Electric Power Steering Control via Torque Sensor Failure Compensation

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Solution Overview

Problem

Existing electric power steering control systems fail to provide a continuous steering assist force when a torque sensor breaks down, leading to potential accidents due to incorrect or absent steering assist forces.

Innovation Solution

A method and apparatus that utilize steering angle information and vehicle speed information to calculate and provide a continuous steering assist force by calculating self-aligning torque, damping force, inertial force, and frictional force, even in the absence of torque sensor data, using a breakdown detection unit, information reception unit, compensation target value calculation unit, and current controller.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the torque sensor is used to measure driver's steering torque, then the steering assist force can be accurately controlled, but the system fails when the torque sensor breaks down

Engineering Contradiction:

Improvesteering torque measurement accuracyVSAvoidsystem reliability under torque sensor failure

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces intermediate parameters (steering angle, vehicle speed) as mediators to calculate the compensation target value when the torque sensor fails. Instead of directly measuring steering torque through the failed sensor, the system uses these intermediary measurements to compute the required steering assist force through calculation, thereby maintaining system reliability while the torque sensor is non-functional

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the measurement parameters from direct steering torque (which requires the torque sensor) to steering angle and vehicle speed (which can be measured by other sensors). By transforming the problem from torque measurement to parameter-based calculation, the system maintains operational capability even when the torque sensor breaks down

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the power steering control stops supplying steering assist force when torque sensor breaks down, then the system avoids erroneous control, but the driver experiences sudden loss of steering assist

Engineering Contradiction:

Improvecontrol accuracyVSAvoidsteering operation smoothness

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent performs preliminary action by pre-calculating the compensation target value using steering angle and vehicle speed information before the complete loss of steering assist occurs. This allows the system to smoothly transition to alternative calculation methods and maintain steering assist force without abrupt interruption, ensuring ease of operation while preserving control reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent ensures continuity of useful action by implementing a seamless transition from torque-sensor-based control to compensation-target-value-based control. The steering assist force continues to be supplied without interruption or abrupt change, maintaining both control reliability and steering operation smoothness during the sensor failure condition

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If alternative calculation methods are implemented for torque sensor failure, then continuous steering assist is provided, but the device complexity increases

Engineering Contradiction:

Improvesteering assist continuityVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements universality by designing a control system that can function in multiple modes: normal mode using torque sensor data and failure mode using compensation target value calculation. The same control apparatus performs both torque-based control and parameter-based control, reducing the need for separate systems and minimizing additional complexity while ensuring steering assist continuity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent applies self-service by enabling the control system to automatically detect torque sensor failure and switch to alternative calculation methods without external intervention. The system monitors its own operational status and autonomously transitions to the compensation mode, maintaining reliability while avoiding the complexity of external monitoring and manual switching mechanisms

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS9522696B2Method and apparatus for controlling electric power steering

Publication Date: 2016.12.20 HL MANDO CORP

AI summary

The present invention relates to a method and apparatus for controlling electric power steering. In particular, the present invention provides a power steering control method that includes: a breakdown detection step of detecting whether a torque sensor has broken down; an information reception step of receiving steering angle information and vehicle speed information in the case in which the torque sensor has broken down; a compensation target value calculation step of calculating a self-aligning torque, and a damping force, an inertial force, and a frictional force of an electric power steering apparatus by using one or more of the steering angle information and the vehicle speed information; and a current control step of calculating a steering assist force based on the compensation target value and controlling the supply of a motor control current that corresponds to the steering assist force, and an apparatus for the same.