Vehicle dynamics & chassis: The feelgood factor
EPS systems offer increased functionality but haven’t always delivered on feedback. AE asked experts to explain how to develop steering feel
- Published in Focus.
Turning a corner: It took Ford six years to perfect the technology
Norbert Kessing
Steering feel provides good road feedback, so that the driver feels what the vehicle is going to do before the actual motion starts. This helps to reduce the effort of the task.
We want to achieve a linear vehicle response: if you double the steering wheel angle, you get double the response from the vehicle, making it easy to find the right steering wheel angle in any kind of curve. So the driver doesn’t under- or overestimate, and therefore doesn’t have to make corrections.
The last element to steering feel is a good match between torque and response so that it’s easy and intuitive for the driver to adjust to the right steering wheel angle.
Vehicle dynamics are important attributes but the steering feel within vehicle dynamics is really the main one.
Our goal is fun to drive, combined with a relaxed and refined driving experience.
Without good steering, you can forget the rest. We tried to make use of EPAS in the Focus six years ago. For one-and-a-half years we tried to make this happen, but found back then that the technology was not mature enough, so we dropped it and went back to a hydraulic system.
Motor power and especially the dynamics of the motor were just not sufficient. Dynamic response of EPAS motors has to be very good, otherwise you won’t be able to provide a natural steering feel, even with the best possible controller – that’s the number one prerequisite.
And controllers have improved a lot. Not just software but also the power of the chips – it’s a doubling or tripling of computing power, which helps a lot. The key term here is the sampling rate: how quickly and how often per second the chip computes new values – the sampling rate versus six years ago is around three to four times better.
