Response Characteristics Of System Research Articles

Water Level Control in Coupled Tank System with PLC and IoT-Based PID Method

There are many advanced technological discoveries in industry, including the coupled tank. Coupled tanks are several tanks connected to each other. One of the quantities that is often controlled in the industry is the control of water levels. Water level control in a PLC and IoT-based coupled tank system is a medium for controlling and monitoring water levels remotely in real-time. The sensor used is a Differential Pressure Transmitter (DPT) with a pump motor actuator which is connected to an Omron PLC using an inverter. There is a disturbance in the form of setting the control valve opening. The control method used is the PID method with Ziegler-Nichols tuning and trial and error. Both methods analyzed which performance of the system response characteristics was better. It is proven that PID tuning is suitable for water level control of coupled tank systems.

A piezoelectric cantilever-beam-spring-pendulum oscillator for multi-directional vibration energy harvesting

Harvesting energy from environmental vibrations holds significance for powering wireless sensors and transducers. However, the current vibration energy harvesting methods still have room for improvement, especially in the field of low-frequency vibration, where the performance of output voltage is relatively insufficient. This paper proposes a novel piezoelectric energy harvester consisting of a piezoelectric cantilever beam and a spring pendulum in order to address this challenge. Under external excitation, energy exchange is generated between the internal parts of the system, so that the swinging of the pendulum is interchanged with the extension and contraction motion of the spring and the bending motion of the cantilever beam to realize multidirectional energy harvesting. Firstly, the energy equation of system is obtained and the dynamics model of system is derived based on Lagrange's theorem. In addition, the response characteristics of system under harmonic excitation and the effects of different parameters on the system performance are investigated by simulation. With proper parameter selection, the system can produce higher output voltages. Compared to a piezoelectric cantilever-single-pendulum, the proposed structure demonstrates superior performance, especially in low-frequency vibration. The maximum voltage amplitudes in the x- and z-directions were 106.6% and 187.3% of those of the piezoelectric cantilever-single-pendulum, respectively. This paper proves the superior energy harvesting performance of the proposed structure.

Research on Simulation and Power Regulation Control Strategy of Fengning Variable-Speed Pumped Storage Unit

Abstract Variable-speed pumped storage unit demonstrates rapid power response and flexible adjustment of unit speed, significantly enhancing unit operational efficiency and the power system’s stability. This paper focuses on simulating the control strategy of the Fengning variable-speed pumped storage unit. First, the water pump/turbine and motor models are established based on the relevant parameters of the Fengning variable-speed pumped storage unit. Second, according to the distinct responsibilities of the governor and the excitation system, the control strategies of the unit in the power priority mode and speed priority mode are designed. Finally, we compare and analyze the power response characteristics of a single-machine infinite bus system under various operating conditions and control strategies. We also summarize the applicable scope and existing problems under different operating conditions.

Effects of clearances on dynamic response and nonlinear characteristics of the planar multibody mechanical system

Effects of clearances on dynamic response and nonlinear characteristics of the planar multibody mechanical system

Hydrodynamic characteristics of coral nursery buoyancy system and prediction using machine learning methods under wave action

The buoyancy system is a critical structure that ensures the safety and stability of the floating coral nursery and reduces the rate of coral shedding. Firstly, experiments in a wave tank were conducted on the motion response characteristics of the buoyancy system with four different structural types and submerged states, using the buoyancy system as the experiment object. The experimental results showed that the submerged state of the floating sphere was an essential element in affecting the hydrodynamic characteristics of the buoyancy system. The variation trends of the maximum oscillating tension of mooring cable with increase in period, and of the floating sphere motion amplitude with increase in Kc number under different submerged states were significantly different. Subject to experiment conditions, it was hard to judge the change tendency of the floating sphere motion amplitude under the large Kc number. Machine learning models trained through experiment data samples can quickly and accurately predict physical phenomena over a broader parameter range. Secondly, the prediction results of various machine learning models were compared and analyzed. Then the traditional machine learning model was optimized based on the particle swarm algorithm, which can improve the accuracy by about 20%. Finally, the optimal PSO-RBF model was employed to predict the floating sphere motion amplitude under the large Kc number. The predicted results showed that Kc = 6 was the demarcation point where the motion amplitude of the floating sphere varies with the Kc number. In addition, the fully submerged single floating sphere of buoyancy system is the best choice for floating coral nurseries under the four experiment cases in this paper, which can effectively reduce the damage of extreme waves with large wave heights and periods to floating coral nurseries.

Numerical modeling and dynamic response analysis of an integrated semi-submersible floating wind and aquaculture system

Floating wind turbines (FWT) are facing the challenges of high cost of energy. Integrating floating wind with offshore aquaculture cages presents a mutually beneficial approach to address cost concerns and maximize overall benefits. This study introduces and numerically models an integrated system, encompassing a self-designed semi-submersible FWT coupled and an aquaculture cage (FWT + AC). Comprehensive, fully coupled aero-hydro-servo-elastic-mooring models for this integrated system are established. Subsequently, the numerical model of the FWT is validated against wave basin model tests. The research further discusses the coupled dynamic response characteristics of the integrated system for both the FWT with and without the aquaculture cage. The results highlight that integrating aquaculture cages leads to an increase in the mean surge response by up to 12.6%, while significantly reducing pitch motion by as much as 7.69% under combined wind, wave, and current conditions. Moreover, the mean mooring loads, particularly for line 4 which faces the direction of wind, wave, and current, do not exhibit an increase of more than 15%. This integration not only enhances the stability of wind power generation under different wind degree, but also minimally impacts the average power generation efficiency, showing a variation of only about 2% under rated wind speed. The findings provide beneficial theoretical support for the design of the integrated FWT + AC system, demonstrating the potential of such integrated systems in promoting offshore sustainable development and enhancing wind energy utilization efficiency.

High-temperature molten salt circulating cold salt pump shaft system prestress response analysis research

To investigate the response characteristics of the rotor system in a high-temperature molten salt pump, a specific model of a cold salt pump was selected as the research object. The natural frequencies and mode shapes, critical speeds, and harmonic response analysis based on modal analysis of the rotor system with and without prestress were computed. The results indicate that with prestress, the natural frequencies of the rotor are higher compared to the rotor without prestress, and there is no clear pattern among the various vibration modes. The calculated critical speed for the second mode is much higher than the rotor’s operating speed. This suggests that the rotor system will not experience resonance at its operating speed, meeting design requirements and ensuring stable operation. When the rotor of the cold salt pump is subjected to unbalanced forces, vibrations occur in the x, y, and z directions. The region with the largest vibration amplitude is located at the fifth-stage impeller. At a frequency of 52 Hz, the corresponding harmonic response displacement reaches its maximum value, and this frequency remains unchanged with variations in the magnitude and position of the unbalanced force. Therefore, it is advisable to avoid operating the rotor system at the critical speeds corresponding to the first and second modes. Furthermore, the operating speed of the rotor system is much lower than the critical speeds corresponding to the first and second modes, so axial unbalanced forces generally do not affect the normal operation of the rotor system.

Optimized PID and NN-based Speed Control of a Load-coupled DC Motor

In this work, three control strategies are presented, compared, and discussed, applied on a load-coupled DC motor. The purpose is to control in an optimal way the motor speed in terms of the armature voltage. Two strategies are based on PID control, working on the classical PID controller and the optimized one by using particle swarm optimization (PSO) to tune the PID controller parameters. The other strategy is based on neural networks (NNs) where two NNs are built to model and control the system. Based on the results, all the strategies reach excellent performances, however, in terms of system response characteristics like rising time or settling time the PID-based controllers show faster responses than the NN controller. Moreover, by comparing these results with other studies that are working with an unloaded DC motor and even when the working system is more complex, the obtained results have a better performance.

Research on Vibration Characteristics of a Flexible Vehicle-Ladder Track System

As a means of vibration reduction, the ladder track has seen broad implementation in urban rail transit. However, issues such as increased vibration noise, rail corrugation, and fastener failure have been observed in certain sections of the ladder track during later operation. To investigate the mechanisms behind these phenomena and provide comprehensive insights into the system's response to various operational conditions, this study employed vehicle-track coupled dynamic theory to establish a three-dimensional finite element model of the flexible vehicle-ladder track system. The vibration transmission and dynamic response characteristics of the vehicle-ladder track system were analyzed. The findings revealed that the vehicle-track resonance and anti-resonance phenomena were more prominent in the medium- to low-frequency range. At specific frequencies, the wheelset exhibited various vibration modes, and the fastener force was found to closely correlate with the ladder vibration mode. Furthermore, the influence of speed on diverse components of the vehicle-ladder track system, in terms of maximum vibration and the dominant vibration frequency range, differed considerably. This study provides a more comprehensive and reasonable exploration of the modeling and dynamic behavior of vehicle-ladder track systems.

Superconducting rotor drive method with integrated driving and alignment

The high-speed rotating superconducting rotor can be used as a high-precision inertial device to measure the angular position or angular velocity of the carrier. The mass eccentricity and spherical error of the superconducting rotor are the main error sources that affect the measurement accuracy. The more complex the structure of the superconducting rotor, the greater the mass eccentricity and spherical error caused by its production and assembly process are, and the lower the accuracy of its measurement of angular velocity. Based on this, in this work, an electromagnetic drive structure with a simple rotor structure is designed. And the torque generated by the stator on the superconducting rotor is studied through finite element method (FEM). The effects of the stator on vertical alignment and acceleration of the superconducting rotor are analyzed. Based on the research results of the superconducting rotor torque, a superconducting rotor drive method with integrated driving and vertical alignment is proposed, which achieves the driving and vertical alignment functions simultaneously through the stator coil, and corresponding stator control timing is designed. Finally, the torque distribution in the driving process of the proposed driving method is analyzed, and the driving effect is quantitatively analyzed based on the response characteristics of the stator system. The time for the superconducting rotor to be accelerated to 50 Hz under different conditions is calculated. The results show that the designed driving electromagnetic structure and the proposed integrated driving method of vertical alignment and driving can be used for vertical aligning and driving the superconducting rotor. The research results provide a reference for further optimizing the superconducting rotor structure and driving methods of superconducting rotors.

Electrical Contact Resistance Evolution and Interface Fretting Wear Characteristics of Conductor-Parallel Groove Clamp System Response to Breeze Vibration Environment

Electrical Contact Resistance Evolution and Interface Fretting Wear Characteristics of Conductor-Parallel Groove Clamp System Response to Breeze Vibration Environment

Research on vibration stability of a mirror bender system for synchrotron radiation.

This paper accurately predicts and quantifies the vibration response characteristics of a mirror bender system with the finite element simulation and experiment. The results show that the fundamental frequency of the roll angle vibration is 24.66Hz, and the fundamental frequency of the pitch angle vibrationis 116.21Hz. The overall error is within 11.15% in comparision with the first six natural frequencies obtained from experiments and simulations. The vertical support rod, being one of the weakest links in the overall structural stiffness, is a crucial factor limiting the increase in the natural frequency of the mirror system. Before and after the injection of cooling water, the pitch angle vibration was 123.63 and 199.04 nrad, respectively. An increase in the cooling water flow rate from 1 to 1.5 l/min has almost no effect on pitch angle vibrations. This study provides references and guidance for improving the stability of the mirror system.

Experimental study on multi-body coupling system for twin-barge hydraulic lifting shipwreck salvaging system

The twin-barge lifting method, applied in the overall salvaging scheme of ‘SEWOL’, is one of the main approaches for salvaging large-tonnage shipwrecks. A model experiment for the twin-barge lifting shipwreck salvaging system was conducted for three typical salvaging stages. Based on the experimental results, this study investigated the coupled dynamic response characteristics of the multi-body system consisting of the shipwreck and twin barges. The coupling effects between the multi-body system were discussed to understand the complex dynamic behaviour in twin-barge salvaging system, utilizing spectrum and statistical analysis. Additionally, this study considered the influence of the environment direction on the barge motion. It was revealed that the multi-body system exhibits significant shielding, which greatly affects the heave, roll, and pitch motions, particularly for beam and quarter seas. The maximum sling tension, including the case of single lifting sling broken, was also analysed to ensure safety under extreme conditions. Finally, it is advisable to perform salvage operations in head seas considering motion response amplitude, and to conduct the salvage in beam seas from the perspective of lifting slings safety. This study is of great significance for improving the safety of large-tonnage wreck salvage operations, promoting the development of research on multi-body system.

Analysis of electromechanical coupling modal and dynamic response characteristics of permanent magnet gear transmission system considering variable load condition

In order to study the influence of electromagnetic (EM) effect and load change on the modal characteristics and dynamic response of gear transmission system driven by permanent magnet synchronous motor (PMSM), a electromechanical coupling dynamic model is established. The composite air gap permeability coefficient is introduced, and the formula of permanent magnet flux linkage under the influence of space harmonic and cogging effect is derived. The variation laws of gear meshing stiffness and bearing support stiffness under the influence of load change are simulated and analyzed. The natural frequency and vibration modal under different load, flux linkage and PI controller gain are revealed. On this basis, the influence of EM effect and load change on the resonance domain is analyzed through frequency sweep analysis and time domain simulation. Results indicate that the 1st order natural frequency and resonance amplitude will increase with the load, and the influence of PMSM EM excitation will gradually dominate. The increase of the flux linkage and speed loop controller gain Kpω will reduce the 1st order natural frequency. When Kpω =123, a new mode appears, and there is a modal transition between the new mode and mode 1 when Kpω =161. The research results can provide theoretical guidance for improving the transmission performance and structure optimization design of the permanent magnet gear transmission system.

Desain dan Simulasi Model Predictive Control pada Sistem Pembagian Daya untuk Kendaraan Listrik Hibrida Fuel Cell – Baterai

This research examines the performance of implementing Model Predictive Control (MPC) in the energy management system of fuel cell – battery hybrid electric vehicles. Three parameter variations were carried out on the MPC controller, namely variations in the horizon value, objective function, and weighting in the objective function. In testing variations in the horizon value of the designed MPC controller, it shows that the higher the horizon value used, the SOC and the final SOC are faster and closer to the optimal SOC determined by compensating for higher hydrogen consumption. Testing of objective function variations shows that the objective function implemented on the MPC controller influences the system response characteristics. It was found in objective function testing that optimal use of fuel cell power produces fuel cell power output with a working efficiency range of 57% - 60% when compared to other objective functions that work in the efficiency range of 49.2% - 57%. Finally, in testing variations in weighting values, it was found that the higher the weighting of an expression in the objective function, the more the optimizer will penalize the expression so that the solver will minimize the expression in the optimization process. Therefore, the MPC controller parameter values ​​need to be paid attention to so that the response characteristics are in accordance with the design. which are desired. It should be noted that this research does not use a speed prediction model so it is assumed that the speed is known without any uncertainty.

Cooperative Adaptive Control of Multi-Parameter Based on Dual-Parallel Virtual Synchronous Generators System

Presently, conventional fixed parameters are applied in dual-parallel virtual synchronous generators (VSGs), resulting in poor frequency response characteristics. Therefore, a multi-parameter cooperative adaptive control strategy is proposed in this paper as a solution. The principle of the method is that when a frequency transient fluctuation occurs in the VSG, the frequency deviation and rate of frequency change are combined with the virtual inertia, damping coefficient, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> /ω droop coefficient to form an adaptive control system. A small-signal model of dual-parallel VSGs was built to analyse the impacts of the parameters on the stability of the system in each phase. The boundary conditions of the parameters such as virtual inertia, damping coefficient, P/ω droop coefficient and virtual inertia adjustment coefficient are further pinpointed to improve parameters' values. In the simulation results, the strategy put forward in this paper can increase the frequency and amplitude by 54.66% and the recovery time by 49.65% when the system is disturbed. The simulation and the StarSim experimental platform are verified that the strategy proposed in this paper can effectively optimize the frequency fluctuation response characteristics of the grid-connected VSG system in different cases, enhancing the dynamic performance and safety and stability of the system.

Development and validation of the lead-bismuth cooled reactor system code based on a fully implicit homogeneous flow model

The liquid lead-bismuth cooled fast reactor has been in a single-phase, low-pressure, and high-temperature state for a long time during operation. Considering the requirement of calculation efficiency for long-term transient accident calculation, based on a homogeneous hydrodynamic model, one-dimensional heat conduction model, coolant flow and heat transfer model, neutron kinetics model, coolant and material properties model, this study used the fully implicit difference scheme algorithm of the convection-diffusion term to solve the basic conservation equation, to develop the transient analysis program NUSOL-LMR 2.0 for the lead-bismuth fast reactor system. The steady-state and typical design basis accidents (including reactivity introduction, loss of flow caused by main pump idling, excessive cooling, and plant power outage accidents) for the ABR have been analyzed. The results are compared with the international system analysis software ATHENA. The results indicate that the developed program can stably, accurately, and efficiently predict the transient accident response and safety characteristics of the lead-bismuth fast reactor system.

Study on the constitutive model of NEPE propellant based on indentation creep

AbstractThe significance of the mechanical properties of solid propellant during the curing process lies in their contribution to stress‐strain calculations of viscoelastic engineering materials and the analysis of structural integrity of solid rocket motor charges. In order to study the Constitutive equation of the nitrate ester plasticized polyether (NEPE) propellant during the curing process, indentation creep tests were carried out on the NEPE propellant, and the viscoelastic constitutive model of propellant with curing reaction at 50 °C and atmospheric pressure was studied. Firstly, based on the viscoelastic theory, the experimental principle of indentation creep test is deduced, and indentation creep tests are carried out for propellants with different curing degrees. Then, based on 2S2P1D (2 Springs, 2 Parabolic elements, 1 Dashpot) model and time‐temperature equivalence principle, the indentation test data are processed, and the complex modulus master curve of propellant with different curing degrees is established, and the influence of curing reaction on viscoelastic properties of propellant is analyzed, so as to better understand the response characteristics of propellant system during curing. The results show that the 2S2P1D model has a good fitting effect for the master curve in low frequency period, the fitting error is controlled within 10 %, and the correlation coefficients are all above 0.95. With the curing reaction, the complex modulus gradually increases, while the change rate gradually decreases. And it tends to be stable on the seventh day.

Electrohydraulic proportional position and pressure loading control utilizing a state perception and processing method

A new multifunctional proportional control triaxial stress loading apparatus is presented in this study, which can apply an output force on coal rock to simulate the conditions of triaxial stress loading, aiming at solving the problems of excessive consideration of static indices in the design and the incompleteness of the simulation and test verification system for the test parts at the performance analysis stage. This apparatus mainly combines the configuration of a triaxial stress loading system which can meet the stress loading requirements under different operating conditions, with the effective integration of multiple pressure loading operations based on the electrohydraulic proportional control method. In this context, a pressure and position combined control strategy based on the sliding mode is proposed to control the vertical and longitudinal loading hydraulic cylinders. Then, a co-simulation mode including the triaxial stress loading hydraulic system is established to verify the control strategy, system response characteristics and selection of the controller parameters. Furthermore, a multifunctional stress loading experimental platform is developed, and the stress loading characteristics with the proposed strategy are tested and analyzed. The results show that the triaxial stress loading hydraulic system can meet the response characteristics, the fluctuating deviation of the constant loading test can be restricted to 8.5%, the tracking error of the variable loading test is small, the minimum response time of instantaneous loading can reach 2.8 s, and the stress loading effect is noticeable. The experimental platform fully indicates that the stress loading system with the state perception and processing method as the core can meet a variety of verification indices of constant, variable and instantaneous loading tests. This research provides technical support for the smooth, synchronous control and intelligent operation of various types of hydraulic actuator machines.

Modeling geogrid-stabilized aggregate base courses considering local stiffness enhancement

Lateral restraint is the primary stabilization mechanism associated with the interlocking of aggregate particles in the geogrid apertures. This paper presents findings from a laboratory study which quantifies the local stiffness enhancement of aggregates through micromechanical interlocking provided by two different types of geogrids. These findings are applied to model the resilient response characteristics of geogrid-stabilized base course composite systems. Using three pairs of bender elements as shear wave transducers, horizontal stiffness profiles were determined above mid-heights of aggregate specimens. For two types of geogrids with square- and triangular-shaped apertures, the shear modulus profiles decreased moving away from the geogrid location. Based on a relationship for aggregates, resilient modulus was estimated from the shear modulus. Considering the variations in resilient moduli with distance from the geogrid location, the local stiffness enhancements provided by the two geogrid types were assigned to modulus profiles of a geogrid-stabilized aggregate base course in flexible pavement mechanistic analysis and modeling. The modeling results demonstrate the effect of geogrid base stabilization on the computed pavement resilient responses for both geogrid types. The sublayering approach which properly considers modeling of the geogrid influence zone could be effectively used in mechanistic analysis of a geogrid-stabilized pavement system.