Robotic Joint Gear Packaging for Compact High-Torque Wrist Motion
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Solution Overview
Problem
Existing robot arm designs face challenges in balancing the requirements of compact size, high torque, light weight, smooth motion, and accurate sensor readings, particularly in the wrist joint, as existing designs often compromise one or more of these criteria.
Innovation Solution
A surgical robot arm design featuring a first and second arm segment coupled by non-parallel, intersecting revolute joints with a joint mechanism that includes hypoid gears and an intermediary gear arrangement, allowing for independent articulation about two perpendicular axes without the need for universal joints, thus optimizing space and motion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional motor and gear arrangements are used in the wrist, then high torque can be achieved, but the size and weight of the robot arm increase
Solution Approach 1:
The drive mechanism is segmented into multiple independent modules: a first drive shaft with first drive gear for the first revolute joint, and a second drive shaft with second drive gear for the second revolute joint. Each module can be independently optimized for torque transmission while minimizing weight, allowing high torque capability without requiring a single oversized drive system.
Solution Approach 2:
The patent transitions from traditional planar gear arrangements to a three-dimensional configuration where drive shafts extend along the longitudinal axes of arm segments, and gears are positioned in multiple spatial planes. This dimensional arrangement allows compact packaging of high-torque transmission components within the wrist volume without increasing overall arm weight.
2Volume of moving object
If compact wrist design is implemented, then robot arm size is reduced, but space for motors and gearing is limited
Solution Approach 1:
The joint mechanism employs nested gear arrangements where intermediate gears are positioned within the space between drive shafts and driven gears. The first and second intermediate gears are arranged to engage with both drive shafts and driven gears in a compact nested configuration, maximizing space utilization within the constrained wrist volume without increasing mechanism complexity.
Solution Approach 2:
Intermediate gears serve as mediators that transfer motion between non-parallel drive shafts and driven gears. The first and second intermediate gears facilitate this transfer in a compact arrangement, enabling complex motion transmission within the limited space of the wrist joint without requiring additional complex mechanisms.
3Adaptability or versatility
If non-parallel intersecting rotation axes are used, then motion range is improved, but gear packaging becomes more difficult
Solution Approach 1:
Intermediate gears act as mediators that bridge the motion transmission gap between non-parallel intersecting rotation axes. The first and second intermediate gears are specifically configured to engage with drive shafts and driven gears at appropriate angles, enabling smooth motion transfer across non-parallel axes while maintaining a compact and manageable gear packaging arrangement.
Solution Approach 2:
The motion transmission system is segmented into distinct stages: first drive shaft to first driven gear, second drive shaft to second driven gear, with intermediate gears providing the necessary angular transitions. This segmentation allows each component to be optimized for its specific function while collectively achieving the desired motion range with manageable complexity.
Data Source
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AI summary
A robot arm comprising a first arm segment and a second arm segment coupled to each other by a first revolute joint having a first rotation axis and a second revolute joint having a second rotation axis non-parallel to the first rotation axis, and a joint mechanism for articulating the first arm segment relative to the second arm segment about the first and second rotation axes, the joint mechanism comprising: a first driven gear disposed about an axle coincident with the first rotation axis, the axle being fast with a first arm segment of the robot arm; a second driven gear disposed about the second rotation axis and fast with a second arm segment of the robot arm and fast with the first driven gear about the first rotation axis; a first drive gear configured to drive the first driven gear to rotate about the axle, the first drive gear being arranged to engage the first driven gear; a second drive gear for driving the second driven gear to rotate about the second rotation axis; and an intermediary gear arrangement arranged to engage the second drive gear and the second driven gear and being disposed about the first rotation axis, whereby rotation of the intermediary gear arrangement relative to the first arm segment about the first rotation axis can be driven.