Improved cornering for energy-efficient vehicles

Tuesday, December 4, 2018

By reducing the resistance when a vehicle is turning, you save energy. That is good both for the environment and for the consumer. The energy saving is made possible by controlling each wheel individually, in terms of steering, drive, braking, wheel suspension and wheel angles.

At the Royal Institute of Technology KTH, Associate Professor Jenny Jerrelind and her colleagues in the field of Vehicle Dynamics strive to find solutions that reduce the resistance that occurs when a vehicle is turning.

“We focus on the tires’ function and their potential to contribute to more energy efficient vehicles. When a vehicle is in motion, the tire creates a resistance that must be overcome. This resistance consists partly of the rolling resistance, which is mainly due to losses when tires are deformed, and partly of the cornering resistance that arises when cornering and the tire forces create force components that act opposing the direction of travel of the vehicle. Our research is based on studying different ways to reduce the cornering resistance”, says Jenny Jerrelind.

The Vehicle Dynamics research group at KTH has studied a future vehicle concept in the form of a wheel corner model, with an electric motor integrated with an active wheel suspension. It provides the ability to individually control steering, drive, braking, wheel suspension settings and wheel angles for each wheel.

“For example, by tilting the tires outward or inward relative to the vehicle body, a so-called camber angle is created. The camber angle gives an extra side force in the direction of tilting the tire.”

RCV Asta Zero

KTH’s experimental vehicle RCV, Research Concept Vehicle is built at their own ITRL laboratory, Integrated Transport Research Lab. The vehicle is equipped with wheel corner functionality and has enabled researchers to test the strategies on an actual vehicle. Trials have for instance been carried out at the AstaZero test facility in Sweden.

The major challenge for the researchers is to create reliable and verified tire models:

“Optimizing the tire’s performance for energy efficiency can create conflicting requirements in terms of safety, comfort and performance. You should also try to include tire wear in the models to see how the tires are affected by electric motors and when you have camber angles on the tires.”

Jenny Jerrelind

The simulations and tests performed by the researchers show that energy losses really can be reduced by individually controlling the camber angle, drive and steering for each wheel. Adjusting the tires’ function while driving for the sake of better energy efficiency is beneficial from a number of aspects.

“The ability to individually control steering, drive, braking and wheel suspension settings to reduce energy consumption are both good for the consumers as well as for the environment”, says Jenny Jerrelind.

Now, continued research and more real-life tests will need to be conducted:

“There is a need for research on tires wear and how to implement tire wear in the simulation models. There is also a need for more physical tests with test vehicles to evaluate the different governing strategies.”

/ Daniel Karlsson, photo: Jenny Jerrelind