Norman Wereley
University of Maryland, Aerospace Engineering, Faculty Member
- Dr. Wereley is the Minta Martin Professor and Chair of the Dept. of Aerospace Engineering at the University of Maryla... moreDr. Wereley is the Minta Martin Professor and Chair of the Dept. of Aerospace Engineering at the University of Maryland since 2012. He joined the Alfred Gessow Rotorcraft Center in 1993. He currently serves as the Director of the Smart Structures Laboratory and the Composites Research Laboratory. His research interests are in dynamics and control of smart structures, with emphasis on active and passive vibration damping control applied to rotorcraft, robotics, aircraft, and other aerospace and automotive systems. His first key research area is the theory and application of semi-active magnetorheological (MR) dampers, and their application to occupant protection, vibration isolation, and stability augmentation systems using advanced feedback control strategies. A second key research area is the design and development of actuators using smart and multifunctional material actuation schemes (PZT, PMN, GaFeNOL, TerFeNOL), pneumatics (such as pneumatic artificial muscles, hydraulics, and passive and active compliant mechanisms, as well as structures for shape changing or morphing wings for aircraft or morphing rotor blades in helicopters. Dr. Wereley’s research has been funded under a U.S. Army Research Office Young Investigator Award and a National Science Foundation CAREER Award, as well as grants from DARPA, the Army Research Laboratory, Air Force Office of Scientific Research, NASA, and Office of Naval Research. His research has also been heavily supported by over 15 corporations including: Techno-Sciences, General Motors, Boeing, Bell Helicopter, Lord Corporation, and Materials Modification Inc. He has advised 43 M.S. (2 pending), 23 Ph.D. graduates (2 pending), and numerous undergraduate research projects. Dr. Wereley has published (or at press) over 210 journal articles, 17 book chapters, and over 280 conference articles. Dr. Wereley is a co-inventor on 19 patents and several patents pending. Many of these patents are currently being commercialized as magnetorheological seat suspensions for SH-60 Seahawk (flight test pending for US Navy), Rigid Inflatable Boats (RIB) for SOCOM (sea trials completed for US Navy), as well as UH-60 Blackhawk crash protection seating, and MRAP ground vehicle mine blast protection seating, which are both in the development stage. Dr. Wereley serves on the editorial board of the Journal of Intelligent Material Systems and Structures since 1996, and currently serves as Editor (2007–present). He is currently an associate editor for Smart Materials and Structures, AHS Journal, MDPI Aerospace, and MDPI Actuators. Dr. Wereley has served for many years on the international program committees of international conferences, and has assumed several leadership roles, including General Chair (2011) of the AIAA Adaptive Structures Conference; Co-Chair (2010, 2011) and Chair (2012, 2013), of the SPIE Symposium on Smart Materials and Structures. He has given invited lectures at numerous conferences and international universities in the field of magnetorheological fluids, devices and applications. Dr. Wereley has been twice awarded the ASME Adaptive Structures and Adaptive Materials Best Paper Award in Structural Dynamics and Control (2004, 2012). Dr. Wereley was named the AIAA National Capital Section Engineer of the Year (2009), and is a member of the AIAA Engineer of the Year Society (2010). He was awarded UMD’s Faculty Service Award (2010), and the AIAA Sustained Service Award (2011). He was awarded the AHS Harry T. Jenson Award (May 2011) for active crash protection systems (team award with Boeing, US Army, Honeywell and University of Maryland). Dr. Wereley was awarded the 2012 ASME Adaptive Structures and Material Systems Prize, the 2013 SPIE Smart Structures and Materials Lifetime Achievement Award, and the 2013 SPIE Smart Structures and Materials Product Implementation Award. Dr. Wereley is a Fellow of AHS (2015), AIAA (2012), ASME (2008), IOP (2001), and SPIE (2014). He is also a senior member of IEEE, and a member of ASEE, and SAMPE. Dr. Wereley holds a B.Eng. in Mechanical Engineering from McGill University in Montreal, Canada, and M.S. and Ph.D. in Aeronautics and Astronautics from the Massachusetts Institute of Technology in 1987 and 1990, respectively.(Dr. Wereley is the Minta Martin Professor and Chair of the Dept. of Aerospace Engineering at the University of Maryland since 2012. He joined the Alfred Gessow Rotorcraft Center in 1993. He currently serves as the Director of the Smart Structures Laboratory and the Composites Research Laboratory. His research interests are in dynamics and control of smart structures, with emphasis on active and passive vibration damping control applied to rotorcraft, robotics, aircraft, and other aerospace and automotive systems. His first key research area is the theory and application of semi-active magnetorheological (MR) dampers, and their application to occupant protection, vibration isolation, and stability augmentation systems using advanced feedback control strategies. A second key research area is the design and development of actuators using smart and multifunctional material actuation schemes (PZT, PMN, GaFeNOL, TerFeNOL), pneumatics (such as pneumatic artificial muscles, hydraulics, and passive and active compliant mechanisms, as well as structures for shape changing or morphing wings for aircraft or morphing rotor blades in helicopters. Dr. Wereley’s research has been funded under a U.S. Army Research Office Young Investigator Award and a National Science Foundation CAREER Award, as well as grants from DARPA, the Army Research Laboratory, Air Force Office of Scientific Research, NASA, and Office of Naval Research. His research has also been heavily supported by over 15 corporations including: Techno-Sciences, General Motors, Boeing, Bell Helicopter, Lord Corporation, and Materials Modification Inc. He has advised 43 M.S. (2 pending), 23 Ph.D. graduates (2 pending), and numerous undergraduate research projects. Dr. Wereley has published (or at press) over 210 journal articles, 17 book chapters, and over 280 conference articles. Dr. Wereley is a co-inventor on 19 patents and several patents pending. Many of these patents are currently being commercialized as magnetorheological seat suspensions for SH-60 Seahawk (flight test pending for US Navy), Rigid Inflatable Boats (RIB) for SOCOM (sea trials completed for US Navy), as well as UH-60 Blackhawk crash protection seating, and MRAP ground vehicle mine blast protection seating, which are both in the development stage. Dr. Wereley serves on the editorial board of the Journal of Intelligent Material Systems and Structures since 1996, and currently serves as Editor (2007–present). He is currently an associate editor for Smart Materials and Structures, AHS Journal, MDPI Aerospace, and MDPI Actuators. Dr. Wereley has served for many years on the international program committees of international conferences, and has assumed several leadership roles, including General Chair (2011) of the AIAA Adaptive Structures Conference; Co-Chair (2010, 2011) and Chair (2012, 2013), of the SPIE Symposium on Smart Materials and Structures. He has given invited lectures at numerous conferences and international universities in the field of magnetorheological fluids, devices and applications. Dr. Wereley has been twice awarded the ASME Adaptive Structures and Adaptive Materials Best Paper Award in Structural Dynamics and Control (2004, 2012). Dr. Wereley was named the AIAA National Capital Section Engineer of the Year (2009), and is a member of the AIAA Engineer of the Year Society (2010). He was awarded UMD’s Faculty Service Award (2010), and the AIAA Sustained Service Award (2011). He was awarded the AHS Harry T. Jenson Award (May 2011) for active crash protection systems (team award with Boeing, US Army, Honeywell and University of Maryland). Dr. Wereley was awarded the 2012 ASME Adaptive Structures and Material Systems Prize, the 2013 SPIE Smart Structures and Materials Lifetime Achievement Award, and the 2013 SPIE Smart Structures and Materials Product Implementation Award. Dr. Wereley is a Fellow of AHS (2015), AIAA (2012), ASME (2008), IOP (2001), and SPIE (2014). He is also a senior member of IEEE, and a member of ASEE, and SAMPE. Dr. Wereley holds a B.Eng. in Mechanical Engineering from McGill University in Montreal, Canada, and M.S. and Ph.D. in Aeronautics and Astronautics from the Massachusetts Institute of Technology in 1987 and 1990, respectively.)edit
The design and test of a magnetorheological fluid (MRF)-based universal gripper (MR gripper) are presented in this study. The MR gripper was developed to have a simple design, but with the ability to produce reliable gripping and handling... more
The design and test of a magnetorheological fluid (MRF)-based universal gripper (MR gripper) are presented in this study. The MR gripper was developed to have a simple design, but with the ability to produce reliable gripping and handling of a wide range of simple objects. The MR gripper design consists of a bladder mounted atop an electromagnet, where the bladder is filled with an MRF, which was formulated to have long-term stable sedimentation stability, that was synthesized using a high viscosity linear polysiloxane (HVLP) carrier fluid with a carbonyl iron particle (CIP) volume fraction of 35%. Two bladders were fabricated: a magnetizable bladder using a magnetorheological elastomer (MRE), and a passive (non-magnetizable) silicone rubber bladder. The holding force and applied (initial compression) force of the MR gripper for a bladder fill volume of 75% were experimentally measured, for both magnetizable and passive bladders, using a servohydraulic material testing machine for a...
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In this study, a simple but effective design of an adaptively tunable magnetorheological elastomer (MRE)-based seat vibration absorber (SVA) is presented to achieve better vibration reduction of a propeller aircraft seat. In order to... more
In this study, a simple but effective design of an adaptively tunable magnetorheological elastomer (MRE)-based seat vibration absorber (SVA) is presented to achieve better vibration reduction of a propeller aircraft seat. In order to effectively concentrate the magnetic field generated from the electromagnet into the MRE pad areas, an electromagnetic finite element analysis (FEA) was also conducted. Based on this FEA, the MRE-based SVA was fabricated. The damping force characteristics of the MRE-based SVA were experimentally evaluated using an Instron testing machine. The dynamic stiffness and loss factor of the MRE-based SVA were obtained using this test data. In order to confirm the tunability of the MRE-based SVA, the transmissibility with respect to a range of applied input currents was experimentally obtained via vibration testing.
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An active trailing edge flap system, actuated utilizing Pneumatic Artificial Muscles (PAMs), is developed in this study. PAMs were chosen as the actuation method because of several attractive properties, including: high specific work and... more
An active trailing edge flap system, actuated utilizing Pneumatic Artificial Muscles (PAMs), is developed in this study. PAMs were chosen as the actuation method because of several attractive properties, including: high specific work and power output, an expendable operating fluid (air), and robustness. Because of their performance, PAM are a potential enabling technology for a variety of next-generation aerospace systems. The actuation system developed here is sized for a full-scale active rotor system for a Bell 407 scale helicopter. This system is designed to produce large Trailing Edge Flap (TEF) deflections (±20°) at the main rotor rotation frequency (1 rev−1) to create large amplitude thrust variations that enable primary control of the helicopter. Additionally, the TEF actuation system is designed to produce smaller magnitude deflections at higher frequencies, up to 5 rev−1 ( N + 1 rev−1), to provide vibration mitigation capabilities. The PAMs are mounted antagonistically in ...
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ABSTRACT Nanofiber-based magnetorheological (MR) fluids display an increased achievable yield stress and greatly reduced sedimentation as compared to conventional MR fluids which typically consist of micron-sized spherical ferromagnetic... more
ABSTRACT Nanofiber-based magnetorheological (MR) fluids display an increased achievable yield stress and greatly reduced sedimentation as compared to conventional MR fluids which typically consist of micron-sized spherical ferromagnetic particles suspended in a carrier fluid. The maximum achievable yield stress of nanofiber-based MR fluids can be more than double that of MR fluids that contain strictly spherical particles at the same particle loadings. Conventional MR fluids display appreciable settling whereas the nanofiber-based fluids display no discernible settling at volume fractions greater than ~6 vol. %. However, a maximum volume fraction of <10 vol. % is achievable in suspensions containing only nanofibers. To achieve the higher loadings required for most commercial applications, dimorphic MR fluids were created in which spherical particles are partially substituted with nanofibers. Dimorphic MR fluid display significantly enhanced particle sedimentation properties with yield stresses equivalent to or greater than those of conventional MR fluids. Nanofibers are well suited as model particles for the systematic experimental and theoretical study of the shape- and composition-dependent properties of MR fluids owing to their well defined geometry, controllable dimensions and composition. The use of nanofibers has greatly enhanced MR fluid properties and has resulted in a better understanding of their physical behavior.
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In this study a novel, biologically inspired, trailing edge flap system was designed and tested under full-scale aerodynamic loading in the Glenn L. Martin Wind Tunnel at the University of Maryland. The system consisted of two pairs of... more
In this study a novel, biologically inspired, trailing edge flap system was designed and tested under full-scale aerodynamic loading in the Glenn L. Martin Wind Tunnel at the University of Maryland. The system consisted of two pairs of pneumatic artificial “muscles” driving a flap through wire rope “tendons.” This concept is envisioned to be a next generation high performance actuation system applicable to a wide range of control surfaces from UAV flaps to rotorcraft blades. In order to explore the feasibility and design of this concept, a representative wing section with a partial-span trailing edge flap was constructed. A 15% chord flap 10-in long was installed into a 24-in span wing with a 21-in chord NACA 0012 airfoil. Two pairs of antagonistically arranged 1-in outer diameter, 5.25-in length pneumatic artificial muscles were mounted chordwise inside the wing section. A novel tendon spooling design was used to convert the actuation forces into torques about the flap spar. A simple empirical model was developed which successfully predicts low frequency performance. System performance was experimentally determined over a wide range of operating pressures (15 – 90 psi), actuation frequencies (0.1 – 40 Hz), angles of attack (0 – 12°), and free stream velocities (M = 0 – 0.3). This actuation concept was successfully able to generate large flap deflections (almost ± 40°) and show that biologically inspired pneumatic actuation systems are a promising technology for future aerospace control applications.
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Page 1. Abstract This paper presents the dynamic modeling of Mckibben pneumatic artificial muscles. The air flow model of a valve orifice and the air volume model of a pneumatic muscle are incorporated into the proposed ...
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This study addresses the application of MR (magnetorheological) isolators to vibration isolation of precision payloads for aerial vehicles. To this end, a precision payload in an aerial vehicle is modeled as a six-degree-of-freedom (DOF)... more
This study addresses the application of MR (magnetorheological) isolators to vibration isolation of precision payloads for aerial vehicles. To this end, a precision payload in an aerial vehicle is modeled as a six-degree-of-freedom (DOF) lumped parameter model of a sensor assembly. An MR isolator is modeled as a 3-DOF passive spring-damping element and a 3-DOF semi-active yield force due to the yield stress of an MR fluid. Three MR isolators are configured with equal installation angles between the precision payload and the base structure in the aerial vehicle. The governing equations of motion for the MR vibration isolation system of the precision payload for the aerial vehicle are derived and then key parameters of the MR isolators, such as stiffness, damping, and isolator orientation, are determined via a global optimization method. The simulated response of the passive MR vibration isolation system with no magnetic field control input and constant magnetic field control input ar...
In this study a novel aircraft trailing edge flap system was developed and tested. Pneumatic Artificial Muscles (PAMs) were used as the driving elements of this system to demonstrate their feasibility as an alternative aerospace actuation... more
In this study a novel aircraft trailing edge flap system was developed and tested. Pneumatic Artificial Muscles (PAMs) were used as the driving elements of this system to demonstrate their feasibility as an alternative aerospace actuation technology. A prototype flap/actuator system was integrated into a model wing section and tested on the bench-top under simulated airloads (M = 0.32) and in an open-jet wind tunnel at free stream velocities ranging up to 100 mph (M=0.13). Testing was performed for actuator pressures ranging from 10 to 90 psi and actuation frequencies ranging from 0.1 to 31 Hz. Results show that the PAM driven trailing edge flap system can generate significant, sustainable deflections. Key parameters are also identified for increasing system performance and providing a foundation for future research.
ABSTRACT This research investigates the feasibility of using Pneumatic Artificial Muscles (PAMs) to drive a rotor blade Trailing Edge Flap (TEF) for primary control and/or vibration reduction. Specifically, this work investigates the... more
ABSTRACT This research investigates the feasibility of using Pneumatic Artificial Muscles (PAMs) to drive a rotor blade Trailing Edge Flap (TEF) for primary control and/or vibration reduction. Specifically, this work investigates the effects of operating these compliant, pneumatic actuators under the high CF loading typical of a helicopter rotor blade. A prototype TEF actuation system was designed and built. It was tested in a vacuum whirl chamber over a range of centrifugal accelerations. Bi-directional actuation was performed to track changes in system performance with increasing CF field. Additionally, testing was performed under different levels of torsional spring loading to simulate aerodynamic hinge moment effects. Results of these tests motivated a second experiment wherein the effects of CF loading on the PAMs themselves are isolated from the rest of the system. This was accomplished by fixing the ends of PAM and performing blocked force testing over a range of centrifugal accelerations. Taken together, these tests show that chordwise PAM actuators are capable of operating under high CF loading with only minor losses in performance. Additionally, the need for careful design of actuation and flap system components for operation in this harsh environment is reiterated.
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ABSTRACT Lag dampers are a critically important stability augmentation device in modern soft in-plane rotors that are used to mitigate mechanical instabilities such as ground resonance, as well as aeromechanical instabilities such as air... more
ABSTRACT Lag dampers are a critically important stability augmentation device in modern soft in-plane rotors that are used to mitigate mechanical instabilities such as ground resonance, as well as aeromechanical instabilities such as air resonance. The in-plane bending, or lead-lag, modes of helicopter rotor blades have very low aerodynamic damping levels, so that damping in these modes must be augmented using a mechanical damper. Typical dampers utilize flow of hydraulic fluids through an orifice, and/or direct shearing of elastomeric material, to achieve these augmented damping levels. In this chapter, an existing lag damper of the snubber type that employs both hydraulic flow through an orifice as well as direct shearing of elastomeric material is modified to provide controllable damping using magnetorheological fluids. The existing orifices in the snubber damper are modified in such a way that magnetic field can be applied to the magnetorheological fluids flowing through the orifice, in order to effect a change in apparent viscosity and, thus, a change in damping level.
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ABSTRACT Magnetorheological energy absorbers (MREAs) provide adaptive vibration and shock mitigation capabilities to accommodate varying payloads, vibration spectra, and shock pulses, as well as other environmental factors. A key... more
ABSTRACT Magnetorheological energy absorbers (MREAs) provide adaptive vibration and shock mitigation capabilities to accommodate varying payloads, vibration spectra, and shock pulses, as well as other environmental factors. A key performance metric is the dynamic range, which is defined as the ratio of the force at maximum field to the force in the absence of field. The off-state force is typically assumed to increase linearly with speed, but at the higher shaft speeds occurring in impact events, the off-state damping exhibits nonlinear velocity squared damping effects. To improve understanding of MREA behavior under high-speed impact conditions, this study focuses on nonlinear MREA models that can more accurately predict MREA dynamic behavior for nominal impact speeds of up to 6 m s-1. Three models were examined in this study. First, a nonlinear Bingham-plastic (BP) model incorporating Darcy friction and fluid inertia (Unsteady-BP) was formulated where the force is proportional to the velocity. Second, a Bingham-plastic model incorporating minor loss factors and fluid inertia (Unsteady-BPM) to better account for high-speed behavior was formulated. Third, a hydromechanical (HM) analysis was developed to account for fluid compressibility and inertia as well as minor loss factors. These models were validated using drop test data obtained using the drop tower facility at GM R&D Center for nominal drop speeds of up to 6 m s-1.
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Recent developments in morphing aircraft research have motivated investigation into conformal morphing systems, that is, shape change without discrete moving parts or abrupt changes in the airfoil profile. In this study, implementation of... more
Recent developments in morphing aircraft research have motivated investigation into conformal morphing systems, that is, shape change without discrete moving parts or abrupt changes in the airfoil profile. In this study, implementation of a continuous span morphing wing is described. The system consists of two primary components: (1) zero-Poisson ratio morphing core and (2) fiber-reinforced elastomeric matrix composite skin with a nearly zero-Poisson ratio in-plane. The main goal for improved air vehicle efficiency was a nominal 100% change in area of the active wing section with less than 2.54 mm out-of-plane deflection under representative aerodynamic loading. Objectives of this study included exploring fabrication techniques for advanced morphing core shapes (i.e., having airfoil-shaped cross-section), exploiting customizable design parameters of in-house fabricated skin and core material, designing a prototype wing structure such that integration with a candidate UAV was feasibl...
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Recent advancements in actuator technology suggest that the implementation of reliable, high power-to-weight ratio pneumatic actuation systems is now possible for robotic platforms. Existing robotic manipulator arms for casualty... more
Recent advancements in actuator technology suggest that the implementation of reliable, high power-to-weight ratio pneumatic actuation systems is now possible for robotic platforms. Existing robotic manipulator arms for casualty extraction and patient placement use hydraulic actuation, whereas related robotic prosthetic devices typically use heavy actuator motors. We have developed an alternative solution that employs pneumatic artificial muscles (PAMs). The goal of this study is to identify requirements for a lightweight, high-force robotic manipulator, design the system for heavy lifting capability, and assemble a prototype arm. Following characterization and comparison of different-sized PAM actuators, a proof-of-concept manipulator was constructed. A quasi-static model for the PAM actuators was applied to the system, which includes the Gaylord force, as well as non-linear elastic energy storage. Experimental testing was performed to measure the joint torque and dynamic response ...
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Broad-scale area change of a non-porous surface while maintaining resistance to aerodynamic loading was demonstrated through the development of a passive elastomeric matrix composite morphing skin. The combined system includes an... more
Broad-scale area change of a non-porous surface while maintaining resistance to aerodynamic loading was demonstrated through the development of a passive elastomeric matrix composite morphing skin. The combined system includes an elastomer-fiber-composite surface layer that is supported by a flexible honeycomb structure, each of which exhibit a near-zero in-plane Poisson’s ratio. A number of elastomers, composite arrangements, and substructure configurations were evaluated and characterization testing led to the selection of the most appropriate components for prototype development. The complete prototype morphing skin demonstrated 100% uniaxial extension accompanied by a 100% increase in surface area. Results from out-of-plane pressure loading showed that out-of-plane deflection of less than 0.1 in. (2.5 mm) can be maintained at various levels of area change under pressures of up to 200 psf (9.58 kPa). Applications to wing span morphing UAVs are also discussed.
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Pneumatic artificial muscles are a class of pneumatically driven actuators that are remarkable for their simplicity, lightweight, and excellent performance. These actuators are essentially a tubular bladder surrounded by a braided sleeve... more
Pneumatic artificial muscles are a class of pneumatically driven actuators that are remarkable for their simplicity, lightweight, and excellent performance. These actuators are essentially a tubular bladder surrounded by a braided sleeve and sealed at both ends. Pressurization of the actuators generates contraction and tensile forces. Pneumatic artificial muscles have traditionally been used for robotics applications, but there has been recent interest in adapting them to a variety of aerospace actuation applications where their large stroke and force, which are realized at minimal weight penalty, create potential performance improvements over traditional technologies. However, an impediment to wide-spread acceptance of pneumatic artificial muscles is the relatively short fatigue lives of the actuators reported in the literature (typically, less than 18,000 actuation cycles before damage occurs). The purpose of this study is to develop a new construction method designed to greatly i...
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Micro-air vehicle (MAV) development is moving toward smaller and more capable platforms to enable missions such as indoor reconnaissance. This miniaturization creates challenging constraints on volume and energy generation/storage for all... more
Micro-air vehicle (MAV) development is moving toward smaller and more capable platforms to enable missions such as indoor reconnaissance. This miniaturization creates challenging constraints on volume and energy generation/storage for all systems onboard. Actuator technologies must also address these miniaturization goals. Much research has focused on active material systems, such as piezoelectric materials and synthetic jets, but these advanced technologies have specific, but limited, capability. Conventional servo technology has also encountered concerns over miniaturization. Motivation has thus been established to develop a small-scale actuation technology prototype based on pneumatic artificial muscles, which are known for their lightweight, high-output, and low-pressure operation. The miniature actuator provides bidirectional control capabilities for a range of angles, rates, and loading conditions. Problems addressed include the scaling of the pneumatic actuators and design of...
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ABSTRACT An active trailing-edge flap system for helicopter rotor blades using pneumatic artificial muscles was investigated, with the goal of generating flap deflections suitable for both vibration mitigation and primary flight control.... more
ABSTRACT An active trailing-edge flap system for helicopter rotor blades using pneumatic artificial muscles was investigated, with the goal of generating flap deflections suitable for both vibration mitigation and primary flight control. Prior work with these actuators showed that large deflections were possible under full-scale conditions. This study developed and demonstrated an inner loop feedback controller that enables the flap to track the complex waveforms required to achieve its goal. Control algorithm development began with proportional feedback, but required the addition of a dead time compensator to reduce tracking error and increase bandwidth. The dead time compensator initially had a fixed value, though this transitioned to a variable to cope with potential changes in the dead time due to changing operating conditions. In this case, the system can continuously adjust the dead time estimate from the position error and predict future tracking error using that estimate, and adjust the control action accordingly. This approach requires no system model and no a priori information about the desired command signal. As such, it is well suited to the active rotor problem. Testing of this controller on single sine waves and complex waveforms composed of a sum of the first four odd harmonics of the rotor frequency showed good tracking for all conditions.
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Pneumatic artificial muscles (PAMs) are comprised of an elastomeric bladder surrounded by a braided mesh sleeve. When the bladder is inflated, the actuator may either contract or extend axially, with the direction of motion dependent on... more
Pneumatic artificial muscles (PAMs) are comprised of an elastomeric bladder surrounded by a braided mesh sleeve. When the bladder is inflated, the actuator may either contract or extend axially, with the direction of motion dependent on the orientation of the fibers in the braided sleeve. Contractile PAMs have excellent actuation characteristics, including high specific power, specific work, and power density. Unfortunately, extensile PAMs exhibit much reduced blocked force, and are prone to buckling under axial compressive loading. For applications in which extensile motion and compressive force are desired, the push-PAM actuator introduced here exploits the operational characteristics of a contractile PAM, but changes the direction of motion and force by employing a simple internal mechanism using no gears or pulleys. Quasi-static behavior of the push-PAM was compared to a contractile PAM for a range of operating pressures. Based on these data, the push-PAM actuator can achieve fo...
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Research Interests: Engineering, Materials Science, Magnetic Materials, Stress, Nanoparticles, and 15 moreStability, Permeability, Magnetic particles, Magnetic Levitation, Physical sciences, Magnetic Properties, Magnetorheological Fluids, Microparticles, Sedimentation, Velocity, Saturation Magnetization, Magnetic Fields, Non Newtonian Fluids, Inductance, and Magnetic Flux
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Semi‐Active Damping of Ground Resonance in Helicopters Using Magnetorheological Dampers. [Journal of the American Helicopter Society 49, 468 (2004)]. Yongsheng Zhao, Graduate Research Assistant, Young‐Tai Choi, Research Associate, Norman... more
Semi‐Active Damping of Ground Resonance in Helicopters Using Magnetorheological Dampers. [Journal of the American Helicopter Society 49, 468 (2004)]. Yongsheng Zhao, Graduate Research Assistant, Young‐Tai Choi, Research Associate, Norman M. Wereley, Professor. ...
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Morphing mechanisms, inspired by biological fliers, offer a lucrative option for controlling aircraft geometry for mitigating adverse aeroelastic phenomena, and potentially using the aircraft flexibility of the aircraft to our advantage.... more
Morphing mechanisms, inspired by biological fliers, offer a lucrative option for controlling aircraft geometry for mitigating adverse aeroelastic phenomena, and potentially using the aircraft flexibility of the aircraft to our advantage. But, in order to enable morphing aircraft, there is a need to determine suitable morphing mechanisms; develop materials and actuation techniques for practical application; and develop a design optimization framework for detailed structural design (with aeroelastic considerations) for a select vehicle concept. We have been developing AMuBA (Aeroservoelastic Multifidelity Design of Biomimetic Aircraft) – a tool for efficient Multidisciplinary Design Optimization (MDO) of aeroelastic aircraft. AMuBA enables aeroservoelastic analysis with Finite Element Analysis (FEA)-based structural sizing within the conceptual design environment. In order to facilitate the coupling between medium-fidelity aerodynamics and high-fidelity structures, a parametric geomet...
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The U.S. Naval Research Laboratory (NRL) has been developing a space-rated 7 degree of freedom (DOF) robot arm with a high payload-to-mass ratio as an alternative design to motor-gear driven robotic manipulators. The robot arm employs... more
The U.S. Naval Research Laboratory (NRL) has been developing a space-rated 7 degree of freedom (DOF) robot arm with a high payload-to-mass ratio as an alternative design to motor-gear driven robotic manipulators. The robot arm employs antagonistic pairs of pneumatic artificial muscle (PAM) actuators to control each degree-of-freedom (DOF) to achieve large force outputs relative to the PAM component masses. A novel feature of the NRL PAM actuator was the integration of the pneumatic control components inside the pressure-bladder, which not only reduces the volume of the robotic arm hardware but also reduces the pressurized-gas actuation volume in the PAM enabling significant reductions in gas consumption during actuation. This multifunctional design enables reductions in launch-weight costs and increases in operational endurance for space applications. The integration of these PAMs into a well-designed robotic-arm structure, in tandem with a newly developed control algorithm, has the...
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To attract and encourage first-year undergraduates to undertake their studies in aerospace engineering, a single credit course was developed, entitled ENAE-100 The Aerospace Engineering Profession. A key element of this course is the... more
To attract and encourage first-year undergraduates to undertake their studies in aerospace engineering, a single credit course was developed, entitled ENAE-100 The Aerospace Engineering Profession. A key element of this course is the illustration of the engineering process of design, test and evaluation as applied to aerospace engineering applications. A classroom demonstration was developed using a 1/6th model-scale helicopter lag mode damper that has similar properties to a model-scale damper used in the industrial helicopter model. The energy analysis for this classroom experiment is well within the skill level of the first year undergraduate.
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L'invention porte sur un procede de conception d'un amortisseur absorbant l'energie de fluide magnetorheologique (MR), lequel procede utilise une analyse hydromecanique avec des parametres localises pour permettre une... more
L'invention porte sur un procede de conception d'un amortisseur absorbant l'energie de fluide magnetorheologique (MR), lequel procede utilise une analyse hydromecanique avec des parametres localises pour permettre une determination quant au fait de savoir si une conception d'amortisseur potentielle fournira les caracteristiques predeterminees, telles qu'une plage de forces dynamiques desiree et une vitesse de piston maximale desiree, avec un fluide MR selectionne et une limite d'elasticite desiree, et satisfait, de preference, des limitations geometriques predeterminees.
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Linear stroke magnetorheological energy absorbers (MREAs) can be used to adaptively control load-stroke profiles under impact loads. An appropriate and controllable dynamic range, defined as the ratio of the force at maximum field to the... more
Linear stroke magnetorheological energy absorbers (MREAs) can be used to adaptively control load-stroke profiles under impact loads. An appropriate and controllable dynamic range, defined as the ratio of the force at maximum field to the off-state force, as well as the off-state (minimum) damping force, must be specified in order to account for varying payload mass over a wide range of MREA operating velocities. A key challenge when designing MREAs for high speed impact conditions is that the high shaft speeds in linear stroke MREAs induce high Reynolds number flows in the magnetic valve of the MREA, so that high dynamic range canbe a design challenge. Previous studies demonstrated that the dynamic range, D, of an MREA under high speed drop impact test dramatically dropped to D≈1 as velocity rose to 6.6 m/s, where Reynolds number, Re>2000. Also, past research on MREAs typically assumed that the off-state force increases linearly with speed, but at the higher shaft speeds occurrin...
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ABSTRACT A single-degree-of-freedom (SDOF) semi-active vibration control system based on a magnetorheological (MR) damper with an inner bypass is investigated in this paper. The MR damper employing a pair of concentric tubes, between... more
ABSTRACT A single-degree-of-freedom (SDOF) semi-active vibration control system based on a magnetorheological (MR) damper with an inner bypass is investigated in this paper. The MR damper employing a pair of concentric tubes, between which the key structure, i.e., the inner bypass, is formed and MR fluids are energized, is designed to provide large dynamic range (i.e., ratio of field-on damping force to field-off damping force) and damping force range. The damping force performance of the MR damper is modeled using phenomenological model and verified by the experimental tests. In order to assess its feasibility and capability in vibration control systems, the mathematical model of a SDOF semi-active vibration control system based on the MR damper and skyhook control strategy is established. Using an MTS 244 hydraulic vibration exciter system and a dSPACE DS1103 real-time simulation system, experimental study for the SDOF semi-active vibration control system is also conducted. Simulation results are compared to experimental measurements.
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ABSTRACT
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This study addresses the effects of compliance of an occupant seated in an adaptive seat suspension equipped with a magnetorheological energy absorber, and exposed to intense vertical shocks. A 50th percentile male occupant, exposed to... more
This study addresses the effects of compliance of an occupant seated in an adaptive seat suspension equipped with a magnetorheological energy absorber, and exposed to intense vertical shocks. A 50th percentile male occupant, exposed to shock conditions characterized by sink rates varying from 5 to 10 m/s, was considered. The compliance effects were examined by comparing the response of a multiple degree-of-freedom biodynamic lumped-parameter model derived from the response of a Hybrid II anthropomorphic test dummy representing a compliant-occupant model to the response of an equivalent rigid-occupant model under the same shock conditions. An experimentally validated nonlinear mathematical model of a magnetorheological energy absorber was integrated with both the compliant and rigid models of the occupants. In addition, three different control techniques were investigated based on controlling the onset of magnetorheological-energy-absorber stroking load: constant stroking-load control, terminal trajectory...
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A key requirement for the commercialization of various magnetorheological fluid (MRF)-based applications is sedimentation stability. In this study, a high viscosity linear polysiloxane (HVLP), which has been used for shock absorbers in... more
A key requirement for the commercialization of various magnetorheological fluid (MRF)-based applications is sedimentation stability. In this study, a high viscosity linear polysiloxane (HVLP), which has been used for shock absorbers in heavy equipment, is proposed as a new carrier fluid in highly stable MRFs. The HVLP is known to be a thixotropic (i.e., shear thinning) fluid that shows very high viscosity at very low shear rate and low viscosity at higher shear rate. In this study, using the shear rheometer, the significant thixotropic behavior of the HVLP was experimentally confirmed. In addition, a HVLP carrier fluid-based MRF (HVLP MRF) with 26 vol. % was synthesized and its sedimentation characteristics were experimentally investigated. But, because of the opacity of the HVLP MRF, no mudline can be visually observed. Hence, a vertical axis inductance monitoring system (VAIMS) applied to a circular column of fluid was used to evaluate sedimentation behavior by correlating measured inductance with the v...
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Advanced rotor systems including hingeless and bearingless rotors have air and ground resonance instabilities due to coalescence of low-frequency rotor modes with landing gear and fuselage modes, respectively. This coalescence is of... more
Advanced rotor systems including hingeless and bearingless rotors have air and ground resonance instabilities due to coalescence of low-frequency rotor modes with landing gear and fuselage modes, respectively. This coalescence is of difficulty due to the direct connection of the rotor blade in these advanced rotor systems to the rotor hub using a flexure or flexbeam. We are currently exploring the mitigation of this modal coalescence through the use of active damping techniques and electro-rheological fluid technology.
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As a smart material, magnetorheological fluid (MRF) has been utilized in fields including civil engineering and automotive engineering, and so on. In this study, the MR damping turning tool based on the squeeze-mode was developed to... more
As a smart material, magnetorheological fluid (MRF) has been utilized in fields including civil engineering and automotive engineering, and so on. In this study, the MR damping turning tool based on the squeeze-mode was developed to improve the vibration resistance of the tool system on the lathe. The 3D magnetic circuit simulations of the damper were performed. The influences of damper structural parameters, such as coil positions, plate thicknesses, and others, on the magnetic induction strength were investigated. Orthogonal experiments were carried out and the optimal combination of damper parameters was determined. The chatter suppressive experiments were carried out to evaluate the performance of the MR damping turning tool.