Automotive architectures reflect differing design philosophies -

Automotive architectures reflect differing design philosophies

The adoption of sensors has led to differing philosophies on how to design modern vehicles, from the domain architecture to newer zonal and central architectures.

Thierry Kouthon

Electronics first appeared in cars in 1968 when Volkswagen installed an electronic control unit (ECU) in the VW 1600 sedan’s engine to help control fuel injection. Today, automotive electronics are ubiquitous, controlling or assisting with every aspect of the vehicle’s operation and performance. Electronics now account for over 40 percent of a new vehicle’s total cost, having grown from just 18 percent in 2000, according to Deloitte.

Integration of computing technology into every aspect of the car has transformed how automotive OEMs approach design, engineering and manufacturing. Up until the past decade, vehicle electronics used a flat architecture where embedded ECUs operated together in a limited way. The advancement toward connected cars and AVs led to a divergence in how carmakers approached the communication architecture of a vehicle’s electronics.

Concurrently, the introduction of sensors into the vehicle architecture further accelerated the need for greater computing power to process and analyze the resulting data. These new aspects of the vehicle’s brain led to differing design philosophies toward designing modern vehicles, from the domain architecture to newer zonal and central architectures.

Domain architectures

Traditional automakers such as Daimler and BMW have generally preferred the domain processing architecture due to their long history of integrating ECUs for specific functions like engine and transmission control, climate control, anti-lock braking and parking assist. This was more an advancement and optimization of the older flat ECU architecture rather than a design evolution or transformation.

The domain architecture focused on aggregating ECUs that were functionally related under a common domain controller or gateway. This introduced a subdivision of ECUs under powertrain, chassis, infotainment and passenger comfort domains. This domain architecture didn’t optimize for wiring because the ECUs for each functional domain were scattered throughout the vehicle.

Zonal architectures

Automakers, however, are now evolving towards new architectures to address increasingly complex advanced driver assistance systems (ADAS) and autonomous driving requirements. As evidence of these shifts, Daimler announced in 2020 that it was co-developing with Nvidia a new software-defined computing architecture. Similarly, Qualcomm announced in late 2021 that it was working with BMW on its next generation of AV systems.

As noted earlier, one of the popular architectures for these traditional automotive OEMs is the new zonal architecture. This approach addresses domain architecture shortcomings by combining ECUs that are physically close under a single zonal controller. The advantage is a reduction in wiring — and weight — at the cost of increased software complexity. This is because the zonal controller must be able to differentiate traffic between the ECUs that connect to it according to function.

The evolution of the domain-centric approach to a zonal architecture creates a network system across the vehicle; the cabling reaches from the central servers outward to the gateways and sensors. Automakers can easily scale zonal architecture up and down to support more sensors and electronics throughout the vehicle. It also allows for increased flexibility for variants of a vehicle model template.

Central automotive architectures

At the other end of the spectrum, companies such as Tesla and Waymo tend to prefer a central processing architecture, in which manufacturers place a majority of the computing power in one centralized processor. This is in part because these car manufacturers don’t have access to legacy designs or technical debt to work with. In other cases, it’s because they have distinct primary objectives.

For some car manufacturers, achieving ADAS Level-5 autonomy as fast as possible is of utmost importance. In the case of Waymo, it’s worth noting that they don’t implement all the driving functions of the vehicle, such as engine control or braking. Rather, they focus on managing the sensors used for autonomous driving. Waymo integrates its technology with existing vehicles such as the Jaguar I–Pace.

SAE J3016 levels of driving automation, in which Level 5 is categorized as completely autonomous driving in all conditions without driver intervention. (Source: SAE)

One major advantage of the centralized approach, which manufacturers take advantage of in their pursuit of Level-5 autonomy, is the ease with which they can distribute software updates. This allows for more rapid experimentation and introduction of new features. Manufacturers considering themselves technology companies first and car companies second find that the ability to frequently add new features after a consumer receives a vehicle is more akin to what customers have come to expect from consumer electronics.

Additionally, the centralized approach allows for better vehicle security because there aren’t as many complex zonal gateways to protect. Manufacturers can distribute over–the–air updates more easily to patch any security risks.

On the flip side, having a centralized unit handle the bulk of the processing introduces a few additional challenges, one of which is a single point of failure. Given that the companies opting for a centralized architecture are also utilizing additional sensors for vehicle autonomy, there’s also an immense amount of data that the vehicle must move and process rapidly without error. This adds prohibitive processing performance requirements to the vehicle’s software.

Any issues with the CPU are often catastrophic and require manufacturers to implement redundancies to limit the chance of problems impacting the central unit.

Final thoughts

While all three architectures evolved from the specific experiences and needs of various automotive manufacturers, many analysts monitoring this market perceive the centralized architecture as the most advanced evolution of automotive architectures. These observers believe a centralized architectures will likely dominate when the industry eventually transitions to full AVs.

Though that timing remains uncertain, we’re likely to see continued rapid innovation in automotive architectures in the near term.

–Thierry Kouthon is a technical product manager at Rambus.

>> This article was originally published on our sister site, EE Times.

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