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Unsupervised Dynamic Fuzzy Cognitive Map

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Tsinghua Science and Technology 2015年第3期20卷 285-292页

作者： Boyuan Liu Wenhui Fan Tianyuan Xiao Department of Automation Tsinghua University

Fuzzy Cognitive Map （FCM） is an inference network, which uses cyclic digraphs for knowledge representation and reasoning. Along with the extensive applications of FCMs, there are some limitations that emerge due to the deficiencies associated with FCM itself. In order to eliminate these deficiencies, we propose an unsupervised dynamic fuzzy cognitive map using behaviors and nonlinear relationships. In this model, we introduce dynamic weights and trend-effects to make the model more reasonable. Data credibility is also considered while establishing a machine learning model. Subsequently, we develop an optimized Estimation of Distribution Algorithm （EDA） for weight learning. Experimental results show the practicability of the dynamic FCM model. In comparison to the other existing algorithms, the proposed algorithm has better performance in terms of convergence and stability.

关键词： Fuzzy Cognitive Map （FCM） Estimation of Distribution Algorithm （EDA） nonlinear relation machinelearning

Synergic Motion Trajectory Planning for Airplane Docking Based on6PURU Parallel Mechanism

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Tsinghua Science and Technology 2015年第2期20卷 188-199页

作者： Hui Li Linxuan Zhang Tianyuan Xiao Jietao Dong State CIMS Engineering Research Center at Tsinghua University

Motion planning issues encountered in assembling airplanes by employing the 6PURU parallel mechanism are analyzed in this paper. A sine curve of the change rate of acceleration, which is called as jerk in the following text, is proposed for uniaxial flexible acceleration and deceleration planning based on the optimal time and velocity and acceleration constraints. Compared with other curves, the proposed curve can realize a continuous n-order derivative and the smooth change of the speed and acceleration. The method is computational^y simple and suitable for programming. In addition, a multiaxial coordinated movement scheme is proposed. The motion trajectory is no longer simply split into many single-direction trajectories nor are all single-direction planning trajectories combined directly. The multiaxial coordinated movement scheme aims to achieve synergic movement in multiple directions to ensure smoothness of the movement in the event of a kinematic error when maintaining a stable value. If the movement fails to achieve this goal, driving force mutations will deteriorate the effect of synergic movement. A physical model of the parallel mechanism is developed in simMechanics, and a holistic system model is completed in SIMULINK. The feasibility of the new planning algorithm is simulated and tested, and then, the multiaxial synergic movement planning method is proposed and verified.

关键词： assembly simulation motion trajectory planning parallel mechanism simMechanics

A dynamic delivery strategy for material handling in mixed-model assembly lines using decentralized supermarkets

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International Journal of Modeling, Simulation, and Scientific Computing 2015年第4期6卷 73-91页

作者： Jietao Dong Linxuan Zhang Tianyuan Xiao Hui Li National CIMS Engineering Research Center Tsinghua University Beijing 100084 P.R.China

Material handling has become one of the major challenges in modern production management.Consequently,this paper intends to investigate the part delivery of mixedmodel assembly lines with decentralized supermarkets and tow trains.Besides,uncertain exception disturbances,including tow train failures and adjustments of the production sequence,are also considered.To solve this problem,a heuristic-based dynamic delivery strategy is proposed,which dynamically schedules the route,departure time,quantities and types of loaded parts for each tour.To evaluate the performance of this strategy,it is used to solve an instance in comparison with the periodic delivery strategy,experimental results are reported and their performances are compared under different metrics.Moreover,a multi-scenario analysis is employed to determinate the long-term decisions,including the number of tow trains and the route layout.Finally,the critical storage is suggested to be set for each station to avoid part starvation resulting from disturbances,and its effect on the delivery performance is investigated.

关键词： Mixed-model assembly lines dynamic part delivery supermarket tow train critical storage.

Real-Time Control for CPS of Digital Airplane Assembly with Robust H-Infinity Theory

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Tsinghua Science and Technology 2015年第4期20卷 376-384页

作者： Hui Li Linxuan Zhang Tianyuan Xiao Jietao Dong State CIMS Engineering Research Cente at Tsinghua University

This study introduces a real-time controller design method under the effects of network time delay and external disturbance. The study first introduces the digital, virtual, intelligent trend of airplane assembly and reveals the status and problems of digital airplane assembly studies. The Cyber-Physical System （CPS） structure is then proposed for digital airplane assembly, and the real-time control issues are discussed. Then, the question of real- time control undertaken by a parallel robot is simplified to a control question with bounded time delay and complex interference, and a mathematical description is presented. Next, a robust Hoo controller with a disturbance degree of decay 7 is designed according to the mathematical description. Finally, a simulation is conducted. All of the experiment results show the feasibility of the above proposed methods.

关键词： cyber physical system network time delay robust H-infinity control linear matrix inequality

Data fusion and simulation-based planning and control in cyber physical system for digital assembly of aeroplane

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International Journal of Modeling, Simulation, and Scientific Computing 2015年第3期6卷 66-84页

作者： Hui Li Linxuan Zhang Tianyuan Xiao Jietao Dong State CIMS Engineering Research Center at Tsinghua University Main Building Room 604 Beijing 100084P.R.China State CIMS Engineering Research Center at Tsinghua University Main Building Room 601 Beijing 100084P.R.China State CIMS Engineering Research Center at Tsinghua University Main Building Room 619 Beijing 100084P.R.China

This paper introduces a CPS application for intelligent aeroplane assembly.At first,the CPS structure is presented,which acquires the characteristics of general CPS and enables“simulation-based planning and control”to achieve high level intelligent assembly.Then the paper puts forward data fusion estimation algorithm under synchronous and asynchronous sampling,respectively.The experiment shows that global optimal distributed fusion estimation under synchronized sampling proves to be closer to the actual value compared with ordinary weighted estimation,and multi-scale distributed fusion estimation algorithm of wavelet under asynchronous sampling does not need time registration,it can also directly link to data,and the error is smaller.This paper presents hybrid control strategy under the circumstance of joint action of the inner and outer loop to address the problems caused by the less controllable feature of the parallel mechanism when undertaking online process simulation and control.A robust adaptive sliding mode controller is designed based on disturbance observer to restrain inner interference and maintain robustness.At the same time,an outer collaborative trajectory planning is also designed.All the experiment results show the feasibility of above proposed methods.

关键词： Intelligent aeroplane assembly cyber physical system multi-sensor data fusion simulation-based control disturbance observer robust adaptive sliding mode controller

A parallel matching algorithm based on order relation for HLA data distribution management

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International Journal of Modeling, Simulation, and Scientific Computing 2015年第2期6卷 1-15页

作者： Yanbing Liu Hongbo Sun Wenhui Fan Tianyuan Xiao Department of Automation Tsinghua University BeijingP.R.China

In distribution simulation based on High-level architecture(HLA),data distribution management(DDM)is one of HLA services for the purpose of filtering the unnecessary data transferring over the network.DDM admits the sending federates and the receiving federates to express their interest using update regions and subscription regions in a multidimensional routing space.There are several matching algorithms to obtain overlap information between the update regions and subscription regions.When the number of regions increase sharply,the matching process is time consuming.However,the existing algorithms is hard to be parallelized to take advantage of the computing capabilities of multi-core processors.To reduce the computational overhead of region matching,we propose a parallel algorithm based on order relation to accelerate the matching process.The new matching algorithm adopts divide-and-conquer approach to divide the regions into multiple region bound sublists,each of which comprises parts of region bounds.To calculate the intersection inside and amongst the region bound sublists,two matching rules are presented.This approach has good performance since it performs region matching on the sublists parallel and does not require unnecessary comparisons within regions in different sublists.Theoretical analysis has been carried out for the proposed algorithm and experimental result shows that the proposed algorithm has better performance than major existing DDM matching algorithms.

关键词： High-level architecture data distribution management matching algorithm

AN EFFECTIVE WAY TO CONTROL CONGESTION FOR RTI WITH HYBRID ARCHITECTURE

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International Journal of Modeling, Simulation, and Scientific Computing 2014年第1期5卷 19-34页

作者： xiao BIN SUN HONGBO xiao tianyuan Department of Automation Tsinghua University Beijing 100084P.R.China Academy of Equipment Beijing 101416 P.R.China

Congestions brought by data explosion may suffer system performance or even cause fatal errors in large-scale simulation systems.This paper analyzes the reasons of generating congestion with queuing theory,and proposes a novel congestion control approach for RTI with hybrid architecture,including framework,sampling policy,queue length predicting,and congestion control algorithm.The framework promotes the usage of federate resources,and improves the performance of HLA simulation systems by dynamically distributing loads on RTIG and LRCs(Local RTI Components).At last,experimental results say that the proposed approach is a flexible,simple and efficient way to control congestion in RTI with hybrid architecture.

关键词： High Level Architecture(HLA) Run-Time Infrastructure(RTI) congestion control

Novel Models and Algorithms of Load Balancing for Variable-structured Collaborative Simulation under HLA/RTI

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Chinese Journal of Mechanical Engineering 2013年第4期26卷 629-640页

作者： YUE Yingchao FAN Wenhui xiao tianyuan MA Cheng State CIMS Engineering Research Center Tsinghua University

High level architecture(HLA) is the open standard in the collaborative simulation field. Scholars have been paying close attention to theoretical research on and engineering applications of collaborative simulation based on HLA/RTI, which extends HLA in various aspects like functionality and efficiency. However, related study on the load balancing problem of HLA collaborative simulation is insufficient. Without load balancing, collaborative simulation under HLA/RTI may encounter performance reduction or even fatal errors. In this paper, load balancing is further divided into static problems and dynamic problems. A multi-objective model is established and the randomness of model parameters is taken into consideration for static load balancing, which makes the model more credible. The Monte Carlo based optimization algorithm(MCOA) is excogitated to gain static load balance. For dynamic load balancing, a new type of dynamic load balancing problem is put forward with regards to the variable-structured collaborative simulation under HLA/RTI. In order to minimize the influence against the running collaborative simulation, the ordinal optimization based algorithm(OOA) is devised to shorten the optimization time. Furthermore, the two algorithms are adopted in simulation experiments of different scenarios, which demonstrate their effectiveness and efficiency. An engineering experiment about collaborative simulation under HLA/RTI of high speed electricity multiple units(EMU) is also conducted to indentify credibility of the proposed models and supportive utility of MCOA and OOA to practical engineering systems. The proposed research ensures compatibility of traditional HLA, enhances the ability for assigning simulation loads onto computing units both statically and dynamically, improves the performance of collaborative simulation system and makes full use of the hardware resources.

关键词： static load balancing dynamic load balancing variable-structure collaborative simulation under HLA/RTI multi-objective optimization ordinal optimization

A scenario relaxation algorithm for finite scenario based robust assembly line balancing

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High Technology Letters 2011年第1期17卷 1-6页

作者：徐炜达 xiao tianyuan Department of Automation Tsinghua University Beijing 100084 P . R. China

A balancing problem for a mixed model assembly line with uncertain task processing time and daily model mixed changes is considered, and the objective is to minimize the work variances between stations in the line. For the balancing problem for the scenario-based robust assembly line with a finitely large number of potential scenarios, the direct solution methodology considering all potential scenarios is quite time-consuming. A scenario relaxation algorithm that embeds genetic algorithm is developed. This new algorithm guarantees termination at an optimal robust solution with relatively short running time, and makes it possible to solve robust problems with large quantities of potential scenarios. Extensive computational results are reported to show the efficiency and effectiveness of the proposed algorithm. Copyright © by High Technology Letters Press.

关键词：松弛算法平衡问题装配生产线混合模型不确定性求解方法遗传算法运行时间