Denso develops compact electrical ADAS architecture

R&D manager, Kazuyoshi Obayashi, explains how the redundant power net system can increase safety levels in increasingly autonomous vehicles

If fully autonomous driving is a destination, then we are yet to reach it. But in the mean time systems where the vehicle can take control during certain scenarios but requires the safety net of a human driver to be on hand are part of the journey, but these systems pose challenges too. Tier One Denso has developed a solution in situations where the vehicle needs to return control of the vehicle to the driver but could be disrupted by a power failure. The firm's system works to the theory that while electrified vehicles should have redundant power on hand because of dual onboard power networks, combustion engine vehicles are less likely to. Denso’s manager of power conversion R&D, Kazuyoshi Obayashi explains his firm's latest technology:

"What kind of society will we have with fully automated driving? Firstly, traffic accidents can be reduced. Also carbon dioxide will be reduced with new routing, reductions in traffic jams and thirdly you can use driving time effectively for preparing work, reading books or watching TV. 

"Fully automated driving can also enable mobility for people such as the elderly, children and disabled who would otherwise struggle. But to reach this stage we have several steps to take. OEMs and suppliers are now developing systems at level three of automated driving as defined by the SAE.

"The big difference between level two and three is who the main driver is. For level two, the driver is human and the system assists but, at level three, the system drives and the human is a fall back in case of a failure.

"Operational behaviour at level three, when there is a failure detected the system can issue a takeover request (TOR) to the human to take over driving in 10 seconds – when automated driving terminates and the car is driven manually.

"At this level, the system is driving so much that the human may not be ready to take over because it takes time to recognise the driving situation so a minimum risk manoeuvre (MRM) might be required, such as automatic stop.

"This is an important function to realise level 3 in the real world. To do a TOR and/or MRM, redundant components are required, including; camera, radar or lidar and also actuators and inverters are also required.

"A lot of R&D is focused on these systems and components but power supply has not been discussed enough.  A power net offers four main functions: supply electricity power to each load, power when accelerating, reduce power consumption if required and also minimise the fail for electricity regeneration.

"Power net components such as ISG, alternator, DC/DC converter and others, are controlled to realise these functions, so what kind of requirement will see ADAS realised?
In a hybrid vehicle, PHEV or EV it will normally have two batteries; a lithium-ion battery and an auxiliary 12V battery. Power management controls, traction, regenerating braking energy to improve fuel economy and each load and the sensors are fed from the battery and DC/DC converter.

"With two power supplies, redundant power can be possible with just the challenge of wiring, failure detection and power management. 48V with 12V battery system has a similar configuration. For conventional vehicles, they only have one battery therefore imagine what would happen if the battery fails during an idling stop period as the engine and alternator have already been stopped, there is no way to supply electricity.

"In the first generation of ADAS, electrified vehicles were the target for redundant power systems but now the conventional vehicle should also be a target, therefore we started to investigate a simple power net for them.

tags: ADAS Denso Electronics