Robot Wrist Gear Layout for Compact High-Torque Sensor Integration
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Solution Overview
Problem
Designing a robot arm wrist that balances compactness, high stiffness, torque transfer, and 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
A robot arm joint mechanism featuring non-parallel rotation axes with sector gears, including bevel gears, and a carrier system that allows for compact and efficient packaging of motors, sensors, and cables, enabling high torque and stiffness while accommodating position and force/torque sensors for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional gear arrangements are used in the robot wrist, then high torque and stiffness can be achieved, but the size of the wrist increases and it cannot be made circularly symmetrical
Solution Approach 1:
The gear system is segmented into sector gears that engage only for the required portion of rotation, rather than using complete circular gears. This segmentation allows the gears to be positioned more compactly within the wrist, reducing overall wrist volume while maintaining the necessary torque and stiffness through precise engagement zones.
Solution Approach 2:
The patent employs bevel gears that transmit torque between non-parallel rotation axes, utilizing a three-dimensional spatial arrangement. This dimensional approach allows torque transmission without requiring coplanar gear arrangements, enabling a more compact and circularly symmetrical wrist configuration while preserving high torque capability.
2Measurement precision
If multiple sensors and motors are integrated into the wrist, then positioning and torque control accuracy improves, but the complexity of the wrist arrangement increases
Solution Approach 1:
Multiple functional components including motors, sensors, and cable routing are merged into a unified wrist assembly. The sector gear mechanism integrates torque transmission and positioning functions, while torque sensors and position sensors are incorporated directly into the joint structure, reducing the number of separate components and simplifying the overall arrangement.
Solution Approach 2:
The wrist joint mechanism serves multiple functions simultaneously: the sector gears provide both torque transmission and position encoding, torque sensors measure both magnitude and direction of forces, and the compact arrangement accommodates cable routing, motor actuation, and sensor measurement within a single integrated structure, reducing overall system complexity.
3Volume of moving object
If the distal portion of the arm is made compact and circularly symmetrical, then multiple robot arms can work in close proximity, but it becomes difficult to fit motors and gearing for high torque
Solution Approach 1:
The patent utilizes bevel gears to transmit torque between non-parallel axes, exploiting three-dimensional spatial relationships within the compact distal portion. This allows motor shafts and gear mechanisms to be arranged along different axes rather than requiring coplanar layouts, fitting high-torque components into a smaller, circularly symmetrical volume.
Solution Approach 2:
The gear train is divided into sector gears with limited engagement arcs, allowing each gear segment to be optimized for specific torque transmission requirements. This segmentation enables more efficient packing of gear components within the compact distal portion while maintaining the necessary power transmission capability through precise angular engagement.
Data Source
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AI summary
A robot arm comprising a joint mechanism for articulating one limb (310) of the arm relative to another limb (311) of the arm about two non-parallel rotation axes (20, 21), the mechanism comprising: an intermediate carrier (28) 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 (33) 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 (37) 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.