Drive-by-Wire

T

he Drive-by-Wire system is used to describe those electronic systems that replace the mechanical linkages between the controls of the car and the oily bits that do the work. An electronic throttle control system has been in use for a number of years by some manufacturers, including the Saab 9-3’s diesel models (my TiD being one); this is one example of a Drive-by-system.

One of the great advantages for the decision to use drive-by-wire control systems is that the computer(s) responsible for interpreting what the driver input is and what he or she really means are able to work the throttle, steering, suspension and brakes work together to give the car better handling, especially in bad road conditions. They should also be able to give lower fuel consumption and to react to emergencies faster than a human driver could. Though the car would look much the same it would contain a computer network.

Electronic Throttle Control

As I’ve written above, Saab’s TiD has an electronic throttle control. In the Saab this works very well – unless you knew it had it, you wouldn’t know. Volkswagen’s electronic throttle control system in the Polo, however, is appalling. Read all about it here.

Electronic throttle control systems are more expensive than conventional cable systems but make it significantly easier and cheaper to integrate additional features, such as cruise control, traction control and stability control. The reasons why these are easier to integrate are because the engine power is moved irrespective of the position of the accelerator pedal.

Brake-by-Wire

As the time of writing, brake-by-wire technology is still under development by many manufacturers and is not yet in widespread use. This is mostly because of its safety-critical nature! Mercedes-Benz use it on their E-Class and I’ve sampled it; the hardest thing to get used to is that you don’t need to lift off the brake pedal as you’re about to stop to avoid that nasty jerk as the car does this for you.

Brake-by-wire systems need many redundant systems plus some clever logic programming to make a best guess in the event of a failure somewhere.

Steer-by-Wire

Steer-by-Wire systems could potentially do away with many mechanical components such as the steering shaft, column and gear reduction mechanism. This could allow for a stronger chassis, a safer passenger compartment (as there’s no steering wheel to hit the driver) and potentially more space for a bigger engine. It would also be possible to fine tune or modify the steering system characteristics so as to change how the car feels on the road.

There are currently no production cars using a Steer-by-Wire system that I am aware of.