Cable Band Drive for Robotic Surgical Tool Cable Retention
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Solution Overview
Problem
Robotic surgical systems face challenges with drive cable derailment and slackening during operations, which can affect the precision and reliability of surgical instruments.
Innovation Solution
The implementation of a cable band system that wraps around an input shaft instead of the drive cables, providing constant torque resistance and preventing derailment by maintaining tension through a constant force spring mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If drive cables are used to articulate the end effector, then the system achieves flexibility and range of motion, but the drive cables are prone to derailment and slackening
Solution Approach 1:
A cable band is introduced as an intermediary component between the drive cable and the input shaft. The cable band wraps around the input shaft and connects to the drive cable, serving as a mediator that prevents the drive cable from directly contacting and potentially derailing from the input shaft. This intermediary element maintains the functional connection while eliminating the derailment risk.
Solution Approach 2:
The cable-driven articulation system is segmented into distinct functional components: the drive cable, the cable band, and the input shaft. By separating the functions of force transmission (drive cable) and rotational engagement (cable band around input shaft), the system achieves both flexibility and reliability. The cable band acts as a separate element that ensures proper cable routing and tension maintenance.
2Force
If the drive cable is wrapped around the input shaft to provide torque resistance, then the system achieves mechanical advantage, but the drive cable may derail from the input shaft
Solution Approach 1:
The cable band serves as an intermediary that provides the wrapping function around the input shaft. Instead of the drive cable itself being wrapped around the shaft (which risks derailment), the cable band performs this function and connects to the drive cable. This mediator maintains the mechanical advantage through friction and normal force while preventing direct contact between the drive cable and shaft.
Solution Approach 2:
The cable band replicates the functional characteristics of a wrapped cable (providing torque resistance through friction) without using the actual drive cable for wrapping. The cable band is a separate element that copies the beneficial mechanical effect of cable wrapping while eliminating the harmful derailment risk.
3Reliability
If a constant force spring mechanism is added to maintain cable tension, then the system achieves prevention of cable slackening, but the device complexity increases
Solution Approach 1:
The constant force spring mechanism is integrated into the cable band assembly, allowing the system to self-regulate cable tension. The spring automatically maintains constant tension on the cable band as it wraps and unwraps from the input shaft, eliminating cable slackening without requiring external active control systems. The mechanism serves itself by using the spring's inherent elastic properties to maintain tension.
Solution Approach 2:
The constant force spring mechanism is merged with the cable band structure. Rather than being a separate, complex active control system, the spring is integrated into the passive cable band assembly, combining the tension maintenance function with the existing cable routing mechanism. This integration minimizes added complexity while achieving reliable tension consistency.
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 solution effectively mitigates drive cable derailment and slackening, ensuring consistent and predictable performance of surgical instruments by maintaining tension and preventing cable displacement during robotic surgical procedures.
Implementation Method 1
maintaining tension through a constant force spring mechanism
Implementation Method 2
providing constant torque resistance
Data Source
Figure 1
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AI summary
A surgical tool includes a drive housing having an input shaft arranged therein for rotation, an elongate shaft that extends from the drive housing, and an end effector operatively coupled to a distal end of the elongate shaft. A cable band is coupled to the input shaft and operatively couples the input shaft to a drive cable that extends to the end effector. Rotation of the input drive correspondingly moves the cable band and thereby controls longitudinal movement of the drive cable to articulate the end effector.