Inductive Stylus Position Detection via Magnetic Flux Disruption
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Solution Overview
Problem
Existing inductive sensing configurations for coordinate measurement 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 increased costs.
Innovation Solution
A scanning probe with a stylus suspension portion and position detection system using a coil board configuration with field generating coils and a cylindrical disruptor element, which generates changing magnetic flux for accurate axial and rotary position sensing, reducing signal errors and cross-coupling errors through advanced signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LVDTs or known inductive type sensors are used to measure displacements in mechanical contact probes, then measurement accuracy is improved, but device size increases and cost increases
Solution Approach 1:
The patent replaces traditional mechanical displacement measurement mechanisms (LVDTs) with an inductive sensing system that uses electromagnetic fields. The inductive sensor detects position through changes in magnetic flux caused by disruptor element movement, eliminating the need for large mechanical components while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the sensing parameter from direct mechanical displacement measurement to inductive coupling measurement. By measuring changes in magnetic flux and inductance rather than direct mechanical position, the system achieves accurate displacement measurement with a more compact sensor design.
2Measurement precision
If LVDTs or known inductive type sensors are used to measure displacements in mechanical contact probes, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive mechanical displacement sensors (LVDTs) with an inductive sensing system that uses electromagnetic fields and disruptor elements. This substitution reduces manufacturing costs while maintaining measurement accuracy, as the inductive components are simpler and more economical to produce.
Solution Approach 2:
The patent uses a disruptor element that creates a magnetic field pattern similar to what would be produced by a larger sensor. By copying the essential sensing function through electromagnetic induction rather than direct mechanical measurement, the system achieves accurate results with lower-cost components.
3Device complexity
If traditional inductive sensor configurations are used, then device simplicity is maintained, but cross-coupling errors and signal non-linearities increase
Solution Approach 1:
The patent segments the sensing function into multiple independent components: a field generating coil, multiple disruptor elements positioned at different locations, and separate detection coils for each disruptor. This segmentation allows each component to be optimized independently and reduces cross-coupling errors between sensing axes.
Solution Approach 2:
The patent introduces disruptor elements as intermediary components that mediate between the field generating coil and the detection coils. These disruptors create localized magnetic field disturbances that can be detected independently, reducing direct coupling between sensing channels and improving signal accuracy.
4Reliability
If known inductive sensing systems are used in CMM probes, then environmental robustness is improved, but signal drift due to environmental effects increases
Solution Approach 1:
The patent incorporates feedback mechanisms where the detection coils continuously monitor the magnetic field disturbances caused by disruptor elements. This feedback allows the system to compensate for environmental effects such as temperature changes by detecting and correcting for shifts in the magnetic field baseline, thereby maintaining signal stability.
Solution Approach 2:
The inductive sensing system is self-compensating for environmental effects. The disruptor elements and detection coils form a closed electromagnetic system that automatically adjusts to temperature and environmental changes, eliminating the need for external compensation mechanisms while maintaining measurement precision.
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 solution provides robust and accurate three-dimensional position indications, enhancing the precision and reliability of CMMs while reducing costs by minimizing errors and environmental susceptibility.
Implementation Method 1
A field generating coil configuration (e.g., a single planar coil) is provided that generates a changing magnetic flux, generally along the axial direction, in the disruptor motion volume in response to a coil drive signal.
Implementation Method 2
A cylindrical disruptor element is provided that moves in the disruptor motion volume relative to an undeflected position. The disruptor element provides a disruptor area that is less than an area of the planar coil when viewed along the axial direction.
Data Source
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AI summary
An inductive position detector for stylus position measurement in a scanning probe comprises a coil board configuration located along a central axis in the probe. The coil board configuration includes a field generating coil configuration that surrounds a hole in the coil board configuration, a top axial sensing coil configuration and a bottom axial sensing coil configuration, and N top rotary sensing coils and N bottom rotary sensing coils. A stylus-coupled disruptor configuration includes a cylindrical disruptor element that is configured to move and fit within the hole of the coil board configuration, and moves along Z (axial) and X-Y (rotary) directions in a motion volume. The field generating coil configuration generates a changing magnetic flux (e.g., encompassing all or at least part of the cylindrical disruptor element), and coil signals indicate the cylindrical disruptor element and/or stylus positions.