Electric Power Steering Current Control for Smooth Centering

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Solution Overview

Problem

Electric power steering systems generate a catching feeling when the steering wheel is rotated from the ends to the center due to reduced auxiliary torque, which is not effectively mitigated by existing rack end stop functions.

Innovation Solution

An electric power steering apparatus that includes a torque sensor, a steering sensor, and an electronic control unit to adjust the current supplied to the motor based on the signals from these sensors, ramping up the current when the steering wheel is rotated from the ends to the center to prevent a catching feeling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the rack end stop function is used to reduce current supplied to the motor before mechanical contact, then the steering wheel mechanical contact is prevented, but a catching feeling is generated when the steering wheel is rotated from the ends to the center

Engineering Contradiction:

Improveprevention of mechanical contactVSAvoidsteering smoothness

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The control unit performs preliminary action by detecting the steering wheel rotation direction and position before mechanical contact occurs. When rotation is detected from the end toward the center, the control unit proactively increases the current supplied to the motor to generate sufficient auxiliary torque, preventing the catching feeling before it occurs. This preliminary detection and response resolves the contradiction by maintaining smooth steering operation while preventing mechanical contact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies dynamics by dynamically adjusting the current supplied to the motor based on real-time detection of steering wheel rotation direction and position. The control unit changes the current magnitude according to the detected rotation state - increasing current when rotating from the end toward the center, and reducing current when approaching the end position. This dynamic adjustment resolves the contradiction by adapting the motor output to the specific operational context.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the current supplied to the motor is reduced to prevent mechanical contact, then the auxiliary torque is reduced, but the steering wheel rotation becomes less responsive

Engineering Contradiction:

Improveprevention of mechanical contactVSAvoidsteering wheel rotation speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The control unit applies local quality by differentiating the current control strategy based on the specific rotation direction and position. When the steering wheel rotates from the end toward the center, the control unit increases current to maintain responsiveness. When the steering wheel approaches the end position, the control unit reduces current to prevent mechanical contact. This localized differentiation of control behavior resolves the contradiction by applying appropriate current levels to specific operational conditions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system implements parameter changes by dynamically modifying the current parameter supplied to the motor based on the detected steering wheel state. The control unit changes the current magnitude according to the rotation direction and position - increasing current when rotating from the end toward the center to maintain speed, and reducing current when approaching the end position to prevent mechanical contact. This parameter adjustment resolves the contradiction by optimizing motor output for different operational contexts.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Prevents the catching feeling by increasing the torque of the steering wheel when rotated from the ends to the center, ensuring a smooth and comfortable steering experience.

Implementation Method 1

a motor for generating an auxiliary power applied to the steering wheel

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 2

a torque sensor for detecting a torque applied to a steering wheel by a driver and outputting an electrical signal proportional to the detected torque

Methodology Applied

Scientific EffectTorque detection:

Implementation Method 3

a steering sensor for outputting an electrical signal proportional to a rotation angle of the steering wheel

Methodology Applied

Scientific EffectPosition detection:

Data Source

PatentUS9031744B2Electric power steering apparatus and method of controlling the same

Publication Date: 2015.05.12 HL MANDO CORP

AI summary

Disclosed are an electric power steering apparatus which controls a current supplied to a motor to adjust a torque of a steering wheel, thereby solving a catching feeling generated when the steering wheel is rotated from opposite ends to a center, and a method of controlling the same.