Robotic Microsurgical Instrument Calibration for Tendon Zeroing
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Solution Overview
Problem
In teleoperated robotic surgery systems, the variability in assembly and deformation of polymeric tendons leads to uncontrollable miniaturized surgical instruments due to elongation and recovery issues, making precise calibration of the kinematic zero point challenging, especially in miniaturized instruments with high production variability.
Innovation Solution
A method for calibrating surgical instruments involves locking the articulated tip using a constraining element and using force sensors to detect contact between motorized actuators and transmission elements, allowing for precise matching of motor positions with the end-effector configuration, even with low actuation force and polymeric tendons, thereby overcoming deformation and variability challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If polymeric tendons are used in miniaturized surgical instruments, then the instruments can be made smaller and more flexible, but the tendons undergo elongation and deformation that makes precise calibration difficult
Solution Approach 1:
The patent applies preliminary action by performing calibration operations before the surgical instrument is used. The method locks the articulated tip in a predefined position and actuates motors to bring actuators into contact with transmission elements, storing these positions as reference points. This preliminary calibration establishes the kinematic zero point before polymeric tendon deformation occurs during surgery, ensuring precise initial positioning despite subsequent tendon elongation.
2Speed
If high initial load is applied to tendons before assembly, then plasticity is removed and rapid actuation response is achieved, but permanent elongation deformation occurs
Solution Approach 1:
The patent applies parameter changes by modifying the calibration approach to account for tendon deformation characteristics. Instead of trying to prevent tendon elongation through high preloading, the method accepts the deformation and calibrates the system to the actual tendon state. The control system stores motor positions corresponding to the articulated tip in predefined positions, creating a mapping that compensates for the elongated tendon length and maintains precise control.
3Measurement precision
If force sensors are used to detect contact between actuators and transmission elements, then precise calibration is achieved, but the system complexity increases
Solution Approach 1:
The patent applies the intermediary principle by introducing force sensors as mediators between the actuators and transmission elements. These sensors detect the contact force when motors actuate to bring actuators into contact with transmission elements during calibration. The force sensors provide precise feedback on contact detection, enabling accurate establishment of the kinematic zero point while isolating the complexity to specific measurement points rather than the entire system.
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 method enables precise and repeatable calibration of surgical instruments, ensuring accurate kinematic zero point definition and maintaining instrument precision during teleoperation, even with polymeric tendons subject to recoverable or non-recoverable deformation.
Implementation Method 1
using force sensors to detect contact between motorized actuators and transmission elements
Implementation Method 2
elastic elongation deformation, which is recovered when the tensile load stops
Implementation Method 3
Viscous creep deformation under tensile load is a time-dependent effect which affects some types of intertwined cords when subject to fatigue
Implementation Method 4
locking the articulated tip using a constraining element
Data Source
AI summary
A method calibrates a surgical instrument of a teleoperated robotic surgery system. The surgical instrument has transmission elements associated with respective tendons and connected to an articulated end-effector connectable, to determine correlate movements between the transmission elements and articulated end-effector. Motorized actuators operatively connect to respective transmission elements to impart movement. The articulated end-effector is arranged and locked in a predetermined reference position univocally associated with a respective resulting position of each transmission element. The actuators are then actuated so each actuator contacts a respective transmission element and the position of the actuators when each actuator contacts a respective transmission element is stored, and the stored actuator reference positions are univocally associated with the end-effector reference position. A kinematic zero condition associates the stored actuator reference position with a virtual zero point. The actuating applies force less than or equal to a threshold force on the respective transmission element.