Electric Power Steering Backup Control With Adaptive Fault Thresholds

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Solution Overview

Problem

Conventional electric power steering apparatuses face issues with erroneous abnormality detection during backup control, where the same threshold value used for normal conditions can lead to incorrect determination of abnormalities, causing unnecessary shutdowns or continued operation with faults.

Innovation Solution

The electric power steering apparatus introduces an abnormality control mode that adjusts the control amount and threshold values based on the specific abnormality detected, ensuring accurate determination of additional abnormalities and preventing erroneous shutdowns by dynamically changing the threshold values during backup control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the same threshold value is used for abnormality detection during both normal control and backup control, then the abnormality detection mechanism remains simple, but erroneous abnormality determination occurs during backup control leading to unnecessary shutdowns or continued operation with faults

Engineering Contradiction:

Improveabnormality detection mechanismVSAvoidabnormality detection accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies dynamics by making the threshold value changeable based on the control mode. The threshold is dynamically adjusted to be higher during backup control than during normal control, allowing the system to adapt to different operational conditions and prevent erroneous abnormality determination while maintaining reliable fault detection

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of the threshold value based on the control mode. By setting different threshold levels for normal control and backup control, the system accurately distinguishes between normal variations during backup operation and actual abnormalities, preventing false shutdowns while maintaining detection sensitivity

Inventive Principle:

Principle #35Parameter changes

2Productivity

If backup control is implemented to continue motor operation during sensor abnormality, then the steering assist can be maintained, but the risk of undetected additional abnormalities increases

Engineering Contradiction:

Improvesteering assist continuityVSAvoidsafety against undetected faults

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements feedback by continuously monitoring sensor values during backup control and comparing them against mode-appropriate thresholds. This feedback mechanism enables the system to detect additional abnormalities that occur during backup operation while maintaining steering assist functionality, balancing productivity and safety

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent prepares for potential additional abnormalities by establishing a higher threshold specifically for backup control mode before such faults occur. This preemptive measure cushions against erroneous determination when additional faults happen during backup operation, allowing continued safe operation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentEP3605834B1Electric power steering device

Publication Date: 2025.01.01 MITSUBISHI ELECTRIC CORP

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AI summary

When detecting an abnormality in a portion related to control of an electric motor, a CPU that calculates a control amount for controlling the electric motor calculates a control amount different from a control amount at a normal time so as to continue the control of the electric motor and changes a threshold value for detecting the abnormality to a value different from a value at a normal time.