Adaptive Knife Closure Control for Surgical Stapler Force Spikes
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Solution Overview
Problem
Endoscopic surgical staplers experience force spikes during surgical procedures, which can lead to mechanical stress and potential damage to the instrument drivetrain.
Innovation Solution
The surgical instrument employs an adaptive knife-based closure method that modulates clamping speed and force using a controller with force feedback, setting a force threshold based on motor torque capacity and past usage data to smooth out force peaks, ensuring controlled clamping and firing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional open surgical devices are used, then the surgical instrument can access the surgical site directly, but the surgical incision size and post-operative recovery time increase
Solution Approach 1:
The surgical system is divided into modular components: a handle portion containing the motor and control electronics, a shaft providing mechanical transmission, and an end effector performing the surgical function. This segmentation allows the instrument to be inserted through a small trocar while maintaining full surgical capability.
Solution Approach 2:
A shaft acts as an intermediary element connecting the handle portion to the end effector, enabling force and motion transmission through a small incision. The shaft allows the surgical instrument to reach deep into the body cavity without requiring a large opening.
2Force
If the surgical stapler clamps down on tissue with high force, then the tissue sealing is effective, but force spikes occur that can damage the instrument drivetrain
Solution Approach 1:
The motor controller receives feedback signals from the motor's back-EMF and current sensors, allowing it to monitor the clamping force in real-time. When force spikes are detected, the controller adjusts the motor output to prevent damage while maintaining effective tissue clamping.
Solution Approach 2:
The motor controller dynamically adjusts the electrical current delivered to the motor during the clamping cycle. Rather than delivering constant high torque, the controller modulates the current profile to match the tissue's resistance characteristics, reducing force spikes while maintaining adequate clamping force.
3Speed
If the knife advances quickly along the ramp surface, then the closure speed is high, but force spikes occur during the transition to closed position
Solution Approach 1:
The motor controller divides the knife advancement into discrete phases with different speed and torque characteristics. During the initial ramp phase, the knife moves quickly with low force. As the knife approaches the closed position, the controller reduces speed and increases torque control to manage the force spike that occurs during the transition.
Solution Approach 2:
The motor controller changes the electrical parameters (current, voltage, frequency) dynamically during the knife advancement. By adjusting these parameters in response to real-time force feedback, the controller optimizes the balance between closure speed and force spike prevention.
Data Source
AI summary
An apparatus (1000) includes an end effector (200), a motor (1100), a sensor (1104), and a controller (1150). The end effector includes first and second jaws (202, 204) and a knife (206). The controller obtains using the sensor a first force value exerted by the motor as the knife is contacting the ramp surface. The controller determines whether the first force value exerted by the motor exceeds a first predetermined force threshold as the knife is contacting the ramp surface. The controller is configured to alter travel of the knife. Altering the travel of the knife includes at least one of: pausing the knife for a predetermined amount of time, pausing the knife until a second force value exerted by the motor obtained from the sensor is below the first predetermined force threshold, or advancing the knife at a second speed that is less than the first speed.