by Larry Carley c2005.
I had the opportunity to experience first-hand SKF's "drive-by-wire" technology that may eventually replace traditional mechanical-based steering and braking systems. The vehicle I drove is the Novanta concept car, built by Bertone (the famous Italian automotive designers), and the location was SKF's North American Technical Center in Plymouth, Michigan.
SKF, who is best known as a leading supplier of wheel bearings, is also a pioneer in adapting aerospace fly-by-wire technology to future automotive applications. The Bertone concept car, which first debuted at the 2002 Geneva auto Show, was created around SKF's prototype steer-by-wire, brake-by-wire and unique throttle control systems to illustrate the design freedom and possibilities these new technologies offer.
The bright orange Novanta concept car has a futuristic yet contemporary look that is more evolutionary than revolutionary. The car is built on a SAAB 95 chassis with a 3.0L V6 engine and automatic transmission. It's fully driveable (unlike many concept cars) but lacks basic amenities that would be on a real production car such as air conditioning, windshield wipers, external mirrors and cup holders.
The real story is inside this vehicle. When you open the door, you immediately notice there is no steering column. Also absent are the gas and brake pedals. There's not even a gear shift. Novanta relies entirely on drive-by-wire technology from SKF to control all major driving systems.
Eliminating many of the constraints imposed by traditional mechanical systems, drive-by-wire technology allowed the Bertone designers to rethink all of the structural elements of the interior and to create a very open and unique driving environment. Compared to most of today's vehicles, the interior is almost spartan. There is no bulky dash to protrude into the passenger compartment, only a few simple control buttons, and a single LCD display panel located in a strip that wraps across the front of the passenger compartment.
When the driver enters the vehicle and closes the door, the "Guida" driver control unit folds out of the door on a pivot arm. The unit resembles the steering controls that one might find on a video arcade flying game. Steering, throttle control, braking and transmission mode selection are on the driver control unit. The steering yokes have twist handles that control vehicle acceleration somewhat like the twist-throttle on a motorcycle, and the brakes are applied by squeezing paddles on the backs of the yokes.
The driver control unit is connected via a closed loop control circuit to the main steering Smart Electro-Mechanical Actuating Unit (SEMAU). An motorized actuator inside the driver control unit generates feedback when the wheels are steered to simulate steering effort and road feel. Driving this vehicle feels a little awkward at first because of the unfamiliar controls. But once you get the hang of using the twist grips to accelerate and squeezing the grips to brake, it's as easy to drive as any vehicle with conventional steering and brakes.
The SKF steer-by-wire system uses a smart electro-mechanical steering actuator instead of a conventional rack and pinion gear. The electric motor that moves the rack to either side is wrapped around the rack for a very compact design. There is no power steering pump, no pressure hoses, no steering shaft and no physical connection between the driver's hands and the front wheels. Sensors on the steering yokes send the driver's steering inputs to a processor, which monitors and controls the position of the front wheels. A feedback loop keeps the wheels and steering inputs in sync with one another, while redundant circuits provide a failsafe backup should anything go wrong.
The braking system is also fully electronic with no hydraulics, no master cylinder, no brake lines and no physical connection between the driver's foot and the brakes. The calipers are electro-mechanical, developed jointly by Brembo and SKF. An electric motor squeezes the pads against the rotors when the brakes are applied. Braking inputs from the driver steering yokes are routed to a controller that functions like a power-assist antilock brake system. The system reacts much more quickly to driver inputs than a conventional hydraulic system, and can modulate braking as needed depending on driving conditions and traction. The system can also be programmed to provide traction control and stability control as well.
Novanta also has an electronic parking brake system that automatically locks the rear wheels when the vehicle is stopped and placed in park. The electronic parking brake can also be programmed to prevent the vehicle from rolling backwards or forward when stopping on a hill, and to prevent vehicle theft (by locking the wheels).
For more information about the Novanta and SKF's drive-by-wire technology, visit the SKF website.