Drive by wire
From Wikipedia, the free encyclopedia
Drive-by-wire, DbW, by-wire, or x-by-wire technology in the automotive industry replaces the traditional mechanical and hydraulic control systems with electronic control systems using electromechanical actuators and human-machine interfaces such as pedal and steering feel emulators. Hence, the traditional components such as the steering column, intermediate shafts, pumps, hoses, fluids, belts, coolers and brake boosters and master cylinders are eliminated from the vehicle.
Examples include electronic throttle control and brake-by-wire.
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[edit] Advantages
Safety can be improved by providing computer controlled intervention of vehicle controls with systems such as Electronic Stability Control (ESC), adaptive cruise control and Honda's Lane Keeping Assist System (LKAS).
Ergonomics can be improved by the amount of force and range of movement required by the driver and by greater flexibility in the location of controls. This flexibility also significantly expands the number of options for the vehicle's design.
Parking can be made easier with reduced lock-to-lock steering wheel travel as with BMW's Active Steering System, or automatic parallel parking which is available in some Toyota Prius models and newer European Volkswagen models. Although neither of these are strictly Steer-by-Wire (SbW) because they retain mechanical linkages, they show the capabilities that are possible.
[edit] Disadvantages
The cost of DbW systems is often greater than conventional systems. The extra costs stem from greater complexity, development costs and the redundant elements needed to make the system safe. Failures in the control systems can result in an unstoppable runaway vehicle - if the throttle, ignition and transmission are all beyond the direct control of the driver there is no effective way to stop the vehicle in such an event.
[edit] Steer by Wire
This is currently used in electric forklifts and stockpickers and some tractors[1]. Its implementation in road vehicles is limited by concerns over reliability although it has been demonstrated in several concept vehicles such as ThyssenKrupp Presta Steering's Mercedes-Benz Unimog, General Motors' Hy-wire and Sequel and the Mazda Ryuga. A rear wheel SbW system by Delphi called Quadrasteer is used on some pickup trucks but has had limited commercial success.
Competitors in the DARPA Grand Challenge, an automated driving competition, relied on 100% DbW systems, in some cases including a SbW system provided by the manufacturer [2].
[edit] Toyota Prius
As of 2005, the Toyota Prius is the most prominent example of DbW technology, featuring electronic throttle, brake and transmission control. This is largely by necessity of the Hybrid Synergy Drive system, which assigns complete engine control and regenerative/friction braking decisions to a hybrid control computer. Further extending the DbW, in Europe and Japan automatic parking assist is also available — the car can control the steering to guide itself backwards into a parking space.
[edit] The future
Some fanciful theories and applications abound as to what the ultimate implications of DbW technology might be. It has been suggested that DbW might allow a car to become completely separate from its controls, meaning that a car of the future might theoretically be controlled by any number of different control systems: push buttons, joysticks, steering wheels, or even voice commands — whatever device that designers could come up with. This would have many advantages, such as:
- increased flexibility for handicapped or disabled drivers
- less weight in the car
- more space in the car
