Hydraulic Cylinder Piston Rod Position Detection Using Pixel Matching

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Solution Overview

Problem

Existing methods for detecting the position of a piston rod in hydraulic cylinders suffer from low accuracy and high costs, with magnetostrictive displacement sensors having limited range and wire rope sensors being difficult to install and maintain, and prone to slippage and zero-point drift.

Innovation Solution

A method and device that utilize a pixel database to compare pixel information from a target image with pre-stored pixel information of a piston rod, allowing for accurate determination of the piston rod's position by correlating pixel information with displacement data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a magnetostrictive displacement sensor is used to detect the position of the piston rod, then the detection method is simple, but the detection range is narrow and the detection accuracy is limited

Engineering Contradiction:

Improvedetection method simplicityVSAvoiddetection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces the magnetostrictive displacement sensor with a vision-based detection system using a camera to capture images of the piston rod. The camera system processes images to determine piston rod position, eliminating the need for magnetic field-based measurement and achieving higher accuracy through image analysis algorithms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates a digital model (pixel database) that stores the correspondence between piston rod positions and their visual appearances. By comparing captured images against this pre-established pixel database, the system accurately determines position without physical contact, achieving both high accuracy and extended detection range.

Inventive Principle:

Principle #26Copying

2Measurement precision

If a built-in wire rope displacement sensor is used to detect the position of the piston rod, then the detection range can be extended, but the installation and maintenance become troublesome and the cost increases with stroke length

Engineering Contradiction:

Improvedetection rangeVSAvoidinstallation and maintenance complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical wire rope displacement sensor with an optical vision system. The camera captures images of the piston rod, and image processing algorithms determine position. This eliminates the mechanical wire rope, its reel mechanism, and associated installation/maintenance complexity while providing contactless measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the measurement function from the mechanical sensor system and implements it through pure optical means. By separating the position detection function from the mechanical drive system, the patent eliminates the wire rope and reel assembly, reducing device complexity and maintenance requirements.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If a built-in wire rope displacement sensor is used to detect the position of the piston rod, then the detection range can be extended, but problems such as slippage and zero-point drift occur which affect stability

Engineering Contradiction:

Improvedetection rangeVSAvoidposition detection stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical wire rope sensor with an optical vision system that captures images of the piston rod. This contactless measurement method eliminates mechanical slippage and zero-point drift issues inherent in wire rope systems, providing stable and reliable position detection throughout the full stroke range.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates a digital pixel database that stores the precise visual correspondence between piston rod positions and image characteristics. By continuously comparing captured images against this database, the system maintains stable and accurate position detection without the mechanical degradation and drift problems of wire rope sensors.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS12264692B2Method and device for detecting position of piston rod, hydraulic cylinder and working machine

Publication Date: 2025.04.01 SANY AUTOMOBILE MFG CO LTD

AI summary

Disclosed are a method and a device for detecting a position of a piston rod, a hydraulic cylinder and a working machine. The method includes: acquiring a target image at a target position; obtaining a pixel information corresponding to the target image; comparing the pixel information with a pixel database of the piston rod, a full-stroke pixel information of the piston rod and a relationship between the full-stroke pixel information of the piston rod and a displacement of the piston rod are stored in the pixel database of the piston rod, and the full-stroke pixel information at least comprises the pixel information within a range in which the piston rod is configured to move relative to the target position; and determining a position information of the piston rod based on a comparison result.