Home » Wire Processing: CAD Keeps Pace With Complexity
A new generation of CAD software is helping engineers design increasingly complex electrical systems for today's vehicles.
Generative design is fast becoming the cornerstone of electrical system design in vehicles. What’s different about the generative approach? Wiring designs are automatically generated from higher level inputs, rather than interactively constructed by an engineer working with a lesser tool.
The typical electrical design process consists of three steps: system design, system integration and harness engineering.
System integration is a difficult and error-prone task, especially with rising signal count and configuration complexity. Imagine a semi tractor. These trucks are available with a huge variety of options and many mechanical configurations, such as different wheelbases. Complicated configuration logic applies: It’s impossible to have both right- and left-hand drive simultaneously, but it is possible to have left-hand drive, a long wheelbase and a satellite theft-tracking system simultaneously. Millions of individual electrical configurations are possible. Engineers must keep track of all possible configurations, while ensuring that in-line connectors mate correctly and pass signals from one harness to another.
In the generative design process, system integration and development of wiring proceed automatically, based on simplified input expressions. The “ingredients” include: * System pin-to-pin signal connectivity. Each signal is tagged with an expression defining the options it supports. This is a comparatively straightforward design task. * Mechanical constraints, such as routing channels, bundle lengths and in-line connector locations. These are typically developed within 3D mechanical CAD systems. Mechanical constraints may also reflect configuration variables, such as alternative wheelbases. * Configuration logic, which expresses the relationships between the configuration variables. These consider such things as the impossibility of building a vehicle with both right- and left-hand drive. * Design rules, which enforce the design methodology of the engineer and the enterprise as a whole.
These four independent inputs are all that is required to calculate automatically the wiring for the entire vehicle for the superset that includes every configuration the logic allows. This calculation accomplishes system integration entirely within the ECAD tool.
The design rules are the key to the generative process. They capture the designer’s skills, and more broadly the intellectual property of the designing organization. The rules instruct the ECAD tool’s algorithms how to proceed. The sum of all the rules is a substantial body of required and forbidden states that must be adhered to. Rule sets may be hierarchical and dynamic. They may even act on data retrieved from outside the CAD data environment.
Rule sets are normally company- or project-specific. Examples include: * “Never permit more than six wires in any splice” * “Never permit wires of the same color to occupy adjacent connector cavities.”
The generative approach creates designs that are correct by construction. If the four “simple” input expressions are written correctly, the software will automatically generate accurate wiring designs for all allowable configurations.
There is much more to generative design than just rule checking, though the rule sets do robustly implement best practices, allowing organizations to capture and develop their competitive intellectual property. System integration is rapid, accomplishing in a few hours a task that would otherwise take weeks. This not only reduces electrical design times and costs, but also allows the evaluation of alternative designs, sometimes by applying different rule sets.
Design change management is greatly simplified, too. Because the four inputs are independent, a design change affecting just one of the inputs (for example, a change of configuration logic) can be propagated through the process easily.