Dynamic Performance Research Research Articles

Exponentially Synchronous Results for Delayed Neural Networks With Leakage Delay via Switched Delay Idea and AED-ADT Method.

Time delay has always been one of the main factors affecting the application performance of neural network (NN) systems, and dynamic performance research of NNs with time delays has been the focus of many scholars in recent years. This article enquires into the exponentially synchronous problem of switched delayed NNs with time delay in the leakage term. Adopting an unusual form from a common switched system, the switching modes of the switched delayed NNs system in this article are dependent on time delays. In the first place, the master, slave, and error NNs models are reconstructed into the switched form by introducing the switched delay idea. Then with the help of the admissible edge-dependent average dwell time (AED-ADT) method and delay-dependent switching adjustment indicators, a novel set of generalized delay-mode-dependent multiple Lyapunov-Krasovskii functionals (MLKFs) is built for analyzing the cases where a state-feedback controller exists and does not exist in the model, and where parts of LKFs may increase during the period when the corresponding subsystems are activated. For these cases, several effective exponential synchronization criteria and switching laws are presented accordingly. At last, the verification of the theoretical results is shown through a few examples.

Design and dynamic performance research of MR hydro-pneumatic spring based on multi-physics coupling model

Aiming at the problem that the damping coefficient of the traditional hydro-pneumatic spring cannot be adjusted in real-time, the magnetorheological (MR) damping technology was introduced into the traditional hydro-pneumatic spring with single gas chamber. A new shear-valve mode MR hydro-pneumatic spring was proposed. And its dynamic performance was analyzed based on multi-physical coupling simulation and mechanical property test. Firstly, a structural scheme of MR hydro-pneumatic suspension was proposed to ensure the original height adjustment function based on the working principle of traditional hydro-pneumatic suspension with single gas chamber. Secondly, based on the design requirements, the parameter of MR hydro-pneumatic spring damping structure was designed by using MR damper design method. Thirdly, the multi-physical coupling dynamic performance of the MR hydro-pneumatic spring damping structure was analyzed based on the electromagnetic field analysis theory, flow field analysis theory and thermal field analysis theory. The analysis results showed that the designed MR hydro-pneumatic spring has reasonable magnetic circuit structure and excellent working performance. Then, the mechanical properties of MR hydro-pneumatic spring were tested. The results showed that the maximum damping force can reach 20 kN, and the dynamic adjustable multiple can reach 6.4 times. It has good controllability and meets the design requirements. Finally, a nonlinear model of MR hydro-pneumatic spring was established based on the elastic force calculation model of the gas and the Bouc–Wen model. The simulation results of the established model agree well with the experimental results, which can accurately describe the dynamic properties of the hydro-pneumatic spring. The proposed design and modeling method of the MR hydro-pneumatic spring can provide a theoretical basis for the related vibration damping devices.

Extending the tire dynamic model range of operating conditions based on finite element method

Tire dynamics model is the basis of vehicle dynamic performance research, however, due to the limitation of safety and environmental conditions, the six-component physical test can not fully characterize the dynamic mechanical response characteristics of tire under special conditions such as low service inflation pressure, high load, and large range of operation temperature. To accurately describe the dynamic response of the tire under special operating conditions with the magic formula (MF) tire model, this paper combines the nonlinear finite element analysis and the experimental test. The finite element model of the tire is verified by the dynamic characteristic experiments, and the tire dynamics simulation under special operating conditions are also conducted based on the verification results. The MF tire model is modified and the parameter identification is performed for the prediction results to extend the operating conditions of the tire dynamic model. The results of the comparison show that the method proposed in this paper can realize the condition expansion of MF tire model under special conditions.

Design and Dynamic Performance Research of Underwater Inspection Robots

With the construction of a large number of power plants along the river and the coast, more and more power plants have adopted open water intake in the circulating water pool of the power plant and the number of underwater operations is increasing. In the detection of complex underwater environments, underwater robots have been widely used as a kind of underwater intelligent equipment. However, the current underwater robots generally have problems such as weak endurance, low intelligence, poor detection ability, and large environmental disturbance. The underwater robot designed in this paper is able to accomplish various rotational and flat movement works in the water and also can realize the monitoring of the water environment. In this paper, the underwater dynamic performance of the underwater robot is studied, the coordinate system and motion equation are established, the hydrodynamic analysis is carried out, and the dynamic characteristics of the underwater robot are tested. The experimental results show that the underwater robot has achieved good results in underwater motion control and its dynamic performance, showing the advantages of good robustness and accuracy, high control accuracy, and good dynamic characteristics.

Research on Dynamic Modeling of the Supercritical Carbon Dioxide Power Cycle

The supercritical carbon dioxide (SCO2) Brayton cycle, as a substitute for the steam cycle, can be widely used in a variety of power generation scenarios. However, most of the existing SCO2 cycle studies are restricted to basic thermodynamics research, parameter optimizations, system design in different application fields, and even economic analysis. Considering the load variability and control flexibility of the power generation system, the dynamic performance research of the SCO2 cycle is also crucial, but the work done is still limited. Based on the previous studies, Simulink software is used in this paper to develop a dynamic model of the 20 MW-SCO2 recompression cycle, which specifically includes component models that can independently realize physical functions and an overall closed-loop cycle model. A series of comparative calculation are carried out to verify the models and the results are very positive. The SCO2 recompression power system is built with the developed models and the dynamic model runs stably with a maximum error of 0.56%. Finally, the simulation of the dynamic switching conditions of the 20 MW-SCO2 recompression cycle are performed and the analysis results supply instructive suggestions for the system operation and control.

Modeling and dynamic performance research on proton exchange membrane fuel cell system with hydrogen cycle and dead-ended anode

In order to improve the response speed and output power of the system to ensure the safe and stable operation of the proton exchange membrane fuel cell system, it is necessary to control the gas supply system reasonably and effectively. In the present study, a system simulation model considering nitrogen crossover and water migration is established, which is in good agreement with the experimental results. By using this model, the pressure difference between the two sides of the membrane during purging was simulated, showing that the pressure difference was all less than 20 kPa. Increasing the pump speed is advantageous because hydrogen recovery increases the relative humidity of the anode inlet and avoids membrane drying of the anode inlet due to the lack of an external humidifier. When the anode recovery rate is at most 90%, the corresponding maximum relative humidity at the anode inlet is 0.45. When the humidity is constantly with the operating temperature at 60, 70 and 80°, the higher the operating temperature, the lower the output voltage. These results reveal that the hydrogen recirculation fuel cell system with dead-ended anode has good performance and the control strategy is effective.

Study on dynamic performance of SOFC

In order to solve the problem of real-time matching of load and fuel cell power, it is urgent to study the dynamic response process of SOFC in the case of load mutation. The mathematical model of SOFC is constructed, and its performance is simulated. The model consider the influence factors such as polarization effect, ohmic loss. It also takes the diffusion effect, thermal effect, energy exchange, mass conservation, momentum conservation. One dimensional dynamic mathematical model of SOFC is constructed by using distributed lumped parameter method. The simulation results show that the I-V characteristic curves are in good agreement with the experimental data, and the accuracy of the model is verified. The voltage response curve, power response curve and the efficiency curve are obtained by this way. It lays a solid foundation for the research of dynamic performance and optimal control in power generation system of high power fuel cell stack.

Study on Nonlinear Damping Properties of Hydro-Pneumatic Suspension System for XP302-Pneumatic Tyred Roller

The nonlinear stiffness and damping properties of the hydro-pneumatic suspension system are introduced, and the nonlinear mathematical model of it is established. Using MATLAB 2009b to establish the computer simulation program and draw out the nonlinear stiffness curve and damping properties curve of the hydro-pneumatic suspension system. Then, researching the influences of related parameters' changes on the nonlinear stiffness and damping properties of the hydro-pneumatic suspension system. The simulation of vehicle dynamic performance research's foundation is provided.

Ultra-small micro pressure sensor chip design and fabrication featuring high-sensitivity and good-linearity

Ultra-small micro pressure sensors are demanded in dynamic performance research of airplanes, missiles and other mechanical movements in aerodynamics. In this study, a novel two island-beam-diaphragm structural sensor chip is designed to improve the sensitivity and linearity simultaneously. Two islands are introduced into the back side of the chip to fulfill the requirement of stress concentration. The chip is fabricated with silicon micromachining technology and calibrated after packaging into a pressure sensor. The resulting sensors perform well. The sensitivity of the sensor is 1.60 mV/V/100 Pa, higher than the designed 1.48 mV/V/100 Pa. Nonlinearity values at 0.04 %FS and repeatability and hysteresis uncertainty value at 0.01 %FSO and 0.05 %FSO, respectively. The temperature coefficient of sensitivity and temperature coefficient of offset is ?0.93 × 10?3/°C FSO and 0.86 × 10?3/°C FSO. The accuracy is 0.04 %FSO. Extremely high over-pressure capability is achieved due to the small island for over-range protection.

Model Based Research of Dynamic Performance of Shaft-Bearing System in High-Speed Field

Dynamic performance of the high-speed running shaft-bearing system (SBS) is different from that of idle state system due to the high-speed effects (HSE), including shaft centrifugal force, gyroscopic moment, and nonlinear bearing operational stiffness. In this paper, aiming at improving the operation stability, dynamic performance of SBS operating in high-speed field is investigated based on a finite element (FE) dynamic model. Firstly, the Timoshenko beam elements are applied to develop the SBS FE model with full consideration of HSE. Secondly, idle state frequency response function at the front tip is obtained analytically and experimentally to validate that the FE model can illustrate the system dynamic behaviors in static condition. Finally, by substituting various rotational velocities into the FE model, the HSE on system natural frequencies are studied one by one as well as together. The results show that, when bearing is being extremely light preloaded, SBS frequencies are affected by the HSE of shaft more than bearing, especially where the gyroscopic moment effect of shaft is the most influential factor. Moreover, the nonmonotonic variation of bearing operational stiffness is analyzed. The “stiffen” phenomenon explained in this paper provides a more comprehensive understanding of the nonlinear bearing operational stiffness.

Research of Dynamic Performance of Reciprocating Compressor Valve

The main duty of this paper is dynamic performance research of reciprocating compressor value. By theoretical analysis, obtaining the movement rules curves of value plate and analyzing selection principle of value characteristics parameters; By mathematical simulation, expounding initial conditions and boundary conditions.

Dynamic Characteristics of Bridge under Moving Constant Load

It is very important to carry out research of dynamic performance and acquire data of bridge. it can provide reference for design of bridge. Combined with a bridge in actual engineering, this paper analyzes the deformation of bridge subjected to vehicles with different velocities. Based on typical theory on vibration analysis between bridge and vehicles and simplified model, finite element model of simple-supported bridge is established by ANSYS software, and concrete process of modeling, solving, analyzing and dealing is introduced. Through the numerical simulation analysis dynamic response characteristics of the bridge body are acquired when the vehicle passes through the bridge at different speeds, variable regularity is given for dynamic response and these can provide good reference for controlling the vibration measures of bridge under moving loads.

Study on Dynamic Test of a Large Span Steel Truss Pedestrian Bridge

To prevent a long-span steel truss pedestrian bridge vibration problem, finite element model was established by analysis software ANSYS, studies on this pedestrian bridge’s vibration question were carried on by frequent spectrum analysis based on recorded data and modal analysis. It has determined the vibrating level. In addition, the reason for this pedestrian bridge’s vibration has been thoroughly analyzed from the pedestrian and traffic, and had dynamic response analysis of pedestrian bridges under the crowd of pedestrians walking load. Then the main reason which causes the actual vibration characteristic has been found. Thus these both gave the reasonable explanation to the vertical vibration and provided the reference for the similar structure’s dynamic performance research.

Research of Dynamic Performance of Gear Shifting Process of Hydro-Mechanical Transmission Vehicle

The structure and working principle of main parts of the HMT are described and analyzed, and the mathematical models of HMT are built up. The results of computer simulation are carried out which manifest the mathematical models of HMT built in the thesis are feasible and the performance is suitable for multi-function vehicles

The Dynamic Performance Research of Fixture for Automobile Hydraulic Vibration Reliability Test

In order to test the reliability of automobile hydraulic, the vibration reliability test needs to be done. The fixture, which is used to clamp and fix the hydraulic system, is one of the most important components of the test. So the dynamic performance of the fixture has great influence on the vibration test. According to the figure and setting localization of electronics, the three-dimensional model of fixture was constituted. The modal frequency and vibration modal were calculated using FEM. By the result of analysis, the structure of the fixture was mended to meet the test requirement.

The Past, Present, and Future of Dynamic Performance Research

This article reviews the extensive history of dynamic performance research, with the goal of providing a clear picture of where the field has been, where it is now, and where it needs to go. Past research has established that job performance does indeed change, but the implications of this dynamism and the predictability of performance trends remain unresolved. Theories are available to help explain dynamic performance, and although far from providing an unambiguous understanding of the phenomenon, they offer direction for future theoretical development. Dynamic performance research does suffer from a number of methodological difficulties, but new techniques have emerged that present even more opportunities to advance knowledge in this area. From this review, I propose research questions to bridge the theoretical and methodological gaps of this area. Answering these questions can advance both research involving job performance prediction and our understanding of the effects of human resource interventions.