Next-Link is initially applied to the domain of cable harness
design. The general problem is that electical cables must be organized
into harnesses and routed to fit inside of tight and complex
environments. The designing engineer must repect the eletrical
connections and properties specified, layout a topology of cable
harnesses, and then route them with a 3-D geometry, as
illustrated.
That this is even more complex than it appears can be seen by looking
at the detail
of a connection. It can be seen that a variety of parts, differing in
use, constitute each connection. The result is a domain that is
sufficiently complex as to be challenging, but not impossible.
In the following scenario, we will configure and route two cables,
C1 and C2, through some particular
environment, which includes a structure and zones where heat or
electromagnetic radiation may require cable bundles to be shielded,
and "off-limits" zones reserved for future use, where cables are not
allowed to pass. The environment also imposes restrictions on
surfaces where the cables may be clamped and where there is room to
access them for maintenance.
P2V1
We begin by supposing that Engineer Jane is configuring and
routing C2. The initial default
configuration requires that the major cable bundle go through the
high temperature zone, requiring heavy and expensive heat
shielding. Let us designate this design as the Path of C2, Version 1,
or, for short, P2V1.
P2V2
Design P2V1 is rejected and an attempt is made
to completely avoid the high temperature zone with
design
P2V2. But this seems to require too
much cable. The designer rejects this design in
favor of a compromise that has a little heat shielding.
P2V3
Unfortunately, this more optimal design,
P2V3, violates
constraints on clamping. Jane is forced to revert
to P2V2 as the best choice.
P1V1-5
Meanwhile, Engineer Joe is working on C1.
His initial working design,
P1V5,
results from
rejecting four previous designs because
of constraint violations. Later, it will be important
to note that one of these, P1V3, was rejected
only because of the off-limits rejection.
P2V4
At the point where Engineer Joe and Engineer Jane
have committed their designs and published them to be "seen" by each
other, a global constraint checker can inspect them. In this case, it
is found that the
two cables must pass over each other at one spot and
that one or the other will be inaccessible for repair.
After negotiation, the engineers decide to reject
design P2V2, which leads to design
P2V4.
P1V6
There is still a minor problem. The new design for cable C2,
P2V4, still interferes with P1V5 because they both need to clamp in the
same place. Fortunately, C1 can be clamped
slightly differently, with no change in configuration,
to become a consistent design,
P1V6.
Design Rationale
At this point, any subsequent engineer should be able to ask NEXT-LINK
the reason for the current design decisions. For example, the routing
of P2V4 depends upon the problem with access space and the
routing of P1V5. Certainly a engineer must be
able to determine why the clamping for the latter had to
be changed to P1V6.
P1V3
However, a design rationale should also be active. Now suppose that it
is later determined that the off-limits space, which was being
reserved for other cables, is now free.
Can you say quickly which cable and engineer are affected and
how? If not, an opportunity to improve the design will be lost.
This is a typical coordination problem.
NEXT-LINK should notify
Engineer Joe that P1V3 was prevously rejected because
of a conflict with that off-limits zone, but there is no longer any
known objection to this previously prefered design. The engineer
decides the optimization is worth the change and instructs NEXT-LINK
to make it
so.
P2V2
Another opportunity is now presented.
NEXT-LINK's next job is to notify Engineer Jane
of Engineer Joe's decision. Why? Because
the rationale for the current design for his cable,
P2V4 depends upon the rejection of P2V2,
which in turn depended upon a conflict with designs
P1V5,6. But Engineer Joe has changed
back to P1V3. Now Engineer Jane
is free to optimize the routing of cable C2
and also tells NEXT-LINK to make it
so, resulting in a new and better
final design.
Distributed Cable Design
This scenario addresses the complexity of design and the need for a
design management tool for only two engineers and two cables. In
reality, a cable harness consists of many complex cables designed by
several engineers, with different expertise. For instance, one
engineer might work on clamping and another routing of the same or
different cables. Obviously, this introduces a new level of complexity
to the task of coordination management.
To understand more about how the design task can be managed by
NEXT-LINK among different design agents, please see
the NEXT-LINK deliverable description.
MAC users may retrieve
compacted self-extracting binhexed copies of a PowerPoint 3.0
presentation of this scenario. (224K)
______________________________________________________
Charles Petrie
