Design And Mechanical Performance Study Of Electro-active Soft Actuators

Due to their unique characteristics such as softness,light weight,high adaptability,and good interactivity,soft actuators have wide applications in fields such as biomedical engineering,surveillance and detection,and human-machine interaction.The actuating methods for soft robots mainly include fluid-actuated,magnetic-actuated,electric-actuated,optical-actuated,and chemical-actuated approaches.Among them,electric-actuated soft actuators based on dielectric elastomers have become a research hotspot due to their fast response,large deformation,high energy density,and ease of control.However,dielectric elastomer-actuated actuators require continuous high-voltage loading,which can lead to electrical breakdown due to accumulated heat in the thin film.Additionally,the inherent viscoelasticity of polymers causes a lag in the actuator response.Based on these challenges,this study focuses on the deformation principles of dielectric elastomers and proposes novel structures for electrically active soft actuators.The mechanical performance of these structures is thoroughly investigated.The specific research contents are as follows:1.Based on the thermodynamic framework,the deformation mechanism and ideal model of dielectric elastomers are introduced.It is pointed out that there are some deficiencies in the thermodynamic theory specifically addressing pure shear deformation.To address this,a network prediction model that describes the actuating behavior of pure shear dielectric elastomers is developed using the Gent free energy density function and BP neural network.The model is trained using finite element samples and validated through experiments.Using this model,the influence of design parameters on the actuating performance of pure shear deformation is studied,and the error between the network model and the traditional ideal model is analyzed.2.Taking advantage of the pure shear deformation characteristics of dielectric elastomers,a stiffness-variable bistable actuator is proposed.The Gent model is utilized for modeling,and the influence of design parameters on the bistable configuration and actuating performance is investigated by optimizing the energy equation.Additionally,a symmetry factor is introduced to achieve the transition between symmetric and asymmetric bistable configurations by adjusting the bending stiffness on both sides of the framework.Experimental validation is conducted to demonstrate different actuating strategies and transition methods between symmetric and asymmetric bistable states.3.To address the issue of dielectric breakdown failure in dielectric elastomers,a minimum energy structure spring actuator is designed based on the advantages of electrostatic hydraulic amplification and self-healing.The static and dynamic performance of the actuator are analyzed through experiments,demonstrating its ability to sustain continuous loading under high voltage(11.5 k V)without experiencing dielectric breakdown failure.Furthermore,a foot structure for a crawling robot is designed by combining a rocker arm mechanism with gears.The hydraulic spring actuator is integrated into the robot,forming a crawling-type robot.The relationship between the crawling speed and actuating frequency of the robot is tested by applying square wave voltage,verifying the feasibility of hydraulic actuation in soft robots.4.A concept of converting small axial displacement of an electrostatic hydraulic actuator into bending displacement is proposed.A hydraulic hinge actuator is designed,and its modeling is carried out using an energy-based approach.The impact of key design parameters on the performance of the hinge actuator is investigated through experiments.Subsequently,taking advantage of the response amplification produced by instability,a bistable beam element is introduced and coupled with the hydraulic actuator to form a bistable hydraulic actuator.Experimental results demonstrate that the addition of the bistable beam element achieves a 2.5-fold displacement response amplification and over 2-fold force response amplification compared to the original actuator.This successful demonstration validates the effectiveness of combining bistable structures with hydraulic actuation to enhance the performance of hydraulic actuators.