Citroen Develops Drive-by-Wire System for Mainstream Family Sedan

Brake-by-Wire, Drive-by-Wire, Steer-by-Wire: whats next - Fly-by-Wire? Known as X-by-Wire, its one of the latest technological trends to hit theautomotive industry, and its taking it by storm. Engineers have found ways to make cars safer, more fuel efficient and more reliable by eliminating mechanical links between driver and car. Citroen, French conglomerate and self-proclaimed mad scientist of the car world has long worked on a Fly-by-Wire system suitable for cars. Through its C-Crosser and C-Airdream concepts, it has developed an electronically controlled steering, gas and brake system, which it has transplanted into its C5 family sedan. The result is a unique, one-off prototype called the C5-by-Wire.

On the outside, the C5-by-Wire looks completely like a normal C5 hatchback, except for the silver and light blue decals which adorn its tall sides. Its powered by a conventional engine, which drives the front wheels through an automatic gearbox, and aside from the fact that it has seats that vibrate should you cross over a traffic lane unintentionally, and that its one of the only vehicles in the world available with a body roll, pitch and dive-removing hydropneumatic suspension system, its a completely normal vehicle. One could relate it to the automotive equivalent of a cyborg - normal on the outside, but completely mechanical and far more advanced underneath.

The main thing thats different about the C5s interior is its unconventional steering wheel. Having hacked off the top and bottom arches of the wheel, it looks more like a video game console handset than a steering wheel. The controls for the missing pedals appear present on the steering wheel, making the C5 a car which can be operated completely with your hands. Throttle is controlled by two paddles which are actuated by the drivers left or right thumbs - to accelerate, or speed up, the driver pushes the paddle outwards. To ease the strain on wary thumbs, automatic cruise control kicks in making the task of sustaining speed easy. Braking is also done with ones fingers, and is controlled by two triggers, operated by the drivers index fingers. With a half inch of travel, the driver simply squeezes on the triggers to slow the vehicle.

To ensure that the C5s steering system is intuitive and ergonomic, Citroens engineers have placed two sets of controls on the left and right hand sides of the steering wheel. This allows the driver to accelerate, brake, or maintain speed while operating the vehicles other controls, such as headlights, horn, turn signals, as well as stereo and climate control. As proven by its studies, this new system of throttle and brake control is easy to use, and while its different than the conventional gas and brake pedal, Citroen claims that drivers feel comfortable after spending just a short amount of time behind the wheel.

Considering that half the steering wheel is missing, the C5-by-Wire is slightly different to steer than normal vehicles. Drawing from its parts bin, Citroen used electrical power steering to replace the conventional hydraulic pump and mechanism for the C5s steering system. Not only does the electric motor power the rack, but it also adjusts the steering wheel to wheel angle ratio, according to the drivers input and the vehicles speed. This means that a quarter turn on the steering wheel wont always equal to a quarter turn in all circumstances. The system is capable at generating a turn ratio of 3:1, which means that for every three turns of the wheel in a normal car are closer to one turn of the C5s quasi steering wheel. Aside from eliminating aggressive arm-over-arm maneuvers which can be quite dangerous during driving, the system makes parking and low-speed cornering easier, while keeping the steering pin-sharp at higher speeds.

Theres no denying that the C5s Fly-by-Wire system is an innovation in technology, but part of the drive to develop it was for safety reasons. While the steering wheel provides greater visibility of the instrumentation and the road ahead, more importantly, it does not have a metal steering column which can intrude into the cockpit, causing serious injury. The removal of the pedals offers similar benefits: reduced risk of foot and leg injury should a serious collision occur. The Fly-by-Wire system also has other active safety benefits, helping the driver to focus on the road, as well as reducing overall braking distances by eliminating the reach for the brake pedal during accident avoidance or panic stops saving precious time and distance.

While the C5-by-Wire focuses on passive collision safety and improved driver ergonomics, this kind of technology wont be showing up on production cars for at least another five to ten years. Ground breaking leaps forward often come at a price: as weve already seen with Mercedes-Benz and the massive product range wide Brake-By-Wire recall, there is still one last hurdle for Citroen to bypass: a failsafe mechanism. Without any in place, a failure of any electrical system could prove to be catastrophic. The initial developments as seen in the C5-by-Wire are present but, it will still be some while before all systems are truly go with Fly-by-Wire for cars.