A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Control and Stabilization of Soft Inverted Pendulum on a Cart(2023) Ajithkumar, Ananth; Chopra, Nikhil Dr.; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Underactuated systems are systems that cannot be controlled to track any arbitrary trajectories in their configuration space. In this work, we introduce a novel soft-robotic pendulum on a cart system. This is an underactuated soft-robotic system with two degrees of under-actuation. We model the system, derive the kinematics, and motivated by the control strategies for classical underactuated systems, we study the swing-up control and stabilization of this system around the vertical equilibrium point. The switching-based control law uses an energy-based control for swing-up and LQR for stabilization once the system is within the region of attraction of LQR. The simulation results depict the efficaciousness of the developed control scheme. Further, in this thesis, we discuss the viability and feasibility of feedback linearization, partially feedback-linearize the system, and analyze the zero dynamics of the system.Item Modeling and Characterization of Bioinspired Hybrid Flapping/Gliding Flight for Flapping Wing Air Vehicles(2022) Johnson, Lena; Bruck, Hugh; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Unmanned Aerial Vehicles (UAVs) are increasingly being used for applications that require longer, reliable flight duration and distances. The greatest limitation to achieving these desired flights is the current on board battery technology which, restricted by internal chemistry and external size, can only provide a finite amount of power over time. Efforts to increase the battery’s efficiency and energy storage tend to rely on cumbersome methods that add weight and/or complexity to the system. However natural flyers, though also limited by a finite amount of internal energy gained through food consumption, are able to extend their flights through techniques that either utilize their inherent aerodynamic advantages or advantageously employ atmospheric phenomena. Flapping-Wing UAVs (FWUAVs) are as limited by their onboard battery as any other type of UAV, but because of their bio-inspired functionality are uniquely suited to utilize natural flight extension methods. Therefore, this PhD presents an analysis of the exploration of bio-inspired, hybrid flapping/gliding, also known as intermittent gliding, techniques to improve the flight performance of a FWUAV. Robo Raven is the FWUAV that was chosen as the research platform for this work. It was developed by researchers at the University of Maryland to perform prolonged, untethered flights and exhibit a flight proficiency that combined the maneuverability of rotary-wing flight with the efficiency of fixed-wing flight. The technique to improve FWUAV flight time, presented in this work incorporates (1) the modeling of Robo Raven’s flapping/gliding potential through the development of a state-space representation directly linking Robo Raven’s onboard battery dynamics with its aerodynamic performance, (2) the use of the state-space model to characterize the effect of intermittent gliding techniques on flight performance through simulation, (3) the real-world characterization of the simulation and of intermittent gliding techniques through flight demonstrations, and (4) the development of a design space by which the effect of wing design on gliding performance might be explored and lead to the potential tailoring of wing design to desired flight performance. The expected outcome of this technique is scientific analysis of the extension of Robo Raven’s flight time without added complexity of weight of the battery system.Item SOFT ROBOTIC APPENDAGES USING PNEUMATIC ARTIFICIAL MUSCLES(2018) Pillsbury, Thomas; Wereley, Norman M; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation focuses on advancing the state of the art in soft robotics using pneumatic artificial (PAM) actuators. Pneumatic artificial muscles are currently used in robotic and prosthetic applications due to their high power to weight ratio, controllable compliance, and simple design. Contractile PAMs are typically used in traditional hard robotics in place of heavy electric motors. As the field of soft robotics grows, extensile PAMs are beginning to have increased usage. The bladder of a PAM affects common actuator performance metrics, specifically: blocked force, free contraction, hysteresis, and dead-band pressure. This work investigates the effect that bladder thickness has on static actuation performance of small scale PAMs. Miniature PAMs were fabricated with a range of bladder thicknesses then experimentally characterized in quasi-static conditions, where results showed that increasing bladder wall thickness decreases blocked force and free contraction, while the dead-band pressure increases. A nonlinear model was then applied to determine the structure of the stress-strain relationship that enables accurate modeling and the minimum number of terms. Contractile and extensile PAMs were experimentally fabricated and parametrically compared to demonstrate the advantages and disadvantages of each type of PAM and applications for which they are best suited. An additional PAM model was developed based on finite strain theory to address the lack of predicitive models. The closed-form pneumatic artificial muscle quasi-static actuator force is obtained. The analysis was experimentally validated using actuation force versus contraction ratio test data at a series of discrete inflation pressures for four different pneumatic artificial muscles, two contractile and two extensile. This work investigates adding bio-inspired ossicle structures from brittle stars to pneumatic artificial muscle continuum arm sections. The ossicle structure increases the range of motion and load capability of the continuum arm section while reducing the pneumatic pressure requirements. In this work, a static model of the continuum arm section is developed assuming constant curvature in the section and finding the center of mass of the section and its end plate. This model is validated by comparing the pressure-angle relationship at various loading conditions.