Automotive wiring systems are undergoing a major transformation as engineers search for ways to address the new era of autonomous driving, connectivity, electrification and sustainability.

These challenges are subjecting wiring systems to higher safety requirements, multiple voltage levels and greater power requirements, as well as the need for additional sensors, actuators, data traffic and processor capacity.

In some cases, current customer-specific wiring systems have more than 100 control units and more than 1,000 individual lines, and the trend is growing.

"This means we are slowly reaching the limits of what can be reasonably handled in manufacturing and final assembly,” warns Ingo Spengler, chief operating officer at Leoni AG. "Let’s face it: we cannot continue as before. We have to rethink the wiring system."

Zonal architectures are intriguing to automakers and suppliers, because they promise to help reduce costs, save weight, streamline supply chains and improve production processes.

Leoni envisions future electrical and electronic architectures that have a small number of central computers connected by high-performance “data highways.” Surrounding the high-performance computers, the wiring system will be divided into several zone.

In these zones, a zone controller will independently perform sub-tasks such as power distribution or data management to and from the sensors and actuators. The first zonal architectures of this type (zonal approach 1.0) will go into production within the next few years.

Engineers at Leoni and a major automaker have jointly designed a wiring system to allow the automated manufacture of subharnesses. They believe that the number of zones and zone computers could gradually increase toward the end of this decade. This would be associated with further standardization of power distribution and interfaces, as well as even more consistent software-supported functionality (zonal approach 2.0).

A well-structured zonal architecture offers several benefits. For instance, the smaller the cable harnesses in the individual architectural zones, the more likely it is that they can be manufactured in a partially or fully automated process, including the integration of connectors, controllers and mounting bracket.

According to Spengler, partially or fully automated production of subharnesses would enable suppliers to change from a customer-specific to a product-specific production strategy. Up to now, he says Leoni has generally produced a customer-specific wiring harness in a specific plant. In the future, the company plans to manufacture subharnesses of a similar structure, such as for bumpers, for different customers’ vehicles together in one plan.

“This will make it easier to compensate for fluctuations in capacity utilization, while the significantly higher level of automation in the future will considerably improve the manufacturing quality and traceability of all production processes,” claims Spengler.

“Another effect of greater automation is to decrease the relative importance of labor costs,” says Spengler. “This makes it possible to once again move wiring harness production sites closer to OEM vehicle assembly plants, which reduces distances and thus transport costs, and also lowers the carbon footprint of logistics and the wiring system. Moving wiring system production closer to OEMs can also minimize geopolitical risk factors and strengthen the resilience of supply chains.

In addition, zonal architectures provide greater freedom in OEM vehicle assembly. For example, a subharness can be installed separately in a vehicle module off the main line or externally at a Tier 1 supplier. This module is then ”married” to the rest of the vehicle.

“OEMs are already considering the possibility of manufacturing entire large vehicle modules—such as the front end, back end or skateboard—separately (including the subharness) and then joining them together in a final assembly line to form a complete automobile,” explains Spengler.

“In this process, the subharness can be easily and securely connected to the main harness with defined and robust interfaces,” Spengler points out. “Wiring system functionality testing and software flashing could also be performed in the module at an earlier stage, rather than at the end of the line."

Another potential benefit of zonal architectures would be a reduction in total cost of ownership. Automation allows processes, components and interfaces to be extensively standardized. For example, Leoni is already working on an operating system that will collect, standardize and consolidate best practices to create a standardized approach at all of its production facilities.

Together with uniform cables, connectors, processors and hardware-software interfaces, this will permit time and cost optimization both in wiring harness production and in final vehicle assembly. For example, it will allow a more effective balance in the conflict of objectives between unit costs and assembly cost.

“Working closely with the OEM, [we] can develop an intelligently designed wiring harness that compensates for any higher unit costs in production through automated, and thus lower-priced, assembly at the customer's plant,” says Spengler. An additional advantage offered by the zonal approach is modularity.

“Even in the development phase, the unavoidable short-term changes can be integrated more easily and thus more quickly into the overall architecture,” notes Walter Glück, chief technology officer at Leoni's WSD Wiring Systems Division. “The same applies to model maintenance measures and ongoing development of the wiring system architecture in the event of a model change."

A third major benefit of zonal architectures is lightweighting and sustainability.

Automotive wiring harnesses are large, bulk, and heavy. Initial analysis from current projects show that the total weight of a zonal architecture could be lowered by about 10 percent. With zonal approach 2.0, Glück believes that mass could eventually decrease by up to 30 percent vs. today's customized cable harnesses.

“Weight can also be reduced, thanks to the much more manageable packaging of subharnesses, as compared to a bulky, heavy customer-specific harness,” says Glück. “Together with a geographically optimized supply chain, zonal architectures offer the potential of comprehensively reducing the CO2 footprint of wiring harnesses, which in turn effectively supports the sustainability efforts of OEMs.”