Modified LuGre Model Friction Compensation for Steering Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power steering systems face issues with pronounced loss of torque during constant cornering and high sensitivity to road surface conditions when adjusting friction using the LuGre model, leading to suboptimal driver feedback.
Innovation Solution
A method that determines adjusted friction in a power steering system using a modified LuGre model, incorporating a state-based equation with a time derivative and adjustable coefficients to minimize torque loss and surface sensitivity, involving measurements of speed and steering wheel torque to calculate the optimal friction compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If friction is adjusted using the LuGre model, then driver feeling is improved, but torque loss becomes too pronounced in constant cornering
Solution Approach 1:
The patent modifies the LuGre model by changing the parameter structure to include a beta coefficient that adjusts the relationship between friction and velocity. This parameter change allows the system to reduce torque loss during constant cornering while maintaining improved driver feeling, as the modified model can adapt friction compensation based on operating conditions rather than applying fixed compensation
2Ease of operation
If friction is adjusted using the LuGre model, then driver feeling is improved, but sensitivity to road surface conditions becomes too high
Solution Approach 1:
The modification introduces a beta coefficient that changes how friction compensation responds to velocity changes. This parameter adjustment dampens the system's sensitivity to road surface variations while preserving the improved driver feedback, as the modified model smooths the friction compensation response based on the relationship between beta and velocity
3Ease of operation
If the amount of compensated friction is increased, then driver feeling is improved, but torque loss and surface sensitivity increase
Solution Approach 1:
The patent transforms the static friction compensation approach into a dynamic one by introducing velocity-dependent adjustment through the beta coefficient. This allows the system to optimize friction compensation in real-time based on operating conditions, maintaining high driver feedback quality while reducing excessive torque loss and surface sensitivity that occur with fixed high-level compensation
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
The method effectively reduces torque loss and sensitivity to road conditions, enhancing driver feedback by accurately adjusting friction based on system state and speed measurements, particularly when the coefficient β is close to 1, thereby improving the overall performance of the power steering system.
Implementation Method 1
determining the friction to be adjusted on the basis of a modified LuGre model, said modified LuGre model determining the friction to be adjusted as a function of a state z of the system, a time derivative ż of the state z of the system being determined as a function of said state and of the speed v
Data Source
AI summary
Method for determining a friction to be adjusted in a power steering system or for modifying a hysteresis of a steering wheel torque applied to a steering wheel of the power steering system, the method including the following steps of: determining a speed, from a measurement of a speed of a part of the power steering system and/or a measurement of the steering wheel torque; determining the friction to be adjusted on the basis of a modified LuGre model, said modified LuGre model determining the friction to be adjusted as a function of a state of the system, a time derivative of the state being determined as a function of said state of the system, the speed, a first gain, and a coulomb friction, according to an equation of the form:z.=v(1-α(z,v)σ0zFcsign (v)).[Math 1]