Dynamic System Model Research Articles

A variable-thickness-arch based nonlinear vibration absorber for rotor-bearing systems

There are complex nonlinear vibrations in rotating machinery and their suppression is essential. This study aims to design a nonlinear vibration absorber to suppress the nonlinear vibration of rotor-bearing systems. The nonlinear vibration absorber is composed of a mass ring and circumferentially arranged multiple variable thickness arches mounted on the rotor and rotated synchronously. The absorber provides the nonlinear stiffness through the bending deformation of the arches under concentrated loads and the nonlinear stiffness is adjustable by designing variable thickness in the arches. The dynamic model of a rotor-bearing system coupled with the nonlinear vibration absorber is established. An efficient Galerkin averaging incremental harmonic balance (EGA-IHB) method is developed to analyze the vibration reduction performance of the absorber. The results indicate that the centrifugal force produced by the rotation of the absorber provides negative stiffness depends on the mass and the rotational speed of the absorber. When the absorber has a linear stiffness near the negative stiffness, the absorber demonstrates outstanding capability in suppressing the nonlinear vibrations of rotor-bearing systems. The absorber effectively suppresses both the primary resonance and harmonic resonance of the rotor system. The analysis demonstrated detailed the effects of the absorber parameters on vibration reduction. Increasing absorber damping can decrease both the primary resonance and harmonic resonance of the rotor system slightly. Appropriately increasing the absorber mass and reducing the cubic nonlinear stiffness can enhance the absorber performance in reducing primary resonance vibrations without affecting the vibration characteristics of the rotor system.

Feasibility Model Of Controlled Atmosphere Storage Implementation For Shallot Farmers In West Java

Smart postharvest technology in the form of Controlled Atmosphere Storage (CAS) is needed to increase the shelf life of shallot. However, the application of CAS requires high investment costs related to the initial setup such as land, warehouse, CAS, and CAS supporting equipment. Thus, it is necessary to analyze the benefits and costs for farmers' welfare reflected by adding the amount of farming margin and income from other sources considering the time adjustment. This study aims to build a dynamic model for the application of CAS technology in shallot farming and evaluate its costs and benefits for farmers' welfare. The method used is the integration of cost and benefit analysis into a dynamic system model. The results showed that shallot farmers’ income is very sensitive to price changes and increasing storage costs. Hence, adopting CAS technology could mitigate some of these effects by reducing post-harvest losses and allowing farmers to store their production in favorable situations. Moreover, the CAS model showed that in the management level, CAS could be feasible (in terms of NPV, IRR, and Net B/C), if the storage cost is at least IDR 2.000/kg. According to the minimum profit limit for farmers, the maximum storage cost is IDR 1.500/kg, which makes the CAS unfeasible to run. The successful adoption of CAS is contingent upon substantial financial support from both private-sector investors and government entities. Therefore, the CAS technology is more appropriate for adoption by stakeholders in the food industry who require a consistent year-round supply of shallots.

The Effect of Support Misalignment on Vibration Characteristics of Aero-Engine Rotor Systems under Ultra-High Operating Speeds

In order to ensure the vibration safety of rotor systems in the next generation of aero-engines and reduce the impact of misalignment faults, the effect of support misalignment on the vibration characteristics of rotor systems under ultra-high operating speeds is investigated in this paper. Firstly, an analytical excitation model of the rotor systems under ultra-high operating speeds is established, considering the impact of the support misalignment. Then, based on the model of the misaligned combined support system, the dynamic model of the flexible discontinuous rotor support system with the support misalignment is presented. Subsequently, based on the established model, the effects of support parameters and support misalignment amounts on the vibration characteristics of the rotor support system are analyzed. Finally, experimental validation of the research findings is conducted. The research result shows that the support misalignment increases the vibration response of the rotor, reduces the vibration reduction efficiency of the combined support system, and consequently decreases the vibration safety of the rotor support system.

Contagion network, portfolio credit risk, and financial crisis

We develop a network-based nonlinear dynamical system model to study credit exposure risk at the portfolio level. This model captures the complex characteristics of contagion arising from the microstructural interdependencies among firms, especially looping effects. We find that when contagion features are not adequately modeled, portfolio credit risk is generally underestimated, but becomes overestimated during a crisis. This can partly explain the outbreak and subsequent intensification of a crisis such as the 2008 financial crisis. We also derive an expression for the portfolio loss of a regular network, which has implications for measurement and pricing of portfolio credit risk.

The Dynamic Behavior of a Stochastic SEIRM Model of COVID-19 with Standard Incidence Rate

This paper studies the dynamic behavior of a stochastic SEIRM model of COVID-19 with a standard incidence rate. The existence of global solutions for dynamic system models is proven by integrating stochastic process theory and the concept of stopping times, together with the contradiction method. Moreover, we construct appropriate Lyapunov functions to analyze system stability and apply Dynkin’s formula and Fatou’s lemma to handle stopping times and expectations of stochastic processes. Notably, the extinction study provides mathematical proof that under the given system dynamics, the total population does not grow indefinitely but tends to stabilize over time. The properties of the diffusion matrix are harnessed to guarantee the system’s stationary distribution. Conclusively, numerical simulations confirm the model’s extinction outcomes.

Analysis of the Development of Downstream Copper Industry in Indonesia to Obtain Maximum Added Value Using Dynamic Systems

This research aims to design a dynamic system model for the downstream copper processing industry. The secondary data obtained is data provided by the BKPM Strategic Investment Downstreaming Expert Team. Vensim software is used to simulate downstream development in the form of CLD and SFD from 2024 to 2045. The results of the value-added simulation resulted in an increase in the added value of copper cathode by 2.15 times, the added value of cathode slab by 1.62 times, the added value of copper billet by 1.65 times, the added value of copper bar &rods by 1.08 times, the added value of copper tube by 1.02 times, the added value of copper strip by 1.39 times, and the added value of copper wire by 1.58 times. After a sensitivity analysis of the selling price at CAGR and an increase in energy costs by 20%, there was a change in the average value-added margin, so that the increase in added value changed which resulted in an added value of copper cathode of 1.9 times, added value of cathode slab of 1.47 times, added value of copper billet of 1.49 times, added value of copper bar &rods of 1.26 times, added value of copper tube of 0.93 times, added value of copper strip of 0.98 times, and added value of copper wire of 1.44 times.

Dynamics for rigid–flexible coupled solar panel multibody system composed of composite laminated plates

Composite laminates are widely employed in the fabrication of solar panels in modern spacecraft engineering because of their superior durability, mechanical qualities, and cost-effectiveness. This research is dedicated to multibody system dynamics modeling of composite laminate solar panels, specifically the coupling system between the rigid main body and the flexible solar panels. In this study, the rigid body is modeled using the natural coordinate formulation (NCF), and for the flexible solar panel, the absolute nodal coordinate formulation (ANCF) with a 36-DOF reduced-order composite thin shell element is used to accurately capture the coupling effect of the solar panel under large motion and deformation. Compared to a 48-DOF fully parameterized thick plate element, this method efficiently avoids shear locking and improves numerical solution convergence efficiency. Based on the Kirchhoff theory and the constitutive relationship of composite laminates, a dynamic model of the multibody system is developed, taking into account the rigid-flexible coupling effect and the kinematic constraints. This work thoroughly discusses the dynamic behavior of solar panel deployment using a comparative analysis of numerical simulation and virtual prototype simulation, and the accuracy is verified. The findings indicate that the flexible characteristics and fiber orientation of composite laminates have a significant impact on the dynamic response of solar panels during deployment. Furthermore, the bang-bang attitude controller is designed, and the difference in dynamic response between the two modeling methods in controlled and uncontrolled states is studied, providing an important theoretical foundation and technical support for solar panel design and analysis.

‘Good Rain Nurtures Things Silently’: A Longitudinal Study of EFL Teacher Emotion and Identity Learning in Curriculum Reform

ABSTRACTIdentity serves as a valuable lens through which to investigate, understand and facilitate teacher learning during curriculum reform. Identity learning is the core process of educational change, with teacher emotion at the heart of professional learning processes. In this study, we traced the 1‐year journeys of four Chinese EFL teachers during a tertiary EFL curriculum reform that focused on ideological and political education. The Dynamic Systems Model of Role Identity was utilised to understand identity learning. By drawing on interviews, documents and observations, we collected rich data and analysed four types of identity learning along a continuum from fake learning to transformation, mediated by teacher emotion. A multiplicity of emotions acted as indicators and potential catalysts for identity learning. However, an overly demanding context might lead to a retrogressive identity learning trajectory. The integration of ideological and political education in foreign language education was also discussed.

Operational transfer path analysis for the fixed shaft gear transmission system based on the simulation and experiment

The Operational Transfer Path Analysis (OTPA) is widely used to analyze signal transfer paths in various fields, but its applications in gear transmission systems are limited. In this paper, the OTPA method is appropriately applied to the study of vibration signal transfer paths of fixed shaft gear transmission systems. Firstly, the dynamic model of a three-axis two-stage fixed-shaft gear transmission system is developed. This model takes into account factors such as the impact of dynamic center distance on backlash and provides a comprehensive analysis of time-varying meshing stiffness and forces. Experiments are conducted to verify the accuracy of the model. Subsequently, this paper delves into the OTPA process for solving the signal transfer coefficient matrix. It also derives the calculation method for computing the contribution of signal transfer paths, which provides a theoretical basis for establishing the evaluation mechanism of the signal transfer paths. Next, the gear transmission system’s signal transfer is analyzed based on the OTPA method, and the contribution of each path is computed. The dominant path is identified by ranking the contribution of these paths. Finally, the excitation experiment of a single signal transfer path reveals the essence of the signal transfer mechanism. This research contributes to a deeper understanding of signal transfer paths within gear transmission systems based on the OTPA method, it identifies the optimal distribution of sensor installation positions for fault signal diagnosis, paving the way for more effective fault detection and diagnosis in the gear transmission system.

Enhancing stability and position control of a constrained magnetic levitation system through optimal fractional-order PID controller

Magnetic levitation systems are complex and nonlinear, requiring sophisticated control methods to maintain the stability and position of the levitated object. This research presents an optimized fractional order PID (FOPID) control approach for position control of a freely-suspended ferromagnetic object. The dynamic system model is mathematically modeled in MATLAB using first-principle modeling and the grey box method. The FOPID controller has five degrees of freedom (DOFs) that allow for fine-tuning of the control gains and fractional orders, enabling the system to handle the nonlinearity inherent in the magnetic levitation system. The DOFs of FOPID and integer order PID controllers are optimized using the Artificial Bee Colony (ABC) algorithm and results are compared with state-of-the-art optimization methods. The results showed that the FOPID controller can effectively control the magnetic levitation system with constraints and outperforms other methods by up to 92.14% in terms of settling time with negligible steady-state error.

Nonlinear vibration characteristics of rotor-bearing system with disc-shaft insufficient interference and flexible coupling misalignment fault

Abstract For the traditional rotor system, the looseness fault caused by disc-shaft insufficient interference is always ignored. Aimed at the disc-shaft looseness caused by insufficient interference, a novel dynamic model of rotor-bearing system in the presence of coupling misalignment is established in this paper to make an investigation on the fault characteristics of disc-shaft looseness fault. Due to the nonlinearity of contact model between disc-shaft, the iterative solving of kinetic equations can be obtained by the combination of Newmark-β and Newton-Raphson methods. The vibration characteristics of the rotor-bearing system with and without the disc-shaft looseness caused by insufficient interference are compared and analyzed. The comparison results show that the slight collision between disc-shaft can be caused in the disc-shaft early looseness fault, and the beat vibration of system is appeared when the disc-shaft looseness become severe. Considering the effect of coupling misalignment, the vibration responses of system under different coupling misalignment are further discussed and parallel misalignment is proved to have a significant effect on the disc-shaft looseness. It is expected that the research results provide a useful reference for the identification and diagnosis of the looseness fault caused by disc-shaft insufficient interference.

National Dictionary Fund: New Opportunities and Prospects

On behalf of the President of the Russian Federation, we have started working on the creation of the National Dictionary Fund (NDF). NDF is a digital resource that contains electronically recorded data on the functioning of the norms of the Russian language from various dictionaries. The development of NDF is due to the need to create a single, complete body of scientific knowledge, reliable and objective information about the norms of the Russian language in their current state and historical dynamics in a certain era of its development, as well as the history of the vocabulary of the modern Russian literary language from the time of its appearance to the present day. The system of Russian dictionaries will be integrated into a single network operating in a continuous development mode and representing an interactive dynamic model of the lexical system of the modern Russian language. It is supposed to have open access to information through a convenient digital tool with simple navigation. The NDF will be equipped with linguistic markup and an online search system for necessary information. NDF will offer the user not only the opportunity to see the information from a particular dictionary, but will also provide an expertly developed tool for extracting various types of language information from dictionaries.

Dynamics and adaptive backstepping control of rotor-hybrid foil-magnetic bearings system

The hybrid foil-magnetic bearing (HFMB) is a contactless-type bearing composed of a foil bearing (FB) in the inner side and an active magnetic bearing (AMB) in the outer side. It has the advantages of low drag torque, high DN value (bearing inner diameter times rotating speed), and high supporting efficiency. However, significant subsynchronous vibration will degrade the stability of the rotor-HFMBs system, which is an obstacle to the industrial implementation of HFMBs. To control the rotor vibration, this paper presents a dynamic model of the rotor-HFMBs system with unknown parameters and the design of an adaptive backstepping controller (ABC) for it. The stability of the closed-loop system is established. Simulation results of the rotor-HFMBs system controlled by ABC are compared with the proportional-integral-derivative controller (PID), illustrating that the ABC is capable of eliminating rotor vibration, and it is more effective than the PID.

Analysis of the Effect of Quay Container Crane Available on Dwelling Time at Jakarta International Container Terminal

The efficiency of loading and unloading dwelling time at the port has been done a lot. The problem at PT JICT is that there has been a decrease in throughput for the last three years, this has an effect on operational performance. operational performance is a representation of the achievement of all targets, thus the company always aims to improve its operational performance. Another problem is that the terminal's operational equipment has begun to be obsolete, which hinders the loading and unloading operation time, the lack of operational equipment that supports the loading and unloading process. The operational equipment studied is the Quay Container Crane which is seen from the available condition. All of these problems will have an impact on dwelling time at PT JICT which can affect operational performance. This research is expected to provide recommendations to PT Jakarta International Container Terminal to prepare adequate operational equipment so that the resulting dwelling time is known. This research method uses a dynamic system model and validation test with behavior pattern test. The results of the dynamic system model validation obtained dwelling time between 2.79 - 4.56 days, mean error of 3% and standard deviation error of 11%. Maintenance of quay container cranes has an influence on unloading productivity which has an impact on dwelling time. Based on 60 data, the quay container crane available variable is seen based on quartile values consisting of quartile 1 (Q1), quartile 2 (Q2) and quartile 3 (Q3). In the quay container crane available variable, the dwelling time value in quartile one is 1.34 days, quartile two is 1.47 and quartile three is 1.51 and the dwelling time value in quartile one is 14 units, quartile two is 12 units and quartile three is 10 units.

An Oscillation Stability Analysis of a Direct-Driven Wind Power Grid-Connected System Considering Low Voltage Ride Though from an Energy Perspective

To solve the problem of the oscillation stability of direct-driven wind-powered grid-connected systems with a low-voltage crossing control, a method of oscillation stability analysis for these systems, based on interactive energy, is proposed in this paper. Firstly, a dynamic energy model of a direct-driven wind-powered grid-connected system is established, considering a low-voltage traverse control. Secondly, the energy is divided into four parts—the line parameter energy, current inner loop energy, PLL energy, and current inner loop–PLL interaction energy—and the conduction path of the energy during a low-voltage crossing is described. On this basis, the aperiodic components of each energy path are analyzed, the stability level of the system is quantified, the influence of the different control parameters on the interactive energy dissipation is deduced, the key interactive control links affecting the stability of the system are screened, and the influence rules of the parameters are expounded. Finally, a direct-driven wind-powered grid-connected system model is built on the Rt-lab platform, and it is verified by a simulation test. The results show that the interaction energy generated by the interaction of the current inner loop and phase-locked loop is a key factor affecting the stability of the direct-driven wind-powered grid-connected system. The simulation test parameters of the control group were adjusted as the current inner loop’s proportion parameter increased from 1.32 to 5.28, the current inner loop’s integral parameter increased from 4.48 to 6.42, the PLL’s proportion parameter decreased from 9.45 to 6.3, and the PLL’s integral parameter decreased from 50.25 to 40.2. Both the theoretical and experimental results show that increasing the current inner loop’s integral and proportion parameters can improve the stability level of the direct-driven wind-powered grid-connected system; reducing the phase-locked loop’s proportion and integral parameters can also improve the stability level of the grid-connected system.

Estimation of the clutch pressure basing on reduced order model of the hydraulic actuator system

The precise control of corresponding clutch pressures is essential to the gearshift quality of vehicle transmissions. The electro-hydraulic clutch-actuator system is widely utilized by vehicle transmissions because of the character of fast response and accurate pressure regulating capability. However, due to the structure of vehicle transmissions, pressure sensors are hard to be mounted to measure the clutch pressure during the shifting process directly. An observer method basing on the reduced order dynamic model of the hydraulic clutch actuator system and the Unscented Kalman Filter (UKF) method is proposed in this paper to ensure a stable and precise control of the clutch actuator system. The reduced order non-linear dynamic model of the clutch actuator system is established basing on the flow distribution character and coupling motion of the valve spool in the system. A state observer is proposed to estimate the clutch pressure online using the output pressure signal of the pressure control valve based on the UKF method. Simulations and experiments are carried out to verify the proposed clutch pressure observe method. The results reveal that the reduced order dynamic model can predict the pressure dynamics inside the hydraulic system accurately and the observer can ensure the estimate accuracy of clutch pressure during the shifting process.

Wheel loader seat damping control research based on ADRC

This paper proposes a new type of damped multi-mode switching damper based on a high-speed switching solenoid valve. The structural design of the damper is completed, and its working principle of realizing different damping modes is analyzed. A damping characteristic model of the damper is constructed, and the change rule of the damping characteristic of the multi-mode switching damper is analyzed. The seat suspension of a wheel loader is equipped with a damper that is controlled by a damping strategy. A 10-degree-of-freedom mixed-logic dynamic model of the seat suspension system is established using HYSDEL, and a multi-mode switching damper is employed. The weight coefficients are adjusted using a self-immunity control strategy, and the hybrid model predictive control method is used to complete the damping control strategy. Simulation results show that, compared with the fuzzy control strategy, the designed wheel loader seat suspension damping active disturbance rejection control (ADRC) strategy not only effectively reduces the root-mean-square (RMS) value of the driver’s vertical vibration acceleration up to more than 40% at different speeds and shock conditions, but also effectively reduces the driver’s vertical vibration acceleration. The ADRC strategy is a robust approach that achieves the desired control objective of the system.

Dynamic modeling and failure mechanism study of herringbone gear planetary transmission system for wind turbine under gear cracks

The herringbone gear planetary transmission system (HGPTS) is a common component in the gearbox of wind turbines. Studying the dynamic performance of gear systems is the key to improving their stability. To reveal the influence of cracks on the dynamic characteristics of the HGPTS, using slicing method, we explore the influence of different crack factors on the time-varying meshing stiffness (TVMS) of the system. A 55-degrees of freedom bending torsion axis pendulum dynamic model was constructed using the centralized mass parameter method; in the model, factors such as TVMS of cracks as well as receding groove and errors are considered. The Runge–Kutta method was used to solve the dynamics, and the evolution diagram of the vibration and load distribution characteristics of the system under crack changes was obtained. Vibration tests were conducted on the system studied in this work. The results show that under the influence of cracks, the TVMS of the external and internal meshing pairs of the system will decrease, and as the cracks intensify, the fluctuation of the TVMS will decrease. Cracks can lead to regular impact behavior in the system. A modulation sideband centered on the meshing frequency appears in the vibration response, and the vibration trajectory of the gears will also become disordered, at the same time, under the influence of cracks, there are significant excitation factors in the load-sharing characteristics of the system. As the cracks continue to intensify, the vibration of the system becomes increasingly evident, and the load-sharing characteristics show a trend of first decreasing and then increasing. The vibration test results are in good agreement with the theoretical predictions. The correctness of the established model is verified. The research results can provide reference for the reliability research of wind turbine HGPTS.

Fuzzy disturbance observer-based fuzzy swing suppression control of a ‘mooring-heavy lift crane-cargo’ coupled system

In this paper, an adaptive fuzzy disturbance observer (FDO)-based control is proposed for the swing suppression of the mooring-heavy lift crane (HLC)-cargo system in the presence of a wave disturbance. First, the dynamic model of the HLC system is determined by employing the Lagrangian method, and the wave force is modeled as an exosystem with unknown terms based on the Jonswap spectrum. Then, based on the HLC model and the wave force exosystem, an FDO is established to determine the wave disturbances, and a fuzzy approximator is developed to estimate the unknown terms. A novel disturbance estimation error observer is first developed to facilitate the parameter adaptive updating law. Subsequently, by augmenting the HLC system and disturbance estimation error system, an FDO-based fuzzy antiswing control method is proposed in terms of the linear matrix inequality technique to suppress the swing. The closed-loop system stability is examined by using the Lyapunov method. Finally, the effectiveness of the proposed method is validated by numerical simulation.

Research on Hybrid Logic Dynamic Model and Voltage Predictive Control of Photovoltaic Storage System

This paper investigates microgrid systems characterized by the coexistence of discrete events and continuous events, a typical hybrid system. By selecting the charging and discharging processes of the energy storage unit as logical variables, a mixed logical dynamic (MLD) model for the microgrid in islanded mode is established. Based on this model, model predictive control (MPC) theory is employed to optimize the energy management strategy, aiming to stabilize the DC bus voltage of the photovoltaic (PV) unit and minimize the switching frequency of the energy storage unit’s charging and discharging processes during system operation.