Collin Arocho
8 December 2020

Eindhoven University of Technology has announced new optimizations to Bosch’s automatic transmission system for electric vehicles (EVs). The system upgrades, part of the doctoral research project of PhD candidate Caiyang Wei, were developed in collaboration with the automotive supplier. Collected data on the current system and simulations were used to show how tweaking the specially designed EV transmission could improve the balance of a car’s efficiency and power, with the added benefit of potentially lowering the total cost for manufacturers and end-users alike.

Test car with CVT4EV. Credit: Bosch

Currently, the EV market is dominated by single-speed transmissions, which use a fixed transmission to transfer power from the electric motor to the wheels. The new system utilizes a continuously variable transmission (CVT), like those found in conventional cars, allowing a vehicle to automatically adjust the RPM (revolutions per minute) and torque of the car’s motor according to its speed. However, different to traditional CVTs, researchers used an optimization method that not only accounts for control of the car’s speed, energy consumption and heat generation but also considers the physical design of the car’s electric motor and transmission system. Combining this method with machine learning algorithms and analysis of measurement data, the researchers were able to design a system that’s optimal in both performance and efficiency while reducing the cost.

Bosch has now integrated Wei’s work in a new powertrain called CVT4EV. According to company, the new system controls result in faster accelerations, higher top speeds and more torque at the wheels for towing and off-road performance. “By operating the electric motor at its most efficient operating point, the CVT also ensures lower energy consumption,” says Gert-Jan van Spijk, transmission director at Bosch. “In addition, due to the reduced torque and speed requirements of the electric motor, CVT4EV makes a more compact electric motor possible. Alternatively, a larger driving range can be selected with the same motor.”