Sensorless BLDC Motor Control via Non-Commutation PWM
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Solution Overview
Problem
Existing sensorless BLDC motor driving methods face challenges in accurately detecting the Zero Cross Point (ZCP) during non-commutation periods, especially at low speeds, due to noise components and limitations in extracting phase back EMF without additional sensors, which affects rotor position estimation and commutation timing.
Innovation Solution
A device and method that utilize a three-phase inverter, terminal voltage detector, and controller for PWM control with non-commutation periods to detect ZCP based on back EMF, eliminating switching noise and enabling precise rotor position estimation and commutation timing without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sensorless method is used to avoid additional sensors, then manufacturing cost and circuit complexity are reduced, but measurement precision of rotor position is degraded
Solution Approach 1:
The patent uses back EMF voltage as an intermediary signal to indirectly detect rotor position. By detecting the zero-crossing point of the back EMF voltage generated during non-commutation periods, the system obtains rotor position information without physical sensors, thus resolving the contradiction between cost reduction and measurement precision.
Solution Approach 2:
The patent replaces mechanical sensor-based detection with electrical signal-based detection. Instead of using physical sensors to detect rotor position, the system uses electrical signals (back EMF voltage) generated by the motor itself, substituting a mechanical detection system with an electrical one to reduce cost while maintaining measurement capability.
2Productivity
If PWM control is used for motor operation, then control flexibility and efficiency are improved, but switching noise interferes with back EMF detection
Solution Approach 1:
The patent extracts and utilizes the non-commutation periods from the PWM control cycle. During these specific time intervals when switching is suspended, the back EMF voltage can be detected without interference from switching noise. This extracts useful detection opportunities from within the PWM control framework, resolving the contradiction between control efficiency and noise interference.
Solution Approach 2:
The patent employs periodic non-commutation intervals within the PWM control cycle. By periodically suspending switching operations at specific phases, the system creates regular windows for noise-free back EMF detection, allowing continuous motor control while periodically eliminating switching noise interference.
3Measurement precision
If non-commutation period is introduced for ZCP detection, then measurement precision is improved, but control complexity increases
Solution Approach 1:
The patent makes the existing PWM control circuit multi-functional by having it serve both motor control and position detection purposes. The same control circuit that manages PWM switching also generates the non-commutation periods needed for back EMF detection, eliminating the need for separate detection circuitry and thus avoiding increased complexity while improving 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
The proposed solution enhances the accuracy of ZCP detection and rotor position estimation, improving the precision of BLDC motor control by removing switching noise and allowing for accurate commutation timing, even at low speeds, without the need for additional position detection sensors.
Implementation Method 1
a three phase inverter configured to convert a DC input voltage into a three phase AC voltage and supply the three phase AC voltage to the BLDC motor
Implementation Method 2
extracting a back electromotive force (EMF) generated in stator coil of each phase while the motor is rotated
Data Source
AI summary
A device and control method for driving a sensorless brushless DC (BLDC) motor, particularly related to a technology configured to increase the accuracy of detection of Zero Cross Point through a non-commutation period in a pulse width modulation (PWM) control. The device for driving a sensorless BLDC motor to switch a current applied to a stator winding based on a position of a rotor includes a three phase inverter configured to convert a DC input voltage into a three phase AC voltage and supply the three phase AC voltage to the BLDC motor; a terminal voltage detector configured to detect a three phase terminal voltage from an output terminal of the three phase inverter; and a controller configured to perform a PWM control of the terminal voltage based on a three phase back electromotive force (EMF) included in the detected terminal voltage. The PWM control includes a non-commutation control in which the switching of the current does not occur.