Dynamic Behaviors Of Two-Layer Composite Structure With Dielectric Elastomer Actuators Via Absolute Nodal Coordinate Formulation

The combination of flexible driving materials and flexible driven materials is the main form of the software structure of software robots,Dielectric elastomer has become the research object of flexible actuator design.The DE-based flexible actuator is a two-layer thin plate structure,that is,the DE film and the flexible electrode are made into a driving piece,which is bonded to the driven piece made of flexible and soft material,and the driving force is produced by electrically stimulating the driving plate to achieve complex movements of the composite structure.The driving material has nonlinear and large deformation characteristics,it is difficult to achieve accurate dynamic modeling and motion control,and the composite structure introduces multi-unit coupling problem.When multi-coupling unit is established under large deformation,coupling conditions are not easy.Therefore,the establishment of an accurate large flexible two-layer structural dynamics model is of great significance for the realization of the motion control of flexible actuators for software robots.Targeting at the accurate modelling of the composite flexible structure under DE actuation,a two-layer plate structure is established via absolute nodal coordinate formulation(ANCF)for accurate description of the deformation of the flexible structure with nonlinear features.The deformation compatibility conditions at the interface of the elements are exploited to establish the composite multi-element model and deduce the dynamic equations for the composite structure.DE actuator is introduced to study the dynamic behaviors of the composite flexible structure under DE actuation with various parameters.The dynamic analysis results may provide guidance for the dynamic modelling and actuation design for soft robots.The main contents are as below:(1)Dynamic modelling for the composite structure based on ANCFComposite two-layer plate model with C~1 continuity condition is established based on the deformation compatibility conditions with ANCF plate elements.Mooney-Rivlin hyper-elastic constitutive model and the DE material constitutive equations are introduced into the elements,and the stiffness matrices,the mass matrices and the generalized external force matrix are derived to establish the dynamic equation of the composite structure with DE actuators.(2)Effects of various parameters on the dynamic behaviors of the composite structure with one single DE actuatorThe dynamic behaviors of the composite flexible structure with one single DE actuator are studied through a number of numerical examples by using MATLAB software.Voltages,material and size parameters are changed to investigate their influence on the motion and the deformation forms of the composite structure.Results show that the deformation of the composite structure increases with the increase of applied voltage,and decreases nonlinearly with the increase of elastic modulus,The periodicity and stability of the end motion are significantly different at lower excitation voltages and higher excitation voltages.The smaller the size of the drive unit,the more linear the end motion of the composite structure changes with various parameters.(3)Study on the performance of the composite structure with multi-unit DE actuators and comparison with sing-unit actuatorComposite structure with multi-unit actuator is modelled based on deformation compatibility conditions across elements.Results show that the free end displacement of double-unit-actuator composite structure exhibits strongest regularity and periodicity.the single-unit-actuator structure has highest linearity relationship of the free-end-displacement and voltage,and the deformation regularity of the triple-unit-actuator structure is poor under various material parameters and excitation voltages.The end of the single-unit-actuator and the triple-unit-actuator composite structure stays in a warp shape in most of the time,and the free end of the double-unit-actuator structure is more likely to exhibit a"one head high and the other head low"S shape.