Integrated BLDC Motor With Absolute Magnetic Position Sensing
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Solution Overview
Problem
Brushless DC electric motors face challenges in achieving high-resolution position accuracy and precision motion control without the use of additional hardware encoders, which limits their applicability in precise applications such as diagnostic systems and small-scale devices.
Innovation Solution
Integration of an absolute encoder within the motor, utilizing a rotor with inner and outer magnetic rings and analog Hall-effect sensors, allowing for high-resolution position determination through geometric and algebraic interpolation, and a microcontroller with ADC for motor commutation and control, enabling wireless or power-line communication for control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall-effect sensors are used for motor commutation, then motor operation is achieved, but position encoding accuracy is limited
Solution Approach 1:
The patent makes the motor magnets serve dual purposes: generating motor torque and providing position encoding information. The same magnets that drive motor operation are used by the Hall-effect sensors to encode position, eliminating the need for separate encoder magnets or additional sensing hardware. This multi-functionality resolves the contradiction by improving measurement precision without adding device complexity.
Solution Approach 2:
The patent combines the motor function and encoder function into a single integrated system. The magnets are arranged to simultaneously produce motor torque and magnetic field patterns for position sensing. By merging these two functions into one system using the same physical components, the patent achieves high-position accuracy without increasing overall device complexity.
2Measurement precision
If conventional hardware encoders are added for high-resolution position feedback, then position accuracy improves, but mechanical packaging becomes larger and more complex
Solution Approach 1:
The patent merges the encoder functionality directly into the motor structure by using the motor's own magnets for position encoding. This integration eliminates the need for separate encoder assemblies, reducing mechanical packaging complexity while maintaining high position feedback resolution. The same magnetic field that drives motor operation is used for position sensing.
Solution Approach 2:
The motor magnets perform multiple functions simultaneously: generating torque for motor operation and providing magnetic field patterns for high-resolution position encoding. This multi-functionality allows the system to achieve encoder-level position accuracy without adding separate encoder hardware, thereby simplifying mechanical packaging.
3Measurement precision
If additional encoder hardware is incorporated for precision motion control, then position determination accuracy improves, but device size and cost increase
Solution Approach 1:
The patent combines position determination functionality with the motor's existing magnetic structure. By using the motor magnets to generate both torque and encoding signals, the system achieves high position determination accuracy without adding separate encoder hardware, thereby reducing overall device complexity and cost.
Solution Approach 2:
The motor magnets are designed to serve dual purposes: motor operation and position encoding. This multi-functionality allows the system to achieve precision motion control capabilities without incorporating additional encoder hardware, reducing both device complexity and cost while maintaining high measurement precision.
4Measurement precision
If incremental encoders are used, then position changes can be tracked, but absolute position requires continuous movement and cannot provide instant positioning
Solution Approach 1:
The patent replaces incremental encoding with absolute encoding using Hall-effect sensors that directly measure the magnetic field pattern. This substitution allows the system to determine absolute position instantly without requiring continuous movement or counting pulses, eliminating the time delay associated with incremental encoders while maintaining measurement precision.
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 approach enables compact, lightweight, and cost-effective motor systems with high-resolution position feedback, reducing mechanical complexity and enhancing precision in motion control without the need for additional encoder hardware, suitable for robotic, automation, and diagnostic applications.
Implementation Method 1
analog Hall-effect sensors
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 a first set of permanent magnets distributed radially about the rotor to facilitate rotation of the rotor and a second set of permanent magnets on the rotor to facilitate determination of an absolute position of the rotor. The motor further includes first and second set of sensors for detection of the magnets of the inner and outer rings. 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 absolute position of the rotor relative the substrate to be determined from the sinusoidal signals without requiring use of an encoder or position sensors and without requiring noise-reduction or filtering of the signal.