The concept of drive-by-wire control technologies, adapted from the fly-by-wire systems used in modern aircraft, allows car interiors to be completely redesigned. Paul Stevens reports that both active and passive safety can be improved by removing the traditional symbol of the automobile: the steering wheel.

Earlier this year at the Hanover Fair a concept vehicle was unveiled to demonstrate the possibilities of drive-by-wire technologies. In principle these are similar to the fly-by-wire systems used on state-of-the-art commercial and military aircraft, whereby adjustments made to the controls are translated into electrical signals that are conveyed to distributed actuators - a far cry from the traditional mechanical and hydraulic links.
The use of drive-by-wire technology in cars is not just technology transfer for the sake of it; there are many reasons behind the movement away from conventional systems towards new alternatives.
One of the most often quoted is safety: a vehicle's controls are, by definition, safety-critical, so anything that reduces response times or improves ergonomics can be seen as a safety improvement. But one of the main benefits of using drive-by-wire systems is that the steering wheel can be replaced by a side-mounted joystick or other appropriate device.
Steering wheels are the cause of many crushing injuries sustained by drivers - though the use of airbags has reduced the frequency and severity of such injuries - but eliminating steering wheels would remove an entire category of potential injuries.

Improving fuel consumption

Automotive manufacturers are also concerned with improving fuel consumption, especially in Europe where fuel is taxed more highly than in the USA and other regions, so there is a huge incentive to reduce vehicle weight. The hope is that electronic systems will weigh less than the mechanical and hydraulic systems that they replace.
Furthermore, electrical systems can be inherently more energy-efficient than hydraulic systems. For example, whereas a hydraulic power steering pump will need to operate continuously (and therefore consume energy continuously) to provide the necessary pressure, an electrical system would only be powered when required.

Inside story

One way in which the weight of a vehicle can be reduced is to decrease the overall size. This implies that the best possible use must be made of the interior space, which is something that drive-by-wire technology can enable.
If there is no longer a steering wheel and set of pedals, the area in front of the driver can be used better. Indeed, drive-by-wire technology allows designers the freedom to completely reconsider the interior layout of vehicles.
The car shown at the Hanover Fair certainly does have a unique interior. Known as the Bertone-SKF Filo concept car, it incorporates drive-by-wire controls for steering, accelerator, brakes, gear change and clutch
(Fig. 1).
All of the main controls are installed in a revolutionary control console called the Guida-Filo, which is mounted in the centre of the vehicle (Fig. 2). This frees the space in front of the driver and has allowed the designers to create a floor that has large ridges on which the driver and passenger may rest their feet; no longer is the driver constrained to have his or her feet positioned where the pedals are situated.
Moreover, the driver does not need to move the seat backwards or forwards to reach the steering wheel and pedals, so the front seats have been redesigned as a single bench seat, likened to a lounge sofa by Bertone (Fig. 3).

Audio systems

To enhance the vehicle occupants' environment further, the Filo has a customised high-performance audio system developed by the Automotive Systems Division of the Bose Corporation.
One possibility would be for the driver or passengers to download music or video from the internet - either by streaming data or by downloading 'one-time play' music or video files - and the sound system can provide the same surround-sound quality as is currently provided by leading-edge home cinema equipment. The Filo also has a concept telephone from Nokia that is built into the Guida-Filo, offering not only voice communications but also data, such as traffic reports, weather forecasting, remote vehicle diagnostics, and tourist information relating to sites being driven past.
Stile Bertone, the Italian-based automotive design house, worked closely with SKF on the Filo project. Sarma, SKF's avionics and aerospace division, provided much of the technology behind the Guida-Filo control console.
Another partner, Brembo, helped to develop the braking system that is claimed to rival the performance of conventional hydraulic systems, with the weight of the electro-mechanical actuating units also comparing favourably with conventional hydraulically-actuated callipers.
Compact geared electric motors are equipped with ball and roller screws to convert the rotary motion into linear motion for the brake pads. Sensors monitor the position of the actuators and the applied forces so that small actuators in the Guida-Filo can provide tactile feedback for the driver, who applies the brakes by squeezing the grips on the Guida-Filo. This principle of providing feedback is important and has also been used with other controls, such as the steering.
The left and right steering yokes are linked mechanically, but the movement is controlled by software, based on the angle through which the driver moves the controls, and other factors including the road speed.
The level of 'feel' experienced by the driver is fully programmable, as is the relationship between the movement of the controls and the response at the wheels.

Pluses and minuses

Although the automotive industry now has various alternative technologies available for providing automated gear changes, including traditional epicyclic gearboxes and modern electronically-controlled continuously variable transmissions, the Filo concept car uses a drive-by-wire manual gearbox and clutch arrangement.
Based on conventional major components, the new actuation system has to execute precise linear and rotary movements to mimic the driver's use of a conventional H-pattern gear selector lever.
However, instead of being presented with a lever, the driver simply has plus and minus buttons on the control console for changing up and down gears; neutral is a logical zero, and reverse is selected by means of a dedicated button - though inappropriate selection is prevented by software logic. The clutch is operated automatically using another smart electro-mechanical actuator.
While safety is seen as one of the main driving forces behind the development of drive-by-wire technologies, many potential purchasers may view this radical use of computers with scepticism, believing it to be less safe than conventional mechanical and hydraulic systems. One way to help overcome these fears may be to introduce the developments in a progressive way.
For instance, it could be that a steering wheel could be used, but with the mechanical linkage replaced with a by-wire system. Similarly, a brake pedal could be equipped with a position/force sensor and feedback actuator, rather than being connected to a hydraulic brake circuit.
Introducing changes such as these could give the driver the same look and feel as a conventional car's controls, but with the new technology operating in the background.
This would not be the approach that eager engineers would wish to see, but the marketing experts may insist that it is the only way. Meanwhile we can all enjoy studying concept cars and dreaming of what life may be like in the future without a steering wheel.