Brushless Motor Controller Noise Reduction via Dual-Loop Segmentation
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Solution Overview
Problem
The existing controller for brushless motors faces limitations in shortening the cycle time of applied voltage calculations due to dependencies on calculation time, rotor position, and current detection, leading to noise issues, especially at high rotor speeds.
Innovation Solution
A separate determination loop for applied voltage updates is introduced, with a cycle time shorter than the calculations loop, allowing for reduced current variation and noise reduction by varying the applied voltage stepwise based on the latest and previous calculations, and using PWM control to update the duty ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the cycle time of applied voltage calculations is shortened to control motor current precisely, then motor current control precision is improved, but the cycle time is limited by calculation time, rotor position detection, and current detection, making it difficult to shorten further
Solution Approach 1:
The control system is divided into two separate loops: a calculation loop that computes applied voltage at a longer cycle time (e.g., 200 μsec), and an update loop that applies the voltage at a shorter cycle time (e.g., 50 μsec or less). This segmentation allows the calculation loop to operate at a manageable speed while the update loop provides finer control resolution, resolving the contradiction between calculation complexity and control precision.
2Manufacturing precision
If the cycle time of applied voltage calculations is shortened, then motor current control precision is improved, but noise with frequency nearly equal to the inverse of the cycle time is generated
Solution Approach 1:
By separating the calculation and update operations into different loops with different cycle times, the system achieves fine control resolution without requiring the calculation loop to operate at the same high speed. This reduces the noise-generating rapid switching while maintaining precise control through the high-frequency update loop.
3Manufacturing precision
If the cycle time of applied voltage calculations is shortened, then motor current control precision is improved, but the problem becomes more significant when the rotor rotates at high speed
Solution Approach 1:
The dual-loop architecture allows the update loop to operate independently at a high frequency that can be maintained even when the rotor rotates at high speed. This ensures that the control precision is maintained across all operating conditions without being constrained by the slower calculation loop, which handles the computationally intensive tasks at a lower frequency.
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 effectively reduces noise frequency and amplitude, ensuring the applied voltage remains close to the desired value, significantly minimizing abnormal noise generation.
Implementation Method 1
generate power for rotating the rotor by varying magnetic field generated by the coil
Data Source
AI summary
The controller for a brushless motor controls motor current by executing updates of applied voltage to a coil in accordance with rotational position of a rotor, the target current, and the actual current flowing through the coil. The updates of applied voltage to the coil are executed according to the results of calculations of applied voltage to the coil in accordance with the rotational position of the rotor, the target current, and the actual current flowing through the coil, in order to generate power for rotating the rotor by varying magnetic field generated by the coil. The cycle time of the updates of applied voltage is shorter than the cycle time of the calculations of applied voltage corresponding to the rotational position of the rotor.