Agricultural Steering System Zero Position Drift

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Solution Overview

Problem

Conventional hydrostatic steering systems in agricultural vehicles experience hydraulic leaks, causing the zero position of the steering signal transmitter to shift relative to the wheel steering angle, which is not perceptible to operators, leading to operational safety concerns.

Innovation Solution

A steering system with a control unit that tracks and adjusts the zero position of the steering signal transmitter using a hydraulic main steering valve, incorporating sensors to determine wheel and steering positions, and a slow tracking process to maintain a constant zero position, thereby counteracting hydraulic leaks and ensuring operator safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional hydrostatic steering system with an orbitrol is used, then the steering system is simple and reliable, but hydraulic leaks cause the zero position of the steering signal transmitter to drift relative to the wheel steering angle

Engineering Contradiction:
Improvezero position stabilityVSAvoidsteering system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The control unit continuously monitors the actual wheel steering angle and compares it with the desired zero position. When a deviation is detected (caused by hydraulic leaks), the control unit automatically adjusts the main steering valve to correct the zero position of the steering signal transmitter, creating a closed-loop feedback system that maintains accuracy despite hydraulic imperfections.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The steering system performs self-correction by automatically detecting zero position drift and adjusting itself through the control unit and main steering valve. This self-service mechanism eliminates the need for manual recalibration and maintains reliable operation without requiring additional external intervention or complex mechanical components.

Inventive Principle:
Principle #25Self-service

2Reliability

If the zero position is adjusted quickly to counteract drift, then the zero position stability is improved, but the vehicle operator can notice the adjustment process which may cause operational issues

Engineering Contradiction:
Improvezero position stabilityVSAvoidoperator control stability
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The control unit performs zero position adjustments in periodic, incremental steps rather than continuously or all at once. This periodic adjustment approach allows the system to gradually correct drift while keeping each individual adjustment step small enough to remain imperceptible to the operator, maintaining both stability and operational smoothness.

Inventive Principle:
Principle #19Periodic action

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

The solution maintains a constant zero position of the steering signal transmitter, enhancing operational safety and ergonomics by ensuring the steering wheel remains in a consistent position, allowing for improved control and reduced risk of mechanical failures, such as broken cable connections.

Implementation Method 1

a hydraulic main steering valve (9) for pressurizing the at least one steering cylinder (2a, 2b)

Methodology Applied
Scientific EffectHydraulic pressure: Hydraulic Press

Implementation Method 2

due to hydraulic leaks, the zero position of the steering signal sensor can drift relative to the zero position of the wheel lock angle

Methodology Applied
Scientific EffectHydraulic leakage:

Data Source

PatentEP3862249B1Steering system for an agricultural vehicle
Publication Date: 2024.01.10 CLAAS SELBSTFAHRENDE ERNTEMASCHINEN GMBH
  • EP3862249B1 patent drawingFigure 1
  • EP3862249B1 patent drawingFigure 2

AI summary

The present invention relates to a steering system for an agricultural vehicle (1) comprising at least one steering cylinder (2a, 2b) for changing a wheel steering angle (3) of the agricultural vehicle (1), a hydraulic main steering valve (9) for pressurizing the at least one steering cylinder (2a, 2b), a steering signal transmitter (10) for actuating the main steering valve (9), and a control unit (14) for adjusting an adjustment characteristic between the steering signal transmitter (10) and the at least one steering cylinder (2a, 2b), wherein the control unit (14) is configured to follow a zero position (20) of the steering signal transmitter (10) by actuating the main steering valve (9), based on a zero position (18) of the wheel steering angle (3) established when driving straight ahead.