Motor Control Filter Circuit for Harmonic Noise Reduction
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Solution Overview
Problem
Existing motor control systems face instability due to high-frequency harmonic components in the drive current, which can lead to uncontrollable motor states and increased costs when attempting to filter these components with fixed filter orders that may not adapt to changing rotation speeds or motor types.
Innovation Solution
A motor control apparatus that includes an obtaining unit for current values, a filter circuit to reduce harmonic components, and a phase determiner to control the drive current, where the filter circuit processes a reduced number of current values to minimize harmonic noise without increasing filter order or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the filter order is increased to reduce harmonic components at lower frequencies, then the harmonic noise reduction capability is improved, but the memory usage and cost increase
Solution Approach 1:
The patent applies dynamics by making the filter order variable rather than fixed. The control device dynamically adjusts the filter order based on the detected rotation speed of the rotor. At higher rotation speeds, a lower filter order suffices, while at lower rotation speeds, the filter order is increased to maintain effective harmonic noise reduction. This dynamic adaptation eliminates the need for consistently high filter orders, thereby reducing memory usage and cost while maintaining effective harmonic noise reduction across varying operating conditions
Solution Approach 2:
The patent changes the parameter of filter order based on rotation speed. By detecting the rotation speed and selecting an appropriate filter order from multiple predetermined values, the system optimizes the balance between harmonic noise reduction and resource consumption. This parameter change strategy allows the system to use minimal filter order (and thus minimal memory) when harmonic noise is not problematic at high speeds, while only increasing filter order when actually needed at lower speeds
2Device complexity
If a fixed filter order is used to reduce harmonic components, then the device complexity is reduced, but the motor control stability deteriorates when rotation speed changes
Solution Approach 1:
The system transitions from a static filter configuration to a dynamic one where the filter order automatically adapts to rotation speed changes. The control device detects the current rotation speed and selects the appropriate filter order from predetermined values, ensuring optimal harmonic noise reduction across the entire operating range. This dynamic adjustment maintains motor control stability without requiring complex manual reconfiguration or over-engineering the filter for worst-case scenarios
Solution Approach 2:
The system implements feedback by continuously monitoring the rotation speed and using this information to adjust the filter order. The control device detects the actual rotation speed and selects the filter order that is appropriate for the current operating condition. This closed-loop approach ensures that the filter configuration always matches the actual operating state, maintaining motor control stability while avoiding unnecessary complexity
3Object-affected harmful factors
If the filter order is set for the lowest rotation speed, then the harmonic noise reduction is improved at low speeds, but the productivity decreases due to increased processing time
Solution Approach 1:
The system dynamically adjusts the filter order based on real-time rotation speed detection. At high rotation speeds where harmonic noise is less problematic, a lower filter order is used, enabling faster control processing and maintaining high productivity. At lower rotation speeds where harmonic noise becomes more significant, the filter order is increased to ensure adequate noise reduction. This dynamic adaptation optimizes the trade-off between noise reduction and processing speed for each operating condition
Solution Approach 2:
The filter order parameter is changed based on rotation speed conditions. By selecting from multiple predetermined filter order values, the system uses the minimal necessary filter order for each operating condition. This prevents unnecessary computational overhead at high speeds while ensuring adequate harmonic noise reduction at low speeds, thereby maintaining overall system productivity
Data Source
AI summary
To control a winding drive current of a motor based on a command phase representing a target phase of a rotor of the motor, a motor control apparatus includes a filter circuit, a phase determiner, and a controller. A current value of the drive current flowing through the winding is obtained at a predetermined period. The filter circuit reduces a harmonic component in a fundamental frequency of the drive current included in a signal indicated by the obtained current value. The phase determiner determines a rotation phase of the rotor based on a filter processed signal. The controller controls the winding drive current to reduce a deviation between the command phase and the determined rotation phase. The filter circuit reduces a harmonic component from a signal indicated by current values of which a number is not greater than a number of the current values obtained at the predetermined period.