Galvanically Isolated Rotating Shaft Position Encoder
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Solution Overview
Problem
Existing position sensing systems for rotating components, such as motor shafts, lack true redundancy due to pin layout issues in multi-sensor ICs, which can lead to short circuits and data verification challenges in safety-critical systems.
Innovation Solution
A system with two galvanically isolated magnetic field sensors positioned on opposite sides of a substrate, where one sensor has a layer of magnetic material to enhance field detection and a non-magnetic layer to maintain field integrity, allowing for equal magnetic field strength measurement and redundancy without additional mechanical attachments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple sensors are embedded in one integrated circuit package, then device complexity is reduced, but reliability deteriorates due to pin layout vulnerabilities to short circuits
Solution Approach 1:
The patent divides the sensor system into two physically separate sensors instead of integrating them in one IC package. Each sensor is independently mounted on the PCB, allowing galvanic isolation and eliminating pin layout vulnerabilities. This segmentation maintains reliability while managing device complexity through modular construction.
Solution Approach 2:
The patent positions the two sensors at different spatial locations relative to the magnet - one sensor closer to the magnet and the other farther away. This dimensional separation in space allows both sensors to detect the magnetic field from the same magnet while maintaining galvanic isolation, achieving redundancy without physical integration.
2Measurement precision
If a magnet is positioned directly over the top of the sensor, then measurement precision is improved, but device complexity increases due to strict alignment constraints
Solution Approach 1:
The patent applies different local qualities to the two sensors: the first sensor is positioned closer to the magnet for primary detection, while the second sensor is positioned farther away. This asymmetric positioning creates local optimization where each sensor operates in its optimal detection zone, reducing the need for precise overall alignment while maintaining measurement precision.
Solution Approach 2:
The patent introduces a non-magnetic substrate as an intermediary between the magnet and the sensors. This substrate allows the magnet to be positioned on one side while sensors are mounted on the opposite side, eliminating the need for direct alignment between the magnet and sensor field sensing surfaces while maintaining effective magnetic field detection.
3Reliability
If two galvanically isolated systems are used for data verification, then reliability is improved, but device complexity increases due to separate sensor requirements
Solution Approach 1:
The patent uses the same type of magnetic field sensor for both detection positions, making the sensor design universal. Both sensors can be identical models mounted at different locations, simplifying the system configuration while achieving galvanic isolation and data verification capabilities through their spatial separation rather than through different sensor architectures.
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 provides a redundant and reliable position sensing system capable of withstanding high voltages, eliminating the need for a secondary magnet and preventing short circuits, suitable for safety-critical applications.
Implementation Method 1
a first magnetic field sensor provided on the first surface of the substrate... a field sensing surface of the first magnetic field sensor is positioned closer to the magnet
Implementation Method 2
a second magnetic field sensor provided on the second surface of the substrate and directly opposite the first magnetic field sensor
Implementation Method 3
A layer of magnetic material may be disposed over the field sensing surface of the second magnetic field sensor
Data Source
AI summary
Different approaches for providing increased redundancy in determining a position of a rotating member, for example, a motor shaft, with galvanically isolated sensors. In one aspect, two separate on-axis sensing chips are positioned in line with one another on a PCB but each on opposite sides or surfaces of the PCB. Respective sensing surfaces are essentially parallel to one another. Advantageously, greater electrical isolation is provided by placing the two sensors on opposite sides of the PCB.