Which innovations allow the EPS market to grow? The electric power steering market is forecast to grow by 13.44% globally by 2016. The challenges of this development will be among others cost as well as compliance and validation to functional safety standards such as ISO26262. But which innovations make the new breakthroughs possible? Learn about recent developments regarding EPS, by studying the technology report by Peter Els & Colin Pawsey. Their exclusive article goes into depth on following issues: • Current developments in EPS architecture • Latest in the use of permanent magnets • EPS using 3 phase motors • What does the future hold for EPS technology Download the full report for free here: http://bit.ly/Steering_Report_Slideshare

1. EPS Technology Report
By Peter Els & Colin Pawsey
Edited by Will Hornick
Introduction
The electric power steering market is forecast to grow by 13.44% globally by 2016. Power
steering has become so commonplace in our vehicles today that we tend to take it for granted,
but the automotive industry does not stand still, and hydraulic power steering is slowly being
replaced by electric systems.
Previous incarnations of electric power steering systems have been criticised for not giving the
correct ‘feel’ to the driver, and creating a digital, and unnatural experience. The key for OEM’s
and their suppliers is to create systems which generate the right amount of feedback from the
road surface and supply the right amount of torque to the steering wheel. The steering wheel is
the driver’s foremost tool for interaction with the road, and electric systems must give an
accurate representation of a natural driving experience.
That said, the main industry driver for this change to EPS is better fuel efficiency, but the cost of
electric power steering systems could affect the forecast growth. Steering a vehicle is no longer
only about control and driver feedback; in a world of ever diminishing resources, it’s as much
about conserving energy and reducing fuel consumption.
Using a system of electric motor(s), electronic control modules and torque sensors Electric
Power Steering may just fulfil these requirements.
Electric power assisted steering uses an electric motor to provide directional control for the
driver, without any power-draining hydraulic systems, resulting in an improvement in fuel
economy of between 3 and 9 %.
Current EPS architecture
With EPS, sensors detect the motion and torque of the steering column and a computer module
applies assistive power via an electric motor coupled directly to either the steering gear or

2. steering column. Most modern EPS systems have variable assist, which provides speed sensitive
assistance to improve steering effort and feel for the driver.
This functionality requires a delicate balance of power and control that has only been available
in recent years.
Besides electro-hydraulic steering, the most common EPS configurations are:
 Column-assist: The electric motor is mounted on the steering column. The advantage of
this is that, because it’s not mounted in the engine compartment, it’s not exposed to
water and heat. However, noise (often as a result of cogging torque in the permanent
magnet motor) can be a problem as it’s in close proximity to the driver.
 Pinion-assist: The electric motor is mounted where the pinion gear of the rack and pinion
steering system connects to the rack. This systemhas better Noise Vibration and
Harshness characteristics than the Column mounted motor.
 Rackassist: The electric motor is mounted on the rack. An advantage of this system is
that the motor can be mounted anywhere on the rack, thereby simplifying packaging
and fitment.
Image credit: Automotive design and production
Due to their high power density and efficiency, long life, low torque ripple and ease of torque
control, permanent–magnet synchronous DC motors are widely used in EPS systems.
However these motors also have disadvantages such as noise and mechanical vibration as well
as cost. Many of these disadvantages can be reduced or even eliminated by careful engineering
and production of the magnets.