Concentric Multi-Axis Actuator with Cross Roller Bearing
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Solution Overview
Problem
Concentric multi-axis actuators with longer rotary output shafts suffer from lower concentricity and increased axial oscillations, which also result in lower moment stiffness, and adding bearings to mitigate these issues often requires longer shafts, complicating space installation.
Innovation Solution
A concentric multi-axis actuator design featuring a multi-stage cross roller bearing with a preceding-stage actuator and a subsequent-stage actuator, where the subsequent-stage actuator has a hollow design allowing the rotary output shaft to project forward through the preceding-stage actuator's hollow section, and utilizing strain wave gear reducers for efficient rotation transfer, with specific roller size and offset configurations to minimize precompressive deformation and enhance moment stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the rotary output shaft of the subsequent stage-side actuator passes through the hollow section of the preceding stage-side actuator and projects frontward, then the concentric multi-axis actuator can achieve compact concentric arrangement, but the axial length of the rotary output shaft increases, resulting in lower concentricity and greater axial oscillations
Solution Approach 1:
The patent applies nesting by placing the subsequent stage actuator inside the hollow section of the preceding stage actuator, with the rotary output shaft passing through the hollow section and projecting frontward. This nested arrangement achieves compact concentric multi-axis actuator design while managing the challenges of increased axial length through additional bearing support.
2Productivity
If the rotary output shaft has longer axial length, then the concentric multi-axis actuator can accommodate multiple stages, but the moment stiffness decreases and axial oscillations increase
Solution Approach 1:
The patent introduces an additional bearing as an intermediary component to support the rotary output shaft at multiple positions along its axial length. This bearing acts as a mediator to provide necessary support and stability, preventing excessive deflection and maintaining moment stiffness despite the increased shaft length required for multi-stage configuration.
3Reliability
If a bearing is added to support the rotary output shaft to minimize axial oscillation and increase moment stiffness, then the rotational stability improves, but the axial length must be extended further to ensure installation space
Solution Approach 1:
The patent merges the support function into the existing actuator structure by integrating the additional bearing within the hollow section of the preceding stage actuator. This combining approach provides necessary rotational stability and moment stiffness support while utilizing the available space efficiently, avoiding excessive extension of the overall axial length.
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 design minimizes surface oscillations and increases moment stiffness by effectively supporting rotary output elements with the multi-stage cross roller bearing, allowing for more compact and stable rotary output mechanisms.
Implementation Method 1
a multi-stage cross roller bearing; an annular outside track of rectangular cross section formed between the outer ring and the middle ring, a plurality of outside rollers rollably inserted within the outside track, an annular inside track of rectangular cross section formed between the middle ring and the inner ring, and a plurality of inside rollers rollably inserted within the inside track
Data Source
AI summary
A concentric double axis actuator has a two-stage cross roller bearing, and a preceding-stage actuator and a subsequent-stage actuator which are linked in tandem. The front end of a subsequent stage rotary output shaft of the subsequent actuator, said subsequent stage rotary output shaft passing through a hollow section of the preceding-stage actuator and projecting forward, is linked and fixed to an inner ring of the two-stage cross roller bearing, and the inner ring functions as a subsequent-stage rotary output member. The output rotary side of the preceding-stage actuator is linked to an middle ring of the two-stage cross roller bearing, which functions as a preceding-stage rotary output member. The rotary output element of each stage is supported by the two-stage cross roller bearing, and surface oscillations of the rotary output member of each stage can be minimized, and the moment stiffness of the members can be increased.