Phase Control Method Research Articles

Time-division multiplexing cascaded active phase-locking method for an all-fiber coherent beam combining system

Coherent beam combining (CBC) is an effective approach to exceed the power limitation of fiber lasers by combining multiple laser sources. Phase-locking is one of the important steps in an active CBC system. Many phase-locking methods have already been developed and have effectively achieved phase control. Generally, the phase control bandwidth decreases accordingly as the number of combined lasers increases. This will hamper the development of CBC systems to larger scales. At the same time, the structure of traditional tiled-aperture CBC systems is also a potential limiting factor in the aspect of feedback configuration. An all-fiber CBC structure based on active phase control can avoid physical size limitations on traditional structures and greatly expand the scale of tiled-aperture CBC arrays to over tens of thousands of sub-beams. In such a large array scale, existing phase control methods will inevitably encounter the problem of bandwidth reduction. To solve this problem, we propose a time-division multiplexing cascaded (TDMC) active phase-locking method in this paper. Simulation studies on phase control of over 10,000 laser beams are conducted. The method shows huge bandwidth enhancement in control phases of a large number of lasers. This will lay the technological foundation for further expanding the number of an all-fiber tiled-aperture array.

Non-uniformly Spaced Antenna Arrays with Overlapped Elements Constraint

In the literature, inter-element spacing antenna design methods have been widely discussed and presented as an alternative approach to element excitation amplitude and/or phase control methods that may be relied upon to achieve the required array pattern shapes. However, methods associated with non-uniformly distributed elements suffer from the element overlap problem, where some of the optimized element locations may overlap each other and cause changes in the overall array aperture length. Practically, these element overlaps cannot be implemented, due to the physical antenna element size, without omitting some of them. Consequently, the overall performance of the antenna array is degraded. Further, degradation may occur when considering phased arrays with scanned main beams. In this paper, we first illustrate the effect of the problem of overlapped element locations and then we propose two approaches based on the genetic algorithm to optimize non-uniformly spaced arrays with overlapped element locations, while simultaneously preserving the array's directivity. To solve the problem of overlapping and to determine the physical array element size, the minimum element-spacing constraints are incorporated in a simple way in the proposed approaches. Thus, the time required to perform optimization-related computations is greatly reduced. Simulation results confirm the effectiveness of the two proposed solutions, where the probability of the elements overlapping has been reduced to zero under specific conditions related to the locations of the some of the elements, while the peak sidelobe levels were always kept below -15 dB and directivity was maintained, to the extent possible, at the level of that of standard uniformly spaced arrays.

Acoustography by Beam Engineering and Acoustic Control Node: BEACON.

Acoustic manipulation has emerged as a valuable tool for precision controls and dynamic programming of cells and particles. However, conventional acoustic manipulation approaches lack the finesse necessary to form intricate, configurable, continuous, and 3D patterning of particles. Here, this study reports acoustography by Beam Engineering and Acoustic Control Node (BEACON), which delivers intricate, configurable patterns by guiding particles along custom paths with independent phase modulation. Leveraging analytical methods of orbital angular momentum beam via iterative Wirtinger hologram algorithm, this study accomplish acoustography by facilitating orbital angular momentum traps, enabling continuous 2D and 3D acoustic manipulation of microparticles in any desired geometry, with phase modulation independent of intensity. Utilizing on-chip acoustography, the BEACON platform markedly increases the space-bandwidth product to 31000 while attaining an enhanced resolution with a pixel size of ≈25µm, surpassing the typical resolution of over 200µm in previous holographic particle manipulation methods. The capabilities of BEACON are demonstrated in creating intricate triple helical tracing structures using microdroplets (20µm in diameter) and those carrying DNA to validate the effectiveness of the acoustography and phase control methods. This study offers new particle manipulation opportunities, paving the way for next-generation biomedical systems and the future of contact-free precision manufacturing.

Molybdenum Disulfide Induced Phase Control Synthesis of Multi‐dimensional Co3S4‐MoS2 Heteronanostructures via Cation Exchange

AbstractPhase control over cation exchange (CE) reactions has emerged as an important approach for the synthesis of nanomaterials (NMs), enabling precise determination of their reactivity and properties. Although factors such as crystal structure and morphology have been studied for the phase engineering of CE reactions in NMs, there remains a lack of systematic investigation to reveal the impact for the factors in heterogeneous materials. Herein, we report a molybdenum disulfide induced phase control method for synthesizing multidimensional Co3S4‐MoS2 heteronanostructures (HNs) via cation exchange. MoS2 in parent Cu1.94S‐MoS2 HNs are proved to affect the thermodynamics and kinetics of CE reactions, and facilitate the formation of Co3S4‐MoS2 HNs with controlled phase. This MoS2 induced phase control method can be extended to other parent HNs with multiple dimensions, which shows its diversity. Further, theoretical calculations demonstrate that Co3S4 (111)/MoS2 (001) exhibits a higher adhesion work, providing further evidence that MoS2 enables phase control in the HNs CE reactions, inducing the generation of novel Co3S4‐MoS2 HNs. As a proof‐of‐concept application for crystal phase‐ and dimensionality‐dependent of cobalt sulfide based HNs, the obtained Co3S4‐MoS2 heteronanoplates (HNPls) show remarkable performance in hydrogen evolution reactions (HER) under alkaline media. This synthetic methodology provides a unique design strategy to control the crystal structure and fills the gap in the study of heterogeneous materials on CE reaction over phase engineering that are otherwise inaccessible.

Ultrafast photo-induced O2− channel-opening in oxygen vacancy ordered SrCoO2.5 film

The recent development of electric-field controlled brownmillerite SrCoO2.5 (BM-SCO) to SrCoO3-δ phase transformation greatly enriches the controlling diversity of functional materials. However, the required potential is much larger than that for the standard electrolysis of H2O and the detailed mechanisms for the corresponding oxygen insertion are still unclear. In this study, we mimic such electric-field control step with optical pulse excitation. In specific, by exciting BM-SCO thin film with femtosecond 400 or 800 nm pulses, and monitoring the lattice dynamics using ultrafast x-ray diffraction, we find that 400 nm photo-excitation can induce a distinctive transient BM-SCO state containing both Co2+ and Co4+, which is more suitable for O2− invasion. This transient BM-SCO state is suggested to originate from the redistribution of electrons on CoT (tetragonal layer) and CoO (octahedral layer) 3d orbitals, which is further confirmed by femtosecond transient reflectance measurements. We suggest that this distinctive transient BM-SCO state, which is critical for the phase transition, is also induced during the electric-field controlled BM-SCO to SrCoO3-δ phase transformation. This study intends to contribute an intriguing research thought for the inherent mechanism that might be powerless with traditional means and a special phase control method as well.

Active phase and amplitude temperature control method for cryostat: A case in the thermodynamic temperature international comparison system

Achieving highly stable temperature control is essential for cryostats. However, the cryocooler used in cryostats, such as the pulse tube cryocooler, produces regular sinusoidal temperature fluctuations due to its inherent working principles. To establish a highly stable temperature environment, an active phase and amplitude control method for suppressing temperature fluctuation is proposed in this paper, by which the optimal phase and amplitude can be predicted in theory. To validate this approach, a thermal response model was developed based on experiments conducted in the thermodynamic temperature international comparison cryostat at approximately 3.7 K. Based on this model, we conducted both single-stage and multi-stage active temperature control experiments. The results demonstrate that the temperature control effect is the best when the active temperature control current is added at the second cold head, the fluctuation of the comparison copper block from 3.3mK to 0.166mK with 94.9 % suppression rate. The multi-stage joint temperature control reduced the temperature fluctuation with an attenuation rate of 95.4 %. These findings offer significant potential for improving temperature stability in future thermodynamic temperature comparison experiments.

Aeroacoustic analysis of fixed- and variable-pitch controlled multirotors and noise reduction via rotor phase control

This research conducts a comparative analysis of the aerodynamic and aeroacoustic characteristics of fixed-pitch and variable-pitch controlled multirotors (i.e., revolution per minute and collective pitch control). The study encompasses hovering and forward flight conditions, considering wind gust effects. Specifically, high-resolution time-frequency analysis is conducted to investigate the interference and modulation effects of multirotor noise. The analysis reveals significant variations in spectral characteristics depending on the control method. Notably, the frequencies of tonal noise from variable-pitch controlled multirotor do not exhibit short-periodic modulation, in contrast to those of fixed-pitch controlled multirotor. Considering the distinctive spectral characteristics of variable-pitch controlled multirotor, this study explores the effectiveness of noise reduction in variable-pitch controlled multirotor by implementing rotor phase control methods. To validate the noise reduction in time series simulations, a deep learning model is employed to determine the dynamically optimized rotor phases. A multilayer perceptron neural network was trained to derive the optimal rotor phase angles over time, considering the target observer points and flight conditions. The results demonstrate a substantial reduction in noise at the target observer points.

A Model-Based Self-Tuning Fully Decoupled Register Control Method for the Speed-Up Phase of Roll-to-Roll Systems

A Model-Based Self-Tuning Fully Decoupled Register Control Method for the Speed-Up Phase of Roll-to-Roll Systems

High environmentally adaptable phase control with reinforcement learning for coherent beam combination

In contemporary times, the utilization of high-power lasers is progressively expanding. However, the potential of a single laser to generate power confronts inherent physical constraints, leading to limitations in its incremental power augmentation. To address this challenge, coherent beam combining technology has been introduced as a means to achieve amplified power output. In this paper, an intelligent phase control method for coherent beam combining is proposed, which introduces reinforcement learning algorithm to provide assistance for the control problem, designs algorithmic variables based on the physical model of coherent beam combining, deploys it in the environment for multiple interactions, and updates the neural network in real time using the feedback from the environment. The efficacy of the proposed algorithm is validated in a 7-channel coherent beam combining simulation system, and the experiment results show that the synthesized beam is strong and stable under the control of the algorithm, and the convergence of the algorithm as well as the control effect is discussed and validated in different environments, and its performance also exceeds that of the existing mainstream phase control algorithm SPGD.

Molybdenum Disulfide Induced Phase Control Synthesis of Multi-dimensional Co3S4-MoS2 Heteronanostructures via Cation Exchange.

Phase control over cation exchange (CE) reactions has emerged as an important approach for the synthesis of nanomaterials (NMs), enabling precise determination of their reactivity and properties. Although factors such as crystal structure and morphology have been studied for the phase engineering of CE reactions in NMs, there remains a lack of systematic investigation to reveal the impact for the factors in heterogeneous materials. Herein, we report a molybdenum disulfide induced phase control method for synthesizing multidimensional Co3S4-MoS2 heteronanostructures (HNs) via cation exchange. MoS2 in parent Cu1.94S-MoS2 HNs are proved to affect the thermodynamics and kinetics of CE reactions, and facilitate the formation of Co3S4-MoS2 HNs with controlled phase. This MoS2 induced phase control method can be extended to other parent HNs with multiple dimensions, which shows its diversity. Further, theoretical calculations demonstrate that Co3S4 (111)/MoS2 (001) exhibits a higher adhesion work, providing further evidence that MoS2 enables phase control in the HNs CE reactions, inducing the generation of novel Co3S4-MoS2 HNs. As a proof-of-concept application for crystal phase- and dimensionality-dependent of cobalt sulfide based HNs, the obtained Co3S4-MoS2 heteronanoplates (HNPls) show remarkable performance in hydrogen evolution reactions (HER) under alkaline media. This synthetic methodology provides a unique design strategy to control the crystal structure and fills the gap in the study of heterogeneous materials on CE reaction over phase engineering that are otherwise inaccessible.

Simulation of boost path and phase control method in supercritical CO2 pipeline commissioning process

CO2 pipeline can be applied to Enhanced Oil Recovery (EOR) projects and CO2 geological storage projects, and has high engineering application value. However, pipeline transportation of CO2 is a high-risk link in CO2 storage projects. The phase state commonly used to transport CO2 is a supercritical state with both gaseous and liquid characteristics, and there are also great challenges in the field of pipeline transportation. The existing researches have carried out a lot of exploration and application development in the heat transfer, phase change, transient and special conditions of supercritical CO2 pipeline operation.In this paper, the modeling and exploration of the commissioning process before the formal operation of the supercritical CO2 pipeline are carried out, and the boost path of the supercritical CO2 pipeline in the phase diagram under different working conditions is obtained. The model developed in this paper is based on the sensitivity analysis of the effects of variables such as ground temperature, filling pressure speed, and whether to perform pressure-stabilizing leak detection operations. The step-up path in the phase diagram of the CO2 pipeline commissioning process and the adjustment control method are obtained. And the critical temperature of each working condition that cannot avoid phase transition, thus contributing to the existing knowledge system in this field.

Research on exoskeleton compliance control strategy based on dual interaction torque split phase control method.

Human gait pattern recognition and compliance control are key technologies for achieving high coordination and assistance between exoskeleton robots and human movements. In order to improve the adaptability of exoskeleton robots to the human body, this paper proposes an exoskeleton compliance control strategy based on dual interaction torque phase separation control method. A support phase swing phase split control strategy based on dual interaction torque is proposed. Utilize the interaction force of human joints and adopt a model-based method to control the support phase. By utilizing the interaction force of exoskeleton joints and using a torque closed-loop method to control the swing phase, a multi-state control method of motion is achieved. A lower limb exoskeleton knee joint testing platform is built to verify the proposed human gait recognition The effectiveness of human-machine interaction force identification and human-machine coupling system compliance control technology. The proposed control method can effectively adjust joint torque, enabling the exoskeleton robot to maintain balance and stability during the entire walking phase.

Optical-pulse-based reconfigurable phase control for independent beamforming and band fusion in a dual-band phased array receiver.

This Letter proposes an optical-pulse-based reconfigurable phase control method, enabling a dual-band phased array receiver to operate in two modes: dual-band-independent operation and dual-band fusion. The method utilizes optical pulses and optical delay to compensate for phase differences across frequency bands. An electrical phase shifter is employed to compensate for phase residual in both bands. All phase operations to both bands are processed concurrently in one link, thereby maintaining inter-band phase coherence. Experimental results verify the ability of dual-band-independent beamforming and inter-band phase coherence maintaining. A four-channel dual-band (X- and Ku-band) phased array antenna (PAA) receiver is constructed to measure PAA patterns and demonstrate band fusion. The pulse compression results in all directions reveal a doubled improvement in range resolution, which shows the potential for enhancement of radar performance.

High-precision frequency-controlled optical phase shifter with acousto-optic devices.

A fundamental parameter to determine how electromagnetic waves interfere is their relative phase, and achieving a fine control over it enables a wide range of interferometric applications. Existing phase control methods rely on modifying the optical path length either by changing the path followed by the light or by altering the thickness or index of refraction of an optical element in the setup. In this Letter, we present a novel, to the best of our knowledge, method, based on acousto-optic modulators (AOMs), which allows adjusting the phase by shifting the frequency of the light in a segment of its path. Since the amount of phase shift depends on the length of the segment, an optical fiber is used to realize a 2π shift. Two experimental implementations are described which deal with different sources of phase fluctuations. The first addresses fluctuations resulting from the optical fiber, while the second tackles unwanted variations originating from the AOMs.

Frequency tuning and automatic frequency tracking of shunted piezoelectric transducers

Piezoelectric ultrasonic transducers, vital in medical devices and aerospace, often face challenges like resonant frequency shifts and impedance variations affecting their operational efficiency. This paper introduces a shunted piezoelectric transducer which could tune itself by digitally programmable inductance. A transformer and inductance-capacitance matching network ensures enhanced compatibility and impedance management. Proposing a fuzzy PI-based phase control method achieves resonant frequency tracking, synchronizing operational frequency with the transducer. In contrast to traditional methods, our approach enables faster and more precise fine-tuning, detecting and rectifying real-world deviations for optimal performance. A comprehensive experimental validation, based on fundamental knowledge analysis, confirms the feasibility and superiority of our proposed method, and the commonly encountered issues of resonance frequency deviation and impedance variation in high-power piezoelectric transducer applications can be effectively mitigated.

Synthetic control with target sticking for on-orbit capturing using a dual-arm space robot

On-orbit capturing is a crucial step in the application of dual-arm space robots, aiming to accurately grasp a moving target and avoid damage to the arms terminal parts (i.e. the end effectors) due to contact force saturation. This paper presents a synthetic control method with target sticking for on-orbit capturing using a dual-arm space robot system from the approaching phase to pre-grasping phase. In the approaching phase, an online trajectory planning method based on visual servoing is proposed to obtain the desired trajectories for end effectors in work space. Then the joint torques are designed by the inverse kinematics and inverse dynamics to track the desired trajectories. Different from most of the current research, a new sticking phase is proposed after the approaching phase and before the pre-grasping phase. In the sticking phase, a force and motion control method is designed to maintain a close relative distance between end effectors and the target, which can avoid saturation of contact forces and avoid damage to the end effectors. In what follows, an impedance control method is proposed in the pre-grasping phase to absorb the impact energy and grasp the target accurately. The synthetic control strategy integrates the controllers of all the phases mentioned above. Automatic switching among the phases is realized by using logic judgment according to the system real states, which is more consistent with the real capturing environment. Finally, numerical simulation results demonstrate the effectiveness of the proposed synthetic control scheme. The results can be applied to the trajectory planning and control of on-orbit capturing, avoiding contact force saturation and ensuring the safety of the system.

The Phase Control of Transition Metallic Elements via Facile Chemical and Physical Syntheses.

The crystal phases of metals are important factors to tune the properties of metals, and therefore received extensive attention. Traditionally, phase control is performed within limited numbers of elements by harsh conditions, such as face-centered cubic Fe by high temperature. This review summarizes most reports in metal phase control area, including elements of Fe, Co, Ni, Cu, Ru, Pd, Rh, Os and Au. For every metallic element, the facile phase control methods are systematically introduced, such as epitaxial growth, ball milling, chemical reduction, etc. Their corresponding applications and the mechanisms for phase control are thoroughly discussed.

An Adaptive Synchronous Driving Phase Control Method of GaN-Based Full-Bridge 6.78-MHz WPTS

An Adaptive Synchronous Driving Phase Control Method of GaN-Based Full-Bridge 6.78-MHz WPTS

Minimum-Time Control for the Test Mass Release Phase of Drag-Free Spacecraft

The capture control of test mass by means of the electrostatic suspensions is crucial for drag-free spacecraft. The test mass must be released to the cage center of the inertial sensor accurately and quickly. This paper proposes a minimum-time capture control method for the test mass release phase of drag-free spacecraft. An analytical solution of optimal control is derived based on Pontryagin’s minimum principle and the linearized dynamics model of the test mass during the release phase. The parameters of the analytical solution are initially guessed with an approximate linear solution of the test mass dynamics model and are slightly modified by using differential correction. Compared with the exact numerical solution by the hp -adaptive pseudospectral method, the analytical solution is proved to be minimum-time. Numerical simulation shows that the proposed control method quickly captures the test mass to the cage center of the inertial sensor. The capture time to stabilization is only half that of the traditional controller.

Comments on “A Simple and Universal Phase Control Method for Designing Directional Couplers With Adjustable Phase Difference Slope and High Linearity”

In the above article (Pan et al., 2023), it is shown that the solution given for the –90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> directional coupler with adjustable phase difference slope is inadequate for equal power division purposes. The proposed solution results in a significant error between the two outputs of the coupler. Exact, correct solutions are derived for the coupler, which proves that the proposed solution in Pan et al. (2023) corresponds to the coupler for an unequal power division case rather than the equal power division.