Variable-Stiffness End Effector Coupling for Surgical Vibration Isolation

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Solution Overview

Problem

Robotic surgical systems face challenges in decoupling vibrations from end effectors during procedures, particularly in spinal surgery, due to high rigidity leading to undesired system dynamics and natural frequency vibrations.

Innovation Solution

A variable stiffness end effector system that allows quick decoupling from a rigid mechanism to a compliant mode, using a coupler that switches between rigid and compliant coupling based on vibration signals, reducing natural frequency vibrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the robotic arm and end effector are designed with high rigidity to ensure stability and precision, then positioning accuracy is improved, but natural frequency vibrations occur during tool operation

Engineering Contradiction:

Improvepositioning accuracyVSAvoidnatural frequency vibrations

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The coupling mechanism transitions from a static rigid connection to a dynamic system that can switch between rigid and compliant states. During drilling operations, the coupling becomes compliant to decouple vibrations from the robotic arm. During positioning operations, the coupling becomes rigid to ensure precision. This dynamic adaptability resolves the contradiction by allowing the system to optimize for either precision or vibration reduction depending on the operational phase.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The stiffness parameter of the coupling mechanism is changed dynamically based on operational requirements. The coupling mechanism's stiffness parameter is high during positioning to ensure accuracy, and low during drilling to allow vibration isolation. This parameter change enables the system to avoid natural frequency vibrations while maintaining positioning accuracy when needed.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If a rigid coupling mechanism is used between the end effector support and tool insertion device, then structural stability is improved, but vibrations are transmitted to the robotic arm

Engineering Contradiction:

Improvestructural stabilityVSAvoidvibrations transmitted to robotic arm

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The coupling mechanism is designed to dynamically change its mechanical properties during operation. It provides rigid coupling during positioning to maintain structural stability, then transitions to compliant coupling during drilling to prevent vibration transmission. This dynamic behavior allows the system to maintain stability when needed while avoiding harmful vibrations during tool operation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The compliant mechanism, which might seem to reduce structural stability, actually benefits the system by isolating vibrations during drilling operations. The compliance that could be seen as a weakness becomes a feature that protects the robotic arm from vibration damage and natural frequency excitation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-generated harmful factors

If the coupling mechanism is made compliant to reduce vibrations, then vibration transmission is reduced, but positioning precision and stability deteriorate

Engineering Contradiction:

Improvevibration transmissionVSAvoidpositioning precision

Core Design Contradiction:

Object-generated harmful factorsVSMeasurement precision

Solution Approach 1:

Rather than using a permanently compliant coupling, the system employs a dynamically adjustable coupling that switches between rigid and compliant states. During positioning operations, the coupling is rigid to ensure precision. During drilling operations, the coupling becomes compliant to reduce vibration transmission. This dynamic switching resolves the contradiction by providing the appropriate coupling characteristic for each operational phase.

Inventive Principle:

Principle #15Dynamics

4Reliability

If the system maintains rigid coupling throughout the procedure, then operational stability is improved, but natural frequency vibrations occur during drilling

Engineering Contradiction:

Improveoperational stabilityVSAvoidnatural frequency vibrations

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The system transitions from static rigid coupling to dynamic coupling that adapts to operational requirements. During drilling operations when natural frequency vibrations occur, the coupling becomes compliant to decouple the tool vibrations from the robotic arm. During positioning operations, the coupling remains rigid to maintain operational stability. This dynamic adaptation allows the system to maintain reliability while avoiding vibration problems.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20240358451A1System And Method For Reducing Tool Vibration At A Variable Stiffness End Effector Of A Surgical System

Publication Date: 2024.10.31 MEDTRONIC NAVIGATION INC

AI summary

A method of operating a surgical system includes positioning a variable stiffness end effector assembly relative to a patient. The effector assembly has an end effector support having a tool insertion device disposed therein. The method also rigidly coupes the end effector support to the tool insertion device in a first mode by forming a rigid coupling mechanism, inserting a tool within the tool insertion device, vibrating the tool insertion device with the tool and decoupling the rigid coupling mechanism and compliantly coupling the tool insertion device in a second mode after vibrating.