Inductive Position Sensor with Saw-Tooth Magnetic Target
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Solution Overview
Problem
Existing optical sensing systems for fluid-actuated cylinders face challenges such as degradation of indicia marks in hostile environments and limited resolution due to the need for specialized fabrication and sealing, as well as limitations in quadrature measuring techniques.
Innovation Solution
An inductive sensor system using a moveable body with a magnetic field-altering profile, such as conical sections, that interacts with Hall-effect sensors to provide a saw-tooth or other profiled magnetic field variations, allowing for higher resolution position sensing without the need for precise indicia marks or complex sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical sensing systems with indicia marks are used for position sensing, then position measurement capability is provided, but the indicia marks are prone to degradation in hostile environments and require specialized fabrication and sealing
Solution Approach 1:
The patent replaces the optical sensing system with an inductive sensing system that uses magnetic fields instead of light. The inductive sensor head reads position information from a ferrous target with raised features through magnetic field interaction, eliminating the need for optical indicia marks and their associated sealing requirements. This substitution resolves the contradiction by improving reliability in hostile environments while reducing device complexity.
Solution Approach 2:
The patent changes the sensing parameter from optical reflection to magnetic field induction. By using a ferrous target that alters the magnetic field based on its position relative to the inductive sensor, the system achieves position sensing without vulnerable optical marks. This parameter change eliminates degradation issues and simplifies the sealing arrangement.
2Measurement precision
If quadrature measuring techniques are used with optical or inductive sensors, then position measurement is achieved, but resolution is limited by the distance between indicia marks or target increments
Solution Approach 1:
The patent uses a conical profile on the ferrous target instead of flat square increments. The conical surfaces create continuous magnetic field gradients as the target moves relative to the inductive sensor, enabling higher resolution measurements. The curved conical geometry allows the sensor to detect position changes over a continuous range rather than discrete increments, effectively reducing the functional distance between measurement points.
Solution Approach 2:
The patent transitions from two-dimensional planar increments to three-dimensional conical surfaces. The conical profile adds a vertical dimension to the target features, creating magnetic field variations that provide continuous position information. This dimensional change enables higher resolution sensing by exploiting the gradient of magnetic field strength along the conical surface rather than relying on discrete planar transitions.
3Measurement precision
If optical indicia marks are used on piston rods, then position sensing capability is provided, but the marks require specialized fabrication techniques and expose the sensing head to environmental degradation
Solution Approach 1:
The patent replaces optical indicia fabrication with magnetic target fabrication. Instead of laser-marking or applying optical codes to the piston rod, the system uses a ferrous target with raised features that can be manufactured using conventional machining techniques. The inductive sensor reads the magnetic field variations caused by these mechanically fabricated features, eliminating the need for specialized optical mark fabrication.
Solution Approach 2:
The ferrous target with raised features serves dual purposes: it provides the magnetic signature for position sensing while also functioning as the piston rod's structural component. The target's physical profile directly creates the magnetic field pattern needed for sensing, eliminating the need for separate indicia application processes and simplifying manufacturing.
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 offers robust, high-resolution linear position sensing resistant to environmental degradation and manufacturing complexity, with the ability to maintain accuracy over long distances and in harsh industrial conditions.
Implementation Method 1
The sensor uses one or more Hall-effect sensors, and the body moves in dependence with an object to be sensed. As the body moves relative to the Hall-effect sensors, the signal output of the sensor alters in accordance with the profile of the body.
Implementation Method 2
An inductive sensor head and a body moveable relative to the sensor. The body is made of a material capable of altering a magnetic field
Data Source
AI summary
A field-altering device for an inductive sensor has an elongated body with a substantially saw-tooth profile. The body is made of steel or other type ferrous material. With use in a Hall-effect sensor, the body moves relative to the sensor causing the field to vary periodically with time. The sensor generates an electrical signal in dependence on the field variations, the electrical signal having a saw-tooth pattern.