Agenda 2024, Day 2 - Wednesday

Zonal Architectures are an upcoming trend in automotive industry and gain importance. Nevertheless, this disruptive megatrend does not only impact the wire harness itself, but its implications propagate through the complete supply chain also affecting the connectors.

Three different topics, linked to the opportunity of zonal architectures, are depicted:

First, the zonal approach also demands versatility of connectors to enable the highest degree of freedom to design optimum solutions. Modularity of connectors is one possible solution to this demand. Second, by refining the harness development process, as done in a recent research project, also digital twins of connectors, implemented during the design process, prevent overengineering and in parallel offer the unique opportunity to improve diagnostic functions in modern cars in combination with e-fuses. Third, the signal integrity of data links is of major importance for highly autonomous vehicles with low failure rates.

Therefore, it is advantageous to implement virtual design evaluation on wire harness level, incorporating sophisticated models of connectors and cables. Thereby it is possible to quantify the performance of data links during early development stages and the impact on reliability and the choice of the components.

Simultaneous engineering of the wire harness along the supply chain can yield significant functional and system cost benefits in comparison to the typical TIER approach. We analyzed in a holistic approach requirements of component, connector and wire harness and developed a new concept for a high-voltage wire harness.

Today connector manufactures supply a construction kit consisting of multiple plastic parts, seals and terminals to the wire harness makers. Typically, terminals consist of a spring element which is joined to a retainer by means of welding or riveting. This retainer is joined to the wires by mechanical crimping or ultrasonic welding where the interface and appropriate tools are defined by the connector manufacturer.

We broke up this pattern and worked out a connection system without a terminal retainer: A contact spring is directly welded on a compacted wire. The compacting of the wire is done by a combination of a welding process with a subsequent mechanical calibration in order to achieve the required thickness tolerance. Welding of the spring is done a continuous-wave laser in the visible range. Naturally, design was optimized to automate the assembly process as much as possible.

Significant improvements in packaging and system cost could be achieved. Moreover, derating performance is superior to classical designs because of less contacting parts and better heat removal.

The electric HV protection system of electric vehicles increasingly tends to consist of a combination of contactors and pyro-fuses. The pyro-fuses must switch off all possible short circuits safely. When the vehicle is charging, a short circuit in the connected charging station must also be switched off by the vehicle’s on-board electric protection system. The additional inductance of the charging wire results in an increased inductive energy that has to be dissipated within the pyro-fuse. It was, however, for a long time overlooked, how high this additional inductance can become. In large charging parks, very long wires are possible, and they bring significant additional inductances into the electric system, which are relevant during a short-circuit event.

This is a major challenge for pyro-fuses: the energy can be up to ten times higher than what has been accounted for. The maximum energies to be switched are a crucial limiting factor for pyro-fuses, determining their sizes and costs. But not only the inductive energy itself must be considered, but also a resistive fraction, which becomes very significant at high inductances.

In order to keep the switching energy within reasonable boundaries even at high inductances, short circuits must be switched off while the current is still increasing. This is inevitable anyway considering the circuit’s melt integral. Short-circuit detection and pyrotechnic trigger times are crucial to ensure a safe all-round protection. Depending on the protection system’s response time, the energy reaches a maximum at a medium high inductance. Simulation helps to determine this worst-case inductance. High inductances become disproportionally more challenging for 800 V systems when compared to 400 V systems. The pyro-fuse’s overcurrent becomes a major limiting factor as well, which is often overlooked.

The automotive industry's strategic shift from hardware-centric to software-oriented solutions, often referred to as the “Software Defined Vehicle”, is initiating a paradigm shift in product development. The transition towards digitalizing automobiles calls for the adoption of new development processes and architectural frameworks, notably the In-Vehicle Network (IVN). It is essential to note that these advancements necessitate the processing and transmission of substantial volumes of data. The underlying backbone enabling these innovations remains the hardware infrastructure.

This presentation explores the cutting-edge developments in data cable technologies, crafted to address the emerging requirements and standards essential for the realization of IVN architectures, as stipulated by working groups or standardization committees like ASA, IEEE, OA, and SAE. We delve into the variances in requirements of key working groups, encompassing channel specifications, components, and high-frequency cable properties, shedding light on the diversity of cable requirements. We will discuss cables capable of meeting a diverse array of specifications. The key to surmounting this challenge lies on digitalization, innovative material solutions and cable design improvements.

In the low-voltage distribution of vehicles, selectivity describes the ability to switch off a fault using a protective device (e.g. an eFuse) that is assigned to the individual current path. A disconnection at a higher level in the distribution hierarchy in response to a fault at a lower level is not selective, as a complete supply network branch with several, probably critical loads is disconnected. Selectivity is also violated if several eFuses at the same level react to a fault event in a parallel load path.

To maintain selectivity, the criteria for detecting a fault must be carefully selected. The speed of the eFuse and tripping to a certain current threshold are considered beneficial for avoiding faults. However, there may be a trade-off in terms of selectivity if the system design and threshold criteria are not appropriately matched. Particular care should be taken when introducing low-voltage Li-based batteries, as this type of source places new demands on the system design and the definition of thresholds.

Scalability describes the freedom to add new loads to the vehicle supply network to support different vehicle configurations. Spare channels on the other hand are desirable, but the cost of unused content is hardly bearable. The configurability of channels for different loads must also be checked for selectivity conflicts.

Overall selectivity in eFusing is a new requirement for the design of the E/E board-net architecture. Awareness and a similar mindset among E/E architects, semiconductor manufacturers, OEMs and first tier is not always given. However, this is essential for a robust and safe energy supply in the vehicle.