Base-Mounted Force Sensor for Surgical Robot Arm

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Solution Overview

Problem

Current telerobotic surgical systems face challenges in providing accurate feedback of forces and torques to surgeons, particularly due to the placement of force sensors distal to wrist joints, mechanical vibrations, and the complexity of fitting and positioning wires in small surgical instruments.

Innovation Solution

A robotic surgical system with a force/torque sensor mounted at the base of the manipulator arm, using strain gauges and optical fibers to accurately measure and transmit forces and torques to the surgeon, eliminating the need for wires through flexing wrist joints and allowing separate yaw and grip axes on the same pivot.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If force sensors are placed distal to wrist joints, then force sensing capability is improved, but device complexity increases due to wire routing through flexing joints

Engineering Contradiction:

Improveforce sensing capabilityVSAvoidwire routing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent inverts the conventional sensor placement by moving the force sensor from the distal end (outboard of wrist joints) to the proximal end (inboard of wrist joints) of the manipulator arm. This inversion eliminates the need to route wires through flexing wrist joints, thereby reducing device complexity while preserving force sensing capability through mathematical transformation of the sensor data.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If wires are routed through flexing wrist joints, then force sensing is achieved, but reliability decreases due to potential wire damage during flexing

Engineering Contradiction:

Improveforce sensingVSAvoidwire integrity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

By inverting the sensor placement to the proximal end of the manipulator arm, the patent eliminates wire routing through flexing joints entirely. The wires remain stationary at the proximal end while the distal end flexes, preventing wire damage and improving reliability while maintaining force sensing capability through coordinate transformation algorithms.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If base-mounted force sensor is used, then ease of manufacture is improved, but measurement precision may be affected by mechanical vibrations

Engineering Contradiction:

Improvesensor installation simplicityVSAvoidforce measurement accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent employs feedback mechanisms through mathematical models and coordinate transformations that compensate for vibrations and mechanical compliance at the base-mounted sensor location. By continuously transforming the sensor readings into the distal coordinate frame and applying compensation algorithms, the system maintains measurement precision despite the vulnerable base-mounted sensor position.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces direct mechanical force transmission through rigid linkages with a mathematical model-based approach. Instead of mechanically isolating the sensor from vibrations, the system uses computational methods to filter and compensate for vibrational effects, substituting mechanical complexity with algorithmic solutions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If force sensor is placed distal to wrist joints, then force feedback accuracy is improved, but ease of operation deteriorates due to complex wire positioning requirements

Engineering Contradiction:

Improveforce feedback accuracyVSAvoidwire positioning difficulty

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent simplifies operation by inverting sensor placement to the proximal end, eliminating the need for operators to position wires through complex flexing joints. The stationary proximal mounting allows straightforward wire connection while mathematical transformations preserve the accuracy of force feedback, making the system easier to operate and maintain.

Inventive Principle:

Principle #13The other way round (Inversion)

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

This configuration enhances the surgeon's ability to accurately control surgical instruments by providing precise force and torque feedback, reducing mechanical vibrations, and simplifying the placement of wires, thereby improving surgical precision and instrument control.

Implementation Method 1

A robotic surgical system with a force/torque sensor mounted at the base of the manipulator arm, using strain gauges to accurately measure and transmit forces and torques

Methodology Applied

Scientific EffectStrain gauge measurement: Piezoresistive Effect

Implementation Method 2

using strain gauges and optical fibers to accurately measure and transmit forces and torques to the surgeon

Methodology Applied

Scientific EffectOptical fiber transmission: Optical Fibre

Data Source

PatentUS9895813B2Force and torque sensing in a surgical robot setup arm

Publication Date: 2018.02.20 INTUITIVE SURGICAL OPERATIONS INC

AI summary

An apparatus, system, and method for improving force and torque sensing and feedback to the surgeon performing a telerobotic surgery are provided. In one embodiment, a robotic surgical manipulator system, a robotic surgical system, and a method for improved sensing of forces on a robotic surgical instrument and/or manipulator arm are disclosed.