Electric Power Steering Hands-Off Detection

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Solution Overview

Problem

Existing electric power steering systems face challenges in accurately determining whether a driver is holding the steering wheel, particularly when torque values fluctuate due to road conditions, leading to potential errors in hands-off detection and instability in lane keeping control systems.

Innovation Solution

An electric power steering apparatus and control method that utilize a steering torque model equation to calculate a steering torque model value, employing first and second reference torque values and counters to differentiate between holding and non-holding states, thereby reducing errors in hands-off detection and ensuring accurate determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single threshold value is used for hands-off detection, then the detection process is simple, but errors occur when torque values temporarily vary due to road conditions

Engineering Contradiction:

Improvedetection process complexityVSAvoidhands-off detection accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The single threshold value is segmented into multiple threshold values (first threshold, second threshold, third threshold) that are applied at different stages of the detection process. This segmentation allows the system to differentiate between temporary torque variations and genuine hands-off states, thereby improving detection accuracy while maintaining a structured approach to complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs preliminary actions by setting multiple threshold values before the actual hands-off detection occurs. These pre-established thresholds (first, second, and third thresholds) prepare the system to handle various torque scenarios, enabling more reliable detection without adding complex real-time decision logic.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If torque sensor output values are directly compared with threshold values, then the determination process is straightforward, but errors arise when steering torque values temporarily vary according to road conditions

Engineering Contradiction:

Improvedetermination process simplicityVSAvoidsteering wheel holding state detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The system dynamically adjusts the detection criteria by using multiple threshold values instead of a fixed single threshold. The first threshold is used for initial comparison, the second threshold for intermediate states, and the third threshold for final determination. This dynamic multi-threshold approach maintains operational simplicity while significantly improving measurement precision in varying road conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the parameter of threshold values from a single static value to multiple static values that are selectively applied. By having first, second, and third threshold values available, the system can adapt its detection criteria to different torque scenarios, improving precision without making the operation overly complex.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a single reference torque value is used for hands-off detection, then the control system is simple, but erroneous determination occurs when torque signals temporarily vary

Engineering Contradiction:

Improvecontrol system complexityVSAvoidholding state determination accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The single reference torque value is segmented into multiple reference torque values (first reference torque, second reference torque, third reference torque) that are used at different stages of the determination process. This segmentation enables the control system to handle temporary torque variations more reliably while maintaining a manageable level of complexity through a structured multi-stage approach.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control system performs preliminary actions by establishing multiple reference torque values before the hands-off determination is needed. These pre-set reference values (first, second, and third) allow the system to systematically evaluate torque signals against multiple criteria, improving reliability without requiring complex real-time adjustments.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9868464B2Electric power steering apparatus and control method thereof

Publication Date: 2018.01.16 HL MANDO CORP

AI summary

The present invention relates to an electric power steering apparatus for determining whether a driver keeps hold of a steering wheel and a control method thereof that can calculate a steering torque model value from a steering torque value, steering torque information, and a steering torque model equation, and can accurately determine whether the driver keeps hold of the steering wheel by using a result obtained by comparing the steering torque model value with first and second reference torques and the counter value of a counter that is updated according to the comparison result.