Hydraulic Steering Neutral Position Calibration

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Solution Overview

Problem

Fully hydraulic steering systems lack a mechanical connection between the steering command device and the steered wheels, making it impossible to manually move the wheels to determine their neutral position, which is crucial for reliable steering control.

Innovation Solution

The method involves moving the steered wheels to a first and second end position using the hydraulic steering motor, and then determining the neutral position by analyzing the signals from the wheel angle sensor, which provides output signals based on measured angles, allowing for the calculation of a neutral signal between the first and second signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fully hydraulic steering system is used to eliminate mechanical connection between steering command device and steered wheels, then reliability of steering control is improved, but the ability to manually determine neutral position is lost

Engineering Contradiction:

Improvereliability of steering controlVSAvoidability to manually determine neutral position

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system uses the wheel angle sensor and hydraulic motor to automatically determine the neutral position through electronic calibration procedures, eliminating the need for manual mechanical determination while maintaining calibration accuracy

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces manual mechanical determination of neutral position with an electronic sensing and calculation system that uses the wheel angle sensor to detect end positions and computes the neutral position electronically, substituting mechanical operations with electronic control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Extent of automation

If the neutral position is determined using wheel angle sensor signals at end positions, then manual intervention is eliminated, but the non-linear relationship between sensor signal and wheel angle complicates the determination

Engineering Contradiction:

Improveautomatic calibration capabilityVSAvoidcomplexity of signal processing

Core Design Contradiction:

Extent of automationVSDevice complexity

Solution Approach 1:

The patent measures wheel angles at the extreme end positions only, rather than attempting to measure at all possible angles. This partial measurement approach simplifies the calibration process by focusing only on the boundary conditions needed to establish the neutral position, avoiding the complexity of characterizing the entire non-linear range

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentEP4163187B1Method for calibrating a fully hydraulic steering system

Publication Date: 2025.04.30 DANFOSS POWER SOLUTIONS APS

Figure 1
Figure 2a~2b

AI summary

A method for calibrating a fully hydraulic steering system (1) of a vehicle having steered wheels and a hydraulic steering motor (2) is described, in which method the steered wheels are moved by the steering motor (2) in one direction until they reach a first end position and are then moved in the opposite direction until they reach a second end position, wherein the hydraulic steering system (1) comprises a wheel angle sensor (15, 16) determining the wheel angle of the steered wheels. Such a calibration should be performed in a simple way. To this end the wheel angle sensor (15, 16) determines a first signal in the first end position and a second signal in the second end position wherein a neutral position of the steering motor is determined by determining a neutral signal between the first signal and the second signal, wherein the difference between the neutral signal and the first signal is substantially equal to the difference between the neutral signal and the second signal.