Electric Power Steering Damping via Torque and Velocity Estimation

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Solution Overview

Problem

Hydraulic assisted power steering systems provide damping through flow changes, but electric power steering systems lack a similar mechanism, requiring a method to mimic or provide damping effectively.

Innovation Solution

A control system for electric power steering that estimates a damping force based on assist torque, various parameters, and handwheel velocity, generating a control signal to mimic hydraulic damping characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If electric power steering systems are used instead of hydraulic systems, then system complexity and energy efficiency are improved, but damping characteristics are lost

Engineering Contradiction:

Improvesystem complexityVSAvoiddamping characteristics

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The patent calculates and applies damping force based on hydraulic system characteristics by copying the damping behavior formula from hydraulic systems. The control module computes damping force using parameters such as steering angle, steering angular velocity, and vehicle speed, then adds this calculated damping force to the assist torque to reproduce hydraulic-like damping effects in the electric power steering system.

Inventive Principle:

Principle #26Copying

2Force

If hydraulic flow changes are used to provide damping, then damping force is generated, but system complexity increases

Engineering Contradiction:

Improvedamping forceVSAvoidsystem complexity

Core Design Contradiction:

ForceVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical hydraulic damping mechanism with an electronic control system. Instead of using hydraulic flow changes through valve assemblies and cylinder lines, the system uses a control module that calculates damping force based on steering parameters and vehicle speed, then applies the damping torque through electric motor control, thereby eliminating complex hydraulic components while maintaining damping functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If damping is mimicked through control algorithms, then hydraulic characteristics are preserved, but control complexity increases

Engineering Contradiction:

Improvehydraulic characteristicsVSAvoidcontrol complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent changes the control parameters by calculating damping force as a function of steering angle, steering angular velocity, and vehicle speed. The control module dynamically adjusts the damping torque based on these varying parameters, allowing the system to adapt to different driving conditions and reproduce hydraulic-like characteristics through parameter-based control rather than fixed mechanical structures.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP2497697B1Damping methods and systems for electric power steering

Publication Date: 2019.09.04 STEERING SOLUTIONS IP HOLDING CORP

Figure 1A~1B
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AI summary

A control system for controlling an electric power steering system is provided. The control system includes a first module (52) that estimates a damping force (74) based on an assist torque and a handwheel velocity (72). A second module (54) generates a control signal (78) based on the estimated damping force (74).