Direct-Drive BLDC Torque Control for Sub-Degree Pointing
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Solution Overview
Problem
Existing control systems for direct current (DC) motors, particularly brushless DC motors, face challenges in achieving sub-degree pointing accuracy without mechanical gears and extending micro-stepping commutation methods to direct drive motors.
Innovation Solution
A bi-stable torque controller, combined with a proportional-integral (PI) velocity controller, proportional-integral-differential (PID) position controller, and sinusoidal zero-velocity table mapping, is used to modulate torque and achieve sub-degree accuracy in brushless DC motors by oscillating instantaneous torque and reducing torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If servo controllers use gears to achieve precision, then pointing accuracy is improved, but device complexity and mechanical reliability are worsened
Solution Approach 1:
The patent replaces mechanical gears with a direct-drive brushless DC motor configuration, eliminating mechanical transmission components. The control system achieves sub-degree accuracy through electronic commutation and control algorithms rather than mechanical reduction gears, thereby improving reliability while maintaining precision.
Solution Approach 2:
The patent employs advanced control parameters including bi-stable torque control, PI velocity control, and PID position control to achieve high precision without mechanical gears. By dynamically adjusting control parameters and using sinusoidal zero-velocity table mapping, the system attains sub-degree pointing accuracy through software-based precision rather than mechanical means.
2Measurement precision
If micro-stepping commutation is used with stepper motors, then precision is improved, but adaptability to direct drive brushless DC motors is worsened
Solution Approach 1:
The patent develops a control methodology that is universally applicable to direct-drive brushless DC motors, extending precision control capabilities beyond stepper motors. The bi-stable torque controller and sinusoidal commutation approach can be applied to various direct drive BLDC motor configurations, making the precision control technique versatile and adaptable.
Solution Approach 2:
The patent adapts micro-stepping-like precision control to direct-drive brushless DC motors by replacing the stepper motor's inherent micro-stepping mechanism with electronic torque modulation. Through bi-stable torque control and oscillating instantaneous torque, the system achieves equivalent precision effects in a different motor topology that is suitable for direct-drive applications.
3Measurement precision
If sub-degree accuracy is achieved through multiple electrical commutation cycles, then pointing accuracy is improved, but response time and productivity are worsened
Solution Approach 1:
The patent uses sinusoidal zero-velocity table mapping to pre-calculate and store optimal torque values for different positions and velocities. This preliminary preparation allows the controller to achieve sub-degree accuracy without requiring multiple iterative commutation cycles, as the correct torque values are already determined and ready for immediate application.
Solution Approach 2:
The patent implements dynamic torque modulation through bi-stable control that can rapidly switch between torque states. This dynamic approach allows the system to achieve high precision in a single or few commutation cycles by adaptively adjusting torque in real-time based on position feedback, rather than requiring multiple fixed commutation cycles.
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 enables sub-degree pointing accuracy in brushless DC motors by minimizing torque changes and maintaining a consistent torque curve across positions, enhancing reliability and efficiency, and is applicable in various applications including unmanned aerial vehicle (UAV) sensor gimbals.
Implementation Method 1
a sinusoidal drive having at least three phases, where the instantaneous torque is based on a sinusoidal reference
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.