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At least 649 records · Page 36

All sources NASA NTRS DOE OSTI

NASA NTRS1991

Experimental study of trajectory planning and control of a high precision robot manipulator

The kinematic and trajectory planning is presented for a 6 DOF end-effector whose design was based on the Stewart Platform mechanism. The end-effector was used as a testbed for studying robotic assembly of NASA hardware with passive compliance. Vector analysis was employed to derive a closed-form solution for the end-effector inverse kinematic transformation. A computationally efficient numerical solution was obtained for the end-effector forward kinematic transformation using Newton-Raphson method. Three trajectory planning schemes, two for fine motion and one for gross motion, were developed for the end-effector. Experiments conducted to evaluate the performance of the trajectory planning schemes showed excellent tracking quality with minimal errors. Current activities focus on implementing the developed trajectory planning schemes on mating and demating space-rated connectors and using the compliant platform to acquire forces/torques applied on the end-effector during the assembly task.

Nguyen, Charles C.↗

NASA NTRS1991

Space shuttle with common fuel tank for liquid rocket booster and main engines (supertanker space shuttle)

An operation and schedule enhancement is shown that replaces the four-body cluster (Space Shuttle Orbiter (SSO), external tank, and two solid rocket boosters) with a simpler two-body cluster (SSO and liquid rocket booster/external tank). At staging velocity, the booster unit (liquid-fueled booster engines and vehicle support structure) is jettisoned while the remaining SSO and supertank continues on to orbit. The simpler two-bodied cluster reduces the processing and stack time until SSO mate from 57 days (for the solid rocket booster) to 20 days (for the liquid rocket booster). The areas in which liquid booster systems are superior to solid rocket boosters are discussed. Alternative and future generation vehicles are reviewed to reveal greater performance and operations enhancements with more modifications to the current methods of propulsion design philosophy, e.g., combined cycle engines, and concentric propellant tanks.

Thorpe, Douglas G.↗

NASA NTRS1991

A study of space-rated connectors using a robotic end-effector

The fabrication and testing of a pair of robot fingers designed to grasp two types of Orbital Replacement Unit (ORU) interfaces, the H Handle type and the Micro Square type are discussed. A closed-form solution is given for the force inverse kinematics. A numerical solution using the Newton-Raphson Method for force forward kinematics is given. Mathematical expressions are derived to compute forces/torques applied to the finger. Suggestions are given for improving finger fabrication. The results of numerous experiments conducted to study the characteristics and feasibility of the fingers are given. The first part of the study was devoted to obtaining data on the forces applied by the finger to the interfaces under various translational and rotational misalignments; the second part was devoted to determining the maximum allowed capture angles that would insure successful mating; and the third part was devoted to the processing and interpretation of the forces/torque data.

Nguyen, Charles C.↗

NASA NTRS1991

Apparatus and method for explosive bonding to edge of flyer plate

The invention is an apparatus and a process for the explosive joining of a flyer plate and a base plate. The apparatus consists of a flyer plate positioned over a base plate. The flyer plate has a notch containing a filler material in intimate contact with the flyer plate. An adhesive means holds a ribbon explosive partially overlapping the notch in the flyer plate. A detonating means initiates the ribbon explosive that drives the flyer plate to accomplish a high velocity, angular collision between the mating surfaces. This collision creates surface melts and effacing bonding, resulting in electron sharing linkups between the plates. An unbonded tab fractures at a base of the notch leaving a bond to an edge of the attached flyer plate.

Bement, Laurence J.↗

NASA NTRS1991

Contact stresses in gear teeth - A new method of analysis

A new, innovative procedure called point load superposition for determining the contact stresses in mating gear teeth is presented. It is believed that this procedure will greatly extend both the range of applicability and the accuracy of gear contact stress analysis. Point load superposition is based upon fundamental solutions from the theory of elasticity. It is an iterative numerical procedure which has distinct advantages over the classical Hertz method, the finite element method, and over existing applications with the boundary element method. Specifically, friction and sliding effects, which are either excluded from or difficult to study with the classical methods, are routinely handled with the new procedure. Presented here are the basic theory and the algorithms. Several examples are given. Results are consistent with those of the classical theories. Applications to spur gears are discussed.

Somprakit, Paisan↗

NASA NTRS1991

The rheology and hydrodynamics of dry powder lubrication

This paper conceptualizes a powder lubrication mechanisms which closely resembles that of a hydrodynamic fluid film. Based on the observations of past investigations and on the author's experiments, it is postulated that a layered shearing of the compacted powder generates velocity, density, and temperature profiles akin to fluid film bearings. Thus, a lubricant consisting of a fine powder unserted either deliberately or one generated by the water of the mating surfaces, constitutes a viable lubricant that generates the required flows and pressures to prevent contact between the surfaces.

Heshmat, Hooshang↗

NASA NTRS1992

Soft-Capture Mechanism For Collet Joint

Soft-capture mechanism part of latching-and-rigidifying mechanism joining strut rigidly to node on truss. Latching-and-rigidifying mechanism of spreading-collet type, in which collet inserted into base that mates with collet to assure proper alignment, then collet spread to rigidify joint, fixing alignment. Designed to be operable by heavily gloved hand or by robot.

Huff, John E., Jr.↗

NASA NTRS1992

Probe And Drogue For Quick Attachment And Detachment

Prototype probe-and-drogue attachment mechanism connects and disconnects parts quickly and locks them together positively. Probe intended to be capturing stud, and drogue is mating recess in panel to be captured, as described in "Easy Attachment Of Panels To A Truss" (LAR-14478). Accommodates large alignment error when parts brought together.

Thomson, Mark↗

NASA NTRS1992

Tapered-Fin Thermal Interfaces

Two meshing sets of tapered fins used as thermal interface with relatively low clamping forces. When in contact, fins provide large area for transfer of heat. Taper ensures easy mating and demating of fins and transfers clamping force to surfaces in contact; improving contact and transfer of heat. Fins arranged in rows, concentric rings, or other configurations.

Poulin, Elizabeth C.↗

NASA NTRS1992

Self-Aligning, Spline-Locking Fastener

Self-aligning, spline-locking fastener is two-part mechanism operated by robot, using one tool and simple movements. Spline nut on springloaded screw passes through mating spline fitting. Operator turns screw until vertical driving surfaces on spline nut rest against corresponding surfaces of spline fitting. Nut rides upward, drawing pieces together. Used to join two parts of structure, to couple vehicles, or to mount payload in vehicle.

Vranish, John M.↗

NASA NTRS1992

Tool Would Grip Round Electrical Connectors

Proposed version of commercially available tool makes it easier to mate and demate round, bayonet-mount, multipin electrical connectors in densely populated connector panels without removing adjacent connectors. Inner surface of cylindrical shell smooth with tapered lip gripping knurled outer ring on connector.

Camarata, Terrence L.↗

NASA NTRS1992

Self-Aligning Cranked Latch

Latching mechanism designed to be quick-acting, self-aligning, and rigid when set useful in applications where users cannot observe mating and latching process. Mechanism is driven-pin, rigidized-clevis device in which pin actuated by crank and slider. Crank turned by hand or by motor.

Redmon, John W., Jr.↗

NASA NTRS1992

Robots Would Couple And Uncouple Fluid And Electrical Lines

Robots make and break connections between umbilical plates and mating connectors on rockets about to be launched. Sensing and control systems include vision, force, and torque subsystems. Enhances safety by making it possible to couple and uncouple umbilical plates quickly, without exposing human technicians to hazards of leaking fuels and oxidizers. Significantly reduces time spent to manually connect umbilicals. Robots based on similar principles used in refueling of National AeroSpace Plane (NASP) and satellites and orbital transfer vehicles in space.

Del Castillo, Eduardo Lopez↗

NASA NTRS1992

Robotic Gripper Resists Torsion And Lateral Forces

Gripper for end effector of robot shaped to tolerate large initial misalignments with object gripped. Gripping surfaces contoured to prevent lateral forces from prying them apart. Ridges on handle mate with grooves in finger. Same ridge-end-slope pattern appears on opposite face of handle so two opposed fingers grip it.

Voellmar, George M.↗

NASA NTRS1992

Rolling-Friction Robotic Gripper

Robotic gripper using rolling-friction fingers closes in on object with interface designed to mate with rollers somewhat misaligned initially, aligns object with respect to itself, then holds object securely in uniquely determined position and orientation. Operation of gripper causes minimal wear and burring of gripper and object. Exerts minimal friction forces on object when grasping and releasing. Releases object easily and reliably even when side forces and torques are between itself and object.

Vranish, John M.↗

NASA NTRS1992

Split-Rail, Rolling-Friction Robotic Gripper With Tool Drive

Robotic gripper includes split-rail drive assembly that moves two gripping fingers toward or away from each other. Gripping fingers equipped with rollers mating with recesses and seating ramps on specially designed object. Similar in design and operation, to those described in "Rolling-Friction Robotic Gripper" (GSC-13261). Present gripper includes rotary tool operating on mechanism in gripped object.

Voellmer, George M.↗

NASA NTRS1991

Sedimentary organic molecules: Origins and information content

To progress in the study of organic geochemistry, we must dissect the processes controlling the composition of sedimentary organic matter. Structurally, this has proven difficult. Individual biomarkers can often be recognized, but their contribution to total organic materials is small, and their presence does not imply that their biochemical cell mates have survived. We are finding, however, that a combination of structural and isotopic lines of evidence provides new information. A starting point is provided by the isotopic compositions of primary products (degradation products of chlorophylls, alkenones derived from coccoliths). We find strong evidence that the isotopic difference between primary carbonate and algal organic material can be interpreted in terms of the concentration of dissolved CO2. Moreover, the isotopic difference between primary and total organic carbon can be interpreted in terms of characteristic isotopic shifts imposed by secondary processes (responsive, for example, to O2 levels in the depositional environment. In favorable cases, isotopic compositions of a variety of secondary products can be interpreted in terms of flows of carbon, and, therefore, in terms of specific processes and environmental conditions within the depositional environment.

Hayes, J. M.↗

NASA NTRS1991

Permanent wire splicing by an explosive joining process

The invention is an apparatus and method for wire splicing using an explosive joining process. The apparatus consists of a prebent, U-shaped strap of metal that slides over prepositioned wires. A standoff means separates the wires from the strap before joining. An adhesive means holds two ribbon explosives in position centered over the U-shaped strap. A detonating means connects to the ribbon explosives. The process involves spreading strands of each wire to be joined into a flat plane. The process then requires alternating each strand in alignment to form a mesh-like arrangement with an overlapped area. The strap slides over the strands of the wires, and the standoff means is positioned between the two surfaces. The detonating means then initiates the ribbon explosives that drive the strap to accomplish a high velocity, angular collision between the mating surfaces. This collision creates surface melts and collision bonding results in electron sharing linkups.

Bement, Laurence J.↗