Wristed Instrument Cable Tension Control for Robotic Surgery
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Solution Overview
Problem
Surgical robotic systems face challenges in precisely actuating surgical instruments due to remote operation, requiring accurate reflection of movement commands from a surgical console.
Innovation Solution
The system includes a surgical robotic arm with a drive unit and motors that adjust the end effector in a null space, using sensors to measure properties like current and torque, and a controller that limits current and torque to ensure precise instrument movement, and compensates for yaw and pitch angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If motors are activated to adjust the end effector in null space, then additional pressure can be applied without movement, but device complexity increases due to sensors and control systems
Solution Approach 1:
Sensors measure motor properties (current, torque) and feed this information back to the controller, which adjusts motor activation accordingly. This closed-loop feedback enables precise null space control while managing system complexity through intelligent regulation rather than purely mechanical solutions
Solution Approach 2:
The patent replaces traditional mechanical pressure adjustment mechanisms with an electronic control system that activates motors in null space. This substitution eliminates the need for complex mechanical linkages while achieving precise pressure control through software-based null space manipulation
2Measurement precision
If current and torque are limited during null space adjustment, then precise control is achieved, but the range of motion is restricted
Solution Approach 1:
The system dynamically adjusts current and torque limits based on real-time sensor feedback and operational context. The controller adapts the degree of limitation to achieve precise null space control when needed while allowing full range of motion when appropriate, making the system versatile across different surgical scenarios
3Manufacturing precision
If multiple sensors are used to measure motor properties, then control accuracy improves, but device complexity and cost increase
Solution Approach 1:
The sensor system is designed with multi-functionality, where sensors serve multiple purposes: measuring motor properties for control, monitoring system health, and providing feedback for calibration. This universal approach reduces the total number of components needed while maintaining high actuation precision
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 approach enables precise and controlled actuation of surgical instruments, allowing for additional pressure application without movement, improving the accuracy and safety of surgical procedures.
Implementation Method 1
each of the couplers including a drive screw and a plurality of drive nuts each of which is threadably coupled to one of the drive screws. The drive nuts are movable along the respective coupler's longitudinal axis in response to rotation of their respective drive screws.
Implementation Method 2
The drive unit includes a plurality of motors each of which is configured to engage one of the couplers and to rotate the coupler and the drive screw.
Data Source
AI summary
A surgical robotic arm includes an instrument having a plurality of cables that are movable longitudinally and an end effector movable by the cables. The surgical robotic arm also includes a drive unit having a plurality of motors each of which is configured to move one of the cables and a plurality of torque sensors, each of which is configured to measure torque output by one of the motors. The surgical robotic arm also includes a controller configured to receive a torque measurement from each of the torque sensors and control each of the motors to apply a minimum torque to maintain a minimum tension on each of the cables based on the torque measurement from each of the torque sensors.