Aerospace Engineering Research Works

Permanent URI for this collectionhttp://hdl.handle.net/1903/1655

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Characterization of Magnetorheological Impact Foams in Compression
(MDPI, 2024-06-14) Choi, Young; Wereley, Norman M.; Wereley, Norman M.
This study focuses on the development and compressive characteristics of magnetorheo- logical elastomeric foam (MREF) as an adaptive cushioning material designed to protect payloads from a broader spectrum of impact loads. The MREF exhibits softness and flexibility under light compressive loads and low strains, yet it becomes rigid in response to higher impact loads and ele- vated strains. The synthesis of MREF involved suspending micron-sized carbonyl Fe particles in an uncured silicone elastomeric foam. A catalyzed addition crosslinking reaction, facilitated by platinum compounds, was employed to create the rapidly setting silicone foam at room temperature, simplify- ing the synthesis process. Isotropic MREF samples with varying Fe particle volume fractions (0%, 2.5%, 5%, 7.5%, and 10%) were prepared to assess the effect of particle concentrations. Quasi-static and dynamic compressive stress tests on the MREF samples placed between two multipole flexible strip magnets were conducted using an Instron servo-hydraulic test machine. The tests provided measurements of magnetic field-sensitive compressive properties, including compression stress, energy absorption capability, complex modulus, and equivalent viscous damping. Furthermore, the experimental investigation also explored the influence of magnet placement directions (0◦ and 90◦) on the compressive properties of the MREFs.
Adaptive magnetorheological fluid energy absorption systems: a review
(Institute of Physics, 2024-03-01) Bai, Xianxu 'Frank'; Zhang, Xinchi; Choi, Young; Shou, Mengje; Zhu, Guanghong; Wereey, Norman M.; Wereley, Norman
In the last two decades, magnetorheological (MR) fluids have attracted extensive attention since they can rapidly and continuously control their rheological characteristics by adjusting an external magnetic field. Because of this feature, MR fluids have been applied to various engineering systems. This paper specifically investigates the application of MR fluids in shock mitigation control systems from the aspects of three key technical components: the basic structural design of MR fluid-based energy absorbers (MREAs), the analytical and dynamical model of MREAs, and the control method of adaptive MR shock mitigation control systems. The current status of MR technology in shock mitigation control is presented and analyzed. Firstly, the fundamental mechanical analysis of MREAs is carried out, followed by the introduction of typical MREA configurations. Based on mechanical analysis of MREAs, the structural optimization of MREAs used in shock mitigation control is discussed. The optimization methods are given from perspectives of the design of piston structures, the layout of electromagnetic coil, and the MR fluid gap. Secondly, the methods of damper modeling for MREAs are presented with and without consideration of the inertia effect. Then both the modeling methods and their characteristics are introduced for representative parametric dynamic models, semi-empirical dynamic models, and non-parametric dynamic models. Finally, the control objectives and requirements of the shock mitigation control systems are analyzed, and the current competitive methods for the ideal ‘soft-landing’ control objectives are reviewed. The typical control methods of MR shock mitigation control systems are discussed, and based on this the evaluation indicators of the control performance are summarized.
Tailorable Energy Absorbing Cellular Materials via Sintering of Dry Powder Printed Hollow Glass Microspheres
(2024-05-01) Wereley, Norman; Park, Jungjin; Howard, John; DeMay, Matthew; Edery, Avi; Wereley, Norman
This article examines amorphous glass-based foams as lightweight core materials for crash-resistant structures that offer tailorable energy absorption capabilities. Hollow glass microspheres (HGMs) of different densities are layered using dry powder printing (DPP), an additive manufacturing process, and subsequently sintered to consolidate these microspheres into a cellular foam structure. The tailoring of energy absorption is achieved in these foams by layering hollow microspheres with different densities and different thickness ratios of the layers. The mechanical response to quasi-static uniaxial compression of the bilayer foams is also investigated. Bilayer samples exhibit a distinctive two-step stress-strain profile that includes first and second plateau stress, as opposed to a single constant density which does not. The strain at which the second plateau occurs can be tailored by adjusting the thickness ratio of the two layers. The resulting stress-strain profiles demonstrate tailorable energy absorption. Tailorability is found to be more significant if the density values of each layer differ greatly. For comparison, bilayer samples are fabricated using epoxy at the interface instead of the co- sintering process. Epoxy-bonded samples show a different mechanical response from the co-sintered sample with a different stress-strain profile. Designing the bilayer foams enables tailoring of the stress-strain profile, so that energy-absorption requirements can be met for a specific impact condition. The implementation of these materials for energy absorption, crashworthiness, and buoyancy applications will be discussed.
A novel approach to inverse design of wind turbine airfoils using tandem neural networks
(Wiley, 2024-05-30) Anand, Apurva; Marepally, Koushik; Safdar, M Muneeb; Baeder, James D.
The performance of a wind turbine and its efficiency majorly depends on wind-to-rotor efficiency. The aerodynamic design of the wind turbine blades using high-fidelity tools such as adjoint-computational fluid dynamics (CFD) is accurate but computationally expensive. It becomes impractical when the number of design variables increases for multidisciplinary optimization (MDO). Low-fidelity tools are computationally cheaper but are not accurate, especially in regions of adverse pressure gradient and reverse flows. Surrogate modeling has been used in many aerodynamic problems. We develop and apply a recent architecture of the deep learning module, tandem neural networks (T-NNs) for the inverse design of wind turbine airfoils. The T-NNs trained on CFD data for fully turbulent cases predict not only the performance parameters for the given airfoil geometry but also the airfoil geometry for a given design objective. This framework uses the entire performance polar for inverse design which ensures that the airfoil optimization is not a single-point optimization problem which is essential for practical design problems. The T-NNs are also optimized to include multiple constraints like maximum thickness and trailing edge (TE) thickness which is a novel contribution in the field of inverse design using surrogate models. A statistical analysis is also performed to predict a family of airfoil geometries.
System identification for high-performance UAV control in wind
(Wiley, 2023-08-14) Shastry, Animesh K.; Paley, Derek A.
This article describes and experimentally evaluates a comprehensive system identification framework for high-performance UAV control in wind. The framework incorporates both linear offline and nonlinear online methods to estimate model parameters in support of a nonlinear model-based control implementation. Inertial parameters of the UAV are estimated using a frequency-domain linear system identification program by incorporating control data obtained from motor-speed sensing along with state estimates from an automated frequency sweep maneuver. The drag-force coefficients and external wind are estimated recursively in flight with a square-root unscented Kalman filter. A custom flight controller is developed to handle the computational demand of the online estimation and control. Flight experiments illustrate the nonlinear controller's tracking performance and enhanced gust rejection capability.
Terrapin Rocket Team's Technical Report to the 2023 Spaceport America Cup
(2023) Daniel, Hailu; Bean, Andrew; Bregin, Ezra; Gill, Dasam; Roy, Nathan; M Jaffar, Mohamed Khalid; Alessandrini, Garret; Mallamaci, Michael; Goldberg, Adin; Zheng, Howard; Rizvi, Saim
This document presents the University of Maryland’s 10,000 ft SRAD Motor Category rocket, Karkinos. It is the third time that the team will be attending the Cup in person since 2018, and the current team has built on the lessons learned at the 2022 Cup. The design process for Karkinos is centered around manufacturability and reliability coupled with a rigorous testing process. This report also documents the design of our Air Brake system that actively trims the rocket’s altitude during flight. The CubeSat payload for this rocket will test the release of a vehicle from the rocket during drogue descent.
Simulation of packet dropouts over wireless channels considering Rayleigh fading effects
(2020) M Jaffar, Mohamed Khalid; Otte, Michael
This document describes how we implement a Rayleigh fading model for use in a multi-robot communication simulation. The main objective of this work is to characterize communication losses in multi-agent settings that require high levels of collaboration.
Feedback motion replanning during high-stakes scenario
(2019) M Jaffar, Mohamed Khalid; Otte, Michael
This paper proposes a novel algorithm for a quadrotor to replan its motion in the event of one, two or three rotor loss. Further, during the course of its replanned trajectory, the MAV avoids collision with static obstacles including the ground.
Terrapin Rocket Team's Technical Report to the 2022 Spaceport America Cup
(2022) Bregin, Ezra; Bean, Andrew; Daniel, Hailu; Roy, Nathan; M Jaffar, Mohamed Khalid; Alessandrini, Garret; Mallamaci, Michael; Goldberg, Adin; Zheng, Howard; Gill, Dasam
This document presents University of Maryland’s 10,000 ft COTS Motor Category rocket, Terpulence II. This project is a return to high power rocketry fundamentals within the Terrapin Rocket Team. It is the first time that the team will be attending the Cup in person since 2018 and the first time any current team members will compete at Spaceport. The design process is targeted at building off of other successful projects and manufacturing a safe and reliable competition rocket. This reports also documents the design of a novel air brake system that increases the rocket performance to reach a desired apogee. The CubeSat payload for this rocket will test liquid fuel tank geometry to gauge if capillary action can replace ullage motors in micro-gravity environments.
Magnetic Susceptibility Instrument for Magnetically Inhomogeneous Granular Mixtures
(Review of Scientific Instruments, 2024) Charles T. Pett
We introduce an instrument and novel method for characterizing the bulk magnetic susceptibility of granular mixtures by submerging an inductor coil in a bed of metallic beads and gauging changes in self-inductance. The resonance frequency of the coil was measured to determine its inductance and evaluate the magnetic permeability of ferrous mixtures relative to air. In air, our coil was accurate to within 3% of the permeability of free space. The range of magnetic susceptibility values for magnetically inhomogeneous granular mixtures is poorly constrained, but our coil uniquely quantifies bulk effects that other surface meters are not designed to resolve. Compared to both a commercial Terraplus Inc. KT-10 meter and theoretical approximations, we report similar trends in susceptibility values measured as a function of mass of ferromagnetic material per volume.
Control of a Heavy-Lift Robotic Manipulator with Pneumatic Artificial Muscles
(MDPI, 2014-04-24) Robinson, Ryan M.; Kothera, Curt S.; Wereley, Norman M.
Lightweight, compliant actuators are particularly desirable in robotic systems intended for interaction with humans. Pneumatic artificial muscles (PAMs) exhibit these characteristics and are capable of higher specific work than comparably-sized hydraulic actuators and electric motors. The objective of this work is to develop a control algorithm that can smoothly and accurately track the desired motions of a manipulator actuated by pneumatic artificial muscles. The manipulator is intended for lifting humans in nursing assistance or casualty extraction scenarios; hence, the control strategy must be capable of responding to large variations in payload over a large range of motion. The present work first investigates the feasibility of two output feedback controllers (proportional-integral-derivative and fuzzy logic), but due to the limitations of pure output feedback control, a model-based feedforward controller is developed and combined with output feedback to achieve improved closed-loop performance. The model upon which the controller is based incorporates the internal airflow dynamics, the physical parameters of the pneumatic muscles and the manipulator dynamics. Simulations were performed in order to validate the control algorithms, guide controller design and predict optimal gains. Using real-time interface software and hardware, the controllers were implemented and experimentally tested on the manipulator, demonstrating the improved capability.
Massively Parallel Large Eddy Simulation of Rotating Turbomachinery for Variable Speed Gas Turbine Engine Operation †
(MDPI, 2020-02-06) Jain, Nishan; Bravo, Luis; Kim, Dokyun; Murugan, Muthuvel; Ghoshal, Anindya; Ham, Frank; Flatau, Alison
Gas turbine engines are required to operate at both design and off-design conditions that can lead to strongly unsteady flow-fields and aerodynamic losses severely impacting performance. Addressing this problem requires effective use of computational fluid dynamics tools and emerging models that resolve the large scale fields in detail while accurately modeling the under-resolved scale dynamics. The objective of the current study is to conduct massively parallel large eddy simulations (LES) of rotating turbomachinery that handle the near-wall dynamics using accurate wall models at relevant operating conditions. The finite volume compressible CharLES solver was employed to conduct the simulations over moving grids generated through Voronoi-based unstructured cells. A grid sensitivity analysis was carried out first to establish reliable parameters and assess the quality of the results. LES simulations were then conducted to understand the impact of blade tip clearance and operating conditions on the stage performance. Variations in tip clearance of 3% and 16% chord were considered in the analysis. Other design points included operation at 100% rotor speed and off-design conditions at 75% and 50% of the rotor speed. The simulation results showed that the adiabatic efficiency improves dramatically with reduction in tip gap due to the decrease in tip leakage flow and the resulting flow structures. The analysis also showed that the internal flow becomes highly unsteady, undergoing massive separation, as the rotor speed deviates from the design point. This study demonstrates the capability of the framework to simulate highly turbulent unsteady flows in a rotating turbomachinery environment. The results provide much needed insight and massive data to investigate novel design concepts for the US Army Future Vertical Lift program.
Characterization and Analysis of Extensile Fluidic Artificial Muscles
(MDPI, 2021-01-30) Garbulinski, Jacek; Balasankula, Sai C.; Wereley, Norman M.
Extensile fluidic artificial muscles (EFAMs) are soft actuators known for their large ranges of extension, low weight, and blocked forces comparable to those of pneumatic cylinders. EFAMs have yet to be studied in a way that thoroughly focuses on their manufacturing, experimental characterization, and modeling. A fabrication method was developed for production of two EFAMs. The quasi-static axial force response of EFAMs to varying displacement was measured by testing two specimens under isobaric conditions over a pressure range of 103.4–517.1 kPa (15–75 psi) with 103.4 kPa (15 psi) increments. The muscles were characterized by a blocked force of 280 N and a maximum stroke of 98% at 517.1 kPa (75 psi). A force-balance model was used to analyze EFAM response. Prior work employing the force-balance approach used hyper-elastic constitutive models based on polynomial expressions. In this study, these models are validated for EFAMs, and new constitutive models are proposed that better represent the measured stress values of rubber as a function of strain. These constitutive models are compared in terms of accuracy when estimating pressure-dependent stress–strain relationships of the bladder material. The analysis demonstrates that the new hyper-elastic stress models have an error 5% smaller than models previously employed for EFAMs for the same number of coefficients. Finally, the analysis suggests that the new stress functions have smaller errors than the polynomial stress model with the same number of coefficients, guarantee material stability, and are more conservative about the stress values for strains outside of the testing range.
Photogrammetric Measurement and Analysis of the Shape Profile of Pneumatic Artificial Muscles
(MDPI, 2021-04-06) Chambers, Jonathan M.; Wereley, Norman M.
Inaccuracies in modeling of the geometric shape of PAMs has long been cited as a probable source of error in modeling and design efforts. The geometric shape and volume of PAMs is commonly approximated using a cylindrical shape profile, even though its shape is non-cylindrical. Correction factors—based on qualitative observations of the PAM’s general shape—are often implemented to compensate for error in this cylindrical shape approximation. However, there is little evidence or consensus on the accuracy and form of these correction factors. Approximations of the shape profile are also used to calculate the internal volume of PAMs, as experimental measurements of the internal volume require intrusive testing methods and specialized equipment. This research presents a photogrammetric method for measuring the shape profile and internal volume of PAMs. A test setup, method of image data acquisition, and a preliminary analysis of the image data, is presented in this research. A 22.2 mm (7/8 in) diameter PAM is used to demonstrate the photogrammetric procedure and test its accuracy. Analysis of the tested PAM characterizes trends of the shape profile with respect to pressure and contraction. The common method of estimating the diameter—through the use of the cylindrical approximation and initial geometry of the PAM—is tested by comparison to the measured shape profile data. Finally, a simple method of calculating the internal volume using the measured shape profile data is developed. The presented method of acquiring photogrammetric measurements of PAM shape produces an accurate characterization of its shape profile, thereby mitigating uncertainty in PAM shape in analysis and other efforts.
Formulation of Shell Elements Based on the Motion Formalism
(MDPI, 2021-12-10) Bauchau, Olivier; Sonneville, Valentin
This paper presents a finite element implementation of plates and shells for the analysis of flexible multibody systems. The developments are set within the framework of the motion formalism that (1) uses configuration and motion to describe the kinematics of flexible multibody systems, (2) couples their displacement and rotation components by recognizing that configuration and motion are members of the Special Euclidean group, and (3) resolves all tensors components in local frames. The formulation based on the motion formalism (1) provides a theoretical framework that streamlines the formulation of shell elements, (2) leads to governing equations of motion that are objective, intrinsic, and present a reduced order of nonlinearity, (3) improves the efficiency of the solution process, (4) circumvents the shear locking phenomenon that plagues shell formulations based on classical kinematic descriptions, and (5) prevents the occurrence of singularities in the treatment of finite rotation. Numerical examples are presented to illustrate the advantageous features of the proposed formulation.
Vibration Isolation Performance of an Adaptive Magnetorheological Elastomer-Based Dynamic Vibration Absorber
(MDPI, 2022-06-12) Choi, Young; Wereley, Norman M.
This study evaluates the vibration isolation performance of an adaptive magnetorheological elastomer (MRE)-based dynamic vibration absorber (MRE-DVA) for mitigating the high frequency vibrations (100–250 Hz) of target devices. A simple and effective MRE-DVA design was presented and its vibration isolation performance was experimentally measured. A cylindrical shaped MRE pad was configured to be operated in shear mode and also worked as a semi-actively tunable spring for achieving adaptive DVA. A complex stiffness analysis for the damper force cycle was conducted and it was experimentally observed that the controllable dynamic stiffness range of the MRE-DVA was greater than two over the tested frequency range. The transmissibility of a target system was measured and used as a performance index to evaluate its vibration isolation performance. It was also experimentally demonstrated that a better vibration isolation performance of the target device exposed to the high frequency vibrations could be achieved by using the adaptive MRE-DVA.
Analysis of Pneumatic Artificial Muscles and the Inelastic Braid Assumption
(MDPI, 2022-08-04) Chambers, Jonathan M.; Wereley, Norman M.
Pneumatic artificial muscles (PAMs) are becoming an increasingly popular form of soft actuator due to their unique actuation characteristics. The creation of accurate PAM actuation models is important for their successful implementation. However, PAM studies often employ actuation models that use simplifying assumptions which make the models easier to formulate and use, but at the cost of reduced accuracy. One of the most commonly used assumptions, the inelastic braid assumption, suggests that the braid does not stretch, and therefore would not affect its geometry or actuation force. Although this assumption has often been cited as a likely source of model error, its use has persevered for decades due to researchers’ inability to directly measure the effects of braid elasticity. The recent development of a photogrammetric method to accurately measure PAM geometry now enables this analysis. This study seeks to assess the current default adoption of the inelastic braid assumption in PAM models by attempting to quantify the braid elasticity effects. This research finds that current models that use the inelastic braid assumption can underestimate PAM diameter by as much as 30%, and overestimate actuation force by as much as 70%. These results show that braid elasticity can have a substantial effect on the geometry and actuation force of PAMs, and demonstrates that the inelastic braid assumption may not be a suitable universal assumption for PAM modeling and analyses, especially when low-stiffness braid materials are used.
Tunable Energy Absorbing Property of Bilayer Amorphous Glass Foam via Dry Powder Printing
(MDPI, 2022-12-19) Park, Jungjin; Howard, John; Edery, Avi; DeMay, Matthew; Wereley, Norman
The research in this paper entails the design of material systems with tunable energy-absorbing properties. Hollow glass microspheres of different densities are layered using dry powder printing and subsequently sintered to form a cellular structure. The tunability of the bilayer foams is investigated using various combinations of hollow microspheres with different densities and different thickness ratios of the layers. The mechanical responses to quasi-static uniaxial compression of the bilayer foams are also investigated. These bilayer samples show different mechanical responses from uniform samples with a distinctive two-step stress–strain profile that includes a first and second plateau stress. The strain where the second plateau starts can be tuned by adjusting the thickness ratio of the two layers. The resulting tunable stress–strain profile demonstrates tunable energy absorption. The tunability is found to be more significant if the density values of each layer differ largely. For comparison, bilayer samples are fabricated using epoxy at the interface instead of a sintering process and a different mechanical response is shown from a sintered sample with the different stress–strain profile. Designing the layered foams allows tuning of the stress–strain profile, enabling desired energy-absorbing properties which are critical in diverse impact conditions.
A lionfish-inspired predation strategy in planar structured environments
(Institute of Physics, 2023-06-30) Thompson, Anthony A.; Peterson, Ashley N.; McHenry, Matthew J.; Paley, Derek A.
This paper investigates a pursuit-evasion game with a single pursuer and evader in a bounded environment, inspired by observations of predation attempts by lionfish (Pterois sp.). The pursuer tracks the evader with a pure pursuit strategy while using an additional bioinspired tactic to trap the evader, i.e. minimize the evader’s escape routes. Specifically, the pursuer employs symmetric appendages inspired by the large pectoral fins of lionfish, but this expansion increases its drag and therefore its work to capture the evader. The evader employs a bioinspired randomly-directed escape strategy to avoid capture and collisions with the boundary. Here we investigate the trade-off between minimizing the work to capture the evader and minimizing the evader’s escape routes. By using the pursuer’s expected work to capture as a cost function, we determine when the pursuer should expand its appendages as a function of the relative distance to the evader and the evader’s proximity to the boundary. Visualizing the pursuer’s expected work to capture everywhere in the bounded domain, yields additional insights about optimal pursuit trajectories and illustrates the role of the boundary in predator-prey interactions.
Biorthogonal decomposition of the disturbance flow field generated by particle impingement on a hypersonic boundary layer
(Cambridge University Press, 2023-08-10) A. Al Hasnine, S.; Russo, V.; Tumin, A.; Brehm, C.
The disturbance flow field in a hypersonic boundary layer excited by particle impingement was investigated with a focus on the first stage of the laminar-to-turbulent transition process, namely the receptivity process. A previously validated direct numerical simulation approach adopting disturbance flow tracking is used to simulate the particle-induced transition process. Particle impingement generates a highly complex disturbance flow field that can be characterised by a wide range of frequencies and wavenumbers. After providing some insight about the spectral characteristics of the disturbance flow field in the frequency and wavenumber domains, biorthogonal decomposition is employed to reveal the composition of the disturbance flow field consisting of different continuous and discrete eigenmodes that are triggered through particle impingement. The disturbance flow characteristics for different frequency and wavenumber pairs are discussed where large contributions in the disturbance flow spectrum are observed in the vicinity of the impingement location. A significant amount of the disturbance energy is diverted into the free stream leading to large coefficients of projection for the slow and fast acoustic branches while contributions to the entropy and vorticity branches are negligible. In addition to the continuous acoustic spectra, the first-, second- and other higher-order Mack modes are activated and provide large contributions to the disturbance flow field inside the boundary layer. Finally, it is demonstrated that the disturbance flow field in the vicinity of the impingement location can be reconstructed with a maximum relative error of 2.3 % by employing a theoretical biorthogonal eigenfunction system expansion and by considering contributions from fast and slow acoustic waves and at most four discrete modes only.

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