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Beltsville, MD, United States

Robinson R.M.,University of Maryland University College | Kothera C.S.,InnoVital Systems, Inc. | Wereley N.M.,University of Maryland University College
IEEE/ASME Transactions on Mechatronics

This paper investigates the orderly recruitment of pneumatic artificial muscles for efficient torque production in a robotic manipulator. Pneumatic artificial muscles (PAMs) are arranged in a parallel bundle, and independently-controlled 'motor units' are employed to imitate the structure and function of human skeletal muscle. Simulated cycling tests are conducted on a model of the robotic manipulator to quantify the benefits of variable recruitment, and experimental testing is performed to validate the simulated predictions. Results reveal a distinct relationship between recruitment and system efficiency. Key factors influencing the value of a variable recruitment strategy include nonlinear PAM bladder elasticity, pneumatic losses, and dissipative forces in the robotic joint. Recruitment guidelines are proposed to maximize efficiency over a range of payload masses. The potential challenges associated with maintaining smooth motion control during discrete transitions in recruitment are also identified and discussed. © 1996-2012 IEEE. Source

Woods B.K.S.,University of Swansea | Kothera C.S.,InnoVital Systems, Inc. | Wang G.,University of Alabama in Huntsville | Wereley N.M.,University of Maryland University College
Smart Materials and Structures

This study presents a time domain dynamic model of an antagonistic pneumatic artificial muscle (PAM) driven trailing edge flap (TEF) system for next generation active helicopter rotors. Active rotor concepts are currently being widely researched in the rotorcraft community as a means to provide a significant leap forward in performance through primary aircraft control, vibration mitigation and noise reduction. Recent work has shown PAMs to be a promising candidate for active rotor actuation due to their combination of high force, large stroke, light weight, and suitable bandwidth. When arranged into biologically inspired agonist/antagonist muscle pairs they can produce bidirectional torques for effectively driving a TEF. However, there are no analytical dynamic models in the literature that can accurately capture the behavior of such systems across the broad range of frequencies required for this demanding application. This work combines mechanical, pneumatic, and aerodynamic component models into a global flap system model developed for the Bell 407 rotor system. This model can accurately predict pressure, force, and flap angle response to pneumatic control valve inputs over a range of operating frequencies from 7 to 35 Hz (1/rev to 5/rev for the Bell 407) and operating pressures from 30 to 90 psi. © 2014 IOP Publishing Ltd. Source

Iii R.D.V.,College Park | Kothera C.S.,InnoVital Systems, Inc. | Wereley N.M.,College Park
Smart Materials and Structures

Pneumatic artificial muscles (PAMs), or McKibben actuators, have received considerable attention for robotic manipulators and in aerospace applications due to their similarity to natural muscles. Like natural muscles, PAMs are a purely contractile actuator, so that, in order to produce bi-directional or rotational motion, they must be arranged in an agonist/antagonist pair, which inherently limits the deflection of the system due to the high parasitic stiffness of the antagonistic PAM. This study presents two methods for increasing the performance of an antagonistic PAM system by decreasing the passive parasitic torque, rather than increasing the active torque. The first involves selection of the kinematic mechanism geometry, and the second involves the introduction of bias into the system, both in terms of PAM contraction and passive (antagonistic) PAM pressure. It was found with the proper selection of design parameters, including mechanism geometry, PAM geometry, and bias conditions, that an ideal actuator configuration can be chosen that maximizes deflection for a given arbitrary loading. When comparing a baseline design to an improved design for a simplified case, a nearly 50% increase in maximum deflection was predicted simply by optimizing mechanism geometry and bias contraction. These results were experimentally verified with quasi-static testing that showed a 300% increase in actuator deflection over the baseline design. © 2014 IOP Publishing Ltd. Source

Robinson R.M.,University of Maryland University College | Kothera C.S.,InnoVital Systems, Inc. | Wereley N.M.,University of Maryland University College
Journal of Intelligent Material Systems and Structures

Pneumatic artificial muscles are actuators known for their low weight, high specific force, and natural compliance. Employed in antagonistic schemes, these actuators closely mimic biological muscle pairs, resulting in applications for humanoid and other bio-inspired robotic systems. Such systems require precise actuator modeling and control in order to achieve high performance. In the present study, refinements are introduced to an existing model of pneumatic artificial muscle force-contraction behavior. The force-balance modeling approach is modified to include the effects of non-constant bladder thickness and up to a fourth-order polynomial stress-strain relationship is adopted in order to accurately capture nonlinear pneumatic artificial muscle force behavior in contraction and extension. Moreover, the polynomial coefficients of the stress-strain relationship are constrained to vary linearly with pressure, improving the ability to predict behavior at untested pressure levels while preserving model accuracy at tested pressure levels. Lastly, a detailed geometric model is applied to improve force predictions, particularly during pneumatic artificial muscle extension. By modeling the deformation shape of the actuator ends as sections of an elliptic toroid, pneumatic artificial muscle force predictions as a function of strain are improved. These modeling improvements combine to enable enhanced model-based control in pneumatic artificial muscle actuator applications. © The Author(s) 2014. Source

Agency: Department of Defense | Branch: Defense Health Program | Program: SBIR | Phase: Phase I | Award Amount: 149.99K | Year: 2014

Many emergency cricothyrotomy kits have been developed in an attempt to simplify this potentially life-saving medical procedure. However, none of the existing kits perform noticeably better than the standard surgical kit. The standard kit itself has led to a reported failure rate of 33% when performed in combat environments, and airway obstruction is reported to be the third most preventable cause of death on the battlefield. The high failure rate is at least partially attributable to inadequate training and experience. As such, InnoVital Systems, Inc. proposes to develop an innovative universal device that is light weight, packable, and adjustable to different size soldiers or patients that will significantly increase ease of use and efficacy of performing cricothyrotomies. Building upon our experience in medical device design, evaluation, and clearance, we will perform design, analysis, fabrication, and FDA clearance planning in Phase I of the project, which will end with prototype bench tests. Phase II will focus on further design refinements and functional hardware validation of the final design with selected materials, and executing the steps necessary for FDA device clearance.

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