Femtosecond laser fabricated nitinol living hinges for millimeter-sized robots

Nitinol is a smart material that can be used as an actuator, a sensor, or a structural element, and has the potential to significantly enhance the capabilities of microrobots. Femtosecond laser technology can be used to process nitinol while avoiding heat-affected zones (HAZ), thus retaining superelastic properties. In this work, we manufacture living hinges of arbitrary cross-sections from nitinol using a femtosecond laser micromachining process. We first determined the laser cutting parameters, 4.1 Jcm^-2 fluence with 5 passes for 5 um ablation, by varying laser power level and number of passes. Next, we modeled the hinges using an analytical model as well as creating an Abaqus finite element method, and showed the accuracy of the models by comparing them to the torque produced by eight different hinges, four with a rectangular cross-section and four with an arc cross-section. Finally, we manufactured three prototype miniature devices to illustrate the usefulness of these nitinol hinges: a sample spherical 5-bar mechanism, a sarrus linkage, and a piezoelectric actuated robotic wing mechanism.Comment: 6 pages, 6 figures, submitted to IEEE RA-

The Effects of Asymmetry on Oscillatory Propulsion

Owing to the problems caused by propellers, research has turned to the biological world for inspiration for non-propeller propulsion. Rays were chosen for further study and it was found that a key feature of their swimming is the asymmetric-in-time movements of their pectoral fins. The main goal was to determine whether asymmetric-in-time oscillations produced a larger resultant force. Two flexible fins were used (NACA and biomimetic stiffness profile "BIO"). Asymmetry was defined by the proportion of the time period taken to effect one half-stroke. The experiments showed that at low frequencies, asymmetric oscillation produced greater resultant force and that this force was at an angle to the chord of the fin at rest. At high frequencies, the BIO fin produced lower resultant force when oscillating asymmetrically and the angle of the resultant force was the same as for the symmetric oscillations. There was no difference between the resultant force magnitude or direction produced by the NACA fin at high frequencies. More power was used when oscillating asymmetrically but the force efficiency, the resultant force per watt, was often the same for symmetric and asymmetric oscillations. The trailing edge kinematics of the fins were analysed. Some of the kinematics variables correlated with the resultant force magnitude independently of fin type. The wake structures behind the fins oscillating at two different frequencies were examined. The wakes were geometrically asymmetric behind both fins oscillating asymmetrically at low frequency. At the higher frequency, the wakes behind the asymmetrically oscillating fins were no different to their symmetric counterpartsEThOS - Electronic Theses Online ServiceGBUnited Kingdo

Computational Fluid Dynamics Simulations of Oscillating Wings and Comparison to Lifting-Line Theory

Computational fluid dynamics (CFD) analysis was performed in order to compare the solutions of oscillating wings with Prandtl’s lifting-line theory. Quasi-steady and steady-periodic simulations were completed using the CFD software Star-CCM+. The simulations were performed for a number of frequencies in a pure plunging setup. Additional simulations were then completed using a setup of combined pitching and plunging at multiple frequencies. Results from the CFD simulations were compared to the quasi-steady lifting-line solution in the form of the axial-force, normal-force, power, and thrust coefficients, as well as the efficiency obtained for each simulation. The mean values were evaluated for each simulation and compared to the quasi-steady lifting-line solution. It was found that as the frequency of oscillation increased, the quasi-steady lifting-line solution was decreasingly accurate in predicting solutions

Aeronautical engineering: A continuing bibliography with indexes (supplement 296)

This bibliography lists 592 reports, articles, and other documents introduced into the NASA scientific and technical information system in Oct. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 119)

This bibliography lists 341 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1980. Abstracts on the engineering and theoretical aspects of design, construction, evaluation, testing, operation, and performance of aircraft (including aircraft engines) and associated components, equipment, and systems are presented. Research and development in aerodynamics, aeronautics, and ground support equipment for aeronautical vehicles are also presented

Aeronautical engineering: A continuing bibliography with indexes (supplement 301)

This bibliography lists 1291 reports, articles, and other documents introduced into the NASA scientific and technical information system in Feb. 1994. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 233)

This bibliography lists 637 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1988. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics