Singularity-Free Parallel Mechanism Architecture
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Solution Overview
Problem
Parallel architecture mechanisms with kinematic chains face complexity in control, leading to high computing power requirements and issues with rigidity singularities, which restrict the pointing domain and can result in mechanism blocking or faults, especially in vehicles like space systems where real-time control is challenging.
Innovation Solution
The mechanism features non-concurrent base and mobile axes with different radii for the minimum theoretical spheres or circles, eliminating rigidity singularities and improving rigidity, allowing control without complex real-time calculations by using open-loop control with pre-recorded tables, and is adapted for use on vehicles like space systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If parallel architecture mechanism with kinematic chains is used, then position control and movement according to multiple degrees of freedom is achieved, but control complexity increases requiring very significant computing power
Solution Approach 1:
The patent pre-calculates and stores control equations and their solutions in lookup tables before real-time operation. During actual control, the system simply retrieves pre-computed values based on current configuration, avoiding complex real-time calculations while maintaining accurate position control across multiple degrees of freedom
2Device complexity
If conventional parallel architecture mechanism geometry is used, then mechanism structure is simplified, but rigidity singularities occur restricting the pointing domain
Solution Approach 1:
The patent introduces asymmetric geometric parameters in the mechanism configuration, specifically using different lengths for base arms versus mobile forearms and offsetting the intersection points of base axes from the mobile position. This asymmetric design breaks the symmetry that causes rigidity singularities in conventional parallel mechanisms, eliminating singularities within the working space while maintaining structural simplicity
3Device complexity
If open-loop control with pre-recorded tables is used, then computing power requirements are reduced, but trajectories cannot be controlled or optimized and may go outside the pointing range
Solution Approach 1:
The patent implements a hybrid control approach where pre-calculated lookup tables provide baseline control with low computing requirements, while additional feedback mechanisms monitor the actual mechanism state and provide corrections. This ensures trajectories remain within the valid pointing range and allows for optimization while maintaining reduced computing power requirements compared to full real-time control
Data Source
Figure 1~2
Figure 3a~3c
AI summary
The invention concerns a mechanism with parallel architecture comprising at least three kinematic chains (13a, 13b, 13c) interposed between a stand (11) and a movable member (12), including three kinematic chains (13a, 13b, 13c) each comprising a base arm hinged to the stand (11), and a base actuator (16a, 16b, 6c) controlling the base angle of the base arm. The movements of each actuator are controlled to move the movable member (12) relative to the stand (11). The base ends (45a, 45b, 45c) and the movable member ends (46a, 46b, 46c) are arranged such that a minimum theoretical sphere, referred to as the base sphere, containing the base ends, has a radius (r1) different to the radius (r2) of a minimum theoretical sphere, referred to as the movable member sphere, containing the movable member ends.