Brushless Motor Sensorless Control via Kickback Pulse Detection
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Solution Overview
Problem
Existing sensorless control techniques for brushless direct current (BLDC) motors face difficulties at high speeds due to challenges in monitoring zero voltage crossings in non-energized motor windings, which limits the maximum operational speed and reliability.
Innovation Solution
A method and circuitry for detecting a kickback pulse in a non-driven winding, masking only the leading edge of the pulse, and detecting the falling edge to identify a rotor-induced zero crossing, which is used to generate a signal for commutation, allowing for accurate rotor position determination without sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless control is implemented by monitoring zero voltage crossings in non-energized windings, then cost and weight are reduced, but reliability deteriorates at high speeds
Solution Approach 1:
The patent segments the kickback pulse detection into two distinct parts: masking the leading edge and detecting the falling edge. This segmentation allows the system to eliminate false zero-crossing detections caused by the leading edge while preserving valid rotor position information from the falling edge, thereby maintaining control reliability at high speeds
Solution Approach 2:
The patent applies preliminary action by masking the leading edge of the kickback pulse before zero-crossing detection occurs. This pre-processing step prevents false detections from occurring in the first place, ensuring that only valid rotor-induced zero crossings are detected even at high operational speeds
2Measurement precision
If the entire kickback pulse is masked to prevent false detections, then measurement precision improves, but the risk of masking valid rotor-induced zero crossings increases
Solution Approach 1:
The patent divides the kickback pulse handling into two segments: masking only the leading edge while allowing the falling edge to pass through for detection. This selective segmentation maintains measurement precision by eliminating false detections while preserving valid rotor position information, preventing commutation errors
Solution Approach 2:
The patent applies local quality by treating different parts of the kickback pulse differently: the leading edge is masked to prevent false detections, while the falling edge is preserved for valid zero-crossing detection. This localized differentiation optimizes both detection accuracy and commutation reliability
3Measurement precision
If Hall effect sensors are used for rotor position sensing, then measurement precision improves, but cost, weight, and device complexity increase
Solution Approach 1:
The patent extracts the position sensing function from separate Hall effect sensors and implements it through signal processing of existing motor phase signals. By taking out the sensor component and replacing it with circuit-based detection of zero crossings in non-energized windings, the system achieves comparable measurement precision while reducing device complexity, cost, and weight
Solution Approach 2:
The patent creates a functional copy of the Hall sensor output by detecting zero crossings in the back-EMF of non-energized windings. This copying approach generates equivalent rotor position information without requiring physical sensors, thereby reducing system complexity 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 reliable commutation at higher speeds by reducing the risk of masking rotor-induced zero crossings and automatically adjusting to variations in winding inductance and switching resistance, enhancing the motor's operational range and reliability.
Implementation Method 1
detecting a kickback pulse in a non-driven winding of the motor; detecting a rotor-induced zero crossing in the non-driven winding following the detection of the kickback pulse
Implementation Method 2
estimation of the rotor speed and/or position based on induced electromotive force (EMF) or back-EMF occurring in a non-energized stator winding
Data Source
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Figure 3A
AI summary
Systems and methods for generating a signal useful in the commutation of current through windings of brushless direct current electric motors (10) are provided. Such methods comprises detecting a kickback pulse (26) in a non-driven winding (L1-L3) of a motor; detecting a rotor-induced zero crossing (32) in the non-driven winding following the detection of the kickback pulse; and using the detection of the rotor-induced zero crossing to generate a signal useful in commutation of the motor.