Master Controller Linkage with Redundant Degrees of Freedom
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Solution Overview
Problem
Current master controllers for robotically assisted surgery lack an input device that provides a large range of motion with minimal hand loading, leading to potential surgeon fatigue and limited precision due to mechanical constraints.
Innovation Solution
An input device featuring a handle coupled to a base via a linkage with a redundant link, which allows internal motion without moving the handle, utilizing a drive system to apply loads proportional to the cosine of the angle between the handle and redundant link axes to increase the distance between the handle and stop position, reducing the load on the handle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional linkage without redundant links is used, then the device complexity is lower, but the range of motion is limited and hand loading increases
Solution Approach 1:
The linkage is divided into multiple segments including a redundant link that can move independently. This segmentation allows the handle to achieve a broader range of motion while the redundant link absorbs mechanical constraints, preventing excessive loading on the surgeon's hand.
Solution Approach 2:
The redundant link is nested within the linkage structure, allowing it to provide internal motion without adding external bulk. The redundant link operates within the existing linkage framework, enabling enhanced adaptability while maintaining a compact overall structure.
2Ease of operation
If the handle is constrained by mechanical stops, then the device complexity is lower, but the surgeon's hand experiences increased loading and fatigue
Solution Approach 1:
The drive system acts as an intermediary between the handle stop and the redundant link. It senses when the handle approaches the stop and activates to create internal motion in the redundant link, thereby reducing the load on the surgeon's hand before the mechanical stop is fully engaged.
Solution Approach 2:
The drive system performs preliminary action by detecting the approach of the handle to the stop position and preemptively creating internal motion in the redundant link. This preliminary action reduces the load on the surgeon's hand before the mechanical constraint is fully engaged, preventing fatigue.
3Adaptability or versatility
If the linkage allows free internal motion, then the range of motion is improved, but the handle position stability deteriorates
Solution Approach 1:
The drive system incorporates feedback mechanisms that monitor the handle position and the state of the redundant link. Based on this feedback, the drive system adjusts the internal motion of the redundant link to maintain handle position stability while still allowing the benefits of redundant degrees of freedom for extended range of motion.
Data Source
AI summary
An input device includes a handle coupled to a base by a linkage. The handle is manually movable relative to the base to provide a position input. The linkage has a plurality of links including a redundant link that permits internal motion of the linkage such that the linkage can move without moving the handle relative to the base. When a distance between the handle and a handle stop position is less than a threshold distance, a handle stop applies a first load to the handle. A drive system applies a second load to the redundant link responsive to the first load to create internal motion of the linkage that increases a distance between the handle and a handle stop position. The second load may be proportional to a cosine of an angle between a handle axis of motion and a redundant link axis of motion.