When you’re testing the build of a car, you have to check its many subsystems: the battery, the engine, the cabin, the thermal-management system, the gearbox, the chassis, and the suspension.

“Which part is the toughest to simulate?” a Tech Briefs reader asked an industry expert from the technology giant Siemens.

The answer may surprise you.

"Making a simpler drive leads to greater complexity," said Siemens’s Steven Dom, Director Automotive Industry Solutions at Siemens Digital Industries Software, in a live presentation on TechBriefs.com this month called Simulation and Testing: The Driving Forces for Engineering the Vehicle of the Future.

Read Dom's edited response below.

"What do you think is the most complex subsystem to develop, and what is the easiest?"

Steven Dom: The most complex subsystem? There are different factors to what constitutes a complex subsystem. The electric drive unit , or e-drive unit, that I talked about is a very complex system because you have electronics, electromagnetics, transmission, and you need to have your fluid flow in there for the lubrication. That is definitely a very complex system to develop.

Steven Dom, Director Automotive Industry Solutions at Siemens Digital Industries Software

But is it the most difficult one to develop? I don’t think so. Every single element in there is quite well managed now.

I think the most complex subsystem to develop, in terms of difficulty to reach a satisfactory level, is probably the autonomous function. Each of the different elements are not specifically complex. The modeling of a sensor is not so complex. Well, it’s complex, but it’s not [the same difficulty level as] pushing our minds to new levels of complexity, or defining driving scenarios.

Control software has been around for a long time, but actually bringing all that together and actually meeting the expectations of the public in order to accept an autonomous driving vehicle? I think that is at the moment a very difficult one.

So, it’s not so much the individual complexity. A battery is a very complex system, for example, because of the chemistry that’s in there, but we know how to model a battery. When something goes wrong in the battery: that’s much more difficult to model. That, you could say, is more complex all of a sudden, but in the end, the battery is a simple system.

When we say the "easiest" or the "simplest" system, I often use the phrase: "Simplification drives complexity." When there's a drive to make the vehicle simpler to produce, the engineering challenge becomes more complex. But it doesn’t mean that the system becomes more complex.

What do you think? Share your questions and comments below.