Surgical Stapler Motor Velocity Control via Position Feedback
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Solution Overview
Problem
Motorized surgical stapling and cutting instruments face challenges in controlling the velocity of cutting members and articulating end effectors to accommodate varying tissue thickness, leading to inconsistent force requirements and potential tissue damage.
Innovation Solution
A surgical instrument with a control circuit that includes a motor driver, position sensor, and microcontroller, which adjusts the motor speed based on tissue thickness by measuring the displacement member's position or velocity, allowing for continuous velocity control and adaptive articulation velocity during tissue engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cutting member velocity is increased to improve surgical productivity, then the cutting efficiency is improved, but the force to fire load on the cutting member increases causing potential tissue damage
Solution Approach 1:
The system dynamically adjusts the cutting member velocity based on real-time feedback from force sensors and position encoders. The controller modifies velocity profiles during the firing stroke according to actual tissue conditions, transitioning from fixed velocity to adaptive velocity control, thereby optimizing cutting efficiency while preventing tissue damage
Solution Approach 2:
The system implements closed-loop feedback control using force sensors to monitor force to fire load and position encoders to track cutting member displacement. The controller continuously compares actual velocity and force measurements with target values, adjusting motor output in real-time to maintain optimal cutting velocity while keeping forces within safe limits
2Object-affected harmful factors
If the force to fire load is reduced to minimize tissue damage, then the safety is improved, but the cutting member velocity decreases reducing surgical productivity
Solution Approach 1:
The system changes operational parameters (velocity, acceleration, power) dynamically based on tissue thickness and density detection. By adjusting these parameters in real-time according to feedback from sensors, the system maintains high cutting efficiency while adapting force levels to prevent tissue damage
Solution Approach 2:
The system performs preliminary detection of tissue conditions using force sensors and position encoders before initiating the cutting stroke. This allows pre-calculation of optimal velocity profiles and force limits specific to the detected tissue characteristics, enabling efficient cutting from the start while preventing excessive forces
3Manufacturing precision
If the tissue thickness is accurately determined to optimize cutting parameters, then the cutting precision is improved, but the measurement complexity increases
Solution Approach 1:
The system uses the cutting member's own motion and the anvil's position as reference frames for measurement. The position encoder tracks displacement relative to the anvil, and force sensors measure interaction forces during tissue engagement, allowing the system to self-determine tissue thickness without external measurement devices
Solution Approach 2:
The force sensors and position encoders serve multiple functions: they monitor cutting member position, determine tissue thickness, calculate velocity profiles, and control motor power output. This multi-functionality reduces the need for separate measurement systems while improving cutting precision
Data Source
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AI summary
A motorized surgical instrument is provided. The surgical instrument includes a displacement member. A motor is coupled to the displacement member. A control circuit is coupled to the motor. A position sensor is coupled to the control circuit. A timer circuit is coupled to the control circuit to measure elapsed time. The control circuit is configured to receive the position of the displacement member from the position sensor, receive elapsed time from the timer circuit, and control velocity of the motor based on the position of the displacement member and the elapsed time. A method of controlling motor velocity of the surgical instrument also is disclosed.