Processing the advantages of zone architecture in automotive

Think of a passenger car as a collection of electronic control units (ECUs) that are distributed across the length and breadth of the car and that talk to each other using different networks. When adding more advanced automotive electronics for vehicle-to-everything (V2X), automated driving and vehicle electrification, the number of ECUs increases and the amount of data exchanged grows. 

The domain architecture explained simply

In a domain architecture, ECUs are categorized into domains based on their function, but the zone architecture is a new approach that classifies ECUs by their physical location inside the vehicle, leveraging a central gateway to manage communication. This physical proximity reduces cabling between ECUs to save space and reduce vehicle weight, while also improving processor speeds.

To understand the domain architecture, it helps to start by understanding the five domains in which ECUs are typically categorized based on function, as shown in Table 1. 

Table 1: ECUs are typically classified into five domains 

The ECUs communicate and exchange data over networks that are specific and relevant inside their own domain while also communicating with ECUs in outside domains. Since the network in one domain could differ from the network in another domain, a gateway serves as a bridge. 

Figure 1 illustrates a vehicle with a domain-based vehicle architecture. In this figure, there is a central gateway module connected to the different domains in the car. Each domain performs several functions. The domain controller, for example the vehicle control unit for powertrain includes gateway function. This domain gateway helps communicate data across the ECUs supporting the relevant domain and from the domain to rest of the vehicle.

The domain controller also incorporates ECUs, which helps minimize system cost by integrating the functionality typically implemented through multiple ECUs. TI’s Jacinto 7 processors integrate Arm® Cortex® A-72 cores for raw processing power to handle the data, an Arm Cortex R-5Fs for real-time control and gigabit time-sensitive network (TSN) and Ethernet switch for high-speed networking.

Figure 1: Domain architecture

Introducing the zone architecture

If the car was a room and the ECUs were people gathered in that room to discuss different topics, a domain architecture is equivalent to chaotically arranging those people, causing them to shout to others in their discussion groups across the room. 

Figure 2 shows a vehicle in zone architecture organizes the ECUs based on their location inside the car and adds a vehicle compute module. The vehicle compute module is a computer with a large processing capacity to perform all computations regardless of function. The figure also depicts the zonal modules and associated edge nodes in different regions of the car. 

It is possible to use a low-bandwidth network such as controller area network (CAN) for communication between the different zonal modules and the central gateway/compute modules. However, high-speed networks such as Ethernet is also a good choice because it provides high reliability and smooth operation in a range of automotive temperatures. And for distributed compute across the central compute and zonal modules, PCIe is a well-suited network choice.

Figure 2: Power distribution modules in zone architecture

Power distribution advantages of a zone architecture

Engineers are also taking advantage of this reorganization of ECUs to optimize power distribution architectures – specifically the redesign of smart junction boxes, which distribute power to different loads and ECUs in the vehicle. Specifically, engineers are replacing relays and fuses with semiconductor solutions.

In a zone architecture, the power distribution boxes are distributed so that each zone has its own power distribution unit to power the modules in the corresponding zone. Figure 2 shows the concept of power distribution in a zone architecture, where you can see the integration of each zone’s power distribution function with the zonal module that manages the network traffic as well. The new power distribution architecture will lead to a harness cable weight reduction, which results in higher fuel efficiency for internal combustion engine-based vehicles and higher driving ranges for battery-powered electric vehicles.

The transition from domain to zone architectures – crossover architectures to the rescue

To transition the complete vehicle architectures from the current domain architecture to the new zone architectures is a huge undertaking. Not only do new zonal modules have to be designed but also the software in most all has to be redeveloped and reconfigured to support the new architecture. Further, replacement of melting fuses and redesign of the complete vehicle harness has to be thoroughly verified and validated.  All this to say that vehicle architectures will be migrated what is likely to be crossover architectures.

Figure 3 shows crossover architectures that are a cross of the existing domain architecture and the new zone architectures. These architectures will retain domains and the corresponding edge nodes. The central compute in zone architectures will likely be subdivided into ADAS, IVI, and VCU compute modules, with domain-specific edge nodes directly communicating with the corresponding central compute module. Zonal modules in the crossover will most likely focus on power distribution and will be much less a gateway for all edge nodes in the zone. That is, a zonal module will look much more like a traditional body control module (BCM), except that there will be multiple of these in the car.

Figure 3: Crossover architecture 

Conclusion

With increase in the number of ECUs, the vehicle architecture has evolved into a domain architecture where the ECUs are grouped based on a related function that each ECU is performing. This has increased both network and power distribution complexity, however. Automotive vehicle designers are now designing zone architecture-based vehicles, with first generation vehicles being crossover architectures, to optimize both data and power distribution. The new zone architecture will ultimately lead to a harness cable weight reduction, which results in higher fuel efficiency for internal combustion engine-based vehicles and higher driving ranges for battery-powered electric vehicles.

For more information, please read the whitepaper: How a Zone Architecture Paves the Way to a Fully Software-Defined Vehicle.