PCB Capacitive Sensor for Rotor Position Sensing
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Solution Overview
Problem
Capacitive position and motion sensors for rotor position feedback in electrical machines are expensive, prone to manufacturing errors, delayed measurements, temperature-dependent, susceptible to noise and electromagnetic interference, and affected by mechanical runout.
Innovation Solution
A capacitive sensor implemented on a printed circuit board (PCB) with electrodes formed around a mounting hole for the rotor shaft, utilizing LC resonance, high-frequency signals, and differential amplifiers to enhance sensitivity and robustness, reducing manufacturing costs and improving system integration and noise resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive displacement sensors are used for high-resolution position measurement, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces complex mechanical capacitive sensors with a simplified PCB-based capacitive sensing system. The sensor tip is integrated directly onto the PCB board, eliminating the need for separate mechanical sensor assemblies. This substitution maintains measurement precision while significantly reducing device complexity and manufacturing cost.
Solution Approach 2:
The PCB serves multiple functions: it acts as both the circuit board for signal processing and the mounting structure for the capacitive sensor. The sensor tip is integrated into the PCB itself, allowing the board to perform both structural and sensing functions simultaneously, thereby reducing overall system complexity.
2Measurement precision
If precise capacitive sensors are implemented with sensor tips mounted around the shaft, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent merges the sensor tip, PCB substrate, and mounting structure into a single integrated unit. The capacitive sensor is fabricated directly on the PCB using standard PCB manufacturing processes, eliminating the need for separate assembly steps. This integration maintains measurement precision while dramatically improving ease of manufacture.
Solution Approach 2:
The patent employs standard PCB manufacturing techniques to create the sensor, replacing expensive custom-machined sensor components with affordable PCB-based capacitive structures. This approach uses conventional, cost-effective manufacturing processes while maintaining adequate measurement precision for the application.
3Measurement precision
If capacitive sensors are used for position feedback, then measurement precision is improved, but susceptibility to electromagnetic interference increases
Solution Approach 1:
The PCB acts as an intermediary structure that provides inherent electromagnetic shielding and noise filtering for the capacitive sensor. The grounded PCB layers and trace routing design serve as natural shields against electromagnetic interference, protecting the sensitive capacitive measurements while maintaining signal integrity.
Solution Approach 2:
The patent replaces vulnerable mechanical sensor assemblies with a PCB-integrated capacitive system that has inherent electromagnetic compatibility. The PCB's layered structure and grounding schemes provide built-in protection against EMI, eliminating the need for additional shielding components required by traditional mechanical sensors.
4Measurement precision
If sensor tips are mounted around the shaft for each measured dimension, then measurement precision is improved, but productivity decreases due to assembly complexity
Solution Approach 1:
The patent combines multiple sensor functions into a single PCB assembly. All capacitive sensor elements for different measurement dimensions are fabricated on one PCB board, eliminating the need to assemble multiple separate sensor tips around the shaft. This integration maintains multi-dimensional measurement capability while dramatically improving assembly productivity.
Solution Approach 2:
The PCB is designed with distinct, separately addressable capacitive sensing zones that can independently measure different dimensions. This segmentation allows each measurement function to be independently optimized while maintaining a unified, easily assembled structure that improves productivity compared to separate mechanical sensor assemblies.
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 an affordable, precise, and robust non-contact measurement of rotor position and motion, minimizing noise and interference while reducing manufacturing costs and improving system connectivity.
Implementation Method 1
an electrode forms a capacitor with a surface of the conducting shaft. Capacitance of the formed capacitor can be measured. Since the capacitance is responsive to the gap between the electrode and the surface of the shaft, the capacitance can be used for estimating the position of the shaft
Implementation Method 2
utilizing LC resonance, high-frequency signals, and differential amplifiers to enhance sensitivity and robustness
Data Source
Figure 1a~1b
Figure 2a~2e
Figure 3a~3c
AI summary
The present disclosure presents a method, a sensor comprising printed circuit board (PCB), and a sensor PCB for a capacitive sensor for sensing position or motion of a shaft comprising an electrically conducting part. The method and the sensor utilise the sensor PCB that comprises a mounting hole through which the conducting part of the shaft can be mounted, at least one capacitor electrode formed to the printed circuit board, wherein an electrode surface of the electrode extends parallel to a center axis of the mounting hole and faces the center axis.