Rotor Position Estimation via Dual High-Frequency Signal Injection
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Solution Overview
Problem
Accurate estimation of rotor position in permanent magnet synchronous motors (PMSM) is crucial for stable operation, but existing methods often result in operational instability due to deviations between estimated and actual rotor positions.
Innovation Solution
The method involves injecting a first and second high frequency signal at different estimating angles to generate sensing signals, determining the quadrant of the operating angle, and calculating the rotor position using these signals and the angle difference, thereby improving estimation accuracy and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single high frequency signal is injected at one estimating angle to determine rotor position, then the device complexity is reduced, but the measurement precision and reliability of rotor position estimation deteriorate due to inability to accurately determine the quadrant of operating angle
Solution Approach 1:
The rotor position estimation process is segmented into multiple independent measurement steps. Instead of using a single signal injection, the method divides the estimation into two separate high frequency signal injections at different estimating angles (first estimating angle and second estimating angle). Each injection provides partial information (sensing signals) that, when combined, enable complete and accurate quadrant determination of the operating angle, thereby improving measurement precision without excessive complexity increase.
Solution Approach 2:
The method transitions from a single-dimension estimation approach to a two-dimension approach by introducing a second estimating angle perpendicular to the first. This dimensional expansion allows the system to determine both the magnitude and quadrant of the operating angle, resolving the ambiguity that exists in single-angle methods and significantly improving rotor position estimation accuracy.
2Measurement precision
If multiple high frequency signals are injected at different estimating angles to improve rotor position accuracy, then the measurement precision improves, but the loss of time increases due to multiple signal injection cycles
Solution Approach 1:
The method employs periodic action by injecting high frequency signals in alternating cycles along the d-axis and q-axis. The first high frequency signal is injected along the d-axis in one period, followed by the second high frequency signal along the q-axis in the next period. This periodic alternation allows continuous rotor position estimation while maintaining accuracy, as the controller can process signals from one axis while preparing for the next injection, thereby reducing overall time loss.
3Device complexity
If the quadrant of operating angle is not accurately determined, then the device complexity is reduced, but the reliability of motor control deteriorates causing rotational direction errors
Solution Approach 1:
The method implements feedback by using the sensing signals from both d-axis and q-axis signal injections to determine the quadrant of the operating angle. The controller continuously monitors the signs of the sensing signals and uses this feedback information to correctly identify which quadrant the operating angle resides in. This feedback mechanism ensures that even with increased algorithm complexity, the motor control reliability is maintained by preventing rotational direction errors through accurate quadrant determination.
Data Source
AI summary
An estimating method for a rotor position of a motor and an estimating device for the same are disclosed herein. The estimating method includes injecting a first high frequency signal to the motor at a first estimating angle, generating a first sensing signal of the motor in a period when the first high frequency signal is injected to the motor, injecting a second high frequency signal to the motor at a second estimating angle, generating a second sensing signal of the motor in a period when the second high frequency signal is injected to the motor, determining a quadrant of an operating angle according to the first sensing signal and the second sensing signal, and acquiring the rotor position according to the first sensing signal, the second sensing signal, and the quadrant of the operating angle.