A Computational Framework for Cable Layout Design ...

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Physics Procedia 33 (2012) 1879 – 1885

2012 International Conference on Medical Physics and Biomedical Engineering

A Computational Framework for Cable Layout Design in Complex Products SHANG Wei, LIU Jian-hua, NING Ru-xin, LIU Jia-shun School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China e-mail: {shangwei, jeffliu, rxning, wh6816}@bit.edu.cn

Abstract The cable layout design in complex products has been challenging because of various strict constraints. In this paper, we present a computationalframework which provides a rich solution for the cable layout problems. The framework centers at the digital mockup of the product,and the digital model of the cable bundle in the productis introduced as an essential part. The design process in the framework is carried out in a virtual environment with a wide range of supporting techniques and tools integrated, including path planning techniques, physically-based model, assembly simulation techniques and more. The techniques and tools respectively emphasizeon different aspects in this problem domain. Besides, the designers play an important role in the framework. They drive the whole design process and make decisions with their knowledge on issues that current techniques cannot solve. A prototype system is developed and applied in practical product development process. The results show that the framework is practical and promising.

©2012 2011Published Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [name Committee. organizer] © by Elsevier B.V. Selection and/or peer review under responsibility of ICMPBE International Open access under CC BY-NC-ND license. Keywords-cable layout design; digital mockup; digital model of cable bundle;virtual assembly;path planning

1. Introduction Cables and wires are widely used in mechanical products to connect electronic devices and modules as the transmittersfor signal and power. In complex products like airplanes, satellites, etc., a mass amount of cables and wires are used in their electronic systems.While on the other hand, it has been challenging to design the cable layoutin such complex systems and have them properlyassembled to ensure the robustness of the whole system. The difficulties come froma wide range of strict constraints, e.g.: 1) due to the high assembly density inside these complex products, the available space for cables is very limited; 2)highly strict demand on electronic-magnetic capability; 3) dynamic cables attached to mechanisms need to be well designed to avoid collision and disturbing force/torque; 4)the product may work in severe environment like high

1875-3892 © 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of ICMPBE International Committee. Open access under CC BY-NC-ND license. doi:10.1016/j.phpro.2012.05.297

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temperature, high humidity, etc.; 5) assembly feasibility of the cable bundles and other parts may decrease in such products because of their complexity. The conventional cable layout design process is usuallycarried out on physical prototypes.Cable bundles are then fabricated and a series of experiments will bemade after assembly.The design process will be iterated based on the feedbackand thesolution is refined tomeet the design demands and constraints.The whole process is time consuming and costly. Now cable routing modules are provided in some CAD systems, but most of them solve no more than the geometry based layout design problem. More evaluation for other constraints cannot be accomplished in the CAD systems.Further researches are conducted or ongoing now, includingautomaticapproaches for cable layout design ([1][2][7]), cable simulation ([3][4]), assembly simulation ([5][6]), etc. In this paper, we propose a framework which provides a rich solution for the cable layout problem. The framework integrates a series of techniques focusing on different aspects in this problem domain, and meanwhile we value the knowledge of human as an important factor.Key techniques are implemented and a prototype system is developed and applied in practical product development process. The rest of the paper is organized as follows. Previous work related to our research are summarized in section II. In section III, the framework and key techniques are presented.In section IV, we show the implementation and applications of the system. At last, conclusions are made and future work is proposed. 2. Related work There are lots of challenging problems in the cable layout design and assemblyprocess. Various researches are published on different issues in this problem domain. In [1], an approach to providing computational support for concurrent design is discussed in the context of an industrial cable harness design problem.An architecture is presented in which the main design tasks are supported by agents – asynchronous and semiautonomous modules that automate routine design tasks and provide specialized interfaces for working on particular aspects of the design. Reference [2] describes a system for automatically routing cable harness in 3D environment using a pair of genetic algorithms.Sampling based motion planning algorithm is employed in [7] for cable route planning. All of them try to solve the cable harness routing problem with automatic algorithms. Reference [3] shows an approach based on kinematics for real-time simulation of cables. Reference [4] presents the assembly simulation for rigid bodies in products and the extension of real-time simulation of flexible cables in virtual environment. These researches are focused on simulatingthe flexibility of the cables. The researches presented in [5] and [6] mainly focus on the assembly simulation and assembly process planning of the cable harness in products. 3. The framework and key techniques 3.1 An overview of the framework We design and implement the framework based on the philosophy as follows: The information source of the framework is the digital mockup, which is highly enriched with all possible information that describes the product. The digital model of the cables in product is an essential part. Multiplesupporting techniques and tools are integrated based on the digital mockup. Designers play a vital part in the framework. They drive the iterated design process and evaluate the result and intermediate result with the assistance of the computational tools.

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The framework is illustrated in Fig. 1. The input of the framework is the design demands and constraints. The iterated design process is carried out with the supporting techniques and tools. The design result will be outputted when it is evaluated to meet the input, in the forms of 3D models, connection charts, BOMs and more that support the later phases in the product development process. With an implemented system based on this computational framework, most of the cable layout design process will be conducted on the digital mockup.

Figure 1. The framework for cable layout design in complex products

The basis and information source of the framework is the digital mockup of the product, which hasthe digital model of the cables as an essential part. The digital mockup, which should provide as much possible information as a physical mockup does, is constructed based on the CAD model and more engineering information. The digital model of the cable harness should be able to represent all the wires, cables and harnesses created in the design process in all possible aspects including electronic connection, routing path, geometry, etc.All the activities related to design, evaluation and refinement in the process are carried out interacting with the digital mockup. Techniques and toolsemphasizing on different aspects in the problem domain are integrated in the framework. These techniques and tools are built in various disciplines for different specific problems, e.g., we implement the path planner for automatic routing with path planning techniques from robotics, and the simulation of dynamic cables is based on mechanics related disciplines. Technically, all the related activities carried out with the support of these techniques and tools are actually reading, analyzing and modifying the information in the digital mockup, which is centered in the framework. Human-beings play an important role in this framework. The whole process involves a series of activities that current techniques and tools have very limited capability to support, e.g., cooperation between designers and other working people from different departments, the decision making in the process, etc. Thus, the involved people need to drive the process with the assistance of the supporting techniques and tools. 3.2 The Digital Model of the Cable Bundle

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There aree plenty of teechniques on the constructtion and appliication of diggital mockup proposed and d implementedd,however, most m of them mainly focuss on assembly y related probblems and haave very littlee concern aboout the cable related r problem ms. In this paart, we will present the digital model of tthe cables and d the supportinng techniquess employed in the design prrocess. We desiggn the digital model m of the cables c with tw wo major princciples: Thee model contaains as much innformation as possible to deescribe the cabble bundle. Enssure the easy interactionbetw i ween the moddel and all otheer activities in the design proocess. In practiical manufactuuring process,, cables and wires w used for connecting reelated devicess and moduless are usually bundled togetther as one siingle part for assembly. Th he structure of o the bundle is sometimess mplex, in whichh case the lay yout design is challenging.F Fig. 2 shows a simple, whille sometimes becomes com physical cabble bundle usedd in product development. d

Figure 2. A phyysical cable bunddle

Figure 3. Primiitive elements in the t cable model

To descrribe such bundles, we desiign some prim mitive elemen nts and compoose the bundlle model with h such simplee elements. Thhe basic modeel describes thhe topologicallstructure of the t cable bunddle, and moree information can be affixed on the primiitive elementss to enrich thee model.The prrimitive elemeents we use in n the model innclude: 1) Cabble bundle:coorresponds to a physical cable c bundle and a includes the informatiion of all thee organized caables and wirees. (A in Fig. 3.) 3 2) Bunndle segment: represents a maximum m section with no crotchin c the caable bundle. (B B in Fig. 3.) 3) Conntrol point:thhere are three kinds of conntrol points in n this model,, a) frontier ppoints, which h represent thee ends of the bundle, b b) crootch points, whhich representt the crotches, and c) interm mediate points,, which are thhe restinterpolaated points. (R Respectively C1, C C2, C3 in Fig. F 3.) A cable bundle b is com mposed with onne or more buundle segmentts, and a bunddle segment inncludes two orr more controol points.Fig. 3 illustrates a visualized buundle model co omposed of thhe primitive eelements. Now w we are able to describe the t topologicaal structure off the cable bu undle with orgganized primittive elements.

Shang Wei et al. / Physics Procedia 33 (2012) 1879 – 1885

We take the topological model as the core of the bundle model, and will later affix more information to enrich the model. The primitives in the modelare organized in two forms: by a tree, or by a graph.If the model is represented by a tree shown in Fig. 4, it is easier to construct and modify. When the model is organized in a graph in the form of its adjacency matrix, which is shown in Fig. 5, it is easier to search some specific connection paths in the bundle via graph algorithms. Thus we have the two forms in the bundle model for different purpose in the working process and always keep them consistent.

Figure 4. Tree representation of the cable bundle

(a) The cable bundle

(b) The primitive elements

x1 x2 x3 x4

x1 x 2 x3 x 4 0 1 0 0 1 0 1 1 0 1 0 0 0 1 0 0

(c) The adjacency matrix

Figure 5. Graph representation of a cable bundle

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We affix more information on the topological model to describe the cable bundle. The routing paths are represented with position information on control points. Information on electronic connection and used cables or wires is attached on bundle segments. We can traverse the tree or search the graph for specific points, bundle segments, or connection paths and acquirethe information on them for later operations. 3.3 Integrated Techniques We employ various techniques and tools in the framework for design, simulation, evaluation,optimization and other purposes. Path planning algorithms in 3D space are used in path planner module for automatic routing. Physically based model is constructed for dynamic cable simulation. This process helps to find potential problems in the cables attached to mechanisms. Assembly simulator is used to evaluate the assembly feasibility and form the assembly plan.The framework is extendable and new techniques can be introduced to solve other problems. 4. Implementation and applications We implemented the framework on a virtual assembly platform referred as “Virtual Assembly Process Planning System”, which can provide the digital mockup of products with rich information, as shown previously in figure 1, and a virtual environment for design and manufacturing related activities. The digital model of cables is addedas another essential part in the digital mockup, and various supporting modules are integrated. In the system, we enable designers to construct the cable bundle, theninteractively define the route, or automatically search the route and refine it. Electronic connections and cables used in connections can be defined on the bundle. After the layout design is finished, assembly simulation and dynamic simulation can be carried out to validate if the result meets the design demands and constraints and provide suggestions on possible further refinement. The system is applied in practical engineering problems to assist designers to accomplish the cable layout design on digital mockup. Fig. 6(a) and Fig. 6(b) respectively show an ongoing cable layout design and an outputted 3D model of the result.The feedbacks from the designers show that the system is useful in the cable layout design process and enable them to fully or partially get rid of physical mockups. The product development process is speeded up and the cost is lowered.

(a) Cable layout designbased on the digital mockup Figure 6. Applications of the prototype system

(b) The 3D model result

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5. Conclusions and future work In this paper, we presented a computational framework for cable layout design problems in complex products. The basis and information source of the framework is the enriched digital mockup of the product. Additional, we design and implement the digital model of the cable bundle as an essential part of the digital mockup. Multiple techniques and tools emphasizing on different problems are integrated in the framework to enable designers to design, evaluate and refine the cable layout solution. Human-beings play an import role to drive the working process and make decisions that the current techniques cannot do. We highlight the framework with the digital model of the cable bundle, and the rich solution for different challenging problems in the design process.A prototype system is implemented and applied in engineering problem. The results show that the framework is practical and promising. However, technically, some algorithms and techniques employed in the framework still need further improvement in the future to acquire better performance. And the framework can be extended with new techniques introduced to enhance its capability.

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Hisup Park, Mark R. Cutkosky, Andrew B. Conru and Soo-Hong Lee (1994). An agent-based approach to concurrent cable harness design. Artificial Intelligence for Engineering, Design, Analysis and Manufacturing, 8, pp 45-61, doi:10.1017/S0890060400000457

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Conru, A.B.; , "A genetic approach to the cable harness routing problem," Evolutionary Computation, 1994. IEEE World Congress on Computational Intelligence., Proceedings of the First IEEE Conference on , vol., no., pp.200-205 vol.1, 2729 Jun 1994, doi: 10.1109/ICEC.1994.350016

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