Magnetically Sensitive Memory Rotor Position Detection
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Solution Overview
Problem
Existing methods for determining the angular position of a motor rotor, especially in multi-turn applications, are complex and prone to errors due to reliance on analog signals and additional circuitry, which complicates accurate position detection and storage.
Innovation Solution
A method utilizing a magnetically sensitive memory, such as MRAM, where the magnetization pattern of memory cells directly correlates with the rotor's angular position, allowing digital detection without the need for AD converters, and enabling storage of multi-turn positions in non-volatile memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog-based position detection methods (Hall sensors, capacitive methods) are used, then position measurement is achievable, but the system requires ADC converters and analog circuitry which increases complexity and introduces temperature drift and offset errors
Solution Approach 1:
The patent replaces analog magnetic field sensing with a digital memory-based system. Instead of using Hall sensors that convert magnetic field strength to analog voltage signals requiring ADC conversion, the invention uses magnetically sensitive memory cells (TMR effect) that directly output digital resistance states (0 or 1) based on magnetic field direction, eliminating the need for ADC converters and analog signal conditioning circuits
Solution Approach 2:
The patent changes the operating parameter from continuous analog voltage levels to discrete digital resistance states. The magnetically sensitive memory cells exhibit high resistance in one magnetic direction and low resistance in the opposite direction, creating natural binary output states that are inherently digital and immune to temperature drift and offset errors affecting analog systems
2Measurement precision
If incremental encoders are used for position detection, then angular resolution can be achieved through multiple tracks, but the system becomes complex and requires precise mechanical alignment
Solution Approach 1:
The patent extracts the position detection function from complex mechanical encoder structures and implements it using a simple magnetically sensitive memory chip. Instead of using multiple mechanical tracks with precise alignment requirements, the invention uses a single memory chip where different memory cells are selectively magnetized based on rotor angle, achieving high angular resolution through digital pattern recognition rather than mechanical complexity
Solution Approach 2:
The patent creates a digital copy of the angular position information in the magnetization pattern of memory cells. The geometric position of magnetized cells on the memory chip directly encodes the angular position, allowing the evaluation unit to determine rotor angle by reading the digital pattern of magnetized versus non-magnetized cells, eliminating the need for physical encoder tracks
3Reliability
If non-volatile memory is used to store revolution count for multi-turn applications, then position persistence across power failures is achieved, but additional memory resources and writing operations are required
Solution Approach 1:
The patent makes the magnetically sensitive memory chip multi-functional by using it both for position detection and for storing revolution count. The same memory cells that detect angular position through magnetic field-induced magnetization can also store persistent position information through their non-volatile nature, eliminating the need for separate volatile and non-volatile memory components and reducing overall system complexity
Solution Approach 2:
The patent merges the position detection function and the position storage function into a single magnetically sensitive memory system. The memory chip simultaneously serves as the sensor that detects rotor angle and as the non-volatile storage that preserves position information across power cycles, reducing component count and simplifying the control architecture
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 solution provides a simple, accurate, and error-resistant digital measurement of the rotor's position, eliminating the need for analog circuitry and ensuring permanent storage of angular data across power failures.
Implementation Method 1
at least one magnet being connected directly or indirectly to a motor axis, with at least one magnetically sensitive memory having a plurality of memory cells being arranged in such a way that at least some of the memory cells are magnetized by the magnet
Implementation Method 2
magnetically sensitive memory (e.g. MRAM, magnetoresistive random access memory)
Data Source
Figure 1~2
AI summary
The invention relates to a method for determining the angular position of a rotor of a motor, to an angular position transmitter, and to a motor. In order to provide a simple solution for determining the angular position of a rotor, according to the invention at least one magnet is indirectly or directly connected to a motor shaft, at least one magnetically sensitive storage unit comprising a plurality of storage cells is arranged such that at least some of the storage cells are magnetized by the magnet, the storage cells are read, and the angular position is determined from a geometric position of the magnetized cells.