Electric Motor Rotor Position Determination with Noise Filtering
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Solution Overview
Problem
Existing electric motor position sensing systems face noise interference from sources like parasitic electromagnetic fields and switching actions, leading to inaccurate position readings and control signals.
Innovation Solution
A method that involves storing previous position readings and using them to determine predicted positions based on speed readings, with thresholds to select reliable final position readings, reducing noise impact and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor or resolver is used to determine rotor position, then position reading capability is provided, but noise interference corrupts position readings
Solution Approach 1:
The system performs preliminary actions by storing multiple previous position readings and calculating expected position values before evaluating the current reading. This predictive approach allows the system to prepare reference values in advance, enabling faster and more accurate noise filtering when the current reading is evaluated against these pre-calculated expectations.
Solution Approach 2:
The system implements feedback by continuously comparing current position readings against expected values derived from previous readings and motor speed. This closed-loop evaluation allows the system to detect deviations caused by noise and correct them by selecting readings that are consistent with the motor's actual motion state, thereby improving measurement precision despite noise interference.
2Measurement precision
If multiple previous position readings are stored and processed to filter noise, then position reading accuracy improves, but processing complexity increases
Solution Approach 1:
The system applies partial action by storing only a limited number of previous position readings (e.g., 2-5 readings) rather than all historical data. This selective storage provides sufficient information for accurate noise filtering while keeping memory requirements and processing complexity manageable. The system processes only the essential previous readings needed to establish expected position values.
Solution Approach 2:
The system performs self-service by using its own previous position readings and speed information to generate expected position values, eliminating the need for external reference systems or complex calibration procedures. The motor's own operational data serves as the reference for filtering noise, simplifying the overall system architecture while maintaining high accuracy.
Data Source
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AI summary
A data storage device stores previous position readings of the rotor for a previous cycle of a pulse width modulation signal applied to the motor (S300). A current raw position reading for the current cycle is received (S302). A predicted position reading for a current cycle is determined based on at least one of the stored previous position readings of the previous cycle (S304). A data processor determines whether a difference between the current raw position reading and the predicted position reading for a first mode and a second mode is within one or more preset thresholds (S306, S307). The data processor selects the current raw position reading as a verified reliable final position reading if a first difference for the first mode is equal to or less than a primary preset threshold or if a second difference for the second mode is equal to or less than a secondary preset threshold (S308).