Brushless DC Motor SFOC Phase Current Detection
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Solution Overview
Problem
Existing control methods for brushless DC motors with a single current measuring device face complexity in determining phase currents due to the need for specific time intervals during clock cycles, which are not always met, especially in critical operating states.
Innovation Solution
The control method subdivides clock cycles into equal partial cycles with symmetrical and coherent partial switch-on periods, allowing for fixed time intervals for current detection, simplifying the determination of phase currents and enabling reliable operation without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single current measuring device is used to detect phase currents, then cost is reduced, but the control method becomes complex and reliability decreases in critical operating states
Solution Approach 1:
The clock cycle is segmented into multiple partial cycles, and each partial cycle is further divided into specific time intervals (first, second, third time intervals) for detecting different phase currents. This segmentation allows a single current measuring device to capture all necessary phase current information by measuring at appropriate moments within each interval, eliminating the need for multiple dedicated measuring devices while ensuring reliable detection in all operating states.
2Ease of operation
If partial switch-on periods are made symmetrical and coherent, then ease of operation improves, but the flexibility in handling critical operating states decreases
Solution Approach 1:
The control method dynamically adjusts the duration of partial switch-on periods based on the operating state. In normal operating states, symmetrical and coherent partial switch-on periods are used for simplified control. In critical operating states, the system automatically adapts by adjusting the timing and duration of switch-on periods to ensure sufficient measurement intervals are available, thus maintaining both ease of operation and adaptability.
3Measurement precision
If fixed time intervals are used for current detection, then measurement precision improves, but the ability to adapt to varying operating conditions decreases
Solution Approach 1:
The system employs periodic current detection at fixed time intervals within each partial cycle, ensuring consistent measurement precision. The periodic structure is designed so that measurements are taken at predetermined points (first, second, third time intervals) that are optimally positioned to capture accurate phase current values. This periodic approach maintains measurement precision while the overall timing structure adapts to different operating conditions through dynamic adjustment of partial cycle parameters.
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 simplifies the control method implementation, ensuring accurate phase current detection and motor control, even in critical states, by coordinating partial activation periods to meet the necessary time intervals for current measurement.
Implementation Method 1
a single current detection device 5 which detects the total current I
Implementation Method 2
the rotary position is derived from a detection of the magnetic fluxes
Data Source
Figure 1~2
Figure 3~4
AI summary
The method involves determining target voltages for three phases using rotational position of a rotor of direct current (DC) motor. A setting device is controlled according to the determination result, such that each phase is connected to a supply voltage line corresponding to the respective reference voltage within a respective clock cycle (T). The divisional switching periods (T1'-T3',T1''-T3'') for each phase are determined such that current detection for each phase is enabled within fixed time intervals (Z1',Z2',Z1'',Z2'') of sub-cycles (T',T''). Independent claims are included for the following: (1) control device for brushless DC motor; and (2) brushless DC motor.