Electric Motor Control Device for Accurate Magnetic Pole Position Estimation
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Solution Overview
Problem
Existing electric motor control devices face challenges in accurately estimating the magnetic pole position of a rotor without a position sensor, leading to potential errors and increased heat generation due to the need for high-frequency voltage amplification across the entire electric angle.
Innovation Solution
An electric motor control device that uses a control unit and current sensor to detect fundamental and specific high-frequency currents at different electric angles, comparing these values to enhance estimation accuracy of the magnetic pole position, thereby reducing heat generation by limiting high-frequency voltage amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high frequency voltage amplification is applied across the entire electric angle to improve magnetic pole position estimation accuracy, then estimation accuracy is improved, but heat generation in the drive circuit and motor increases
Solution Approach 1:
The patent applies high frequency voltage only at specific electric angles (0° and 180°) rather than across the entire electric angle range. This localized application of high frequency voltage allows for accurate magnetic pole position estimation while minimizing heat generation in the drive circuit and motor, as the high frequency voltage is applied only when necessary for measurement purposes.
2Measurement precision
If high frequency voltage is continuously applied to improve estimation accuracy, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The patent employs periodic application of high frequency voltage at specific intervals (at electric angles of 0° and 180°) rather than continuous application. This periodic action enables the system to obtain accurate magnetic pole position estimates at critical points while reducing overall energy consumption by avoiding continuous high frequency voltage application throughout the entire rotation cycle.
3Device complexity
If maximum amplitude value is selected from each data of high frequency current to estimate magnetic pole position, then estimation process is simplified, but estimation accuracy deteriorates when difference between maximum values is small
Solution Approach 1:
The patent uses feedback by comparing the absolute values of high frequency currents at electric angles of 0° and 180° to determine the correct magnetic pole position. This feedback mechanism ensures accurate estimation by verifying which direction (0° or 180°) produces the expected current characteristics, thereby avoiding errors that would occur with simple maximum value selection when the difference between maximum values is small.
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
Improves the estimation accuracy of the magnetic pole position while reducing heat generation in the drive circuit and motor, allowing for a more efficient and cost-effective control system.
Implementation Method 1
a high frequency voltage estimation method that applies a high frequency voltage higher than a frequency of a drive voltage of the electric motor to the electric motor, to thereby estimate the magnetic pole position of the rotor
Implementation Method 2
a current sensor that detects a current generated in the electric motor
Data Source
AI summary
An electric motor control device includes a control unit that controls operation of a drive circuit supplying electric power to an electric motor and a current sensor that detects current generated in the electric motor. The control unit detects fundamental high frequency current generated when the electric motor is applied with fundamental high frequency voltage for estimating the magnetic pole position, selects first electric angle and second electric angle corresponding to a d-axis direction of the magnetic pole position, detects first specific high frequency current generated when a position of the first electric angle is applied with specific high frequency voltage and second specific high frequency current generated when a position of the second electric angle is applied with the specific high frequency voltage, and compares the first and the second specific high frequency currents to estimate a positive d-axis direction of the magnetic pole position.