Control-focused, nonlinear and time-varying modelling of dielectric elastomer actuators with frequency response analysis

Current models of dielectric elastomer actuators (DEAs) are mostly constrained to first principal descriptions that are not well suited to the application of control design due to their computational complexity. In this work we describe an integrated framework for the identification of control focused, data driven and time-varying DEA models that allow advanced analysis of nonlinear system dynamics in the frequency-domain. Experimentally generated input–output data (voltage-displacement) was used to identify control-focused, nonlinear and time-varying dynamic models of a set of film-type DEAs. The model description used was the nonlinear autoregressive with exogenous input structure. Frequency response analysis of the DEA dynamics was performed using generalized frequency response functions, providing insight and a comparison into the time-varying dynamics across a set of DEA actuators. The results demonstrated that models identified within the presented framework provide a compact and accurate description of the system dynamics. The frequency response analysis revealed variation in the time-varying dynamic behaviour of DEAs fabricated to the same specifications. These results suggest that the modelling and analysis framework presented here is a potentially useful tool for future work in guiding DEA actuator design and fabrication for application domains such as soft robotics

A quadrafunctional electrocatalyst of nickel/nickel oxide embedded N-graphene for oxygen reduction, oxygen evolution, hydrogen evolution and hydrogen peroxide oxidation reactions

A multifunctional nano-heterostructured electrocatalyst of transition metal/metal oxide (nickel/nickel oxide) embedded on nitrogen-doped graphene is reported. The hybrid composite of N-doped graphene nanosheets with a high atomic percentage of nitrogen (8.2 at%) and embedded with highly distributed nickel/nickel oxide nanoparticles inside the graphene layers is synthesized by a one pot thermal annealing process. The resultant composite demonstrates excellent electrocatalytic activity utilizing the superior electrocatalytic properties of nickel/nickel oxide nanoparticles supported on nitrogen-doped graphene. The hybrid exhibits efficient oxygen reduction reaction (ORR) properties comparable with state-of-the-art electrode Pt/C with a four-electron transfer pathway and superior oxygen evolution reaction (OER) compared to the state-of-the-art electrode for the OER, Ru/C. Alternatively, this composite acts as an excellent electrode material for the hydrogen evolution reaction (HER) both in acidic and alkaline media. Nevertheless, this composite facilitates the hydrogen peroxide oxidation reaction (HPOR) in the presence of hydrogen peroxide, which is crucial for developing reversible fuel cells and fuel cells with liquid oxidant

Nitrogen doped graphene via thermal treatment of composite solid precursors as a high performance supercapacitor

A novel method for nitrogen doping of graphene via solid-state impregnation was developed using graphene oxide (GO) as the raw substrate and aminoterephthalic acid as the doping agent via a facile thermal treatment at 750 °C. The structure, morphology and chemical composition of the synthesised N-doped graphene were characterised using XRD, SEM, EDS and XPS. The N-graphene product exhibits homogeneous doping with high nitrogen content (approx. 6 at%) in four configurations: pyridinic-N, pyrrolic-N, pyridinic-N-oxide and graphitic-N. The electric double layer capacitor (EDLC) fabricated using an N-doped graphene electrode attained a specific capacitance of 210 F g-1 (at a current density of 1 A g-1), which was greater than the values attained by pristine graphene and a GO electrode by factors of about two and six, respectively. Our synthesised N-graphene shows supercapacitance at a low electrolyte concentration compared to supercapacitors reported in the literature for high electrolyte concentrations with similar electrodes. The EDLC device we constructed based on N-graphene showed excellent charge-discharge stability for tests of up to 5000 cycles with high capacity retention (\u3e90%). A comparison of the electrochemical performance of GO, graphene and N-graphene demonstrated that doping with nitrogen can dramatically enhance capacitance