Overview
Steer-by-wire is a safety-critical automotive electronics technology that removes the mechanical link between the steering wheel and the front wheels. When the driver turns the steering wheel, the system converts the motion into an electrical signal, which is sent to steering drive motors that actuate the steering mechanism. Steer-by-wire provides variable steering ratios, allowing the driver to select different driving modes with different ratios. Compared with conventional electric power steering systems, steer-by-wire reduces part count and structural complexity, simplifying the overall architecture and reducing manufacturing time and cost, which benefits high-volume production. By removing the hard mechanical connection between the wheels and the steering wheel, steer-by-wire can deliver a smoother driving experience. On uneven roads the system can reduce wheel vibration and kickback, improving safety and comfort. The system also improves vehicle maneuverability, especially in tight spaces. By using an electronic control unit to precisely command the steer actuators, the system can adapt to different driving conditions and driver styles, providing stable handling.
The following summary is compiled from multiple information sources.
Part 1 — Tesla steer-by-wire system
Physical components
Based on patent descriptions, the production system is consistent with these diagrams. Tesla's steer-by-wire system includes a steering wheel torque feedback actuator assembly, front wheel steering actuator assemblies, power assemblies, the vehicle communication network, and a dedicated communication system. The design increases reliability through redundant components and physical separation. The system may also include a differential gearbox loaded wheel actuator to allow absolute positioning of loaded wheels, and position sensor assemblies that include magnetic and inductive sensors.
There are four controllers: two primary/secondary steering feedback actuator controllers (21A and 21B) for the steering wheel, and primary/secondary road wheel actuator controllers at the actuation layer.
For the Cybertruck, steer-by-wire combined with rear-wheel steering increases flexibility and stability at both low and high speed. At low speed, the rear wheels can steer up to 10 degrees opposite the front wheels, improving maneuverability in tight spaces such as parking lots. At high speed, small rear-wheel adjustments improve stability and smooth lane changes, enhancing overall ride comfort.
As of Q1 2024, Tesla planned to begin deliveries of the first production vehicles equipped with this system.
Part 2 — Design challenges
This topic was discussed previously in the "Zhineng Report" article on steer-by-wire technology trends.
Steer-by-wire also faces several challenges. Its highly integrated electronics and advanced sensors increase R&D and production difficulty, leading to relatively high manufacturing costs. The system is highly dependent on power and electronic components; failures could result in steering loss. At the Shanghai Auto Show, a review of developments by suppliers such as Nexteer showed that Tier-1 suppliers are mainly building R&D capacity. Automakers in the Chinese market will need pioneers like Tesla to take the initial risk before wider adoption.
