The new BMW i3s with its 135 kW electric motor offers a torque of 270 Nm from the standstill. But the traction system can do more than just get going: In adverse weather and road conditions, it increases traction and driving stability when starting off, in braking energy recovery mode and when accelerating from tight corners. The innovation is based on a control system that is 50 times faster than earlier versions. The BMW engineers achieved this performance increase mainly with a simple trick: They installed the driving stability systems for calculating the control process directly in the drive unit - normally these algorithms run in a remote ECU. The installation significantly shortens the signal paths and thus the dead times in the control loop.
BMW did not disclose details about the necessary design changes to the control electronics. It is clear, however, that the developers had to master a number of challenges for this measure, because when placed directly on the engine, the electronics have to be immunised against the strong electromagnetic interference fields of the engine; furthermore, the heating of the drive module requires additional cooling measures for the electronics.
The positive effect of the shortened control cycles is not only felt in purely electrically powered cars. The innovative traction control system also optimises the traction, driving stability and driving dynamics of vehicles with combustion engines, says BMW. In future BMW and MINI models with front-, rear-wheel and four-wheel drive, it will therefore provide noticeably more confidence and driving pleasure even in difficult starting and road conditions.