BLDC Compressor Control Using Analog Hall Sensors at Low Speeds
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Solution Overview
Problem
Existing BLDC motor control systems for portable ventilators lack precise speed control at all rotor speeds, especially at low speeds, due to the use of simple motor controllers and separate speed transducers which increase device size, weight, and cost, making them unsuitable for compact and affordable portable ventilator designs.
Innovation Solution
A control system using analog Hall effect sensors to provide continuous rotor position and speed feedback, allowing for precise speed control of a BLDC motor driving a Roots blower compressor, independent of rotor speed, eliminating the need for separate speed transducers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate speed transducers are used for BLDC motor control, then speed measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the speed sensing function with the existing Hall effect sensors already present in the BLDC motor system. Instead of adding separate speed transducers, the invention merges speed measurement capability into the existing motor control circuitry by utilizing the magnetic field information from the rotor position sensors, thereby eliminating additional components while maintaining measurement precision.
Solution Approach 2:
The BLDC motor's own Hall effect sensors serve dual purposes: both commutation control and speed measurement. The system uses its existing magnetic field sensing capability to generate speed information through software processing of rotor position data, allowing the motor to self-monitor its speed without external transducers.
2Ease of manufacture
If simple motor controllers are used, then device cost is reduced, but speed control precision deteriorates
Solution Approach 1:
The patent replaces complex hardware-based speed control mechanisms with software-based processing. By using digital signal processing algorithms to analyze Hall effect sensor outputs, the system achieves precise speed control through computational methods rather than additional mechanical or electronic control components, reducing overall system cost while maintaining precision.
Solution Approach 2:
The invention changes the control approach from hardware-parameter based to software-parameter based speed control. By processing Hall effect sensor signals through algorithms that calculate rotor speed based on position changes over time, the system achieves precise speed control using software parameters rather than complex hardware control circuits.
3Weight of moving object
If device size is reduced for portability, then weight is reduced, but speed control capability deteriorates
Solution Approach 1:
The patent makes the Hall effect sensors multi-functional by using them for both commutation and speed measurement. This universal utilization of existing components eliminates the need for separate speed sensing hardware, allowing the device to maintain full speed control capability while reducing overall system weight and size for portable application.
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
Enables accurate and efficient control of airflow in portable ventilators by maintaining speed and position accuracy across the full range of rotor speeds, reducing the size, weight, and cost of the device while ensuring precise speed control.
Implementation Method 1
A control system using analog Hall effect sensors to provide continuous rotor position and speed feedback
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.