Optimal Design of Stewart Platform Safety Mechanism

A safety mechanism capable of moving at will within the range of its whole link lengths is designed based on the link space. Sixteen extreme poses are obtained in a Stewart platform. The singular points of the extreme poses are solved by using homotopy method as well as the judgment condition of singular points, and thereby the maximum link lengths are achieved. The rotation angles of joints and the distances between two neighboring links are analyzed in a calculation example in which that the mechanism moves among the extreme poses is assumed. Then an algorithm to test the safety mechanism is presented taking the constraint conditions into account. A safety mechanism having optimal properties of global movement is worked out by optimizing all structural parameters through minimizing the average condition number of extreme poses.

Concept Design,Modeling and Station-keeping Attitude Control of an Earth Observation Platform

The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynamics, model uncertainties, and external disturbances contribute to the difficulty in maneuvering the stratosphere airship. A key technical challenge for the earth observation platform is station keeping, or the ability to remain fixed over a geo-location. This paper investigates the conceptual design, modeling and station-keeping attitude control of the near-space earth observation platform. A conceptual design of the earth observation platform is presented. The dynamics model of the platform is derived from the Newton-Euler formulation, and the station-keeping control system of the platform is formulated. The station-keeping attitude control approach for the platform is proposed. The multi-input multi-output nonlinear control system is decoupled into three single-input single-output linear subsystems via feedback linearization, the attitude controller design is carried out on the new linear systems using terminal sliding mode control, and the global stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the designed control system is simulated by using the variable step Runge-Kutta integrator. Simulation results show that the control system tracks the commanded attitude with an error of zero, which verify the effectiveness and robustness of the designed control system in the presence of parametric uncertainties. The near-space earth observation platform has several advantages over satellites, such as high resolution, fast to deploy, and convenient to retrieve, and the proposed control scheme provides an effective approach for station-keeping attitude control of the earth observation platform.

Optimum Design of Jacket Platforms Considering Structure-Pile-Soil Interaction

This paper proposes an optimum design model for the offshore jacket platform considering multidesign criteria, multi-design constraints and the structure-pile-soil interaction, and gives an optimum design procedure in which the proposed optimum design model is used together with structural analysis software SAP91 and optimum algorithm software OPB1. The Chengbei (#)11 offshore platform, which lies in the Shengli oilfield, is designed by use of the above optimum design model. The results show that the optimum design model is stable, and it depends on neither the optimization algorithm nor initial values of design variables. All values of the objective function converge to the same minimum value, and the speed of convergence is high, showing that the proposed optimum design model is reasonable.

Finite Element Method for Design of Reinforced Concrete Offshore Platforms

A design method of reinforced concrete (R. C.) offshore platforms with nonlinear finite element analysis is proposed. According to the method, a computer program is developed. In this program nonlinear constitutive relationships and strength criteria of concrete and steel bars are included, and the progressive cracking and crushing of the concrete are taken into account. Based on the stress distribution obtained by the nonlinear finite element analysis, the amount of reinforcement in the control sections can be computed and adjusted automatically by the program to satisfy the requirement of the design. The amount of reinforcement required in the control sections, which are obtained with the nonlinear finite element analysis, is agreeable to that obtained in the experiment. This shows that the design method of R. C. offshore platform with the nonlinear finite element method proposed by the authors is reliable for practical use.

Investigation of Allowable Stresses for Fatigue Design of Fixed Offshore Platforms

Fatigue design method is usually used for estimating whether a platform structure meets the requirements of fatigue resistance. It is described in API RP-2A and ZC rules for fixed offshore platforms, in which the allowable stresses for fatigue design are defined. In this paper discussed are the allowable stresses related factors, such as wave climate, structural response, fatigue behaviour of structural members.

Design and Development of System Platform of "Study on Relationship between Natural Phenology and Climate Change" Based on WEB and GIS

[Objective] The research aimed to study design and development of system platform of 'study on relationship between natural phenology and climate change' based on WEB and GIS. [Method] Relied on the technologies of WEB and GIS, a set of system platform of 'study on relationship between natural phenology and climate change' was developed based on the hybrid architecture of C/S (Client/Server) and B/S (Browser/Server). Moreover, its establishing process and functional module were detailedly introduced. [Result] The natural phenology and climate change in Guangxi were research objects of system platform of 'study on relationship between natural phenology and climate change'. By combining WEB and GIS with database, the primary application of 'study on relationship between natural phenology and climate change' was realized. The system used hybrid architecture of C/S and B/S. The four-layer architectures were independent to improve security, stability and maintainability of system. The visual interface on the foreground was simply, clear and easy to use. The generating program of GIS three-dimensional graph on the background was real-time and high-efficiency, providing powerful guarantee for stable and safe operation of phenology research work process. The system had functions of inquiry, analysis, statistical diagram, GIS three-dimensional graph and data export. Through the analysis of natural phenology observation data, the system could find variation rule of natural phenology as three-dimensional space (longitude, latitude and altitude) and its relationship with climate change. [Conclusion] The research laid good foundation for further deeply carrying out application of 'study on relationship between natural phenology and climate change', and also provided reference basis for recognizing nature and using change rule of phenology to execute production scheduling and strategic decision (seed-introduction and regionalization).

A preliminary study on seismic design criteria of offshore platforms in Bohai Sea of China

This paper analyzes the seismicity in Bohai Sea,introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located in the Bohai Sea,a statistical analysis was performed for different peak ground acceleration (PGA) ratios at two different probability levels. In accordance with the two-stage design method,a scheme of two seismic design levels is proposed,and two seismic design objectives are established respectively for the strength level earthquake and the ductility level earthquake. By analogy with and comparison to the Chinese seismic design code for buildings,it is proposed that the probability level for the strength level earthquake and ductility level earthquake have a return period of 200 and 1000 - 2500 years,respectively. The validity of these proposed values is discussed. Finally,the PGAs corresponding to these two probability levels are calculated for different sub-regions of the Bohai Sea.

An Agent-Based Multimedia Intelligent Platform for Collaborative Design

Collaborative design can create added value in the design and production process by bringing the benefit of team work and cooperation in a concurrent and coordinated manner. However, distributed design knowledge and product data make the design process cumbersome. To facilitate collaborative design, an agent-based intelligent CAD platform is implemented. Intelligent agents are applied to the collaborative design. Adopting the JADE platform as framework, an intelligent collaborative design software (Co-Cad platform for short) is designed. In this platform, every man, design software, management software, equipment and resource is regarded as a single agent, the legacy design can be abstracted to be interaction between agents. Multimedia technology is integrated into Co-Cad platform, communication and identity authentication among collaborative designers from different areas are more convenient. Finally, an instance of collaborative design using Co-Cad platform is presented.

Multilevel Optimal Design of Prestressed Lightweight Concrete-Steel Platform Structures

The concrete-steel platform structure is rather complicated because it involves such materials as concrete, reinforcing bars, steel, and so on. If the traditional dimension optimization method is employed, the optimal design of the platform will meet many handicaps, even it cannot be implemented at all. The multilevel optimal design approach is an efficient tool for the solution of large-scale engineering structures. In this paper, this approach is applied to the optimal design of a concrete-steel platform, which is formulated as a system level optimal design problem and a set of uncoupled substructure level optimal design problems. The process of optimization is a process of iteration between system level and substructure level until the objective function converges. An illustrative example indicates that this method is effective in the optimal design of concrete-steel platforms.

Design of A Bionic Spudcan and Analysis of Penetration and Extraction Performances for Jack-up Platform

The mechanisms of soil structure interaction have drawn much attention in the past years in the installation and operation of jack-up platform. A bionic spudcan produced by biomimetic of egg and snail shell is proposed, and the performance of the penetration and extraction are analyzed by numerical method. The geometric contour of egg and snail shell is measured, and its mathematical model is established respectively. According to the structure of existing spudcan of jack-up platform, three kinds of typical biomimetic spudcan are designed. Furthermore, numerical analysis models of biomimetic spudcan are established respectively to study the soil structure interaction mechanism in the process of penetration and extraction, and contrastive analysis of resistance characteristics are carried out. To conclude, the results show that the biomimetic spudcan facilitates the platform installation, and it is also beneficial to the improvement of the bearing capacity of spudcan.

Reliability-Based Full-Life Cycle Optimum Design of Offshore Jacket Platform

Based on the consideration of operation environment and structural property, an optimum design model of offshore jacket platform is developed in this paper, namely, the reliability-based full-life cycle optimum design model. In this model, the time-dependent reliability assessment method for structural members is established by combination of the decrease of sectional size and performance deterioration of material. The initial investment, maintenance cost and failure loss cost are assembled into the model. The total cost of the platform structure system in its full service period is chosen as the objective function, and the initial reliabilities of the layer elements partitioned in advance are taken as the design variables. Different models are obtained, depending on whether the system reliability constraint is considered or not. This optimum design model can result in the lowest full-life cost and the optimal initial layer reliability of an offshore jacket platform in the design of marine structures. The feasibility of this model is illustrated with an actual jacket platform in the Liaodong Gulf as an example.

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.

Parameter identification of inertially stabilized platforms using current command design

Accurate parameter identification is essential when designing controllers for inertially stabilized platforms (ISPs). But traditional identification methods suffer from observation measurement noise and operating restrictions of ISPs. To address this issue, a novel identification method based on current command design and multilevel coordinate search (MCS) algorithm without any higher order measurement differentiations was proposed. The designed current commands were adopted to obtain parameter decoupled models with the platform operating under allowable conditions. MCS algorithm was employed to estimate the parameters based on parameter decoupled models. A comparison experiment between the proposed method and non-linear least square method was carried out and most of the relative errors of identified parameters obtained by the proposed method were below 10%. Simulation and experiment based on identified parameters were conducted. A velocity control structure was also developed with disturbance observer (DOB) for application in disturbance compensation control system of an ISP. Experimental results show that the control scheme based on the identified parameters with DOB has the best disturbance rejection performance. It reduces the peak to peak value (PPV) of velocity error integral to 0.8 mrad which is much smaller than the value (10 mrad) obtained by the single velocity controller without DOB. Compared with the control scheme based on sweep model with DOB compensation, the proposed control scheme improves the PPV of velocity error integral by 1.625 times.

面向综合能源协调的虚拟电厂调控平台设计与规划优化

为解决综合能源协调调度难题,文章提出了基于虚拟电厂调控平台设计和综合能源协调调度模型。通过分析虚拟电厂的基本网架结构,设计了虚拟电厂总体架构,分为资源层、平台层和应用层,并设计了网络架构和数据流架构。基于该架构建立了面向综合能源协调的虚拟电厂调度应用模型。针对模型内光伏、风力发电、电解器、燃料电池、氢气储能、电池储能,以可靠性指标作为切入点,提出了全生命周期内成本最小的目标函数。通过算例分析,验证了文章所提出的模型在可靠性和成本方面的优势。

基于ZigBee和云平台的大棚环境监测系统设计与实现

针对温室大棚环境的实时监测问题,利用ZigBee无线传感网络和GPRS远程传输技术,设计远程监测系统,在云端搭建服务器,采用Spring Boot服务框架,开发Android移动端APP.测试表明,系统能对温室大棚环境进行远程监测和预警,系统运行稳定、部署灵活、便利性好,有利于提高大棚农业管理水平.

基于“仿真—半实物仿真—实物”三阶段开发流程的DAB变换器实验探索与研究

该文以双有源桥DC-DC变换器为对象,详细分析了变换器在三重移相调制下的两种数学模型,又基于这两种数学模型提出了对应的电感电流优化控制策略,搭建了包含MATLAB/Simulink仿真平台、StarSim半实物仿真平台和实物平台的三阶段实验平台,在平台中通过实验验证了优化控制策略的可行性和有效性。所设计的三阶段开发流程能够加深学生对电力电子领域相关知识的理解,逐步提升学生的理论分析能力、仿真验证能力和实践操作能力。

基于校企合作的燃气输配智慧化实验平台设计与开发

针对燃气企业人才职业能力培养与新工科背景下燃气输配课程教学改革的需要,实施行业指导、校企共建,设计建设了燃气输配智慧化实验平台,开发出多种类型的实验项目,构建了多层次实验教学项目体系并进行了实验教学方法的探索。该平台运用各种信息化先进技术,可模拟燃气输配管网工艺系统及运行工况、燃气管网智能化控制系统运行、燃气管网事故应急处理等任务,具有丰富多样的实验与工程实训功能,有利于实施理实一体化教学,锻炼和提高学生的工程实践能力、智能化能力和创新意识,加强培养学生解决城市燃气输配复杂工程问题的能力和素质。

智慧灌溉大数据管理平台设计与应用

以粗放型为主的漫灌方式浪费水资源,探索高效节水农业灌溉意义重大。本研究研制了集数据采集、数据管理、数据可视化、分析决策和远程管理为一体的智慧灌溉大数据管理平台,旨在以数字化管理与智能化控制方式提升水资源利用效率。平台利用嵌入式、物联网、互联网、3S(GIS、GPS、RS)等技术,采取“1+1+N”的设计模式,构建作物需水预报模型与灌溉决策模型,基于B/S构架和Java语言,设计了1个灌溉数据中心、1个灌溉数据管理系统、4个应用系统,打造了智慧灌溉大数据管理平台。平台在河北、河南、山东、江苏等地区设有多个示范基地,汇聚了8个科研小组、24个试验基地的有关多种作物的生长、灌溉、气象、土壤等数据,平均采集数据18829条/天,帮助管理人员摸清家底;集成了多个团队的软件系统和62套物联网设备,及时、定量地呈现了农作物生长状况及环境状态,实现了农作区动态监测,助力生产决策;生成农作物需水预报和灌溉决策方案,完成了远程灌溉目标,并且经过实地试验,验证了自动灌溉的有效性,将灌溉水有效利用系数最高提升了31%以上;形成了大田产业、温室中心、数字科研和区域灌溉等不同专题可视化布局,满足多种农业场景应用需求。为农业生产和跨区域管理提供了便捷工具,为农业灌溉数字化系统搭建和应用提供了参考。

基于等级保护2.0的高校校园网安全平台设计

文章分析了我国高校当前面临的网络安全形势,从落实网络安全等级保护视角,以四川民族学院校园网安全为研究对象,基于等级保护2.0标准,从管理和技术两个维度对高校校园网安全平台设计,构建安全合规、具有前瞻性技术理念的网络安全平台,最后对基于等级保护2.0高校校园网安全平台的目标和实现进行了深入探讨.