Sensorless Rotor Lock Detection via PI Torque Saturation
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Solution Overview
Problem
Existing electric motor control systems face challenges in accurately detecting rotor lock conditions without position or velocity sensors, as conventional methods rely on inaccurate estimates of angular velocity, leading to potential motor damage from sustained obstructions.
Innovation Solution
A controller device employs proportional-integral (PI) circuitry to generate a reference torque signal based on the error between estimated and target angular velocities, determining rotor lock by monitoring the saturation of this signal for a threshold time, allowing for detection without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless field-oriented control is used to estimate angular velocity, then the device complexity is reduced, but the measurement precision of angular velocity deteriorates under rotor lock conditions
Solution Approach 1:
The patent introduces a reference torque signal as an intermediary indicator to detect rotor lock conditions. Instead of directly measuring angular velocity accuracy, the system monitors the reference torque signal generated by PI circuitry, which saturates when rotor lock occurs. This intermediary signal allows detection of measurement precision deterioration without adding sensors.
2Measurement precision
If additional sensors are added to improve rotor lock detection accuracy, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent makes the existing control system self-diagnostic by utilizing the reference torque signal that already exists in the control loop. The system monitors its own internal signal (reference torque) to detect rotor lock conditions, eliminating the need for external sensors or additional measurement devices.
Solution Approach 2:
The reference torque signal serves multiple functions: it is used for normal motor control and simultaneously serves as an indicator for rotor lock detection. This multi-functionality allows the system to achieve both control and diagnostic capabilities without adding separate dedicated components.
3Reliability
If the reference torque signal is monitored continuously, then the reliability of rotor lock detection improves, but the use of energy increases
Solution Approach 1:
The patent applies a threshold-based detection approach where the reference torque signal is monitored continuously but rotor lock is only declared when the signal exceeds a saturation threshold for a predetermined time period. This partial action approach ensures reliable detection while avoiding excessive energy consumption from continuous processing and false alarms.
Data Source
AI summary
In some examples, a controller device is configured to generate control signals for a power-conversion circuit that drives an electric motor including a rotor. In some examples, the controller device includes subtraction circuitry configured to generate an error signal based on a difference between an estimated angular velocity of the rotor and a target angular velocity for the rotor. In some examples, the controller device further includes proportional-integral (PI) circuitry configured to generate a reference torque signal based on the error signal. In some examples, the controller device also includes processing circuitry configured to determine that the rotor is locked based on detecting that the reference torque signal includes a saturated amplitude for at least a threshold time.