Spherical Capacitive Plate Probing System for Deep Hole Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing probing systems face challenges in achieving high precision and deep measurement of small structures with large aspect ratios due to stylus bending, anisotropic probing characteristics, and sensitivity to material and surface finish, limiting their ability to measure complex geometries accurately.
Innovation Solution
An ultraprecision non-contact three-dimensional probing system based on a spherical capacitive plate, which includes a spherical probing head, stylus pipe, active shielding pipe, signal conducting rod, and a signal converting and processing circuit, eliminating stylus bending and contact deformation by using a capacitive sensing mechanism with equipotential driving and tri-coaxial structure to enhance dynamic performance and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a contact probe with long stylus is used to measure deep small holes, then the measurable depth is improved, but the stylus bending under probing force seriously reduces the measurement precision
Solution Approach 1:
The patent replaces the mechanical contact-based stylus probing system with a capacitive sensing system. The capacitive probe head detects position through electrical field interaction without physical contact, eliminating the mechanical stylus bending problem entirely while enabling measurement of deep small holes with both depth and precision.
Solution Approach 2:
The patent introduces an intermediary capacitive field between the probe head and the workpiece surface. This electrical field mediator enables non-contact detection, allowing the probe to sense position changes in deep holes without the mechanical interference of a physical stylus, thus resolving the bending precision issue.
2Device complexity
If a touch trigger probe is used for simple structure and low cost, then the device complexity is reduced, but the probing force causes stylus bending and pretravel errors reduce measurement precision
Solution Approach 1:
The patent replaces the mechanical touch trigger mechanism with a capacitive sensing mechanism. This substitution eliminates the need for physical contact and trigger circuits, reducing device complexity while simultaneously eliminating stylus bending and pretravel errors that compromised measurement precision.
Solution Approach 2:
The patent extracts and removes the problematic mechanical contact elements (stylus, trigger mechanism) from the probing system. By taking out these components that caused bending and pretravel errors, the system achieves both simplified structure and improved precision through non-contact capacitive sensing.
3Measurement precision
If a scanning probe with high sensitivity is used to reduce probing force, then the measurement precision is improved, but the structure becomes much more complicated and precision is reduced for three-dimensional measurement
Solution Approach 1:
The patent replaces complex mechanical scanning mechanisms with a simple capacitive sensing system. The capacitive probe head directly measures three-dimensional coordinates through electrical field interaction, eliminating the need for complex micro three-dimensional carriages while maintaining high precision and reducing device complexity.
Solution Approach 2:
The patent segments the probing function into independent capacitive sensing elements that can measure multiple dimensions simultaneously. This segmentation allows three-dimensional profiling without requiring complex mechanical scanning structures, achieving both simplicity and precision.
4Measurement precision
If optical probes are used for non-contact measurement, then the measurement precision is improved, but the sensing characteristics are easily influenced by material characteristics and surface finish
Solution Approach 1:
The patent replaces optical sensing with capacitive sensing. The capacitive field interacts with the workpiece through electrical field coupling, which is less sensitive to surface finish and material optical properties compared to optical methods. This substitution reduces the harmful influence of material characteristics and surface finish on 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
Enables non-contact measurement of small structures with large aspect ratios with ultrahigh resolution and dynamic performance, reducing errors from kinematic inertia and stylus deformation, and providing approximate point sensing characteristics for precise three-dimensional profiling.
Implementation Method 1
the micro gap between the probing head and the part being measured to a capacitive signal through the electric field formed between them
Implementation Method 2
through the electric field formed between them
Implementation Method 3
The stylus pipe, the active shielding pipe and the signal conducting rod altogether form a tri-coaxial structure, and the influence of parasitic capacitance and spatial electromagnetic interference on the capacitive signal can be completely eliminated
Data Source
AI summary
A non-contact three-dimensional probing system based on a spherical capacitive plate has a probe including a spherical probing head (5), a stylus pipe (6), an active shielding pipe (8), a signal conducting rod (7), an insulating element (9), a stylus holder (10) and a probe body (11). The spherical probing head (5) is mounted at one end of the insulating element (9), and it has a spherical capacitive plate over its surface. The capacitive signal coming from the spherical capacitive plate is outputted through the signal conducting rod (7). The active shielding pipe (8) is driven by the signal converting and processing circuit (13) of the probing system to maintain equipotential with the signal conducting rod (7), and so the influence of parasitic capacitance and spatial electromagnetic interference can be eliminated.