Rotor Position Estimation Using Current Squaring
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Solution Overview
Problem
Conventional methods for estimating the rotor position of electric rotating machines without rotational position sensors, such as those using Fourier transforms or random frequency settings, incur increased computational and memory costs, and face challenges in accurate position detection at zero or low speeds.
Innovation Solution
A control apparatus that calculates rotor position estimation current amplitudes using only the squares of position estimation currents, eliminating the need for Fourier transforms and reducing computational and memory loads, thereby enabling efficient drive control without unnecessary cost increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fourier transform is used to calculate position estimation current amplitudes, then measurement precision is improved, but device complexity increases due to additional computational requirements and memory for sine/cosine functions
Solution Approach 1:
The patent extracts only the essential computational element needed for amplitude calculation - specifically using only the square of the position estimation current. This eliminates the need for complex Fourier transform operations and associated sine/cosine function memory storage, while still achieving accurate position estimation through the simplified calculation of current amplitude squared.
2Reliability
If random frequency is used for high-frequency voltage application, then reliability is improved by reducing noise, but measurement precision deteriorates due to difficulty in accurate position detection at zero or low speeds
Solution Approach 1:
The patent changes the frequency parameter from random to fixed, allowing the high-frequency voltage to be applied at a specific frequency. This enables accurate position detection at zero or low speeds while still maintaining noise reduction effectiveness through the fixed frequency approach combined with the simplified amplitude calculation method.
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 allows for accurate rotor position estimation and efficient drive control of electric rotating machines, reducing computational and memory requirements while avoiding the limitations of conventional methods.
Implementation Method 1
a high-frequency voltage having a frequency different from a drive frequency of the electric rotating machine is applied to the electric rotating machine, a high-frequency current flowing in the electric rotating machine along with the application of the high-frequency voltage is detected, and the position of the electric rotating machine is estimated by using the fact that the magnitude of the high-frequency current varies depending on the position of the electric rotating machine owing to the saliency of the electric rotating machine
Implementation Method 2
a method of estimating the position of the rotor of the electric rotating machine mainly from an inductive voltage of the electric rotating machine
Data Source
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AI summary
Control means (5) for outputting voltage instructions for drive control of an electric rotating machine (1) adds, by using adders (23u to 23w), position estimation voltage instructions for estimating the rotor position generated by a position estimation voltage generator (12), to drive voltage instructions, and outputs the resultant signals as voltage instructions. Position estimation means (4) include current extractors (6u to 6w) for extracting position estimation currents having the same frequency components as that of the position estimation voltage instructions, from electric rotating machine currents detected by a current detection means (2), a position estimation current amplitude calculation section (7) for calculating position estimation current amplitudes from the position estimation currents; and an estimation position calculation unit (8) for calculating an estimated position of the electric rotating machine (1), based on the position estimation current amplitudes. The position estimation current amplitude calculation section (7) calculates the position estimation current amplitudes, based on an autocorrelation obtained by squaring the position estimation currents.