Forward Dynamics Analysis of the 6-PUS Mechanism Based on Platform-Legs Composite Simulation

The dynamics analysis plays an important role for the control, simulation and optimization of the parallel manipulators. Normally, the Stewart type manipulators have a platform and several legs. The inverse dynamics can be solved efficiently by taking the advantage of such structural characteristics. However, for the forward dynamics analysis, this structural decomposition still faces challenges from both modeling and computation. In this paper, an efficient approach is proposed for the forward dynamics of the 6-PUS manipulator based on the platform-legs composite simulation. By composite method, the dynamics modeling of the parallel manipulator is separated into the forward dynamics of the platform and the kineto-statics of the legs. The global simulation model can be constructed by connecting the predefined platform model and leg models according to the manipulator＇s topology. Thus, the global simulation can be decomposed into the independent calculations of purely algebraic equations and ordinary differential equations （ODEs）, the computational cost can be reduced and the stability of the simulation can be improved. For the purpose of solving the manipulator＇s forward dynamics accurately, the algebraic-loop problem is discussed and a closed form algorithm is proposed. A numerical example of the 6-PUS manipulator is given to demonstrate the effectiveness of the proposed approach. The example results show that the modeling efficiency can be improved and the simulation stability can be ensured for decomposing the system equations into purely algebraic equations and ODEs.

SPACECRAFT DOCKING SIMULATION USING HARDWARE-IN-THE-LOOP SIMULATOR WITH STEWART PLATFORM

A ground-based hardware-in-the-loop （HIL） simulation system with hydraulically driven Stewart platform for spacecraft docking simulation is presented. The system is used for simulating docking process of the on-orbit spacecraft. Principle and structure of the six-degree-of-freedom simulation system are introduced. The docking process dynamic of the vehicles is modeled. Experiment results and mathematical simulation data are compared to validating the simulation system. The comparisons of the results prove that the simulation system proposed can effectively simulate the on-orbit docking process of the spacecraft.

Real-time hybrid simulation of structures equipped with viscoelastic-plastic dampers using a user-programmable computational platform

A user-programmable computational/control platform was developed at the University of Toronto that offers real-time hybrid simulation （RTHS） capabilities. The platform was verified previously using several linear physical substructures. The study presented in this paper is focused on further validating the RTHS platform using a nonlinear viscoelastic-plastic damper that has displacement, frequency and temperature-dependent properties. The validation study includes damper component characterization tests, as well as RTHS of a series of single-degree-of-freedom （SDOF） systems equipped with viscoelastic-plastic dampers that represent different structural designs. From the component characterization tests, it was found that for a wide range of excitation frequencies and friction slip loads, the tracking errors are comparable to the errors in RTHS of linear spring systems. The hybrid SDOF results are compared to an independently validated thermal- mechanical viscoelastic model to further validate the ability for the platform to test nonlinear systems. After the validation, as an application study, nonlinear SDOF hybrid tests were used to develop performance spectra to predict the response of structures equipped with damping systems that are more challenging to model analytically. The use of the experimental performance spectra is illustrated by comparing the predicted response to the hybrid test response of 2DOF systems equipped with viscoelastic-plastic dampers.

An agent-based simulation with NetLogo platform to evaluate forward osmosis process(PRO Mode)

Forward osmosis(FO), as an emerging technology, is influenced by different factors such as operating conditions,module characteristics, and membrane properties. The general aim of this study was to develop a suitable(flexible,comprehensive, and convenient to use) computational tool which is able to simulate osmosis through an asymmetric membrane oriented in pressure retarded osmosis(PRO) mode in a wide variety of scenarios. For this purpose, an agent-based model was created in NetLogo platform, which is an easy-to-use application environment with graphical visualization abilities and well suited for modeling a complex system evolving over time. The simulation results were validated with empirical data obtained from literature and a great agreement was observed. The effect of various parameters on process performance was investigated in terms of temperature,cross-flow velocity, length of the module, pure water permeability coefficient, and structural parameter of the membrane. Results demonstrated that the increase in all parameters, except structural parameter of the membrane and the length of module led to the increase of average water flux. Moreover, nine different draw solutes were selected in order to assess the influence of net bulk osmotic pressure difference between the draw solution(DS) and feed solution(FS)(known as the driving force of FO process) on water flux. Based on the findings of this paper, the performance of FO process(PRO mode) can be efficiently evaluated using the NetL ogo platform.

Numerical Simulation of Float-Over Installation for Offshore Platform

In this paper,a numerical investigation of a float-over installation for an offshore platform is presented to verify the feasibility of the actual installation.The hydrodynamic performance of a T-barge is investigated in the frequency domain,and the coupled motions are analyzed in the time domain.We then compare with those of the model test and determine that the response amplitude operator and the time series agree quite well.The barge exhibits favorable hydrodynamic behavior in the considered sea state,and the equipment loads are allowable.Themooring systemand sway fender forces are within the permissible range.Based on these results,we can verify that the actual installation of the offshore platform is feasible.We accurately simulated many important factors and effectively reduced the risk associated with the offshore installation,which is of great importance.As such,we demonstrate that the numerical simulation of the float-over installation for offshore platforms has practical engineering significance.

Research on hydraulic wind turbine semi-physical simulation platform

According to a research on the 30kVA simulation experimental platform of hydraulic wind tur- bine, its basic structure, composition and operation principle are expounded in this paper. An in- verter motor is used to simulate the wind turbine, while a similarity calculation method is applied be- tween the small and large wind turbine. A fixed displacement pump-variable motor closed loop is used as the main transmission system, and a self-excited synchronous generator generates electricity through the grid connection. The experiment and simulation study on the speed and power control of the hydraulic wind turbine is conducted, based on the experimental platform, thus correctness and progressiveness of the experiment platform is further verified. The experimental platform study lays a foundation for further research on the characteristics of hydraulic wind turhln~

6-DOF Motion Assessment of A Hydrodynamic Numerical Simulation of A Semisubmersible Platform Using Prototype Monitoring Data

Hydrodynamic numerical simulations are used to conduct structural analyses and inform the design of engineered marine structures.In this paper,a hydrodynamic numerical model of“Nanhai Tiaozhan”(NHTZ)FPS platform was established according to its design specifications.The model was assessed with two sets of field monitoring data representing harsh and conventional sea states.The motion responses of the platform according to the measured data and the hydrodynamic simulation were compared by reviewing their statistical characteristics,distributions,and spectrum characteristics.The comparison showed that the hydrodynamic model could correctly simulate the frequency domain characteristics of the motion responses of the platform.However,the simulation underestimated the reciprocating motions of the floating body and the influence of slow drift on the motion of the platform.Meanwhile,analysis of the monitoring data revealed that the translational degrees of freedom(DOF)and rotational DOF of the platform were coupled,but these coupled motion states were not apparent in the hydrodynamic simulation.

Optimal Design of the Superstructure of an Offshore Tourism Platform by Using Numerical Simulation

This paper aims to reduce the wind resistance of the self-designed offshore tourism platform by optimizing its superstructure,and a transparent shape design is finally suggested.A numerical simulation was performed to calculate the wind load on the platform to test the effect of wind resistance reduction.Two original scale models(sealed and transparent)were established in accordance with the design requirements.The numerical simulation uses the FLUENT software combined with the built-in self-compiled user-defined function(UDF).The stochastic wind was also applied on the basis of the Davenport wind spectrum.The detached eddy simulation(DES)model was used to solve the NS equation.Numerical simulation results show that the wind resistance reduction for the transparent shape model is subtle in the horizontal direction but can effectively reduce the drag force and moment in the vertical direction.Moreover,the force variation of the transparent shape model under different wind attack angles decreases,which reduces the wind load fluctuations.

Analysis of the Oscillating Mechanism of an Aerial Work Platform Based on ADAMS Hydraulic-Mechanical Coupling Simulation

Rigid model of the aerial work platform and hydraulic model of the oscillating mechanism were established with ADAMS. The simulation of two parameters, cy-linder force and oil chamber pressure, was carried out. The simulation result is useful to the design of the oscillating mechanism.

Database application platform for earthquake numerical simulation

Introduction In recent years, all kinds of observation networks of seismology have been established, which have been continuously producing numerous digital information. In addition, there are many study results about 3D velocity structure model and tectonic model of crust （Huang and Zhao, 2006; Huang et al, 2003; Li and Mooney, 1998）, which are valuable for studying the inner structure of the earth and earthquake preparation process. It is badly needed to combine the observed data, experimental study and theoretical analyses results by the way of numerical simulation and develop a database and a corresponding application platform to be used by numerical simulation, and is also a significant way to promote earthquake prediction.

A Study of Virtual Museum Simulation Platform Based on 2.5D Architectural Modeling Technology

With the application of virtual reality technology to realize interactive display of virtual museum as content of study,we analyze the problems in the current virtual museum system.Taking Daqing Museum for example,we develop a 2.5D(between 2D and 3D) architectural modeling technology,and combine it with virtual reality technology,to create the virtual museum simulation platform.By establishing the virtual simulation platform of Daqing Museum,we verify the feasibility of using 2.5D architectural modeling technology to build the virtual museum system,create a virtual simulation platform with practical value,and show the bright future of virtual museum based on 2.5D virtual reality technology.

CBTC Simulation Platform Design and Study

In order to train and test the functionality of the CBTC signal system, this paper designs simulation platform’s architecture and function module based on the CBTC principle firstly. Then, it detailedly discusses the main content and key algorithms about train module and trackside module. Finally, it builds CBTC simulation test platform, used for training of rail transit signal related specialized student and detecting the main function of actual CBTC system based on Shanghai Metro Line 9.

Simulation platform of navigation system for autonomous underwater vehicle

In view of the characteristics of underwater navigation, the simulation platform of navigation system for autonomous underwater vehicle has been developed based on Windows platform. The system architecture, net communication and the information flow are discussed. The methods of software realization and some key techniques of the Vehicle Computer and the Navigation Equipment Computer are introduced in particular. The software design of Terrain Matching Computer is introduced also. The simulation platform is verified and analyzed through simulation. The results show that the architecture of the platform is reasonable and reliable, and the mathematic models and simulation algorithms of sub-systems are also valid and practicable.

Environmental simulation platform and its application to geodesic instruments for a performance study

In this study,an environmental simulation platform(ETS-02)was constructed for high-precision geodesic instruments(e.g.,absolute/relative gravimeters and inclinometers),to test the disturbances caused by environmental fl uctuations.The outer layer of the platform was constructed with two sets of rectangular electromagnetic coils,which generated the required magnetic fi eld when current was applied.The inner layer was a closed cabin in which radiators were distributed such that the temperature of the experimental space inside the cabin could be controlled,by energy exchange between the radiators and a thermal controller through the fl owing liquid.A high-precision hexapod was used to simulate the tilt-related eff ect.The platform was capable of adjusting temperatures within a dynamic range of 0℃-70℃ at a resolution of 0.01℃.The noise of the power-spectrum density when the cabin was set to room temperature was measured as 0.03℃/Hz^(1/2) at 1 mHz.The magnetic field simulation had a dynamic range of±300μT and stability of 20 nT.The resolution of the ground-tilt simulation was 1 arc s.The inner space of the platform had a volume of approximately 5 m^(3),which is sufficient for most types of instruments to be tested for a general environmental coupling effect.To illustrate the application of the platform,a dual-axis inclinometer was built and tested carefully with the platform,and the accuracy of the calibration factors was found to be signifi cantly improved.

ERP Virtual Simulation Experiment Teaching Platform based on UFIDA Cloud Computing

Economic Management Professional Academic Education are increasingly becoming personalization,intelligence and application.Colleges and universities should actively use cloud computing and big data.Also Internet of Things and other advanced information technologies to build an economics and management ERP virtual simulation experiment teaching platform.Cloud computing and big data,virtual simulation experiment teaching resources with"resource library+project library+enterprise management simulation sandbox training"as the core can build an online and offline collaborative and practical experiment teaching platform.It is expected to achieve the ideal effect of integration of three spaces.Such as physics and resources and social digital teaching.Moreover,it can also benefit human-computer collaboration and interactive teaching and inquiry learning.

Methods for the Construction and Realization of a Humanoid Robot's Simulation Platform

This paper proposes a method of humanoid robot data structure definition based on the characteristics of a graph with tree structure. It applies the depth-first search algorithm to traverse and uses screw theory and chain of multiplication to describe the robot＇s postures. The platform references zero moment point theory as the stability constraint of the robot＇s dynamic walking and plans the gaits accordingly, h also realizes the visualization of motion control. This study provides superior means and methods to the evolution of a humanoid robot.

Research on Interactive Simulation Experiment Platform and Remote Simulation System Under Web Environment

This paper brings forward a method of experimental teaching reform of universities and colleges,which establishes an interactive simulation experiment platform with MATLAB simulation software.The platform uses visual man-machine interface,which avoids a lot of programming and debugging work,and improves students’learning enthusiasm.Simultaneously,it implements remote simulation based on JAVA under web environment,which is convenient for network teaching,and improves flexibility and practicability of the simulation experiment platform.

X-In-the-Loop Methodology and Simulation Platform For Controller Development of Gravity-1

The Gravity-1(YL-1) launch vehicle has been extensively optimized in terms of its overall layout which in turn has increased the functional and performance demands on the control system. To thoroughly validate and verify the control system, the X-In-the-Loop simulation methodology was implemented from the verification of the YL-1's concept phase. Throughout the entire development cycle, from the initial concept demonstration to the flight test,simulations under sevral modes including Model-in-the-Loop(MiL), Software-in-the-Loop(SiL) and Hardware-in-theLoop(HiL) were executed following the V-V process which ensuring the correctness and robustness of the control system. Specifically, MiL simulation are primarily used to verify the accuracy and robustness of the control strategies and parameters. SiL simulation focused on verifying the correctness of the code implementation. Whereas HiL testing mainly checked the operational correctness of the flight control hardware, the compatibility of flight control software within the flight control computer and the correctness of hardware I/O. In addition to these, further semi-physical simulations were possible on the HiL platform by replacing models of controlled objects with real devices such as IMUs and TVC actuators. And realistic flight conditions were replicated through turntables, TVC actuator loading tables etc.to achieve a more comprehensive validation and verification of the control system.

Virtual Simulation Experiment Teaching Platform Based on 3R-4A Computer System

Virtual simulation experiment teaching gradually becomes the trend of the computer-related education practice.Through analyzing the problems existed in current computer experiment teaching,this paper proposes the idea of building virtual simulation experiment platform based on 3R-4A computer system and clarifies the design technology,including frame,characteristic and innovation,resource sharing and management,condition protection and so on.

Design of Simulation Competition Platform Based on Cognitive Behavior Modeling

Cognitive behavior modeling of agent is an important component of simulation system,and there are some difficulties in the simulation of course teaching.When students make simulation experiments about cognitive behavior modeling,such as algorithm design and model construction,there is no simulation competition platform that is controllable,flexible and scalable.To solve this problem,we propose a simulation competition platform based on cognitive behavior modeling,called TankSim,for undergraduate and graduate students.This platform aims to cultivate studenfs team collaboration and innovation capability,and improve their learning motivation.This paper elaborates the proposed platform from three aspects,including demand analysis,platform design,and content design.