Empirical Friction Model for Power Steering via Scatter Points
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Solution Overview
Problem
Accurately determining and managing friction forces within power steering mechanisms is challenging due to their variability over time and dependence on wear and environmental conditions, affecting driving comfort and steering system responsiveness.
Innovation Solution
A method involving the acquisition of characterization points across a range of assistance force values to construct an empirical friction model, correlating friction values with assistance force measurements, allowing for a comprehensive and reliable mapping of friction phenomena across various life situations, including real-time adaptation to changes in the steering mechanism's condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single friction measurement is taken to simplify the model construction, then the device complexity is reduced, but the measurement precision and reliability deteriorate due to noise and measurement errors
Solution Approach 1:
The friction characterization is segmented into multiple discrete measurement points across different assistance force values. Instead of using a single measurement, the method divides the characterization into N distinct points, each providing information about friction at a specific operating condition. This segmentation allows the system to capture the non-linear behavior of friction while maintaining manageable complexity through systematic data collection and correlation law establishment.
Solution Approach 2:
The method changes the assistance force parameter to multiple different values during measurement to capture the variation of friction with operating conditions. By measuring friction at N different assistance force values, the system establishes a correlation law that accounts for parameter changes, thereby improving measurement precision and reliability without excessive complexity.
2Reliability
If multiple characterization points are collected to improve model reliability, then the measurement precision and robustness are enhanced, but the loss of time and measurement complexity increase
Solution Approach 1:
The friction characterization measurements are performed in advance during system operation or calibration phases. The N characterization points are collected beforehand to establish the correlation law, so that once the model is built, friction can be accurately determined in real-time without requiring continuous multi-point measurements. This preliminary action reduces the time penalty during actual operation.
Solution Approach 2:
The method enables continuous updating of the friction model by periodically collecting new characterization points and refreshing the correlation law. This continuous action ensures the model remains reliable over time as the steering mechanism ages or operating conditions change, while the established correlation law allows rapid processing of the collected data to minimize time loss.
3Adaptability or versatility
If friction measurements are taken frequently to capture real-time variations, then the adaptability to wear and environmental conditions is improved, but the productivity and system response time deteriorate
Solution Approach 1:
The friction model is designed to be dynamic, allowing updates as new characterization points are collected during operation. The correlation law can be refreshed periodically or when significant changes in operating conditions are detected, enabling the system to adapt to wear and environmental changes without requiring constant recharacterization. This dynamic approach maintains adaptability while preserving steering system productivity.
Data Source
AI summary
A method for evaluating the frictions in a power steering mechanism, the method including a step of acquiring a series of characterization points, during which are measured, for several different values taken successively by the assistance force during the operation of the steering mechanism, the corresponding friction values, so as to empirically obtain a series of distinct characterization points each associating a measured friction value to a measured value representative of the assistance force, then a step of constructing an empirical friction model, during which a correlation law is established between the characterization points constitutive of the series of characterization points, from the scatter chart formed by the series of the characterization points.