Computer-controlled ultra high voltage amplifier for dielectric elastomer actuators

Soft robotics is a breakthrough technology to support human-robot interactions.The soft structure of a soft robot can increase safety during human and robot interactions.One of the promising soft actuators for soft robotics is dielectric elastomer actuators(DEAs).DEAs can operate silently and have an excellent energy density.The simple structure of DEAs leads to the easy fabrication of soft actuators.The simplicity combined with silent operation and high energy density make DEAs interesting for soft robotics researchers.DEAs actuation follows the Maxwell-pressure principle.The pressure produced in the DEAs actuation depends much on the voltage applied.Common DEAs requires high voltage to gain an actuation.Since the power consumption of DEAs is in the milli-Watt range,the current needed to operate the DEAs can be neglected.Several commercially available DC-DC converters can convert the volt range to the kV range.In order to get a voltage in the 2-3 kV range,the reliable DC-DC converter can be pricy for each device.This problem hinders the education of soft actuators,especially for a newcomer laboratory that works in soft electric actuators.This paper introduces an entirely do-it-yourself(DIY)Ultrahigh voltage amplifier(UHV-Amp)for education in soft robotics.UHV-Amp can amplify 12 V to at a maximum of 4 kV DC.As a demonstration,we used this UHV-Amp to test a single layer of powdered-based DEAs.The strategy to build this educational type UHV-Amp was utilizing a Cockcroft-Walton circuit structure to amplify the voltage range to the kV range.In its current state,the UHV-Amp has the potential to achieve approximately 4 kV.We created a simple platform to control the UHV-Amp from a personal computer.In near future,we expect this easy control of the UHV-Amp can contribute to the education of soft electric actuators.

Toward broad optimal output bandwidth dielectric elastomer actuators

Dielectric elastomer actuators(DEAs)are one of the most promising soft actuation technologies owing to their relatively high power density and electromechanical efficiency enabled by a resonant actuation technique.However,existing DEA designs suffer from a very narrow optimal output bandwidth close to resonance and poor output control capability due to their fixed geometrical configurations.This condition greatly limits their applications in programmable actuation and broad-bandwidth applications.Accordingly,this work developed a novel resonance tunable DEA(RTDEA)design for broad-optimal-output actuation bandwidths that is enabled by an integration of a stiffness and voltage control strategy.This design features a broad resonant frequency adjustment from 84 to 126 Hz and independent tunings of its resonant amplitude and frequency.Parametric studies were conducted to illustrate the fundamental principles behind the resonance tuning strategy,and optimization was performed to maximize the tuning capability.Here,a resonance tuning control strategy is proposed to achieve accurate adjustments of the RTDEA’s resonance based on the stiffness and voltage control strategy.These resonance tunable soft actuators are envisioned to greatly expand DEAs’applications in,for instance,soft robotic locomotion,human–robot communication,and active vibrational control with demands of broad actuation bandwidths and high output performance.

Snap-through path in a bistable dielectric elastomer actuator

The dielectric elastomer(DE)has attracted significant attention due to its desired features,including large deformation,fast response,and high energy density.However,for a DE actuator(DEA)utilizing a snap-through deformation mode,most existing theoretical models fail to predict its deformation path.This paper develops a new finite element method(FEM)based on the three-parameter Gent-Gent model suitable for capturing strain-stiffening behaviors.The simulation results are verified by experiments,indicating that the FEM can accurately characterize the snap-through path of a DE.The method proposed in this paper provides theoretical guidance and inspiration for designing and applying DEs and bistable electroactive actuators.

Recent progress in the development of dielectric elastomer materials and their multilayer actuators

Dielectric elastomers(DEs)have emerged as one of the most promising artificial muscle technologies,due to their exceptional properties such as large actuation strain,fast response,high energy density,and flexible processibility for various configurations.Over the past two decades,researchers have been working on developing DE materials with improved properties and exploring innovative applications of dielectric elastomer actuators(DEAs).This review article focuses on two main topics:recent material innovation of DEs and development of multilayer stacking processes for DEAs,which are important to promoting commercialization of DEs.It begins by explaining the working principle of a DEA.Then,recently developed strategies for preparing new DE materials are introduced,including reducing mechanical stiffness,increasing dielectric permittivity,suppressing viscoelasticity loss,and mitigating electromechanical instability without pre-stretching.In the next section,different multilayer stacking methods for fabricating multilayer DEAs are discussed,including conventional dry stacking,wet stacking,a novel dry stacking method,and micro-fabrication-enabled stacking techniques.This review provides a comprehensive and up-to-date overview of recent developments in high-performance DE materials and multilayer stacking methods.It highlights the progress made in the field and also discusses potential future directions for further advancements.

PI-funnel and inverse hysteresis compensation cascade control of smart soft dielectric elastomer actuator

Smart soft dielectric elastomer actuators(SSDEAs)possess wide applications in soft robotics due to their properties similar to natural muscles,including large deformation ratio,high energy density,and fast response speed.However,the complicated asymmetric and rate-dependent hysteresis property,creep property and quadratic input property of the SSDEA pose enormous challenges to its dynamic modeling and motion control.In this paper,first,we construct the dynamic model of the SSDEA by connecting a square module,a one-sided Prandtl–Ishlinskii(OSPI)model and a linear system in series to describe the above properties.The key and innovative aspect of the dynamic modeling lies in cascading the square module in series with the OSPI model to construct the asymmetric hysteresis model.Subsequently,a PI-funnel and inverse hysteresis compensation(PIFIHC)cascade control method of the SSDEA is proposed to actualize its tracking control objective.By performing the inversion operation on the asymmetric hysteresis model,the inverse hysteresis compensation controller(IHCC)is designed to compensate the asymmetric hysteresis property and quadratic input property of the SSDEA.In addition,a PI-funnel controller is designed to cascade with the IHCC to construct the PIFIHC cascade controller to obtain a good tracking performance.Then,the stability analysis of the PIFIHC cascade control system of the SSDEA is performed to theoretically prove that the tracking error can be controlled within the performance funnel and the steady-state error converges to zero.Finally,several practical tracking control experiments of the SSDEA are conducted,and RRMSEs are less than 2.30%for all experiments.These experimental results indicate the effectiveness and feasibility of the proposed PIFIHC cascade control method of the SSDEA.

Fabrication and stiffness optimization of carbon-based composite double polymer compliant electrode

A manufacturing method is proposed for carbon based composite double polymer compliant electrode.The stiffness of this compliant electrode is changed by adjusting the mass fraction of carbon black and the ratios between Ecoflex20 and RT625.Tensile machine is used to test its ductility and hardness.The conductivity is measured through the source table.Finally,it is printed on the dielectric elastomers(DE)film,and the high-voltage amplifier is used for dielectric elastomers actuators(DEAs)dynamics testing.The results show that the compliant electrode has high tensile properties(>200%),low stiffness(<300 kPa)and well conductivity(0.0493 S/cm).It is proved that the DEAs displacement output is up to 1.189 mm by this compliant electrode under dynamic response,which is 1.64 times and 1.32 times of the same type.Moreover,this formula extends the curing time of the original compliant electrode ink.It can provide a reference for the production of compliant electrode and DEAs in the future.

Failure modeling of folded dielectric elastomer actuator

When subjected to voltage,the dielectric elastomer membrane reduces its thickness and expands its area under the resulting compressive force.This characteristic enables the dielectric elastomer actuators of different structures to be designed and fabricated.By employing the thermodynamic theory and research method proposed by Suo et al.,an equilibrium equation of folded dielectric elastomer actuator with two generalized coordinates is established.The governing equations of failure models involving electromechanical instability,zero electric field,electrical breakdown,loss of tension,and rupture by stretch are also derived.The allowable areas of folded dielectric elastomer actuators are described.These results could provide a powerful guidance to the design and performance evaluation of the dielectric elastomer actuators.