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Robot Path Planning for Wiring of Cable Harnesses

IP.com Disclosure Number: IPCOM000060719D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

Kurtzberg, JM: AUTHOR [+2]

Abstract

A cable harness consists of an assembly of wires of various types and colors, bundled together in a distinct shape and ready for insertion into a product, such as a computer frame. Industries, such as computer and electronic, aerospace, and automotive, spend considerable resources on cables. Usually the assembly is essentially flat, i.e., two-dimensional. The individual wires are known as leads and connect specified pins in terminator or connector devices. An important method of production is one in which all leads of a common type are strung together in one continuous operation, thus sharply reducing the amount of overhead involved in starting and stopping robot motion.

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Robot Path Planning for Wiring of Cable Harnesses

A cable harness consists of an assembly of wires of various types and colors, bundled together in a distinct shape and ready for insertion into a product, such as a computer frame. Industries, such as computer and electronic, aerospace, and automotive, spend considerable resources on cables. Usually the assembly is essentially flat, i.e., two-dimensional. The individual wires are known as leads and connect specified pins in terminator or connector devices. An important method of production is one in which all leads of a common type are strung together in one continuous operation, thus sharply reducing the amount of overhead involved in starting and stopping robot motion. A method is described herein for constructing a path for the wire in which all the required leads are included and the connecting or traversal links are minimized according to an appropriate cost function. Another robot application, which poses the same problem, is cake decoration. In this case, the design consists of some set of required paths. The robot must cover all the required paths and travel between paths in a minimal amount of time. The link connection problem common to both applications is a generalization of the traveling salesman problem and, consequently, a heuristic approach is appropriate. The present method is described in terms of the cable application without loss of generality. The procedure has been implemented and has been successfully tested. The layout of the individual leads of the cable is available from the cable design system. That is, for each lead, there is a starting and stopping coordinate. The problem, then, is to produce a path (sequence of wire segments, or chain) which connects the leads of a common wire type, which minimize the traversal between leads according to some cost function dependent on the end points of the link. The layout of the common leads is referred to in terms of a graph. Links are added to the graph which represent the traversal of wire connecting the leads or required links. These extra links are sometimes termed the "wasted wire" since they are not required in the final cable. Two cost functions have been adopted for the cable application: 1) Euclidean distance between endpoints 2) Step function: if dist(v,w) is <=M then return(dist(v,v)) else return(BIGVALUE) This modified form of the distance function is used if it is determined that any link over a certain length not be strung continuously by the robot, but, instead, the current wire path should be cut and wiring re-started. Thus, all links over a certain length should carry the same cost. PROCEDURE The construction of the wire path (chain) consists of two steps: 1) Build a minimal spanning tree on the partially linked graph. 2) Perturb the tree into a chain. This two-step procedure leads to better results than the alternative "greedy" procedure of building the chain by iteratively joining shortest cost lin...