Robotic Sealing Instrument Motor Position Control With Spring Compression

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Solution Overview

Problem

Existing robotic surgical instruments face inconsistencies in monitoring and maintaining the closure pressure between jaw members, leading to unreliable tissue sealing due to the degradation of torque sensor correlations over time.

Innovation Solution

A robotic surgical instrument with a housing and a shaft that includes a selectively engageable end effector assembly, a drive rod, and a spring compression assembly, where the jaw drive input rotates a gear to compress the compression spring a preset number of degrees, ensuring consistent closure pressure between jaw members, and a method to determine a homing position using torque sensors and algorithms to calibrate the instrument.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If torque sensors are used to monitor closure pressure, then initial measurement capability is provided, but reliability deteriorates over time due to sensor degradation

Engineering Contradiction:

Improveclosure pressure measurementVSAvoidmeasurement consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical torque sensor-based measurement system with a spring compression-based mechanical system. The spring compression assembly uses a compression spring with known spring constant that is compressed by a predetermined distance to generate the desired closure pressure, eliminating reliance on torque sensors and their degrading correlations over time.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from torque (which degrades) to spring compression distance (which is mechanically controlled). By controlling the compression distance of the spring with known spring constant, the system achieves reliable closure pressure without depending on torque sensor readings that deteriorate with repeated use.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If sensor-based torque monitoring is used, then closure pressure can be inferred, but consistency is lost over repeated use

Engineering Contradiction:

Improveautomatic pressure controlVSAvoidclosure pressure consistency

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-compressing the spring assembly to a specific compression distance before tissue sealing. The spring is compressed by a predetermined distance that corresponds to the desired closure pressure range, ensuring consistent pressure application from the start of each sealing cycle without relying on sensor feedback.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The spring compression assembly serves itself by using the mechanical properties of the compression spring (known spring constant) to automatically generate the correct closure pressure. The system self-regulates the pressure through the mechanical compression distance, eliminating the need for continuous sensor monitoring and calibration.

Inventive Principle:

Principle #25Self-service

3Reliability

If a compression spring with known spring constant is used, then closure pressure can be controlled, but device complexity increases

Engineering Contradiction:

Improveclosure pressure controlVSAvoidspring compression assembly

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the pressure control function from the complex sensor and control system, isolating it into a dedicated spring compression assembly. By separating the pressure generation function into this specific component with known spring constant, the system achieves reliable pressure control while simplifying the overall control architecture.

Inventive Principle:

Principle #2Taking out (Extraction)

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

Ensures consistent closure pressure between jaw members, maintaining a range of 3 kg/cm² to 16 kg/cm² during repeated use, improving the reliability and accuracy of tissue sealing.

Implementation Method 1

a compression spring having a known spring constant mounted between the proximal and distal hubs

Methodology Applied

Scientific EffectSpring: Spring

Implementation Method 2

compression spring having a known spring constant

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS12433664B2Motor position control and methods for robotic assisted sealing instrument

Publication Date: 2025.10.07 COVIDIEN LP

AI summary

A robotic surgical instrument includes a housing having a shaft extending therefrom configured to receive a first end effector including jaw members moveable between a fully open position wherein the jaw members are spaced a maximum distance relative to one another and a closed position wherein a closure pressure between the jaw members is within a predetermined range. A drive rod actuates the first end effector upon translation thereof. The housing includes a spring compression assembly having proximal and distal hubs with the compression spring disposed therebetween. A jaw drive input rotates a drive gear to translate the distal hub relative to the proximal hub to compress the compression spring and actuate the end effector. Once the jaw members are fully open, the jaw drive input rotates a preset number of degrees to compress the compression spring and approximate the jaw members to a closure pressure within the predetermined range.