Spherical Parallel Link Mechanism for Compact 3-DOF Posture Control
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Solution Overview
Problem
Existing parallel link mechanisms face challenges in achieving a compact construction with a wide operating range and precise movement, as they often require larger sizes due to increased link lengths and have difficulty in maintaining a fixed center of rotation for the distal end-side link hub, limiting their application in applications requiring compactness and precision.
Innovation Solution
A parallel link mechanism with a proximal end-side link hub, multiple link mechanisms, and rotating bodies, where the rotating bodies are connected to the link mechanisms and rotatably coupled to the proximal hub, with a configuration that allows the distal end-side link hub to move on a sphere around a fixed center of rotation, enabling three degrees of freedom and precise posture control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the link length is increased to achieve a large operating range of the traveling plate, then the operating range is improved, but the size of the entire mechanism and apparatus increases
Solution Approach 1:
The invention transitions from planar motion to spherical motion by introducing a fixed center of rotation in three-dimensional space. The distal end-side link hub moves on the surface of a sphere rather than in a plane, allowing the mechanism to achieve a wide operating range without increasing link lengths proportionally. This dimensional change enables compact construction while maintaining large operating range.
Solution Approach 2:
The invention employs spherical geometry by defining a fixed center of rotation and having the distal end-side link hub move along a spherical surface. This spherical configuration allows multiple degrees of freedom (three rotational degrees of freedom) within a compact volume, resolving the contradiction between operating range and mechanism size.
2Volume of moving object
If the distal end-side link hub operates in two degrees of freedom, then the mechanism is compact, but adding another degree of freedom requires an external rotation mechanism that increases device size
Solution Approach 1:
The invention merges multiple rotational degrees of freedom into a single integrated spherical mechanism. Instead of adding external rotation mechanisms for additional degrees of freedom, the spherical link mechanism inherently provides three rotational degrees of freedom (rotation around three mutually orthogonal axes passing through the fixed center of rotation) within a compact structure, eliminating the need for separate external rotation devices.
Solution Approach 2:
The distal end-side link hub serves multiple functions simultaneously: it maintains a fixed center of rotation, enables three degrees of freedom of rotation, and operates within a compact volume. This multi-functional design resolves the contradiction between device size and degrees of freedom by making the same structural element perform multiple roles.
3Adaptability or versatility
If the radius of rotation changes with bend angle, then the mechanism has flexibility, but the center of rotation cannot be fixed making operation difficult to imagine
Solution Approach 1:
The invention establishes the fixed center of rotation in advance as a predetermined geometric point in space before operation begins. All rotational movements of the distal end-side link hub are constrained to occur on the surface of a sphere centered at this pre-defined point. This preliminary establishment of the rotation center provides predictable and imaginable motion patterns while still allowing flexible operation through three degrees of freedom.
Solution Approach 2:
The invention creates an equipotential spherical surface where the distal end-side link hub moves. All positions on this spherical surface are equivalent in terms of their distance from the fixed center of rotation, providing consistent rotational characteristics regardless of the specific position or bend angle. This enables predictable motion patterns while maintaining operational flexibility.
Data Source
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AI summary
A parallel link mechanism includes a proximal end-side link hub (1), three link mechanisms (11), a rotating body (2a), and a distal end-side link hub (3). The rotating body (2a) is connected to one link mechanism among the three link mechanisms (11). The rotating body (2a) is rotatably coupled to the proximal end-side link hub (1). In the link mechanism (11), a first center axis (15a to 15c) of a first revolute pair portion (25a to 25c) intersects with a second center axis (16a to 16c) of a second revolute pair portion (26a to 26c) at a spherical link center point (30). The rotation center axis 12 of the rotating body (2a) intersects with the spherical link center point (30).