Surgical Instrument Motor Current Analysis for Mechanical Limit Detection
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Solution Overview
Problem
Existing electromechanical surgical devices rely on multiple mechanical limit sensors and switches to prevent actuation beyond mechanical limits, which increases complexity and cost, and there is a need for a system that can detect mechanical limits without these components.
Innovation Solution
A surgical instrument with a motor and controller that measures current draw to calculate rate of change values, using a condition-of-interest counter and stability counter to determine mechanical limits, thereby terminating current supply to prevent further operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple mechanical limit sensors and switches are used to detect operational state, then mechanical limits can be prevented, but device complexity and cost increase
Solution Approach 1:
The patent extracts the mechanical limit detection function from multiple physical sensors and switches, consolidating it into a single sensor that measures motor current. This removes unnecessary components while preserving the essential safety function of detecting mechanical limits.
Solution Approach 2:
The motor current sensor serves multiple functions: it monitors motor operation, detects mechanical limits, and provides feedback for control adjustments. This multi-functionality eliminates the need for separate mechanical limit sensors and switches, reducing overall device complexity.
2Reliability
If multiple mechanical limit sensors and switches are used, then mechanical limits can be detected, but cost increases
Solution Approach 1:
The patent extracts the mechanical limit detection function from multiple expensive physical components (sensors and switches) and implements it through software processing of motor current data. This extraction eliminates the need to manufacture and assemble multiple separate components, significantly reducing manufacturing cost.
Solution Approach 2:
Instead of using physical copies of sensors throughout the device, the patent uses a single sensor reading (motor current) that indirectly represents the mechanical state. This virtual copying approach reduces component count and manufacturing complexity.
3Reliability
If threshold-based mechanical limit detection is used, then mechanical limits can be detected, but premature shutdowns occur due to tissue clamping loads
Solution Approach 1:
The patent transitions from a static threshold-based detection method to a dynamic approach that analyzes the rate of change of motor current over time. This dynamic method adapts to varying load conditions, distinguishing between normal tissue clamping (gradual current increase) and mechanical limits (abrupt current change), thereby improving detection accuracy and preventing premature shutdowns.
Solution Approach 2:
The system continuously monitors motor current and uses feedback from the rate of change analysis to adjust operation. This feedback mechanism allows the system to respond appropriately to real-time conditions, differentiating between acceptable tissue clamping loads and actual mechanical limits, thus improving measurement precision.
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 simplifies the detection of mechanical limits, reduces complexity and cost, and prevents premature shutdowns by analyzing the rate of change in motor current, improving the reliability and safety of the surgical instrument.
Implementation Method 1
a motor disposed within the handle assembly and operatively coupled to the drive assembly
Implementation Method 2
a controller operatively coupled to the motor for measuring a current draw of the motor to obtain a plurality of samples of the current draw
Data Source
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AI summary
A method for controlling a surgical instrument comprising; measuring a current draw of a motor coupled to a drive assembly for actuating an end effector of the surgical instrument to obtain a plurality of samples of the current draw, calculating a plurality of rate of change values based on the plurality of samples of the current draw, determining whether operation of the motor reached a mechanical limit based on a portion of the plurality of rate of change values being within a first range of rate of change values and determining whether operation of the motor is stable based on a portion of the plurality of rate of change values being within a second range of rate of change values.