Analysis Of Dynamical Systems Research Articles

Solving differential‐algebraic equations in power system dynamic analysis with quantum computing

AbstractPower system dynamics are generally modeled by high dimensional nonlinear differential‐algebraic equations (DAEs) given a large number of components forming the network. These DAEs' complexity can grow exponentially due to the increasing penetration of distributed energy resources, whereas their computation time becomes sensitive due to the increasing interconnection of the power grid with other energy systems. This paper demonstrates the use of quantum computing algorithms to solve DAEs for power system dynamic analysis. We leverage a symbolic programming framework to equivalently convert the power system's DAEs into ordinary differential equations (ODEs) using index reduction methods and then encode their data into qubits using amplitude encoding. The system nonlinearity is captured by Hamiltonian simulation with truncated Taylor expansion so that state variables can be updated by a quantum linear equation solver. Our results show that quantum computing can solve the power system's DAEs accurately with a computational complexity polynomial in the logarithm of the system dimension. We also illustrate the use of recent advanced tools in scientific machine learning for implementing complex computing concepts, that is, Taylor expansion, DAEs/ODEs transformation, and quantum computing solver with abstract representation for power engineering applications.

Building agricultural potential: Utilization of former land use rights by spatial planning

Background: Areas that were once Cultivation Rights (HGU) in Manokwari Selatan District are the subject of this research. Residents must follow the Regional Spatial Plan (RTRW) to use the land. This study aims to identify the potential for land development and analyze the current spatial allocation and arrangement in the former HGU area. Methods: Using system dynamic analysis, the study combined qualitative and quantitative approaches through observations and interviews. Result: The results show that once HGU areas could be developed into plantations or agriculture. This finding is based on land capability evaluated by considering ecological factors and local wisdom. Land use policies should be tailored to the potential and availability of land in this context. To increase the use of agricultural and plantation land, crop types suitable for soil capability can be selected based on land suitability. This research emphasizes the effect of policies on Kampung Gedi Merah's population growth. Using strategies to suppress the population growth rate is expected to reduce land conversion that is not by the RTRW spatial pattern. In 2023, 904 lived in this area without indicating land conversion. One of the critical challenges identified is the projected 33% decrease in land availability by 2030. Therefore, its land use needs to remain cording to RTRW directives. This research also provides recommendations to the local government to develop the potential of this land further so that interference with community use and control can be avoided.

Anisotropic power-law inflation for models of non-canonical scalar fields non-minimally coupled to a two-form field

In this paper, we investigate the validity of the so-called cosmic no-hair conjecture in the framework of anisotropic inflation models of non-canonical scalar fields non-minimally coupled to a two-form field. In particular, we focus on two typical k-inflation and Dirac–Born–Infeld inflation models, in which we find a set of exact anisotropic power-law inflationary solutions. Interestingly, these solutions are shown to be stable and attractive during an inflationary phase using the dynamical system analysis. The obtained results indicate that the non-minimal coupling between the scalar and two-form fields acts as a non-trivial source of generating stable spatial anisotropies during the inflationary phase and therefore violates the prediction of the cosmic no-hair conjecture, even when the scalar field is of non-canonical forms. In connection with the Planck 2018 data, tensor-to-scalar ratios of these anisotropic solutions are investigated. As a result, it appears that the tensor-to-scalar ratio of the anisotropic power-law inflationary solution of k-inflation model turns out to be more highly consistent with the Planck 2018 data than that of Dirac-Born-Infeld model.

Fundamental Study on Force-Projecting Bilateral Control for Pneumatically Driven Follower Device

This paper proposes the application of force-projecting bilateral control to a master-follower teleoperation system with pneumatic drive on the follower side and evaluates its effectiveness. The proposed method directly projects the operating force on the master side to the driving force on the follower side, eliminating the need for both position control and external force detection on the follower side, thereby solving the problem of low rigidity and response delay of a pneumatic servo system and providing highly stable sensor-less force presentation against variable environments. In this study, dynamic response analyses of a 1-DOF master-follower system were performed by numerical simulation using a linear system model, followed by experimental verification by implementing an actual system with an external force estimator. The results showed that the proposed force-projecting bilateral control has significantly higher positioning rigidity and better force control stability than the conventional force-reflecting bilateral control. A theoretical consideration was also given using the equivalent transformation of force transfer functions to provide evidence of high stability.

Buckling and dynamic analysis of drill string system in horizontal wells

Buckling and dynamic analysis of drill string system in horizontal wells

A discrete adjoint gradient approach for equality and inequality constraints in dynamics

The optimization of multibody systems requires accurate and efficient methods for sensitivity analysis. The adjoint method is probably the most efficient way to analyze sensitivities, especially for optimization problems with numerous optimization variables. This paper discusses sensitivity analysis for dynamic systems in gradient-based optimization problems. A discrete adjoint gradient approach is presented to compute sensitivities of equality and inequality constraints in dynamic simulations. The constraints are combined with the dynamic system equations, and the sensitivities are computed straightforwardly by solving discrete adjoint algebraic equations. The computation of these discrete adjoint gradients can be easily adapted to deal with different time integrators. This paper demonstrates discrete adjoint gradients for two different time-integration schemes and highlights efficiency and easy applicability. The proposed approach is particularly suitable for problems involving large-scale models or high-dimensional optimization spaces, where the computational effort of computing gradients by finite differences can be enormous. Three examples are investigated to validate the proposed discrete adjoint gradient approach. The sensitivity analysis of an academic example discusses the role of discrete adjoint variables. The energy optimal control problem of a nonlinear spring pendulum is analyzed to discuss the efficiency of the proposed approach. In addition, a flexible multibody system is investigated in a combined optimal control and design optimization problem. The combined optimization provides the best possible mechanical structure regarding an optimal control problem within one optimization.

Dynamic reliability analysis of CNC lathe spindle-bearing system with thermal effect in radial runout

As one of the key components of computerized numerical control (CNC) lathes, the dynamic characteristics of spindle-bearing system has a vital influence on machining performance. Analyzing the kinematic error of spindle-bearing system is of great significance for investigating its radial runout and optimizing CNC lathe. The failure mode of CNC lathe spindle-bearing system with thermal effect is defined as the dynamic displacement of shaft end exceeds the allowable radial runout. Firstly, a dynamic model of system with thermal effect under random geometric parameters is presented to carry out the reliability analysis of radial runout. The stochastic perturbation method is applied to determine the first four moments of system dynamic displacement. Random variables and derivatives of system differential equations can be arranged into two-dimensional matrices used with Kronecker algebra. In addition, the reliability and its reliability sensitivity of system are obtained to study the influence of random parameters on the reliability of system. A CJK-6130 CNC lathe is used as a practical example of proposed model. Furthermore, the comparison between numerical calculation and Monte Carlo simulation is used to verify the proposed method. Eventually, the effects of mean values and variances of bearing random parameters on the radial runout are discussed.

A novel numerical methodology of solar power tower system for dynamic characteristics analysis and performance prediction

Solar power tower (SPT) system is a promising candidate to improve the flexibility of renewable energy power systems. Accurately predicting the dynamic performance of the SPT system is an important prerequisite for stabilizing or dispatching the system. To this end, an integrated transient model of an SPT system has been established, taking into account the dynamic behavior of all its subsystems, including concentration, thermal energy storage, and power cycle. System dynamic response characteristics are then explored under varying environmental and operational parameters. Then, a dual-time-scale hybrid method combining steady and transient models is proposed to predict system performances. Finally, based on predicted annual performances, the capacities of subsystems are optimized. The results indicate that the direct normal irradiance (DNI) and mass flow rate of molten salts and working fluids have substantial impact on the system. When the DNI and mass flow rate of molten salt vary by more than 30 %, the required adjustment time exceeds 280 s, potentially resulting in a significant reduction in output power. The proposed hybrid method allows for rapid and accurate forecasting of overall performance, reducing calculation time by 32 % while maintaining a low relative error compared with the complete transient model. Additionally, based on the annual performances predicted by the proposed calculation method, the solar multiple and thermal storage time are optimized to be 3.0 and 12.5 h, respectively, which have considered the system efficiency, stability, and cost of energy storage.

Dynamic analysis of slant cracked rotor system considering nonlinear oil film force.

In this paper, considering the combined effects of nonlinear oil film forces and cracks on the rotor-bearing system, the differential equations of motion with 4 degrees of freedom are established by Lagrangian method. Then, the Lundgren-Kutta method is used to solve them and the results of the model are compared with the experimental data. The study demonstrate that the cracked rotor-bearing system is relatively stable at subcritical speeds, mostly in the period-1 motion. But near 1/3 of the critical speed, there is an inner loop in its whirl orbit and a significant increase in the 2x frequency component. When the system speed rises to the region near 1/2 of the critical speed, though the bifurcation motion and a relatively high 2x frequency can be observed, there are no other reliable fault characteristics. The study proves that the rotor crack fault diagnosis method based on the whirl orbits is convincing for slant cracked rotors.

Retracted: Dynamic Modeling and Analysis of Micro-Video Teaching System Based on Cloud Computing in College English Teaching

Retracted: Dynamic Modeling and Analysis of Micro-Video Teaching System Based on Cloud Computing in College English Teaching

‘Adequate amount of data’‐driven system design theory: how far can we know/control/protect?

In contrast to the natural tendency of many researchers to focus on collecting as much data as possible, Assistant Professor Tomonori Sadamoto, from the Department of Mechanical Engineering and Intelligent Systems at the University of Electro-Communications in Japan, believes that the pursuit of big data is not always desirable. He is promoting a shift towards the acceptance of a “adequate amount of data”-driven system design theory. Sadamoto is concentrating on data-driven methodologies and their application in social systems. Through key international collaborations with colleagues at leading institutions, he is advancing his research. His work on data-driven methodologies focuses on interdisciplinary studies that combine machine learning and control theory. His more applied work primarily falls within the realm of smart grids. In his projects, he formulates his questions mathematically from the perspective of control theory. For instance, Sadamoto has developed a novel mathematical tool known as the VARX (vector autoregressive with exogenous input) framework, which facilitates the tractable analysis of dynamic systems. Using this new tool, he has developed data-dependent system identification analyses when only an “insufficient amount of data” is available. Furthermore, for the first time, Sadamoto was able to demonstrate that the informativeness of data in a certain class of dynamic output controller design is equivalent to the identification of the target system. His efforts are aimed at expanding the horizons of these novel control theories into the field of smart grids.

Design and performance of a novel magnetically induced penta-stable piezoelectric energy harvester

The magnetically induced multi-stable piezoelectric vibration energy harvesters have garnered significant attention due to their strong nonlinear characteristics, wide operating bandwidths, and high electromechanical energy conversion efficiency. However, a traditional penta-stable design typically requires four rectangular external magnets. The excessive number of structural parameters amplify complexities in system optimization, dynamic analysis, and prototype installation, impeding harvester manufacturing and application. This study presents a novel penta-stable harvester design that utilizes interaction forces among a rectangular magnet and two annular magnets, resulting in a simplified system requiring only two external magnets. This design approach streamlines system design, dynamic analysis, and prototype installation, providing a fresh perspective on magnetic penta-stable vibration energy harvester design. The magnetizing current method is employed to accurately determine the system’s magnetic field and magnetic force. Stability analysis indicates that the multi-stability of the harvester is influenced by both the vertical magnetic force and equivalent linear elastic force, which can be effectively controlled by adjusting the system’s components. Dynamic simulations conducted under Gaussian white noise excitation confirm the penta-stable behavior of the system, and the dynamic responses verify that a shallower potential well depth contributes to the system’s ability to attain a higher output voltage. Experimental validations closely align with simulation results, providing strong evidence for the accuracy of the study’s findings. Furthermore, a practical application experiment demonstrates the harvester’s capability to power a hygrothermograph, highlighting its potential for real-world energy harvesting applications.

Rub-impact dynamic analysis of a dual-rotor system with bolted joint structure: Theoretical and experimental investigations

Large gas turbines often utilize dual-rotor structures to improve efficiency. To facilitate manufacture and maintenance, the large rotor systems are typically constructed by connecting components made from different materials together through the bolted joint. In this work, a dynamic model of a dual-rotor system with bolted joint included in the high-pressure (HP) rotor is established based upon the finite element theory of Timoshenko beam element, as well as taking into account the bearing forces and fixed-point rubbing fault. To evaluate the influence of rubbing faults on the dynamic behavior of a dual-rotor system, this study analyzed the response characteristics of the rotor under the cases of the LP rotor and the HP rotor subjected to the rubbing fault, respectively. In order to further reveal the effect of bolted joint structure on the system response while rubbing fault occurs, piecewise linear bending stiffness is also considered in this study. The nonlinear vibration responses of the bolted joint dual rotor-bearing system are studied through numerical simulation. Effect of rotor–stator contact stiffness and the occurrence of rubbing faults at the low-pressure (LP) rotor and the HP rotor are investigated through frequency-amplitude curves, waterfall diagrams, time-domain responses, and bending stiffness of the bolted joint. The results indicate that the presence of rubbing faults, whether occurring at the LP rotor or the HP rotor, leads to a decrease in the critical speed. Furthermore, under a rubbing fault, the bending stiffness of the bolted joint enters the stiffness softening region earlier and exhibits a wider range, which is exacerbated with increased contact stiffness. This phenomenon is considered one of the main causes of system response instability. Finally, the experimental studies are carried out on a bolted joint dual-rotor test rig to validate the numerical simulation results.

Descriptive design structure matrices for improved system dynamics qualitative modeling

AbstractQualitative modeling approaches can be useful in system information collection, model analysis, and formal model development. This is difficult when the number of elements and their interactions in the system is large. System dynamicists need additional tools and methods to conceptually model these large tightly coupled systems. We propose and test the Descriptive Design Structure Matrix (DDSM) as a qualitative system dynamics modeling tool and approach for systems with many elements and more interactions that can reasonably be modeled individually using traditional system dynamics methods. A DDSM consists of four parallel and internally consistent matrices that describe system interactions with binary relations, nontechnical text, technical text, and literature support. By including and documenting system information in multiple forms, DDSMs facilitate multiple stages of system dynamics modeling, improve modeler communication with system participants and domain experts, and improve model rigor. DDSM construction is described. A case study of the 2014 flooding in Kashmir is used to illustrate and test a DDSM and its application. Due to their compact format, DDSMs provide a useful visual communication aid, intuitive reasoning tool, and foundation for formal system dynamics modeling and analysis. © 2024 The Authors. System Dynamics Review published by John Wiley & Sons Ltd on behalf of System Dynamics Society.

On the Stability of a 3DOF Vibrating System Close to Resonances

Abstract Purpose In the current work, the motion of a three degrees-of-freedom (DOF) dynamical system as a vibrating model is examined. The proposed system is of high importance in vibration engineering applications, such as the analysis of the control of flexible arm robotics, flexible arm vibrational motion as a dynamic system, pump compressors, transportation devices, rotor dynamics, shipboard cranes, and human or walking analysis robotics. Methods Lagrange's equations (LE) are used to derive the equations of motion of the controlling system. The analytic solutions (AS) are obtained utilizing the multiple-scales method (MSM) up to the third order. Results The framework for removing secular terms provides the requirements for the solvability of this problem. Various resonance scenarios are categorized and the modulation equations (ME) are constructed. To graphically demonstrate the beneficial impacts of the distinct parameters of the problem, the time histories (TH) of the approximate solutions as well as the resonance curves (RC) are depicted. The Runge-Kutta algorithm (RKA) is employed to obtain the numerical solutions (NS) of the regulating system. Conclusion A comparison of the AS and NS reveals the accuracy of the perturbation approach. The stability/instability zones are studied using Routh-Hurwitz criteria (RHC), and then they are examined using a steady-state situation. Basically, the used perturbation method is considered a traditional method that is applied to solve a new dynamical system. Then, the achieved results are considered new because they weren’t obtained previously, which indicates the novelty of this work.

Nonlinear Dynamic Analysis of a Spur Gear Pair System with Wear Considering the Meshing Position

In this paper, a nonlinear dynamic model of a parallel shaft gear system consisting of two involute spur gears is developed to investigate the coupling effect between the gradual surface wear of gear teeth over time and nonlinear dynamic characteristics. A uniform wear model that accounts for how the volumetric wear of the gear teeth affect their meshing position, backlash, and stiffness is proposed. Additionally, a nonlinear dynamic model with six degrees of freedom is described that considers friction, time-varying gear backlash, and time-varying meshing stiffness. The proposed model significantly changes the mesh stiffness, not only in terms of value but also in terms of contact ratio. Furthermore, the nonlinear dynamic characteristics of the gear system vary significantly. It is found that the gradual wear of gear teeth affects the meshing position and further has a significant impact on the nonlinear dynamic characteristics of the spur gear system. This paper provides a basis for studying the nonlinear dynamic characteristics of the spur gear system as it experiences the gradual wear of teeth over time.

Dynamical system analysis of cosmological evolution in the Aether scalar tensor theory

Dynamical system analysis of cosmological evolution in the Aether scalar tensor theory

A dynamical systems analysis of change in PTSD symptoms, depression symptoms, and suicidal ideation among military personnel during treatment for PTSD

ObjectiveThe connections among posttraumatic stress disorder (PTSD), depression, and suicidal ideation are elusive because of an overreliance on cross-sectional studies. In this secondary analysis of pooled data from three clinical trials of 742 military personnel, we examined the dynamic relationships among PTSD, depression, and suicidal ideation severity assessed repeatedly during and after outpatient treatment for PTSD. MethodsWe conducted dynamical systems analyses to explore the potential for coordinated change over time in psychotherapy for PTSD. ResultsOver the course of psychotherapy, PTSD, depression, and suicidal ideation severity changed in coordinated ways, consistent with an interdependent network. Results of eigenvalue decomposition analysis indicated the dominant change dynamic involved high stability and resistance to change but indicators of cycling were also observed, indicating participants “switched” between states that resisted change and states that promoted change. Depression (B = 0.48, SE = 0.11) and suicidal desire (B = 0.15, SE = 0.01) at a given assessment were associated with greater change in PTSD symptom severity at the next assessment. Suicidal desire (B = 0.001, SE < 0.001) at a given assessment was associated with greater change in depression symptom severity at the next assessment. Neither PTSD (B = −0.004, SE = 0.007) nor depression symptom severity (B = 0.000, SE = 0.001) was associated with subsequent change in suicidal ideation severity. ConclusionsIn a sample of treatment-seeking military personnel with PTSD, change in suicidal ideation and depression may precede change in PTSD symptoms but change in suicidal ideation was not preceded by change in PTSD or depression symptoms.

Application of dynamic accuracy evaluation for press systems based on orthogonal design method

The variation of dynamic accuracy for press systems is the nonlinear phenomenon that results from the consideration of contact and impact on the deformation of transmission mechanism, usually revolute joint and translation joint. The influence is especially obvious in the ultra-precision mechanism, which can cause the vibration and unstabitily of position and machining accuracy would be failure. As usual, the dynamic accuracy is used to evaluate the ability of press systems, which is also the important design object. Due to the stronger nonlinear of dynamic accuracy, especially for the effect of coupling factors, the mathematical analysis method plays an important role in the study of dynamic behavior for press systems. This work proposes the new approach to conduct the simplified dynamic accuracy analysis based on the orthogonal design method, which optimize the reasonability of sample collection. The proposed method is compared with the traditional approach, which illustrates the advantage and efficiency for the dynamic accuracy analysis of press systems.•Developed dynamic accuracy analysis is observed to be effective for the stability evaluation of press systems.•The simplified model of coupling effect analysis is established based on orthogonal design method.•No need to collect a large amount of data for comparison and the reliable nonlinear analysis is conducted with simplified model.

Investigation of Collision Damage Mechanisms and Reduction Methods for Pod Pepper

This study aims to address the current situation of the late start of mechanized harvesting technology for the pod pepper, the high damage rate of existing pod pepper harvesters, and the lack of theoretical support for key harvesting components. The Hertz theory is employed to investigate the damage mechanism of collisions between pod pepper and comb fingers. The study analyzes the maximum deformation of pod pepper and the critical speed at which damage occurs during the collision process. Furthermore, it explores the critical relative speed that leads to damage in pod pepper. Orthogonal tests are conducted to analyze the effects of rotational speed, hose thickness, and moisture content on the efficiency of pod pepper picking. The experimental results are then subjected to multifactorial ANOVA to identify the optimal test parameters. The structural and motion parameters of the picking device are optimized based on these conditions. It is determined that the critical relative velocity for damage to pod pepper during a collision with the comb finger is V0 = 11.487 m s−1. The collision velocities of pod pepper with different hose thicknesses are analyzed using the i-SPEED TR endoscopic high-speed dynamic analysis system to obtain the corresponding collision velocities for different hose thicknesses. The study finds that rotational speed, hose thickness, and the water content of pod pepper affect the damage rate and stem shedding rate. The optimal experimental parameters are determined to be a rotational speed of 705.04 rpm, hose thickness of 3 mm, and water content of the pepper of 71.27%.