Integrated Simulation System Research Articles

Static performance modeling and simulation of the staged combustion cycle LPREs

The objective of the current research is to analyze the steady state performance of staged combustion cycle liquid propellant rocket engines (SCCLPREs) and to provide a comprehensive case study with all the required technical input data. For this purpose, using the modular concept, engine components are classified into 14 modules and a modeling and simulation platform for SCCLPRE integrated system simulation has been developed in MATLAB Simulink. Space shuttle main engine (SSME) has been selected as a case study, and its static performance has been studied. A total of 34 elements has been taken into account, and using 110 linear/non-linear equations the engine's system modular model has been established. Most of the equations are solved by direct substitution of the initial guesses and iteration through eleven nested iterative loops and a few nonlinear complex equations are solved by Newton–Raphson method. The SSME's throttled performance at four different throttling levels has been simulated, and the effect of throttling has been studied on engine major elements. It is found that by throttling, the pressure of preburners, combustion chamber and high-pressure turbopumps are influenced more than other elements. The simulation mean error at 109% rated thrust level (RTL), 100% RTL, 60% RTL and 50% RTL is 1.63%, 5.76%, 12.91% and 15.28% respectively. Comparing to the previous studies, the simulation accuracy has been enhanced 3% to 7%. The developed model is a basis for further research over SSME and other SCCLPRE.

Numerical simulation on a thermal management system for a small data center

A system with optimum thermal control and noise control is proposed to allow placement of servers at workspace for low operation office cost. A computational fluid dynamics (CFD) model is developed to predict the air flow and temperature distribution of the system. To improve the accuracy of the simulation, the geometry of the axial-flow fan is reproduced in detail and the rotor region is treated with the multiple reference frame model. A porous model is applied to describe the hydraulic and thermal behavior of the evaporator. The integrated system simulation model is validated by measurements. Four layouts of fans are proposed to analyze the airflow organization and temperature distribution. The inhomogeneity of the temperature field is quantitatively evaluated via information entropy and variance. The results reveal that the airflow organization scheme avoids the occurrence of an evident stagnant zone or a hot spot. There are low-velocity zones with insufficient heat transfer in the evaporator. Increasing the number of fans can improve the heat transfer and result in a more uniform temperature distribution. Setting up ventilation fans to increase the ventilation rate of the server is an effective way to meet the challenges of higher heat density.

Distributed and Real-time Integrated Simulation System on Avionics

In order to achieve iterative design in early R&D period, a Distributed and Real-time Integrated Simulation System for avionics based on a Model-Based Systems Engineering (MBSE) method is proposed. The proposed simulation system includes driver, simulation model, monitor, flight visual model and aircraft external model. The effect of this simulation system in iterative design and system verification is testified by several use cases. The result shows that the simulation system, which can play an important role in iterative design and system verification, can reduce project costs and shorten the entire R&D period.

Numerical modeling and simulation technique in time-domain for multibeam echo sounder

A Multibeam Echo Sounder (MBES) is commonly used for rapid seafloor mapping. We herein present a time-domain integrated system simulation technique for MBES development. The Modeling and Simulation (M&S) modules consist of four parts: sensor array signal transmission, propagation and backscattering modeling in the ocean environment, beamforming of the received signals, and image processing. Also, the simulation employs a ray-theory-based algorithm to correct the reconstructed bathymetry, which has errors due to the refraction caused by the vertical sound velocity profile. The developed M&S technique enables design parameter verification and system parameter optimization for MBES. The framework of this technique can also be potentially used to characterize the seabed properties. Finally, typical seafloor images are presented and discussed.

Double Position Servo Synchronous Drive System Based on Cross-Coupling Integrated Feedforward Control for Broacher

Synchronization errors directly deteriorate the machining accuracy of metal parts and the existed method cannot keep high synchronization precision because of external disturbances. A new double position servo synchronous driving scheme based on semi-closed-loop cross-coupling integrated feedforward control is proposed. The scheme comprises a position error cross-coupling feedforward control and a load torque identification with feedforward control. A digital integrated simulation system for the dual servo synchronous drive system is established. Using a 20 t servo broacher, performance analysis of the scheme is conducted based on this simulation system and the simulation results show that systems with traditional parallel or single control have problems when the worktable works with an unbalanced load. However, the system with proposed scheme shows good synchronous performance and positional accuracy. Broaching tests are performed and the experimental results show that the maximum dual axis synchronization error of the system is only 8 μm during acceleration and deceleration processes and the error between the actual running position and the given position is almost zero. A double position servo synchronous driving scheme is presented based on cross-coupled integrated feedforward compensation control, which can improve the synchronization precision.

Visualization and interaction of finite element analysis in augmented reality

In this paper, augmented reality (AR) is used to enhance the visualization and interaction of finite element analysis (FEA) of structures. An integrated simulation system is proposed which acquires input data using sensors and uses AR technology to visualize FEA results in the real world. A number of intuitive interaction methods have been devised and implemented in this system. The user can perform real-time FEA simulation to investigate structural behavior under different loading conditions either through manipulating virtual loads or creating different loading conditions. Exploration of FEA results is enhanced through natural interfaces for manipulating, slicing and clipping the result data. Moreover, the user can modify the FE models of the structures through simplified operations for different purposes, e.g., adding structural members for stiffening and performing local mesh refinement. The modified model can be re-analyzed automatically. A prototype system has been built and a case study has been implemented to demonstrate the innovative interaction methods and evaluate the system performance.

Modeling and simulation technique for development of multibeam echo sounder

Multibeam echo sounder (MBES) is commonly used for rapid sea floor mapping. We present a time-domain integrated system simulation technique for MBES development. The simulation and modeling (M&S) modules consist of four parts: sensor array signal transmission, propagation and backscattering modeling in the ocean environment, beamforming of the received signals, and image processing. Also, the simulation employs a ray-theory-based algorithm to correct the reconstructed bathymetry, which has errors due to the refraction caused by the vertical sound velocity profile. The developed M&S technique enables design parameter verification and system parameter optimization for MBES. The framework of this technique can also be potentially used to characterize the seabed properties. Finally, typical sea floor images are presented and discussed.

IntSIM: An Integrated Simulator of Next-Generation Sequencing Data.

Next-generation sequencing data has been widely used for DNA variant discovery and tumor study through computational tools. Effective simulation of such data with many realistic features is very necessary for testing existing tools and guiding the development of new tools. We present an integrated simulation system, IntSIM, to simulate common DNA variants and to generate sequencing reads for mixture genomes. IntSIM has three novel features in comparison with other simulation programs: 1) it is able to simulate both germline and somatic variants in the same sequence, 2) it deals with tumor purity so as to generate reads corresponding to heterogeneous genomes and also produce tumor-normal matched samples, and 3) it simulates correlations among SNPs, among CNVs/CNAs based on HMM models trained from real sequencing genomes, and can simulates broad and focal CNV/CNA events. The simulation data of IntSIM can reflect characteristics observed from real data and are consistent with input parameters. The IntSIM software package is freely available at http://intsim.sourceforge.net/. Based on a great number of experiments, IntSIM performs better than other program for some scenarios, such as simulation of heterozygous SNPs, CNVs/CNAs, and can achieve some functions that other programs cannot achieve. Simulation with IntSIM can be expected to evaluate performance of methods in detecting various types of variants, analyzing tumor samples, and especially providing a realistic assessment of effect of tumor purity on identification of somatic mutations.

Integrated coupling of road traffic and network simulation for realistic emulation of connected vehicle applications

To meet the requirements of connected vehicle (CV) system simulation evaluations, different simulators (i.e., traffic flow simulation, network communication simulation and CV application simulation) must be combined and interaction must be enabled among them during the run-time of the simulation. This paper proposes a CV simulation prototype system based on integration of three components in one coupling. Considering the characteristics of the distributed interactive simulation of multi-emulators, a high-level architecture simulation and modeling concept is used to construct the simulation framework, and the three types of simulation elements are defined as the primary federates. The integration simulation system is constructed by defining the federation object model and developing the support environment of the run-time infrastructure during simulation. In the simulation implementation procedure, a commercial-off-the-shelf time-stepped VISSIM simulator and an open-source event-driven NS2 simulator are selected as the basic simulation tools to develop the system. In addition, selected related technologies are investigated, including the NS2 simulation model transformation, time synchronization management strategy, track consistency strategy, and integration of application members. Finally, two case studies of intersection speed guidance and collision warning are used to verify the validity of the simulation prototype system.

Numerical Analysis of Melting of Paraffin Wax with Al<Sub>2</Sub>O<Sub>3</Sub>, ZnO and CuO Nanoparticles in Rectangular Enclosure

A numerical study on variations of thermo-physical properties of Phase Change Material (PCM) due to dispersion of nanoparticles is presented in this article. Dispersed metal oxide nanoparticles in paraffin wax might be a solution to improve latent heat thermal storage performance. Thermo-physical properties such as thermal conductivity and latent heat could be changed for different concentration of dispersed nanoparticle. The paper will focus on numerical investigation of the melting of paraffin wax dispersed with three different metal oxide Alumina (Al 2 O) 3 , Copper Oxide (CuO) and Zinc Oxide (ZnO) that is heated from one side of rectangular enclosure of dimensions of 25 mm × 75 mm. The integrated simulation system ANSYS Workbench 15.0 for the numerical study was used including mesh generation tool ICEM and FLUENT software. In FLUENT, the melting model with Volume Of Fluid (VOF) that includes the physical model to disperse nanoparticles in the PCM and their interactions is applied. During melting process, the enhancement of heat transfer is considered. For each nanoparticle analyzed, three different volume fractions are considered and compared. Dispersed nanoparticles in smaller volumetric fractions show a rise the heat transfer rate. The thermal performances are slightly greater using Al2O3 respect both ZnO that CuO nanoparticles.

Design and Realization of Avionics Integration Simulation System Based on RTX

Aircraft avionics system becoming more and more complicated, it is too hard to test and verify real avionics systems. A design and realization method of avionics integration simulation system based on RTX was brought forward to resolve the problem. In this simulation system, computer software and hardware resources were utilized entirely. All kinds of aircraft avionics system HIL (hardware-in-loop) simulations can be implemented in this platform. The simulation method provided the technical foundation of testing and verifying real avionics system. The research has recorded valuable data using the newly-developed method. The experiment results prove that the avionics integration simulation system was used well in some helicopter avionics HIL simulation experiment. The simulation experiment results provided the necessary judgment foundation for the helicopter real avionics system verification.

유무인항공기 통합 시뮬레이션 연구

무인항공기시스템 수요의 증가와 기술의 급격한 발전에 따라 많은 국가들에서 기존의 공역 시스템에 무인항공기를 통합하려는 시도가 이루어지고 있다. 유인항공기와 무인항공기의 통합 운용에 따른 영향을 파악하기 위해서는 유무인항공기의 통합 시뮬레이션 시스템을 통한 HiTL (Human-in-The-Loop) 시뮬레이션이 필요하다. 본 논문에서는 유무인항공기 통합 시뮬레이션을 위한 운용 개념을 정의하고, 유무인항공기 통합 운용 시 발생 가능한 상황을 시나리오로 설정하여, HiTL 시뮬레이션을 수행하였다. 수행 결과에 대해 통신, 안전, 성능, HMI로 나누어 영향을 분석하였다. With the rapid growth of technologies and demand of remotely piloted aircraft systems (RPASs), integration of such systems into the existing airspace is becoming an issue in many countries. To assess the impact of integrated operations of manned and remotely piloted aircraft (RPA), it is necessary to perform Human-in-The-Loop (HiTL) simulations of likely situations with an integrated simulation system. This paper defines several operational concepts for the integrated simulation. Several probable scenarios were developed including a traffic pattern at a small airport and an altitude maneuver at a route crossing. HiTL simulations were performed according to the developed scenarios. The simulation results are analyzed focusing on the impacts of different communication, safety, performance, and human machine interface (HMI) characteristics of RPA.

A full rat-scale model of the basal ganglia and thalamocortical network to reproduce Parkinsonian tremor

We aim to investigate the precise mechanisms underlying Parkinsonian symptoms by large-scale simulation of realistic neural network models including the basal ganglia (BG), thalamus, the motor cortex and spinal cord. Parkinson 's disease is a mid- or late-age degenerative disorder of the central nervous system. The symptoms include akinesia, resting tremor, rigidity and gait problems. A principal cause of PD is the loss of dopaminergic neurons in the substantia nigra pars compacta. How the loss of dopamine transmission causes the symptoms remains unclear. Although it was previously assumed that the tremor is caused by enhanced striatum->GPe (external Globus Pallidus) inhibition, recent experimental data suggests that enhanced GPe->STN (Subthalamic nucleus) inhibition generates synchronized STN rebound bursts to initiate tremor [1]. While the BG oscillation is in beta-band (8-15Hz), the final physical tremor is 4-8Hz, half the BG frequency. The oscillation thus undergoes sub-harmonic responses downstream of the BG, likely in the thalamocortical network. As the oscillation originates through intercellular interactions and depends on multiple distinct areas, we connect multiple spatially-organized network models to form an integrated simulation system. We construct separate BG and thalamocortical models using NEST and connect them with MUSIC. The separate models enable concurrent development by different researchers, and the clean separation simplifies the integration work. The BG model is based on Shouno et al. [2,3]. All subareas are modeled at the full spatial size and neuron numbers of the rat. The striatum includes medium-spiny D1 and D2 neurons and fast-spiking interneurons, with D1 neurons projecting directly to the GPi (internal Globus Pallidus) and D2 neurons to the GPe-STN indirect pathway. The total number of neurons exceeds 3 million. The neuron models are conductance-based with static or STDP synapses. The thalamocortical network model consists of four neuron types in the thalamus and five layers of the primary motor cortex, with neuron numbers, spatial layout and connections based on experimental data. The cortical surface size is 3mm2 and consists of ~180K neurons organized in a stochastic 3-d configuration using Integrate-and-Fire neurons. We show the BG in a normal and a PD-like state with a ~14Hz oscillation in the GPi arising from STN-GPe interaction. Inhibitory GPi-thalamus connection may evoke rebound oscillation in the thalamus, which causes oscillatory output from the cortical pyramidal tract neurons.

IDC장치에 대한 공압시스템의 모델링에 관한 연구

An intelligent deburring control (IDC) device is used to control the constant force for a deburring tool mounted on the end-effector of a robotic arm. This device maintains a constant contact force between the deburring tool and the workpiece in order to provide a good deburring performance. In this paper, we build a mathematical model in Matlab/Simulink to estimate the force control mechanism of the pneumatic system for the IDC device. The Simulink blocks are built for each separate part and are linked into an integrated simulation system. Such a model also relies on the effects of the flow rate through the valve, air compressibility in the cylinder, and time delay in the pressure valve. The results of the simulation are compared to a simple experiment in which convenient math modeling is performed. These results are then used to optimize the mechanical design and to develop a force control algorithm for the pneumatic cylinder.

Integrated Simulation System for 5-axis Milling Cycles

Abstract Multi axis milling is a promising technology for machining of complex geometries and surfaces. Thanks to the additional rotary axis, it provides flexibility to overcome the accessibility issues. However, the process becomes more complicated in terms of geometry, mechanics and dynamics due to the additional degrees of freedom and ball nose end mills. In this study, mechanics and stability of 5-axis ball end milling operations is simulated throughout a given toolpath. The cutting tool-workpiece engagement boundary is calculated and workpiece is represented using distance field approach. Distance field approach features very low computational time, close to real-time simulation. The cutting forces are modeled using orthogonal-to-oblique transformation. Stability limits are estimated in frequency domain.

An Integrated Simulation System for Building Structures

In this paper, an integrated simulation system for building structures is presented to satisfy the engineering requirements for high performance simulation. It is a coalition of the traditional design softwares and general finite element analysis (FEA) softwares. This system is developed in the platform of Intel Fortran, using the programming language of Fortran2003/2008. For simplicity, it would be introduced and discussed briefly in the following article. And combining with YJK and ABAQUS, this system is implemented to perform dynamic analysis for a high-rise building. Its capacity and validity would be demonstrated by the numerical results.

Simulation approach to study the behavior of a milling machine''s structure during end milling operation

This paper presents an integrated simulation system that is employed in order to evaluate the static and dynamic performance of a milling machine. The paper discusses the design consideration of the evaluation system, creates the system based on finite element technique, applies it to a case study, and discusses the results. Obtaining such a reliable model could replace many experimental tests that must otherwise be carried out each time the parameters affecting cutting conditions are changed. Modeling and meshing of various machine elements including the mechanical structure are carried out, contacts between each adjacent elements are defined, load components generated from machining process are modeled, and finally the static and dynamic performance of the entire machine is evaluated. The machine performance is identified in terms of static loop stiffness in both x and y directions, mode shapes, and frequency response function at tool center point.

An Integrated Simulation System Based on Digital Human Phantom for 4D Radiation Therapy of Lung Cancer

Purpose: To develop and test an integrated simulation system based on the digital Extended Cardio Torso (XCAT) phantom for 4-dimensional (4D) radiation therapy of lung cancer. Methods: A computer program was developed to facilitate the characterization and implementation of the XCAT phantom for 4D radiation therapy applications. To verify that patient-specific motion trajectories are reproducible with the XCAT phantom, motion trajectories of the diaphragm and chest were extracted from previously acquired MRI scans of five subjects and were imported into the XCAT phantom. The input versus the measured trajectories was compared. Simulation methods of 4D-CT and 4D-cone-beam CT (CBCT) based on the XCAT phantom were developed and tested for regular and irregular respiratory patterns. Simulation of 4D dose delivery was illustrated in a simulated lung stereotactic-body radiation therapy (SBRT) case based on the XCAT phantom. Dosimetric comparison was performed between the planned dose and simulated delivered dose. Result: The overall mean (±standard deviation) difference in motion amplitude between the input and measured trajectories was 1.19 (±0.79) mm for the XCAT phantoms with voxel size of 2 mm. 4D-CT and 4D-CBCT images simulated based on the XCAT phantom were validated using regular respiratory patterns and tested for irregular respiratory patterns. Comparison between simulated 4D dose delivery and planned dose for the lung SBRT case showed comparable results in all dosimetric matrices: the relative differences were 0.3%, 4.0%, 0%, and 2.8%, respectively, for max cord dose, max esophagus dose, mean heart dose, and V20Gy of the lungs. 97.5% of planning target volume (PTV) received prescription dose in the simulated 4D delivery, as compared to 95% of PTV received prescription dose in the plan. Conclusion: We developed an integrated simulation system based on the XCAT digital phantom and illustrated its utility in 4D radiation therapy of lung cancer. This simulation system is potentially a useful tool for quality control and development of imaging and treatment techniques for 4D radiation therapy of lung cancer.

Fuel cell–gas turbine hybrid system design part II: Dynamics and control

Fuel cell gas turbine hybrid systems have achieved ultra-high efficiency and ultra-low emissions at small scales, but have yet to demonstrate effective dynamic responsiveness or base-load cost savings. Fuel cell systems and hybrid prototypes have not utilized controls to address thermal cycling during load following operation, and have thus been relegated to the less valuable base-load and peak shaving power market. Additionally, pressurized hybrid topping cycles have exhibited increased stall/surge characteristics particularly during off-design operation. This paper evaluates additional control actuators with simple control methods capable of mitigating spatial temperature variation and stall/surge risk during load following operation of hybrid fuel cell systems. The novel use of detailed, spatially resolved, physical fuel cell and turbine models in an integrated system simulation enables the development and evaluation of these additional control methods. It is shown that the hybrid system can achieve greater dynamic response over a larger operating envelope than either individual sub-system; the fuel cell or gas turbine. Results indicate that a combined feed-forward, P–I and cascade control strategy is capable of handling moderate perturbations and achieving a 2:1 (MCFC) or 4:1 (SOFC) turndown ratio while retaining >65% fuel-to-electricity efficiency, while maintaining an acceptable stack temperature profile and stall/surge margin.

Shafting Vibration Simulation for Hydro Turbine Generating Sets

Based on the transient model of hydro turbine generating sets (HTGS), the integrated simulation system of HGTS is built to study shafting stability. Given different bearing stiffness, equivalent damping coefficient and mass eccentricity, the change characteristics of shafting vibration at rated angular speed in steady and maximum angular speed in transient are simulated, and which are applied to study inferences shafting parameters and angular speed on shafting vibration. Simulation results show that the relationship between shafting vibration amplitude and angular speed is linear. however, the vibration amplitude increment produced by angular speed error will be amplified while the shafting stiffness is weaker, mass eccentricity of the runner and rotor is larger.