Internal Coupling Research Articles

Research on coupling analysis and decoupling control of two-degree-of-freedom PTZ system

Abstract With the development of technology, especially in areas such as robotics, aerospace, photography, and videography, gimbal systems, as an important stabilization device, have been widely used. However, the two-degree-of-freedom gimbal system also faces a series of challenges in practical applications. Among them, one of the most critical issues is the internal coupling phenomenon in the system. The coupling phenomenon refers to the mutual influence and a constraint relationship between different degrees of freedom in the system, which may increase the complexity of the system’s dynamic characteristics and make the design and implementation of control strategies difficult. This study aims at explore more advanced and practical decoupling control strategies through in-depth analysis of the coupling characteristics of the two-degree-of-freedom gimbal system, providing new ideas and methods for the further optimization and application of the gimbal system.

Adaptive control for refrigeration via online identification

Vapor compression refrigeration systems (VCRS) occupy a crucial position in modern society and in the field of thermal sciences. However, the operation of VCRS is subjected to both external disturbances (dynamic-changing environment) and inherent system characteristics (coupling or nonlinear features), leading to issues like reduced refrigeration efficiency and significant fluctuations in cooling capacity. To address these challenges and enhance the adaptability of VCRS in dynamically changing environments, this study establishes a dynamic simulation model for VCRS based on the Switched Moving-Boundary method. The impact of external environmental disturbances on refrigeration performance is investigated, and continuous online identification methods are employed to elucidate its internal coupling characteristics and nonlinear features. The adaptive temperature control method is introduced, benefiting from the developed recursive least squares method with a forgetting factor for online identification, achieving precise model identification which facilities the real-time parameters tuning of adaptive controller. The results indicate that the hybrid paradigm of online identification and adaptive control algorithm not only effectively handles various disturbances but also reduces overshoot and IAE by 2-3 orders of magnitude compared to traditional PID controllers. Adaptive PID control maintains overshoot in the 10-4 order of magnitude and IAE in the 10-5 order of magnitude.

Spatio-temporal pattern and coordinated development of eco-compensation performance of 101 cities in the Yangtze River Economic Belt.

Eco-compensation is an important component of ecological civilization construction. Therefore, it is of great significance to elucidate the spatial and temporal pattern of eco-compensation performance and its internal coupling and coordinated features to promote ecological civilization construction. We proposed that eco-compensation performance consists of benefit and efficiency, and used the projection pursuit and super-efficiency SBM-DEA models to measure the eco-compensation benefit and efficiency of 101 cities in the Yangtze River Economic Belt from 2010 to 2021 and to analyze their spatial and temporal patterns. Finally, we used the coupling coordination degree model to reveal the coupling and coordinated features of eco-compensation performance. The results showed that the temporal trends of eco-compensation benefit and efficiency were "W" and "U" shaped. The eco-compensation benefit in eastern or mega-cities was the highest, whereas the eco-compensation efficiency in western or small/medium-sized cities was the highest. Coupling coordination degree of eco-compensation performance was in the coordinated development stage from 2010 to 2012, with a concentration of agglomeration effects in the central region. It was in the transition/adjustment stage from 2013 to 2020, with low-value areas concentrated and scattered high-value areas, and smaller regional differences. It was in the coordinated development stage in 2021, with a clear agglomeration effect in the eastern region. Cities in the Yangtze River Economic Belt should incorporate the eco-compensation performance coupling coordination mechanism into their optimized eco-compensation policy plans based on the stage of coordinated development, to achieve their environmental improvement goals.

Hybrid force-position coordinated control of a parallel mechanism with the number of redundant actuators equal to its DOF

To address the demands for precision and load-bearing capacity in the installation of building panels, a hybrid force-position driven robot with redundant actuation has been developed. The mechanical performance of this robot is primarily governed by its central parallel mechanism, which is equipped with redundant actuators matching the degrees of freedom. Non-redundant and redundant actuators are respectively responsible for position and force control. The inclusion of redundant force-driven joints has increased the internal coupling within the mechanism. To enhance the coordination between position and force control, a hybrid synchronized control method based on cross-coupling has been proposed. Initially, kinematic and dynamic models of the parallel structure were established. Under predefined trajectories, the theoretical inputs for each actuator were calculated using inverse kinematics and dynamics. Subsequently, employing the principle of cross-coupling, the torque output from the position actuators was used as feedback. This feedback was processed by a synchronized coordination controller to adjust the output force of the redundant force-driven joints. By adjusting the output force of the redundant actuators, the torque burden on the position actuators was effectively reduced, thereby enhancing the precision of position control. Additionally, under the same load conditions, smaller power actuators could be utilized for position control, reducing the overall weight of the robot and improving its load-to-weight ratio. To validate the effectiveness of the proposed control strategy, a robotic simulation environment was established. The simulation results demonstrated significant reductions in the average torque required by the position actuators across three different trajectories, with reductions of 91.43%, 54.56%, and 80.6% respectively. Finally, the load-bearing capacity and the load-to-weight ratio of the prototype were assessed. Experimental results confirmed that the prototype achieved a load-to-weight ratio of 15.83%, validating the effectiveness of the hybrid synchronized control method based on cross-coupling.

Control of a Multimode Double-Pendulum Overhead Crane System Using Input Shaping Controllers

This paper investigates the impact of higher derivative input shaping for minimizing both oscillations, namely hook and payload of a multimode double-pendulum overhead crane (MDPOC) system. The MDPOC has greater nonlinearities and stronger internal couplings, especially when involving two oscillation frequencies with multimode dynamic effects. With a suitable system’s natural frequency and damping ratio of the hook and payload oscillations, multimode zero-vibration (ZV-ZV), multimode zero-vibration derivative (ZVD-ZVD) and multimode zero-vibration derivative-derivative (ZVDD-ZVDD) shapers are successfully designed. More interestingly, two scenarios under a fixed cable length and a payload hoisting are considered which are closer to the real practical crane. Thus, an average travel length (ATL)-based shaper method is also considered to further verify the effectiveness and robustness of efficient hook and payload oscillation control under payload hoisting. All the multimode input shaping is simulated using the Matlab software. The simulation results of multimode ZVDD-ZVDD shaper successfully reduced in the overall hook and payload oscillations by 97.9% and 97.2%, respectively, compared to the unshaped system, whereas the multimode ATL-ZVDD shaper reduced hook and payload oscillations by 94.8% and 94.0%, respectively. In fact, the multimode ZVDD-ZVDD and multimode ATL-ZVDD shapers demonstrate the superiority in minimizing the hook and payload oscillations compared to the multimode ZV-ZV, multimode ZVD-ZVD, ATL-ZV and ATL-ZVD shapers. This significant reduction in oscillations enhances the precision and safety of real-world crane operations in industrial settings. It has been proven that considering the additional derivative of input shaping results in a higher level of hook and payload oscillations reduction.

Dynamical properties of a diffusion-coupled system of differential equations with an additional internal coupling

Dynamical properties of a diffusion-coupled system of differential equations with an additional internal coupling

Dual-Loop μ-Synthesis Direct Thrust Control for Turbofan Engines

As the power unit of an aircraft, the engine’s primary task is to provide the demanded thrust, making research on direct thrust control crucial. However, being a complicated multivariable system, effective multivariable direct thrust control methods are currently lacking. The main content of this paper is threefold. First, it presents a dual-loop multivariable μ-synthesis direct thrust control scheme for mixed-exhaust low-bypass turbofan engines, which is a typical rotationally symmetric machine. The scheme adjusts fuel flow for thrust control and nozzle area to control the turbine pressure ratio, ensuring thrust tracking while maintaining the engine’s key parameters within safe limits. Second, a fast, accurate thrust estimation algorithm based on aerodynamic thermodynamics and component characteristics is introduced. At last, considering the model uncertainties between off-design and design points, a weight function frequency shaping μ-synthesis control design method is proposed to address internal loop coupling and external disturbance suppression. Nonlinear simulations within the flight envelope show that μ-synthesis direct thrust control achieves robust servo tracking and disturbance rejection, with a maximum steady-state thrust error of no more than 0.1%, and the key parameters are not over their safety boundaries.

Assessing the impact of DIONISIO-SubChanFlow code coupling in nuclear fuel performance simulations

Realistic simulation of nuclear fuel performance requires not only validated models capable of describing the thermomechanical phenomena that take place within the fuel under irradiation conditions, but a detailed description of the thermal hydraulics of the channel surrounding the fuel rods, which provides the boundary conditions of the system. In this work, the main results and outlooks of coupling the thermal hydraulics code SubChanFlow with the fuel performance code DIONISIO are presented. To achieve this, an internal coupling was implemented, wherein DIONISIO is used as a master code controlling SubChanFlow as a thermal hydraulics subroutine replacing the simplified version already embedded in DIONISIO. Several tests were conducted to ensure the performance and quality of the coupling under normal operation conditions as a first approach. In addition, it was observed that the coupling demonstrated a significant improvement in the description of the cladding temperature and related variables, such as oxide thickness and hydrogen uptake, when compared with experimental data.

The photothermal coupling of TiN@Au core-shell nanorods applied to near-infrared photothermal therapy

Thermal plasmonic nanoparticles offer a novel and significant approach for photothermal therapy in the medical field, which is photothermal therapy of cancer. This study introduces a type of core-shell nanorods with internal coupling of titanium nitride (TiN) and gold (Au) nanomaterials. The photothermal properties of these nanorods in the near infrared (NIR) band were investigated using COMSOL Multiphysics software and the finite element method. Results indicate that TiN@Au and Au@TiN core-shell nanorods exhibit superior photothermal properties in the NIR band compared to pure TiN nanorods of similar volume. Furthermore, core-shell nanorods with polarization angles of 0° and 45° demonstrate enhanced optical absorption properties in the near infrared range. Furthermore, the study on the tunability of localized surface plasmon resonance with variations in core diameter, shell thickness, and combined changes of core diameter and shell thickness for core-shell nanorods of equal volume suggests that TiN@Au core-shell nanorods with a 10 nm Au shell offer increased optical absorption efficiency and photothermal conversion capability. Ultimately, the TiN and Au core-shell nanorods proposed in this research offer valuable insights for the structural design and heat transfer control of nanoparticle heat generators to enhance fluid temperature, as well as provide practical guidance for the preparation of core-shell nanoparticles.

Can the Water Resource Fee-to-Tax Reform Promote the “Three-Wheel Drive” of Corporate Green Energy-Saving Innovations? Quasi-Natural Experimental Evidence from China

The long-standing, unrestrained utilization of energy resources by China’s manufacturing sector has created irreversible obstacles to regional sustainable development. Consequently, the Chinese government has implemented a water resource tax policy in certain regions, with the aim of compelling manufacturing enterprises to adopt green and energy-saving innovations. This study used panel data from Chinese manufacturing companies listed on the A-share market from 2009 to 2020 and employed a double machine learning model to explore whether the water resource fee-to-tax reform can compel enterprises to enhance their tripartite green energy-saving innovation drive. These innovations consist of vision-driven and mission-driven green energy-saving technological innovations and green management energy-saving innovations. Following a quasi-natural experiment, our findings revealed the following: (1) The water resource fee-to-tax policy promoted the internal coupling coordination of the triple-driven system. (2) The policy compelled progress in mission-driven green energy-saving technological innovations and green energy-saving management innovations but hindered vision-driven green energy-saving technological innovations. (3) Within the internal systems of manufacturing enterprises, green energy-saving management innovations play a positive mediating role between the water resource fee-to-tax policy and the mission-driven green energy-saving technology innovation subsystem, but they lack a similar positive mediating mechanism for the vision-driven green energy-saving technology innovation subsystem. (4) The counterfactual framework verified that the mechanistic pathway “water resource fee-to-tax → green energy-saving management innovation → mission-driven/vision-driven green energy-saving technological innovation” could be further extended to other manufacturing enterprises not currently under policy compulsion. (5) In the interaction system between manufacturing enterprises and external markets, the development of marketization and financial technology positively regulated the promoting effect of the water resource fee-to-tax policy on mission-driven green energy-saving technological innovations and green energy-saving management innovations, but it did not have a similar effect on vision-driven green energy-saving technological innovations.

Hyper-graph matching D2D offloading scheme for enhanced computation and communication capacity

As the Internet of Things(IoT) and its intelligent applications continue to proliferate, forthcoming 6G networks will confront the dual challenge of heightened communication and computing capacity demands. To address this, D2D collaborative computing is being explored. However, the current D2D collaborative computing ignores the integrity of computing and communication. For a single-task device, offloading operations intertwine computing and communication, internal coupling causes due to parallel executed between local and D2D offloading. In addition, external coupling arises among devices competing for limited radio and computing resources. Worse, internal coupling and external coupling interact, exacerbating the situation. To address these challenges, a novel D2D offloading framework is proposed based on hyper-graph matching in this paper. Our goal is to minimize both delay and energy costs while ensuring service quality for all users by jointly optimizing task scheduling, offload policies and resource allocation. The original problem is formulated as a nonlinear integer programming problem. Then, by three-stage strategy optimization decomposition, it is separated into several sub-problems. In the first stage, a polynomial-time algorithm has been developed to optimize the task offloading ratio, taking into account both its upper and lower bounds. In the second stage, a geometric programming algorithm has been created to address power allocation. In the third stage, a three-dimensional hyper-graph matching model is employed to derive the optimal offloading and channel allocation policies. This is based on analyzing the conflict graph and applying the claw theorem. Simulation results demonstrate that the proposed scheme outperforms other algorithms by approximately 12%, 20%, 28%, 40%, respectively. Moreover, it enhances both spectral efficiency and computational efficiency.

Life cycle techno-economic-environmental optimization for capacity design and operation strategy of grid-connected building distributed multi-energy system

Distributed multi-energy systems (DMS) have received increasing attention. Many studies have optimized the capacity and operation strategies of DMS based on multiple objectives, but these studies must discuss the weights of different objectives and have not considered the internal coupling between different objectives. Besides, existing studies have not considered the changes in the actual value of environmental impacts. To address these shortcomings, this paper constructs a technology-economic-environmental optimization model by mixed-integer linear programming. Based on life-cycle assessment, the model quantifies the value of system life-cycle environmental impacts by introducing carbon price. The case results show that the proposed optimization model can reduce the total cost by 28.83 % and the life cycle environmental cost by 3.39 % compared to the traditional model. To reduce the strain on the grid, a new operation pattern (The grid provides fixed electricity to the system throughout the year.) is proposed. The electricity interaction of the system with the grid under the new operation pattern is more than 70 % lower than the system without electricity purchased quantity constraint. Sensitivity analysis shows the total system cost is more sensitive to natural gas and electricity price than carbon price. But carbon price volatility helps reduce system carbon emissions.

Aero-propulsion analysis of distributed ducted-fan propulsion based on lifting-line driven body-force model

As the environmental problems become increasingly serious, distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years. The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration. A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed. The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation. The lift and drag characteristics of the aero-propulsion coupling configuration are simulated. The results indicate that the coupling configuration has the most obvious lift augmentation at 12° angle of attack, which can provide an 11.11% increase in lift for the airfoil. At 0° angle of attack, the pressure difference on the lip parts provides the thrust component, which results in a lower drag coefficient. Additionally, the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated. For the two failure conditions, the lift of the coupling configuration is decreased significantly by 27.85% and 26.14% respectively, and the lip thrust is decreased by 70.74% and 56.48% respectively.

Durability of decisions explained by actor-strategies in games: A multiple case study analysis

Public decision-making contains several decisions taken by multiple actors intended to lead to collective gains. The impact of these decisions varies over time. This paper presents a novel approach to explain the durability, i.e., impact, of decisions in relation to strategies performed by actors involved in infrastructure development projects. The concept of durability is operationalised in terms of actors fulfilling joint aims and creating joint focus. We aim to explain why some decisions have a durable (lasting and joint focus) impact and why other decisions have a non-durable (temporary and no joint focus) impact. Actor-strategies performed in the decision-making process are used to explain the different types of decision impact. After analysing several Dutch Railway projects, we discovered that durable decisions appear when (i) obstructive non-deciding and non-cooperative strategies are dealt with, (ii) responsibilities are clearly divided, (iii) the scope alternates between internal and external focus and coupling of issues happens, and (iv) the design of the decision-making process is made explicit and information asymmetry is managed.

Tunable Photocarrier Dynamics in CuS Nanoflakes under Pressure Modulation.

Two-dimensional materials with a unique layered structure have attracted intense attention all around the world due to their extraordinary physical properties. Most importantly, the internal Coulomb coupling can be regulated, and thus electronic transition can be realized by manipulating the interlayer interaction effectively through adding external fields. At present, the properties of two-dimensional materials can be tuned through a variety of methods, such as adding pressure, strain, and electromagnetic fields. For optoelectronic applications, the lifetime of the photogenerated carriers is one of the most crucial parameters for the materials. Here, we demonstrate effective modulation of the optical band gap structure and photocarrier dynamics in CuS nanoflakes by applying hydrostatic pressure via a diamond anvil cell. The peak differential reflection signal shows a linear blueshift with the pressure, suggesting effective tuning of interlayer interaction inside CuS by pressure engineering. The results of transient absorption show that the photocarrier lifetime decreases significantly with pressure, suggesting that the dissociation process of the photogenerated carriers accelerates. It could be contributed to the phase transition or the decrease of the phonon vibration frequency caused by the pressure. Further, Raman spectra reveal the change of Cu-S and S-S bonds after adding pressure, indicating the possible occurrence of structural phase transition. Interestingly, all of the variation modes are reversible after releasing pressure. This work has provided an excellent sight to show the regulation of pressure on the photoelectric properties of CuS, exploring CuS to wider applications that can lead toward the realization of future excitonic and photoelectric devices modulated by high pressure.

Terahertz metal-graphene hybrid metamaterial for active manipulation of electromagnetically induced transparency

The dynamic tuning of terahertz (THz) electromagnetically induced transparency (EIT) offers significant potential in rapidly changing THz regulation fields, such as the next generation wireless communication, switching, and sensing. In this work, we demonstrate a THz EIT metamaterial by combining a circular and a rectangular split-ring resonator (CSRR and RSRR) based on the bright-bright mode coupling. The introduction of graphene into the EIT structure enables active tuning, and reveals two distinct regulation mechanisms in the metal-graphene hybrid EIT metamaterial: 1. the internal coupling effect diminishes with the increase of the Fermi level in the CSRR-graphene integration; 2. the surface electric field undergoes redistribution in the RSRR-graphene integration. These two dynamic regulation mechanisms are well confirmed by the simulated electric field distribution. As a result, the transmittance within the EIT window of the hybrid metamaterial can be precisely modulated, exhibiting a significant modulation depth of >85%. Notably, the integration with graphene in the RSRR allows for simultaneous modulation of resonances on either side of the EIT peaks, which expands more THz modulation channels. This work enriches the design and implementation methods for active THz EIT and shows potential applications in THz dynamic application scenarios.

Improving the output performance of magnetic energy harvesters through coupling beam

We propose a novel magnetic energy harvester (MEH) with multiple resonance modes. The MEH consists of low-frequency and high-frequency piezoelectric cantilevers connected by a coupling beam. Theoretical modeling, simulation, and experiments were conducted to validate the multiple resonance phenomenon. The results from these investigations are consistent with each other. It is evident that the internal coupling (IC) effect resulting from the coupling beam facilitates significant voltage outputs from both cantilevers at their respective resonant frequencies, i.e. the low-frequency beam (LFB) resonates at the resonant frequency of the high-frequency beam (HFB), resulting in a remarkable 122% increase in the output voltage. Conversely, the HFB resonates at the resonant frequency of the LFB, leading to an astounding 1200% increase in the output voltage. As a result of the IC phenomenon, the operating frequency bandwidth for harvesting an output voltage of more than 1 V in the LFB has been extended by 35.3%, while that of the HFB for capturing an output voltage of more than 0.5 V has been extended by 62.5%. Additionally, the coupling effect significantly enhances the power output of the MEH.

The passive biomechanics of the thumb carpometacarpal joint: An in vitro study

The thumb carpometacarpal (CMC) joint facilitates multidirectional motion of the thumb and affords prehensile power and precision. Traditional methods of quantifying thumb CMC kinematics have been largely limited to range-of-motion (ROM) measurements in 4 orthogonal primary directions (flexion, extension, abduction, adduction) due to difficulties in capturing multidirectional thumb motion. However, important functional motions (e.g., opposition) consist of combinations of these primary directions, as well as coupled rotations (internal and external rotation) and translations. Our goal was to present a method of quantifying the multidirectional in vitro biomechanics of the thumb CMC joint in 6 degrees-of-freedom. A robotic musculoskeletal simulation system was used to manipulate CMC joints of 10 healthy specimens according to specimen-specific joint coordinate systems calculated from computed tomography bone models. To determine ROM and stiffness (K), the first metacarpal (MC1) was rotated with respect to the trapezium (TPM) to a terminal torque of 1 Nm in the four primary directions and in 20 combinations of these primary directions. ROM and K were also determined in internal and external rotation. We found multidirectional ROM was greatest and K least in directions oblique to the primary directions. We also found external rotation coupling with adduction-flexion and abduction-extension and internal rotation coupling with abduction-flexion and adduction-extension. Additionally, the translation of the proximal MC1 was predominantly radial during adduction and predominantly ulnar during abduction. The findings of this study aid in understanding thumb CMC joint mechanics and contextualize pathological changes for future treatment improvement.

Characterization and mechanism of multi-scale pore changes in scCO2-water injection into different porosity coal specimen

The process of supercritical CO2 (scCO2) injection into the coal body induces inhomogeneous changes in pore, which has a significant effect mechanical changes of the geological storage of CO2 coal seams. In this study, the effect of scCO2-water intrusion on coal samples with different porosity was investigated by NMR equipment and the change in the mechanical properties were tested by uniaxial compression and acoustic emission techniques after treatment. Results showed that during the treatment of scCO2-water, the pores of different scales showed an exponential change trend of y = a·xb, with the macropore of low-porosity coal samples continuously increasing and the macropore of high-porosity coal samples continuously decreasing. The pore changes after treatment mainly occurred in the micropore range, and the changes of low-porosity coal samples were more than 6%, while the changes of high-porosity coal samples were less than 2.3%. The changes in the fractal dimension of low-porosity coal samples exceeded those observed in high-porosity. The geochemical impact, effective stress of scCO2-water mixed fluid, and the adsorption and expansion mechanism of matrix macromolecules are influenced by varying porosity. This study helps to understand the internal multi-scale pore coupling mechanism and the effect on the coal mechanical properties after CO2 injection.

Phosphorus starvation response genes and function coupling: A mechanism to regulate phosphorus availability in a subtropical estuary

Phosphorus (P) plays an important role in regulating primary production in estuarine environments. However, knowledge of the P-functional gene composition of microbial communities and the mechanisms of microbial adaptation to changes in available P in estuaries remain limited. This study coupling 16 s rDNA and metagenomics sequencing was conducted to reveal the relationship between P cycling functional genes, microbial interactions, and P availability in the Jiulong River Estuary. The results showed that the relative abundance of P cycling functions genes was highest in winter, and lowest in summer. Spatially, the total relative abundance of P cycling functions genes was higher in the riverward than that in the seaward. P cycling functional microbial interactions and P cycling gene coupling were strongest in summer and in the seaward. Changes in both temperature and salinity had significant direct and indirect effects on P cycling function, and the influence of salinity on P cycling function was greater than that on the microbial community in the estuary. Salinity had significant direct negative effects on inorganic P-solubilization (IP), organic P-mineralization (OP), and P uptake and transport functions (PT). Whereas, salinity had a significant positive effect on P-starvation response regulation (PR) function. Thus, salinity and microbial communities regulate the soluble reactive phosphate concentrations in estuarine environments by strengthening internal coupling among P cycling functions, promoting PR function, and facilitating PT gene expression. PR is the most important predictors, PR, PT, and PR-PT together explained 38.56 % of the overall soluble reactive phosphorus (SRP) variation. Over 66 % of the explained SRP variations can be predicted by the PR, PT, and PR-PT functional genes. This finding improves the knowledge base of the microbial processes for P cycling and provides a foundation for eutrophication management strategies in the estuary.