Ultrasonic End Effector State Estimation via Complex Impedance
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Solution Overview
Problem
Existing ultrasonic and electrosurgical devices require different generators due to their unique drive signal, sensing, and feedback needs, limiting their ability to recognize interchangeable instruments and optimize control and diagnostic processes accordingly. Additionally, there are challenges with capacitive coupling leading to unacceptable patient exposure to leakage current.
Innovation Solution
A method and system for estimating the state of an ultrasonic end effector by measuring and analyzing the complex impedance of the ultrasonic transducer, comparing it to a reference pattern, and controlling the end effector based on the estimated state. This approach allows for unified control of both ultrasonic and electrosurgical instruments and minimizes patient exposure to leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different generators are used for ultrasonic and electrosurgical devices, then each device can have optimized control and sensing, but the system complexity increases and interchangeability is limited
Solution Approach 1:
The generator is designed to provide both ultrasonic and electrosurgical functions through a single unified platform. The system can operate in different modes (ultrasonic cutting, ultrasonic coagulation, electrosurgical cutting, electrosurgical coagulation) using the same generator hardware, eliminating the need for separate dedicated generators and reducing overall system complexity while maintaining optimized control for each function
Solution Approach 2:
The generator dynamically adapts its operating parameters and control algorithms based on the detected instrument type and operational mode. The system can switch between different drive signals, impedance measurement techniques, and feedback control strategies to optimize performance for ultrasonic or electrosurgical operations as needed
2Device complexity
If traditional impedance measurement is used in noisy environments, then the measurement process is simple, but electromagnetic interference reduces the ability to maintain lock on resonant frequency
Solution Approach 1:
The system continuously monitors impedance magnitude and phase, and uses this feedback to adjust the drive frequency to maintain operation at the resonant frequency. The feedback loop compensates for drift and interference by detecting changes in the impedance characteristics and correcting the operating frequency accordingly
Solution Approach 2:
The system uses impedance magnitude and phase as intermediary parameters to indirectly detect and maintain resonant frequency operation. Rather than directly measuring frequency, the system uses impedance characteristics as a mediator to infer and control the resonant state, improving reliability in noisy environments
3Power
If asymmetrical harmonic distortion is present in the drive signal, then the generator can deliver high power, but the accuracy of impedance magnitude and phase measurements is reduced
Solution Approach 1:
The system measures the actual impedance magnitude and phase despite harmonic distortion and uses this information to correct and refine the measurements. The feedback mechanism allows the system to compensate for measurement errors introduced by the distorted drive signal, maintaining accuracy while delivering high power
Solution Approach 2:
The system intentionally allows asymmetrical harmonic distortion in the drive signal to deliver sufficient power for surgical operations, while using post-processing techniques and feedback to extract accurate impedance measurements from the distorted signal. The excessive power delivery is accepted as a trade-off, with measurement accuracy restored through signal processing
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
The proposed solution enables efficient estimation and control of the ultrasonic end effector's state, facilitating unified operation of ultrasonic and electrosurgical devices. It also reduces the risk of patient exposure to harmful leakage currents by improving the generator's ability to manage capacitive coupling.
Implementation Method 1
Vibrating at high frequencies (e.g., 55,500 cycles per second), the ultrasonic blade denatures protein in the tissue to form a sticky coagulum
Implementation Method 2
the ultrasonic blade denatures protein in the tissue to form a sticky coagulum
Implementation Method 3
measuring, by a control circuit, a complex impedance of an ultrasonic transducer
Data Source
AI summary
Various aspects of a generator, ultrasonic device, and method for estimating and controlling a state of an end effector of an ultrasonic device are disclosed. The ultrasonic device includes an electromechanical ultrasonic system defined by a predetermined resonant frequency, including an ultrasonic transducer coupled to an ultrasonic blade. A control circuit measures a complex impedance of an ultrasonic transducer, wherein the complex impedance as defined asZg(t)=Vg(t)Ig(t);The control circuit receives a complex impedance measurement data point and compares the complex impedance measurement data point to a data point in a reference complex impedance characteristic pattern. The control circuit then classifies the complex impedance measurement data point based on a result of the comparison analysis and assigns a state or condition of the end effector based on the result of the comparison analysis. The control circuit estimates the state of the end effector of the ultrasonic device and controls the state of the end effector of the ultrasonic device based on the estimated state.