Inductive Stylus Position Detection with Disruptor and Coil Segmentation
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Solution Overview
Problem
Existing inductive sensing technologies used in coordinate measuring machines (CMMs) face challenges such as signal non-linearities, position errors due to assembly and alignment issues, and environmental effects like temperature changes, leading to inaccuracies and high costs, particularly due to large and expensive motion mechanisms and displacement detectors.
Innovation Solution
A scanning probe with a stylus position detection system utilizing a receiver coil portion and a disruptor configuration, featuring N top and bottom rotary sensing coils and axial sensing coils, which generates signals that are less susceptible to cross-coupling errors, allowing for accurate three-dimensional position determination through inductive sensing principles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If precision LVDTs or known inductive type sensors are used to measure displacements in mechanical contact probes, then measurement accuracy is improved, but device size and cost increase significantly
Solution Approach 1:
The patent replaces traditional mechanical displacement detectors (LVDTs) with an inductive sensing system using coils and a conductive target. This substitution eliminates the need for complex mechanical measurement mechanisms while achieving high precision displacement detection through electromagnetic induction, directly resolving the contradiction between measurement accuracy and device complexity.
Solution Approach 2:
The patent changes the sensing parameter from mechanical contact (LVDT) to inductive coupling (coils and conductive target). By using changes in inductive coupling strength as the disruptor element moves, the system achieves precise measurement without requiring large or complex mechanical sensors, thus resolving the size and complexity issue while maintaining high accuracy.
2Device complexity
If traditional inductive sensor configurations are used, then device simplicity is maintained, but measurement accuracy and reliability deteriorate due to cross-coupling errors and environmental susceptibility
Solution Approach 1:
The patent segments the sensing function into multiple independent coils (first and second coils) positioned at different locations. Each coil provides independent measurement data, and the system processes these segmented signals to eliminate cross-coupling errors and compensate for environmental effects, thereby improving accuracy while maintaining configuration simplicity.
Solution Approach 2:
The patent implements a feedback mechanism where the system continuously monitors signals from multiple coils and uses signal processing to compensate for errors. The controller processes the inductive coupling signals and applies corrections for cross-coupling and environmental effects, maintaining high accuracy without increasing physical complexity.
3Measurement precision
If conventional displacement detectors are used in CMM probes, then measurement capability is achieved, but system cost and susceptibility to environmental effects increase
Solution Approach 1:
The patent replaces mechanical displacement detectors with an inductive sensing system that uses electromagnetic fields rather than mechanical contact. This substitution reduces susceptibility to environmental effects such as temperature changes and mechanical wear, while also reducing system cost by eliminating complex mechanical components.
Solution Approach 2:
The patent introduces a conductive target (disruptor element) as an intermediary between the coils and the measured object. This intermediary enables non-contact measurement through inductive coupling, isolating the sensing system from environmental effects and reducing direct exposure to harmful factors while maintaining measurement capability.
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 proposed solution provides robust and accurate three-dimensional position indications, reducing signal errors and environmental susceptibility, while being more cost-effective and compact compared to traditional systems.
Implementation Method 1
The stylus position detection portion is based on inductive sensing principles, and includes a receiver coil portion, a disruptor configuration, and field generating coil configuration
Data Source
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AI summary
An inductive position detector (IPD) for stylus position measurement in a scanning probe comprises two substrates located along a central axis in the probe with a motion volume therebetween, each including N rotary sensing coils (RSCs) and respective axial sensing coil configurations (ASCC). A stylus-coupled conductive disruptor moves along Z (axial) and X-Y (rotary) directions in the motion volume. A generating coil (GC) generates a changing magnetic flux encompassing the disruptor and coils, and coil signals indicate the disruptor and/or stylus position. Axial projection of the disruptor defines axial sensing overlap area (ASOA) with the ASCC, and rotary sensing overlap areas (RSOAs) with respective RSCs. The IPD is configured such that the ASOA is independent of disruptor position, and N complementary pairs (CPs) of RSCs are provided, wherein the magnitude of the change in the RSOA in the two coils of a CP is the same for any disruptor displacement.