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COBEM 2021
26th International Congress of Mechanical Engineering
Optimal control based on the reduced-order model of a parallel manipulator with flexible links
Submission Author:
Fernanda Thaís Colombo , SP
Co-Authors:
Fernanda Thaís Colombo, Maíra Martins da Silva
Presenter: Fernanda Thaís Colombo
doi://10.26678/ABCM.COBEM2021.COB2021-0601
Abstract
Flexible robotic systems with lightweight structures may have improved dynamic performance with high operating speeds and lower energy consumption. To address the unwanted vibration that such flexible systems may be subject to, control strategies based on their model can be crucial. In this paper, the dynamic of a parallel and planar 3RRR manipulator with flexible links is modeled in a multibody dynamics (MBD) environment using the Finite Element (FE) method. Parallel manipulators have higher positioning accuracy and payload to weight ratio than their serial counterparts, but they can present singularities in the workspace. The design of control strategies for parallel manipulators is also challenging since their configuration depends on the end-effector's pose, and they have nonlinear dynamics, especially at high speeds. Another advantage of computing an MBD model is that it allows the direct measurement of the robot's end-effector position in the Cartesian space, a complex task for parallel manipulators. However, FE models of robotic systems may have tens of thousands of degrees of freedom, used to describe the deformation of the several nodes created by the mesh. Since these large-scale models are not suitable for the control design, we applied Model Order Reduction methods to the model under study. We validated the reduced-order model obtained by comparing its frequency domain properties with the original full-order one. Also, we evaluated the theoretical dynamic performance in the time domain of optimal controllers based on the reduced-order model. To illustrate the controller capabilities of tracking the trajectory while also decreasing the vibration, we applied reference signals in the Cartesian space with different accelerations to this flexible manipulator. Performance indices in the time domain, such as the root mean squared error and energy consumption, were also analyzed. These numerical results, regarding the reduction of the FE model and the controller performance, can demonstrate the importance of model-based control strategies for lightweight manipulators with flexible links.
Keywords
model-based control, multibody dynamic system, Model order reduction, Flexible Manipulators, parallel kinematic manipulators
