The Basic Research On Dynamic Control Modeling Of EAP Actuator

Electroactive Polymer (EAP) become a popular material in the field of robotic, toys andmedicinal machinery due to their light weight, noiseless operation, large strain, modestresponse time, high energy density, strong environmental tolerance and cheap. Dielectricelastomer (DE) is one of electric-filed-type electroactive polymer, and also is the most widelyused EAP material. The actuation principle of DE material is based on the electrostaticpressure being induced between oppositely charged electrodes. The electrostatic pressurecauses a compression of the DE sheets in the thickness direction. The thickness compressionresults in an extension of the material in the plane perpendicular to the thickness direction.Although the physical actuation principle of DE material can be easily understood, predictingthe actuation for a given electrical stimulus is not as straightforward.The modeling and simulation were carried out to figure out characteristics ofnonlinearity in dielectric elastomer material in this thesis. The main research work of thisthesis is organized as follows：(1) The disadvantages of conventional actuate method were explained; The significanceof researching on electroactive polymer were introduced; The overseas and domestic researchstatus of EAP actuator’s application and modeling were summarized.(2) The actuation principle of DE material was explained. The influence of prestrain forDE material’s deformation was analyzed. The viscoelastic behavior of polymer was explained,and the two of the most simple viscoelastic models were introduced. The theory ofhyperelastic materials was explained, and many functional forms of the strain energy wereintroduced. The DE material’s mechanical properties were discussed by the strain energyunder the boundary condtions of uniaxial and biaxial pre-stretch, respectively.(3) Taking DE material’s mechanical characteristics of nonlinearity, incompressibilityhyperelasticity and viscoelasticity into account, The DE material’s mechanical properties weredescribed by viscoelastic model when the DE actuator undergoing relatively smalldeformations, and by three common strain energy function (Yeoh, Mooney-Rivlin and Ogden)when the DE actuator undergoing large deformations. A electrical model was modeled, andthen, combining with the mechanical model, a dynamic electromechanical model of a DEactuator was modeled.(4) Two experiments were introduced, and their experimental datas were acquired. The unknown model parameters were obtained by fitting its creep compliance to the experimentaldatas using MATLAB2009’s lsqcurvefit function. And then, The fitting curves were provided.The influence of the experimental setup for experiments was analyzed. The DE actuatorrespon of the known stimuli were given.(5) The model was implemented and simulated in MATLAB. It is shown that the modelis close agreement with the measured response of the DE actuator. The model can also beused to design and control actuators.