Power Steering Friction Estimation Model
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Solution Overview
Problem
Existing power steering systems face variability in frictional force due to manufacturing tolerances and wear, leading to inconsistent driving experiences across similar vehicles, with current methods requiring a large number of characterization points and only estimating dry friction values.
Innovation Solution
A method that estimates the immediate frictional force by determining a mathematical model of the power steering system, measuring input and output variables, calculating deviations, and correcting internal parameters using Lyapunov theorem to account for various physical phenomena like lubrication and bonding stiffness, allowing for real-time adjustment of motor torque to achieve equivalent behavior across vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If empirical friction models with multiple characterization points are used, then measurement precision improves, but loss of time increases due to long learning periods
Solution Approach 1:
The patent replaces empirical friction models (which require extensive characterization point collection) with a physics-based dynamic model incorporating Stribeck curve, lubrication effects, and bonding stiffness. This substitution enables immediate friction force estimation without requiring long learning periods, thus resolving the contradiction between measurement precision and time loss
Solution Approach 2:
The patent performs preliminary characterization of friction parameters (Stribeck speed, viscous coefficient, bonding stiffness) during system setup or manufacturing. This preliminary action allows the physics-based model to provide accurate friction estimates immediately during operation, eliminating the need for ongoing empirical learning and characterization point collection
2Reliability
If manufacturing tolerances and wear are accounted for, then reliability improves, but device complexity increases due to parameter variability
Solution Approach 1:
The patent uses a physics-based model with explicit parameters (Stribeck speed, viscous coefficient, bonding stiffness) that can be adjusted to account for manufacturing tolerances and wear. By changing these parameters based on operating conditions and accumulated data, the system maintains reliable and consistent driving experience across vehicles while managing parameter variability through physical constraints rather than complex empirical relationships
3Productivity
If immediate friction force estimation is achieved, then productivity improves, but measurement precision may worsen without sufficient characterization data
Solution Approach 1:
The patent replaces empirical methods requiring extensive data collection with a physics-based dynamic model that provides immediate friction force estimation. The model incorporates fundamental physical phenomena (Stribeck curve, lubrication, bonding stiffness) to achieve both real-time productivity and measurement precision without requiring sufficient characterization data points
Solution Approach 2:
The system uses real-time measurements of motor torque, rotational speed, and acceleration to continuously update and refine friction force estimation through the physics-based model. This self-service approach allows the system to maintain high productivity and precision by leveraging its own operational data within the constraints of the physical model
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides an accurate and immediate estimation of frictional force, reducing the learning time and accounting for multiple physical phenomena, enabling consistent driving experiences across vehicles by adjusting motor torque to compensate for frictional variations.
Implementation Method 1
accounting for various physical phenomena like lubrication and bonding stiffness
Implementation Method 2
estimating an value of a frictional force exerted on a portion of a power steering system
Data Source
AI summary
A method for estimating a value of a friction force exerted on a part of a power steering system of a vehicle, the part of the power steering system including at least one motor exerting a motor torque, the value of the friction force making it possible to modify the motor torque, by means of a mathematical model.