered piezoelectric structures: Exact and simplified models

This article presents a study of the dispersion characteristics of wave propagation in layered piezoelectric structures under plane strain and open-loop conditions. The exact dispersion relation is first determined based on an electro-elastodynamic analysis. The dispersion equation is complicated and can be solved only by numerical methods. Since the piezoelectric layer is very thin and can be modeled as an electro-elastic film, a simplified model of the piezoelectric layer reduces this complex problem to a non-trivial solution of a series of quadratic equations of wave numbers. The model is simple, yet captures the main phenomena of wave propagation. This model determines the dispersion curves of PZT4-Aluminum layered structures and identifies the two lowest modes of waves: the generalized longitudinal mode and the generalized Rayleigh mode. The model is validated by comparing with exact solutions, indicating that the results are accurate when the thickness of the layer is smaller or comparable to the typical wavelength. The effect of the piezoelectricity is examined, showing a significant influence on the generalized longitudinal wave but a very limited effect on the generalized Rayleigh wave. Typical examples are provided to illustrate the wave modes and the effects of layer thickness in the simplified model and the effects of the material combinations.

Surface based variable thickness slicing modeling for laser metal deposition

Laser metal deposition (LMD) has been a promising additive manufacturing technology widely used in mold rapid manufacturing. In order to improve the capacity of LMD for complex curved surface structures, a surface based variable thickness slicing (S-VTS) model is proposed to adaptively generate the LMD process based on the geometric characteristics of structures. Two deposition strategies in scanning and overlapping directions are designed to enable variable thickness of each cladding layer by dynamically adjusting the scanning speed and overlapping rate. To improve the surface quality and forming efficiency, the discrete particle swarm optimization (DPSO) algorithm is adopt to optimize the process parameters of S-VTS model, including the number of cladding layer, scanning pass, and segment per pass. Several experiments are conducted to form the cuboid samples with wavy and freeform surface and verify the feasibility of the S-VTS model. The results demonstrate that under the open-loop control condition, the geometric accuracy, surface quality, and efficiency of the proposed method is improved in comparison with uniform thickness slicing (UTS) deposition. Moreover, heterogeneous microstructure is always generated by the S-VTS method in terms of grain size and growth direction.

Development of a very high sensitivity magnetic field sensor based on planar Hall effect

While planar Hall effect based magnetic field detection is a well-studied area, the sensing capabilities of ‘Hall cross’ sensors had not improved significantly for more than a decade. Here we report a major improvement in the sensing characteristics of ‘cross’ geometry by using pulsed laser ablation grown Permalloy as sensing material. Our sensor has two modes of operation. In the linear regime, it has a field sensitivity of 650 Ω/T with an estimated detection threshold of 5nT in open-loop condition. In switching applications, it shows a 400% output voltage swing in a range of ±0.3 mT, a value comparable with modern TMR sensors at room temperature. These values, which are the highest reported for the ‘cross’ geometry, make it applicable in a wide range of scenarios like geomagnetic field and magnetic anomaly detection. The small size of the sensing area also makes it a desirable choice for magnetic microbead based biomolecule detection.

A Hybrid Compensation Scheme for the Gate Drive Delay in CLLC Converters

The CLLC converter is often used as an isolated linker between high- and low-voltage buses where the CLLC converter operates under the open-loop condition at a resonant frequency. In such applications, CLLC converters are able to achieve high efficiency usually due to the superior performance of soft switching. However, we found that the operating process of a CLLC converter under open-loop control at the resonant frequency will significantly change by the nonideal parameters of the semiconductor switches and gate driver circuits. These impacts on the converter operation were investigated and defined as the gate drive delay. We present a comprehensive steady-state analysis for the CLLC converter that considers the gate drive delay including its operating process, mathematical model, power loss, and voltage ripple. In some cases, the gate drive delay changes the operating process of the CLLC converter. As a result, the soft-switching condition changes or even loses, large circulating current exists on the secondary side, output voltage ripples become larger, and so that the efficiency decreases dramatically. Therefore, a hybrid compensation scheme, consisting of an offline design procedure and an online closed-loop control algorithm, is proposed to minimize the resonant-frequency variation due to the gate drive delay. Both the correctness of the steady-state analysis and effectiveness of the proposed hybrid compensation scheme are verified by the experiment. Using the proposed compensation scheme can reduce the output voltage ripple to one-third of the original value and increase the efficiency by more than 10% within the whole load range.

Planned Heating Control Strategy and Thermodynamic Modeling of a Natural Gas Thermal Desorption System for Contaminated Soil

This paper presents a planned heating control strategy applied for a natural gas thermal desorption system for polluted soil to achieve the dynamic adjustment of the heating time and energy consumption. A lumped-parameter model for the proposed system is established to examine effects of the natural gas mass flow rate and the excess air coefficient on the heating performance of the target soil. The control strategy is explored to accomplish the heating process as expected with constant temperature change rate or constant volumetric water content change rate at different phases by adapting the natural gas flow. The results demonstrate that the heating plan can be realized within the scheduled 36 days and the total natural gas consumption can be reduced by 24% (1487 kg) compared to that of the open-loop reference condition, which may be widely applied for other thermal remediation systems of the polluted soil.

MULTIFIDELITY ESTIMATORS FOR CORONARY CIRCULATION MODELS UNDER CLINICALLY INFORMED DATA UNCERTAINTY.

Numerical models are increasingly used for noninvasive diagnosis and treatment planning in coronary artery disease, where service-based technologies have proven successful in identifying hemodynamically significant and hence potentially dangerous vascular anomalies. Despite recent progress towards clinical adoption, many results in the field are still based on a deterministic characterization of blood flow, with no quantitative assessment of the variability of simulation outputs due to uncertainty from multiple sources. In this study, we focus on parameters that are essential to construct accurate patient-specific representations of the coronary circulation, such as aortic pressure waveform and intramyocardial pressure, and quantify how their uncertainty affects clinically relevant model outputs. We construct a deformable model of the left coronary artery subject to a prescribed inlet pressure and with open-loop outlet boundary conditions, treating fluid-structure interaction through an arbitrary-Lagrangian-Eulerian framework. Random input uncertainty is estimated directly from repeated clinical measurements from intracoronary catheterization and complemented by literature data. We also achieve significant computational cost reductions in uncertainty propagation thanks to multifidelity Monte Carlo estimators of the outputs of interest, leveraging the ability to generate, at practically no cost, one- and zero-dimensional low-fidelity representations of left coronary artery flow, with appropriate boundary conditions. The results demonstrate how the use of multifidelity control variate estimators leads to significant reductions in variance and accuracy improvements with respect to traditional Monte Carlo. In particular, the combination of three-dimensional hemodynamics simulations and zero-dimensional lumped parameter network models produces the best results, with only a negligible (less than 1%) computational overhead.

AI Algorithm-Based Two-Stage Optimal Design Methodology of High-Efficiency CLLC Resonant Converters for the Hybrid AC–DC Microgrid Applications

Thanks to the advantages of high power density and the capacity of bidirectional power transfer, the CLLC resonant converter is widely used in the hybrid ac-dc microgrid as a dc transformer to interlink the ac and dc bus. Since the voltages of ac and dc bus are controlled by the energy management system, the CLLC resonant converter operates under open-loop condition, which means the switching frequency and duty cycle are fixed. As a result, in the hybrid ac-dc microgrid applications, for the CLLC converter, the main concern is not the voltage regulation but the conversion efficiency. This paper focuses on the total power loss optimization and the magnetic design of the CLLC resonant converter based on artificial intelligence (AI) algorithm. In order to optimize the total power loss, an AI algorithm-based two-stage optimal design method is proposed. In the first stage, the total power loss, including the driving loss, turn-off loss, conduction loss of the switches, the power loss of the resonant capacitances, and copper and core loss of the transformer are optimized by the proposed AI algorithm, GA+PSO, and the optimal parameters, including the leakage inductances (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r1</sub> and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r2</sub> ), magnetizing inductance (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ), and resonant capacitances (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r1</sub> and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r2</sub> ) are derived. In the second stage, the optimal leakage inductances and magnetizing inductance are realized by setting proper distance between the primary winding and the secondary winding (d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</sub> ), and the thickness of the air gap (d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> ). As for the magnetic design, in this paper, the leakage inductances of a planar transformer are used as the resonant inductances. The equations of dw and da to achieve the optimal leakage inductances and magnetizing inductance are derived. Both the proposed optimal design method and the equations of dw and da are validated by simulations and experiments.

PI and PID Controller Design and Analysis for DC Shunt Motor Speed Control

This paper proposes a step by step procedure design and analysis of proportional Integral (PI) and proportional integral derivative (PID) controller. These controllers are employed to control the speed of a DC shunt motor. DC shunt motor Characteristics are modeled in s-function, the speed characteristic of motor is analyzed in open loop condition and closed loop condition without controller and Parameter controlling of PI &amp; PID controller is designed by frequency response analysis. Design, analysis and implementation of PI &amp; PID controller are conducted separately. The performances controllers such as rise time (tr), settling time (ts), steady state error, percent overshoot (%OS), and phase margin are compared to both controllers. Design and analysis of controller are verified by simulation, the results show that PID controller that applied speed control DC shunt motor is better than PI controller.