Permanent Magnet Motor Rotor Position Estimation via N-Division
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Solution Overview
Problem
Traditional methods for determining rotor position in permanent magnet synchronous motors, such as using mechanical sensors, increase system complexity and are prone to interference, while sensorless control methods like sliding mode observers and traditional PLLs suffer from robustness issues and decreased system bandwidth.
Innovation Solution
A fast rotor position estimation method using the N-division approach, which divides the rotor position plane into regions based on stator current characteristics, constructs a cost function, and iteratively optimizes the rotor position estimation without additional observers, reducing calculation amount and improving system bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical position sensors are used to obtain rotor position, then rotor position can be obtained, but the connection line between motor and control system increases and power density decreases
Solution Approach 1:
The patent replaces mechanical position sensors with a sensorless control method that uses mathematical models and signal processing to estimate rotor position from motor electrical characteristics, eliminating the need for physical sensors and their associated connection lines
2Measurement precision
If mechanical position sensors are used, then rotor position can be obtained, but reliability decreases due to interference from motor vibration, temperature, and electromagnetic noise
Solution Approach 1:
The patent replaces vulnerable mechanical sensors with an electronic-based sensorless estimation method that derives rotor position from electrical measurements and mathematical models, which are less susceptible to mechanical vibrations and environmental interference
Solution Approach 2:
The patent introduces intermediate signal processing steps including coordinate transformations and cost function calculations that act as mediators to extract rotor position information indirectly through electrical characteristics rather than direct mechanical measurement
3Ease of operation
If traditional PLL with fixed gain is used, then rotor position can be demodulated, but robustness is weak
Solution Approach 1:
The patent transforms the static fixed-gain PLL into a dynamic adaptive system where the cost function and optimization process continuously adjust to changing operating conditions, enabling the system to maintain robustness across different speeds and load conditions
4Measurement precision
If sliding mode observer and PLL are combined, then rotor position can be estimated, but system bandwidth decreases affecting dynamic performance
Solution Approach 1:
The patent extracts and eliminates the bandwidth-limiting PLL component from the traditional observer-based approach, using direct cost function optimization instead, which removes the bottleneck in the control loop and allows for faster dynamic response
5Measurement precision
If FPS-PLL with 24 iterations is used, then accurate rotor position can be obtained, but calculation amount is large
Solution Approach 1:
The patent segments the rotor position plane into N distinct regions and uses the cost function to identify which region contains the actual rotor position, then performs refined estimation only within that specific region rather than searching the entire 360-degree range, significantly reducing computational iterations
Data Source
AI summary
A method for quickly determining the rotor position of a permanent magnet motor using the N-division approach is provided. The method involves converting the motor's three-phase stator current coordinates into the dq two-phase synchronous rotation coordinate system and identifying the initial rotor position area. By establishing a stator current cost model and utilizing the d-axis stator current, the initial rotor position can be obtained. Subsequently, the N-division approach is employed for iterative optimization to obtain the estimated rotor position and the final position region, leading to a rapid estimation of the permanent magnet motor's rotor position. This method incorporates the finite set model predictive control concept into a phase-locked loop based on stator current, eliminating the need for additional rotor position polarity judgment and invalid rotor position control variables.