Encoderless BLDC Motor Position Sensing from Sinusoidal Voltage Signals
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Solution Overview
Problem
Brushless DC electric motors lack high resolution and positional accuracy without additional encoder hardware or noise-filtering, which limits their precision in applications requiring precise motor control.
Innovation Solution
A system that encodes a brushless DC electric motor using multiple voltage sensors and a processor module to determine motor displacement from sinusoidal signals without hardware encoders or positional sensors, utilizing matrix transformations to eliminate noise and improve resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional encoder hardware is used to improve resolution and positional accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the encoding function from separate hardware components and integrates it into the existing voltage sensor system. By processing the back-EMF signals already present in the motor system through matrix transformations, the patent achieves high-resolution position sensing without adding dedicated encoder hardware, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The voltage sensors originally designed for commutation purposes are made multi-functional by also serving as position sensors. The same sensors that detect back-EMF for motor control are simultaneously used for high-resolution position encoding through signal processing, eliminating the need for separate encoder hardware while maintaining measurement precision
2Measurement precision
If noise-filtering is applied to improve signal accuracy, then measurement precision is improved, but loss of information increases
Solution Approach 1:
The patent replaces traditional noise-filtering mechanisms with mathematical signal processing techniques. Instead of using hardware filters that remove frequency components, the system uses matrix transformations and coordinate transformations to extract position information directly from the raw sinusoidal signals, preserving all signal information while achieving high measurement precision
Solution Approach 2:
The patent changes the parameter representation of the signal from time-domain voltage measurements to spatial-domain position coordinates through mathematical transformations. This parameter transformation allows accurate position determination without losing signal information, as the transformation is reversible and preserves the complete signal content
3Ease of operation
If piece-wise applied algorithms are used for signal processing, then ease of operation is improved, but measurement precision deteriorates due to electrical cycle harmonics
Solution Approach 1:
The patent introduces an intermediary coordinate transformation step that converts the three-phase voltage signals into a two-phase reference frame before position calculation. This intermediary transformation eliminates electrical cycle harmonics and piece-wise algorithm artifacts, providing a continuous and accurate position signal while maintaining computational simplicity through standardized transformation matrices
4Measurement precision
If permanent magnets extend beyond the magnetic core to reduce signal noise, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the motor's own magnetic field structure serve the dual purpose of both motor operation and position sensing. By extending the permanent magnets beyond the magnetic core, the system uses the motor's inherent magnetic field to provide clean, noise-free sinusoidal signals for position encoding, eliminating the need for separate sensing magnets or additional structural complexity
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
Achieves extraordinarily high resolution and positional accuracy in motor control, enabling precise displacement determination and reduced runout without additional hardware or noise-filtering, suitable for applications like diagnostic assays and robotic systems.
Implementation Method 1
multiple voltage sensors at fixed positions relative the stator and disposed adjacent a path of the plurality of magnets during movement of the movable element
Implementation Method 2
determine a displacement of the motor from the voltage signals from the sensors without requiring use of a hardware encoder or additional position-based sensor and/or without error correction of the signal
Data Source
AI summary
A DC electric motor having a stator mounted to a substrate, the stator having a coil assembly having a magnetic core, a rotor mounted to the stator with permanent magnets distributed radially about the rotor, the permanent magnets extending beyond the magnetic core, and sensors mounted to the substrate adjacent the permanent magnets. During operation of the motor passage of the permanent magnets over the sensors produces a substantially sinusoidal signal of varying voltage substantially without noise and/or saturation, allowing an angular position of the rotor to be determined from the sinusoidal signals by utilizing a transformation matrix or piece-wise algorithm applied in substantially linear portions of the sinusoidal signals without requiring use of additional hardware encoder or position sensors and without requiring noise-reduction or filtering of the signal.