Surgical Stapler Motor Velocity Control via Displacement Feedback
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Solution Overview
Problem
Motorized surgical stapling and cutting instruments face challenges in accurately controlling the velocity of cutting members and articulation of end effectors to adapt to varying tissue conditions, leading to inconsistent performance and potential tissue damage.
Innovation Solution
A surgical instrument with a displacement member that translates over predefined zones, coupled with a motor, position sensor, and timer circuit, which measures displacement and sets command velocities based on measured positions and elapsed time to adjust for tissue conditions, enabling closed-loop feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open loop control is used for motor velocity, then device complexity is reduced, but manufacturing precision and consistency of stapling/cutting operations deteriorate
Solution Approach 1:
The patent implements closed-loop feedback control by measuring the actual velocity of the cutting member using position sensors and timer circuits, comparing it to the commanded velocity, and adjusting motor control signals to eliminate velocity errors. This feedback mechanism ensures consistent stapling and cutting operations across varying tissue conditions while maintaining manageable system complexity through structured control architecture.
2Ease of operation
If constant velocity is maintained, then ease of operation is improved, but adaptability to varying tissue conditions deteriorates
Solution Approach 1:
The patent employs dynamic velocity adjustment where the commanded velocity is modified in real-time based on feedback from position measurements. The control circuit calculates actual velocity by comparing position changes over time intervals and adjusts motor commands dynamically to compensate for tissue thickness variations, force to fire variations, and other tissue conditions, thereby maintaining both ease of operation and adaptability.
3Productivity
If velocity is increased to improve productivity, then productivity is improved, but force to fire increases causing potential tissue damage
Solution Approach 1:
The control system continuously monitors the actual velocity of the cutting member during the firing stroke and compares it to the commanded velocity. When tissue conditions require lower velocities to reduce force to fire, the feedback mechanism detects the velocity deviation and adjusts motor control signals accordingly, enabling high productivity when conditions permit while preventing tissue damage when force limits are approached.
4Force
If velocity is decreased to reduce force to fire, then force to fire is reduced improving safety, but productivity deteriorates
Solution Approach 1:
The system dynamically adjusts velocity based on real-time feedback from position measurements and tissue condition assessment. Rather than operating at a fixed low velocity, the control circuit modulates velocity dynamically - reducing it when force to fire exceeds thresholds and maintaining higher velocities when tissue conditions permit - thereby optimizing both safety and productivity throughout the firing stroke.
5Manufacturing precision
If measured displacement is used to adjust velocity, then manufacturing precision is improved, but device complexity increases due to additional sensors and control circuitry
Solution Approach 1:
The patent utilizes feedback from position sensors and timer circuits to measure actual cutting member velocity by calculating displacement over specified time intervals. This measured velocity feeds back to the control circuit, which adjusts motor commands to maintain commanded velocity despite variations in tissue conditions, load, or mechanical friction, thereby achieving high velocity measurement accuracy and consistent stapling/cutting precision.
6Adaptability or versatility
If closed loop feedback control is implemented, then adaptability to tissue conditions is improved, but device complexity increases
Solution Approach 1:
The control system implements closed-loop feedback by continuously measuring cutting member position with sensors, calculating actual velocity over time intervals, comparing it to commanded velocity, and adjusting motor control signals accordingly. This feedback architecture enables real-time adaptation to varying tissue conditions including thickness, density, and force to fire variations, while maintaining structured control logic that manages system complexity.
7Measurement precision
If velocity measurements are taken at fixed time intervals, then measurement precision is improved, but loss of time increases due to measurement overhead
Solution Approach 1:
The control system performs velocity measurements at periodic fixed time intervals by recording position at the beginning and end of each interval, calculating displacement, and determining actual velocity. This periodic measurement approach provides sufficiently accurate velocity data for feedback control while minimizing measurement overhead and maintaining real-time responsiveness for adaptive velocity control during the firing stroke.
Data Source
AI summary
A motorized surgical instrument is disclosed. The surgical instrument includes a displacement member, a motor coupled to the displacement member, a control circuit coupled to the motor, a position sensor coupled to the control circuit, and a timer circuit coupled to the control circuit. The timer circuit is configured to measure elapsed time and to to receive, from the position sensor, a position of the displacement member in a current zone during a set time interval, measure displacement of the displacement member at a set time at the end of the set time interval, wherein the measured displacement is defined as the distance traveled by the displacement member during the set time interval at a set command velocity for the current zone, and set a command velocity of the displacement member for a subsequent zone based on the measured displacement of the displacement member within the current zone.