Dynamic Performance of Flexible Composite Structures with Dielectric Elastomer Actuators via Absolute Nodal Coordinate Formulation

Author(s):  
Haidong Yu ◽  
Yunyong Li ◽  
Aolin Chen ◽  
Hao Wang
Author(s):  
Gengxiang Wang

The moving platform of the 4-SPS/CU (S is the spherical joint, P is the prismatic joint, C is the cylindrical joint, U is the universal joint) parallel mechanism is treated as a thin-plate element based on the absolute nodal coordinate formulation due to its physical characteristic. In order to eliminate high-frequency modes caused by the coupling between membrane and bending effects, the elastic mid-surface approach is used to evaluate the elastic force of the flexible moving platform. In order to formulate constraint equations between the flexible body and the rigid body, the tangent frame is introduced to define the joint coordinate system that is rigidly attached to the node at the joint, which is convenient for determining the constant vector in the joint coordinate system. The dynamics model of the parallel mechanism with the flexible moving platform is built based on the equation of motion. The simulation results show that the vibration frequency caused by the flexible body will be increased with the increasing stiffness of the material, and the kinematic trajectory and dynamics performance of the parallel mechanism are affected seriously when the smaller Young’s modulus is used, which illustrates that the effect of the flexible moving platform on the dynamic performance of the parallel mechanism should not be ignored.


2018 ◽  
Vol 29 (5) ◽  
pp. 986-997 ◽  
Author(s):  
Hamza Edher ◽  
Armaghan Salehian

Dielectric elastomer actuators have been considered for an increasing number of applications due to their desirable characteristics of low weight, high strain outputs and favourable material costs. The present work describes the use of a dielectric elastomer actuator in conjunction with a belt mechanism to apply cyclic active compression. The belt mechanism helps convert the stress relaxation upon the voltage application to the dielectric elastomer actuator to a compressive force. Testing is conducted using multi-layered silicone–based dielectric elastomer actuators. A novel method of dynamically charging dielectric elastomer actuators through manipulating the input signal shape, termed the hold method, is introduced. Using this method, cyclic actuation strain output can be increased by 24% with insignificant change in actuation output curve shape. Furthermore, the effect of pre-stretch ratios on the output force amplitudes is characterized. The optimized hold time parameters obtained through cyclic dielectric elastomer force and strain are utilized for active compression physiological testing and a pressure gradient of 10 mmHg is achieved.


1999 ◽  
Vol 122 (4) ◽  
pp. 498-507 ◽  
Author(s):  
Marcello Campanelli ◽  
Marcello Berzeri ◽  
Ahmed A. Shabana

Many flexible multibody applications are characterized by high inertia forces and motion discontinuities. Because of these characteristics, problems can be encountered when large displacement finite element formulations are used in the simulation of flexible multibody systems. In this investigation, the performance of two different large displacement finite element formulations in the analysis of flexible multibody systems is investigated. These are the incremental corotational procedure proposed in an earlier article (Rankin, C. C., and Brogan, F. A., 1986, ASME J. Pressure Vessel Technol., 108, pp. 165–174) and the non-incremental absolute nodal coordinate formulation recently proposed (Shabana, A. A., 1998, Dynamics of Multibody Systems, 2nd ed., Cambridge University Press, Cambridge). It is demonstrated in this investigation that the limitation resulting from the use of the infinitesmal nodal rotations in the incremental corotational procedure can lead to simulation problems even when simple flexible multibody applications are considered. The absolute nodal coordinate formulation, on the other hand, does not employ infinitesimal or finite rotation coordinates and leads to a constant mass matrix. Despite the fact that the absolute nodal coordinate formulation leads to a non-linear expression for the elastic forces, the results presented in this study, surprisingly, demonstrate that such a formulation is efficient in static problems as compared to the incremental corotational procedure. The excellent performance of the absolute nodal coordinate formulation in static and dynamic problems can be attributed to the fact that such a formulation does not employ rotations and leads to exact representation of the rigid body motion of the finite element. [S1050-0472(00)00604-8]


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