Steer-by-wire Steering Column Using Lateral Acceleration Feedback
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Solution Overview
Problem
Steer-by-wire steering systems lack a natural and intuitive steering feel, as they eliminate mechanical coupling between the steering handle and the wheel actuator, leading to a synthetic feedback that does not accurately represent the vehicle's handling.
Innovation Solution
The system directly converts lateral acceleration into a feedback torque, which is incorporated into the target torque of the haptic actuator, allowing for a more natural and responsive steering feel that mimics conventional mechanical steering systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical coupling between steering handle and wheel actuator is eliminated, then steering handle can move with virtually no resistance, but steering feel becomes synthetic and loses feedback from road surface
Solution Approach 1:
The patent implements feedback by using a lateral acceleration sensor to detect vehicle lateral acceleration and converting it into a feedback torque that is applied to the haptic actuator. This allows the steering handle to provide artificial feedback that represents the vehicle's handling and road conditions, resolving the information loss caused by eliminating mechanical coupling.
Solution Approach 2:
The patent introduces a lateral acceleration sensor and control unit as intermediaries between the wheel actuator and the steering handle. The sensor detects lateral acceleration, the control unit processes this information and converts it to torque, and the haptic actuator applies this torque to the steering handle, creating an intermediary feedback path that replaces the lost mechanical coupling.
2Ease of operation
If haptic actuator is controlled based on estimated steering rack force, then steering feel can be improved, but system complexity and error-proneness increase due to force sensors
Solution Approach 1:
The patent replaces the mechanical force sensor approach with an electronic sensing and calculation system. Instead of using complex force sensors to directly measure rack force, the system uses a lateral acceleration sensor to detect lateral acceleration, then the control unit calculates the corresponding feedback torque based on this acceleration data, substituting mechanical measurement with electronic sensing and computational derivation.
Solution Approach 2:
The patent changes the measurement parameter from direct force measurement to lateral acceleration measurement. The lateral acceleration sensor detects acceleration, and the control unit converts this parameter into the equivalent torque feedback, thereby simplifying the sensing requirement while maintaining the ability to provide appropriate haptic feedback.
3Measurement precision
If lateral acceleration is directly converted into feedback torque, then positioning accuracy of wheel actuator is enhanced, but system complexity increases due to additional calculation modules
Solution Approach 1:
The patent merges the lateral acceleration sensing function with the haptic feedback control function. The lateral acceleration sensor is integrated into the steering system, and the control unit that converts lateral acceleration to feedback torque is combined with the existing haptic actuator control, creating a unified control system that enhances positioning accuracy without requiring entirely separate systems.
Data Source
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AI summary
A steer-by-wire steering system (1) for a motor vehicle comprises a steering handle (2) for inputting a steering command by a driver of the motor vehicle, a haptic actuator (3) mechanically coupled to the steering handle (2) for simulating steering feedback for the driver at the steering handle (2), a wheel actuator (4) for setting a steering angle at steerable vehicle wheels (5) of the motor vehicle, control means (6) configured to cause the wheel actuator (4) to effect steering action of the vehicle wheels (5) and the haptic actuator (3) to generate steering feedback, the control means (6) comprising a first calculation module (8) for the steering feedback provided by the haptic actuator (3) and a second calculation module (9) for the steering angle to be set by the wheel actuator (4), and both (8,9) or at least the second calculation module (9) is connected as an input variable to a quantity representing the steering command, as well as a device for determining the lateral acceleration (a) of the vehicle. The control means (6) are configured such that the lateral acceleration (a) is directly converted into a feedback torque (Sa) and this feedback torque (Sa) is included in the first calculation module (8), either entirely or with a scaling factor greater than 0 and less than 1, as a summand in a target torque (SH) of the haptic actuator (3) representing the steering feedback.