Sensorless Induction Motor Rotor Stop Detection Using Pulse Probing
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Solution Overview
Problem
Sensorless induction motor systems face challenges in preventing response delay and overcurrent generation due to incorrect position estimation, especially at low velocities and varying stopping times.
Innovation Solution
A sensorless induction motor system with a controller that sets a stop waiting time based on the rotor's rotational velocity and instantaneous deceleration slope, applies a pulse voltage to the stator after the stop waiting time, and determines the rotor's stop position by observing identical rotor position vectors with the largest induced current deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the stopping time is set to be short, then productivity is improved, but measurement precision deteriorates due to incorrect identification of rotor position
Solution Approach 1:
The controller performs preliminary actions by applying pulse voltages to the stator windings before officially determining the rotor has stopped. This preliminary voltage application stimulates the rotor windings to generate currents that reveal position information, allowing the system to accurately detect stop completion and position even during very short stopping intervals, thus resolving the contradiction between fast stopping and accurate position identification.
Solution Approach 2:
The system uses feedback by continuously monitoring the currents generated in rotor windings in response to applied pulse voltages. By detecting when the rotor position vectors stabilize and match across consecutive pulse applications, the system obtains real-time feedback on rotor stop status and position, enabling accurate measurement even during rapid deceleration and short stopping periods.
2Measurement precision
If the stopping time is set to be excessively long, then measurement precision is improved, but productivity deteriorates due to acceleration delay
Solution Approach 1:
The controller applies pulse voltages to the stator windings during the deceleration phase before the rotor comes to a complete stop. This preliminary action captures position information while the rotor is still moving at low speeds, eliminating the need to wait for complete stoppage before measurement, thus reducing overall stopping time while maintaining high measurement precision.
Solution Approach 2:
The system skips the traditional approach of waiting for complete stoppage before position measurement. By rushing through the measurement process during the final deceleration phase using pulse voltage applications, the system obtains accurate position data before the rotor fully stops, thereby reducing idle time and improving productivity without sacrificing measurement accuracy.
3Device complexity
If sensorless control is used to reduce package size, then device complexity is reduced, but measurement precision deteriorates at low velocity
Solution Approach 1:
The patent replaces mechanical sensors (Hall sensors) with an electrical field-based measurement system. By applying pulse voltages to stator windings and measuring the resulting currents in rotor windings, the system substitutes mechanical position detection with electromagnetic induction-based detection, maintaining sensorless operation while achieving high precision even at low velocities where traditional sensorless methods fail.
Solution Approach 2:
The system changes the operating parameters by applying high-frequency pulse voltages to the stator windings instead of using continuous operation. This parameter change excites the rotor windings to generate measurable currents that reveal precise position information, overcoming the limitation of traditional sensorless control that loses accuracy at low velocities without requiring additional sensors.
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 identification of the rotor's stop completion time and position, preventing response delay and overcurrent issues, and ensuring reliable control of the motor without sensors.
Implementation Method 1
applying a pulse voltage to each phase of the stator a plurality of times after the stop waiting time
Implementation Method 2
a motor including a stator having windings forming a plurality of phases and a rotor having a permanent magnet
Data Source
AI summary
Disclosed are a sensorless induction motor system including a controller configured to control operation of a motor by controlling a voltage applied to each phase of a stator, to set a stop waiting time expected to be required for the rotor to stop during stop control of the motor, to apply a pulse voltage to each phase of the stator a plurality of times after the stop waiting time, and to determine that the rotor is stopped when rotor position vectors having largest induced current deviations are observed as the same rotor position vector, and a control method thereof.