Part 1 of this series dealt with overall wiring system design as providing the critical foundation for the growth in automotive electronics systems and functionality. In that installment we looked at how to develop a set of system diagrams into a specific vehicle architecture, taking into account the complexity of a modern vehicle (both in terms of components and the option/variant complexity arriving from increased customer choice).
Part 2 looked at simulation and analysis techniques that can be applied to an electrical distribution design flow to make it more efficient and less costly.
Part 3 discussed automotive wiring harness design flow "pain points."
A new generation of COTS harness design tools emerges
As discussed in Part 3, harness suppliers have shifted towards the adoption of third-party software tools in a bid to become leaner and focused on core competences. In terms of tools available, a new generation is beginning to emerge. So what distinguishes this new generation?
Previous generation tools
COTS harness design tools have been available for several years, and typically have been designed around a key sponsor-customer flow. Normally stable, mature products, they perform well within their dedicated flow. However, when attempting to deploy these tools more widely, perhaps as part of a common tools and processes initiative, they lack flexibility. Implementing new requirements often leads to expensive customizations or costly add-on modules that over-complicate the software.
A new generation of harness design applications came out of recognizing that a different approach is required. These applications have been designed from the ground-up both to be flexible and also to solve some of the process issues noted in Part 3. These tools provide powerful standard functionality coupled with the ability to adjust their automated behavior, reports, and graphical outputs.
Common tools and processes solve design flow challenges
Graphical outputs: No industry standard exists for harness drawings, so harness suppliers must support multiple graphical formats as required by their OEM customers. As a result, adopting a single harness design tool is a particular challenge for suppliers serving multiple OEMs.
The new generation of harness design tools provides a solution to this problem via an ability to configure all aspects of the graphical output. This graphical configurability does not only cover relatively simple tasks, such as controlling fonts and line-styles or automatically placing data tables, some applications provide much more sophisticated graphical styling technology. For example, query engines may be used to enable the information displayed on the drawing to be dynamically changed depending on the underlying design data. In another instance, flag notes may be automatically displayed where a connector is required to carry gold plated terminals.
Data outputs: In terms of supporting multiple report outputs, new generation tools typically make use of XML to communicate design content. In more advanced cases both the data for the harness itself and its graphical image are conveyed via XML.
The advantage of using XML is that it has been designed specifically to enable different applications connected via the Internet to talk to each other. XML is a self-documenting format that can be quickly understood and transformed at a low cost into whatever format a target system may require.
Application customization: Finally, the most modern design applications allow the processing behavior of the application to be tuned using rules. These rules may be configured to enforce particular end-customer constraints or the know-how of the supplying organization. For example rules may be written to support a reliability constraint (e.g. to prevent splices containing more than six wires), to support a safety constraint (e.g. all signals in safety-critical systems must be implemented via wires carrying gold plated terminals) or to support a manufacturability constraint (e.g. no taping must be used between bundle breakouts less that 100 mm apart).
This rule capability is often extended via an extensible design rule checking function. This feature allows companies to build their own checks, essentially capturing their "intellectual property" about how harnesses should be builtensuring that identified failure modes are designed out automatically from new designs, thereby increasing overall product quality and reducing exposure to warranty claims.