Rotatable Wrist Assembly for Surgical Robot Gripper Control
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Solution Overview
Problem
Existing surgical robotic systems lack the capability to perform precise manipulations required for minimally invasive procedures due to the inability to produce instrument roll about the gripper axis, limiting their application in micro-surgery.
Innovation Solution
A continuum robot with a rotatable wrist assembly that integrates axial rotation, selective detachability, and roll-yaw-pitch capabilities, utilizing a flexible wire rope and actuation mechanism to enable precise movement and connection to the gripper, allowing for independent control of multiple degrees of freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional surgical robotic system is used, then the system structure is simple, but it lacks the capability to perform precise manipulations and produce instrument roll about the gripper axis
Solution Approach 1:
The wrist assembly is divided into multiple independent rotational segments (pitch, yaw, roll joints) that can be controlled separately. Each segment is actuated by dedicated wire ropes passing through guide pulleys, allowing precise independent control of each degree of freedom while maintaining a manageable overall structure
Solution Approach 2:
The wrist assembly employs a nested configuration where the roll joint is positioned inside the yaw joint, which is in turn positioned inside the pitch joint. This nested arrangement allows multiple rotational degrees of freedom to be compactly integrated without significantly increasing the external footprint or overall system complexity
2Adaptability or versatility
If a rotatable wrist assembly with multiple degrees of freedom is added, then the dexterity and manipulation capability are improved, but the device complexity increases
Solution Approach 1:
The wire rope actuation system serves multiple functions: it actuates the pitch joint, then continues to actuate the yaw joint, and finally the roll joint through the nested configuration. This multi-functional use of the wire rope system reduces the need for separate actuation mechanisms for each degree of freedom, thereby reducing overall system complexity while maintaining high dexterity
Solution Approach 2:
Guide pulleys are introduced as intermediary elements to route and redirect the wire ropes between different joints. These pulleys simplify the mechanical linkage by providing clear geometric paths for the wire ropes, making the complex multi-DOF actuation system more manageable and easier to control
3Ease of operation
If a continuum robot with tubular shafts is used, then the robot can navigate complex pathways, but the actuation pathway for the gripper and wrist becomes constrained
Solution Approach 1:
The wire ropes are routed through the hollow interior of the tubular shafts, utilizing the internal volume of the continuum robot structure. This three-dimensional routing through the shaft interiors allows actuation lines to reach the distal wrist assembly without interfering with the bending mechanics of the continuum segments, effectively using the internal dimension of the shafts to resolve the actuation pathway problem
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
Enables precise and coordinated motion necessary for micro-surgical procedures by providing a rotatable wrist assembly that enhances the dexterity of surgical robots, allowing for more complex and precise manipulations.
Implementation Method 1
Linear movement of the actuator causes linear movement of the flexible wire loop through the shafts of the continuum robot and thus causes rotation of the wrist capstan due to friction between the flexible wire loop and the wrist capstan
Implementation Method 2
the wire does not make a full turn around the capstan and torque transmission to the capstan relies on the positive lock between the spherical feature and the capstan rather than on friction between the wire rope and the capstan
Data Source
AI summary
A rotatable wrist connecting a gripper tool to the distal end of a positioning shaft. The rotatable wrist includes a wrist hub that is non-rotatably connected to the distal end of the shaft. A wrist capstan is rotatably connected to the wrist hub and non-rotatably connected to an actuatable device (e.g., a gripper). A flexible wire loop extends through the wrist hub and partially contacts the wrist capstan. Linear movement of the flexible wire loop through the shaft causes rotation of the wrist capstan due to friction between the flexible wire loop and the wrist capstan. The wrist also supports selective detachability and control of roll, pitch and roll, pitch yaw and roll according to different embodiments.