Parallel-Kinematic Joint Layout for High-Stiffness Manipulators
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Solution Overview
Problem
Existing parallel kinematic machines (PKMs) used for applications like aerospace components and long vehicles are heavy, costly, and limited by low stiffness, speed, and controllability, with linear delta machines failing to meet application requirements due to suboptimal platform designs.
Innovation Solution
A method for determining the placement of support-platform joints in PKMs to optimize stiffness by evaluating kinematic and elasticity models, adjusting joint placements to meet application criteria, and using mechanical interfaces to enhance stiffness, allowing for lightweight, modular, and high-stiffness designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If serial kinematics manipulators are used to achieve high stiffness, then stiffness is improved, but weight increases and speed/acceleration are limited
Solution Approach 1:
The manipulator is divided into multiple independent parallel linkages (first support linkage, second support linkage, third support linkage) that work together to support the platform. Each linkage is lighter than a monolithic serial structure, achieving weight reduction while maintaining overall stiffness through the parallel configuration.
Solution Approach 2:
The patent transitions from static serial kinematics to dynamic parallel kinematics, where multiple carriages move independently along separate paths. This dynamic parallel structure enables faster acceleration and speed while maintaining stiffness through the coordinated action of multiple support linkages.
2Adaptability or versatility
If traditional linear delta machines are used, then modularization is achieved, but stiffness is insufficient for high-precision applications
Solution Approach 1:
The patent optimizes the local quality of the platform by introducing a three-dimensional configuration with support links extending in multiple directions (first, second, and third support linkages) rather than a simple flat platform. This local structural enhancement at the platform level significantly improves overall stiffness while preserving modularization.
Solution Approach 2:
The invention transitions from a two-dimensional flat platform to a three-dimensional platform structure with support links arranged in multiple spatial dimensions. This dimensional expansion allows for optimized stiffness characteristics in multiple directions while maintaining the modular parallel kinematic architecture.
3Ease of manufacture
If support-platform joints are placed suboptimally, then manufacturing is simplified, but stiffness and precision are reduced
Solution Approach 1:
The patent applies preliminary action by using computational optimization methods to determine the optimal placement of support-platform joints before manufacturing. The stiffness optimization model calculates precise joint locations that maximize platform stiffness, and this pre-planned optimal configuration is then implemented in the manufacturing process, achieving high precision without complicating manufacturing.
Data Source
AI summary
A method for determining placement of support-platform joints (8a, 9a, 10a, 11a, 12a, 13a) on a support-platform (17) of a parallel kinematic manipulator, PKM. The PKM comprises: the support-platform (17), a first support linkage (SL1), a second support linkage (SL2) and a third support linkage (SL3). The first support linkage (SL1), the second support linkage (SL2) and the third support linkage (SL3) together comprises at least five support-links (8, 9, 10, 11, 12, 13). The method comprises estimating (S1) parameters indicative of stiffness for the PKM, based on a kinematic model and an elastic model of the PKM and chosen defined forces and/or torques applied to a tool (22) during a processing sequence, and checking (S2) whether the estimated parameters indicative of stiffness of the PKM fulfill one or more stiffness criteria. Upon the estimated parameters indicative of stiffness fulfilling one or more stiffness criteria, the method comprises choosing (S3) the current placement configuration as an optimal placement configuration of the support-platform joints. The disclosure also relates to a system comprising a computer configured to perform the method and to output an optimal placement configuration, and a PKM with support-platform joints that are placed to the support-platform according to the optimal placement configuration outputted by the computer. The disclosure also relates to PKMs with support-platform joints that are placed to the support-platform to achieve high stiffness.