Motor Control Device Rotor Position Determination
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Solution Overview
Problem
Conventional motor control devices for synchronous motors face instability and uncontrollability due to erroneous rotor position determination, particularly in the flux-weakening-control region, where high current peak values lead to unstable current phase measurement.
Innovation Solution
A motor control device that selects between two rotor position determining units based on both current peak value and current phase, using specific calculation equations and data tables to ensure accurate rotor position determination in both normal and flux-weakening-control regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second rotor position determining unit is selected based only on current peak value threshold in flux-weakening-control region, then rotor position can be determined in high current conditions, but erroneous rotor position may be obtained due to unstable current phase measurement
Solution Approach 1:
The patent changes the selection parameters from only current peak value threshold to a combination of current peak value and current phase. By adding current phase as an additional parameter for determining which rotor position determining unit to select, the system avoids erroneous measurements in high current regions where phase instability occurs.
Solution Approach 2:
The patent implements a feedback mechanism where the selecting unit continuously monitors both current peak value and current phase to dynamically select the appropriate rotor position determining unit. This feedback loop ensures that when current phase becomes unstable (indicating potential measurement errors), the system switches to the more reliable first determining unit.
2Measurement precision
If the first rotor position determining unit is used in normal-control region, then accurate rotor position can be obtained, but the system cannot handle high current peak values in flux-weakening-control region
Solution Approach 1:
The patent makes the rotor position determination system dynamic by allowing switching between two different determining units based on operating conditions. The selecting unit dynamically chooses between the first determining unit (for normal-control region with accurate phase measurement) and the second determining unit (for flux-weakening-control region with high current), enabling the system to adapt to varying operational requirements.
Solution Approach 2:
The patent creates a universal rotor position determination system that can handle both normal-control and flux-weakening-control regions. By designing two complementary determining units with different characteristics and selecting the appropriate one based on operating conditions, the system achieves multi-functionality across the entire operating range.
3Reliability
If dual rotor position determining units are implemented with switching logic, then accurate rotor position can be maintained across all regions, but device complexity increases
Solution Approach 1:
The patent segments the rotor position determination function into two specialized determining units: the first unit optimized for normal-control region with accurate current phase measurement, and the second unit optimized for flux-weakening-control region. This segmentation allows each unit to be simpler and more reliable in its specific operating range, while the selecting unit manages the switching between them.
Data Source
AI summary
Provided is a motor control device having a function for determining a rotor position of a synchronous motor, without use of a sensor, the device prevents obtaining an erroneous rotor position, to enable stable control of the synchronous motor based on the rotor position in both the normal-control region and the flux-weakening-control region. The motor control device 1 includes: a first rotor position determining unit 19 that determines a rotor position of the synchronous motor 2 based on a current electrical angle, and a first current phase obtained from a current peak value and a difference between an induced voltage electrical angle and a current electrical angle; a second rotor position determining unit 20 that determines the rotor position of the synchronous motor 2 based on the current electrical angle, and a second current phase obtained from a flux linkage and the current peak value; and a selecting unit 21 that selects the first rotor position determining unit 19 or the second rotor position determining unit 20, based on the current peak value, and the first current phase or the second current phase.