Robot Arm Wrist Gear Layout for Compact High-Torque Packaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Designing a robot arm wrist that balances compactness, high torque transfer, stiffness, and accurate sensor integration is challenging, as existing designs often compromise on these criteria, particularly in fitting motors, gearing, torque sensors, and position sensors within a small, circularly symmetrical space.
Innovation Solution
The robot arm incorporates a joint mechanism with sector gears and bevel gears, a torque sensor arrangement featuring a deflectable body with a bushing for precise torque measurement, and a rotary position sensor system using magnetic rings and sensors for accurate position tracking, allowing for compact and efficient packaging of motors and sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional gears are used in the wrist, then torque transfer is achieved, but the size of the distal portion increases and circular symmetry is compromised
Solution Approach 1:
The gear system is segmented into sector gears that engage only during specific ranges of motion of each joint. This allows the gears to be positioned off-center and packaged more compactly within the wrist, maintaining circular symmetry while providing sufficient torque transfer during operational ranges.
Solution Approach 2:
The patent positions gear elements in three-dimensional space around the rotation axes, using radial and axial arrangements to achieve compact packaging. The sector gears are disposed at specific angles and distances from the axes, utilizing spatial dimensionality to maintain symmetry while enabling torque transfer.
2Volume of moving object
If the distal portion is made compact, then multiple robot arms can work in close proximity, but it becomes difficult to fit motors and gearing
Solution Approach 1:
The patent nests multiple functional components within the compact distal portion, including positioning motors, sector gears, torque sensors, and position sensors in a nested arrangement around the rotation axes. This allows all necessary components to be integrated within a small volume while maintaining accessibility and functionality.
Solution Approach 2:
Components are arranged in three-dimensional space around the rotation axes, utilizing radial, axial, and angular dimensions to package motors, gears, and sensors efficiently. This spatial arrangement enables compact packaging while maintaining the mechanical and sensing functions.
3Force
If high torque is delivered by the joints, then heavier tools can be carried, but the distal portion becomes heavier
Solution Approach 1:
The gear system uses sector gears that engage only during specific operational ranges, allowing for more efficient torque transmission with lighter components. The segmented engagement reduces the size and weight of gear elements compared to full-circle gears, while still providing the necessary torque for heavy tools.
4Force
If conventional gear arrangements are used, then torque transfer is achieved, but backlash and elasticity increase
Solution Approach 1:
The patent designates specific gear teeth as sacrificial elements that can be replaced or reset, while other teeth maintain precision engagement. This local differentiation allows for backlash compensation without compromising the overall stiffness of the gear train, and prevents wear particles from affecting the entire system.
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 configuration enables a compact, lightweight, and highly accurate robot arm wrist capable of delivering high torque with minimal backlash, while providing precise position and torque sensing, enhancing the range of surgical procedures that can be performed.
Implementation Method 1
a torque sensor arrangement featuring a deflectable body with a bushing for precise torque measurement
Implementation Method 2
a rotary position sensor system using magnetic rings and sensors for accurate position tracking
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A robot arm comprising a joint mechanism for articulating one limb of the arm relative to another limb of the arm about two non-parallel rotation axes, the mechanism comprising: an intermediate carrier attached to a first one of the limbs by a first revolute joint having a first rotation axis and to a second one of the limbs by a second revolute joint having a second rotation axis; a first drive gear disposed about the first rotation axis and fast with the carrier, whereby rotation of the carrier relative to the first limb about the first rotation axis can be driven; a second drive gear disposed about the second rotation axis and fast with the second one of the limbs, whereby rotation of the second one of the limbs about the second rotation axis relative to the carrier can be driven; at least one of the first and second drive gears being a sector gear. At least part of one of the drive gears intersects a circle about the axis of the other one of the drive gears that is coincident with the radially outermost part of said other one of the drive gears.