Brushless DC Motor Position Estimation Using Hall Sensors
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Solution Overview
Problem
Existing control systems for sinusoidal-drive brushless DC electric motors in automotive power actuators face challenges with high costs and error likelihood due to the use of high-resolution sensors, necessitating a simpler yet reliable control solution.
Innovation Solution
A control system utilizing low-resolution Hall position sensors with a position estimation method based on time integration of motor speed, combining sensed and estimated positions using weighted coefficients to accurately control the brushless DC electric motor in sinusoidal mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution position sensors (encoders, resolvers) are used for sinusoidal drive control, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a virtual copy of the high-resolution position sensor functionality through software-based position estimation. Instead of physically installing expensive encoders or resolvers, the system uses low-resolution Hall sensors combined with mathematical algorithms (time integration of speed, observer-based estimation) to generate accurate rotor position information, effectively copying the function of high-resolution sensors using cheaper components
Solution Approach 2:
The patent replaces the mechanical/optical sensor system (encoders, resolvers) with an electrical/software-based estimation system. The physical measurement mechanism is substituted with computational methods including time integration of motor speed and observer-based position estimation, eliminating the need for complex mechanical sensing components
2Device complexity
If low-resolution Hall sensors are used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The system performs preliminary actions to compensate for the low resolution of Hall sensors. Before using Hall sensor data for control, the system pre-processes the signals through time integration of speed and observer-based estimation algorithms, preparing enhanced position information in advance that compensates for the inherent low resolution of the Hall sensors
Solution Approach 2:
The patent implements feedback mechanisms where the estimated position and speed are continuously refined based on motor current feedback and electrical angle calculations. The observer-based estimation uses feedback from phase currents and voltage to continuously update and improve position accuracy, creating a closed-loop system that compensates for the low resolution of Hall sensors
3Device complexity
If trapezoidal drive control is used, then device complexity is reduced, but harmful factors (torque ripple, mechanical noise) increase
Solution Approach 1:
The patent transitions from the static, discontinuous switching characteristics of trapezoidal drive to a dynamic, continuous control approach. By using sinusoidal current waveforms generated through PWM modulation based on accurately estimated rotor position, the system creates smooth, continuous torque production that eliminates the abrupt transitions and associated mechanical noise inherent in trapezoidal drive
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 provides a reliable and cost-effective control of the brushless DC electric motor, reducing mechanical noise and torque ripple without the need for expensive high-resolution sensors.
Implementation Method 1
using three on/off Hall position sensors 4a, 4b, 4c, the magnetic position of the rotor 3 may be detected
Implementation Method 2
Control of the brushless DC electric motor 1 envisages electrical periodical switching of the currents flowing in the stator windings 2a, 2b, 2c, in order to maintain the rotation of the rotor 3, via the resulting magnetic interaction
Data Source
AI summary
A control system (14) for controlling a brushless electric motor (1) for an automotive power actuator (10), having a rotor (3) operable to rotate with respect to stator windings (2a, 2b, 2c), the control system (14) is provided with: a position sensing unit (4a-4c, 30) coupled to the rotor (3), to sense its angular position and to provide a sensed position (θ); and a generation unit (24), to generate driving voltages and/or currents for the stator windings (2a, 2b, 2c), as a function of the angular position of the rotor (3). A position estimation module (25) is coupled to the position sensing unit (4a-4c, 30), to receive the sensed position (θ) and to correct the value of the sensed position (θ), thereby providing a corrected angular position (θr) to the generation unit (24).