Preloaded Instrument Coupling for Zero-Backlash Surgical Motion
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Solution Overview
Problem
Robotically controlled surgical systems face challenges with backlash in their drive mechanisms, leading to unpredictable motion of surgical instruments during installation, which can be detrimental in precise medical procedures.
Innovation Solution
A surgical instrument manipulator assembly with a low backlash mechanical interface, utilizing a drive output disk with alignment elements and preload springs to ensure zero backlash for torque levels used in surgical procedures, thereby stabilizing instrument movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical interface with gears or disks is used to couple the drive system to the surgical instrument, then the system can transmit torque and motion, but backlash occurs leading to unpredictable instrument motion
Solution Approach 1:
The mechanical interface transitions from a static engagement to a dynamic preload mechanism. A spring applies continuous axial force to press the drive disk against the driven disk, eliminating gaps and ensuring consistent contact. This dynamic adjustment maintains zero backlash throughout operation, resolving the unpredictability issue while preserving torque transmission capability.
Solution Approach 2:
The invention changes the physical state of the mechanical interface by introducing preload force. By applying axial pressure through a spring mechanism, the interface parameters (contact force, gap distance) are modified to eliminate backlash. This parameter change transforms the mechanical coupling from loose to tight, ensuring predictable motion transmission without sacrificing torque capacity.
2Reliability
If the drive motors are rotated back and forth multiple times during installation to ensure engagement, then the complementary features can mesh securely, but the surgical instrument moves in an unpredictable manner
Solution Approach 1:
The preload mechanism is activated before final instrument installation and motor rotation. By pre-applying axial force to secure the mechanical interface, the system eliminates the need for multiple trial rotations during installation. The preliminary preload ensures that when motors are rotated, the drive and driven features are already in stable, predictable engagement, preventing unexpected instrument movement.
3Reliability
If a sterile barrier is interposed between the docking port and instrument backend, then sterilization is maintained, but the mechanical interface complexity increases
Solution Approach 1:
The drive disk is designed with dual functionality: it serves as both the torque transmission element and the sterile interface component. By integrating the sterile barrier attachment directly onto the drive disk structure, the invention eliminates the need for separate sterile adaptors and complex coupling mechanisms. This universal design maintains sterilization while simplifying the overall mechanical interface.
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 solution effectively minimizes backlash, ensuring precise and predictable transmission of torque and position to surgical instruments, enhancing the reliability and accuracy of robotic surgical systems.
Implementation Method 1
A first preload spring coupled to the drive output disk... When the first preload spring is compressed, the first preload spring applies a first preload force to the drive output disk
Implementation Method 2
A second preload spring coupled to the drive output disk... When the second preload spring is compressed, the second preload spring applies a second preload force to the drive output disk
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A surgical system (200) includes a surgical instrument (260) that is sensitive to backlash that would adversely affect the transmission of controlled torque and position to the surgical instrument. The surgical instrument (260) is coupled to motors in a surgical instrument manipulator assembly (240) via a mechanical interface. The combination of the mechanical interface and surgical instrument manipulator assembly (240) have low backlash, e.g., less than 0.7 degrees. The backlash is controlled in the surgical instrument manipulator assembly (240). From the drive output disk (545) in the surgical instrument manipulator assembly to the driven disk (964) of the surgical instrument, the mechanical interface has zero backlash for torque levels used in surgical procedures.