Drive by wire
Drive by wire or DbW technology in the automotive industry is the use of electronic or electro-mechanical systems in place of mechanical linkages that control driving functions. Drive-by-wire may refer to just the propulsion of the vehicle through electronic throttle control,[2] or it may refer to electronic control over propulsion as well as steering and braking, which separately are known as steer by wire and brake by wire, along with electronic control over other vehicle driving functions.[3]
Driver input is traditionally transferred mechanically to the motor and wheels through a steering wheel and steering column, throttle, hydraulic brakes, brake pull handles and so on. In drive-by-wire systems, driver input is processed by an electronic control system which controls the vehicle using electromechanical actuators. The human–machine interface, such as a steering wheel, yoke, accelerator pedal, brake pedal, and so on, may include haptic feedback that simulates the resistance of hydraulic and mechanical pedals and steering. Components such as the steering column, intermediate shafts, pumps, hoses, belts, coolers, vacuum servos and master cylinders are eliminated from the vehicle. Similarly, fly-by-wire systems are widely used in the aviation industry. Safety standards for drive-by-wire are specified by the ISO 26262 standard level D.
Properties
Dispensing with mechanical linkages has several advantages: it reduces complexity and simplifies assembly; simplifies service and tuning; reduces the force required to engage inputs and allows it to be customized with haptic technology; allows for more interior design freedom in the placement of input mechanisms; allows for automation of driving functions; reduces cabin noise by eliminating the acoustic linkage to the drive systems; and by reducing floor openings it improves the crash behavior of the vehicle.[4] Because driver inputs can be overridden, safety can be improved by providing computer controlled intervention of vehicle controls with systems such as electronic stability control (ESC), adaptive cruise control and lane assist systems.[5]
Each drive-by-wire system leads to more actuator in the vehicle and therefore a greater energy consumption. For instance, the drive-by-wire technology adds actuator motors to create the torque needed to turn the wheels, and a feedback transducer to create the "road feel" on the steering wheel.
Safety considerations require redundancy of driver input sensors, vehicle communication networks, actuators,[4] and other systems. Automotive safety standards such as ISO 26262 require drive-by-wire fail-operational and fail-safe behaviors.[6]
Safety and security
Failures in drive by wire systems can lead to potential hazardous situations where safety depends entirely on the vehicle's failure mode. The Aachen University Institute for Motor Vehicles (ika - Institut für Kraftfahrzeuge), in collaboration with Mercedes-AMG and others, studies the operation, risks, and safety mechanisms of drive-by-wire systems through its drive-by-wire concept vehicle, SpeedE. Studied scenarios include loss of control over acceleration, brakes, or steering.[1]
Early by-wire systems had mechanical backup systems in case the by-wire systems failed.[2] The modern drive by wire paradigm dispenses with mechanical backups, and relies on redundancy fail-safes and other safety and security measures: computational redundancy through lockstep CPUs; functional redundancy through modular design where the failure of one module is compensated by an identical module, for example by torque vectoring to compensate for a failed steering or braking module; multi-sensor fault detection; self-isolation of damaged systems; and fault-tolerant communication. Such fail-safes are specified by the ISO 26262 standard level D.[6]
Assessment and standardization of drive-by-wire computer security has also taken place. Researchers demonstrated in 2011[7] and 2013[8][9] that some systems in commercially-available vehicles are susceptible to hacking, allowing for external control of the vehicle. Hacking demonstrations included remote activation of systems like the horn, windshield wipers, accelerator, brakes, and transmission.[9] Modern standards such as the ISO/SAE 21434 standard and UNCE regulations 155, 156, and 157 require dedicated cryptographic modules that encrypt all communication between the ECUs and the drive system components.[2]
Systems
Brake by wire
A pure brake by wire system would eliminate the need for hydraulics completely by using motors to actuate calipers, in comparison to the currently existing technology where the system is designed to provide braking effort by building hydraulic pressure in the brake lines
Park by wire
The parking pawl in a traditional automatic transmission has a mechanical link to the gear lever and locks the transmission in the park position when the vehicle is set in Park. A park by wire system uses electronic commands to actuate the parking pawl by a motor when the driver puts the vehicle in park.
Shift by wire
The direction of motion of the vehicle (Forward, Reverse) is set by commanding the actuators inside the transmission through electronic commands based on the current input from the driver (Park, Reverse, Neutral or Drive).
Steer by wire
A vehicle equipped with a steer-by-wire system is able to steer some or all of its wheels without a steering column connected to the wheel axles. It is different from electric power steering or power-assist, as those systems still rely on the steering column to mechanically transfer some steering torque to the wheels.[11]
A vehicle with a steer-by-wire system may be manually controlled by a driver through a steering wheel, a yoke, or any other steering apparatus which is connected to one or more electronic control units, which uses the input to control steering actuators that turn the wheels and steer the vehicle. The steering wheel or yoke may be equipped with haptic feedback to simulate road feel and wheel resistance, and change depending on the vehicle speed or customizable settings.[11][12]
Throttle by wire
This system helps accomplish vehicle propulsion by means of an electronic throttle without any cables from the accelerator pedal to the throttle valve of the engine. In electric vehicles, this system controls the electric motors by sensing the accelerator pedal input and sending commands to the power inverter modules.
References
- ^ a b SpeedE - Forschungsplattform, ika - Institute for Motor Vehicles of RWTH Aachen University, 2016
- ^ a b c d Scheibert, K., Kostarigka, A., Dannebaum, U., Ambekar, A. et al., "Challenges with the Introduction of X-By-Wire Technologies to Passenger Vehicles and Light Trucks in regards to Functional Safety, Cybersecurity and Availability," SAE Technical Paper 2023-01-0581, 2023, doi: 10.4271/2023-01-0581 .
- ^ Arjun V. Pillai (November 18, 2022), "Overview of drive by wire technologies in automobiles", AIP Conference Proceedings, 2452 (1), International conference on smart grid & electric vehicle (ICSGEV 2021) 15–16 July 2021 Tamil Nadu, India, doi:10.1063/5.0113232
- ^ a b Harald Naunheimer; et al. (2011), "9.1.3 Shift-by-Wire", Automotive Transmissions: Fundamentals, Selection, Design and Application (Second ed.), Springer, doi:10.1007/978-3-642-16214-5, ISBN 978-3-642-16213-8
- ^ Austin Weber (March 26, 2010), "Wire Processing: Drive-by-Wire", Assembly Magazine
- ^ a b Arunkumar Sampath, "Toward functional safety in drive by wire vehicles" (PDF), Mobility Engineering (December 2020)
- ^ Checkoway, Stephen. "Comprehensive Experimental Analyses of Automotive Attack Surfaces". YouTube. Archived from the original on 31 May 2017. Retrieved 23 August 2018.
- ^ Greenberg, Andy. "Hackers Reveal Nasty New Car Attacks--With Me Behind The Wheel (Video)". Archived from the original on 2017-08-25. Retrieved 2017-08-26.
- ^ a b Greenberg, Andy. "Hackers Remotely Kill a Jeep on the Highway—With Me in It". Archived from the original on 2017-01-19. Retrieved 2017-03-06.
- ^ "Uniti Sweden: the diversity behind the electric car of the future", Euronews, April 8, 2017
- ^ a b Chris Perkins (March 17, 2023), "How Toyota Is Making the Case for Steer-By-Wire", Road & Track
- ^ Jancer, Matt. "Take a Look Inside the First Steer-by-Wire Car". Archived from the original on 2014-03-16. Retrieved 2017-03-06.
