Electric Power Steering (EPS)

Overview

As part of efforts to make their vehicles more environmentally friendly, carmakers have increasingly been switching from hydraulic steering assist systems to electric power steering (EPS) using electric motors in order to reduce weight and boost fuel efficiency. In recent years there is a trend toward linking functions that assist the driver in operating the vehicle to the EPS system, for example by providing continuously variable steering gear ratio adjustment according to the running speed and steering angle, in addition to simple power shift functionality. This creates demand for MCUs capable of supporting sophisticated motor control with features such as high-performance CPU, large memory capacity, dedicated timer units, high-speed, high-precision A/D converters, and interfaces for communicating with other control units.In addition, the ISO 26262 functional safety standard for the automotive field is scheduled to take effect in 2011 amid rising concerns over vehicle safety. Systems that require the highest level of safety, such as the steering and brakes, typically require compliance with ASIL-D,* the highest safety level. This has led to demand for MCUs incorporating safety mechanisms such as redundant cores.
Renesas supplies optimized solutions to support system advances, based on technology such as high-performance lock step dual CPU cores.

* ASIL: Automotive Safety Integrity Level.
ASIL-D is the highest Automotive Safety Integrity Level.

System Block Diagram