Surgical Robot Jaw Cable Breakage Detection Using Torque Feedback
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Solution Overview
Problem
Surgical robotic instruments experience cable snapping due to high strain during actuation, leading to uncontrolled movement of end effectors that can damage other instruments or camera.
Innovation Solution
A surgical robotic system with an instrument drive unit (IDU) equipped with high-side and low-side motors and torque/position sensors, a controller that calculates the angle and combined torque between jaws, and detects cable breakage by analyzing the angle and torque derivatives, issuing an alert when a cable is broken.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cables are used to actuate surgical robotic instruments, then the instrument can be moved to position the end effector at a work site, but the cables may snap due to high strain during actuation
Solution Approach 1:
The system performs preliminary detection of cable breakage by monitoring torque and position data before uncontrolled movement occurs. The controller continuously calculates jaw angle and compares torque measurements against expected values to identify cable failures early, preventing catastrophic instrument malfunction.
Solution Approach 2:
The system implements feedback through torque sensors that continuously monitor the force required to actuate cables. When torque exceeds predetermined thresholds or shows abnormal patterns indicating cable degradation or breakage, the system provides feedback signals to alert operators and prevent further operation that could cause damage.
2Reliability
If cable breakage detection is implemented using torque and position sensors, then cable failure can be detected and alerts can be generated, but the device complexity increases
Solution Approach 1:
The torque sensors and position sensors serve multiple functions: they control instrument actuation, monitor cable health, detect breakages, and provide diagnostic information. This multi-functionality reduces the need for separate dedicated detection systems, thereby limiting the increase in device complexity while maintaining high reliability.
Solution Approach 2:
The system uses its own actuation sensors (torque and position sensors already required for instrument control) to simultaneously perform cable breakage detection. Rather than adding separate detection hardware, the system self-monitors cable health using data already collected during normal operation, minimizing additional complexity.
Data Source
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AI summary
A surgical system includes an instrument drive unit having a plurality of motors, two of which are high-side motors and two of which are low-side motors. The instrument drive unit is coupled to an instrument having an end effector with a first jaw and a second jaw. The instrument also includes a plurality of cables, two of which are high-side cables actuatable by the high-side motors and two of which are low-side cables actuatable by the low-side motors. The high-side cables are used to close the first and second jaw members and the low-side cables are used to open the first and second jaw members. The system also includes a controller for determining whether one of the low-side cables is broken based on a derivative of jaw angle between the first and second jaws exceeding a jaw angle derivative threshold and a sum of motor torques of the high-side motors exceeding combined high-side torque threshold.