Maximum Tip Displacement Research Articles

Optimising Sodium Borohydride Reduction of Platinum onto Nafion-117 in the Electroless Plating of Ionic Polymer–Metal Composites

The effects of process parameters on the electroless plating of ionic polymer–metal composites (IPMCs) were studied in this work. Specifically, the NaBH4 reduction of platinum onto Nafion-117 was characterised. The effects of the concurrent variation of NaBH4 concentration, stir time and temperature on surface resistance were studied through a full factorial design. The three-factor three-level factorial design resulted in 27 runs. Surface resistance was measured using a four-point probe. A regression model with an R2 value of 97.45% was obtained. Surface resistance was found to decrease with increasing stir time (20 to 60 min) and temperature (20 to 60 °C). These responses were attributed to increased platinisation rates, resulting in more uniform electrode deposition, confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDAX) analysis. Surface resistance decreased, going from 1% to 5% NaBH4 concentration, but increased from 5% to 10% concentration. This behaviour was attributed to surface morphology: increased grain size inducing porous electrodes, in line with findings in the literature. The maximum tip displacement, measured through a computer vision system, as well as the maximum blocking force, measured through an analytical balance setup, were obtained for all 27 samples. The varying results were discussed with regards to surface and cross-sectional SEMs, alongside EDAX analysis.

Improved non-contact vibration measurement via acceleration-based blade tip timing

The conventional displacement-blade tip timing (D-BTT) measurements often rely on Once-Per-Revolution (OPR) sensors to compute expected or theoretical time of arrival (TOA) based on rotational speed. However, integrating OPR sensors within the confined space of aero-engines presents challenges, and estimating theoretical TOA introduces computational errors, particularly for low-amplitude, high-frequency blade vibrations. This paper presents the Acceleration-based Blade Tip Timing (A-BTT) method as a solution. Building upon A-BTT, the acquisition of blade tip vibration acceleration serves not only to capture rapid changes in vibration but also to offer richer data for precise measurement of high-frequency blade vibrations. With only three blade tip timing sensors recording actual TOA without an OPR sensor, A-BTT eliminates the need for estimating expected TOA, thus mitigating calculation errors. Furthermore, by analyzing the relationship between maximum blade tip vibration acceleration and displacement during synchronous blade vibration, vibration parameters, such as natural frequency, can be directly identified without prior information such as engine orders. Simulation and experimental results validate the efficacy of the A-BTT method, demonstrating its successful application to specific aero-engine compressor rotor blades.

Multiple-Bird-Strike Probability Model and Dynamic Response of Engine Fan Blades

Bird strikes pose one of the most significant threats to aviation safety, often leading to substantial loss of life and economic damage. Many bird strike incidents involve multiple birds. However, in previous bird strike studies, the problem of multiple bird strikes has often been neglected. In this paper, the bird slicing process of a rotating engine fan is examined, and a probability model is introduced to assess the risk of multiple impacts on the fan blades. In addition, this paper utilized an implicit–explicit calculation method. The parameters of blade root stress, tip displacement, plastic deformation, and energy were selected to investigate the effects of the time interval and strike position of a bird strike on the dynamic response of and damage to the blades. The results indicated that the position of bird strikes has a more pronounced effect on blade damage compared to the time interval between impacts. Damage to a blade is most severe when the blade root is struck multiple times. Multiple bird strikes may not always lead to a significant increase in maximum blade tip displacement, and may even have a dampening effect.

Analyzing the structural behavior of conducting polymer actuators and its interdependence with the electrochemical phenomenon

This work reports the deformation behavior of a conducting polymer, poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS)/bacterial cellulose (BC) bi-layered cantilever type actuator. Herein, it was found that the type (i.e. bending and torsion) of deformation of (PEDOT:PSS)/BC actuator was non-trivially dependent on its dimensions (width and length). Increasing the actuator’s width resulted in larger torsional deformation along the longitudinal axis against the increased area moment of inertia. The actuator with a width of 7.75 mm rotates ∼90° (i.e. the bottom cross-section) with respect to its top end. It was noticed that torsional motion dominated the deformation when the bending in the lateral direction was restricted. Further, the maximum tip displacement trivially increased with the length from 5.40 mm for an actuator of length 10 mm–12.40 mm for a length of 59.00 mm. However, the curvature of bending, which was proportional to the induced strain, was higher for smaller lengths. The change in the dimension of the actuator involves change in the stress field distribution (i.e. induced through electrochemical process) and simultaneously the resistance to deformation, resulting in a non-trivial relationship between the deformation and the dimensions. This can be advantageous from the design perspective in realizing different types of motions without incorporating additional materials. Structural theory and electrochemical impedance Spectroscopy were used to understand the mechanism of deformation dependence on the dimensions. The electrochemical impedance spectroscopy results indicated that electrolytic ions penetrate deeper into the PEDOT:PSS layer for actuators of smaller lengths. The increase in the curvature of the actuator could be explained based on the constancy of the strain produced due to the volume change per ion. The torsional motion increased because the stresses were being induced further away from the center in wider actuators. These observations and analyses reveal the interdependence of the structural behavior (i.e. dimensions) and the electrochemical phenomenon (i.e. deformation) in a conducting polymer actuator.

Conceptual Design of a Robotic Ground-Aerial Vehicle with an Aeroelastic Wing Model for Mars Planetary Exploration

This paper presents the technical barriers and an analysis to advance the conceptual development of novel robotic ground-aerial vehicles (RGAVs) for exploration missions to Mars prior to human arrival and the establishment of a base. The concept for RGAVs for Mars planetary exploration is novel, and will require innovations that are at various stages of development or use by the aerospace community. The RGAV concept will utilize inflatable wing technology, which increases the flexibility of the wing, and thus the possibility of structural dynamic instabilities that must be studied in the context of the Martian atmosphere. An aeroelastic model for wing bending is proposed, which considers wind gusts where the change in wind direction is up to ±6° from the mean, and a turbulence intensity of up to 20%. Their effect on the bending displacement of a semi-elastic wing is quantified, resulting in a maximum wing tip displacement of 16.2 cm. Low-fidelity computational aerodynamic analysis is performed using OpenVSP (3.31.1, NASA, Washington, DC, USA) to compute mean aerodynamic loads during cruise conditions at a cruise Mach number of 0.70. Finally, a non-linear adaptive control system is proposed for the longitudinal aerial dynamics and a proportional integral derivative (PID) controller is outlined for the ground roving lateral dynamics.

Multi-Objective Structural Optimization of a Composite Wind Turbine Blade Considering Natural Frequencies of Vibration and Global Stability

Aspects concerning resonance and global stability of a wind turbine blade must be carefully considered in its optimal design. In this paper, a composite wind turbine blade with an external geometry based on the NREL 5 MW model was subjected to multi-objective structural optimization considering these aspects. Four multi-objective structural optimization problems are formulated considering the blade mass, the maximum blade tip displacement, the natural frequencies of vibration, and the critical load factor as objective functions. The design variables are the number of plies, material, and fiber orientation. The design constraints are the materials’ margin of safety, the blade’s allowable tip displacement, and the minimum load factor. The blade model is submitted to the loads determined by the actuator lines theory and discretized in a finite element parameterized model using the Femap software according to geometric design variables. Among many multi-objective evolutionary algorithms available in the literature concerning evolutionary computation, the NSGA-II is the adopted evolutionary algorithm to solve the multi-objective optimization problems. Pareto fronts are obtained and performance indicators are used to evaluate the distribution of the non-dominated solutions. Multi-criteria decision-making is used to extract the solutions from the Pareto fronts according to the decision-maker’s preferences. The values of the objective functions, design variables, and constraints are presented for each extracted solution. The proposed study is expected to contribute to the multi-objective optimization and the structural design of wind turbine blades.

Design and Control of Monolithic Compliant Gripper Using Shape Memory Alloy Wires.

This paper presents the design, fabrication and testing of a shape memory alloy (SMA)-actuated monolithic compliant gripping mechanism that enables translational motion of the gripper tips for grasping operation suitable for micromanipulation and microassembly. The design is validated using a finite element analysis (FEA), and a prototype is created for experimental testing. The reported gripping structure is simple and easy to build and design. The gripper is demonstrated to have a displacement amplification gain of 3.7 that allows maximum tip displacement up to 1.2 cm to possess good handling range and geometric advantage which cannot be accomplished by conventional grippers. The position of the gripper tip is predicted from the variation in the electrical resistance of the SMA wire based on the self-sensing phenomena. Self-sensing actuation of the SMA allows the design of a compact and lightweight structure; moreover, it supports the control loop/scheme to use the same SMA element both as an actuator and sensor for position control. The geometrical dimensions of the SMA wire-actuated monolithic compliant gripper is 0.09 m × 0.04 m and can be operated to handle objects with a maximum size of 0.012 m weighing up to 35 g.

Platinum-coated silicotungstic acid-sulfonated polyvinyl alcohol-polyaniline based hybrid ionic polymer metal composite membrane for bending actuation applications

An electro-stimulus-responsive bending actuator was developed by synthesizing a non-perfluorinated membrane based on silicotungstic acid (SA), sulfonated polyvinyl alcohol (SPVA), and polyaniline (PANI). The membrane was developed via solution casting method. The dry membrane SA/SPVA showed a sufficient ion-exchange potential of 1.6 meq g−1 dry film. The absorption capacity of the membrane after almost 6 h of immersion was found to be ca. 245% at 45 °C. The electroless plating with Pt metal was carried out on both sides of the membrane that delivered an excellent proton conductivity of 1.9 × 10−3 S cm−1. Moreover, the scanning electron microscopy (SEM) was conducted to reflect the smooth and consistent surface that can prevent water loss. The water loss capacity of the membrane was found to be ca. 33% at 6 V for 16 min. These results suggest a good actuation output of the ionic polymer metal composite (IPMC) membrane once the electrical potential is applied. The electromechanical characterization displayed a maximum tip displacement of 32 mm at 3 V. A microgripping device based on multifigure IPMC membrane may be developed showing a good potential in micro-robotics.

Rotordynamics analysis of solar hybrid microturbine for concentrated solar power

Microturbine based on a parabolic dish solar concentrator runs at high speed and has large amplitudes of subsynchronous turbo-shaft motion due to the direct normal irradiance (DNI) fluctuation in daily operation. A detailed rotordynamics model coupled to a full fluid film radial or journal bearing model needs to be addressed for increasing performance and to ensure safe operating conditions. The present paper delivers predictions of rotor tip displacement in the microturbine rotor assembly supported by a journal bearing under non-linear vibrations. The rotor assembly operates at 72 krpm on the design speed and delivers a 40 kW power output with the turbine inlet temperature is about 950 °C. The turbo-shaft oil temperature range is between 50 °C to 90 °C. The vibrations on the tip radial compressor and turbine were presented and evaluated in the commercial software GT-Suite environment. The microturbine rotors assembly model shows good results in predicting maximum tip displacement at the rotors with respect to the frequency and time domain.

Design and performance assessment of a distributed vibration suppression system of a large flexible antenna during attitude manoeuvres

One of the major needs of future Earth Observation satellites is to fulfil high demanding pointing requirements when using instrumentations supported by or mounted at the end of very large flexible truss structures. Those spacecraft often call for the capacity of performing fast and precise manoeuvres without exceeding deformation requirements related to their flexible parts. On-board mechanical disturbances can be generated by an attitude control equipment and pointing mechanisms. In this perspective, a network of smart actuators/sensors can be mounted on a passive structure to counteract undesired elastic vibrations. In this paper, the problem of micro-vibration control for a spacecraft equipped with a very large flexible antenna is addressed. The instrument is sustained by an active frame hosting an optimally distributed network of actuators and sensors dedicated to vibrations suppression. The fully coupled 3-D equations for a flexible spacecraft subjected to forces of the orbital environment are derived taking the presence of the smart materials into account. The 3-D flexible structure model is developed and validated via FEM formulation by using commercial codes. The model is then reduced to obtain a system to be easily handled by control systems algorithms. A placement strategy to identify the best location for vibration control devices is carried out by using Gramian-based techniques. Typical profiles of attitude manoeuvres are then simulated by applying a control torque while simultaneously suppressing unwanted vibrations. To achieve a high performance, feedback methods are implemented to coordinate the actuators and ensure that maximum tip displacement requirements are satisfied during operations.

Structural Performance of Damaged Open-Web Type SRC Beam-Columns after Retrofitting

The structural performance of damaged open-web type of steel encased reinforced concrete (SRC) beam-columns after retrofitting was experimentally investigated. The experimental parameters were the open-web type of the encased steel and the maximum tip displacement of the columns during the initial loading. First, each column was cyclically loaded to the targeted displacement. Subsequently, the test columns were retrofitted and reloaded. The damaged portions of each column were retrofitted with the polymer cement mortar, and the epoxy resin was injected into the cracks. The experimental results indicated that the measured stiffness of the retrofitted columns was lower than the initial ones, while the displacements experienced in each column were different. The lower stiffness might be attributed to deterioration of the concrete rigidity, low rigidity of the resin and imperfect injection of the resin. Numerical analyses were also conducted to evaluate the retrofitted column behavior. The effect of the strain hysteresis of concrete at the first loading was considered for the behavior at the second loading. The analytical results predicted the experimental behaviors fairly well, which implies the validity of the analytical methods presented in this paper for evaluating the structural performance of the retrofitted SRC columns.

Characterization and actuation behavior of SPS/SGO ion exchange polymer actuator based on PEDOT: PSS/SGO composite electrode

ABSTRACTThis paper studied the fabrication of new hybrid-type poly(3,4- ethylene dioxythiophene) (PEDOT)/sulfonated graphene oxide electrode-based polymer actuator produced by film casting method. Sulfonated Poly(1,4-phenylene ether-ether sulfone) (SPS) ion-exchange polymer membrane-based ionic polymer composite actuators were fabricated using the different concentration of SGO. The characterization and actuation were demonstrated. By altering SGO concentration, four different SPS based membrane actuators were analyzed. The effects of SGO concentration on the morphology, proton conductivity, ion exchange capacity, and water uptake capability were studied. The maximum tip displacement and force by varying concentration of SGO were evaluated for the actuation performance.

Towards radio transceiving in-vivo nano-robots

An implementable model and simulation of an oscillating Carbon Nanotube (CNT) for radio communication in nanorobots is presented. A cylindrical CNT cantilever beam, operating under constant direct current supply, is forced to continuously oscillate by applying a controlled electromagnetic force. Oscillation parameters are computed and simulated, including the maximum tip displacement, the acting electromagnetic force and the dynamic response of the CNT, yielding a frequency of oscillation. We develop a model to predict the oscillation frequency of the cantilever beam based on its properties, including the device geometry. The primary functional component of the system is the electrically chargeable cantilever beam which oscillates due to its electric charge and discharge, where the discharge happens when the cantilever moves closer to the counter electrode. Thus, we provide an implementable design of in-vivo transceiver, suitable for future large-scale applications based on radio communicating nanorobots. A swarm of such nanorobots can be regarded as implementable programmable matter.

Development of a Novel Modular Compliant Gripper for Manipulation of Micro Objects.

This paper proposes a modular gripping mechanism for the manipulation of multiple objects. The proposed micro gripper combines traditional machining techniques with MEMS technologies to produce a modular mechanism consisting of a sturdy, compliant aluminium base and replaceable end-effectors. This creates an easily-customisable solution for micro manipulation with an array of different micro tips for different applications. We have provided the kinematic analysis for the gripper to predict the output and have also optimised design parameters based on FEA (finite element analysis) simulation and the effects of altering flexure beam lengths. The gripper is operated by a piezo actuator capable of 18 m displacement at 150 V of applied DC voltage. This is then amplified by a factor of 8.1 to a maximum tip displacement of 154 m. This is achieved by incorporating bridge and lever amplifying techniques into the design. An initial experimental analysis of the micro gripper is provided to investigate the performance of the micro gripper and to gauge the accuracy of the theory and simulation through comparison with experimental results.

The effect of gold electrode thicknesses on electromechanical performance of Nafion-based Ionic Polymer Metal Composite actuators

The effect of gold electrode thickness (10, 27, 45, 67 and 80 nm) on the electromechanical performance of Nafion-based Ionic Polymer Metal Composite (IPMC) actuators was investigated in this study. The mechanical, morphological, electrical properties and electroactive behaviors of IPMC under direct current voltage (DC) and alternating voltage (AC) were examined. The tip displacement and maximum blocking force of actuators under various electrical stimulations were measured. In order to define transient response characteristics and quasi-steady state value of the actuators, DC excitations of 1, 3, 5, 7 and 9 V were used. Besides, to define bandwidth of the actuator samples, square wave excitation with magnitudes of 3, 5, and 7 V and frequencies of 0.1, 0.25, 0.5, 1, and 2 Hz were applied to actuator samples. The actuator having a gold electrode thickness of 45 nm produced maximum tip displacement among all actuators for all excitation DC voltages. In the square wave experiments, the higher cutoff frequencies were observed for the actuators with 27 and 45 nm electrode thicknesses. The blocking force of IPMC increased with increasing gold electrode thickness from 10 nm to 45 nm and decreased with increasing gold electrode thickness from 45 nm to 80 nm.

The influence of electrodeposited conducting polymer electrode structure on the actuation performance of muscle-like ionic actuators

This study demonstrates the influences of physical and electrochemical characteristics of conducting polymer (CP) film as electrode material on the actuation performances of ionic actuators which is of considerable interest for increasing the application of metal-free ionic actuators in different fields. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and polypyrrole (PPy) were applied as electrode materials in fabrication of metal-free Nafion-based electromechanical actuators. These polymers were electrochemically deposited on both surfaces of polymeric membrane and variations in physical, electrochemical and electromechanical characteristics of actuators were followed as a function of the applied polymer type. Pt-electrode Nafion based actuators were prepared as standard. Electrochemical studies revealed that the mechanism of actuation is mainly related to double-layer capacitance (Cdl) and that faradic capacitance (CF) plays less significant role. PPy-electrode actuators showed higher ion and water permeability due to formation of thinner electrode layers with finer morphology. The largest tip displacement (25 mm) was obtained in PPy-electrode actuators, in response to 6 V dc potential. These actuators exhibited the highest specific capacitance of 146.26 m F.cm−2 and capacitance retention of 87.41% after 100 cycles. The electro-mechanical energy efficiency and the maximum tip displacement of PPy-electrode actuators were 46.42% and 31.57% higher than that considered for PEDOT:PSS-electrode actuators, respectively.

3D printed electrically-driven soft actuators

Soft robotics is an emerging field enabled by advances in the development of soft materials with properties commensurate to their biological counterparts, for the purpose of reproducing locomotion and other distinctive capabilities of active biological organisms. The development of soft actuators is fundamental to the advancement of soft robots and bio-inspired machines. Among the different material systems incorporated in the fabrication of soft devices, ionic hydrogel–elastomer hybrids have recently attracted vast attention due to their favorable characteristics, including their analogy with human skin. Here, we demonstrate that this hybrid material system can be 3D printed as a soft dielectric elastomer actuator (DEA) with a unimorph configuration that is capable of generating high bending motion in response to an applied electrical stimulus. We characterized the device actuation performance via applied (i) ramp-up electrical input, (ii) cyclic electrical loading, and (iii) payload masses. A maximum vertical tip displacement of 9.78 ± 2.52 mm at 5.44 kV was achieved from the tested 3D printed DEAs. Furthermore, the nonlinear actuation behavior of the unimorph DEA was successfully modeled using an analytical energetic formulation and a finite element method (FEM).

Electrochemical and Electromechanical Study of Carbon-Electrode-Based Ionic Soft Actuators

In the current work, metal-free Vulcan carbon/MWCNT (V/M) based soft actuators were fabricated by physical deposition of V/M ink on both faces of Nafion membrane. The effects of the weight percentage of MWCNTs on the electromechanical and electrochemical behaviors of actuators were studied through extensive experiments. Morphological characterization showed that the electrode structure of actuators changed considerably by changing the MWCNT content of the electrode layer. Electrochemical studies revealed V/M electrodes improve the ionic conduction and capacitive behavior of the Nafion-based actuators. The electrochemomechanical performance of actuators was compared by measuring maximum tip displacement, rate of displacement, durability, waveform analysis, and specific electromechanical energy efficiency. The highest tip displacement (44.5 mm) was obtained in actuators comprising 20 wt % MWCNTs. These actuators showed considerably higher ionic conductivity (26.9 mS/cm) and capacitive characteristic (45.2 μ...

Bending of a Tapered Rod: Modern Application and Experimental Test of Elastica Theory

A tapered rod mounted at one end (base) and subject to a normal force at the other end (tip) is a fundamental structure of continuum mechanics that occurs widely at all size scales from radio towers to fishing rods to micro-electromechanical sensors. Although the bending of a uniform rod is well studied and gives rise to mathematical shapes described by elliptic integrals, no exact closed form solution to the nonlinear differential equations of static equilibrium is known for the deflection of a tapered rod. We report in this paper a comprehensive numerical analysis and experimental test of the exact theory of bending deformation of a tapered rod. Given the rod geometry and elastic modulus, the theory yields virtually all the geometric and physical features that an analyst, experimenter, or instrument designer might want as a function of impressed load, such as the exact curve of deformation (termed the elastica), maximum tip displacement, maximum tip deflection angle, distribution of curvature, and distribution of bending moment. Applied experimentally, the theory permits rapid estimation of the elastic modulus of a rod, which is not easily obtainable by other means. We have tested the theory by photographing the shapes of a set of flexible rods of different lengths and tapers subject to a range of impressed loads and using digital image analysis to extract the coordinates of the elastica curves. The extent of flexure in these experiments far exceeded the range of applicability of approximations that linearize the equations of equilibrium or neglect tapering of the rod. Agreement between the measured deflection curves and the exact theoretical predictions was excellent in all but several cases. In these exceptional cases, the nature of the anomalies provided important information regarding the deviation of the rods from an ideal Euler-Bernoulli cantilever, which thereby permitted us to model the deformation of the rods more accurately.

The effect of MWCNT content on electropolymerization of PPy film and electromechanical behavior of PPy electrode-based soft actuators

This study investigates the effects of multi-walled carbon nanotubes (MWCNTs) content on the electropolymerization potential of polypyrrole (PPy) on both surfaces of carbon nanoparticle/MWCNT (CN/M)-coated Nafion membranes and on the electrical, electrochemical and electromechanical properties of PPy- electrode based soft actuators. SEM analysis revealed that the surface morphology of actuators changes considerably by altering the MWCNT content and the most porous PPy films formed in actuator comprising of 25wt% MWCNT. The electrochemical characteristics of the prepared actuators were compared in terms of double layer capacitance (Cdl), pseudo capacitance (CF) and ionic conductivity (σ). The capacitive nature of the prepared actuators was followed by waveform analysis of applied voltage and output current. Cdl and σ increased by increasing the MWCNT content up to 25wt% and afterward decreased considerably, while a reverse trend was observed for CF. The electrochemical impedance spectroscopy (EIS) measurements confirmed that this sample had the highest surface roughness. These data were in good agreement with the data obtained from water uptake (WUP) and ion exchange capacity (IEC) measurements. The electro-chemo-mechanical performances of the actuators were followed by studying the maximum tip displacement and IV curves. The largest tip displacement was obtained in actuators comprising of 25wt% MWCNT which showed to have the highest capacitive characteristic (243.52 mF. cm−2). The specific electro-mechanical energy efficiency (1.18) and the maximum tip displacement (25mm) of these metal-free actuators were 18% and 9% higher than that considered for Pt-based actuators, respectively. This strategy is therefore of considerable interest for increasing the applicability of low cost carbon-based soft actuators in medicine and robotics.