Robot Arm Wrist Gear Train for Compact Two-Axis Torque Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Designing a robot arm wrist that balances compactness, high stiffness, and torque transfer is challenging due to the need for efficient motor and gearing integration, often compromising on one or more criteria in existing designs.
Innovation Solution
A robot arm joint mechanism featuring an intermediate carrier with revolute joints and a complex gear train system, including worm and bevel gears, allows for articulation about two non-parallel rotation axes, enabling compact and rigid drive arrangements while minimizing parasitic motion through compensatory control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If motors and gearing are integrated into the wrist to enable compact design, then the size of the distal portion is reduced, but the mechanical complexity and weight distribution become challenging
Solution Approach 1:
The drive arrangement is segmented into modular components: motors are mounted in the proximal arm part, gear trains are distributed between proximal and distal parts, and drive shafts extend through the arm. This segmentation allows compact wrist integration while maintaining manageable mechanical complexity through organized functional modules.
Solution Approach 2:
The mechanism uses two non-parallel rotation axes (first and second axes) that intersect, creating a three-dimensional articulation space. This dimensional approach allows compact packaging of multiple degrees of freedom within the wrist volume while maintaining clear separation of drive functions along different spatial dimensions.
2Adaptability or versatility
If a complex gear train system is used to achieve articulation about two non-parallel axes, then the range of motion is improved, but the device complexity increases
Solution Approach 1:
The intermediate carrier serves multiple functions: it carries the first drive gear for rotation about the first axis, carries the second drive gear for rotation about the second axis, and provides structural support for both revolute joints. This multi-functionality reduces overall system complexity by consolidating components.
Solution Approach 2:
The intermediate carrier acts as a mediator between the two rotation axes, providing a common reference frame and mechanical interface. It couples the first and second revolute joints while carrying both drive gears, simplifying the kinematic chain and reducing the complexity of coordinating two non-parallel axes.
3Force
If drive shafts extend along the limbs with shaft gears for torque transfer, then the torque transfer capability is improved, but the weight of the arm increases
Solution Approach 1:
The drive shafts are positioned to extend along specific limbs only where torque transfer is required, rather than uniformly throughout the entire arm structure. Shaft gears are placed locally at joints requiring high torque (e.g., wrist joints), allowing optimized weight distribution with reinforcement only where mechanically necessary.
Solution Approach 2:
The use of bevel gears and worm gears with conical or curved tooth surfaces enables efficient torque transfer through rotational motion. These curved gear geometries provide mechanical advantage for torque multiplication while maintaining compact shaft designs that minimize unnecessary material and weight.
4Stability of the object's composition
If multiple drive shafts and gear trains are integrated into the wrist, then the stiffness and torque delivery are improved, but the parasitic motion increases
Solution Approach 1:
The control system is configured to detect and compensate for parasitic motion generated by the gear train system. By monitoring the actual motion of the intermediate carrier and drive gears, the control system applies corrective torques through the drive shafts to counteract unwanted movements, maintaining joint stiffness and positioning accuracy.
Solution Approach 2:
Sensors are integrated into the joint mechanism to provide real-time feedback on the positions and forces at each articulation point. This feedback enables the control system to detect parasitic motion from the gear trains and adjust drive shaft torques accordingly, maintaining precise control despite the complex mechanical 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
The solution provides a compact, lightweight, and rigid drive arrangement that effectively transfers torque and maintains precise control, addressing the limitations of existing designs by enabling a wide range of motion with reduced mechanical complexity and weight distribution.
Implementation Method 1
a first drive gear disposed about the first rotation axis, the first drive gear being fast with the carrier; a second drive gear disposed about the second rotation axis, the second drive gear being fast with the second one of the limbs
Implementation Method 2
A robot arm joint mechanism featuring an intermediate carrier with revolute joints and a complex gear train system, including worm and bevel gears
Implementation Method 3
enables compact and rigid drive arrangements while minimizing parasitic motion through compensatory control
Implementation Method 4
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
Data Source
Figure 1~2
Figure 3
Figure 4
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, the mechanism comprising: an intermediate carrier (28) attached to a first one of the limbs by a first revolute joint having a pitch rotation axis (20) and to a second one of the limbs by a second revolute joint having a yaw rotation axis (21); a first drive gear (33) disposed about the pitch rotation axis, the first drive gear being fast with the carrier; a second drive gear (37) disposed about the yaw rotation axis, the second drive gear being fast with the second one of the limbs; a first drive shaft (26) for driving the first drive gear to rotate about the pitch rotation axis, the first drive shaft extending along the first one of the limbs and having a first shaft gear (32) thereon, the first shaft gear being arranged to engage the first drive gear; a second drive shaft (27) for driving the second drive gear to rotate about the yaw rotation axis, the second drive shaft extending along the first one of the limbs and having a second shaft gear (34) thereon; and an intermediate gear train (35, 38, 39) borne by the carrier and coupling the second shaft gear to the second drive gear.