Steering Damping Control via Rack Force Feedback
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Solution Overview
Problem
Existing steering systems for vehicles, particularly those with electromechanical or steer-by-wire systems, face challenges in providing a natural steering feel due to the lack of mechanical coupling. This leads to control stability issues, time delays, and unpredictability in steering torque, especially under varying vehicle conditions such as transverse acceleration and road friction.
Innovation Solution
A method for determining a steering damping requirement that uses the rack force as a primary input, independent of steering feel coordination. This approach eliminates the intrinsic feedback loop present in prior art, allowing for more robust and rapid control of steering damping. Additionally, the method incorporates vehicle speed, steering position, and steering velocity to enhance precision in determining the steering damping requirement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If driver input variables (steering wheel angle, angular velocity, driving torque) are used as input variables for determining return torque, damping torque and hysteresis torque, then the steering feel can be adapted to driver input, but the control mechanism comprises an intrinsic additional loop that reduces control speed and stability
Solution Approach 1:
The patent introduces rack force as an intermediary variable that mediates between the actuator output and the steering feel requirements. Instead of directly using driver input variables that create feedback loops, the rack force serves as an intermediate measurement that reflects the actual mechanical state of the steering system. This intermediary approach allows adaptation of steering feel while avoiding the intrinsic feedback loop problem, as rack force is measured directly from the steering rack rather than derived from driver inputs.
2Ease of operation
If driver input variables are used for determining individual torques, then steering feel can be coordinated, but time delay and control stability are reduced due to the intrinsic feedback loop
Solution Approach 1:
The patent performs preliminary determination of rack force characteristics before the main control loop operates. By pre-characterizing the relationship between rack force and steering feel requirements across different operating conditions, the system avoids real-time calculations that would introduce time delays. The rack force measurements and derived parameters are prepared in advance, allowing the control system to respond more quickly without sacrificing coordination quality.
3Adaptability or versatility
If scaling factors are used to adjust basic steering torque for different vehicle weights, then consistent steering feel can be achieved, but other functions using steering torque as input variable become complex and require high expenditure
Solution Approach 1:
The patent creates a universal rack force-based determination method that serves multiple functions simultaneously. The same rack force measurements and determination logic are used for determining return torque, damping torque, and hysteresis torque, as well as for adapting to different vehicle parameters. This multi-functional approach eliminates the need for separate scaling factor calculations and multiple adaptation mechanisms, reducing overall system complexity while maintaining adaptability to different vehicle configurations.
Data Source
AI summary
The present disclosure relates to a method for determining a steering damping requirement of a steering device of a vehicle, a steering system, a computer program product and a computer-readable storage medium. The steering device is part of a steering system of the vehicle and is coupled to at least one actuator which is configured to apply a steering torque to the steering device. The method comprises at least the step of determining the steering damping requirement based on at least one rack force of the steering system, wherein the steering damping requirement forms at least a portion of a target steering torque with which the steering device can be acted upon by the at least one actuator.