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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Base reaction optimization of manipulators with redundant kinematics

A trajectory generation method for space manipulators is introduced. The approach developed employs a manipulator with redundant kinematics. The method is implemented in two steps. First, the end-effector trajectory is developed to satisfy motion requirements. Next, the joint trajectories are developed to minimize base reactions. The analytical development of this method is described and an example illustrating the method is presented.

Chung, C. L.↗
NASA NTRS1988

Kinematics of Hooke universal joint robot wrists

The singularity problem associated with wrist mechanisms commonly found on industrial manipulators can be alleviated by redesigning the wrist so that it functions as a three-axis gimbal system. This paper discussess the kinematics of gimbal robot wrists made of one and two Hooke universal joints. Derivations of the resolved rate motion control equations for the single and double Hooke universal joint wrists are presented using the three-axis gimbal system as a theoretical wrist model.

Mckinney, William S., Jr.↗
NASA NTRS1987

A kinematic model for the evolution of the Gorda Plate

The magnetic lineation pattern produced by the Gorda Rise reflects a complex tectonic history marked by propagating ridges and nonrigid deformation of the Gorda plate. The Pacific-side lineation pattern is matched using a kinematic model which incorporates northward and southward propagating ridge segments and ridge rotation. By superimposing flexural-slip style deformation on the resulting Gorda-side lineations, and allowing convergent motion at the Mendocino Fracture Zone, the Gorda magnetic pattern is also successfully predicted. A similar model, but one which does not allow convergence at the Mendocino Fracture Zone, fails to produce the observed lineation pattern. Model predictions of the amount of material that would be 'obducted' at the Mendocino due to convergence between the Gorda and Pacific agree with bathymetric and density estimates of the amount of material located along the Mendocino Ridge.

Stoddard, Paul R.↗
NASA NTRS1988

Evolution of large-sclae plasma structures in comets: Kinematics and physics

Disconnection Events are the dramatic part of the periodic morphology involving the separation of the entire plasma tail from the head region of the comet and the growth of a new plasma. The coordinated observations of Comet Halley recorded approximately 30 DEs during the 7 months of plasma activity; 19 of these are obvious. The plasma physics of these events were approached via a detailed, kinematic investigation of specific DEs and the solar-wind environment associated with it. As the detailed investigations are completed, researchers should be able to answer the question of a single or multiple mechanism(s) for DEs and determine which mechanism(s) are important. At present, the mechanism of sunward magnetic reconnection caused by interplanetary sector boundary crossing in consistent with the data available.

Brandt, John C.↗
NASA NTRS1989

Kinematics at the Intersection of the Garlock and Death Valley Fault Zones, California: Integration of TM Data and Field Studies

Kinematic relationships at the intersection of the southern Death Valley and Garlock fault zones were examined to identify and delineate the eastern structural boundary between the Mojave and the Basin and Range geologic terrains, and to construct a model for the evolution of this boundary through time. In order to accomplish this, satellite imagery was combined with field investigations to study six areas in the vicinity of the intersection, or possible extensions, of the fault zones. The information gathered from these areas allows the test of various hypotheses that were proposed to explain the interaction between the Death Valley and Garlock fault zones.

Verosub, Kenneth L.↗
NASA NTRS1987

Parallel processing architecture for computing inverse differential kinematic equations of the PUMA arm

In advanced robot control problems, on-line computation of inverse Jacobian solution is frequently required. Parallel processing architecture is an effective way to reduce computation time. A parallel processing architecture is developed for the inverse Jacobian (inverse differential kinematic equation) of the PUMA arm. The proposed pipeline/parallel algorithm can be inplemented on an IC chip using systolic linear arrays. This implementation requires 27 processing cells and 25 time units. Computation time is thus significantly reduced.

Hsia, T. C.↗
NASA NTRS1988

Coordination of dual robot arms using kinematic redundancy

A method is developed to coordinate the motion of dual robot arms carrying a solid object, where the first robot (leader) grasps one end of the object rigidly and the second robot (follower) is allowed to change its grasping position at the other end of the object along the object surface while supporting the object. It is shown that this flexible grasping is equivalent to the addition of one more degree of freedom (dof), giving the follower more maneuvering capabilities. In particular, motion commands for the follower are generated by using kinematic redundancy. To show the utility and power of the method, an example system with two PUMA 560 robots carrying a beam is analyzed.

Suh, Il Hong↗
NASA NTRS1988

Kinematic calibration of manipulators with closed loop actuated joints

A method for performing forward kinematic calibration of manipulators having one or more closed-loop-actuated joints is presented. The technique is an extension of algorithms designed for open-loop jointed manipulators. The calibration is equivalent to minimizing an objective function subject to constraints. The objective function is taken as the integral of end-effector position and orientation error. The constraints arise from the closed-loop mechanisms present in the manipulator.

Everett, Louis J.↗
NASA NTRS1988

A study of kinematic models for forward calibration of manipulators

The objective of robot calibration is to identify all parameters in a robot model so that the model represents the true robot. Each model has its own set of parameters. The authors prove that regardless of the kinematic model chosen, there are a maximum number of parameters that must be determined, implying that model accuracy cannot be improved by adding parameters. In addition, the authors demonstrate how to model any manipulator so that a minimum size Jacobian is used, thus reducing the computation required for calibration.

Everett, Louis J.↗
NASA NTRS1988

Kinematics and ionization of extended gas in active galaxies. IV - The Seyfert 2 galaxy NGC 4388

The results of direct CCD imaging and long-slit medium-dispersion spectroscopy of the extended narrow-line-emitting gas in the nearby Seyfert 2 galaxy NGC 4388 are presented. The spectra are used to investigate the distribution, kinematics, and ionization structure of the excited gas in the regions surrounding the nucleus out to a distance of about 4.8 kpc. The data support earlier suggestions that the galaxy, which appears to lie near the core of the Virgo cluster, has been tidally distorted, possibly by the nearby cluster core galaxies M84 or IC 3303. Much of the highly ionized gas in the galaxy appears to be distributed in two wide cones originating from the nucleus and extending above and below the disk. Explanations are offered for the distribution of this gas and for the remainder of the gas above and below the disk.

Corbin, Michael R.↗
NASA NTRS1988

The kinematics and dynamics of the rich cluster of galaxies Abell 539

A sample of 289 redshifts within 10 deg of the center of the cluster A539 have been obtained in order to investigate the cluster kinematics and dynamics. Within 1 Mpc of the center, the physical parameters of A539 are found to be typical of those of rich clusters. It is shown that early-type galaxies are more concentrated toward the cluster center and that the velocity distributions of early-type and late-type galaxies differ marginally.

Ostriker, Eve C.↗
NASA NTRS1989

Kinematic evidence for a relativistic Keplerian disk - Arp 102B

Line profiles were calculated for a Keplerian disk with allowance made for relativistic effects. Excellent agreement was found between the resulting double peaked asymmetric profiles and the H-alpha line of Arp 102B; this yielded an accurate determination of several disk parameters. It is believed that the line profile of Arp 102B shows the most convincing direct kinematic evidence for rotation in any AGN.

Chen, Kaiyou↗
NASA NTRS1989

The kinematics of Milky Way halo gas. I - Observations of low-ionization species

Ultraviolet interstellar line day observed with the IUE toward 70 halo stars and four extragalactic sight lines are analyzed in a study of the large-scale kinematic properties of the Milky Way halo gas. The motions of the low-ionization gas is focused on. Large systematic velocities are found, and a pronounced asymmetry in the absorption characteristics of halo gas toward the Galactic poles is indicated. In the north, substantial amounts of material are falling toward the disk at velocities up to about 120 km/s in the most extreme case. Toward the south, low-ionization material shows no extreme or systematic motions.

Danly, Laura↗
NASA NTRS1989

A framework for modelling kinematic measurements in gravity field applications

To assess the resolution of the local gravity field from kinematic measurements, a state model for motion in the gravity field of the earth is formulated. The resulting set of equations can accommodate gravity gradients, specific force, acceleration, velocity and position as input data and can take into account approximation errors as well as sensor errors.

Schwarz, K. P.↗
NASA NTRS1989

Kinematic functions for the 7 DOF robotics research arm

The Robotics Research Model K-1207 manipulator is a redundant 7R serial link arm with offsets at all joints. To uniquely determine joint angles for a given end-effector configuration, the redundancy is parameterized by a scalar variable which corresponds to the angle between the manipulator elbow plane and the vertical plane. The forward kinematic mappings from joint-space to end-effector configuration and elbow angle, and the augmented Jacobian matrix which gives end-effector and elbow angle rates as a function of joint rates, are also derived.

Kreutz, K.↗
NASA NTRS1989

Reflexive obstacle avoidance for kinematically-redundant manipulators

Dexterous telerobots incorporating 17 or more degrees of freedom operating under coordinated, sensor-driven computer control will play important roles in future space operations. They will also be used on Earth in assignments like fire fighting, construction and battlefield support. A real time, reflexive obstacle avoidance system, seen as a functional requirement for such massively redundant manipulators, was developed using arm-mounted proximity sensors to control manipulator pose. The project involved a review and analysis of alternative proximity sensor technologies for space applications, the development of a general-purpose algorithm for synthesizing sensor inputs, and the implementation of a prototypical system for demonstration and testing. A 7 degree of freedom Robotics Research K-2107HR manipulator was outfitted with ultrasonic proximity sensors as a testbed, and Robotics Research's standard redundant motion control algorithm was modified such that an object detected by sensor arrays located at the elbow effectively applies a force to the manipulator elbow, normal to the axis. The arm is repelled by objects detected by the sensors, causing the robot to steer around objects in the workspace automatically while continuing to move its tool along the commanded path without interruption. The mathematical approach formulated for synthesizing sensor inputs can be employed for redundant robots of any kinematic configuration.

Karlen, James P.↗
NASA NTRS1989

Dynamical modeling of serial manipulators with flexible links and joints using the method of kinematic influence

A method of formulating the dynamical equations of a flexible, serial manipulator is presented, using the Method of Kinematic Influence. The resulting equations account for rigid body motion, structural motion due to link and joint flexibilities, and the coupling between these two motions. Nonlinear inertial loads are included in the equations. A finite order mode summation method is used to model flexibilities. The structural data may be obtained from experimental, finite element, or analytical methods. Nonlinear flexibilities may be included in the model.

Graves, Philip L.↗
NASA NTRS1988

A kinematic model of ridge-transform geometry evolution

A simple kinematic model is used to study the effects of various parameters on the evolution of zero-offset transforms and very-long-offset transforms. Consideration is given to the effects of initial configuration, degree of asymmetry, and degree of bias in asymmetry on the generation of these ridge transform geometries and on the possible steady-state nature of the transform length spectra. Of the parameters tests, only lack of 'memory' of zero-offset transforms affects transform length distribution.

Stoddard, Paul R.↗