Sensorless Rotor Detection via Flux Convergence Monitoring
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Solution Overview
Problem
Existing sensorless control methods for permanent magnet motors become unreliable due to flux estimation issues, leading to motor control problems such as tripping or oscillation, especially when the estimated flux diverges from the actual flux or during start-up and power disruptions.
Innovation Solution
Implementing methods to estimate and monitor the convergence of estimated flux towards actual flux, allowing immediate control usage once convergence is confirmed, and discontinuing control when divergence occurs, along with monitoring power levels to resume control after disruptions, thereby ensuring reliable motor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control is used to eliminate position sensors, then device complexity is reduced, but reliability deteriorates due to flux estimation becoming unreliable over time
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors the reliability of flux estimates and dynamically adjusts control strategy. When flux estimation becomes unreliable (indicated by divergence detection), the system transitions from sensorless control to sensor-based control, ensuring continuous reliable operation while maintaining the benefits of sensorless control during normal operation.
2Loss of time
If flux estimation is used immediately after start-up, then time in open-loop control is reduced, but measurement precision deteriorates because flux estimates are not sufficiently accurate
Solution Approach 1:
The patent performs preliminary flux estimation during the start-up phase and uses this initial estimate to determine when the rotor has been successfully found. This preliminary action allows the system to transition to closed-loop control earlier than traditional methods, reducing the time spent in open-loop control while ensuring accuracy by verifying convergence before full control engagement.
3Ease of operation
If traditional sensorless control is maintained during power disruptions, then ease of operation is maintained, but reliability deteriorates due to rotor position and speed estimate becoming unreliable
Solution Approach 1:
The patent implements a dynamic control system that automatically adapts to changing operating conditions, including power disruptions. The system monitors flux convergence in real-time and dynamically switches between control modes (sensorless during normal operation, sensor-based during disruptions), maintaining both ease of operation and reliability without requiring manual intervention.
Data Source
AI summary
Various methods of detecting a found rotor, a lost rotor, a locked rotor and a caught rotor after a power disruption using flux estimates are disclosed. Also disclosed are permanent magnet motor controllers and assemblies suitable for performing one or more of these methods.