Sub-Commutated Sinusoidal Motor Control for Sub-Degree Pointing
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Solution Overview
Problem
Existing technologies face challenges in achieving sub-degree pointing accuracy with direct current (DC) motors, particularly with asymmetric direct-drive brushless DC motors, as they struggle with torque ripple and precise torque modulation.
Innovation Solution
The implementation of a bi-stable torque controller, combined with a proportional-integral (PI) velocity controller, a proportional-integral-differential (PID) position controller, and sinusoidal zero-velocity table mapping, allows for modulated torque values and precise control of brushless DC motors, enabling sub-degree pointing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional brushless DC motor controllers are used, then the system is simple to implement, but sub-degree pointing accuracy cannot be achieved due to torque ripple and limited commutation precision
Solution Approach 1:
The controller segments the electrical commutation cycle into multiple sub-commutation intervals, enabling precise torque control at each segment. This allows the system to achieve sub-degree pointing accuracy by controlling torque delivery in fine-grained temporal segments rather than as a continuous signal.
Solution Approach 2:
The controller dynamically adjusts torque commands during each electrical commutation cycle based on real-time motor state and desired trajectory. This dynamic control enables the system to compensate for torque ripple and achieve high pointing accuracy while maintaining adaptability to changing operating conditions.
2Force
If standard commutation methods are used, then the control system is straightforward, but torque ripple prevents precise torque modulation
Solution Approach 1:
The controller implements periodic sub-commutation cycles within each electrical commutation period, creating a structured sequence of torque adjustments. This periodic action pattern enables systematic torque ripple compensation and precise torque modulation while maintaining a predictable control rhythm that simplifies implementation.
Solution Approach 2:
The controller uses feedback from motor position, velocity, and current sensors to continuously adjust torque commands during sub-commutation intervals. This feedback mechanism enables precise torque modulation by comparing actual motor state with desired state and making real-time corrections to compensate for torque ripple.
3Measurement precision
If gears are used to achieve precision (as in servo controllers), then pointing accuracy can be achieved, but the system loses direct-drive simplicity and adds mechanical complexity
Solution Approach 1:
The controller replaces mechanical gearing mechanisms with electronic sub-commutation control to achieve precision. By using multiple control cycles within each electrical commutation period, the system achieves gear-like precision through electronic modulation rather than mechanical reduction, maintaining direct-drive simplicity while achieving high pointing accuracy.
Data Source
AI summary
An electric motor controller system for modulating requested motor torque via oscillating the instantaneous torque, including a bi-stable torque controller; a proportional-integral (PI) velocity controller a proportional-integral-differential (PID) position controller; and sinusoidal zero-velocity table mapping.