Sensorless Induction Motor Stop Timing via Induced Current Deviation
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Solution Overview
Problem
Sensorless induction motor systems face response delays and overcurrent issues due to incorrect rotor position estimation, particularly at low speeds, leading to control failures and increased inverter loss in integrated air compressors for fuel cell vehicles.
Innovation Solution
A controller sets a stop waiting time based on the rotor's deceleration gradient and applies pulse voltage multiple times to determine when the rotor has stopped by calculating the minimum deviation value of induced current, ensuring accurate stop time and position identification without sensors, thereby reducing inverter loss and improving durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If sensorless control method is used to estimate rotor position without Hall sensor, then package size and weight are reduced, but estimation performance deteriorates at low speed causing speed control failure
Solution Approach 1:
The system applies preliminary actions by injecting voltage vectors before actual operation and using instantaneous deceleration gradient calculation during deceleration phase to predict stop time. This preliminary estimation of rotor position and stop timing enables sensorless control to achieve accuracy comparable to sensor-based systems, resolving the low-speed estimation performance issue while maintaining the weight reduction benefit of eliminating Hall sensors.
2Speed
If stop time is set to be short to improve response speed, then acceleration delay is reduced, but incorrect vector values cause incorrect rotor position identification and control failure
Solution Approach 1:
The system employs feedback mechanisms by continuously monitoring instantaneous deceleration gradient and comparing predicted stop time with actual stop detection. The controller adjusts the stop waiting time based on real-time deceleration characteristics, ensuring that pulse voltage is applied at the optimal moment when the rotor has truly stopped. This feedback loop maintains high response speed while preventing control failure due to premature or delayed stop detection.
Solution Approach 2:
The system dynamically adapts the stop waiting time based on instantaneous deceleration gradient rather than using a fixed time value. By calculating the deceleration gradient in real-time during the deceleration phase, the system adjusts the predicted stop time to match actual operating conditions, enabling reliable rotor position identification across varying load and speed conditions while maintaining fast response.
3Measurement precision
If stop time is set to be long to ensure accurate stop detection, then rotor position identification accuracy is improved, but acceleration delay increases when restarted
Solution Approach 1:
The system performs preliminary calculation of instantaneous deceleration gradient during the deceleration phase to predict the exact stop time in advance. This allows the controller to set an optimized stop waiting time that is long enough to ensure accurate stop detection but short enough to minimize acceleration delay upon restart, eliminating the need for excessively long fixed waiting periods.
Solution Approach 2:
The system changes the stop waiting time parameter dynamically based on instantaneous deceleration gradient rather than using a conservative fixed value. By adjusting this parameter according to real-time deceleration characteristics, the system achieves accurate stop detection with minimal waiting time, preventing both premature restart and excessive acceleration delay.
4Measurement precision
If pulse voltage is applied multiple times to determine stop completion, then rotor stop determination accuracy is improved, but inverter loss increases and durability deteriorates
Solution Approach 1:
The system performs preliminary estimation of stop completion time using instantaneous deceleration gradient calculation during the deceleration phase. This allows the controller to apply pulse voltage exactly once at the predicted stop time rather than repeatedly applying it multiple times. The preliminary time prediction ensures accurate stop detection with a single pulse voltage application, significantly reducing inverter loss and improving durability while maintaining high detection accuracy.
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 method accurately determines the rotor's stop completion time and position, preventing response delays and control failures, while minimizing inverter loss and enhancing the reliability of rotor stop determination in sensorless induction motor systems.
Implementation Method 1
a controller configured to control operation of the motor by controlling a voltage applied to each phase of the stator, to set a stop waiting time predicted to be necessary for the rotor to stop, to apply a pulse voltage to each phase of the stator a plurality of times
Data Source
AI summary
A sensorless induction motor system and a control method thereof includes a motor including a stator including windings forming a plurality of phases and a rotor including a permanent magnet, and a controller configured to control operation of the motor by controlling a voltage applied to each phase of the stator, to set a stop waiting time predicted to be necessary for the rotor to stop when the motor is controlled to stop, to apply a pulse voltage to each phase of the stator a plurality of times after the stop waiting time, and to conclude that the rotor has stopped when a minimum deviation value of an induced current is equal to or greater than a reference value.