Does electric power steering mean that a motor does the steering of the front wheels? If so, what happens when the battery is weak or the motor fails? Will I be left with no steering control?
Actually, what you are referring to is "power-assisted" electric steering. There is a motor but its function is to "assist" the driver by providing a torque to the steering shaft every time there is an angular movement of the steering wheel.
With some cars, a weak battery will cause the motor to be a little lethargic, resulting in noticeably heavier steering - especially during quick manoeuvres.
On the other hand, if there is a total failure of electric motor, the steering wheel becomes heavy to turn. This also happens if you try to turn the steering before starting up the engine.
In any case, every mechanical element linking the steering wheel to the front wheels remains unbroken and hence the front wheels can still be controlled if power assistance is lost.
Almost every carmaker now employs electric power-assisted steering instead of the traditional hydraulic power-assisted system. The latter comprises several more components, including an engine-driven pump which robs power.
An electric motor is compact, lightweight, efficient and can be more precisely controlled. Carmakers are beginning to use the steering's electric motor in systems where steering intervention is incorporated to enhance safety.
For example, in an accident avoidance manoeuvre when the driver's steering input could be sudden and sharp, the system intervenes to moderate steering action and reduces the risk of skidding.
Of worthy mention is Infiniti's direct adaptive steering, which actually decouples the mechanical link and is essentially a drive-by-wire system. But even in this unique system, an electrical system failure reverts the entire system to direct mechanical control.