Steer-by-Wire Torque Feedback via Low-Pass Filtering
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Solution Overview
Problem
Steer-by-wire steering systems lack a realistic steering feel due to the absence of direct mechanical feedback between the steering wheel and steered wheels, leading to a perceived synthetic or numb steering experience, and the division of software implementations between control units can cause synchronicity issues affecting the steering feel.
Innovation Solution
A method for operating a steer-by-wire steering system that involves detecting the current steering wheel angle and position to determine a target steering wheel torque, which is low-pass filtered and used to provide feedback to the steering wheel, enhancing the dynamic behavior and accounting for external forces, thereby creating a more realistic steering feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the steering torque is calculated and artificially applied via the steering wheel actuator in a steer-by-wire system, then the positioning of steered wheels is achieved, but the steering feel is perceived as synthetic or numb
Solution Approach 1:
The patent implements a feedback mechanism where the actual steering torque from the steering actuator is measured and fed back to the steering wheel actuator. This creates a closed-loop system that reproduces the tactile feedback normally provided by mechanical linkage, allowing the driver to feel road conditions and steering forces authentically rather than receiving artificial torque calculations.
Solution Approach 2:
The patent replaces the traditional mechanical feedback linkage with an electromechanical system. Sensors measure the actual steering torque, and this information is transmitted electronically to control the steering wheel actuator, substituting direct mechanical coupling with an electronic feedback loop that achieves the same tactile communication function.
2Device complexity
If the steering system uses separate control units for steering wheel actuator and steering actuator with data exchange via communication path, then functional decoupling is achieved, but synchronization problems occur leading to sluggish steering feel
Solution Approach 1:
The patent merges the control functions of the steering wheel actuator and steering actuator into a unified control system. By integrating the control units, the system eliminates communication delays and synchronization issues between separate controllers, ensuring that steering torque calculations and actuator responses occur in tight coordination without lag.
3Measurement precision
If steer-by-wire system eliminates mechanical linkage between steering wheel and steered wheels, then steering assistance precision is improved, but direct mechanical feedback is lost resulting in numb steering experience
Solution Approach 1:
The patent uses feedback from torque sensors to measure the actual forces applied to the steered wheels and feeds this information back to the steering wheel actuator. This allows the system to maintain precise electronic control while reproducing the tactile sensations of road conditions and steering resistance that would otherwise be lost without mechanical linkage.
Solution Approach 2:
The patent introduces an intermediary feedback mechanism that mediates between the steering wheel actuator and steering actuator. The torque sensor and control system act as intermediaries to translate and transmit steering forces electronically, replacing the direct mechanical intermediary of the traditional linkage with an electronic feedback intermediary.
Data Source
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AI summary
The invention relates to a method for operating a steer-by-wire steering system (1) comprising a steering device (3) with a steering actuator (34) for setting a steering angle of steered wheels (32) and a steering wheel device (2) for applying a steering wheel torque to a steering wheel (21), having the following steps: - detecting a current steering wheel angle (LRW); - regulating a steering position depending on the current steering wheel angle (LRW) and depending on an actual steering position (IZP) in order to obtain a target steering control variable (SZK) as a control variable for actuating the steering actuator (34), and - determining a target steering wheel torque (SLRM) for actuating the steering wheel actuator (25) depending on the target steering control variable (SZK).