Electric Steering Motor Current Control for Vibration Mitigation

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Solution Overview

Problem

Current electric power steering systems fail to effectively mitigate smooth road shake (SRS) vibrations, which are caused by irregular road surfaces and internal imbalances, leading to customer complaints and reduced driving comfort.

Innovation Solution

A control algorithm is implemented in the Electronic Control Unit (ECU) that adjusts motor current based on torque signals and gain calculations from sensors, using a processor and torque sensor to minimize steering wheel vibrations by applying frequency-dependent gains to reduce vibrations at specific frequency ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional EPS control algorithms are used, then the system maintains basic steering functionality, but steering wheel vibrations (smooth road shake) occur and cannot be effectively mitigated

Engineering Contradiction:

Improvesteering wheel vibrationsVSAvoiddriving comfort

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The control algorithm dynamically adjusts motor current based on real-time vibration detection. The system continuously monitors steering wheel vibrations and modifies motor current in response to detected vibration frequencies, transforming the static control system into a dynamic one that adapts to changing road conditions and vibration patterns.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system implements a feedback mechanism where vibration sensors detect steering wheel vibrations, the control algorithm processes this information, and the motor current is adjusted accordingly. This closed-loop feedback enables the system to detect and respond to smooth road shake conditions, continuously optimizing steering assist to reduce vibrations.

Inventive Principle:

Principle #23Feedback

2Object-affected harmful factors

If motor current is increased to reduce vibrations, then vibration mitigation improves, but system stability and performance may be compromised

Engineering Contradiction:

Improvevibration reductionVSAvoidsystem stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The control algorithm modifies motor current parameters dynamically based on detected vibration characteristics. By changing current magnitude and frequency characteristics in response to vibration detection, the system achieves vibration reduction while maintaining overall stability through controlled parameter adjustment rather than sustained high current.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system applies periodic motor current adjustments synchronized with detected vibration frequencies. This periodic action counteracts the vibrations through anti-resonance, reducing smooth road shake while maintaining system stability by applying corrections only when and where needed, rather than continuous high-current operation.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS8335611B2Methods and systems for controlling motor current in steering systems of vehicles equipped with electric steering assist

Publication Date: 2012.12.18 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method of controlling a motor current for a vehicle having a motor and a steering system includes the steps of obtaining a torque signal from the steering system, calculating a torque, and adjusting the motor current based at least in part on the torque signal, the torque gain, or both.