Power Steering Reference Position Determination

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Solution Overview

Problem

Existing power steering systems face inaccuracies in determining the absolute position of steering components due to thermal drifts, mechanical elasticity, and non-reproducible implementation conditions, leading to errors in defining the reference position.

Innovation Solution

A method that generates index pulses in both clockwise and counterclockwise directions to calculate a reference position by averaging edge positions, reducing errors and ensuring high accuracy and reliability in determining the absolute origin of the steering reference frame.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single index pulse is used to define the reference position, then the determination process is simple, but measurement precision deteriorates due to thermal drifts and mechanical elasticity

Engineering Contradiction:

Improvedetermination process complexityVSAvoidreference position accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent divides a single index pulse into multiple measurable components: rising edge position, falling edge position, and intermediate positions. By segmenting the pulse and measuring multiple points, the system achieves higher precision in determining the reference position while compensating for thermal drifts and mechanical elasticity effects.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary measurements of the index pulse characteristics (rising edge, falling edge, and intermediate positions) before finalizing the reference position determination. These preliminary actions allow the system to calculate compensation values for thermal drifts and mechanical elasticity, improving measurement precision before the actual reference position is established.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If factory calibration is performed under ideal conditions, then initial accuracy is high, but reliability deteriorates when implementation conditions differ from calibration conditions

Engineering Contradiction:

Improveinitial calibration accuracyVSAvoidreference position consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the approach from fixed calibration parameters to dynamic parameter adjustment. By continuously measuring the index pulse characteristics and calculating compensation values based on actual operating conditions, the system adapts to varying temperatures and mechanical states, maintaining reliability despite differences from calibration conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements a feedback mechanism where the measured positions of rising edges, falling edges, and intermediate points are continuously monitored. These measurements provide feedback that allows the system to calculate and apply compensation values, ensuring that the reference position remains accurate and reliable under varying operational conditions.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If the reference position is updated frequently, then accuracy is maintained, but loss of time increases due to repeated measurements

Engineering Contradiction:

Improvereference position accuracyVSAvoidcalibration time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies partial action by measuring only the critical points of the index pulse (rising edge, falling edge, and selected intermediate positions) rather than continuously monitoring the entire pulse waveform. This selective measurement approach maintains accuracy while reducing the time required for reference position updates.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent performs preliminary identification of key pulse characteristics during normal operation, storing these measurements for later use in reference position determination. This preliminary action allows the system to quickly update the reference position without performing complete measurements each time, reducing time loss while maintaining accuracy.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9937951B2Determination of an angular reference position of a power steering system from rising and falling edges of an index signal

Publication Date: 2018.04.10 JTEKT EUROPE SAS

AI summary

A reference position in a power steering system is defined by acquiring a first edge position corresponding to a first edge of a first index pulse generated when a movable steering member passes an indexed position in a first movement direction; acquiring a second edge position corresponding to a second edge of a second index pulse generated when the movable steering member passes the same indexed position in a second movement position opposite the first movement direction; and calculating the reference position from the first edge position and the second edge position.