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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records

All sources NASA NTRS DOE OSTI

NASA NTRS1990

Experiments in cooperative-arm object manipulation with a two-armed free-flying robot

Developing computed-torque controllers for complex manipulator systems using current techniques and tools is difficult because they address the issues pertinent to simulation, as opposed to control. A new formulation of computed-torque (CT) control that leads to an automated computer-torque robot controller program is presented. This automated tool is used for simulations and experimental demonstrations of endpoint and object control from a free-flying robot. A new computed-torque formulation states the multibody control problem in an elegant, homogeneous, and practical form. A recursive dynamics algorithm is presented that numerically evaluates kinematics and dynamics terms for multibody systems given a topological description. Manipulators may be free-flying, and may have closed-chain constraints. With the exception of object squeeze-force control, the algorithm does not deal with actuator redundancy. The algorithm is used to implement an automated 2D computed-torque dynamics and control package that allows joint, endpoint, orientation, momentum, and object squeeze-force control. This package obviates the need for hand-derivation of kinematics and dynamics, and is used for both simulation and experimental control. Endpoint control experiments are performed on a laboratory robot that has two arms to manipulate payloads, and uses an air bearing to achieve very-low drag characteristics. Simulations and experimental data for endpoint and object controllers are presented for the experimental robot - a complex dynamic system. There is a certain rather wide set of conditions under which CT endpoint controllers can neglect robot base accelerations (but not motions) and achieve comparable performance including base accelerations in the model. The regime over which this simplification holds is explored by simulation and experiment.

Koningstein, Ross↗

NASA NTRSDate not supplied

Comparing Human Input in RViz and Virtual Reality Interfaces for 3D Object Manipulation Tasks

Effective human-in-the-loop robot control requires intuitive and easy to use interfaces. We present a within-subjects user study design to compare the ease of use of interfaces for human-robot teleoperation, specifically the ROS 3D visualization tool RViz and a virtual reality interface. Our proposed study will determine which interface is easiest to use and minimizes operator cognitive load in shared autonomy tasks.

Emily Sheetz↗

NASA NTRS1980

Manipulation of large objects

Remote manipulator control experiments have been conducted to investigate the problems related to the 'controlled collision' aspect of manipulation. A six degrees of freedom pantograph arm with a six-dimensional force-torque balance sensor and microprocessor-driven real-time graphics display are employed in the experiments. Among other results, it is found that the use of computer force-torque feedback loop for 'stop at contact' provides a nearly linear relation between load transfer to jigs at 'stop at contact', rate of motion, and preset force-torque threshold values for stop under limited motion and load conditions.

Bejczy, A. K.↗

NASA NTRS1989

Object impedance control for cooperative manipulation - Theory and experimental results

The dynamic control module being developed in the Dynamic and Strategic Control of Cooperative Manipulators (DASCCOM) project at the Stanford University Aerospace Robotics Laboratory is described. First, the cooperative manipulation problem is analyzed from a systems perspective, and the desirable features of a control system for cooperative manipulation are discussed. Next, a control policy is developed that enforces a controlled impedance not of the individual arm endpoints, but of the manipulated object itself. A parallel implementation for a multiprocessor system is presented. The controller fully compensates for the system dynamics and directly controls the object internal forces. Most importantly, it presents a simple, powerful, intuitive interface to the strategic controller. Experimental results for a dual two-link arm robotic system are presented to verify the controllers performance, for both free-motion slews and environmental contact.

Schneider, Stanley A.↗

NASA NTRS1992

Object impedance control for cooperative manipulation - Theory and experimental results

This paper presents the dynamic control module of the Dynamic and Strategic Control of Cooperating Manipulators (DASCCOM) project at Stanford University's Aerospace Robotics Laboratory. First, the cooperative manipulation problem is analyzed from a systems perspective, and the desirable features of a control system for cooperative manipulation are discussed. Next, a control policy is developed that enforces a controlled impedance not of the individual arm endpoints, but of the manipulated object itself. A parallel implementation for a multiprocessor system is presented. The controller fully compensates for the system dynamics and directly controls the object internal forces. Most importantly, it presents a simple, powerful, intuitive interface to higher level strategic control modules. Experimental results from a dual two-link-arm robotic system are used to compare the object impedance controller with other strategies, both for free-motion slews and environmental contact.

Schneider, Stanley A.↗

DOE OSTI2024

Airborne Acoustic Vortex End Effector‐Based Contactless, Multi‐Mode, Programmable Control of Object Surfing

Abstract Tweezers based on optical, electric, magnetic, and acoustic fields have shown great potential for contactless object manipulation. However, current tweezers designed for manipulating millimeter‐sized objects such as droplets, particles, and small animals exhibit limitations in translation resolution, range, and path complexity. Here, a novel acoustic vortex tweezers system is introduced, which leverages a unique airborne acoustic vortex end effector integrated with a three‐degree‐of‐freedom (DoF) linear motion stage, for enabling contactless, multi‐mode, programmable manipulation of millimeter‐sized objects. The acoustic vortex end effector utilizes a cascaded circular acoustic array, which is portable and battery‐powered, to generate an acoustic vortex with a ring‐shaped energy pattern. The vortex applies acoustic radiation forces to trap and spin an object at its center, simultaneously protecting this object by repelling other materials away with its high‐energy ring. Moreover, The vortex tweezers system facilitates contactless, multi‐mode, programmable object surfing, as demonstrated in experiments involving trapping, repelling, and spinning particles, translating particles along complex paths, guiding particles around barriers, translating and rotating droplets containing zebrafish larvae, and merging droplets. With these capabilities, It is anticipated that the tweezers system will become a valuable tool for the automated, contactless handling of droplets, particles, and bio‐samples in biomedical and biochemical research.

Li, Teng↗

NASA NTRS2006

System and method for confining an object to a region of fluid flow having a stagnation point

A device for confining an object to a region proximate to a fluid flow stagnation point includes one or more inlets for carrying the fluid into the region, one or more outlets for carrying the fluid out of the region, and a controller, in fluidic communication with the inlets and outlets, for adjusting the motion of the fluid to produce a stagnation point in the region, thereby confining the object to the region. Applications include, for example, prolonged observation of the object, manipulation of the object, etc. The device optionally may employ a feedback control mechanism, a sensing apparatus (e.g., for imaging), and a storage medium for storing, and a computer for analyzing and manipulating, data acquired from observing the object. The invention further provides methods of using such a device and system in a number of fields, including biology, chemistry, physics, material science, and medical science.

Schroeder, Charles M.↗

NASA NTRS1989

Spatial constraints of stereopsis in video displays

Recent development in video technology, such as the liquid crystal displays and shutters, have made it feasible to incorporate stereoscopic depth into the 3-D representations on 2-D displays. However, depth has already been vividly portrayed in video displays without stereopsis using the classical artists' depth cues described by Helmholtz (1866) and the dynamic depth cues described in detail by Ittleson (1952). Successful static depth cues include overlap, size, linear perspective, texture gradients, and shading. Effective dynamic cues include looming (Regan and Beverly, 1979) and motion parallax (Rogers and Graham, 1982). Stereoscopic depth is superior to the monocular distance cues under certain circumstances. It is most useful at portraying depth intervals as small as 5 to 10 arc secs. For this reason it is extremely useful in user-video interactions such as telepresence. Objects can be manipulated in 3-D space, for example, while a person who controls the operations views a virtual image of the manipulated object on a remote 2-D video display. Stereopsis also provides structure and form information in camouflaged surfaces such as tree foliage. Motion parallax also reveals form; however, without other monocular cues such as overlap, motion parallax can yield an ambiguous perception. For example, a turning sphere, portrayed as solid by parallax can appear to rotate either leftward or rightward. However, only one direction of rotation is perceived when stereo-depth is included. If the scene is static, then stereopsis is the principal cue for revealing the camouflaged surface structure. Finally, dynamic stereopsis provides information about the direction of motion in depth (Regan and Beverly, 1979). Clearly there are many spatial constraints, including spatial frequency content, retinal eccentricity, exposure duration, target spacing, and disparity gradient, which - when properly adjusted - can greatly enhance stereodepth in video displays.

Schor, Clifton↗

NASA NTRS1991

Anthropomorphic Remote Manipulator

Two-armed telerobot undergoing development manipulates objects with dexterity approaching that of human. Designed to be remotely operated by human. Operator wears harness with exoskeletonlike sleeves and gloves; remote manipulator follows operator's arm, hand, and finger movements and feeds back position and force information so operator has sense of manipulating object held by telerobot. Developed for use in outer space. Suited for such terrestrial uses as handling materials and maintaining equipment in hazardous environments where mechanical dexterity and nearly instantaneous feedback of sensory information needed.

Jau, Bruno M.↗

NASA NTRS1984

The representation of manipulable solid objects in a relational database

This project is concerned with the interface between database management and solid geometric modeling. The desirability of integrating computer-aided design, manufacture, testing, and management into a coherent system is by now well recognized. One proposed configuration for such a system uses a relational database management system as the central focus; the various other functions are linked through their use of a common data repesentation in the data manager, rather than communicating pairwise to integrate a geometric modeling capability with a generic relational data managemet system in such a way that well-formed questions can be posed and answered about the performance of the system as a whole. One necessary feature of any such system is simplification for purposes of anaysis; this and system performance considerations meant that a paramount goal therefore was that of unity and simplicity of the data structures used.

Bahler, D.↗

NASA NTRS2007

Learning Grasp Strategies Composed of Contact Relative Motions

Of central importance to grasp synthesis algorithms are the assumptions made about the object to be grasped and the sensory information that is available. Many approaches avoid the issue of sensing entirely by assuming that complete information is available. In contrast, this paper proposes an approach to grasp synthesis expressed in terms of units of control that simultaneously change the contact configuration and sense information about the object and the relative manipulator-object pose. These units of control, known as contact relative motions (CRMs), allow the grasp synthesis problem to be recast as an optimal control problem where the goal is to find a strategy for executing CRMs that leads to a grasp in the shortest number of steps. An experiment is described that uses Robonaut, the NASA-JSC space humanoid, to show that CRMs are a viable means of synthesizing grasps. However, because of the limited amount of information that a single CRM can sense, the optimal control problem may be partially observable. This paper proposes expressing the problem as a k-order Markov Decision Process (MDP) and solving it using Reinforcement Learning. This approach is tested in a simulation of a two-contact manipulator that learns to grasp an object. Grasp strategies learned in simulation are tested on the physical Robonaut platform and found to lead to grasp configurations consistently.

Platt, Robert, Jr.↗

NASA NTRS2001

Planning of reach-and-grasp movements: effects of validity and type of object information

Individuals are assumed to plan reach-and-grasp movements by using two separate processes. In 1 of the processes, extrinsic (direction, distance) object information is used in planning the movement of the arm that transports the hand to the target location (transport planning); whereas in the other, intrinsic (shape) object information is used in planning the preshaping of the hand and the grasping of the target object (manipulation planning). In 2 experiments, the authors used primes to provide information to participants (N = 5, Experiment 1; N = 6, Experiment 2) about extrinsic and intrinsic object properties. The validity of the prime information was systematically varied. The primes were succeeded by a cue, which always correctly identified the location and shape of the target object. Reaction times were recorded. Four models of transport and manipulation planning were tested. The only model that was consistent with the data was 1 in which arm transport and object manipulation planning were postulated to be independent processes that operate partially in parallel. The authors suggest that the processes involved in motor planning before execution are primarily concerned with the geometric aspects of the upcoming movement but not with the temporal details of its execution.

Cues↗

NASA NTRS2006

Tilt/Tip/Piston Manipulator with Base-Mounted Actuators

A proposed three-degree-of-freedom (tilt/tip/piston) manipulator, suitable for aligning an optical or mechanical component, would offer several advantages over prior such manipulators: Unlike in some other manipulators, no actuator would support the weight of another actuator: All of the actuators would be mounted on a base. Hence, there would be less manipulated weight. The basic geometry of the manipulator would afford mechanical advantage: that is, actuator motions would be larger than the motions they produce in the manipulated object. Mechanical advantage inherently increases the accuracy and resolution of manipulation. Unlike in some other manipulators, it would not be necessary to route power and/or data lines through manipulator joints. The proposed manipulator (see figure) would include three prismatic actuators (T1N1, T2N2, and T3N3) mounted on the base and operating in the same plane. Examples of suitable prismatic actuators include lead-screw mechanisms, linear hydraulic motors, piezoelectric linear drives, inchworm-movement linear stepping motors, and linear flexure drives. The actuators would control the lengths of links R1T1, R2T2, and R3T3. Three spherical joints (P1, P2, and P3) would be located at the corners of an equilateral triangle of side length q on the platform holding the object to be manipulated. Three inextensible limbs (R1P1, R2P2, and R3P3) having length r would connect the spherical joints on the platform to revolute joints (R1, R2, and R3) at the ends of the actuator-controlled links R1T1, R2T2, and R3T3. By varying the lengths of these links, one could control the tilt, tip, and piston coordinates of the platform. Closed-form equations for direct or forward kinematics of the manipulator (given the lengths of the variable links, find the tilt, tip, and piston coordinates) have been derived. The equations of inverse kinematics (find the variable link lengths needed to obtain the desired tilt, tip, and piston coordinates) have also been derived.

Tahmasebi, Farhad↗

NASA NTRS1988

Integration of a computerized two-finger gripper for robot workstation safety

A microprocessor-based controller has been developed that continuously monitors and adjusts the gripping force applied by a special two-finger gripper. This computerized force sensing gripper system enables the endeffector gripping action to be independently detected and corrected. The gripping force applied to a manipulated object is real-time monitored for problem situations, situations which can occur during both planned and errant robot arm manipulation. When unspecified force conditions occur at the gripper, the gripping force controller initiates specific reactions to cause dynamic corrections to the continuously variable gripping action. The force controller for this intelligent gripper has been interfaced to the controller of an industrial robot. The gripper and robot controllers communicate to accomplish the successful completion of normal gripper operations as well as unexpected hazardous situations. An example of an unexpected gripping condition would be the sudden deformation of the object being manipulated by the robot. The capabilities of the interfaced gripper-robot system to apply workstation safety measures (e.g., stop the robot) when these unexpected gripping effects occur have been assessed.

Sneckenberger, John E.↗

NASA NTRS2003

Compliant Gripper for a Robotic Manipulator

A 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.

Cipra, Raymond↗

NASA NTRS2013

Hierarchical Robot Control System and Method for Controlling Select Degrees of Freedom of an Object Using Multiple Manipulators

A robotic system includes a robot having manipulators for grasping an object using one of a plurality of grasp types during a primary task, and a controller. The controller controls the manipulators during the primary task using a multiple-task control hierarchy, and automatically parameterizes the internal forces of the system for each grasp type in response to an input signal. The primary task is defined at an object-level of control, e.g., using a closed-chain transformation, such that only select degrees of freedom are commanded for the object. A control system for the robotic system has a host machine and algorithm for controlling the manipulators using the above hierarchy. A method for controlling the system includes receiving and processing the input signal using the host machine, including defining the primary task at the object-level of control, e.g., using a closed-chain definition, and parameterizing the internal forces for each of grasp type.

Abdallah, Muhammad E.↗

NASA NTRS1997

Visual Computing Environment

The Visual Computing Environment (VCE) is a NASA Lewis Research Center project to develop a framework for intercomponent and multidisciplinary computational simulations. Many current engineering analysis codes simulate various aspects of aircraft engine operation. For example, existing computational fluid dynamics (CFD) codes can model the airflow through individual engine components such as the inlet, compressor, combustor, turbine, or nozzle. Currently, these codes are run in isolation, making intercomponent and complete system simulations very difficult to perform. In addition, management and utilization of these engineering codes for coupled component simulations is a complex, laborious task, requiring substantial experience and effort. To facilitate multicomponent aircraft engine analysis, the CFD Research Corporation (CFDRC) is developing the VCE system. This system, which is part of NASA's Numerical Propulsion Simulation System (NPSS) program, can couple various engineering disciplines, such as CFD, structural analysis, and thermal analysis. The objectives of VCE are to (1) develop a visual computing environment for controlling the execution of individual simulation codes that are running in parallel and are distributed on heterogeneous host machines in a networked environment, (2) develop numerical coupling algorithms for interchanging boundary conditions between codes with arbitrary grid matching and different levels of dimensionality, (3) provide a graphical interface for simulation setup and control, and (4) provide tools for online visualization and plotting. VCE was designed to provide a distributed, object-oriented environment. Mechanisms are provided for creating and manipulating objects, such as grids, boundary conditions, and solution data. This environment includes parallel virtual machine (PVM) for distributed processing. Users can interactively select and couple any set of codes that have been modified to run in a parallel distributed fashion on a cluster of heterogeneous workstations. A scripting facility allows users to dictate the sequence of events that make up the particular simulation.

Lawrence, Charles↗

NASA NTRS1989

Adaptive Force And Position Control For Robots

Control system causes end effector of robot manipulator to follow prescribed trajectory and applies desired force or torque to object manipulating or in contact. Characterized by hybrid control architecture, where positions and orientations along unconstrained coordinate axes controlled by position-control subsystem, while forces and torques along constrained coordinate axes controlled by force-control subsystem. Compensates for dynamic cross-coupling between force-and position-control loops and does not require knowledge of complicated model of dynamics of manipulator and environment.

Seraji, Homayoun↗