Electromagnet Position Sensor for Hydraulic Piston Disturbance Rejection
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Solution Overview
Problem
Existing position measurement systems face limitations in measuring the position of isolated moving objects due to the need for mechanical connections, harsh environment exposure, size constraints, and susceptibility to ferromagnetic disturbances, particularly in applications like hydraulic pistons where clear line of sight and sub-mm accuracy are required.
Innovation Solution
An electromagnet-based position sensing system that generates an alternating magnetic field, using magnetic sensors to measure field intensity and estimate object position, with adaptive estimation algorithms to reject disturbances from ferromagnetic objects, allowing for non-intrusive, real-time measurement without the need for permanent magnets or mechanical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical connection sensors (potentiometers, LVDTs) are used for position measurement, then measurement precision can be achieved, but the device complexity increases and reliability decreases due to mechanical connections and exposure to harsh environments
Solution Approach 1:
The patent replaces mechanical connection sensors with a magnetic field-based sensing system. An array of magnetic sensors detects the position of a magnet attached to the moving object through non-contact measurement, eliminating mechanical connections and improving reliability in harsh environments while maintaining measurement precision
2Ease of operation
If laser and LED sensors are used for position measurement, then no mechanical connection is required, but the device complexity increases and measurement precision decreases when clear line of sight is blocked
Solution Approach 1:
The patent uses magnetic field-based non-contact sensing to replace optical sensors. The magnetic field penetrates isolation barriers (such as engine blocks or hydraulic cylinder walls) that block optical lines of sight, enabling accurate position measurement without requiring clear visibility while maintaining ease of non-contact operation
3Ease of operation
If magnetic field-based position measurement systems are used, then no mechanical connection is required, but measurement precision decreases due to susceptibility to ferromagnetic disturbances
Solution Approach 1:
The patent applies preliminary calibration to characterize and compensate for ferromagnetic disturbances in the measurement environment. By pre-measuring and storing disturbance patterns, the system can subtract these known errors from subsequent measurements, maintaining precision despite the presence of ferromagnetic objects
Solution Approach 2:
The patent uses multiple magnetic sensors arranged in an array to detect field variations caused by ferromagnetic disturbances. The system processes signals from multiple sensors to distinguish between position-induced field changes and disturbance-induced field changes, enabling compensation and maintaining measurement precision through feedback processing
4Ease of operation
If permanent magnet-based position sensors are used, then no mechanical connection is required, but device complexity increases due to susceptibility to ferromagnetic object disturbances
Solution Approach 1:
The patent performs preliminary characterization of the measurement environment to identify and model ferromagnetic disturbances. This pre-calibration process creates a reference map of disturbance patterns that simplifies subsequent position measurements by allowing direct compensation of known errors, reducing the complexity of real-time signal processing
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 system provides robust and accurate position measurement, immune to ferromagnetic disturbances, with reduced size and power requirements, enabling its use in harsh environments and isolated applications like hydraulic pistons, while maintaining high accuracy and linearity.
Implementation Method 1
an electromagnet to generate an alternating magnetic field
Implementation Method 2
at least one magnetic sensor for measuring an intensity of a magnetic field
Data Source
AI summary
A position sensing system for measuring a position of a linearly moving object includes a high magnetic permeability material positioned on the moving object, an electromagnet configured to generate an alternating magnetic field, and at least one magnetic sensor configured to measure an intensity of a first magnetic field that is based on the alternating magnetic field. A controller is configured to estimate a linear position of the moving object based on the measured intensity of the first magnetic field.