Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

The capability, speed, size, and widespread availability of small unmanned aerial systems (sUAS) makes them a serious security concern. The enabling technologies for sUAS are rapidly evolving and so too are the threats they pose to national security. Potential threat vehicles have a small cross-section, and are difficult to reliably detect using purely ground-based systems (e.g. radar or electro-optical) and challenging to target using conventional anti-aircraft defenses. Ground-based sensors are static and suffer from interference with the earth, vegetation and other man-made structures which obscure objects at low altitudes. Because of these challenges, sUAS pose a unique and rapidly evolving threat to national security.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

This paper describes how parallel elastic elements can be used to reduce energy consumption in the electric-motor-driven, fully actuated, Sandia Transmission-Efficient Prototype Promoting Research (STEPPR) bipedal walking robot without compromising or significantly limiting locomotive behaviors. A physically motivated approach is used to illustrate how selectively engaging springs for hip adduction and ankle flexion predict benefits for three different flat-ground walking gaits: human walking, human-like robot walking, and crouched robot walking. Based on locomotion data, springs are designed and substantial reductions in power consumption are demonstrated using a bench dynamometer. These lessons are then applied to STEPPR, a fully actuated bipedal robot designed to explore the impact of tailored joint mechanisms on walking efficiency. Featuring high-Torque brushless DC motors, efficient low-ratio transmissions, and high-fidelity torque control, STEPPR provides the ability to incorporate novel joint-level mechanisms without dramatically altering high-level control. Unique parallel elastic designs are incorporated into STEPPR, and walking data show that hip adduction and ankle flexion springs significantly reduce the required actuator energy at those joints for several gaits. These results suggest that parallel joint springs offer a promising means of supporting quasi-static joint torques due to body mass during walking, relieving motors of the need to support these torques and substantially improving locomotive energy efficiency.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

In this paper we introduce STEPPR (Sandia Transmission-Efficient Prototype Promoting Research), a bipedal robot designed to explore efficient bipedal walking. The initial iteration of this robot achieves efficient motions through powerful electromagnetic actuators and highly back-drivable synthetic rope transmissions. We show how the addition of parallel elastic elements at select joints is predicted to provide substantial energetic benefits: reducing cost of transport by 30 to 50 percent. Two joints in particular, hip roll and ankle pitch, reduce dissipated power over three very different gait types: human walking, human-like robot walking, and crouched robot walking. Joint springs based on this analysis are tested and validated experimentally. Finally, this paper concludes with the design of two unique parallel spring mechanisms to be added to the current STEPPR robot in order to provide improved locomotive efficiency.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

There are numerous applications for small-scale actuation utilizing pyrotechnics and explosives. In certain applications, especially when multiple actuation strokes are needed, or actuator reuse is required, it is desirable to have all gaseous combustion products with no condensed residue in the actuator cylinder. Toward this goal, we have performed experiments on utilizing milligram quantities of high explosives to drive a millimeterdiameter actuator with a stroke of 30 mm. Calculations were performed to select proper material quantities to provide 0.5 J of actuation energy. This was performed utilizing the thermochemical code Cheetah to calculate the impetus for numerous propellants and to select quantities based on estimated efficiencies of these propellants at small scales. Milligram quantities of propellants were loaded into a small-scale actuator and ignited with an ignition increment and hot wire ignition. Actuator combustion chamber pressure was monitored with a pressure transducer and actuator stroke was monitored using a laser displacement meter. Total actuation energy was determined by calculating the kinetic energy of reaction mass motion against gravity. Of the materials utilized, the best performance was obtained with a mixture of 2,4,6,8,10,12-hexanitro-2,4,6,8,10, 12- hexaazaisowurtzitane (CL-20) and bis-triaminoguanidinium(3,3' dinitroazotriazolate) (TAGDNAT). © 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.