Master-Slave Surgical Robot Dynamic Speed Control for Delay Mitigation
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Solution Overview
Problem
In master-slave robotic systems for medical or surgical teleoperation, particularly with unconstrained master devices, delays, actuation system limits, and mechanical resonance cause positional discrepancies between the master and slave devices, leading to perceptible delays and distortions in the slave device's movements, especially during rapid changes in direction or high speeds.
Innovation Solution
A method involving passivation techniques to modify the target pose of the slave device by reducing its translational speed and power, using transfer functions dependent on the master device's speed and distance, to mitigate these discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the slave device follows the master device position and orientation in real-time, then the tracking accuracy is improved, but the system delays and actuation limits cause positional discrepancies and perceptible delays in motion
Solution Approach 1:
The patent applies dynamic speed adjustment by modifying the slave device's speed based on real-time conditions. The control system dynamically reduces the slave device's speed when approaching certain positions or during rapid master device movements, creating a adaptive response that compensates for system delays and actuation limits while maintaining tracking accuracy.
Solution Approach 2:
The patent implements preliminary action by predicting future positions and proactively adjusting the slave device's speed before positional discrepancies become problematic. The control system anticipates potential conflicts between master and slave device positions and pre-adjusts velocities to prevent perceptible delays and maintain coherent motion throughout the teleoperation task.
2Productivity
If the slave device moves at high speed to reduce delay perception, then the productivity is improved, but mechanical resonance and actuation limits cause motion distortions and trajectory deviations
Solution Approach 1:
The patent changes the speed parameter dynamically based on the operational context. When the master device moves rapidly or changes direction quickly, the control system temporarily reduces the slave device's speed to stay below mechanical resonance thresholds and actuation limits. This parameter adjustment prevents harmful vibrations and trajectory deviations while maintaining high productivity during normal operations.
3Productivity
If the operator makes rapid direction changes to improve responsiveness, then the productivity is improved, but the accumulated movement delay causes the slave device to converge to the master device along the shortest trajectory rather than following the intended path
Solution Approach 1:
The patent applies dynamic velocity modification during rapid direction changes. When detecting quick master device maneuvers, the control system temporarily adjusts the slave device's velocity to prevent convergence along shortest trajectories. This dynamic adjustment ensures the slave device follows the intended curved paths rather than cutting corners, maintaining trajectory accuracy during high-speed operations.
Data Source
AI summary
A method for controlling a slave device during teleoperation is performed by a robotic system. The robotic system includes a master device movable by an operator, and a slave device having a surgical instrument controllable by the master device. The method defines a nominal target pose in a workspace of the slave device, modifies the nominal target pose to obtain a modified target pose, and controls motion of the slave device in the workspace so that the slave follows the modified target pose. Modifying the nominal target pose includes decreasing a translational speed module of the modified target pose relative to speed of the nominal target pose, and/or decreasing instantaneous power or energy imparted to the slave device, according to a transfer function dependent on the instantaneous speed/instantaneous power of the master device and/or the distance between a current position and the nominal target pose of the slave device.