Automotive Steer-By-Wire (SBW) System | Composition, Principle & Features
An automotive steer-by-wire (SBW) system consists of three main components: a steering wheel assembly, a steering execution assembly and a main electronic control unit (ECU), as well as auxiliary systems including an automatic fault prevention system and a power supply system.
Overview
An automotive steer-by-wire (SBW) system is composed of three core components: a steering wheel assembly, a steering execution assembly and a main ECU, along with auxiliary systems such as an automatic fault prevention system and a power supply.
The steering wheel assembly includes a steering wheel, a steering wheel angle sensor, a torque sensor and a steering wheel return torque motor. Its primary function is to convert the driver's steering intention (by measuring the steering wheel angle) into digital signals and transmit them to the main ECU. Meanwhile, it receives torque signals from the main ECU to generate steering wheel return torque, providing the driver with corresponding road feel information. The steering execution assembly comprises a front wheel angle sensor, a steering execution motor, a steering motor controller and front wheel steering components, among others. It accepts commands from the main ECU and controls the rotation of the steering wheels via the steering motor controller to realize the driver's steering intention.
The main ECU analyzes and processes the collected signals to determine the vehicle's motion state, and sends instructions to the steering wheel return torque motor and the steering execution motor to control their operation. This ensures the vehicle delivers an optimal response under all working conditions, reducing the driver's need to compensate for changes in the vehicle's steering characteristics with speed and lightening the driver's burden. Additionally, the controller can identify the driver's operation instructions and judge whether the steering operation is reasonable under the current state. When the vehicle is in an unstable state or the driver issues an incorrect instruction, the SBW system will block the incorrect steering operation and automatically perform stability control to restore the vehicle to a stable state as soon as possible.
The automatic fault prevention system is a crucial module of the SBW system, which includes a series of monitoring and implementation algorithms. It responds to different fault types and levels with corresponding processing measures to maintain the normal driving of the vehicle to the maximum extent. As one of the most widely used means of transportation, vehicle safety must be the primary consideration and the foundation of all research. Therefore, automatic fault detection and processing are among the most important components of the SBW system. It adopts rigorous fault detection and processing logic to further improve vehicle safety performance.
The power supply system is responsible for supplying power to the controller, the two execution motors and other on-vehicle electrical appliances. The maximum power of the front wheel angle execution motor alone ranges from 500W to 800W, and together with other electronic devices on the vehicle, the power supply is under considerable load. Therefore, to ensure the stable operation of the power grid under heavy loads, the performance of the power supply is particularly important.
Working Principle
The vehicle steering system is a key component that determines the active safety of a vehicle. The traditional automotive steering system is a mechanical system: the driver manipulates the steering wheel, and the steering motion is transmitted to the steering wheels through the steering gear and a series of linkages. The automotive SBW system eliminates the mechanical connection between the steering wheel and the steering wheels, realizing steering entirely by electrical energy. It breaks free from the various limitations of traditional steering systems, allowing for the free design of both the force transmission characteristics and the angle transmission characteristics of vehicle steering. This brings unlimited possibilities to the design of vehicle steering characteristics and represents a major innovation in automotive steering systems.
The working principle of the automotive SBW system is as follows: Sensors detect the driver's steering data, which is then transmitted to the on-vehicle ECU via a data bus, and feedback commands are obtained from the steering control system. The steering control system also receives the driver's steering instructions from the steering control mechanism and wheel status information from the steering system, thereby commanding the movement of the entire steering system. The steering system controls the wheels to turn to the required angle and feeds back the wheel angle and rotation torque to other parts of the system, such as the steering control mechanism, to provide the driver with road feel. The intensity of this road feel can be controlled by the steering control system according to different conditions.
Characteristics
Enhanced vehicle safety performanceThe removal of mechanical connections such as the steering column completely avoids injury to the driver from the steering column in collision accidents. The intelligent ECU judges the rationality of the driver's operation based on the vehicle's driving state and makes corresponding adjustments. When the vehicle is in extreme working conditions, it can automatically perform stability control on the vehicle.
Improved driving characteristics and maneuverabilityThe steering ratio (the ratio of steering wheel angle to wheel angle) is dynamically adjusted based on vehicle speed, traction control and other relevant parameters. At low speeds, the low steering ratio reduces the steering wheel rotation angle required for turning or parking; at high speeds, the increased steering ratio ensures better straight-line driving performance.
Optimized driver's road feelSince there is no mechanical connection between the steering wheel and the steering wheels, the driver's "road feel" is generated by simulation. The system can extract information that best reflects the actual vehicle driving state and road conditions from the signals and use it as a control variable for the steering wheel return torque. This ensures the steering wheel only provides the driver with useful information, thus delivering a more realistic road feel.
Composition
Essentially, a steer-by-wire system consists of two key components: a steering wheel module (also known as a steering wheel actuator) and a steering module (also known as a wheel actuator). The steering wheel module is mounted on the upper steering column and includes a traditional steering wheel, sensors that detect steering angle, steering force or steering torque, and an electric motor that generates an appropriate steering feel for the driver.