Sensorless Brushless Motor Commutation Control
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Solution Overview
Problem
The power of two-phase brushless motors is limited by the intermediate circuit voltage, particularly in battery-powered devices, where the voltage drop restricts the motor's performance, and existing sensorless control methods do not optimize efficiency due to phase current lagging behind induced voltage.
Innovation Solution
Adjusting the commutation angle by setting a predetermined target value for the induced voltage that deviates from zero, allowing the phase-locked loop to synchronize with a reference value, thereby increasing the motor's power output even at lower voltages, and implementing a control device to determine and compare induced voltages for optimal commutation timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the intermediate circuit voltage is reduced in battery-powered devices, then energy efficiency and portability are improved, but the motor power output is limited
Solution Approach 1:
The patent changes the commutation angle parameter from the conventional zero-induced-voltage point to a predetermined target value that deviates from zero. This parameter change allows the motor to operate at optimal power factor even when intermediate circuit voltage drops, maintaining motor power output while accepting lower voltage for improved energy efficiency and portability in battery-powered devices
2Loss of energy
If the commutation angle is adjusted to optimize power factor, then motor efficiency is improved, but control complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism where the microcontroller continuously monitors the induced voltage in the non-energized phase and adjusts the commutation timing accordingly. The system compares the determined induced voltage with a predetermined target value and dynamically adapts the commutation time to maintain optimal power factor, improving motor efficiency through closed-loop control
Solution Approach 2:
The system uses the induced voltage from the non-energized phase itself as the feedback signal for commutation timing, eliminating the need for external position sensors. The motor's own electrical characteristics provide the necessary information for self-regulation of the commutation angle, reducing additional hardware complexity
3Measurement precision
If a position sensor is used for commutation control, then rotor position detection accuracy is improved, but device cost and complexity increase
Solution Approach 1:
The system uses the induced voltage from the non-energized phase itself as the feedback signal for commutation timing, eliminating the need for external position sensors. The motor's own electrical characteristics provide the necessary information for self-regulation of the commutation angle, reducing additional hardware complexity
Solution Approach 2:
The induced voltage in the non-energized phase serves as an intermediary signal that indirectly provides rotor position information. Instead of directly measuring rotor position with sensors, the system uses the electromagnetic coupling between phases to derive commutation timing information, simplifying the overall system
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 increased power output and efficiency of the brushless motor, allowing full performance even at lower voltages, reducing the need for larger converters and minimizing costs and installation space, while maintaining efficient operation.
Implementation Method 1
comparing the determined induced voltage with a predetermined target value of the induced voltage, which is not equal to zero, and adjusting the commutation time, if the difference between the determined induced voltage and the predetermined target value of the induced voltage is not equal to zero
Implementation Method 2
determining the induced voltage of a non-energized phase
Data Source
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AI summary
The invention relates to a method for controlling a brushless motor (M) with at least two phases, preferably without a rotor position sensor, comprising at least the following steps: • Energizing (100) two phases (U, V, W), wherein the voltage (UPhase) of the energizing (100) is set by means of PWM control, • Determining (200) the induced voltage (EMF) of a non-energized phase (U, V, W), • Comparing (300) the determined induced voltage (EMF) with a predetermined setpoint of the induced voltage (EMKRef), which is not equal to zero, and • Adjusting (400) the commutation time if the difference between the determined induced voltage (EMF) and the predetermined setpoint of the induced voltage (EMKRef) is not equal to zero.