Synchronous Motor Rotor Position Detection Using Single Sensor
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Solution Overview
Problem
Polyphase synchronous electric motors face challenges in synchronism maintenance during load changes, leading to potential destruction of components due to poor rotor position detection, especially with high costs associated with multiple logic-type position sensors in mass-produced small household appliances.
Innovation Solution
A method for controlling a three-phase synchronous electric motor using a single logic-type position sensor to align the rotor's magnetic polarization with a predetermined stator alignment position, leveraging theoretical models to determine alignment times and oscillation damping characteristics, allowing for precise position and speed estimation to adjust switching instants and ensure optimal torque application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple logic-type position sensors are used to detect rotor position, then position detection precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent segments the position detection function into two parts: a single logic-type sensor provides basic position information, while a theoretical model provides complementary position and speed estimation. This segmentation allows the system to achieve comprehensive position detection capability without using multiple physical sensors, thereby reducing manufacturing cost while maintaining detection precision.
Solution Approach 2:
The patent introduces a theoretical model as an intermediary between the single position sensor and the control system. This model processes the sensor signal and generates additional position and speed information that would otherwise require multiple sensors to obtain directly. The intermediary model enables the system to achieve multi-sensor level precision using only a single physical sensor.
2Ease of manufacture
If a single logic-type position sensor is used to reduce cost, then manufacturing cost is reduced, but position detection precision deteriorates
Solution Approach 1:
The patent replaces the need for multiple physical sensors with a combination of a single sensor and a computational theoretical model. The model mathematically estimates position and speed parameters that would otherwise require additional physical sensors to measure directly. This substitution of mechanical/sensor-based measurement with computational estimation achieves the same precision goals at lower manufacturing cost.
Solution Approach 2:
The patent creates a virtual copy of the multi-sensor detection capability through a theoretical model that replicates the information output of multiple sensors. The model generates estimated position and speed signals that mirror what multiple physical sensors would provide, allowing the control system to operate as if it had multiple sensors while using only a single physical sensor.
3Speed
If switching frequency is increased during motor operation, then motor speed is improved, but risk of losing synchronism increases
Solution Approach 1:
The patent implements continuous feedback by using the theoretical model to constantly estimate rotor position and speed based on the single sensor input. This feedback mechanism allows the control system to monitor the motor's operational state in real-time and adjust switching frequency dynamically. When the motor approaches synchronism loss conditions, the feedback enables corrective action before failure occurs, allowing higher operating speeds while maintaining reliability.
Solution Approach 2:
The patent performs preliminary action by using the theoretical model to predict future rotor position and speed states based on current sensor data. This predictive capability allows the control system to prepare switching commands in advance, ensuring that switching frequency can be increased to achieve higher speeds while maintaining synchronism. The model anticipates synchronism loss conditions and enables preventive control adjustments.
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 reduces motor costs and size, enhances precision in position detection, and enables high-speed operation with optimal torque control, minimizing stress on motor components during startup and maintaining performance comparable to motors with multiple sensors.
Implementation Method 1
use position sensors of the logic type, in particular Hall effect or optical, to inform the controller of a relative position of the rotor with respect to the stator
Implementation Method 2
a stator comprising teeth around which are wound coils defining electrical phases and magnetic poles of the stator
Implementation Method 3
the rotor rotates at the same angular velocity as the stator polarization direction
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention relates to a method for controlling the starting of a three-phase synchronous electric motor (1) without a collector, comprising a step of aligning the direction and sense of the magnetic polarization of the rotor (5) with an alignment position (PA) defined by the direction and sense of the polarization of the stator (2) determined according to the information read from the position sensor concerning the sense of the magnetic polarization of the rotor, said alignment step being carried out for a period after which the amplitude of the oscillations and/or the speed of the rotor (5) is less than a predetermined threshold.