Portable Ventilator BLDC Compressor Control With Analog Hall Feedback
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Solution Overview
Problem
Existing BLDC motor control systems for portable ventilators face challenges in achieving precise speed control without the added cost, size, and weight of separate speed transducers, as simple BLDC motor controllers provide coarse speed detection, which is insufficient for the transient response required in these applications.
Innovation Solution
The use of analog Hall effect sensors to provide continuous rotor position and speed feedback, allowing for precise speed control of BLDC motors without the need for separate speed transducers, by sampling sensor signals independently of rotor speed and processing them using methods like the arctangent function to calculate angular position and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple BLDC motor controllers with commutation states are used, then device complexity is reduced, but measurement precision of rotor position and speed deteriorates
Solution Approach 1:
The patent replaces mechanical/optical speed transducers with electronic Hall effect sensors integrated into the BLDC motor controller. This substitution provides continuous rotor position and speed feedback through magnetic field detection, achieving precise measurement without adding mechanical complexity or separate transducer components.
Solution Approach 2:
The Hall effect sensors are integrated directly into the motor controller circuit board, allowing the controller to self-monitor rotor position and speed using magnetic field information from the motor itself. This eliminates the need for external speed transducers and enables the system to serve its own measurement needs.
2Measurement precision
If separate speed transducers are added to achieve precise speed control, then measurement precision improves, but device complexity, size, and cost increase
Solution Approach 1:
The patent merges the speed sensing function with the existing motor controller by integrating Hall effect sensors onto the controller circuit board. This combination eliminates separate speed transducers while maintaining precise speed control capability, reducing overall system complexity and component count.
Solution Approach 2:
The Hall effect sensors serve multiple functions: providing continuous rotor position feedback for commutation control and simultaneous speed feedback for speed regulation. This multi-functionality replaces what would traditionally require separate position and speed transducers.
3Device complexity
If commutation state information is used for speed control, then device complexity is minimized, but transient response deteriorates especially at low speeds
Solution Approach 1:
The patent implements continuous feedback of rotor speed derived from Hall effect sensor signals to the controller. This feedback enables real-time speed regulation and improves transient response by allowing the controller to actively adjust motor drive signals based on actual speed conditions, particularly enhancing low-speed response.
4Productivity
If the motor is accelerated rapidly from rest to high speed, then productivity is improved, but control precision deteriorates during transient phases
Solution Approach 1:
The patent employs dynamic speed control by continuously monitoring rotor speed through Hall effect sensors and adjusting motor drive signals in real-time. This dynamic control maintains precision during rapid acceleration transients by adapting the control strategy to instantaneous speed conditions.
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 accurate rotor speed control across the full range of speeds, maintaining precision and reducing the complexity and cost of the control system, making it suitable for compact, lightweight, and affordable portable ventilator designs.
Implementation Method 1
analog Hall sensors 401A-D provide continuous signals in response to the magnetic flux sensed from a magnet 412 attached to the rotor 402
Data Source
AI summary
A method and apparatus for controlling a brushless DC (BLDC) motor over a wide range of angular speeds is presented. Analog magnetic sensors provide continuous signal measurements related to the rotor angular position at a sample rate independent of rotor angular speed. In one embodiment, analog signal measurements are subsequently processed using an arctangent function to obtain the rotor angular position. The arctangent may be computed using arithmetic computation, a small angle approximation, a polynomial evaluation approach, a table lookup approach, or a combination of various methods. In one embodiment, the BLDC rotor is used to drive a Roots blower used as a compressor in a portable mechanical ventilator system.