Random Vibration Control For Mechanical Systems With Dielectric Elastomer Actuators

Soft robots possess prominent performance of human-machine interaction.The interface of the soft materials,however,induces the weak operating accuracy of soft robots.How to improve the operating accuracy dramatically with little cost is of important significance.In this thesis,we take the mechanical systems with dielectric elastomer actuators as research objects and investigate the optimal control strategy to minimize the random responses.The optimal feedback control strategies are first established by theoretical analysis,then verified by numerical simulations and experiments.In the first part of this thesis,we investigate the aspects of theory and numerical simulation.Mechanical systems with plate-type and conical-type dielectric elastomer actuators are investigated,respectively.The relations of force to deformation are first derived by using the thermodynamic principle.The stochastic dynamic equations of the mechanical systems are established and then the governing equations with respect to the disturbance around the associated equilibrium position are deduced.The low-dimensional stochastic differential equations with respect to system total energy are obtained by using the stochastic averaging method.Combining stochastic averaging with the stochastic dynamic programming principle,the optimal feedback control strategies are established.The derived feedback control strategies can significantly reduce the level of random responses by lightly adjusting the imposed voltage in real time.Numerical simulations illustrate the good control effectiveness and high control efficiency.In the second part of this thesis,we concentrate on the experimental aspect of the random optimal control.In the experiment,a mechanical system,i.e.,a pendulum,with conical dielectric elastomer actuator are investigated.The experimental platform including the mechanical system,laser vibrator,signal processing device and voltage amplifier,is first built to execute the random optimal control strategies.The influences of the bound of optimal control and the reference voltage on the effectiveness of the optimal bounded control strategy are investigated for three different bandwidth of random excitations.The experimental results verify the efficacy of the optimal feedback control strategies to suppress the response level of the random-excited mechanical systems.