Cable-Driven Surgical Wrist Hardstop Detection by Tension Threshold
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Solution Overview
Problem
Existing robotic surgical systems lack effective methods for detecting and handling hardstops, which can lead to difficulties in identifying and managing contact with rigid objects during minimally-invasive surgeries, particularly in robotic-assisted procedures.
Innovation Solution
A robotically assisted surgical system with a wrist mechanism driven by cables, equipped with sensors to detect forces, processors for comparing cable tensions, and a torque threshold calculation to identify hardstops, enabling precise detection and handling of obstacles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If robotic arms are used to manipulate surgical tools in minimally-invasive surgery, then patient recovery time and scarring are reduced, but the ability to detect and handle hardstops contact is compromised
Solution Approach 1:
The system implements feedback by continuously monitoring cable tension forces during robotic arm operation. When the end effector contacts a hardstop, the force sensors detect the sudden increase in cable tension and provide real-time feedback to the control system, enabling immediate detection and handling of the contact condition.
Solution Approach 2:
The patent replaces traditional mechanical hardstop detection mechanisms with a sensor-based force measurement system. Instead of relying on mechanical switches or physical limit stops, the system uses force sensors to detect cable tension changes, enabling more precise and reliable hardstop detection in the robotic surgical system.
2Device complexity
If only video feedback is provided to the operator, then system complexity is reduced, but the ability to identify hardstop contact is insufficient
Solution Approach 1:
The system supplements video feedback with force feedback from cable tension sensors. This multi-modal feedback approach provides the operator with both visual information and tactile-like force information, enabling more reliable hardstop identification without excessively increasing system complexity.
Solution Approach 2:
The force sensors serve multiple functions: they monitor cable tension for normal operation, detect hardstop contacts, and provide feedback for force control. This multi-functionality allows the system to achieve reliable hardstop detection without adding dedicated detection hardware, thereby managing system complexity effectively.
3Measurement precision
If cable tension forces are monitored to detect hardstops, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The existing cable tension sensors, which are already part of the robotic system for normal operation, are utilized for hardstop detection as well. This multi-functional use of existing sensors achieves accurate hardstop detection without adding dedicated detection hardware, thereby managing system complexity effectively.
Solution Approach 2:
The robotic system's existing force sensing capabilities serve the dual purpose of both normal operation control and hardstop detection. The system essentially detects hardstops using its own inherent sensing mechanisms, eliminating the need for separate detection systems and reducing overall complexity.
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
The system provides accurate and reliable detection of hardstops, enhancing the safety and precision of robotic surgical procedures by preventing unintended contact with rigid objects.
Implementation Method 1
A plurality of sensors configured to detect forces associated with the plurality of cables
Data Source
AI summary
The disclosed embodiments relate to systems and methods for a surgical tool or a surgical robotic system. One example system for detecting a hardstop for a surgical tool includes a wrist connected to and driven by a plurality of cables of a tool driver, a plurality of sensors configured to detect forces associated with the plurality of cables one or more processors configured to perform a comparison of the forces associated with the plurality of cables, selected a highest tension cable from the plurality of cables based on the comparison of the forces associated with the plurality of cables, set a force assigned to the highest tension cable to a predetermined value, calculate a variable torque threshold for the wrist based on a sum of the predetermined value for the highest tension cable and detected forces for remaining cables in the plurality of cables, receive a joint torque value for the wrist, perform a comparison of the received joint torque value for the wrist to a variable wrist torque threshold and identify a hardstop based on the comparison of the received joint torque value for the wrist to the variable wrist torque threshold.