Experimental Model Identification for Flexible Multibody Mechanisms Through the Flexible Natural Coordinate Formulation and Vision-Based Measurements

EasyChair Preprint 13316

Abstract

This work presents a novel framework for the experimental model identification of flexible multibody mechanisms. It is shown that by exploiting the flexible natural coordinate formulation (FNCF) and vision-based measurements. By using the FNCF formulation, both the mass matrix and the stiffness matrix in the equations of motion are constant. This property opens up the possibility for a least-squares model identification where, instead of the often time-consuming model simulations between optimizer iterations, simple matrix multiplications are used. However, this requires knowledge of the full vector of generalized coordinates and the external excitation for each time step. By only using conventional sensors (e.g., accelerometers, strain gauges, encoders), this is difficult to achieve, especially for flexible multibody mechanisms where measurements of both the rigid body motion and the flexible deformations are required. Therefore, this research proposes the use of vision-based measurements, as they can provide full-field motion measurements of the mechanism with sufficient accuracy and spatial density to extract individual component deformations. The vision-based motion tracking in this research uses an affine Lucas-Kanade optical flow in combination with Procrustes motion separation to obtain the components' rigid body motions and deformation motions. Both a hybrid modal decomposition and a singular value decomposition are exploited to decompose the deformation motion into individual modes and participation factors. As a validation platform, a planar slider-crank mechanism is used. Here, the crank is considered a rigid component while the connecting rod is assumed to be flexible. The setup is recorded with a Photron SA-Z High-Speed Camera at 40,000 frames per second while the crank rotates at a speed of 60 rad/s. The external excitation is obtained by a torque readout from the driving servomotor.

Keyphrases: camera measurements, flexible multibody system, flexible natural coordinate formulation (FNCF), model identification

@booklet{EasyChair:13316,
  author    = {Thijs Willems and Klemen Zaletelj and Simon Vanpaemel and Janko Slavič and Frank Naets},
  title     = {Experimental Model Identification for Flexible Multibody Mechanisms Through the Flexible Natural Coordinate Formulation and Vision-Based Measurements},
  howpublished = {EasyChair Preprint 13316},
  year      = {EasyChair, 2024}}