2T2R Parallel Mechanism for Automated Fiber Placement
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Solution Overview
Problem
Current automated fiber placement (AFP) systems in aerospace manufacturing rely on serial robots, which have low stiffness and high inertia, limiting their performance in high-compact-force applications due to their serially connected structure, whereas parallel robots offer higher stiffness and precision but are not widely used in AFP due to complexity and cost constraints.
Innovation Solution
A 2T2R parallel mechanism with a 2RPS-2UPS topology is introduced, featuring two RPS limbs and two UPS limbs, optimizing the location of UPS limbs to achieve a large singularity-free workspace and good kinematics performance, allowing for efficient fiber placement with a moving base and rotating spindle, and potentially expanding to 6-DOF systems for complex part manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If serial robots are used for AFP systems, then ease of operation and availability are improved, but stiffness and precision deteriorate
Solution Approach 1:
The patent inverts the conventional serial robot architecture by adopting a parallel mechanism architecture for the AFP system. This inversion transforms the kinematic chain from serial to parallel, fundamentally changing the structural characteristics to achieve both high stiffness and operational capability simultaneously
2Manufacturing precision
If parallel robots are used for AFP systems, then stiffness and precision are improved, but device complexity increases
Solution Approach 1:
The parallel mechanism is segmented into distinct functional modules: a moving base providing translational motion, a platform for mounting the AFP head, and multiple independent limbs (RPS and UPS configurations). This segmentation allows each module to be optimized independently while maintaining overall system precision and managing complexity through modular design
3Adaptability or versatility
If a 6DOF platform is used for AFP operation, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent implements a 4DOF parallel mechanism (2T2R: two translations and two rotations) which provides sufficient adaptability for most AFP applications without the full complexity of a 6DOF system. The moving base adds one translation and the AFP head rotation adds one more degree of freedom, achieving partial action that balances adaptability with manageable complexity
Data Source
AI summary
The present invention introduces a new concept of applying a parallel mechanism in automated fiber placement for aerospace part manufacturing. The proposed system requirements are 4DOF parallel mechanism consisting of two RPS and two UPS limbs with two rotational and two translational motions. Both inverse and forward kinematics models are obtained and solved analytically. Based on the overall Jacobian matrix in screw theory, singularity loci are presented and the singularity-free workspace is correspondingly illustrated. To maximize the singularity-free workspace, locations of the two UPS limbs with the platform and base sizes are used in the optimization which gives a new design of a 4DOF parallel mechanism. A dimensionless Jacobian matrix is also defined and its condition number is used for optimizing the kinematics performance in the optimization process. A numerical example is presented with physical constraint considerations of a test bed design for automated fiber placement.