The Experts below are selected from a list of 1323 Experts worldwide ranked by ideXlab platform
Carmel Majidi - One of the best experts on this subject based on the ideXlab platform.
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Saddle-like deformation in a Dielectric Elastomer Actuator embedded with liquid-phase gallium-indium electrodes
2018Co-Authors: James Wissman, Lauren R Finkenauer, Luca Deseri, Carmel MajidiAbstract:We introduce a Dielectric Elastomer Actuator (DEA) composed of liquid-phase Gallium-Indium (GaIn) alloy electrodes embedded between layers of poly(dimethylsiloxane) (PDMS) and examine its mechanics using a specialized elastic shell theory. Residual stresses in theDielectric and sealing layers of PDMS cause the DEA to deform into a saddle-like geometry (Gaussian curvature K
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saddle like deformation in a Dielectric Elastomer Actuator embedded with liquid phase gallium indium electrodes
Journal of Applied Physics, 2014Co-Authors: James Wissman, Lauren R Finkenauer, Luca Deseri, Carmel MajidiAbstract:We introduce a Dielectric Elastomer Actuator (DEA) composed of liquid-phase Gallium-Indium (GaIn) alloy electrodes embedded between layers of poly(dimethylsiloxane) (PDMS) and examine its mechanics using a specialized elastic shell theory. Residual stresses in the Dielectric and sealing layers of PDMS cause the DEA to deform into a saddle-like geometry (Gaussian curvature K<0). Applying voltage Φ to the liquid metal electrodes induces electrostatic pressure (Maxwell stress) on the Dielectric and relieves some of the residual stress. This reduces the longitudinal bending curvature and corresponding angle of deflection ϑ. Treating the Elastomer as an incompressible, isotropic, NeoHookean solid, we develop a theory based on the principle of minimum potential energy to predict the principal curvatures as a function of Φ. Based on this theory, we predict a dependency of ϑ on Φ that is in strong agreement with experimental measurements performed on a GaIn-PDMS composite. By accurately modeling electromechanical coupling in a soft-matter DEA, this theory can inform improvements in design and fabrication.
Rahimullah Sarban - One of the best experts on this subject based on the ideXlab platform.
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dynamic electromechanical modeling of Dielectric Elastomer Actuators with metallic electrodes
IEEE-ASME Transactions on Mechatronics, 2012Co-Authors: Rahimullah Sarban, Benny Lassen, Morten WillatzenAbstract:In this paper, a nonlinear electromechanical model for a PolyPower Dielectric Elastomer Actuator is proposed based on an electric circuit model coupled with a viscoelastic mechanical model. The parameters of the model are found by fitting to an electrical step impulse for the mechanical part and by standard methods for the electric circuit. The resulting model is compared with experiments for a range of sinusoidal stimuli. The comparison shows good agreement between experiments and model results.
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inverse grey box model based control of a Dielectric Elastomer Actuator
Smart Materials and Structures, 2012Co-Authors: Richard W Jones, Rahimullah SarbanAbstract:An accurate physical-based electromechanical model of a commercially available tubular Dielectric Elastomer (DE) Actuator has been developed and validated. In this contribution, the use of the physical-based electromechanical model to formulate a model-based controller is examined. The choice of control scheme was dictated by the desire for transparency in both controller design and operation. The internal model control (IMC) approach was chosen. In this particular application, the inverse of the linearized form of the grey-box model is used to formulate the IMC controller. To ensure consistent control performance across the operating range of the DE Actuator, a gain scheduling term, which linearizes the operating characteristics of the tubular Dielectric Elastomer Actuator, is developed and implemented in series with the IMC controller. The IMC-based approach is investigated for servo control of the DE Actuator position as well as its ability to provide vibration isolation of a payload subject to ground vibration.
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physical model based active vibration control using a Dielectric Elastomer Actuator
Journal of Intelligent Material Systems and Structures, 2012Co-Authors: Rahimullah Sarban, Richard W JonesAbstract:Dielectric Elastomer is a new type of electroactive material, which has the potential to provide effective actuation for a wide range of applications. The force, strain and speed of response proper...
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a tubular Dielectric Elastomer Actuator fabrication characterization and active vibration isolation
Mechanical Systems and Signal Processing, 2011Co-Authors: Rahimullah Sarban, Richard P O Jones, B R Mace, Emiliano RustighiAbstract:Physicists and chemists have long sought to develop lightweight materials that grow or shrink significantly in length or volume when subjected to electric stimulation. A new material of this type is Dielectric Electro-Active Polymer (DEAP), which when utilised as an Actuator, has the potential to be an effective replacement for many conventional Actuators. DEAP has a range of properties that place it somewhere between those of piezoceramics and shape memory alloys (SMA's). DEAP Actuators, among many other applications, have the potential to be used in active vibration control (AVC). The overall goal of this work was to investigate the viability of using a DEAP Actuator in active vibration isolation (AVI). In the experimental setup, a mass, representing an instrument for example, was intended to be isolated from ground vibration, generated by an electrodynamic shaker, by placing an active isolator (the DEAP Actuator) between the shaker and mass. First, this paper introduces the basic characteristics of one type of DEAP material, called PolyPower®. Among the Actuator types, constructed from PolyPower material, those having a tubular shape are investigated here. The static and dynamic characteristics of the Actuators as well as the frequency response function are of special interest from the AVC point of view, and are investigated for the tubular type PolyPower Actuators. Experimental results are presented. Feedforward control approach was used in all experiments. Least mean squared (LMS) adaptive algorithm was used to optimize the control parameters iteratively in order to minimize the displacement of the solid mass caused by the shaker. Three different types of controller, single harmonic controller, double harmonic controller and FIR controller were used for tonal isolation. The implications associated with the Actuator?s nonlinearities and the performance of the three controllers was assessed. FIR controller was also used for broadband isolation and the proper choices of its parameters were experimentally determined
Samuel Rosset - One of the best experts on this subject based on the ideXlab platform.
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identification of a nonlinear Dielectric Elastomer Actuator based on the harmonic balance method
IEEE-ASME Transactions on Mechatronics, 2021Co-Authors: Jakub Bernat, Jakub Kolota, Samuel RossetAbstract:This article presents a control-oriented modeling of a circular Dielectric Elastomer Actuator loaded with a mass. Precise dynamic position control of these Actuators is a challenge, because of the high level of nonlinearities. Our model takes into account nonlinear mechanical phenomena such as hyperelasticity and viscoelasticity. The behavior of Dielectric Elastomer Actuators is analyzed by a series of experiments on three Actuators with different parameters. Furthermore, the model parameters are found using optimization procedures. To improve the performance of the optimization, the steady-state solution is found using the harmonic balance method (HBM). Compared to a forward integration method, the time gain of the HBM is significant, and exceeds two orders of magnitude when six or less harmonics are considered. The application of steady-state solver enables taking the frequency response into account for the parameter identification procedure. The results obtained from the model are compared with experiments and show an excellent agreement.
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identification of a nonlinear Dielectric Elastomer Actuator based on the harmonic balance method
IEEE-ASME Transactions on Mechatronics, 2020Co-Authors: Jakub Bernat, Jakub Koota, Samuel RossetAbstract:This paper presents a control-oriented modelling of a circular Dielectric Elastomer Actuator loaded with a mass. Precise dynamic position control of these Actuators is a challenge, because of the high level of nonlinearities. Our model takes into account nonlinear mechanical phenomena such as hyperelasticity and viscoelasticity. The behavior of Dielectric Elastomer Actuators is analyzed by a series of experiments on three Actuators with different parameters. Furthermore, the model parameters are found using optimization procedures. To improve the performance of the optimization, the steady state solution is found using the Harmonic Balance Method. Compared to a forward integration method, the time gain of the Harmonic Balance Method is significant, and exceeds 2 orders of magnitude when 6 or less harmonics are considered. The application of steady state solver enables taking the frequency response into account for the parameter identification procedure. The results obtained from the model are compared with experiments and show an excellent agreement.
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Dielectric Elastomer Actuator for mechanical loading of 2d cell cultures
Lab on a Chip, 2016Co-Authors: Alexandre Poulin, Samuel Rosset, Cansaran Saygili Demir, Tatiana V PetrovaAbstract:We demonstrate the use of Dielectric Elastomer Actuators (DEAs) for mechanical stimulation of cells in vitro. The development of living tissues is regulated by their mechanical environment through the modification of fundamental cellular functions such as proliferation, differentiation and gene expression. Mechanical cues have been linked to numerous pathological conditions, and progress in cellular mechanobiology could lead to better diagnosis and treatments of diseases such as atherosclerosis and cancers. Research in this field heavily relies on in vitro models due to the high complexity of the in vivo environment. Current in vitro models however build on bulky and often complex sets of mechanical motors or pneumatic systems. In this work we present an alternative approach based on DEAs, a class of soft Actuators capable of large deformation (>100%) and fast response time (<1 ms). The key advantage of DEAs is that they can be integrated within the culture substrate, therefore providing a very compact solution. Here we present a DEA-based deformable bioreactor which can generate up to 35% uniaxial tensile strain, and is compatible with standard cell culture protocols. Our transparent device also includes a static control area, and enables real-time optical monitoring of both the stimulated and control cell populations. As a proof of concept we cycled a population of lymphatic endothelial cells (LECs) between 0% and 10% strain at a 0.1 Hz frequency for 24 h. We observe stretch-induced alignment and elongation of LECs, providing the first demonstration that DEAs can be interfaced with living cells and used to control their mechanical environment.
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Fully printed 3 microns thick Dielectric Elastomer Actuator
Proceedings of SPIE, 2016Co-Authors: Alexandre Poulin, Samuel RossetAbstract:In this work we present a new fabrication technique to print thin Dielectric Elastomer Actuators (DEAs), reducing the driving voltage below 300 V while keeping good actuation performance. With operation voltages in the kV-range, standard DEAs are limited in terms of potential applications. Using thinner membranes is one of the few existing methods to achieve lower operation voltages. Typical DEAs have membranes in the 20-100 um range, values below which membrane fabrication becomes challenging and the membrane quality and uniformity degrade. Using pad printing we produced thin silicone Elastomer membranes, on which we pad-printed compliant electrodes. We then fabricated DEAs by assembling two membranes back to back. We obtain an actuation strain of 7.5% at only 245 V on a 3 um thick DEA. In order to investigate the stiffening impact of the electrodes we developed a simple DEA model that includes their mechanical properties. We also developed a strain-mapping algorithm based on optical correlation. The simulation results and the strain-mapping measurements confirm that the stiffening impact of the electrodes increases for thinner membranes. Electrodes are an important element that cannot be neglected in the design and optimization of ultra-thin DEAs.
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variable stiffness Actuator for soft robotics using Dielectric Elastomer and low melting point alloy
Intelligent Robots and Systems, 2015Co-Authors: Jun Shintake, Samuel Rosset, Bryan Edward Schubert, Dario FloreanoAbstract:A novel variable stiffness Actuator composed of a Dielectric Elastomer Actuator (DEA) and a low-melting-point-alloy (LMPA) embedded silicone substrate is demonstrated. The device which we call variable stiffness Dielectric Elastomer Actuator (VSDEA) enables functional soft robots with a simplified structure, where the DEA generates a bending actuation and the LMPA provides controllable stiffness between soft and rigid states by Joule heating. The entire structure of VSDEA is made of soft silicones with an elastic modulus of less than 1 MPa providing a high compliance when the LMPA is active. The device has the dimension of 40 mm length × 10 mm width × 1 mm thickness, with mass of ∼1 g. We characterize VSDEA in terms of the actuation stroke angle, the blocked force, and the reaction force against a forced displacement. The results show the controllable actuation angle and the blocked force up to 23.7 ° and 2.4 mN in the soft state, and 0.6 ° and 2.1 mN in the rigid state. Compared to an Actuator without the LMPA, VSDEA exhibits ∼90× higher rigidity. We develop a VSDEA gripper where the mass of active parts is ∼2 g, which is able to successfully hold an object mass of 11 g, exhibiting the high performance of the Actuator.
Andrew T Conn - One of the best experts on this subject based on the ideXlab platform.
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power optimization of a conical Dielectric Elastomer Actuator for resonant robotic systems
Extreme Mechanics Letters, 2020Co-Authors: Chongjing Cao, Andrew T Conn, Xing Gao, Stuart C BurgessAbstract:Abstract Insects utilize resonant actuation to amplify the flapping stroke and improve the energy efficiency. The inherent elasticity in Dielectric Elastomer Actuators (DEAs) offers the advantage over conventional Actuators of achieving resonant actuations with no additional elastic elements required. Despite that the resonant actuation of the DEAs have attracted great research interests, no optimization has been done on the output performance of resonating DEAs. In this work, a double cone DEA (DCDEA) configuration is adopted and a numerical model is developed to characterize its dynamic response. An effective power study framework is developed and the power output of the DCDEA is optimized against its pre-stretch ratios and spacer length. To demonstrate the potential exploitation of resonant DEA performance, a bioinspired flapping wing mechanism driven by the optimized DCDEA design is developed with a peak flapping stroke of 31°at its resonance of 30 Hz.
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nonlinear dynamics of a magnetically coupled Dielectric Elastomer Actuator
Physical review applied, 2019Co-Authors: Chongjing Cao, Thomas L Hill, Andrew T Conn, Xing GaoAbstract:The magnetically coupled Dielectric Elastomer Actuator (MCDEA) is an emerging two-degree-of-freedom system that demonstrates rich dynamical behavior, which is important for applications in robotics, energy harvesting, and smart structures. However, the complex nonlinear dynamical behavior that can arise in such a system is challenging to predict. The authors develop a numerical model that can accurately characterize these dynamics, and thus suggests control strategies to manage $e.g.$ the appearance and amplitude of a specific resonance. These insights will impact engineering solutions for active vibrational control, energy harvesting, and programmable soft motors.
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a compliantly coupled Dielectric Elastomer Actuator using magnetic repulsion
Applied Physics Letters, 2019Co-Authors: Chongjing Cao, Xing Gao, Andrew T ConnAbstract:Dielectric Elastomer Actuators (DEAs) have attracted growing research interest over the past two decades for their large actuation strain, inherent compliance, and low cost. The conical DEA configuration is particularly attractive thanks to their simple structure and high force/stroke actuation. A double cone DEA design with two antagonistic membranes allows active bidirectional actuation. However, in existing double cone DEA designs, the two membranes are rigidly coupled, which restricts their relative actuation response under periodic electrical input to 180° out-of-phase operation. This work presents a magnetically coupled DEA with compliant coupling by a magnetic repulsion. The compliant coupling allows two separate inputs with a fully adjustable phase difference. The current prototype demonstrates a peak normalized stroke of 14% (relative to the nominal DEA height) at a phase shift of 180° and a normalized linear expansion between the two membranes of up to 8.3% (relative to the nominal DEA height) at a phase shift of 0° at 0.5 Hz. This results in several emerging actuation behaviors, which could potentially be suitable for controllable shape changing actuations, active vibration damping, and bioinspired locomotion.
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performance optimization of a conical Dielectric Elastomer Actuator
Actuators, 2018Co-Authors: Chongjing Cao, Andrew T ConnAbstract:Dielectric Elastomer Actuators (DEAs) are known as ‘artificial muscles’ due to their large actuation strain, high energy density and self-sensing capability. The conical configuration has been widely adopted in DEA applications such as bio-inspired locomotion and micropumps for its good compactness, ease for fabrication and large actuation stroke. However, the conical protrusion of the DEA membrane is characterized by inhomogeneous stresses, which complicate their design. In this work, we present an analytical model-based optimization for conical DEAs with the three biasing elements: (I) linear compression spring; (II) biasing mass; and (III) antagonistic double-cone DEA. The optimization is to find the maximum stroke and work output of a conical DEA by tuning its geometry (inner disk to outer frame radius ratio a/b) and pre-stretch ratio. The results show that (a) for all three cases, stroke and work output are maximum for a pre-stretch ratio of 1 × 1 for the Parker silicone Elastomer, which suggests the stretch caused by out-of-plane deformation is sufficient for this specific Elastomer. (b) Stroke maximization is obtained for a lower a/b ratio while a larger a/b ratio is required to maximize work output, but the optimal a/b ratio is less than 0.3 in all three cases. (c) The double-cone configuration has the largest stroke while single cone with a biasing mass has the highest work output.
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antagonistic Dielectric Elastomer Actuator for biologically inspired robotics
Proceedings of SPIE, 2011Co-Authors: Andrew T Conn, Jonathan RossiterAbstract:For optimal performance, Actuators designed for biologically-inspired robotics applications need to be capable of mimicking the key characteristics of natural musculoskeletal systems. These characteristics include a large output stroke, high energy density, antagonistic operation and passive compliance. The actuation properties of Dielectric Elastomer Actuators (DEAs) make them viable for use as an artificial muscle technology. However, much like the musculoskeletal system, rigid structures are needed to couple the compliant DEA layers to a load. In this paper, a cone DEA design is developed as an antagonistic, multi-DOF Actuator, viable for a variety for biologically-inspired robotics applications. The design has the advantage of maintaining pre-strain through a support structure without substantially lowering the overall mass-specific power density. Prototype cone DEAs have been fabricated with VHB 4910 acrylic Elastomer and have characteristic dimensions of 49mm (strut length) and 60mm (DEA diameter). Multi-DOF kinematical outputs of the cone DEAs were measured using a custom 3D motion tracking system. Experimental tests of the prototypes demonstrate antagonistic linear (±10mm), rotational (±25°) and combined multi-DOF strokes. Overall, antagonistic cone DEAs are shown to produce a complex multi-DOF output from a mass-efficient support structure and thus are well suited for being exploited in biologically-inspired robotics.
Chongjing Cao - One of the best experts on this subject based on the ideXlab platform.
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power optimization of a conical Dielectric Elastomer Actuator for resonant robotic systems
Extreme Mechanics Letters, 2020Co-Authors: Chongjing Cao, Andrew T Conn, Xing Gao, Stuart C BurgessAbstract:Abstract Insects utilize resonant actuation to amplify the flapping stroke and improve the energy efficiency. The inherent elasticity in Dielectric Elastomer Actuators (DEAs) offers the advantage over conventional Actuators of achieving resonant actuations with no additional elastic elements required. Despite that the resonant actuation of the DEAs have attracted great research interests, no optimization has been done on the output performance of resonating DEAs. In this work, a double cone DEA (DCDEA) configuration is adopted and a numerical model is developed to characterize its dynamic response. An effective power study framework is developed and the power output of the DCDEA is optimized against its pre-stretch ratios and spacer length. To demonstrate the potential exploitation of resonant DEA performance, a bioinspired flapping wing mechanism driven by the optimized DCDEA design is developed with a peak flapping stroke of 31°at its resonance of 30 Hz.
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nonlinear dynamics of a magnetically coupled Dielectric Elastomer Actuator
Physical review applied, 2019Co-Authors: Chongjing Cao, Thomas L Hill, Andrew T Conn, Xing GaoAbstract:The magnetically coupled Dielectric Elastomer Actuator (MCDEA) is an emerging two-degree-of-freedom system that demonstrates rich dynamical behavior, which is important for applications in robotics, energy harvesting, and smart structures. However, the complex nonlinear dynamical behavior that can arise in such a system is challenging to predict. The authors develop a numerical model that can accurately characterize these dynamics, and thus suggests control strategies to manage $e.g.$ the appearance and amplitude of a specific resonance. These insights will impact engineering solutions for active vibrational control, energy harvesting, and programmable soft motors.
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a compliantly coupled Dielectric Elastomer Actuator using magnetic repulsion
Applied Physics Letters, 2019Co-Authors: Chongjing Cao, Xing Gao, Andrew T ConnAbstract:Dielectric Elastomer Actuators (DEAs) have attracted growing research interest over the past two decades for their large actuation strain, inherent compliance, and low cost. The conical DEA configuration is particularly attractive thanks to their simple structure and high force/stroke actuation. A double cone DEA design with two antagonistic membranes allows active bidirectional actuation. However, in existing double cone DEA designs, the two membranes are rigidly coupled, which restricts their relative actuation response under periodic electrical input to 180° out-of-phase operation. This work presents a magnetically coupled DEA with compliant coupling by a magnetic repulsion. The compliant coupling allows two separate inputs with a fully adjustable phase difference. The current prototype demonstrates a peak normalized stroke of 14% (relative to the nominal DEA height) at a phase shift of 180° and a normalized linear expansion between the two membranes of up to 8.3% (relative to the nominal DEA height) at a phase shift of 0° at 0.5 Hz. This results in several emerging actuation behaviors, which could potentially be suitable for controllable shape changing actuations, active vibration damping, and bioinspired locomotion.
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performance optimization of a conical Dielectric Elastomer Actuator
Actuators, 2018Co-Authors: Chongjing Cao, Andrew T ConnAbstract:Dielectric Elastomer Actuators (DEAs) are known as ‘artificial muscles’ due to their large actuation strain, high energy density and self-sensing capability. The conical configuration has been widely adopted in DEA applications such as bio-inspired locomotion and micropumps for its good compactness, ease for fabrication and large actuation stroke. However, the conical protrusion of the DEA membrane is characterized by inhomogeneous stresses, which complicate their design. In this work, we present an analytical model-based optimization for conical DEAs with the three biasing elements: (I) linear compression spring; (II) biasing mass; and (III) antagonistic double-cone DEA. The optimization is to find the maximum stroke and work output of a conical DEA by tuning its geometry (inner disk to outer frame radius ratio a/b) and pre-stretch ratio. The results show that (a) for all three cases, stroke and work output are maximum for a pre-stretch ratio of 1 × 1 for the Parker silicone Elastomer, which suggests the stretch caused by out-of-plane deformation is sufficient for this specific Elastomer. (b) Stroke maximization is obtained for a lower a/b ratio while a larger a/b ratio is required to maximize work output, but the optimal a/b ratio is less than 0.3 in all three cases. (c) The double-cone configuration has the largest stroke while single cone with a biasing mass has the highest work output.