Adaptive Stepper Motor Blanking Period Control
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Solution Overview
Problem
Current stepper motor current regulation methods suffer from overshoot and zero-crossing distortion due to fixed blanking periods, which limit the precision of current regulation and micro-stepping resolution, especially at higher current levels and torque requirements.
Innovation Solution
Adaptive blanking period control is implemented, where the blanking period is proportional to the selected current regulation set-point, allowing earlier detection of current sense feedback and reducing overshoot, thereby improving current regulation accuracy and reducing zero-crossing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed blanking period is used in current regulation, then the system is simple to implement, but overshoot and zero-crossing distortion occur reducing current regulation precision
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed blanking period to an adaptive blanking period that varies based on the absolute value of the current regulation set-point. The blanking period is dynamically adjusted to be proportional to the set-point current level, allowing the system to optimize performance across different operating conditions while maintaining implementation feasibility through a straightforward proportional relationship.
Solution Approach 2:
The patent implements parameter changes by modifying the blanking period parameter based on the current regulation set-point. The blanking period is changed from a constant value to a variable value that scales with the set-point current, thereby reducing overshoot and zero-crossing distortion at higher current levels while maintaining appropriate blanking at lower levels.
2Manufacturing precision
If a fixed blanking period is used, then the control logic is simple, but micro-stepping resolution is limited due to overshoot
Solution Approach 1:
The adaptive blanking period dynamically adjusts based on the current set-point level, allowing the system to maintain precise current regulation across the full range of micro-stepping positions. This dynamic adjustment enables finer micro-stepping resolution by reducing overshoot effects that would otherwise limit positioning precision.
3Measurement precision
If the blanking period is shortened to reduce overshoot, then current regulation accuracy improves, but noise from parasitic RLC tank circuit increases
Solution Approach 1:
The patent resolves this contradiction by making the blanking period proportional to the set-point current rather than using a fixed short period. At higher current levels where overshoot is more problematic, the proportional relationship allows for longer blanking periods that filter noise. At lower current levels, the blanking period naturally shortens, maintaining detection accuracy while avoiding excessive noise filtering that would delay current detection.
Data Source
AI summary
Stepper motor winding current regulation methods and apparatus adapt a maximum blanking period to generate an adapted blanking period that is proportional to a currently-selected current regulation set-point. Sensed winding current feedback is ignored at a current regulation controller during the adapted blanking period or during a minimum blanking period, whichever longer, to avoid attempting to track noise imposed upon a sensed winding current feedback signal at an initiation of rapid current changes di/dt. Doing so may decrease ripple in the motor winding current waveform and reduce zero-crossing distortion by decreasing overshoot of the current regulation set-point by the sensed winding current.