Designing a family of reconfigurable vehicles using multilevel multidisciplinary design optimization

Continuous advancements in technology have resulted in customers expecting enhanced performance across multiple operating conditions. In this paper, the desire to meet a variety of objectives after the system has been deployed is accomplished through the design of reconfigurable systems. However, permitting a system to adapt increases both complexity and cost. If this increase is too large, only a subset of design variables can be made adaptable. A multilevel multidisciplinary design optimization (MDO) approach is presented to determine the core architecture for a family of three reconfigurable vehicles when accommodating a changing number of adaptable design variables. To illustrate this approach, a case study involving a three-driver racing team is introduced. A common architecture is determined for the three vehicle variants, resulting in lap-time performance increases of 2.08%, 3.27%, and 3.67% when compared to the static, optimized baseline vehicle. The results of this study demonstrate the effectiveness of combining reconfigurability with product platforming and MDO. This paper is based on AIAA paper AIAA-2007-1880 that was reviewed for, and presented at, the 48th AIAA/ASMR/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference.     

Scalability planning for reconfigurable manufacturing systems

Scalability is a key characteristic of reconfigurable manufacturing systems, which allows system throughput capacity to be rapidly and cost-effectively adjusted to abrupt changes in market demand. This paper presents a scalability planning methodology for reconfigurable manufacturing systems that can incrementally scale the system capacity by reconfiguring an existing system. An optimization algorithm based on Genetic Algorithm is developed to determine the most economical way to reconfigure an existing system. Adding or removing machines to match the new throughput requirements and concurrently rebalancing the system for each configuration, accomplishes the system reconfiguration. The proposed approach is validated through a case study of a CNC-based automotive cylinder head machining system.     

Sequential optimization and reliability assessment for multidisciplinary systems design

With higher reliability and safety requirements, reliability-based design has been increasingly applied in multidisciplinary design optimization (MDO). A direct integration of reliability-based design and MDO may present tremendous implementation and numerical difficulties. In this work, a methodology of sequential optimization and reliability assessment for MDO is proposed to improve the efficiency of reliability-based MDO. The central idea is to decouple the reliability analysis from MDO with sequential cycles of reliability analysis and deterministic MDO. The reliability analysis is based on the first-order reliability method (FORM). In the proposed method, the reliability analysis and the deterministic MDO use two MDO strategies, the multidisciplinary feasible approach and the individual disciplinary feasible approach. The effectiveness of the proposed method is illustrated with two example problems.     

支持多学科设计优化的集成产品过程建模方法

针对当前主要的设计过程建模方法缺乏表达复杂产品多学科设计过程中资源的组织调用和协作方式等信息,提出一种支持复杂产品多学科设计优化的设计路线图框架过程建模方法.从全面表达设计过程信息的角度出发,描述产品多学科设计优化过程中的主要活动及其协同关系,建立支持多学科设计优化的过程模型;在此基础上,给出了多学科设计优化的过程规划方法,以降低产品设计过程中的迭代,通过构建支持多学科设计优化的集成产品设计过程结构框架,实现产品多学科设计优化的过程集成.最后通过已开发的多学科系统集成平台,应用具体设计实例验证了整套方法的有效性.     

Development of an automated flexible fixture for planar objects

A three fingered automated flexible fixturing system has been developed to fixture planar objects in a machining process. The fixturing system consists of two computer numerically controlled (CNC) modules, an auxiliary mechanism and a fixturing algorithm. This fixture is designed on the idea of the minimum number of fingers needed to immobilise an object. The fixturing algorithm is developed on the concept of the maximal inscribed circle in a polygon. It offers the flexibility to reconfigure the fingers of the system to accommodate workpieces of different shapes and sizes. A prototype of the system has been successfully built and tested, showing satisfactory performance in mechanical design and automatic control over the configurations of the fingers. Examples are given of the application of the system with objects of different shapes. The system is shown to be flexible, reconfigurable and automatic, capable of fixturing planar objects of different shapes and sizes in the machining process.     

Multi-Criteria Optimization of a Hexapod Machine

Alternative designs of a hexapod machine are proposed and investigated with the aims to reduce flexibility and to eliminate singular kinematic configurations that appear in the workspace for the current design of the machine. The hexapod is modeled as a rigid multibody system. Articular coordinates associated with desired tool trajectories are computed by inverse kinematics. Hence, dynamic forces and torques are not considered and, as there is no closed-loop control realized in the model, the actual rotational and translational position of the tool deviates from the desired position due to machining loads. These deviations serve as objective functions during a multi-criteria optimization in order to determine the best design regarding stiffness/flexibility of the machine. Further, a general approach for evaluating flexibility behavior of the machine in the complete workspace is introduced and the results from the optimization are verified. Besides flexibility, a crucial point for machining tools is the size of the feasible workspace. Therefore, the influence of the design modification on the workspace is also taken into account.     

An efficient strategy for multidisciplinary reliability design and optimization based on CSSO and PMA in SORA framework

The conventional reliability-based multidisciplinary design optimization (RBMDO) integrates the reliability-based design optimization and multidisciplinary design optimization (MDO) directly, which leads to a triple-level nested optimization loop. Especially, the multidisciplinary reliability analysis in the middle layer dominates the whole efficiency of RBMDO. To tackle this problem, first of all, a sequential multidisciplinary reliability analysis (SMRA) approach that integrates the concurrent subspace optimization (CSSO) strategy and the performance measure approach is proposed, in which the multidisciplinary analysis, system sensitivity analysis and reliability analysis are decoupled and arranged sequentially, making a recursive loop. The multidisciplinary analysis and system sensitivity analysis provide the value and gradient information of limit-state function for reliability analysis respectively. As a result, a great number of repeated iterations of the whole reliability analysis are eliminated. Secondly, the CSSO has been integrated with the sequential optimization and reliability assessment (SORA) to decouple the triple-level nested RBMDO procedures into a sequence of cycles of deterministic MDO and multidisciplinary reliability analysis. Therefore, the expensive computation of the whole reliability analysis model in each iteration of RBMDO is avoided. And also, the CSSO is adopted in the deterministic MDO to deal with medium-scale and coupled multidisciplinary systems. The procedures of the proposed approaches are presented in detail. The effectiveness of the proposed strategies is demonstrated and verified with two design examples.     

可重构制造系统监督控制器的自动重构

提出了基于改进的网重写系统(Improved net rewriting system, INRS)的可重构制造系统(Reconfigurable manufacturing systems, RMS) Petri网监督控制器的自动重构方法, 以快速适应由市场需求变化所引起的制造系统构形的频繁变化. INRS解决了网重写系统存在的问题, 可动态调整给定Petri网模型的结构而不改变其行为属性. 以集合和图的组合形式定义了RMS的构形, 并提出了基于INRS的一类模块化、可重构的Petri网控制器的设计方法. 针对这类Petri网控制器, 提出了基于INRS的自动重构方法. 方法可将RMS构形的变化转变为INRS的图重写规则, 并作用于当前Petri网控制器, 使其快速、自动地重构为所求的新控制器. 所提出的Petri网控制器的设计与重构方法, 均从理论上保证了结果的正确性, 免校验. 仿真研究验证了方法的有效性.     

一种模块化可重构机器人系统的研制

在教育和科研领域中,为使机器人兼有较好的重构能力与操作性能,研制了一种模块化可重构机器人系统MRRES.提出了一种机器人模块划分及重构的方法,构建出机器人模块库,研制出集成传动、控制及传感于一体的系列化关节模块.基于Open GL和VC++开发了具有建模、仿真和运动控制功能的应用软件MRR-SIM.给出了一个基于任务和模块库的机器人设计实例,进行了实验测试.实验结果表明,MRRES系统模块划分和设计合理,机器人在保证重构能力的同时具有较好的操作性能,可应用于教育和科研等领域.     

Configuration representation and reconfiguration optimization for the reconfigurable robots with independent manipulation

Single module of the reconfigurable robots with independent manipulation can perform the actions of locomotion and manipulation. In conformity with the request for achieving autonomous operation in the unstructurized environment instead of fixed operation in the structurized environment, these robots are applied in the complicated and dangerous environment. The existing researches on the configuration theory focus on the reconfigurable robots with limited locomotion and the ones with independent locomotion, not being applicable to the reconfigurable robots with independent manipulation. The vector configuration is put forward, the research content of which contains the topology and locomotion direction of configuration, the posture and orientation and connection relation between modules. Module state vector and configuration state matrix are proposed for representation methodology for the swarm configuration of these reconfigurable robots, which supports transformation operation to represent and trigger behavior motion of the module and reconfiguration between configurations. Optimization algorithm of assembly reconfiguration applying workload as the optimization target is presented, as well as optimization algorithm of transformation reconfiguration applying the integration of posture orientation workload and connection workload. The result of optimization is the relation of state transformation between the initial configuration and the object one as the basic of reconfiguration plan and control. Supported by the National High-Tech Research and Development Program of China (Grant No. 2006AA04Z254) and the Scientific Research Fund for Doctor of Liaoning Provice (Grant No. 20071007)     

Modular Design of a Reconfigurable Electromagnetic Robot

This paper discusses the modular design of distributed reconfigurable robots. The design concept, mechanical structure, electrical processing unit, actuator dissection and reconfiguration examples of the proposed robotic modules are presented in detail. The reconfigurable robotic motion is realized via a collection of the proposed modules with the capability of connecting and disconnecting with adjacent modules. The key actuation of the robotic reconfiguration is driven only by the E-type electromagnets and different shapes of the modules are implemented for versatile applications. Finally, the feasibility of the proposed robotic modules has been extensively tested.     

Multidisciplinary aerospace design optimization: survey of recent developments

The increasing complexity of engineering systems has sparked rising interest in multidisciplinary optimization (MDO). This paper surveys recent publications in the field of aerospace, in which the interest in MDO has been particularly intense. The primary c hallenges in MDO are computational expense and organizational complexity. Accordingly, this survey focuses on various methods used by different researchers to address these challenges. The survey is organized by a breakdown of MDO into its conceptual components, reflected in sections on mathematical modelling, approximation concepts, optimization procedures, system sensitivity, and human interface. Because the authors' primary area of expertise is in the structures discipline, the majority of the references focus on the interaction of this discipline with others. In particular, two sections at the end of this review focus on two interactions that have recently been pursued with vigour: the simultaneous optimization of structures and aerodynamics and the simultaneous optimization of structures with active control.     

Rapid design and reconfiguration of Petri net models for reconfigurable manufacturing cells with improved net rewriting systems and activity diagrams

To respond rapidly to the highly volatile market, the emerging reconfigurable manufacturing systems (RMS) have brought forward two challenging issues, namely, how to build rapid a formal model of an initial manufacturing configuration and how to yield the goal model from the existing one along with manufacturing configuration changes (reconfiguration). As for the issues, we present in this paper a method for rapid design of Petri net (PN) formalized models of RMS, intended for supervisory control and logic control of RMS, as well as a method for automated reconfiguration of the models. Firstly, we present an improved net rewriting system (INRS) for dynamically operating net transformation, unlike its predecessor-net rewriting system, where the initial behavioral properties of the underlying PN rewritten can be preserved during the transformation. Subsequently, the paper proposes the three-phase method for rapid design of initial full PN models of reconfigurable manufacturing cells (RMCs). In this method, activity diagrams of Unified Modeling Languages version 2 (UML 2) are used to describe manufacturing configurations, firstly; then the sub-activity diagrams are transformed into PN sub-models; finally, the PN sub-models are automated synthesized into a full model by the approach of INRS. Further, we present a model reconfiguration method for this class of PN models. The method compares changes in activity diagrams of the existing and goal manufacturing configurations and converts them into net rewriting rules of INRS. By applying the rules obtained, the existing PN model can reconfigure into a new one for the goal manufacturing configuration. No matter the design method or the reconfiguration method, the behavioral properties of the obtained PN models, e.g., liveness, boundedness, or reversibility, can be guaranteed and thereby the efforts of verification can be avoided. Finally, rapid design of a PN model of a reconfigurable manufacturing cell, as well as its automated reconfiguration, is illustrated with the help of an example. The result indicates the validity of the methods.     

卫星有效载荷的多目标多学科设计优化研究

在卫星有效载荷系统研究中,实施多目标多学科优化的可行性设计。首先,分析了开展卫星有效载荷多学科设计优化的关键技术。建立了包含天线、转发器、数据传输、可靠性、成本和质量的多学科分析模型。然后,应用多目标遗传算法对某卫星有效载荷的可靠性和成本进行多目标设计优化,获得最优解集。最后,运用多学科协同优化结合遗传算法进行可靠性单目标设计优化。研究结果表明:有效载荷的多目标多学科设计优化全面考虑了多个学科之间的关系,设计人员可按需选择其满意的优化结果,大幅提高设计效率;协同优化方法有助于实现学科自治、并行设计,提高设计的灵活性和缩短设计周期。     

Dynamic Analysis and Distributed Control of the Tetrobot Modular Reconfigurable Robotic System

Reconfigurable robotic systems can be adapted to different tasks or environments by reorganizing their mechanical configurations. Such systems have many redundant degrees of freedom in order to meet the combined demands of strength, rigidity, workspace kinematics, reconfigurability, and fault tolerance. In order to implement these new generations of robotic system, new approaches must be considered for design, analysis, and control. This paper presents an efficient distributed computational scheme which computes the kinematics, dynamics, redundancy resolution, and control inputs for real-time application to the control of the Tetrobot modular reconfigurable robots. The entire system is decomposed into subsystems based on a modular approach and Newton's equations of motion are derived and implemented using a recursive propagation algorithm. Two different dynamic resolution of redundancy schemes, the centralized Jacobian method and the distributed virtual force method, are proposed to optimize the actuating forces. Finally, distributed dynamic control algorithms provide an efficient modular implementation of the control architecture for a large family of configurations.     

计算机辅助可重构制造系统设计

可重构制造系统是为了快速而准确地提供响应新的高层需求所需的生产能力和生产同一零件族内的新零件所需的制造功能，从一开始就设计成可面向系统级和生产资源级快速而又以有竞争力的成本重构的制造系统，文中分析了可重构制造系统的设计方法及其特征，提出了计算机辅助可重构制造系统设计这一新的研究方向，说明了包括动态适应学习识别机制，建模分析与性能优化，专家系统、集成设计等模块的设计机辅助可重建制造系统设计的流程，实现了可重构制造系统的集成设计。     

基于SOPC的可穿戴计算机动态重构模块设计与实现

针对可穿戴计算机任务的多变性及多样性,研究通过动态重构技术和SOPC设计方法两者相结合来制造适合可穿戴计算机的动态重构方式,同时对基于SOPC的可穿戴计算机动态重构模块进行了设计与实现．．     

Development of a multidisciplinary design optimization test simulator

Many of the method development efforts in the field of multidisciplinary design optimization (MDO) attempt to simplify the design of a large, complex system by dividing the system into a series of smaller, simpler, and coupled subsystems. A representative and efficient means of determining the feasibility and robustness of MDO methods is crucial. This paper describes the construct and applications of a test simulator, CASCADE (Complex Application Simulator for the Creation of Analytical Design Equations), that is capable of randomly generating and then converging a system of coupled analytical equations, of user-specified size (Hulme and bloebaum 1996). CASCADE-generated systems can be used for test sequencing and system reduction strategies, convergence strategies, optimization techniques, MDO methods, and distributed computing techniques (via Parallel Virtual Machine), among others.