Surgical Stapler Velocity Control via Variable Zones
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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 effectively, particularly due to varying tissue conditions and load distributions during the firing stroke, which can lead to inconsistent performance and tissue handling issues.
Innovation Solution
A surgical instrument with a control circuit that uses a combination of open-loop and closed-loop control systems, including a motor drive circuit and position sensors, to adjust the firing velocity based on real-time tissue conditions by measuring current, time, and displacement, allowing for variable velocity zones during the firing stroke to accommodate different tissue loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a motor drives the displacement member at constant velocity, then the device complexity is reduced, but the tissue handling consistency deteriorates due to varying tissue conditions
Solution Approach 1:
The firing stroke is divided into multiple zones (first zone with highest load, second zone with medium load, third zone with least load) with different velocity requirements. The control system segments the motion control to match load distribution, applying slower velocity in high-load zones and faster velocity in low-load zones, thereby maintaining tissue handling consistency without requiring completely complex adaptive control throughout the entire stroke.
Solution Approach 2:
The motor velocity is made dynamic rather than constant, with the control circuit adjusting velocity based on real-time feedback from position sensors and current measurements. The system transitions from a static constant-velocity mode to a dynamic variable-velocity mode that adapts to varying tissue conditions and load requirements across different zones of the firing stroke.
2Productivity
If the firing velocity is increased to improve productivity, then the cutting efficiency is improved, but the manufacturing precision of tissue handling deteriorates under high load conditions
Solution Approach 1:
Different velocity qualities are applied to different zones of the firing stroke based on local load conditions. The first zone (highest load) receives slower velocity for precise tissue handling, the second zone (medium load) receives moderate velocity, and the third zone (least load) receives faster velocity for improved productivity. This local differentiation of velocity quality resolves the contradiction between cutting efficiency and tissue handling precision.
3Device complexity
If open-loop control is used to simplify the control system, then the device complexity is reduced, but the measurement precision of tissue conditions deteriorates
Solution Approach 1:
The control system incorporates feedback mechanisms using position sensors to monitor displacement member position and current measurements to infer tissue load conditions. This feedback enables the control circuit to adjust motor velocity in real-time, achieving precise tissue condition measurement and response while maintaining relatively simple device architecture through efficient use of sensor data and control algorithms.
Data Source
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AI summary
A motorized surgical instrument is disclosed. The surgical instrument includes a displacement member, a motor coupled to the displacement member, the motor operable to translate the displacement member, a control circuit coupled to the motor, and a position sensor coupled to the control circuit. The control circuit is configured to receive a position output of the position sensor indicative of at least one position of the displacement member and control velocity of the motor to translate the displacement member at a plurality of velocities corresponding to the position output. Each of the plurality of velocities is maintained in a predetermined zone.