Steering Controller Motor Absolute Angle Calibration

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Solution Overview

Problem

Existing steering controllers in electric power steering systems and steer-by-wire systems face challenges in maintaining an accurate motor absolute angle correspondence with the steered angle, especially when power supply is interrupted, leading to loss of correspondence between the motor absolute angle and the steered angle.

Innovation Solution

A steering controller that includes an end position determination unit, a motor absolute angle detection unit, and an end position-corresponding motor angle setting unit, which determines the steering axle's end position and sets the motor absolute angle accordingly, allowing for accurate motor absolute angle detection even after power interruption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electric power is continuously supplied from the on-board battery to the controller to detect motor rotation and maintain correspondence between steered angle and motor absolute angle, then the correspondence relationship between steered angle and motor absolute angle is maintained, but power consumption increases and reliability decreases when battery replacement occurs

Engineering Contradiction:

Improvecorrespondence relationship maintenanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The controller stores learned correspondence relationships between steered angle and motor absolute angle in a non-volatile memory before power interruption occurs. This preliminary action ensures that even when power is interrupted for battery replacement, the correspondence relationship can be restored without requiring continuous power supply during the interruption period.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A non-volatile memory component acts as an intermediary between the powered controller and the correspondence relationship data. This intermediary preserves the learned correspondence relationship during power interruptions, allowing the system to maintain accuracy without continuous power supply to the controller.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the motor absolute angle is detected in correspondence with the steered angle using continuous power supply, then accurate angle detection is achieved, but the system becomes vulnerable to data loss during battery replacement

Engineering Contradiction:

Improvemotor absolute angle detection accuracyVSAvoiddata persistence during power interruption

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The controller performs learned correspondence relationship storage before power interruption occurs. By preliminarily capturing and storing the relationship between steered angle and motor absolute angle in non-volatile memory, the system ensures that measurement precision is maintained even when power is interrupted for battery replacement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Non-volatile memory serves as an intermediary that preserves measurement data and correspondence relationships during power interruptions. This intermediary ensures that motor absolute angle detection accuracy is maintained without requiring continuous power supply during battery replacement operations.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If the correspondence relationship between steered angle and motor absolute angle is lost during battery replacement, then power consumption is reduced, but accurate motor absolute angle detection cannot be maintained

Engineering Contradiction:

Improvepower consumption during battery replacementVSAvoidmotor absolute angle detection accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The controller stores the correspondence relationship in non-volatile memory before power interruption occurs. This preliminary action ensures that even when power consumption is reduced during battery replacement, the motor absolute angle detection accuracy can be restored by retrieving the stored correspondence relationship.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Non-volatile memory acts as an intermediary that preserves measurement data during low-power states. This allows the system to reduce power consumption during battery replacement while maintaining the ability to restore accurate motor absolute angle detection by reading from the intermediary storage.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10981596B2Steering controller

Publication Date: 2021.04.20 JTEKT CORP

AI summary

A control steered angle calculation unit includes: an end position determination unit that determines whether a rack shaft is located at either one of right and left rack end positions; a motor absolute angle calculation unit that detects a motor absolute angle; an end position-corresponding motor angle setting unit that, when the rack shaft is determined to be located at either one of the right and left rack end positions, sets the detected motor absolute angle as an end position-corresponding motor angle corresponding to the one of the right and left rack end positions; and a control steered angle origin setting unit that calculates an average value of right and left end position-corresponding motor angles as an offset angle, and sets an angle obtained by subtracting the offset angle from the detected motor absolute angle as an origin of the control steered angle represented by the motor ab solute angle.