Lexus made news earlier this year for beating Tesla in launching an electric vehicle with a steer-by-wire system. The Lexus RZ 450e is a battery electric SUV featuring an optional steer-by-wire system named ‘One Motion Grip’ which incorporates a steering yoke instead of the traditional steering wheel.
The RZ 450e is the first Lexus electric vehicle to be built from the ground up, and Lexus engineers aimed to reduce steering effort while maintaining steering feel. They improved the precision of steering control and speed of steering response by eliminating the traditional steering column and mechanical link. The One Motion Grip system relies on an electrical connection to send inputs from the steering wheel and wheels on the road. The system requires only a 150-degree turn of the yoke to move from the straight ahead to left or right lock, eliminating the need for hand-over-hand turns.
As steering feel is important for driver confidence and control, the system provides steering feedback at all times, maintaining a strong connection between the driver and car. The driver will notice less steering wheel sway when travelling over rough roads, stable control and correction in strong crosswinds, and straight-line performance on angled surfaces. A fail-safe provision of processors and an emergency power supply is included, should the system lose its principal power supply.
The RZ is also the first production model to feature Lexus’s new Direct4 system, working with the two e-Axles. Direct 4, an exclusive Lexus technology, is an intelligent system that constantly balances the traction of all four wheels, automatically and seamlessly distributing drive force. Direct4 uses ECU sensors to collect, evaluate and react to a range of factors, including vehicle speed, steering angle, and G forces. From these inputs, it calculates and immediately applies the appropriate drive torque to each e-Axle to maximise grip and traction. The front/rear torque bias can be adjusted from zero to 100 or 100 to zero in milliseconds, which is faster than any mechanical system. Thus, Direct4 also improves steering response with better communication between the road and steering wheel or yoke.
While Lexus may be the first car manufacturer in the world to introduce a steer-by-wire system with a steering yoke, x-by-wire technology, itself, is not new. Nissan was among the world’s first manufacturers to introduce a steer-by-wire system in a production car, the Infiniti Q50. Several car manufacturers are testing by-wire systems with plans to start serial production in the next two years.
Thyssenkrupp Presta AG, one of the world’s largest suppliers of steering systems for the automotive industry, expects the first production models that rely exclusively on steer-by-wire to roll out from 2023. Having completed eight decades in the steering business, Thyssenkrupp Presta is betting big on the future of steer-by-wire solutions. The company estimates that there’ll be at least around one million steer-by-wire vehicles on the roads worldwide by 2030.
The benefits of x-by-wire, a generic term for steer-by-wire, brake-by-wire, drive-by-wire, etc., are numerous. Steering by wire or data cable allows completely new vehicle architectures to be designed, as well as leading to greater standardization in vehicle construction and shorter development times. Numerous vehicle categories and layouts can be created on one and the same platform. For example, the position from which the vehicle is steered becomes completely irrelevant. No company has explored this possibility more than Paravan, the global market leader for customized vehicle adaptations and drive-by-wire steering and driving controls for the disabled.
Paravan’s drive-by-system name ‘Space Drive’ is an electronic driving and steering system that has been on the market for almost 20 years. Currently, more than 9,000 vehicles operate on the road with Space Drive technology, completing over 1 billion kilometres driven ‘by-wire’.
To demonstrate the possibilities of the Space Drive, Paravan converted a Tesla Model 3 car by removing its steering wheel and brake pads and allowing the vehicle’s steering and braking functions to be controlled entirely using a small joystick in the centre console. The joystick allows the driver to sit anywhere in the car and opens up the possibility of completely new interior concepts in vehicles.
Roland Arnold, founder and CEO of Paravan, says: “It is no coincidence that this technology comes from the world of disabled mobility. A person with restricted mobility or little strength cannot simply grab the steering wheel when the technology fails. He or she must be able to rely on our technology one hundred percent.”
As vehicles become increasingly electrified, automated, and software controlled, by-wire technology is expected to play an increasingly pivotal role in all aspects of vehicle motion control – longitudinally, transversely and vertically.
ZF Friedrichshafen (ZF) is developing and industrializing advanced chassis systems with a comprehensive offering of by-wire technologies that no longer require a mechanical connection or system fluids. The company recently presented its advanced steer-by-wire technology for the front axle, positioning itself to achieve fully automated by-wire vehicle control through an offering that includes:
• Steer-by-wire including rear wheel steering
• Brake-by-wire with integrated brake control
• Electronically controlled active suspension
These technologies are being combined to yield system solutions that offer enhancements greater than they can alone. Here software and combined E/E architectures play a key role in adding value.
By-wire systems offer greater degrees of vehicle control offering shorter stopping distances, more degrees of freedom in manoeuvring, better stability at high speeds and greater range and efficiency. The amount of steering assist or brake torque can be tuned to mimic the typical feel that drivers expect but can also be instantly adjusted to enhance brake force to reduce stopping distances or steer around an obstacle more expertly than drivers can do themselves.
ZF’s steer-by-wire systems enable fully autonomous vehicle control for shuttles and robotaxis. For personal passenger vehicles, it also offers unique capabilities like retractable steering wheels for fully automated driving modes, fully adaptable steering control reducing the steering wheel angle for parking or low-speed manoeuvres and enhanced crash safety through the removal of the steering column.
ZF’s brake-by-wire IBC braking system enables regenerative braking and energy recuperation that helps recharge the batteries of electric vehicles, highlighting how chassis and e-drives can work together to enhance motion control, extend range and offer more compact system packaging.
To future-proof the technology, ZF is enabling the new generation software supporting the by-wire actuators to be updated over-the-air at any time.
ZF revealed that it has been awarded significant volume contracts by several major car manufacturers aiming to launch by-wire systems in all major regions in 2023.
Wolf-Henning Scheider, CEO, ZF Friedrichshafen AG, says: “Smart by-wire systems end the era of mechanical connections and enable a new era of vehicle control. ZF’s steer-by-wire technology enables new safety and comfort features, like autonomous emergency evasive manoeuvres or parking in very confined spaces. This is an important precondition for advanced automation in passenger cars and trucks and also a breakthrough for new design and engineering freedom. In line with our ‘develop once, deploy anywhere’ guiding philosophy, by-wire technologies will also be applied to commercial vehicle automation.”
Delivery trucks and vans
Israel-based REE Automotive is introducing by-wire technology in two of its vehicles, the class 5 Proxima van and class 3 P7-B box truck.
REE uses x-by-wire technology to control each of the corners of the vehicles with full drive-by-wire, brake-by-wire and steer-by-wire systems, which reduces underfloor turbulence and enables the design of a low and flat load floor.
The Proxima is being developed as the first drive-by-wire, fully electric, walk-in step van. The vehicle features an EAVX and Morgan Olson body design and is powered by REE’s modular P7 platform.
The P7 platform is intended to power class 3–5 vehicles with payloads up to 3,600 kg (8,000 pounds), along with all-wheel steering and all-wheel drive.
REE’s REEcorner technology packs critical vehicle components (steering, braking, suspension, powertrain and control) into a single compact module positioned between the chassis and the wheel, enabling REE to build flat EV platforms with more room for passengers, cargo and batteries.
Each REECorner is completely independent and powered by its own REEcorner ECU, with a REEcenter ECU controlling all corner level functions including fully sprung high RPM electric motor; single wheel steer-by-wire technology; single wheel brake-by-wire technology; multi-ratio high efficiency drivetrain; high power ECU architecture; preventive maintenance AI; and over-the-air updates.
The P7-B box truck, also built on the P7 platform, offers increased interior space for passengers and cargo and a low step-in height while targeting a maximum speed of 120 km/h, max range of 241 km, up to 2,000 kg payload, and gross vehicle weight ratings (GVWR) of up to 6,350 kg.
The full x-by-wire architecture supports all-wheel steer, all-wheel drive, adaptive regenerative breaking, creep control, hill start assist, and torque vectoring as standard as well as over-the-air updates.
Tactical combat vehicles
American Rheinmetall Vehicles, a developer of tactical wheeled and tracked combat vehicles and systems has formed a strategic collaboration with GM Defense to compete in the U.S. Army’s Common Tactical Truck (CTT) programme which seeks to identify a replacement platform for the army’s family of heavy tactical vehicles.
Rheinmetall recently unveiled its HX3, next-generation series of truck with advances in power, mobility, advanced driver assistance systems (ADAS), drive-by-wire operation and an open systems architecture with pathways to hybrid technology incorporation, leader follower driving, and autonomous operations.