Phacoemulsification Probe Resonance Control Using Magnetic Sensors
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Solution Overview
Problem
Existing phacoemulsification systems face challenges in efficiently maintaining the resonance frequency of piezoelectric crystals due to mechanical load and temperature changes, leading to reduced vibration amplitude and potential eye damage or discomfort, as the drive signal frequency does not adapt to actual resonance frequencies.
Innovation Solution
The system incorporates magnetic-field components, including generators and sensors, to measure the vibration amplitude and direction of the needle, and a processor adaptively adjusts the drive signal frequency to maintain resonance, while using multiple piezoelectric crystals driven in independent resonant modes to minimize mode interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive signal frequency is kept constant, then the system structure is simple, but the vibration amplitude reduces and heat-related issues occur due to frequency drift from mechanical load and temperature changes
Solution Approach 1:
The patent implements a feedback control system where magnetic sensors detect the actual vibration amplitude of the needle, and this information is fed back to a controller that adjusts the drive signal frequency to maintain resonance. This resolves the contradiction by automatically compensating for frequency drift caused by mechanical load and temperature changes, ensuring stable vibration amplitude without requiring overly complex manual intervention.
Solution Approach 2:
The system uses the vibration characteristics of the needle itself to generate feedback signals through magnetic sensors, allowing the system to self-regulate its operating frequency. The needle's own mechanical response serves as the sensing mechanism, eliminating the need for external reference standards or complex calibration systems while maintaining reliable vibration amplitude.
2Productivity
If multiple piezoelectric crystals are used to drive the needle, then the vibration efficiency is improved through multiple resonant modes, but the mode interaction increases system complexity
Solution Approach 1:
The patent divides the piezoelectric actuation system into multiple independent crystal elements, each capable of operating in its own resonant mode. These segmented crystals are arranged to vibrate in specific patterns (e.g., longitudinal and lateral modes) that collectively enhance the needle's vibration efficiency while maintaining independent control of each element to minimize harmful mode interactions.
Solution Approach 2:
Different regions of the piezoelectric crystal assembly are configured with distinct vibrational characteristics - some regions produce longitudinal vibration while others produce lateral vibration. This local differentiation allows each portion of the system to contribute optimally to the overall vibration efficiency without creating conflicting mode interactions, as each local region operates in its optimized mode.
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 ensures continuous vibration at resonant frequencies, enhancing efficiency and safety by preventing amplitude reduction and heat-related issues, allowing precise control of needle motion during cataract surgery.
Implementation Method 1
a piezoelectric crystal configured to vibrate in response to a drive signal
Implementation Method 2
one or more magnetic-field generators configured to generate a magnetic field
Implementation Method 3
one or more magnetic-field sensors configured to sense the magnetic field
Implementation Method 4
The tip of the needle vibrates at ultrasonic frequency to sculpt and emulsify the cataract
Data Source
AI summary
A phacoemulsification device includes a phacoemulsification probe and a processor. The phacoemulsification probe includes a piezoelectric crystal configured to vibrate in response to a drive signal, a needle configured to be inserted into a lens capsule of an eye and to be vibrated by the piezoelectric crystal, and a set of magnetic-field components. The set includes (i) one or more magnetic-field generators configured to generate a magnetic field, and (ii) one or more magnetic-field sensors configured to sense the magnetic field. At least one of the magnetic-field components is coupled to vibrate with the needle and at least one other of the magnetic-field components is isolated from vibration of the needle, thereby causing the magnetic-field sensors to output signals indicative of the vibration. The processor is configured to adaptively adjust a frequency of the drive signal so as to vibrate the needle at a resonant frequency of the piezoelectric crystal.