Surgical Teleoperation Control at Slave Rotation Workspace Limits

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Solution Overview

Problem

Existing master-slave robotic systems for medical or surgical teleoperation face challenges in maintaining intuitive operator behavior and high usability when the slave device approaches or exceeds the limits of its workspace, particularly with rotational degrees of freedom, leading to performance degradation due to rotational misalignments and lack of force feedback.

Innovation Solution

A method and system that define a nominal target pose, a modified target pose, a departure region, and a reentry region in the rotational space of the slave device, controlling the slave device to converge to the modified target pose through slowed teleoperation when approaching or exceeding workspace limits, and blocking movements until both poses are within defined regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the master device is mechanically unconstrained without force feedback, then the operator enjoys greater freedom of movement and intuitive control, but the slave device may reach physical movement limits causing rotational misalignment and performance degradation

Engineering Contradiction:

Improveoperator freedom of movementVSAvoidslave device performance near workspace limits

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The control system implements feedback by continuously monitoring the slave device's current pose and comparing it with the nominal target pose to detect when the slave approaches or exceeds workspace limits. This feedback loop enables the system to automatically apply corrective transformations to realign the slave device with the master device, preventing rotational misalignment while maintaining operator freedom of movement.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically changes the transformation parameters between master and slave devices based on the slave's position relative to its workspace limits. When the slave device is within acceptable limits, the transformation is direct. When limits are approached or exceeded, the system applies a corrective transformation to adjust the slave's orientation, ensuring it remains aligned with the master device's intended direction without physical constraints.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the slave device is controlled to strictly follow the master device's nominal target pose, then teleoperation accuracy is maximized, but the system becomes unusable when the nominal target pose exceeds the slave device's workspace limits

Engineering Contradiction:

Improveteleoperation accuracyVSAvoidsystem usability near workspace limits

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The control system dynamically adapts the transformation between master and slave devices based on real-time conditions. When the nominal target pose is within the slave's workspace, the system maintains direct 1:1 mapping for maximum accuracy. When the nominal target pose exceeds workspace limits, the system dynamically applies a corrective transformation to redirect the slave device along the boundary of its workspace, maintaining usability while preserving teleoperation accuracy within physical constraints.

Inventive Principle:

Principle #15Dynamics

3Reliability

If the system applies corrective transformations to maintain alignment near workspace limits, then rotational misalignment is prevented, but the teleoperation response time increases due to the slowed teleoperation phase

Engineering Contradiction:

Improverotational alignment maintenanceVSAvoidteleoperation response time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system applies corrective transformations partially, only when and where needed. The slowed teleoperation phase with corrective transformation is activated only when the nominal target pose approaches or exceeds workspace limits. When both poses are within acceptable ranges, the system operates in normal mode without correction, minimizing time loss while maintaining rotational alignment only when necessary.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS20250366943A1Method and system for controlling a slave device, in a master-slave robotic system for surgical teleoperation, at physical limits of movement of the slave device

Publication Date: 2025.12.04 MEDICAL MICROINSTRUMENTS INC

AI summary

A method controls a robotic system slave device for medical/surgical teleoperation. The system includes a hand-held master device movable by an operator and controlling a slave device. If a nominal target pose having an orientation in a rotational space of the slave device is outside a slave device working region, and the nominal or modified target pose inside the working region, are inside the departure region, the slave device orientation is converged to the modified target pose. If the nominal and/or modified target poses are outside the departure region, rotational movement of the slave device is blocked until the nominal and modified target poses enter into the reentry region. When the nominal and modified target poses return to the reentry region, the slave device orientation is converged to the modified target pose, through a teleoperation phase, ending when the slave device orientation converges to the modified target pose.