Sensorless Rotor Synchronization via Countervoltage Phase Offset
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Solution Overview
Problem
Sensorless brushless DC motors face challenges in determining accurate position information during start-up, especially below a threshold rotation speed, leading to inefficient commutation and potential motor stalling due to lack of synchronization between the rotor and stator fields.
Innovation Solution
A method and device for synchronizing the rotation speed of a permanently excited rotor with the rotation field of a sensorless commutated stator by determining the phase position of the rotation field and induced countervoltage, and adjusting the amplitude of the rotation field components based on the phase offset to achieve synchronization, thereby ensuring continuous force flow and compensating for load torque fluctuations during run-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless commutation is used to simplify the motor structure, then device complexity is reduced, but measurement precision of rotor position deteriorates at low speeds
Solution Approach 1:
The patent introduces an intermediary synchronization mechanism that uses the countervoltage signal as a mediator between the rotor and stator fields. By detecting the phase position of the countervoltage and using it to synchronize the rotation field, the system obtains indirect position information without requiring direct sensors, thus maintaining structural simplicity while improving measurement precision at low speeds.
Solution Approach 2:
The patent implements a feedback mechanism where the phase position of the countervoltage is continuously monitored and used to adjust the rotation field synchronization. The controller compares the desired phase position with the actual phase position derived from countervoltage and adjusts the rotation field accordingly, enabling accurate position tracking even at low speeds without adding physical sensors.
2Ease of operation
If blind start-up is used to simplify control, then ease of operation is improved, but reliability of motor operation deteriorates due to potential stalling
Solution Approach 1:
The patent applies preliminary action by synchronizing the rotation field with the rotor before full power is applied during start-up. The controller initially operates in a synchronization mode where the rotation field is aligned with the rotor position derived from countervoltage, ensuring the rotor is properly positioned and the magnetic fields are synchronized before transitioning to normal commutation mode, thereby preventing stalling while maintaining simple control.
3Speed
If rotation field amplitude is increased to accelerate rotor, then speed is improved, but loss of energy increases
Solution Approach 1:
The patent implements dynamic control of the rotation field amplitude based on the synchronization state and load conditions. The controller adjusts the amplitude of the rotation field components dynamically - using higher amplitudes when synchronization is needed for acceleration, and reducing amplitudes when synchronization is maintained, thereby optimizing the balance between speed performance and energy consumption.
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 enables smooth transition from standstill to desired rotation speed, allowing for accurate synchronization of the rotor and stator fields, even at low speeds, and effectively compensates for load torque fluctuations, ensuring efficient motor operation and preventing stalling.
Implementation Method 1
an angle position of the rotor can only be determined if a sufficiently high magnitude of countervoltage is induced into the coils of the stator by the magnetic field of the rotor on the basis of a rotation of the rotor
Data Source
AI summary
A method for synchronizing a rotation speed of a permanently excited rotor of an electric motor with a frequency of a rotation field of a sensorless commutated stator of the electric motor during a run-up procedure of the electric motor includes determining a phase position of the rotation field and a phase position of a countervoltage that is induced by the rotor in the stator in order to obtain a phase offset between the rotation field and the countervoltage. The method further includes adjusting a prevailing amplitude of one component of the rotation field using the phase offset to synchronize the rotation speed with the frequency. The amplitude of the component is increased if the rotor is lagging behind the rotation field or the amplitude of the component is reduced if the rotor is running ahead of the rotation field.