Wired for Autonomy

Wiring harnesses are already heavy, complex and costly, so what happens when AV equipment is added? Two experts weigh in.

January 1, 2020

Dan Scott and Ulrike Hoff

As OEMs integrate automated-driving systems and other new-technology content into their vehicles, wiring harnesses have the potential to become ever larger, more complex and expensive and heavier. (Image: Mentor)

Engineers and product planners are already grappling with the complexity of autonomous vehicles (AVs), with the prospect of complexity increasing. Every second, AVs manage advanced-sensor fusion via high-bandwidth networks, while onboard computers run AI algorithms to process gigabits of data. Connecting it all is the wiring harness, which has become increasingly heavy, more expensive and more difficult to package within the vehicle.

Premium-segment cars and full-size trucks can contain 40 different harnesses comprised of 700 connectors and more than 3,000 wires. Stretched in a continuous line, these wires would span 2.5 mi (4 km) and weigh approximately 132 lb. (60 kg). In addition, there can be more than 70 specialty cables that include coax, high-speed data and USB runs.

This does not encompass the added AV sensors and processing content that will further expand harness size, mass, complexity and cost. The implications of escalating electronic content are a significant issue for AVs built on electric-vehicle (EV) platforms. Engineers can undertake several strategies at the architectural- and harness-level to resolve this dilemma.

Architectural optimizations

AVs rely on a dense network of powerful sensors and computers to detect and react to highly dynamic driving scenarios. (Image: Mentor)

Automakers are investigating new electronic/electrical (E/E) architectures that will simplify the harness design to minimize cost and weight. Such designs can reduce the wiring needed to support vehicle functionality and offer an opportunity to reduce mass while making automated production easier, driving down cost. And OEMs have begun consolidating electronic components, such as ECUs and sensor modules, moving from highly distributed to increasingly centralized architectures. The architectural consolidation is driving reduced bills-of-material (BoM), which directly impacts harness complexity.

ECU consolidation has become a popular strategy as automakers integrate more powerful integrated circuits (IC) and microprocessors into their vehicles. The increased computational capabilities of these chips enables a single box to manage tasks that used to require multiple units. As a result, vehicle architectures are converging with powerful domain controller units using sensor fusion and artificial intelligence algorithms to pre-process sensor data before sending it to a centralized processing unit.

However, there is a balance to be struck with consolidation. An architecture that features only one or two control units managing all vehicle functions will require an immense amount of wiring to connect with all the components that are necessarily distributed around the vehicle. OEMs will need to perform dozens of analyses to determine the optimal balance between distribution and centralization for harness functionality.

Automated data transfer reduces errors in the harness design by streamlining the interaction between domains. (Image: Mentor)

OEMs and Tier 1s also are developing technologies that directly reduce harness weight through smaller wires and new materials. Ultra-thin-diameter wiring (0.13 mm2) is a notable example. Unfortunately, the industry still is struggling to develop sufficient terminal substitutions for all currently existing terminals that can crimp to such a small diameter. The available products on the market currently do not support a large-scale migration to ultra-small diameter wiring.

The same applies to aluminum wiring. For small-diameter wiring, pure aluminum is too brittle and thus not a feasible option. Terminal suppliers are developing optimal aluminum alloys for the specifications of their terminals. This has led to a multitude of different alloys on the market that, in most cases, are incompatible with other suppliers’ terminals. To use these wires, a vehicle would have to use one supplier’s connectors across the full vehicle, which is not realistic.

Finding alternatives to specialty cables will further reduce weight/cost and bundle diameters of harnesses. The number of data-intense sensors and displays will only increase in the future, making it crucial to develop solutions to transmit video and other data-rich signals via standardized wiring. Alternatively, finding ways to multiplex signals onto a single shared specialty cable while multiple devices tap in will have the same effect: reducing weight/cost/bundle diameters.

Leveraging digitalization

In concert with architectural and harness optimizations, adopting E/E software solutions to support development flow will be crucial. Software solutions need to enable rapid tradeoff studies to optimize module locations and identify any module that can be combined to save weight/cost/complexity. With the ability to compare and analyze layouts for their impact, engineers will be able to choose the optimal system architecture.

The Capital software suite enables tradeoff studies with cost, weight and bundle-size metrics to optimize a harness design. (Image: Mentor)

Additionally, the most advanced E/E engineering solutions support data continuity throughout harness development, integrate with other engineering software and automate design tasks. An example is Mentor’s Capital software suite that enables the engineering of electrical systems for large platforms such as vehicles. Such capabilities will help OEMs to design harnesses for even the most sophisticated vehicles.

Data continuity ensures that engineers at all stages of E/E architecture and harness development have access to accurate and up-to-date information. This replaces manual data exchange with a robust digital twin of the vehicle architecture and wiring harnesses. As a result, engineers can collaborate more effectively through automated data exchanges that remove errors from manual data exchange and reentry. Likewise, integrations with software from other domains, such as mechanical design tools and product lifecycle management solutions, facilitate collaboration and automated data exchanges across engineering domains.

Automation capabilities help engineers further optimize vehicle architectures and wiring harnesses. Wiring synthesis combines system connectivity information, such as device and signal types, with the physical harness constraints to generate optimized wiring and splices within the context of the vehicle. Today’s wiring synthesis tools support complex wiring types, multiple shielding materials, various network protocols and can even automatically create ground points.

Finally, ongoing architectural optimizations and system-level changes can have wide-ranging effects on the E/E system and wiring harness. In addition, changes can be initiated throughout the engineering and manufacturing processes, driving constant redesign efforts. It is extremely important to develop a structured and disciplined approach to change management early on in the project.

Advanced E/E engineering software can provide an elegant solution. Integrated device databases can be enhanced with change-control mechanisms to determine ownership over design data and the direction in which certain changes should flow.

With these enhancements, this database will immediately provide automated and structured change-management procedures.

New challenges, new solutions

The move to electrification and AV driving places additional burdens on the wiring harness. As OEMs pursue these trends, they must consider the number and sophistication of technology features they integrate into vehicles, as they have a direct effect on wiring harness weight/diameter/cost.

Modern harness design and engineering tools provide a solution to problems wrought by automotive innovation. By leveraging engineering solutions with high levels of automation, advanced metrics and analytical capabilities, engineers can overcome these challenges. Such solutions enable tradeoff studies to optimize harness materials, component placement and routing for minimal harness weight/cost/diameter.

Design automation then can generate optimal wiring based on device and signal location, and the physical constraints of the vehicle. As the development of the E/E architecture and wiring harness progresses, comprehensive change-management facilities and a robust digital twin ensure that the various engineering domains remain in step with all needed information.

Vehicle automation, electrification and connectivity are coming closer to mainstream reality. These technologies will progressively shift the emphasis in automotive engineering from mechanical systems to E/E architecture.

The resulting capabilities provided by an advanced E/E engineering software solution will be critical to delivering a robust, reliable and cost-effective vehicle platform.

Engineer Dan Scott is Integrated Electrical Systems market director at Mentor, A Siemens Business. Ulrike Hoff is an independent automotive wiring consultant.