Multisine Excitation Research Articles

Fiber-Reinforced Soft Bending Actuator Control Utilizing On/Off Valves

Soft fluid-driven robots have great potential for safe interaction with humans, and for adaptation to complex and unpredictable environments with the compliance brought about by soft materials. However, the respective complex structure and massive use of nonlinear and viscoelastic soft materials, and the nonlinear fluid-driven dynamics, result in the nonlinear dynamic behavior of soft robots, and thus pose great challenges to system modeling and dynamic control. In this study, a complete model is first established by considering the nonlinear behavior of fiber-reinforced soft bending actuator (FRSBA) and the nonlinear dynamics of pneumatic system regulated by two high-speed on/off valves. Notably, the nonlinear dynamic behavior of FRSBA is first identified as parametric uncertainties using the multi-sine pressure excitation signal, and the effects of nonlinear pneumatic system are fully taken into account. Then, an adaptive robust controller is designed to handle the system nonlinearities with a guaranteed transient and steady-state performance. Finally, the comparative experiments demonstrate the effectiveness of proposed modeling method and high performance of adaptive robust controller.

Detection, Classification, and Quantification of Nonlinear Distortions in Time-Varying Frequency Response Function Measurements

The class of nonlinear time-varying (NLTV) systems includes all possible systems and, hence, is difficult to identify. Still, when the nonlinearities are not too strong then, depending on the application, a linear model might be sufficient for approximating the true response. To quantify the approximation error of the linear model, detecting and quantifying the nonlinear behavior are of key importance. In this article, we propose a fully automated procedure for detecting, classifying, and quantifying the nonlinear distortions in the response, possibly subject to a trend, of a specific class of NLTV systems to odd random phase multisine excitations. The result is a measurement of the time-varying frequency response function together with uncertainty bounds due to noise and nonlinear distortions. The user only has to specify four integer numbers: an upper bound on: 1) the degree on the time-domain polynomial modeling of the trend; 2) the degree of the frequency-domain polynomial basis function; 3) the number of frequency-domain hyperbolic-like basis functions, all used for modeling the output spectrum; and 4) a quality measure-called degrees of freedom (dof)-of the noise variance estimate. Guidelines are provided for obtaining reasonable values for these upper bounds.

A nonlinear model of vortex-induced forces on an oscillating cylinder in a fluid flow

A nonlinear model relating the imposed motion of a circular cylinder, submerged in a fluid flow, to the transverse force coefficient is presented. The nonlinear fluid system, featuring vortex shedding patterns, limit cycle oscillations and synchronisation, is studied both for swept sine and multisine excitation. A nonparametric nonlinear distortion analysis (FAST) is used to distinguish odd from even nonlinear behaviour. The information which is obtained from the nonlinear analysis is explicitly used in constructing a nonlinear model of the polynomial nonlinear state-space (PNLSS) type. The latter results in a reduction of the number of parameters and an increased accuracy compared to the generic modelling approach where typically no such information of the nonlinearity is used. The obtained model is able to accurately simulate time series of the transverse force coefficient over a wide range of the frequency–amplitude plane of imposed cylinder motion.

Seismic response analysis of a hydraulic fill dam

The seismic response of a highly heterogeneous hydraulic fill dam was evaluated by studying the natural frequencies of the first and second modes of vibration and analyzing the crest accelerations of different two-dimensional or 2D sections of the dam when subjected to two different earthquake excitations. The existing methods for determination of the natural frequency of earthen embankment structures can only be used to analyze the structural response at small strain levels. However, during seismic events, the natural frequency of an earthen dam is significantly affected by the nonlinear material behavior exhibited by the geomaterials at high strain levels. Hence, a novel method was devised to evaluate the strain-dependent natural frequency for plane strain 2D dam sections, using a synthesized multi-sine base excitation. The degradation of first and second natural frequencies of transverse vibration for all the 2D sections followed a linear trend when plotted against the respective crest’s root mean square strain on a logarithmic scale. The slope of the degradation curve was found to depend on the constituent material properties prevalent in the individual sections. The observed variations in natural frequencies and crest accelerations of the 2D dam sections were also used to assess the suitability of using two-dimensional plane strain analyses for studying the response of a long earthen dam having variability in material properties. Results indicate that there is a considerable chance of erroneous estimation of the seismic response of such highly heterogeneous earthen dams that are conventionally analyzed using plane strain models. A 2D analysis was found to merely capture the seismic response of the individual sections of the dam as independent entities while ignoring the stiffening or weakening effect of the adjacent neighboring segments that may have different material properties.

Standalone IoT Bioimpedance Device Supporting Real-Time Online Data Access

The use of electrical bioimpedance methods in medical and personalized healthcare applications requires sophisticated hardware and measurement settings. Here, we describe Zink , a standalone bioimpedance analyzer with Internet of Things (IoT) monitoring features. Zink can be connected to a secure wireless or local area network and accessed using any device with a Web browser and Internet access. Through a user-friendly Web-based access able to handle multiple simultaneous connections, the user(s) can perform single or multiple bioimpedance measurement(s) remotely. Zink supports the measurement of bioimpedance in both time and frequency domains using stepped-sine and multisine excitation signals. Embedded signal processing calculates bioimpedance from voltage and current signals using a coherent demodulation and the fast Fourier transform. Zink can also measure bioimpedance synchronized with either electrocardiogram (ECG) or electromyogram signals. The data is displayed on the user’s Web client from where it can be downloaded for further analysis. Zink full bandwidth is 100 mHz to 10 MHz and the average signal-to-noise ratio tested from 1 kHz to 1 MHz is 56 dB. The extended calibration method proposed here reduces the average magnitude error with respect to the existing three-parameter calibration approach by $0.6~\Omega $ (0.3%) measuring phantoms. Thoracic bioimpedance and ECG measurements on volunteers demonstrate the feasibility of detecting respiration changes while showing the results in real time on the user device’s Web browser. The performance, portability, and integration of Zink makes it a suitable standalone platform for medical and personalized health IoT monitoring applications.

Three-harmonic optimal multisine input power spectrum for bioimpedance identification

Objective: The attention towards optimal signals for measuring electrical bioimpedance (EBI) has increased recently due to the many advantages they offer such as, for example, reduced measuring time. Here, the design of a three-harmonic optimized multisine input power spectrum for measuring bioimpedance is considered. Approach: The approach is based on designing the input power spectrum multisine excitation by optimizing a scalar function of the information matrix using the Fricke–Morse model. Main results: Simple analytical equations are provided that can be adopted by the reader to optimize the multisine input power spectrum to satisfy any specific application-related EBI measurement. Significance: The presented signal may be a good choice of excitation signal in EBI applications where optimal excitation power spectrum is desired.

Application of Time-Resolved Multi-Sine Impedance Spectroscopy for Lithium-Ion Battery Characterization

Electrochemical Impedance Spectroscopy (EIS) is a valuable tool for the characterization of electrical, thermal and aging behavior of batteries. In this paper, an EIS measurement technique to acquire impedance spectra with high time resolution is examined, which can be used to gather impedance data during dynamic operating conditions. A theoretical analysis of the used multi-sine excitation signals is performed in detail and a practical measurement system is presented and validated. Afterwards, EIS measurements during the charging process of a lithium-ion battery are performed and discussed.

High-Accuracy Localization of Passive Tags With Multisine Excitations

This paper proposes an extensive study of multisine excitations to enable high-accuracy localization of battery-less tags, by harvesting the higher order harmonics, generated by the rectifier nonlinearity. Usually, these harmonics are either filtered out or terminated, to increase the conversion efficiency. A dual-mode rectifier with the output section splitted into two paths is designed. One dc path is the common one used to deliver the converted dc power to an optimum load and the second path is broadband and collects the higher harmonics obtaining an ultrawideband radiated signal to communicate with the receivers for tag localization. To this purpose, a variety of multisine excitation signals, with different tones, spacing among tones and bandwidth, is accurately evaluated to characterize the system-level localization performance. Both the modeled and experimental results are presented demonstrating the excellent performance of such a dual-mode rectifier, despite of the limited add-on circuitry if compared to those used in standard rectennas. For an average received power of −10 dBm, measurements show that the localization of a tag with centimeter-level accuracy can be achieved at more than 10 m distance from the receivers having a 4 dB noise figure.

Accounting for Unsteady-State Behavior during Electrochemical Impedance Spectroscopy

Electrochemical Impedance Spectroscopy (EIS) is one of the most effective methods to characterize an electrochemical system. Most of the common mathematical tools available for the correct interpretation of EIS data assumes a steady-state system. So, the system should have a constant voltage at a given current or vice versa during the duration of experiment. However, the system can deviate from a steady-state because of the perturbation applied during EIS measurement or because of the intrinsic chemistry of the system. For example, during charging or discharging of a battery at a constant current, voltage is drifting due to the changes in chemistry of the materials inside the battery. This drift in voltage can be significant especially during lower frequency scans that can lasts hours (<0.3 mHz). In such a case, extracting meaningful data from EIS can be challenging due to violation of the steady state condition. Here we show a reliable method to correct for the drift that might occur during such a low frequency measurement. This method takes advantage of the fact that phase angles in many systems are not affected by such an unsteady state behavior. Therefore, drift-free impedance modulus data is reconstructed from the phase angle spectrum with the help of a Z-HIT algorithm that applies the logarithmic form of the Hilbert transform to systems exhibiting ‘two-pole’ behavior. From this drift-free EIS data, the severity of drift can be analyzed. In addition, a better-fitted equivalent circuit model can be simulated. Furthermore, this method removes inaccuracy during multi-sine excitation combined with other tools. Applicability of this method in characterizing different electrochemical devices such as batteries, fuel cells and supercapacitors is presented. Keywords: EIS, Z-HIT, Battery, Supercapacitor, Fuel cells,

Waveform Approach for Assessing Conformity of CISPR 16-1-1 Measuring Receivers

An alternative approach for assessing the conformity of electromagnetic interference measuring receivers with respect to the baseline CISPR 16-1-1 requirements is proposed. The method’s core is based on the generation of digitally synthesized complex waveforms comprising multisine excitation signals and modulated pulses. The superposition of multiple narrowband reference signals populating the standard frequency bands allows for a single-stage evaluation of the receiver’s voltage accuracy and frequency selectivity. Moreover, characterizing the response of the weighting detectors using modulated pulses is more repeatable and less restrictive than the conventional approach. This methodology significantly reduces the amount of time required to complete the verification of the receiver’s baseline magnitudes, because time-domain measurements enable a broadband assessment while the typical calibration methodology follows the time-consuming narrow band frequency sweep scheme. Since the reference signals are generated using arbitrary waveform generators, they can be easily reproduced from a standard numerical vector. For different test receivers, the results of such assessment are presented in the 9 kHz–1 GHz frequency range. Finally, a discussion on the measurement uncertainty of this methodology for assessing measuring receivers is given.

A novel fractional-order model and controller for vibration suppression in flexible smart beam

Vibration suppression represents an important research topic due to the occurrence of this phenomenon in multiple domains of life. In airplane wings, vibration can cause discomfort and can even lead to system failure. One of the most frequently used means of studying vibrations in airplane wings is through the use of dedicated flexible beams, equipped with sensing and actuating mechanisms powered by suitable control algorithms. In order to optimally reject these vibrations by means of closed-loop control strategies, the availability of a model is required. So far, the modeling of these smart flexible beams has been limited to deliver integer order transfer functions models. This paper, however, describes the mathematical framework used to derive a fractional-order impedance lumped model for capturing frequency response of a flexible beam system exposed to a multisine excitation. The theoretical foundation stems from fractional calculus applied in combination with transmission line theory and wave equations. The simplified model reduces to a minimal number of parameters when converging to a limit value. It is shown that the fractional-order model outperforms an integer order model of the smart beam. Based on this novel fractional-order model, a fractional-order $$\hbox {PD}^\mu $$ controller is then tuned. The controller design is based on shaping the frequency response of the closed-loop system such that the resonant peak is reduced in comparison to the uncompensated smart beam system and disturbances are rejected. Experimental results, considering a custom-built smart beam system, are provided, considering both passive and active control situations, showing that a significant improvement in the closed-loop behavior is obtained using the proposed controller. Comparisons with a fractional-order $$\hbox {PD}^\mu $$ controller, tuned according to classical open-loop frequency domain design specifications, are provided. The experimental results show that the proposed tuning technique leads to similar results as the classical approach. Thus, the proposed method is a viable alternative, being based on closed-loop specifications, which is more intuitive for practitioners.

A Two-Port Nonlinear Dynamic Behavioral Model of RF PAs Subject to Wideband Load Modulation

This work presents a full two-port, i.e., double input-double output, behavioral modeling approach suitable for radio frequency power amplifiers (PAs) in the presence of dynamic load modulation (DLM). The formulation of the model, based on a first-order approximation of a modified Volterra series, accounts for the nonlinear distortion determined by large-signal operation under mismatched conditions, and also for the memory effects stimulated by a modulated PA input signal, or by the dynamic variations of the PA load. By following an exhaustive procedure defined in the frequency domain, the model of a general purpose commercial PA is extracted over 160 MHz of modulation bandwidth (BW) with nonlinear vector network analyzer measurements. Validation results under 20-MHz BW multisine excitation and injected 80-MHz BW multisine load modulation show improved prediction capabilities with respect to quasi-static or single-input descriptions, allowing for reliable system-level simulations in the presence of DLM.

Odd Random Phase Electrochemical Impedance Spectroscopy to Study the Corrosion Behavior of Hot Dip Zn and Zn-Alloy Coated Steel Wires in Sodium Chloride Solution

Electrochemical impedance spectroscopy (EIS) is a very popular technique to investigate the corrosion behavior of metals and alloys in electrolytes. To interpret the EIS data, an equivalent electrical circuit (EEC) is built and the corrosion behavior can be explained on the basis of the values obtained for each element of the EEC after fitting the impedance data. Hence, the reliability of the interpretation greatly depends on the selection of the EEC for the impedance modeling. In this work, odd random phase electrochemical impedance spectroscopy (ORP-EIS) is used to investigate the corrosion behavior of Zn, Zn-Al and Zn-Al-Mg hot dip coated steel wires in 0.1 M NaCl. ORP-EIS uses a multisine excitation signal to obtain the impedance response of the electrochemical system. It is faster than conventional EIS as well as provides accurate information about linearity, stationarity and noise distortions of the system during the measurement. This is used to optimize the experimental conditions and to evaluate the correctness of the data modeling. The corrosion behavior of the metallic coated steel wires is quantified by EIS modeling. The validity of the proposed EEC is assessed based on the physical phenomena as well as the statistical evaluation of the modeling results.

Nonparametric Analysis of Nonlinear Distortions for Biomolecular Systems

System identification of biomolecular circuits is a challenging problem, including due to the nonlinearities that are often present in them. The extent to which these nonlinearities contribute to the overall behaviour of the biomolecular circuit is unclear. Here, we address this issue for simple biomolecular circuit models by exploiting the properties of broadband random phase multisine excitations. We analysed the classical models of a two-state signaling system, an enzymatic signaling system, and of a transcriptional feedback circuit for the presence of nonlinear distortions at certain parametric settings and studied their dependence on the input parameters. These results should help the modeller in quantifying the effect of nonlinearities and assessing the validity of the linear models at a particular operating condition.

A Novel Multi-Sine Excitation Procedure for Impedance Spectroscopy Supports Automatic Drift Correction and Online Error Determination

The traditional way to measure impedance using single-sine (monochromatic) excitation is the most transparent and robust way to find reliable EIS data. Compared to the time saving polychromatic (i.e. multi-sine) excitation, the advantage of single-sine excitation is the unequivocal assignment of harmonic content in the response signal to unwanted interference. Systematic analysis of these harmonics allows for the determination of a reliable measurement variance for every single data sample immediately after raw data collection is complete. For decades, such a procedure named “Weighted Harmonics Autocorrelation” has proven its benefit for the EIS instruments of the authors group [1]. Another helpful feature is owed to the periodicity of the monochromatic excitation: unwanted time drift contributions can be calculated from succeeding periods of the response signal for the reconstruction of the drift-free response. This allows for an automatic drift correction [2]. These valuable features are hardly achievable using standard multi sine techniques. Here, even in the absence of interference, the response signals are neither periodic nor free of harmonics. In spite of the fact that monochromatic techniques have the better relationship between information density and time effort [3], it is sometimes preferable to use multi-sine whenever the total measurement time is crucial for practical reasons. In this poster, a novel multi-sine excitation method will be presented that keeps the advantages of automatic drift correction and online error determination analogous to the monochromatic single-sine procedure. Keywords: EIS, error determination, drift correction, multi-sine, single-sine

Method to Increase the Speed of EIS Series Measurements on Battery Stacks during Cycling While Avoiding Dramatic Loss of Measurement Accuracy

The amount of time expended while running experiments is a crucial factor to consider when screening new materials as candidates for improving battery performance. Electrochemical impedance spectroscopy (EIS) is among the most appropriate evaluation tools for collecting in-situ information about electrochemical processes occurring inside battery systems. However, during charging and discharging cycles, the electrodes, electrolytes, and related materials comprising battery systems are continuously undergoing changes in state over time, even at timescales shorter than the amount of time required to run a single charge-discharge experiment. For instance, voltage is changing during constant current load. Here, the application of EIS can become restricted because the prerequisite of steady state as a foundational principle to interpret the resulting EIS spectra is violated due to changes of state in between the time it takes to sweep through frequencies of interest. Trying to yield significant results accounting for drift effects requires implementing particular modeling measures. This abstract presents an ensemble of solutions to combat this issue. Parallel EIS, automatic drift correction of the measured time dependent signals, time interpolation by series measurements, and the application of the Z-HIT algorithm as post-processing of the data are the tools of choice. Simultaneous EIS is an effective time saving procedure. Otherwise, sequential EIS evaluation of n single cells in a stack increases time consumption by the factor n. Also, comparing the results for each individual cell to other cells is no longer directly comparable to an exact degree because the measurement drifts due to time effects are difficult to correct for. Second, precautions must be provided during the data acquisition phase in order to suppress the erroneous assignment of drift signals to the system response [1]. Furthermore, “non causal” spectra in the meaning of the Kramers-Kronig relations can be converted into correct spectra by interpolation of spectra series vs. time and, by removal of residual non-causalities with the help of the Z-HIT transform, which has the capability to reconstruct drift-affected data [2]. In many cases, the user would favor the comfortable possibility to significantly reduce the time for recording the EIS spectra by the application of multi-sine excitation. However, conventional multi-sine excitation normally is accompanied by significant losses of accuracy. An advanced technique provides the features of automatic drift correction and error detection known from single-sine excitation [3]. As a result, substantial loss in accuracy can be avoided. Experimental data obtained from a four-cell Li-FePO4 stack (13.2 V / 40 Ah) using this new multi-sine algorithm will be presented upon approval of this abstract for presentation. Keywords: Multi-sine, Battery stacks, EIS, True parallel measurements, Z-HIT

Flight-Test Techniques for Quantifying Pitch Rate and Angle-of-Attack Rate Dependencies

Three different types of maneuvers were designed to separately quantify the pitch rate and angle-of-attack rate contributions to the nondimensional aerodynamic pitching moment coefficient. These maneuvers combined pilot inputs and automatic multisine excitations, and they were demonstrated with the subscale T-2 and Bat-4 airplanes using the NASA Airborne Subscale Transport Aircraft Research flight-test facility. Stability and control derivatives (in particular, and ) were accurately estimated from the flight-test data. These maneuvers can be performed with many types of aircraft, and the results can be used to improve physical insight into the flight dynamics, facilitate more accurate comparisons with wind-tunnel experiments or numerical investigations, and increase simulation prediction fidelity.

Measurement and Analysis of Effect of Ionic Conductivity on Nonlinear Behavior of All-Solid-State Battery

Now a days all solid state batteries draw attentions of researchers, battery and vehicle developers due to its high energy density characteristic and safety issues. The numerous benefits make solid-state batteries more convenient for automotive industries to invest. However some issues of solid state batteries such as low ionic conductivity and interface between electrodes and solid electrolyte remain which need more in depth research and investigations during coming years. This paper tries to introduce a method to analyze and evaluate the effects of solid electrolyte conductivity on the battery linear and nonlinear behaviors. In the proposed method the measured current and voltage of the battery in frequency domain are analyzed and linear part as well as the nonlinear distortions is extracted. In order to evaluate the ionic conductivity, two all-solid-stat coin cells are prepared. Both cells have same cathode and anode materials, LiNbO3-coated LiCoO2 and graphite respectively. Surface area is 1cm2 and the thickness of each part is also similar. Capacity of each cell is 0.67 mAh. However the only difference is ionic conductivity inside of the cathode layer. The ionic conductivity of cathode layer has been controlled by changing solid electrolyte (SE) materials; in cell number 1, LiI-Li2S-P2S5 glass exhibiting ionic conductivity (σ 25ºC) of 10-3 S/cm was equipped, while for second cell, the solid electrolyte of γ-Li3PS4 (σ25ºC ≈ 10-5S/cm) was used. In the proposed method several sinusoidal waves with same amplitude and different frequencies and also different phase realizations are added together in one signal, which is called multisine excitation. The zero signal means and overall SoC remains constant during the experiment. Furthermore charge and discharge signals can be distinguished and analyzed, separately. Thanks to frequency domain analysis, every excited waves and its response can be analyzed and also corresponding impedance can be calculated. A nonlinear system can be approximated by a linear dynamic system, which is called the best liner approximation. This linear part (linear part of battery impedance) is approximated from the voltage response to multisine excitation current in frequency domain. Besides the noise and transient, the main source of signal distortion in a measurement is nonlinear behavior of the battery which this paper tries to find the link between distortions and ionic conductivity of cathode layer. In this paper 2 different multisine realizations with different current amplitudes at 2mA and 15mA are designed and applied to both cells at 60°C ambient temperature. Figure 1 shows the input cell current for15mA case. The signal shape suggests that it is random but if we look at it in frequency domain, it is made of specified frequencies with exact same amplitudes. The purpose of choosing these two cases is to evaluate how battery voltage and impedance are affected by ionic conductivity of cathode layer in low and high currents. The measured voltages for both cases are shown in figure 2a and 2b. As expected, the voltage amplitude is much bigger for cell 2 due to the higher impedance. However the interesting point is the voltage variation during charge and discharge, which is different for cell 2 at low and high currents. According to figure 2.a when the input current is 2mA, the voltage drop during discharge is higher than charge if the blue curve is considered as a reference. However when current has been increased to 15mA, the voltage during charge has been increased more compared with the voltage during the discharge phase. In the way that voltage variation seems more balanced than the 2mA case, which is due to the ionic conductivity reduction. For calculating the approximated linear impedance and nonlinear distortions in each case, the measured current and voltage have been transformed to frequency domain. Based on the mathematical and statistical methods the best linear approximation of impedance and nonlinear distortion on the excited sine waves has been calculated, which has been indicated in figure 3. According to the figure 3a when the current is 2mA, the linear part of the impedance is increased to 15 times in case of cell2 while nonlinear distortion has been increased to 200 times. But when the current increases to 15mA (figure 3.b) the linear part of the impedance increases to around 14 times and nonlinear distortion changes only 40 times more due to the symmetrical pattern, which has been discussed at figure 2b. Such analysis will formulate the nonlinear effects of ionic conductivity on SSB behaviors. This method will be used for developing nonlinear models which is useful for optimized cell manufacturing process. Figure 1

(Keynote) Electrochemical Impedance Spectroscopy Characterization of Advanced Materials for Energy

Several electrochemical energy technologies (batteries, fuel cells, supercapacitors, …) have been developed. Many have been commercialized, but a large number is still under development. Systems are optimized in terms of life time, performance and cost, and new systems are being designed.The electrode and electrolyte materials must have the required characteristics with respect to ionic and/or electronic transport properties, electrochemical properties, chemical stability, compatibility with other materials, thermal properties, … To be able to tailor the energy materials, characterization of their electrochemical behavior is of prime importance. The electrochemical behavior is influenced by a high number of processes, all occurring at a different rates. Knowing the quantitative mechanism of an electrochemical system is an essential step in the prediction of its behavior. Electrochemical Impedance Spectroscopy (EIS) is the designated experimental technique to that purpose. Yet, identifying and quantifying the characteristic parameters of the reactions governing the system from the experimental EIS results is complex.In our group, we developed a new approach to EIS [1-4]. It consists of an integrated measuring and modelling methodology based on an odd random phase multisine excitation signal (ORP-EIS) and on mathematical modeling via parameter estimation. The mathematical model representing the system is formulated on the relations between the input and output to the system, including the model parameters. These parameters stand for inherent properties of the system; they describe the stability and control the behavior of the system. This methodology is applied in this paper for the investigation of two types of energy materials.The first application concerns Lithium Ion Batteries (LiB’s), used for Hybrid Electrical Vehicles (HEV’s). This study contributes to the quest for electrode materials with high cycling stability. Li4Ti5O12 (LTO) has been proposed as a promising candidate to replace the market-dominating carbon-based anodes (graphite and amorphous carbon). Aged batteries are post-mortem analyzed by EIS to have insight into the origin of the aging phenomena. Reliable impedance modelling is performed to quantitatively address the origin of the rising impedance.The second application is in the field of Solid Oxide Fuel Cells (SOFC’s). Solid electrolytes exhibit electrical conductivity due to ionic conduction through the crystalline structure. For their use in SOFC’s, a sufficient electrical conductivity is achieved at high temperatures. To reduce the application temperature, research is dedicated to increase the conductivity of the ceramic material by heterogeneous doping or reducing the grain size or the film thickness. How the microstructure of the material affects the electrical conduction is still a matter of debate in literature. A good understanding of the relationship between microstructure and ion conductivity would open the possibility to engineer advanced materials for SOFCs. Oxides with fluorite structure are measured by EIS at low to high temperatures, varying the oxygen flow. Thin film and bulk electrolytes of doped ceria with different grain size and dopants are investigated. [1] Y. Van Ingelgem, E. Tourwé, O. Blajiev, R. Pintelon, A. Hubin, Electroanalysis 21(6) (2009) 730[2] T. Breugelmans, J. Lataire, T. Muselle, E. Tourwé., R. Pintelon, A. Hubin, Electrochimica Acta 76 (2012) 375 [3] L. Fernández Macía, M. Petrova, T. Hauffman, T. Muselle, T. Doneux, A. Hubin, Electrochimica Acta, 140 (2014) 266[4] L. Fernández Macía, M. Petrova, A. Hubin, Journal of Electroanalytical Chemistry, 737 (2015) 46

Multimodal vibration damping using energy transfer

The vibration control using the piezoelectric elements is an area interesting for many industrial sectors. Within this framework, we propose an improved control technique based in synchronized switch damping by energy transfer. It realizes the energy transfer using storage capacitances and switches synchronized with the structure modal coordinates or piezo-voltages. These switches produce either a voltage inversion on the piezoelements for damping or energy extraction purposes, or oscillating discharges between the piezoelements and the storage capacitances for energy transfer. This new method has an improvement in the modal damping technology SSDI-Max. Their performance is simulated with a model representative of a clamped plate with four piezoelectric elements coupled with the structural modes while taking into account realistic transfer losses. The damping effect is simulated in multi-modal with pulse or multi-sine excitation.