The powertrain system takes the inputs from your foot on the accelerator and sends that as a request to the powertrain, whether a combustion engine or a single or pair of electric motors.
Meanwhile, a separate driving dynamics unit receives inputs from the steering wheel and brakes, along with any other data the car’s sensors might get from the external environment.
Those two systems run in parallel, so there’s a small but potentially significant lag when they need to send data to each other, and there are limitations on how closely they can operate together.
The Heart of Joy unites those systems into a single unit that receives all those inputs in the same place, processes them simultaneously and then sends the information to up to four motors along with the brakes, steering and so on. BMW says it allows for communication that’s up to 10 times faster than that used on cars that were on sale in 2021.
That’s a big boost when trying to precisely modulate power and braking to best fit the conditions. But there are other benefits too. On most current EVs, friction braking is controlled by the driving dynamics unit while regeneration through the motors is the responsibility of the powertrain system.
That’s why you can sometimes feel an imbalance if you’re slowing using the regen and then need to apply the brakes.
“When recuperation is only done by the powertrain, you can’t use the whole potential of it,” says Thalmeier. “You need the driving dynamics system to work out how to enlarge the recuperation.”
He cites the example of a rearbiased car – yes, future BMW EVs will still be rear-driven or rear-biased – cornering at speed. “
When there’s a load change, you can only put a certain amount of longitudinal force on the tyres before the car becomes unstable,” he says.
“So to keep the car balanced, you have to take away either lateral or longitudinal force. Because you’re cornering and you can’t remove the lateral force, you have to reduce the recuperation to keep the car stable. But that’s not what we want: we want to add stability by recuperation.