Global modes for the reduction of flexible multibody systems

Multibody System Dynamics - Modeling a flexible multibody system employing the floating frame of reference formulation (FFRF) requires significant computational resources when the flexible...     

Global and regional path planners for integrated planning and navigation

This paper presents a hierarchical strategy for field mobile robots that incorporates path planning at different ranges. At the top layer is a global path planner that utilizes gross terrain characteristics, such as hills and valleys, to determine globally safe paths through the rough terrain. This information is then passed via waypoints to a regional layer that plans appropriate navigation paths using regional terrain characteristics. The global and regional path planners share the same map information, but at different ranges. The motion recommendations from the regional layer are then combined with those of the reactive navigation layer to provide reactive control for the mobile robot. Details of the global and regional path planners are discussed, and simulation and experimental results are presented. © 2005 Wiley Periodicals, Inc.     

An integrated simulator for coupled domain problems in MEMS

An integrated circuit and microfluidic simulator is presented in this paper. It allows coupled simulation of flow, structure, thermal, and electrical domains. The overall architecture and various algorithms including the coupling of the circuit and microfluidic simulators are described. An application of the simulator is demonstrated for a controlled microliquid dosing system using detailed numerical models for the fluid field, a low-dimensional model for the flow sensor, and circuit elements for the electronic control. Unlike other simulators which employ mostly lumped models for the various components, we formulate here a methodology for distributed systems     

Comparative study of the bimanual and collaborative modes for closely coupled manipulations

The interactive manipulation of complicated environments poses a real challenge since it involves the simultaneous management of several heterogeneous constraints. For instance, molecular design requires the simultaneous control of several connected kinematic structures, with strong physical and chemical interactions, to provide the relevant conformation and docking solutions. This paper investigates two working strategies for carrying out closely coupled manipulations in such environments. We present an experimental study which compares bimanual and collaborative configurations. For both strategies, we provide users with the same number of resources, such as the same visualization system and the same number of manipulation tools. The performances are better in the collaborative configuration for the simultaneous management of several constraints and the manipulation of distant regions. However, this working strategy involves a strong communication flow to coordinate the actions. The performances are better in the bimanual configuration when the tasks involve a limited working space and a low level of constraints.     

Global stability analysis for stochastic coupled systems on networks

This paper considers the global stability problem for some stochastic coupled systems on networks (SCSNs). We provide a systematic method for constructing a global Lyapunov function for these SCSNs, by using graph theory and the Lyapunov second method. Consequently, a new global stability principle, which has a close relation to the topology property of the network, is given. As an application to the results, we employ the principle to two well-known coupled systems in physical and ecology, and then some easy-verified sufficient conditions which guarantee the global stability are obtained.     

一种八边形的混合快速运动估计算法

根据图像序列的运动矢量的时空相关性和中心偏移特性,并结合零运动判断,设计研究了一种八边形模式搜索[1]。其在中等或大运动块的情况下相对于FS、TSS、DS、MVFAST能够得到更高的精确度,又由于对非静止块采用了起始点预测,减少了搜索的时间,同时可以大大提高搜索速度。     

STEELEX: A coupled expert system for integrated design of steel structures

Most expert systems developed so far are concerned with symbolic processing of a knowledge base. Solution of complex engineering problems often requires substantial numerical processing in addition to symbolic processing of heuristics and experiential knowledge. In this paper, we present STEELEX, a prototype knowledge-based expert system for integrated design of building structures consisting of moment-resisting steel frames. STEELEX is a coupled system in which AI symbolic processing is combined with conventional numerical processing. STEELEX produces the final detailed design including the beam-column connections ready for fabrication. In addition, it can explain the basis of design and the principles behind the design specification. STEELEX has been developed using a domain-specific tool called SDL (for Structural Design Language). Implemented in the INTERLISP environment, SDL provides a design problem-solving environment using a hierarchical cooperating specialists paradigm. STEELEX has a debugging facility and provides a multiwindow graphics interface for drawing isometric as well as orthographic views of the steel frame and beam-column connections.     

Global synchronised regions of linearly coupled Lur'e systems

This article addresses the global synchronisation problem of a network of coupled Lur'e systems from the perspective of global synchronised region. A decomposition approach is proposed to convert the synchronisation of high-dimensional Lur'e networks into the test of a set of matrix inequalities whose dimensions are the same as a single Lur'e node. The notion of global synchronised region is then introduced and analysed. A necessary and sufficient condition is derived for the existence of the inner-linking matrix to guarantee a desirable unbounded synchronised region. A multi-step design procedure is given for constructing such an inner-linking matrix, which maintains a favourable decoupling property. Furthermore, the global H _∞ synchronised region is characterised for evaluating the performance of a Lur'e network subject to external disturbances. The effectiveness of the theoretical results is demonstrated through a network of Chua's circuits.     

基于模式切换的有源无源一体化跟踪算法研究

针对传统目标跟踪算法缺乏灵活性,不能满足复杂环境下目标连续跟踪的缺点,探讨了网络雷达不同工作模式下,接收站获取目标运动状态参数不同集合对目标跟踪精度的影响,提出了基于模式切换的有源无源一体化跟踪算法,该算法可根据接收站的不同需求灵活选择有源无源等不同的定位跟踪方式。采用UKF算法对不同模式切换下的目标跟踪精度进行分析,仿真结果表明,该算法能够有效利用前一阶段的滤波跟踪结果,可在复杂的环境下保持对目标的连续跟踪。     

Conceptual digital twin modeling based on an integrated five-dimensional framework and TRIZ function model

Digital twin represents a fusion of the informational and physical domains, to bridge the material and virtual worlds. Existing methods of digital twin modeling are mainly based on modular representation, which limits guidance of the modeling process. Such methods do not consider the components or operational rules of the digital twin in detail, thereby preventing designers from applying these methods in their fields. With the increasing application of digital twin to various engineering fields, an effective method of modeling a multi-dimensional digital twin at the conceptual level is required. To such an end, this paper presents a method for the conceptual modeling of a digital twin based on a five-dimensional digital twin framework to represent the complex relationship between digital twin objects and their attributes. The proposed method was used to model the digital twin of an intelligent vehicle at the concept level.     

Global exponential synchronization for coupled switched delayed recurrent neural networks with stochastic perturbation and impulsive effects

This paper focuses on the hybrid effects of stochastic perturbation, system switching, state delays and impulses on neural networks. Based on the Lyapunov functional method, switching analysis techniques, the comparison principle and a new impulsive delay differential inequality, we derive some sufficient conditions which depend on delay and impulses to guarantee the exponential synchronization of the coupling delay switching recurrent neural networks with stochastic perturbation. Simulation results finally demonstrate the effectiveness of the theoretical results.     

Learning analysis strategies for octagon and context sensitivity from labeled data generated by static analyses

We present a method for automatically learning an effective strategy for clustering variables for the Octagon analysis from a given codebase. This learned strategy works as a preprocessor of Octagon. Given a program to be analyzed, the strategy is first applied to the program and clusters variables in it. We then run a partial variant of the Octagon analysis that tracks relationships among variables within the same cluster, but not across different clusters. The notable aspect of our learning method is that although the method is based on supervised learning, it does not require manually-labeled data. The method does not ask human to indicate which pairs of program variables in the given codebase should be tracked. Instead it uses the impact pre-analysis for Octagon from our previous work and automatically labels variable pairs in the codebase as positive or negative. We implemented our method on top of a static buffer-overflow detector for C programs and tested it against open source benchmarks. Our experiments show that the partial Octagon analysis with the learned strategy scales up to 100KLOC and is 33\(\times \) faster than the one with the impact pre-analysis (which itself is significantly faster than the original Octagon analysis), while increasing false alarms by only 2%. The general idea behind our methodis applicable to other types of static analyses as well. We demonstrate that our method is also effective to learn a strategy for context-sensitivity of interval analysis.     

Global optimization by coupled local minimizers and its application to FE model updating

Coupled local minimizers (CLM) is a new method applicable to global optimization of functions with multiple local minima. In CLM a cooperative search mechanism is set up using a population of local optimizers, which are coupled during the search process by synchronization constraints. CLM is characterised by a relative fast convergence since the local optimizers are gradient-based. The combination of both, the coupled parallel strategy and the fast convergence, offers an efficient global optimization algorithm. In the paper the CLM method is described and is illustrated with a test function. Due to the simultaneous and coupled search of a whole population of optimizers, CLM is able to find the global minimum of the test function. Next, CLM is successfully applied to FE model updating using experimental modal data. In an example the damage pattern of a reinforced concrete beam is identified.     

Global dynamics of two coupled parametrically excited van der Pol oscillators

Using a combination of analytical and numerical methods, the global bifurcations and chaotic dynamics of two non-linearly coupled parametrically excited van der Pol oscillators are investigated in detail. With the aid of the method of multiple scales, the slow flow equations are obtained. Based on the slow flow equations, normal form theory and the techniques of choosing complementary space are applied to find the explicit expressions of the simpler normal form associated with a double zero and a pair of pure imaginary eigenvalues. By the simpler normal form, using the global perturbation method developed by Kovacic and Wiggins, the analysis of global bifurcation and chaotic dynamics of two non-linearly coupled parametrically excited van der Pol oscillators is given. The results indicate that there exists a Silnikov type single-pulse homoclinic orbit for this class of system which implies the chaotic motions can occur. Numerical simulations are also given and verify the analytical predictions.     

Global asymptotical synchronisation in linearly coupled networks of RCL-shunted Josephson junctions

This article presents the synchronisation criteria for a class of dynamical networks with each node being resistively-capacitively-inductively-shunted (RCL-shunted) Josephson junction, which guarantee the synchronised states to be global asymptotically stable. These conditions are established in terms of linear matrix inequalities (LMIs), readily solvable by available numerical software. In addition, an interesting conclusion is reached that the stability of synchronisation in the coupled whole 3N-dimensional networks can be converted into that of 3-dimensional space.     

Enabling technologies and tools for digital twin

Digital twin is revolutionizing industry. Fired by sensor updates and history data, the sophisticated models can mirror almost every facet of a product, process or service. In the future, everything in the physical world would be replicated in the digital space through digital twin technology. As a cutting-edge technology, digital twin has received a lot of attention. However, digital twin is far from realizing their potential, which is a complex system and long-drawn process. Researchers must model all the different parts of the objects or systems. Varied types of data needed to be collected and merged. Many researchers and participators in engineering are not clear which technologies and tools should be used. 5-dimension digital twin model provides reference guidance for understanding and implementing digital twin. From the perspective of 5-dimension digital twin model, this paper tries to investigate and summarize the frequently-used enabling technologies and tools for digital twin to provide technologies and tools references for the applications of digital twin in the future.     

From simple digital twin to complex digital twin Part I: A novel modeling method for multi-scale and multi-scenario digital twin

In recent years, the digital twin has attracted widespread attention as an important means of digitalization and intelligence. However, the digital twin is becoming more and more complex due to the expansion of need on the simulation of multi-scale and multi-scenario in reality. The instance of digital twin in references mostly concentrates a particular application, while it is still a lack of a method for constructing the complex digital twin in the total elements, the variable scale of working environments, changeable process, not even the coupling effects. In this paper, a novel modeling method for such a complex digital twin is proposed based on the standardized processing on the model division and assembly. Firstly, the complex model of digital twin is divided into several simple models according to the composition, context, component, and code in 4C architecture. Composition and context make the digital twin focus on the effective elements in a specific scale and scenario. Component and code develop the digital twin in standard-based modularization. Secondly, assemble the simple models of digital twins into the complex model through information fusion, multi-scale association and multi-scenarios iterations. Ontology establishes the complete information library of the entities on different digital twins. Knowledge graph bridges the structure relationship between the different scales of digital twins. The scenario iterations realize the behavior interaction and the accuracy calculation results. It provides an implementable method to construct a complex model of digital twin, and the reuse of components and code also enables rapid development of digital twins.     

Microfluidic chips for capillary electrophoresis with integrated electrodes for capacitively coupled conductivity detection based on printed circuit board technology

A simple and low budget microfabrication method compatible with mass production was developed for the integration of electrodes for capacitively coupled contactless conductivity detection (C4D) in Lab on a Chip devices. Electrodes were patterned on a printed circuit board using standard processing. This was followed by lamination-photolithography-lamination to cover the electrodes in dry film photoresist (DFR) using an office laminator. This resulted in a flush, smooth surface on top of the detection electrodes, enabling subsequent integration of a microfluidic network at a distance dictated by the thickness of the DFR (17 μm, 30 μm and 60 μm were used in this work). This process was applied to create two types of detectors, re-usable detectors to be used in combination with a separate microfluidic network and integrated detectors where the microfluidic network is irreversibly sealed to the detector. A poly(dimethylsiloxane) (PDMS) slab containing the microfluidic network was positioned on top of the re-usable detectors to create the PDMS hybrid devices. The integrated DFR devices were created by patterning and sealing the microchannel in DFR using subsequent lamination and lithographic steps. The sensitivity of the C4D made using this new technology for small inorganic cations was between 6 and 20 μM, which is comparable with devices made using significantly more advanced technologies. Where the 17 μm film slightly improved the sensitivity, the use of 30 μm thick insulating films was preferred as these did not impose significant restrictions on the applicable field strengths.     

Toward self-describing and workflow integrated Earth system models: A coupled atmosphere-ocean modeling system application

The complexity of Earth system models and their applications is increasing as a consequence of scientific advances, user demand, and the ongoing development of computing platforms, storage systems and distributed high-resolution observation networks. Multi-component Earth system models need to be redesigned to make interactions among model components and other applications external to the modeling system easier. To that end, the common component interfaces of Earth system models can be redesigned to increase interoperability between models and other applications such as various web services, data portals and science gateways. The models can be made self-describing so that the many configuration, build options and inputs of a simulation can be recorded. In this paper, we present a coupled modeling system that includes the proposed methodology to create self-describing models with common model component interfaces. The designed coupled atmosphere-ocean modeling system is also integrated into a scientific workflow system to simplify routine modeling tasks and relationships between these tasks and to demonstrate the enhanced interoperability between different technologies and components. Later on, the work environment is tested using a realistic Earth system modeling application. As can be seen through this example, a layered design for collecting provenance and metadata has the added benefit of documenting a run in far greater detail than before. In this way, it facilitates exploration and understanding of simulations and leads to possible reproducibility. In addition to designing self-describing Earth system models, the regular modeling tasks are also simplified and automated by using a scientific workflow which provides meaningful abstractions for the model, computing environment and provenance/metadata collection mechanisms. Our aim here is to solve a specific instance of a complex model integration problem by using a framework and scientific workflow approach together. The reader may also note that the methods presented in this paper might be also generalized to other types of Earth system models, leading to improved ease of use and flexibility. The initial results also show that the coupled atmosphere-ocean model, which is controlled by the designed workflow environment, is able to reproduce the Mediterranean Sea surface temperature when it is compared with the used CCSM3 initial and boundary conditions.