Electrosurgical RF Power Control Using Dynamic PID Variables
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Solution Overview
Problem
Existing electrosurgical generators face challenges in efficiently controlling power delivery due to tissue impedance changes during procedures, leading to potential patient injury from current spikes or arcs during short circuits and excessive leakage during open circuits, with complex heuristic gain calculations causing delays and inefficiencies.
Innovation Solution
Implementing a proportional-integral-derivative (PID) control loop that dynamically selects process variables based on measured current, voltage, and impedance to control RF power delivery, using a sampling rate to adjust feedback control signals and reduce processing cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repeated measurement of voltage, current, and power is performed at KHz frequency range to control power delivery, then power delivery control is achieved, but processing complexity and delay increase due to multiple error comparisons and heuristic gain calculations
Solution Approach 1:
The patent extracts the essential control function by using a simplified control loop that measures only power and impedance directly, eliminating the need for separate voltage and current measurements and complex heuristic gain calculations. This reduction in measurement and processing complexity maintains reliable power delivery control while reducing device complexity.
Solution Approach 2:
The control loop is designed to perform multiple functions through a single integrated approach: it simultaneously controls power delivery, monitors impedance changes, and responds to aberrant conditions using the same simplified measurement and control mechanism, thereby reducing overall system complexity while maintaining control reliability.
2Reliability
If multiple error values for different parameters are compared to determine adjustments, then power delivery is maintained despite tissue impedance changes, but additional processing circuit cycles and manual gain settings are required
Solution Approach 1:
The patent removes the complex multi-parameter error comparison process and replaces it with direct power and impedance measurement. This extraction of essential control variables eliminates unnecessary processing circuit cycles and manual gain settings, reducing processing delay while maintaining the ability to compensate for tissue impedance changes.
Solution Approach 2:
The control system dynamically adjusts its operation based on real-time impedance measurements, changing control parameters automatically in response to tissue impedance variations. This eliminates the need for manual gain settings and multiple error comparisons, reducing processing time while maintaining reliable power delivery adaptation.
3Object-affected harmful factors
If control loop temporarily interrupts energy delivery during aberrant conditions, then patient injury and instrument damage are minimized, but response time and processing speed are reduced
Solution Approach 1:
The patent implements a feedback control loop that continuously monitors power and impedance measurements. When aberrant conditions are detected, the feedback mechanism automatically triggers appropriate responses (such as interrupting energy delivery) without requiring complex processing or manual intervention. This feedback approach maintains fast response speed while effectively protecting against patient injury and instrument damage.
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 PID control loop effectively maintains consistent power delivery despite tissue impedance changes, reducing the risk of patient injury and instrument damage by quickly responding to aberrant conditions, and simplifying the control process.
Implementation Method 1
An RF output stage is configured to impart RF power between the first and second electrodes
Implementation Method 2
using a proportional-integral-derivative (PID) control loop to control RF power imparted between the electrodes, based upon a selected one of the measured current, the measured voltage, and the calculated power
Data Source
AI summary
An electrosurgical system includes an RF output stage configured to impart RF power between first and second electrodes; measurement circuitry measures current and voltage imparted between the first and second electrodes; a processing circuit calculates power and impedance, based upon the measured current and the measured voltage; the processing circuitry uses a proportional-integral-derivative control loop to control RF power imparted between the electrodes, based upon a selected one of the measured current, the measured voltage, calculated power, and the calculated impedance.