The energy supply in autonomous electric vehicles is guaranteed by two sources: In addition to the high-voltage battery, there is a 12V battery that supplies the car in idle mode or in high load situations when the vehicle is in motion. Safety-critical components such as brakes and steering can thus be connected to two energy paths. But what happens if a fault occurs in one of them?
In today's on-board network architectures of highly and fully automated vehicles, it is common practice to isolate the affected area by means of an overload fuse - in the past usually a single-use fuse, today increasingly implemented as an electronic switching element. This design, however, results in the affected component being switched off completely in the event of a fault. For highly and fully automated driving, such a procedure is only possible if all components and the vehicle electrical system are redundant, i.e. duplicated - an expensive approach, especially in the case of the vehicle electrical system, which also requires additional space and increases the vehicle weight. In order to ensure highly reliable safety while driving even without a second on-board power supply system, researchers at Fraunhofer IZM in the HiBord project, together with partners from industry and the Fraunhofer Institute for Integrated Systems IISB, developed a disconnecting element that switches off the faulty on-board power supply system component and still guarantees the supply of safety-relevant components.
The researchers see this as a significant improvement in safety during autonomous driving. Phillip Arnold, research associate at Fraunhofer IZM, explains: "With current systems, undervoltage during driving can lead to an abrupt and uncontrolled failure of the entire electronics, including the steering and braking systems. Especially at high speeds, this is an intolerable risk. Thanks to our new module, part of the on-board network continues to function and the fully automated car has sufficient time to drive the passengers to a safe area, e.g. to a hard shoulder or parking lot".