Mechanical & Fluid Systems

Compliant Gripper for a Robotic Manipulator

Diverse small objects can be manipulated without force-feedback control.

The figure depicts a prototype of a robotic-manipulator gripping device that includes two passive compliant fingers, suitable for picking up and manipulating objects that have irregular shapes and/or that are, themselves, compliant. The main advantage offered by this device over other robotic-manipulator gripping devices is simplicity: Because of the compliance of the fingers, force-feedback control of the fingers is not necessary for gripping objects of a variety of sizes, shapes, textures, and degrees of compliance. Examples of objects that can be manipulated include small stones, articles of clothing, and parts of plants.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Robotics, Parts, Biomechanics

Hybrid Aerial/Rover Vehicle

This robotic vehicle would combine features of balloons and "beach-ball" rovers.

A proposed instrumented robotic vehicle called an "aerover" would fly, roll along the ground, and/or float on bodies of liquid, as needed. The aerover would combine features of an aerobot (a robotic lighter-than-air balloon) and a wheeled robot of the "rover" class. An aerover would also look very much like a variant of the "beach-ball" rovers described in "Lightweight 'Beach- Ball' Robotic Vehicles" (NPO-20283), NASA Tech Briefs, Vol. 22, No. 7 (July 1998), page 74. Although the aerover was conceived for use in scientific exploration of Titan (the largest moon of the planet Saturn), the aerover concept could readily be adapted to similar uses on Earth.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Product development, Robotics, Autonomous vehicles, Marine vehicles and equipment, Spacecraft, Unmanned aerial vehicles

Docking Fixture and Mechanism for a Protective Suit

One can transfer safely and quickly between the suit and a sealed vehicle.

A suitlock assembly that comprises a docking fixture and mechanism has been invented to facilitate and accelerate donning and doffing of a sealed protective suit and/or to enable ingress and egress between the protective suit and a sealed vessel. The sealed protective suit could be a space suit, in which case the sealed vessel could be a spacecraft. Alternatively, the sealed suit could be an environmental protective suit of a type worn on Earth during cleanup of a hazardous-material site, in which case the sealed vessel could be a vehicle equipped to maintain a safe interior environment for workers in transit to and from the site. Figure 1 depicts a typical situation in which several crewmembers are working inside such a vehicle, one is working outside in a protective suit, and one is donning or doffing a protective suit while holding onto an overhead bar for support.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Product development, Hazards and emergency management, Hazards and emergency operations, Protective clothing, Spacesuits, Spacecraft

Solution-Adaptive Program for Computing 2D/Axi Viscous Flow

A computer program solves the Navier- Stokes equations governing the flow of a viscous, compressible fluid in an axisymmetric or two-dimensional (2D) setting. To obtain solutions more accurate than those generated by prior such programs that utilize regular and/or fixed computational meshes, this program utilizes unstructured (that is, irregular triangular) computational meshes that are automatically adapted to solutions. The adaptation can refine to regions of high change in gradient or can be driven by a novel residual minimization technique. Starting from an initial mesh and a corresponding data structure, the adaptation of the mesh is controlled by use of minimization functional. Other improvements over prior such programs include the following: (1) Boundary conditions are imposed weakly; that is, following initial specification of solution values at boundary nodes, these values are relaxed in time by means of the same formulations as those used for interior nodes. (2) Eigenvalues are limited in order to suppress expansion shocks. (3) An upwind fluctuation-splitting distribution scheme applied to inviscid flux requires fewer operations and produces less artificial dissipation than does a finite-volume scheme, leading to greater accuracy of solutions.
Posted in: Briefs, TSP, Mechanical Components, Mechanics, Computational fluid dynamics, Computer software and hardware, Performance upgrades, Product development

Mechanical Amplifier for a Piezoelectric Transducer

In addition to multiplication of stroke, the design affords momentum compensation.

A mechanical amplifier has been devised to multiply the stroke of a piezoelectric transducer (PZT) intended for use at liquid helium temperatures. Interferometry holds the key to high angular resolution imaging and astrometry in space. Future space missions that will detect planets around other solar systems and perform detailed studies of the evolution of stars and galaxies will use new interferometers that observe at mid- and far-infrared wavelengths. Phase-measurement interferometry is key to many aspects of astronomical interferometry, and PZTs are ideal modulators for most methods of phase measurement, but primarily at visible wavelengths. At far infrared wavelengths of 150 to 300 µm, background noise is a severe problem and all optics must be cooled to about 4 K. Under these conditions, piezos are ill-suited as modulators, because their throw is reduced by as much as a factor of 2, and even a wavelength or two of modulation is beyond their capability. The largest commercially available piezo stacks are about 5 in. (12.7 cm) long and have a throw of about 180 µm at room temperature and only 90 μm at 4 K. It would seem difficult or impossible to use PZTs for phase measurements in the far infrared were it not for the new mechanical amplifier that was designed and built.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Amplifiers, Imaging and visualization, Lasers

Swell Sleeves for Testing Explosive Devices

A device is detonated in a sleeve and the resultant swelling is measured.

A method of testing explosive and pyrotechnic devices involves exploding the devices inside swell sleeves. Swell sleeves have been used previously for measuring forces. In the present method, they are used to obtain quantitative indications of the energy released in explosions of the devices under test.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Test equipment and instrumentation

Propulsion Flight-Test Fixture

Subscale engines can be flight-tested early in the development cycle.

NASA Dryden Flight Research Center's new Propulsion Flight Test Fixture (PFTF), designed in house, is an airborne engine-testing facility that enables engineers to gather flight data on small experimental engines. Without the PFTF, it would be necessary to obtain such data from traditional wind tunnels, ground test stands, or laboratory test rigs.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Jet engines, Flight tests, Test facilities

High-Temperature Switched-Reluctance Electric Motor

Motors like this one would be incorporated into gas turbines as starter/generators.

An eight-pole radial magnetic bearing has been modified into a switched-reluctance electric motor capable of operating at a speed as high as 8,000 rpm at a temperature as high as 1,000 °F (Å540 °C). The motor (see figure) is an experimental prototype of starter-motor/ generator units that have been proposed to be incorporated into advanced gas turbine engines and that could operate without need for lubrication or active cooling.

Posted in: Briefs, Mechanical Components, Mechanics, Bearings, Electric motors

Using ERF Devices To Control Deployments of Space Structures

A report proposes devices containing electrorheological fluids (ERFs) damper for controlling deployments of lightweight, flexible structures in outer space. The structures would include spring members that could be wound or compressed for compact stowage during transport. The ERF based damper would keep the structures compacted and/or regulate the speeds with which the structures would spring out for deployment. After deployment, ERF based dampening mechanism could be used to rigidize the structures or damp their vibrations. The report describes several potential variations on the basic concept of an ERF-controlled structural member, including compartmentalization of the interior volume to prevent total loss of the ERF in case of a leak and the use of multiple, individually addressable electrode pairs to enable more localized control.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Dampers and shock absorbers, Smart materials

Miniature Gas-Turbine Power Generator

Energy density would greatly exceed that of a typical battery system.

A proposed microelectromechanical system (MEMS) containing a closed- Brayton-cycle turbine would serve as a prototype of electric- power generators for special applications in which high energy densities are required and in which, heretofore, batteries have been used. The system would have a volume of about 6 cm3 and would operate with a thermal efficiency >30 percent, generating up to 50 W of electrical power. The energy density of the proposed system would be about 10 times that of the best battery-based systems now available, and, as such, would be comparable to that of a fuel cell.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Microelectricmechanical device, Microelectromechanical devices, Microelectricmechanical device, Microelectromechanical devices, Electric power, On-board energy sources, Gas turbines

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