Brushless Slotless DC Motor Torque Ripple Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional stepper motors used in fluidic pumps, such as peristaltic pumps, are position-controlled and prone to vibration, resonance, and torque ripple, which are not optimal for controlling fluid pressure and vacuum in ophthalmic surgical systems, where precise force and torque control are necessary.
Innovation Solution
The use of brushless slotless direct current (BSDC) motors with digital sine-wave commutation and associated control circuitry, including sine-cosine encoders and torque sensing, to provide torque-controlled operation and minimize vibration and torque ripple, enabling precise control of fluidic pumps in ophthalmic surgical systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stepper motors are used to control fluidic pumps, then position control is achieved, but vibration, resonance, and torque ripple occur which are not optimal for precise fluid pressure and vacuum control
Solution Approach 1:
The patent replaces traditional stepper motors with brushless slotless direct current (BSDC) motors that use electromagnetic fields instead of mechanical commutation. The BSDC motor eliminates brushes and commutators, using electronic commutation with sine-wave currents to drive the motor, thereby eliminating mechanical vibration and torque ripple while maintaining precise position and torque control for fluidic pump operation
Solution Approach 2:
The patent changes the electrical parameters by using sinusoidal current waveforms instead of stepped currents, and implements electronic commutation with precise control of current magnitude and phase. This allows continuous torque control without the discrete steps that cause torque ripple in stepper motors, achieving smooth operation with minimal vibration
2Power
If traditional brushless DC (BLDC) motors are used, then torque control is improved, but thermal efficiency and eddy current losses are not optimized
Solution Approach 1:
The patent changes the motor construction parameters by eliminating the slot structure and using a slotless design with distributed magnets. This configuration reduces eddy current losses by eliminating the concentrated magnetic fields in slots that cause hysteresis and eddy current heating in traditional BLDC motors, while maintaining effective torque control through proper magnet distribution
Solution Approach 2:
The patent employs composite material structures in the motor construction, using specific magnetic materials and conductor arrangements that minimize energy losses. The slotless design with distributed magnets creates a more uniform magnetic field distribution that reduces hysteresis losses in the magnetic materials
3Ease of operation
If stepper motors are used for fluidic pump control, then position control is provided, but electromagnetic interference (EMI) and vibration are transferred to surgical devices
Solution Approach 1:
The patent replaces the mechanical commutation system of stepper motors with an electromagnetic field-based BSDC motor system. This substitution eliminates the mechanical contacts and commutators that generate electromagnetic interference and mechanical vibration, providing smooth electromagnetic torque delivery without harmful EMI or vibration transfer to surgical devices
Solution Approach 2:
The patent introduces advanced electronic commutation circuitry with sine-wave current control as an intermediary between the control system and motor. This electronic mediation provides precise position control through field control rather than mechanical means, eliminating direct mechanical coupling and associated vibration and EMI
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
BSDC motors offer improved thermal efficiency, reduced vibration and electromagnetic interference (EMI), and lower torque ripple, leading to more reliable and precise control of fluid pressure and vacuum, enhancing the performance of fluidic pumps in ophthalmic surgical applications.
Implementation Method 1
a sine-cosine encoder with an analog-to-digital converter (ADC) mechanically coupled to the BSDC motor
Implementation Method 2
generating, by the three-phase amplifier, a three-phase signal based on the command signal and providing the three-phase signal, typically sine waves, to a brushless slotless direct current (BSDC) motor
Data Source
AI summary
In certain embodiments, a fluidic pump system includes a brushless slotless direct current (BSDC) motor mechanically coupled to a fluidic pump, and a motor controller communicably coupled to the BSDC motor. The BSDC motor is configured to drive the fluidic pump, and the motor controller is configured to generate command signals to drive the BSDC motor. The fluidic pump system further includes commutation circuitry coupled to the BSDC motor that is configured to provide digital sine-wave commutation of the BSDC motor and to provide an indication of movement of the BSDC motor to the motor controller.