Surgical Instrument Shaft Support for Accurate External Force Sensing

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Solution Overview

Problem

Existing surgical instrument units in master-slave robots face challenges in accurately detecting external forces due to interference from cable tension and potential noise from inertial forces, especially when force sensors are mounted on the root or tip end, which can hinder movable range and complicate sterilization.

Innovation Solution

A surgical instrument unit with a shaft and hollow base, supported by a strain generating part comprising two layers of multidirectional strain generating bodies, each inclined at opposite angles, and a strain sensor to detect external forces without interference from cable tension or inertial forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a force sensor is mounted on the root side of a cable drive to sense the force applied to the tip end, then the external force can be detected, but inertial force is added to the measurement value as noise during arm motion due to the large weight of the force sensor

Engineering Contradiction:

Improveexternal force detection accuracyVSAvoidinertial force noise

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The force sensing function is extracted from the traditional force sensor mounted on the root side and transferred to a strain sensor integrated into the cable drive mechanism itself. This eliminates the need for a separate heavy force sensor while maintaining detection capability through the cable tension measurement.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The cable tension, which was previously just a driving force, serves as an intermediary element that carries both the driving force and the external force information. By measuring the tension in the cable, the system indirectly detects external force without requiring a separate sensing mechanism that would introduce inertial noise.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a force sensor is mounted on a gripper part of the end effector to sense external force, then accurate force measurement is possible, but electric wiring and optical fiber must be provided up to the gripper part, which hinders the movable range of the tip end

Engineering Contradiction:

Improveexternal force detection accuracyVSAvoidtip end movable range

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The force sensing function is merged with the cable drive mechanism itself. The strain sensor is integrated into the cable drive structure, eliminating the need for separate wiring and optical fibers to reach the gripper. This integration maintains detection accuracy while preserving full mobility range.

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If a strain sensor is simply arranged around the shaft to sense external force, then the structure is simple, but interference occurs between the external force and tension caused by the plurality of cables, making accurate measurement difficult

Engineering Contradiction:

Improvesensor arrangement simplicityVSAvoidexternal force measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Instead of placing a strain sensor around the entire shaft, the sensing function is localized to specific measurement points within the cable drive mechanism where tension can be directly measured. This localized approach eliminates interference from multiple cables while maintaining measurement accuracy.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The traditional mechanical strain sensor arrangement around the shaft is replaced with a cable tension measurement system. By measuring the tension in the cable rather than strain on the shaft, the system avoids interference from multiple cables while maintaining the ability to detect external force.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The solution enables accurate external force detection by minimizing interference from cable tension and inertial forces, ensuring reliable operation and ease of sterilization, while maintaining a compact design.

Implementation Method 1

a strain sensor that detects strain in the strain generating part

Methodology Applied

Scientific EffectStrain: Deformation

Data Source

PatentUS12544087B2Surgical instrument unit, force detection device, and surgery support system

Publication Date: 2026.02.10 SONY GROUP CORP

AI summary

A surgical instrument unit includes a shaft having an end effector at the tip end, a hollow base, and a strain generating part that supports a root part of the shaft in the base. The strain generating part has a first-layer strain generating body and a second-layer strain generating body arranged in order in a long axis direction of the shaft, each of the first-layer strain generating body and the second-layer strain generating body including a multidirectional strain generating body supporting a root part of the shaft with a plurality of legs. The first strain generating body is inclined by a predetermined angle θ with respect to a plane orthogonal to a long axis of the shaft, and the second strain generating body is inclined by an angle −θ opposite to each leg of the first strain generating body with respect to the plane.