Steer-by-Wire Feedback Actuator Torque Limiting
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Solution Overview
Problem
Steer-by-wire steering systems lack reliable feedback mechanisms to provide a safe and realistic steering feel to drivers, which is critical for vehicle control and safety, especially during cornering and varying road conditions.
Innovation Solution
A method and system that calculates and adapts motor torque for a feedback actuator using a control unit, incorporating steering functions for damping, hysteresis, and center return, with limiter mechanisms to ensure safety levels, based on vehicle conditions and driver inputs, to simulate a conventional steering experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback actuator is used to provide steering feel in a steer-by-wire system, then the driver receives realistic road feedback, but the system may produce unsafe or unpredictable steering movements
Solution Approach 1:
The patent applies preliminary action by calculating and limiting the maximum permissible engine torque before it is applied to the feedback actuator. The control unit determines the base engine torque based on vehicle conditions, then proactively limits this torque to a safe maximum value before the actuator executes the steering action. This prevents unsafe steering movements from occurring in the first place, rather than reacting to them after they occur.
Solution Approach 2:
The system implements feedback by continuously monitoring vehicle conditions (speed, steering angle, acceleration) and using this information to dynamically adjust the maximum permissible engine torque. The control unit receives feedback from sensors about the current driving state and modifies the torque limit accordingly, ensuring the feedback actuator provides realistic steering feel while maintaining safety under all operating conditions.
2Force
If the feedback actuator provides strong steering feel to simulate road conditions, then the driver experiences realistic feedback, but the steering torque may become excessive and unsafe
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the maximum permissible engine torque parameter based on vehicle operating conditions. The control unit calculates the base engine torque required for realistic steering feel, then modifies this parameter by applying a limit to ensure it does not exceed safe values. The limited engine torque is determined as a function of vehicle speed, steering angle, and acceleration, allowing the system to provide strong but safe steering feedback across different driving scenarios.
3Adaptability or versatility
If multiple steering functions are combined to provide comprehensive steering control, then the system offers enhanced functionality, but the complexity of ensuring safety across all functions increases
Solution Approach 1:
The patent applies merging by combining multiple steering functions (steering damping, hysteresis, center return) into a single integrated control approach. Instead of separately managing safety for each function, the system calculates the base engine torque that incorporates all desired steering characteristics, then applies a unified limitation to ensure the combined output remains safe. This consolidates the complexity into a single safety mechanism rather than requiring separate safety systems for each function.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for controlling a steer-by-wire steering system for motor vehicles, comprising a steering adjuster (3) which acts on the steered wheels and is electronically controlled as a function of a driver's steering request, a feedback actuator (2) which transmits feedback from the street to a steering wheel, and a control unit (5) which controls the feedback actuator (2), wherein the following method steps are provided for calculating an engine torque (TFBA): determining a basic engine torque (Tbasic); providing at least one steering function (9,10,11) which is part of a first subgroup of steering functions (8); limiting the initial value of the at least one steering function (9,10,11) for reaching a predetermined safety level in a first limiter (13); adapting the basic engine torque (Tbasic) by means of the limited initial value of the at least one steering function in a summer (19); actuating the feedback actuator (2) with the resulting engine torque (TFBA)·output by the summer (19).