Robot Joint Rotational Structure With Internal Optical Encoder
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Solution Overview
Problem
Existing rotational structures for robots, such as those used in care robots and exoskeletons, face issues with encoder malfunction due to external forces, require a compact and lightweight design, and struggle with easy separation and coupling with other members while maintaining positioning accuracy.
Innovation Solution
A rotational structure with an encoder integrated inside, utilizing a hollow portion around the shaft member and an optical encoder with a reflective or transmission scale, which reduces the risk of malfunction from external forces and eliminates the need for additional components, allowing for compact and lightweight construction with accurate rotation angle detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the encoder is provided outside the movable part of the joint structure, then the thickness of the encoder can be reduced, but the encoder has high possibility of malfunction when external force is applied
Solution Approach 1:
The encoder is nested inside the movable part of the joint structure, specifically utilizing the hollow portion of the shaft member. The detection target member is mounted on the rotational member inside the hollow portion, and the detector is mounted on the base member, creating a protected internal encoder configuration that eliminates the risk of external force damage while maintaining compact dimensions.
2Volume of moving object
If the encoder is provided outside the movable part, then the encoder thickness is reduced, but the joint structure size increases in the axial direction
Solution Approach 1:
The encoder components are nested within the hollow portion of the shaft member, utilizing existing internal space rather than adding external components. This allows the detector and detection target member to be positioned axially within the existing joint structure boundaries, avoiding axial length increase.
Solution Approach 2:
The encoder is repositioned from an external axial arrangement to an internal radial arrangement within the hollow portion. By mounting the detection target member on the rotational member and the detector on the base member, the encoder operates in the radial dimension of the hollow portion rather than extending axially outward.
3Reliability
If a separate bearing component is provided for the encoder, then the encoder is protected from stress, but the number of components and assembly steps increases
Solution Approach 1:
The encoder detection system is merged with the existing joint structure components. The detection target member is integrated with the rotational member, and the detector is integrated with the base member. The hollow portion of the shaft member serves as the encoder housing, eliminating the need for separate encoder bearing components while the existing bearing (16) protects both the rotational member and the encoder.
Solution Approach 2:
The existing bearing (16) and hollow portion structure serve multiple functions: supporting the rotational member and simultaneously protecting the encoder components. The base member and rotational member serve dual roles as both structural components and encoder mounting surfaces, reducing the total component count.
4Manufacturing precision
If positioning pins are used for accurate positioning in separatable joint structure, then coupling accuracy is achieved, but processing steps and assembly steps increase
Solution Approach 1:
The coupling structure merges the positioning function with the existing coupling surface. The coupling surface (32) on the rotational member integrates positioning features directly into the coupling interface, eliminating the need for separate positioning pins. The groove portion and projection portion work together as an integrated positioning and coupling mechanism.
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 significantly reduces the likelihood of encoder malfunction, achieves a compact and lightweight structure, and enables secure and accurate coupling with other members, enhancing the robustness and efficiency of the rotational structure.
Implementation Method 1
a circuit board having a main surface provided with an optical sensor which transmits and receives light to detect a rotational state of the disc part to and from the disc part
Implementation Method 2
an optical encoder including a reflective scale and a detection element, in a hollow portion, in which the base member is opposed to the rotational member
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A rotational structure (10) comprises a base member (11), a shaft member (12) and a rotational member (13). The shaft member (12) includes one end fixed to the base member (11) and extends in an axial direction of the rotational structure (10). The rotational member (13) is attached to the shaft member (12) through a bearing (16) and configured to rotate about the shaft member (12). At least one of the base member (11) and the rotational member (13) is provided with a coupling surface (32) serving as a plane to couple a different member, in an external circumferential surface thereof in a circumferential direction of the shaft member (12). The coupling surface (32) is provided with a groove portion (32A) having a cross section with an inverted T shape.