Automotive Steering Systems
In a typical mechanical steering system the driver’s
steering input is transmitted by a steering shaft through some type of gear reduction mechanism to generate steering motion
at the front wheels.
In the present day automobiles, power steering assist has
become a standard feature. A hydraulic power steering uses hydraulic pressure supplied by an engine-driven pump. Power steering
amplifies and supplements the driver-applied torque at the steering wheel so that steering effort is reduced.
The recent introduction of electric power steering in production
vehicles eliminates the need for the hydraulic pump. Electric power steering is more efficient than conventional power steering,
since the electric power steering motor only needs to provide assist when the steering wheel is turned, whereas the hydraulic
pump must run constantly. The assist level is also easily tunable to the vehicle type, road speed, and even driver preference.
An added benefit is the elimination of environmental hazard posed by leakage and disposal of hydraulic power steering fluid.
The next step in steering system evolution is steer-by-wire
technology.
“by-wire” technology
The substitution of electronic systems in place of mechanical and hydraulic controls is known as “by-wire”
technology. The benefits of applying electronic technology are improved performance, safety and reliability with reduced manufacturing
and operating costs. The idea is not new to airplane pilots and many modern aircraft, both commercial and military, rely on
“fly-by-wire” flight controls (the concept of “flight-by-wire” was introduced by NASA in 1972). However,
only recently has the electronic revolution begun to find its way into automotive systems.
A number of current production vehicles already employ by-wire technology for throttle and brakes. However, steer-by-wire
is a more daunting concept than throttle- or brake-by-wire.
Steer-by-Wire
The aim of steer-by-wire technology is to completely do away
with as many mechanical components (steering shaft, column, gear reduction mechanism, etc.) as possible. Completely replacing
conventional steering system with steer-by-wire holds several advantages, like:
-
The absence of steering column simplifies the car interior
design.
-
The absence of steering shaft, column and gear reduction mechanism
allows much better space utilization in the engine compartment.
-
The steering mechanism can be designed and installed as a
modular unit.
-
Without mechanical connection between the steering wheel and
the road wheel, it is less likely that the impact of a frontal crash will force the steering wheel to intrude into the driver’s
survival space.
-
Steering system characteristics can easily and infinitely
be adjusted to optimize the steering response and feel.
Links
