Surgical Robot Pose Projection for Limited-DOF Tool Control

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Solution Overview

Problem

Robotic surgical systems face challenges in accurately translating user inputs with more degrees of freedom (DOF) into tools with fewer DOF, leading to undesirable and unintuitive behavior due to the lack of mechanical constraints and haptic feedback, especially when using ungrounded user interface devices.

Innovation Solution

Projecting user inputs with six degrees of freedom into a subspace compatible with the limited degrees of freedom of the surgical tool, using inverse kinematics to control the robotic arm and tool, ensuring intuitive operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a user interface device with six degrees of freedom is used to control a surgical tool with fewer degrees of freedom, then the user input flexibility is improved, but the control accuracy and intuitiveness deteriorate due to the mismatch between input DOF and tool DOF

Engineering Contradiction:

Improveuser input flexibilityVSAvoidcontrol accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent introduces a virtual fixture as an intermediary computational layer between the 6-DOF user interface device and the surgical tool with fewer DOF. This virtual fixture maps and constrains the user's 6-DOF inputs into the appropriate subspace matching the tool's DOF capabilities, thereby maintaining input flexibility while ensuring control accuracy through the transformation process.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If mechanical fixtures or haptic feedback are not used to constrain user input, then the ease of operation is improved, but the reliability of command translation deteriorates due to ungrounded input allowing infeasible motions

Engineering Contradiction:

Improveuser interface freedomVSAvoidcommand translation reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces physical mechanical fixtures and haptic feedback mechanisms with a computational virtual fixture implemented through software. This virtual fixture computationally constrains the 6-DOF user inputs to match the surgical tool's DOF without requiring physical contact forces or mechanical constraint structures, thereby maintaining ease of operation while ensuring reliable command translation through algorithmic enforcement of motion constraints.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If direct mapping from 6-DOF user input to tool with fewer DOF is performed without projection, then the response time is improved, but the operational intuitiveness deteriorates due to unfeasible joint commands

Engineering Contradiction:

Improvecommand response speedVSAvoidoperational intuitiveness

Core Design Contradiction:

SpeedVSEase of operation

Solution Approach 1:

The patent applies preliminary action by pre-defining the virtual fixture constraints and projection matrices that map 6-DOF input space to the tool's DOF subspace. These transformation rules are established beforehand based on the tool's kinematic model, allowing the system to rapidly project user inputs without real-time iterative calculations, thus maintaining fast response time while ensuring operationally intuitive and feasible joint commands through pre-computed constraint enforcement.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12514662B2Projection of user interface pose command to reduced degree of freedom space for a surgical robot

Publication Date: 2026.01.06 AURIS HEALTH INC

AI summary

For teleoperation of a surgical robotic system, the user command for the pose of the end effector is projected into a subspace reachable by the end effector. For example, a user command with six DOF is projected to a five DOF subspace. The six DOF user interface device may be used to more intuitively control, based on the projection, the end effector with the limited DOF relative to the user interface device.