BLDC Rotor Position Detection via Phase Voltage Measurement
Solution Overview
Problem
Current sensorless brushless DC motor (BLDCM) control technologies face challenges in accurately detecting initial rotor position, especially at zero and low speeds, and are inefficient due to the need for additional hardware and sensitivity to temperature and noise, limiting their reliability and cost-effectiveness in applications like cordless power tools and electric vehicles.
Innovation Solution
A method that uses on-time and off-time open phase voltage measurements to detect rotor position without additional electronic circuitry, employing rotor position functions and rotation direction functions to calculate accurate rotor position and direction, and integrating software-controlled synchronous rectification for improved efficiency and torque control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control methods are used to reduce hardware complexity, then device complexity is reduced, but measurement precision of rotor position deteriorates
Solution Approach 1:
The patent replaces mechanical sensor-based position detection with an electrical measurement system. By measuring phase voltages and currents during switching transitions and using mathematical models to calculate rotor position, the system eliminates physical sensors while maintaining measurement capability through electrical field interactions in the motor windings.
Solution Approach 2:
The patent introduces mathematical models and calculation algorithms as intermediaries between the electrical measurements and the rotor position determination. These models translate raw voltage and current measurements into accurate position information without requiring direct mechanical sensing, thus bridging the gap between simplified hardware and precise measurement.
2Measurement precision
If additional electronic circuitry is added to improve measurement accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the motor windings themselves serve the dual purpose of both generating motor operation and providing position detection functionality. The existing phase windings act as both actuators and sensors, eliminating the need for separate detection circuitry by utilizing the motor's own electrical characteristics for position measurement.
Solution Approach 2:
The patent implements a system where the motor's phase windings perform multiple functions: they both drive the motor operation and enable position detection. The same electrical components used for motor control are also utilized for sensing rotor position, thereby avoiding additional hardware while achieving measurement precision.
3Device complexity
If conventional sensorless methods are used, then device complexity is reduced, but reliability deteriorates due to sensitivity to temperature and noise
Solution Approach 1:
The patent implements feedback mechanisms where the measured phase voltages and currents are continuously monitored and used to calculate rotor position. This closed-loop approach allows the system to compensate for temperature variations and noise by continuously adjusting position calculations based on actual electrical measurements, thereby improving reliability without adding complex hardware.
Data Source
AI summary
A method of operating a Brushless Direct Current Motor (BLDCM), the BLDCM of the type including: a series of concentric independently activated electromagnetic phase coils interacting with a series of permanent magnets to provide relative movement therebetween, the phase coils having temporal periods of activation time and deactivation time, the method including the steps of: (a) activating at least one of the phase coils for a short period of activation; and (b) measuring the voltage response across the phase coil of the deactivated phase coil during the short period of activation to determine the rotor position.