Stepper Motor Hydraulic Steering Angle Estimation

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Solution Overview

Problem

Off-road vehicles require costly calibration and customization of wheel angle sensors for different models, leading to increased manufacturing and engineering expenses.

Innovation Solution

A vehicle guidance system that uses a hydraulic steering cylinder, stepper motor, and position encoder to estimate steering angles, eliminating the need for wheel angle sensors by controlling hydraulic fluid flow and utilizing a location-determining receiver for position data, thereby simplifying the system and reducing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If wheel angle sensors are used to detect steering angles, then measurement precision is improved, but device complexity and manufacturing costs increase due to calibration and customization requirements

Engineering Contradiction:

Improvesteering angle measurementVSAvoidsensor calibration and customization

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical wheel angle sensor system with an electro-hydraulic control system. A stepper motor controls a hydraulic steering valve to actuate the steering cylinder, and the steering angle is estimated based on the controlled displacement of the hydraulic piston. This substitution eliminates the need for mechanical angle sensors and their associated calibration procedures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a hydraulic steering cylinder as an intermediary between the control system and the steerable wheel. The cylinder's piston displacement, controlled by the hydraulic valve, serves as an intermediate measurement that can be precisely controlled and measured, replacing the direct angle measurement approach.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If wheel angle sensors with mounting adaptors are installed on multiple vehicle models, then adaptability is improved, but manufacturing costs increase due to customized hardware provisions

Engineering Contradiction:

Improvevehicle model compatibilityVSAvoidmanufacturing and engineering costs

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent creates a universal steering control system where the stepper motor, hydraulic valve, and cylinder assembly can be standardized across multiple vehicle models. The electro-hydraulic actuation mechanism serves multiple functions: it provides precise steering control, enables angle estimation through piston displacement measurement, and eliminates the need for model-specific sensor mounting hardware.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent extracts the angle sensing function from the mechanical domain and relocates it to the hydraulic control domain. By measuring piston displacement within the hydraulic cylinder rather than directly measuring wheel angle, the system removes the need for customized mounting adaptors and hardware provisions for different vehicle models.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If position encoder is added to measure motor shaft movement, then steering angle estimation accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvesteering angle estimationVSAvoidsystem components

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the hydraulic steering cylinder serve dual purposes: it provides the steering actuation force and simultaneously serves as the measurement device through its piston displacement. The position encoder on the motor shaft, combined with the known mechanical advantage of the hydraulic system, allows the cylinder to 'self-report' the steering angle through its own displacement measurement.

Inventive Principle:

Principle #25Self-service

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

This solution reduces the need for wheel angle sensors, simplifies installation, and lowers manufacturing costs by using a stepper motor and position encoder to estimate steering angles, facilitating efficient retrofitting and minimizing parts complexity.

Implementation Method 1

A hydraulic steering valve is adapted to control a flow of hydraulic fluid to the hydraulic steering cylinder

Methodology Applied

Scientific EffectHydraulic fluid flow control: Hydraulic Press

Implementation Method 2

A position encoder is associated with the stepper motor to measure the movement of the motor shaft

Methodology Applied

Scientific EffectPosition encoding:

Data Source

PatentUS9834248B2Vehicle guidance system with a stepper motor

Publication Date: 2017.12.05 DEERE & CO

AI summary

A vehicle guidance system comprises a hydraulic steering cylinder for controlling a steering angle of a steerable wheel of a vehicle. A hydraulic steering valve is adapted to control a flow of hydraulic fluid to the hydraulic steering cylinder. A stepper motor is adapted to move or modulate a shaft coupled to the hydraulic steering valve in accordance with a control signal or control data message from a vehicle guidance controller. A position encoder of the stepper motor can measure the movement of the shaft. A steering angle estimator can estimate the steering angle based on measurements of the position encoder. A location-determining receiver provides position data and heading data. A vehicle guidance controller provides the control signal or control data message based on the estimated steering angle, position data and heading data.