Steer-by-Wire Rack Force Damping for On-Center Steering Feel
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing steer-by-wire steering systems lack effective damping, particularly in the on-center region, leading to inconsistent steering feel and input impedance.
Innovation Solution
Implement a method and system that generate damping torque using a two-dimensional lookup table varying with vehicle speed, adding rack force values to the effort function to create a more uniform damping effect, enhancing steering system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional steer-by-wire steering systems are used without effort-based damping, then the system structure remains simple, but damping is insufficient particularly in the on-center region leading to inconsistent steering feel
Solution Approach 1:
The patent applies parameter changes by modifying the rack force signal through multiplication with a damping factor derived from handwheel velocity and vehicle speed. The damping factor is calculated as a function of these parameters, and the modified rack force signal is then used to generate the effort command. This dynamic parameter adjustment provides speed-dependent damping that improves steering feel consistency without requiring additional hardware components.
Solution Approach 2:
The patent replaces mechanical damping mechanisms with an electronic control system that calculates and applies damping forces through signal processing. Instead of using physical dampers or mechanical friction elements, the system uses computational methods to generate damping torque based on sensor inputs (handwheel velocity, vehicle speed) and mathematical relationships, thereby achieving damping functionality through electronic means rather than mechanical components.
2Reliability
If speed-dependent damping is implemented using handwheel velocity and vehicle speed, then damping performance improves particularly in on-center region, but calculation complexity increases
Solution Approach 1:
The system uses self-service by leveraging existing sensor data (handwheel velocity and vehicle speed) that are already available in the steer-by-wire system for other control functions. Rather than requiring additional sensors or measurement systems, the damping calculation reuses these existing signals, and the controller simultaneously performs multiple control tasks including damping, steering assist, and stability control, making the system self-sufficient and reducing overall complexity.
Solution Approach 2:
The patent implements speed-dependent damping by dynamically changing the damping factor based on vehicle speed and handwheel velocity parameters. The damping factor is calculated as a function of these parameters, allowing the system to automatically adjust damping characteristics according to operating conditions without requiring complex lookup tables or iterative calculations.
3Stability of the object's composition
If rack force signal is modified by adding damping value, then steering system provides more consistent input impedance, but the control algorithm becomes more complex
Solution Approach 1:
The patent replaces complex mechanical impedance matching mechanisms with an electronic control algorithm that calculates the required effort command to achieve desired input impedance characteristics. The system uses signal processing and mathematical relationships to generate damping torque that maintains consistent input impedance across different operating conditions, avoiding the need for complex mechanical linkages or variable stiffness mechanisms.
Solution Approach 2:
The control algorithm modifies the rack force signal by applying a damping factor that is a function of handwheel velocity and vehicle speed. This parameter-based approach allows the system to dynamically adjust the effort command to maintain consistent input impedance characteristics without requiring complex iterative optimization or adaptive control algorithms.
Data Source
AI summary
A method for rack force effort-based damping includes: receiving a handwheel velocity signal associated with rotational motion of a handwheel of a vehicle; determining a vehicle speed; identifying, in a rack force look-up table, a rack force value based on the handwheel velocity signal and the vehicle speed; generating a modified rack force signal by adding the rack force value to a rack force signal; identifying, in an effort look-up table, an effort value based on the modified rack force signal; and selectively controlling at least one aspect of a steering system based on the effort value.