Robotic Surgical Tool Homing via Torque-Based Roll Disk Engagement
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Solution Overview
Problem
Surgical robotic systems face challenges in engaging and synchronizing surgical tools with actuators due to the lack of mechanical hardstops, leading to difficulties in detecting engagement and ensuring safe operation, particularly in scenarios with unlimited range of motion and complex mechanical designs that exhibit backlash and compliance.
Innovation Solution
A method and apparatus for engaging the driving motor of a rotary actuator with a surgical instrument's roll tool disk without hardstops, involving torque threshold detection and synchronization of motors, as well as calibration and control mechanisms to account for backlash and compliance, ensuring safe and precise operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical hardstops are used to constrain instrument motion, then engagement detection becomes easier and operation is safer, but the range of motion is limited and the design is less versatile
Solution Approach 1:
The patent replaces mechanical hardstop-based engagement detection with an algorithmic approach that monitors motor operating parameters (torque, current, velocity, impedance). The system detects engagement by analyzing changes in these parameters when the instrument contacts tissue or structures, eliminating the need for physical hardstops and enabling unlimited range of motion while maintaining reliable engagement detection.
Solution Approach 2:
The system continuously monitors motor operating parameters and uses feedback control to detect engagement events. By analyzing real-time data from torque sensors, current measurements, and velocity feedback, the system can reliably identify when the instrument engages with tissue or anatomical structures, replacing the need for mechanical hardstops.
2Reliability
If two motors are used to drive the same joint, then load is distributed and redundancy is improved, but synchronization becomes more complex and engagement detection is more difficult
Solution Approach 1:
The patent merges the control of multiple motors driving the same joint by treating them as a unified system. The algorithm monitors combined motor parameters and detects engagement based on the aggregate response of all motors, rather than requiring individual motor synchronization. This approach maintains redundancy and load distribution while simplifying the detection logic.
Solution Approach 2:
The engagement detection algorithm is designed to work universally with any number of motors driving a joint. By monitoring general motor operating parameters (torque, current, velocity) rather than motor-specific signals, the system can detect engagement whether one or multiple motors are involved, reducing complexity while maintaining reliability.
3Device complexity
If torque threshold detection is used for engagement detection, then the method is simple to implement, but it may fail to detect engagement in instruments without hardstops or with compliant mechanisms
Solution Approach 1:
The system performs preliminary characterization of the instrument's mechanical properties (backlash, compliance, stiffness) during a calibration phase before actual use. This preliminary action allows the engagement detection algorithm to be tailored to each specific instrument's characteristics, improving reliability without increasing operational complexity.
Solution Approach 2:
The system transitions from using fixed torque thresholds to using dynamic thresholds that adapt to the specific instrument's mechanical properties. By characterizing each instrument's backlash and compliance parameters beforehand, the system can set appropriate detection thresholds that work reliably for that specific instrument, rather than using universal fixed thresholds.
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
Enables reliable engagement and synchronization of surgical tools with actuators, enhancing safety and precision in surgical procedures by effectively managing torque and position control, even in systems without mechanical hardstops, and compensating for mechanical recoil and hysteresis.
Implementation Method 1
determining whether a measured torque of the rotary motor exceeds a preset torque threshold
Implementation Method 2
Using two or more coupled motors, the end effector load is divided between the two or more motors that are constrained through the coupling mechanism
Implementation Method 3
the mechanical design of the end effector, as well as properties of the drive train may exhibit backlash and/or compliance
Implementation Method 4
the mechanical design of the end effector, as well as properties of the drive train may exhibit backlash and/or compliance
Data Source
AI summary
The disclosed embodiments relate to systems and methods for a surgical tool or a surgical robotic system. A tool driver is coupled to a distal end of a robotic arm and includes a roll drive disk driven by a rotary motor. One or more processors are configured to detect an attachment of a surgical tool to the tool driver. The surgical tool includes a roll tool disk to be engaged with the roll drive disk of the tool driver, actuate of the roll drive disk through the rotary motor, determine that a measured torque of the rotary motor exceeds a preset torque threshold for a preset period of time since the actuation, and report a successful engagement between the roll drive disk and the roll tool disk.