Medical Robotic System Velocity Control for Tissue Safety
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Solution Overview
Problem
Medical robotic systems face challenges in preventing excessive force exertion by end effectors during minimally invasive surgeries, as existing force feedback systems suffer from low fidelity and instability, which can lead to tissue damage or instrument breakage.
Innovation Solution
A control system and method that inhibits damaging motions by receiving commanded movements and force data from the end effector, determining a reduced velocity to prevent excessive force, and controlling the robotic manipulation to restrict movement accordingly, while also warning the surgeon through haptic feedback and visual/auditory cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If force feedback systems are used to provide tactile feedback to the surgeon, then the surgeon can feel contact forces, but the systems suffer from low fidelity and instability
Solution Approach 1:
The patent introduces an intermediary control system that acts as a mediator between the surgeon's input device and the slave manipulator. This intermediary layer processes force information and generates appropriate velocity commands, avoiding the need for complex direct force feedback hardware while achieving reliable force control through computational mediation
Solution Approach 2:
The patent replaces complex mechanical force feedback systems with a computational control approach. Instead of using mechanical components to physically reproduce forces, the system uses processors to calculate and limit velocities based on force information, substituting mechanical complexity with computational simplicity
2Ease of operation
If the surgeon applies force to manipulate the end effector, then the surgical procedure can be performed, but excessive force may cause tissue damage or instrument breakage
Solution Approach 1:
The system performs preliminary action by pre-calculating safe velocity limits based on force thresholds before the surgeon's manipulation can cause damage. The processor determines velocity commands that inherently prevent excessive force application, proactively avoiding harmful outcomes rather than reacting after damage occurs
Solution Approach 2:
The patent implements feedback by continuously monitoring force information from the end effector and using this information to adjust velocity commands in real-time. This closed-loop feedback ensures that the surgeon's manipulation remains within safe force boundaries while maintaining operational ease
3Productivity
If velocity is increased to improve surgical efficiency, then productivity increases, but the risk of excessive force and damage increases
Solution Approach 1:
The patent applies dynamics by making the velocity limit adaptive rather than fixed. The system dynamically adjusts the maximum velocity based on the current force state, allowing higher velocities when force is low and reducing velocities when force approaches dangerous levels. This dynamic adjustment maintains productivity while preventing excessive force through real-time velocity modulation
Data Source
AI summary
A medical robotic system includes a surgical instrument, a robotic arm assembly, an input device, and a processor. The surgical instrument has an end effector and a sensor for sensing a force exerted by the end effector, and is operatively mounted on the robotic arm assembly. The processor is configured to receive commanded movement of the end effector from the input device, receive information of the force from the sensor, determine a reduced velocity of the commanded movement that would inhibit damage causing motion of the end effector, and control robotic manipulation of the surgical instrument in response to the commanded movement of the end effector while restricting the velocity of the commanded movement to the reduced velocity.