Inductive Stylus Position Detection via Disruptor Modulation
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Solution Overview
Problem
Existing inductive sensing technologies in coordinate measuring machines (CMMs) face challenges such as accuracy issues due to signal non-linearities, position errors from imperfect assembly and alignment, and environmental effects like temperature changes, and are often expensive and prone to cross-coupling errors.
Innovation Solution
A scanning probe configuration utilizing a stylus position detection system with a receiver coil portion, a disruptor configuration, and a field generating coil configuration, featuring multiple sensing coils and a disruptor element that moves within a defined motion volume, providing overlapping areas that remain constant despite stylus motion, to correct signal errors and enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional inductive sensors (LVDTs) are used for position detection, then measurement accuracy is improved, but device size and cost increase
Solution Approach 1:
The patent replaces traditional mechanical inductive sensors (LVDTs) with an electromagnetic field-based sensing system. The system uses a disruptor element that modulates the magnetic field generated by drive coils, allowing position detection through electromagnetic interactions rather than direct mechanical contact. This substitution reduces mechanical complexity while maintaining measurement precision.
Solution Approach 2:
The disruptor element serves as an intermediary between the drive coils and receive coils. It modulates the magnetic field by moving within the field generated by drive coils, creating position-dependent variations that are detected by receive coils. This intermediary approach enables indirect position measurement with reduced complexity compared to direct sensor contact.
2Measurement precision
If traditional inductive sensing is used, then position detection is achieved, but cross-coupling errors and signal non-linearities increase
Solution Approach 1:
The sensing system is segmented into multiple independent coil pairs, each responsible for detecting position along specific axes. The disruptor element's position is determined by combining signals from multiple coil pairs, which reduces cross-coupling errors between axes. Each coil pair operates semi-independently, allowing error isolation and correction.
Solution Approach 2:
The system uses feedback through the disruptor element's position-dependent modulation of the magnetic field. The receive coils detect the modulated field signals, which are processed to determine position. This feedback mechanism allows for error correction and compensation, improving signal reliability by continuously monitoring and adjusting for deviations.
3Measurement precision
If complex assembly and alignment procedures are used, then sensor accuracy is improved, but manufacturing difficulty and time increase
Solution Approach 1:
The patent employs symmetric geometric arrangements of coils and disruptor elements that create equipotential conditions for field distribution. This symmetry ensures that position detection is inherently reference-free, eliminating the need for complex alignment procedures. The geometric symmetry provides natural error compensation, making the system robust to manufacturing tolerances.
Solution Approach 2:
The system uses parameter changes in the magnetic field strength and distribution based on disruptor position, rather than relying on precise mechanical alignment. By detecting changes in field parameters (magnitude, phase, frequency) as the disruptor moves, the system achieves high precision without requiring complex assembly procedures. The field parameters naturally encode position information.
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 configuration improves the accuracy of three-dimensional position detection in CMMs by eliminating or correcting signal errors and cross-coupling issues, providing robust and highly accurate position indications with simplified signal processing.
Implementation Method 1
a field generating coil configuration... configured to generate a changing magnetic flux
Implementation Method 2
The receiver coil portion... configured to detect the changing magnetic flux and provide signal components that are indicative of the position
Data Source
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AI summary
An inductive position detector (IPD) for stylus position measurement in a scanning probe comprises a coil board configuration located along a central axis in the probe with a motion volume extending on opposite sides of the coil board configuration. The coil board configuration includes N top rotary sensing coils (RSCs) and a top axial sensing coil configuration (ASCC), and N bottom RSCs and a bottom ASCC. A pair of stylus-coupled conductive disruptors move along Z (axial) and X-Y (rotary) directions in the motion volume. A generating coil (GC) of the coil board configuration generates a changing magnetic flux (e.g., encompassing all or at least part of the disruptors), and coil signals indicate the disruptors and/or stylus positions. Areas of the conductive disruptors may be larger than an area of the generating coil in some implementations, and the conductive disruptors may each comprise a plurality of concentric conductive loops, spirals, etc.