Steering Position Control With Friction Feedforward Compensation

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Solution Overview

Problem

Existing steering systems face challenges in precise position control due to hysteresis caused by rack inertia, damping, and friction forces, leading to tracking errors, especially in reverse maneuvers like lane keep assist and adaptive cruise control.

Innovation Solution

Implementing a friction compensation-based feedforward component using a Lugre model to the PID controller, which generates a friction compensation command based on target pinion velocity and temperature, reducing reverse delay and improving tracking performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a PID controller is used for steering system position control, then the system is simple to implement, but tracking precision deteriorates due to friction-induced hysteresis and reverse delay

Engineering Contradiction:

Improvecontroller implementation simplicityVSAvoidposition tracking precision

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The friction compensation term is calculated in advance based on the desired pinion velocity and added to the PID control output. This preliminary compensation action counteracts the friction effects before they cause tracking errors, particularly improving reverse direction response without complicating the overall control structure

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control approach changes from pure PID to PID plus friction compensation by introducing velocity-dependent and temperature-dependent friction parameters. This parameter enhancement maintains the simplicity of PID while adding precision through modeled friction characteristics

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If friction compensation based on velocity and temperature is implemented, then position tracking precision is improved, but device complexity increases

Engineering Contradiction:

Improveposition tracking precisionVSAvoidcontrol system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Physical friction effects are replaced by a computational friction compensation model that uses velocity and temperature parameters. This substitution eliminates the need for complex mechanical friction reduction mechanisms while achieving similar效果 through software-based compensation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

A friction compensation term acts as an intermediary between the PID controller and the steering system. This intermediary component processes velocity and temperature inputs to generate compensation signals that correct friction-induced errors without directly modifying the physical steering mechanism

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If PID control is used without friction compensation, then the control algorithm is computationally simple, but reverse delay increases

Engineering Contradiction:

Improvecontrol computation efficiencyVSAvoidreverse direction delay

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The friction compensation is continuously updated based on real-time velocity and temperature measurements, creating a periodic correction cycle that actively counteracts friction effects during steering operations, especially during reverse direction transitions

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS20250353545A1Systems and methods for optimized position control using friction feedforward compensation

Publication Date: 2025.11.20 STEERING SOLUTIONS IP HOLDING CORP

AI summary

A method for steering system position control includes receiving a target angle for a pinion of a rack of a steering system, receiving an actual angle of the pinion, and determining an angle error value based on a difference between the target angle and the actual angle. The method also includes providing the angle error value to a proportional-integral-derivative (PID) controller, receiving a target velocity of the pinion, and generating a friction compensation value based on the target velocity. The method also includes generating a control command value based on an output of the PID controller and the friction compensation value, and controlling at least one aspect of the steering system based on the control command value.