Multi-Motor Surgical Tool Actuator for Cable Resistance Control
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Solution Overview
Problem
Robotic surgery systems face challenges in achieving precise motion control of surgical tools, particularly in overcoming the mechanical resistance of twisted cables and maintaining reliability and durability in a compact form.
Innovation Solution
A multi-motor actuator and controller system is employed, featuring at least two input shafts coupled through a transmission to drive an output shaft. This system includes a primary motor subsystem and secondary motor subsystems that work together to overcome resistance, with a digital controller managing motor inputs based on position error and using impedance control to provide torque assist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a single motor actuator is used to drive the surgical tool, then the device complexity is reduced, but the torque capacity is insufficient to overcome the mechanical resistance of twisted cables
Solution Approach 1:
The patent combines multiple motor actuators (first motor actuator and second motor actuator) into a single integrated actuator assembly that drives the output shaft together. The motor actuators are coupled through a transmission mechanism to simultaneously drive the output shaft, merging their torque outputs to overcome the mechanical resistance of twisted cables while maintaining a unified control structure.
Solution Approach 2:
The actuator is segmented into multiple independent motor subsystems, each with its own motor actuator and control channel. This segmentation allows each motor to contribute independently to the total torque output, enabling the system to overcome high mechanical resistance while maintaining modularity and manageable complexity in the control architecture.
2Force
If the actuator is designed with high torque capacity to overcome cable resistance, then the force capability is improved, but the actuator size increases and compact profile is lost
Solution Approach 1:
Multiple motor actuators are merged into a compact integrated assembly where they share common mechanical elements such as the output shaft and transmission mechanism. This merging allows the system to achieve high torque capacity through combined output while maintaining a compact overall footprint, as the motors work together rather than requiring separate drive mechanisms.
Solution Approach 2:
The motor actuators and transmission components are nested within each other in a compact arrangement. The motors are positioned to share space efficiently, with their rotational outputs combined through the transmission mechanism to drive the output shaft. This nesting approach maximizes torque density while minimizing the overall actuator volume.
3Volume of moving object
If a compact actuator design is used to maintain small profile, then the device size is reduced, but the torque capacity becomes insufficient to overcome mechanical resistance
Solution Approach 1:
The compact actuator design merges multiple motor actuators into a single integrated unit, where their combined torque output compensates for the reduced size. By combining the rotational outputs of multiple motors through a shared transmission and output shaft, the system achieves sufficient torque capacity within a compact form factor suitable for simultaneous use with other surgical tools.
4Reliability
If multiple motor subsystems are used to provide torque assist, then the reliability is improved through redundancy, but the device complexity increases
Solution Approach 1:
Multiple motor subsystems are merged into a coordinated control system where they operate together to drive the output shaft. The control system combines feedback from multiple sources and coordinates the motor actuators to work as a unified system, improving reliability through redundancy while managing complexity through integrated control architecture that treats the multiple motors as a coordinated team rather than independent systems.
Data Source
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AI summary
A first input coupling and a second input coupling are coupled to rotatably drive an output coupling at the same time. In one embodiment, the output coupling rotates a robotic surgery endoscope about a longitudinal axis of the output coupling. A first motor drives the first input coupling while being assisted by a second motor that is driving the second input coupling. A first compensator produces a first motor input based on a position error and in accordance with a position control law, and a second compensator produces a second motor input based on the position error and in accordance with an impedance control law. In another embodiment, the second compensator receives a measured torque of the first motor. Other embodiments are also described and claimed.