Configurable Inductive Probe Coils for Accurate CMM Position Sensing
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Solution Overview
Problem
Inductive sensing configurations in coordinate measuring machines (CMMs) face issues such as signal non-linearities, position offsets, signal drift due to environmental factors, and signal noise, which affect the precision of probe tip deflection measurements.
Innovation Solution
A measuring probe with a stylus suspension portion, stylus position detection portion, and signal processing circuitry is developed, utilizing a field generating coil and sensing coils to generate and detect magnetic flux, with configurable coil connections for improved signal processing and control, enhancing positional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inductive sensing configurations are used for position detection, then measurement capability is provided, but signal non-linearities and position offsets occur
Solution Approach 1:
The patent applies parameter changes by utilizing the non-linear relationship between disruptor position and induced voltage as a feature rather than a defect. By measuring the frequency of the oscillating voltage signal and mapping it to position through calibration, the system transforms the non-linear physical relationship into a usable measurement parameter that maintains accuracy while accommodating the inherent non-linearity of inductive sensing.
Solution Approach 2:
The patent implements feedback through calibration procedures that establish the relationship between disruptor position and induced voltage frequency. The system uses reference measurements at known positions to create a mapping function, then applies this feedback to correct and linearize the position readings across the full measurement range, eliminating position offsets and non-linearities.
2Measurement precision
If inductive sensing is used to detect small probe tip deflections, then measurement sensitivity is improved, but signal drift due to environmental effects increases
Solution Approach 1:
The patent employs periodic action by using oscillating drive signals at specific frequencies (e.g., 6.77 kHz, 13.54 kHz, or 20.31 kHz) to excite the inductive sensing system. This periodic excitation creates corresponding oscillating voltage signals whose frequencies are modulated by the disruptor position, enabling sensitive detection while the regular timing provides a stable reference that reduces drift from environmental effects.
Solution Approach 2:
The patent applies preliminary action through pre-calibration procedures that establish the relationship between disruptor position and signal frequency before actual measurements. The system performs reference measurements at known positions to create a calibration map, which is then used to correct subsequent measurements, thereby compensating for environmental drift and maintaining reliability.
3Measurement precision
If inductive position detectors are used in CMM probes, then position sensing capability is provided, but signal noise and assembly errors affect measurement accuracy
Solution Approach 1:
The patent applies dynamics by using a movable disruptor element that can be precisely positioned within the coil assembly. The disruptor's position is dynamically adjusted to create the desired magnetic field modulation, and its movement is coupled to the stylus mechanism to translate probe tip deflections into measurable frequency variations, thereby maintaining accuracy despite assembly tolerances.
Solution Approach 2:
The patent uses feedback through calibration procedures that measure the actual relationship between disruptor position and induced voltage at reference points. This empirical data is used to create correction functions that compensate for assembly errors and reduce signal noise, improving measurement accuracy without requiring perfect mechanical alignment.
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 enhanced precision in measuring probe tip deflections by addressing signal non-linearities and environmental drift, improving the signal-to-noise ratio and amplification for accurate position sensing.
Implementation Method 1
The field generating coil configuration is configured to generate a changing magnetic flux generally along the axial direction in the disruptor motion volume in response to a coil drive signal
Implementation Method 2
The sensing coil configuration comprises a plurality of sensing coils... coil signals indicate the disruptor and/or stylus position
Data Source
AI summary
A measuring probe for a coordinate measuring machine is provided. The measuring probe includes a stylus position detection portion with a sensing coil configuration comprising a plurality of sensing coils. Different couplable coil portions (e.g., which each at least partially surround a central axis) are provided that may be connected (e.g., individually and/or in series as part of an axial, rotary or normalization sensing coil of the plurality of sensing coils) as part of different stylus position detection configurations. For example, a first couplable coil portion may be connected to provide signals as received by signal processing and control circuitry in a first stylus position detection configuration, and may not be connected to provide signals in a second stylus position detection configuration. A second couplable coil portion may be connected to provide signals received by the signal processing and control circuitry in at least a second stylus position detection configuration.