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At least 235 records · Page 13

Tool actuation and force feedback on robot-assisted microsurgery system

An input control device with force sensors is configured to sense hand movements of a surgeon performing a robot-assisted microsurgery. The sensed hand movements actuate a mechanically decoupled robot manipulator. A microsurgical manipulator, attached to the robot manipulator, is activated to move small objects and perform microsurgical tasks. A force-feedback element coupled to the robot manipulator and the input control device provides the input control device with an amplified sense of touch in the microsurgical manipulator.

Das, Hari↗

A macro-micro robot for precise force applications

This paper describes an 8 degree-of-freedom macro-micro robot capable of performing tasks which require accurate force control. Applications such as polishing, finishing, grinding, deburring, and cleaning are a few examples of tasks which need this capability. Currently these tasks are either performed manually or with dedicated machinery because of the lack of a flexible and cost effective tool, such as a programmable force-controlled robot. The basic design and control of the macro-micro robot is described in this paper. A modular high-performance multiprocessor control system was designed to provide sufficient compute power for executing advanced control methods. An 8 degree of freedom macro-micro mechanism was constructed to enable accurate tip forces. Control algorithms based on the impedance control method were derived, coded, and load balanced for maximum execution speed on the multiprocessor system.

Marzwell, Neville I.↗

Effects of static fingertip loading on carpal tunnel pressure

The purpose of this study was to explore the relationship between carpal tunnel pressure and fingertip force during a simple pressing task. Carpal tunnel pressure was measured in 15 healthy volunteers by means of a saline-filled catheter inserted percutaneously into the carpal tunnel of the nondominant hand. The subjects pressed on a load cell with the tip of the index finger and with 0, 6, 9, and 12 N of force. The task was repeated in 10 wrist postures: neutral; 10 and 20 degrees of ulnar deviation; 10 degrees of radial deviation; and 15, 30, and 45 degrees of both flexion and extension. Fingertip loading significantly increased carpal tunnel pressure for all wrist angles (p = 0.0001). Post hoc analyses identified significant increase (p < 0.05) in carpal tunnel pressure between unloaded (0 N) and all loaded conditions, as well as between the 6 and 12 N load conditions. This study demonstrates that the process whereby fingertip loading elevates carpal tunnel pressure is independent of wrist posture and that relatively small fingertip loads have a large effect on carpal tunnel pressure. It also reveals the response characteristics of carpal tunnel pressure to fingertip loading, which is one step in understanding the relationship between sustained grip and pinch activities and the aggravation or development of median neuropathy at the wrist.

NASA Center ARC↗

LIS-Hydro: Authoritative Source for OCONUS Hydro-Intelligence

U.S. military forces are often tasked to participate in a variety of transboundary water-related decision-making activities, including humanitarian assistance operations through Department of State tasking, support of in-country infrastructure development activities that help develop or improve diplomatic relationships, and support of transboundary water treaty negotiations or disputes to reduce risk of conflict caused by water security issues. The U.S. intelligence communities have identified the coordination over shared water resources as an area of significant concern to U.S. national security (U.S. National Defense Strategy, 2018). Such transboundary water issues are projected to intensify in the future under increasingly complex population dynamics, political tensions due to parallel issues, and a changing climate. A 2017 joint NASA, USACE/RDC, and U.S. Air Force co-sponsored workshop revealed a lack of sufficient decision support tools and access to timely technical and contextual information needed to assess and respond to potential water-related threats around the world. The need for an integrated operational service, with the capacity to combine and synthesize hydrological modeling, assimilation, forecasting, and visualization capabilities across the U.S. Government, was highlighted as a key recommendation. In direct response, a subset of the U.S. Department of Defense, National Intelligence Community, and Oak Ridge National Laboratory are collaborating on the development of a fully integrated hydro-modeling and streamflow prediction system (i.e., LIS-Hydro). Completion of the project and sustainment of the operational capability by Air Force Weather will establish a national asset to assist federal agencies implement government-wide strategies around water resources (U.S. Global Water Strategy, 2017). The hydrological products and services will, for the very first time, establish a routinely available authoritative source of global water intelligence information supporting war-fighters, planners, and decision makers at all echelons and services of the U.S. military, Federal government, and intelligence community. A summary of the interagency scientific collaboration in addressing some of the key gaps and needs identified during the 2017 workshop will be presented.

Land Information System↗

Classification image analysis: estimation and statistical inference for two-alternative forced-choice experiments

We consider estimation and statistical hypothesis testing on classification images obtained from the two-alternative forced-choice experimental paradigm. We begin with a probabilistic model of task performance for simple forced-choice detection and discrimination tasks. Particular attention is paid to general linear filter models because these models lead to a direct interpretation of the classification image as an estimate of the filter weights. We then describe an estimation procedure for obtaining classification images from observer data. A number of statistical tests are presented for testing various hypotheses from classification images based on some more compact set of features derived from them. As an example of how the methods we describe can be used, we present a case study investigating detection of a Gaussian bump profile.

Non-NASA Center↗

Force-Measuring Clamps

Force-measuring clamps have been invented to facilitate and simplify the task of measuring the forces or pressures applied to clamped parts. There is a critical need to measure clamping forces or pressures in some applications for example, while bonding sensors to substrates or while clamping any sensitive or delicate parts. Many manufacturers of adhesives and sensors recommend clamping at specific pressures while bonding sensors or during adhesive bonding between parts in general. In the absence of a force-measuring clamp, measurement of clamping force can be cumbersome at best because of the need for additional load sensors and load-indicating equipment. One prior method of measuring clamping force involved the use of load washers or miniature load cells in combination with external power sources and load-indicating equipment. Calibrated spring clamps have also been used. Load washers and miniature load cells constitute additional clamped parts in load paths and can add to the destabilizing effects of loading mechanisms. Spring clamps can lose calibration quickly through weakening of the springs and are limited to the maximum forces that the springs can apply. The basic principle of a force-measuring clamp can be implemented on a clamp of almost any size and can enable measurement of a force of almost any magnitude. No external equipment is needed because the component(s) for transducing the clamping force and the circuitry for supplying power, conditioning the output of the transducers, and displaying the measurement value are all housed on the clamp. In other words, a force-measuring clamp is a complete force-application and force-measurement system all in one package. The advantage of unitary packaging of such a system is that it becomes possible to apply the desired clamping force or pressure with precision and ease.

Nunnelee, Mark↗

EMG-force dynamics in human skeletal muscle

On-line parameter tracking algorithm, obtaining parameters in mathematical relation between full wave rectified EMG and human triceps muscle force during isometric task

Bekey, G. A.↗

Models of man as a suboptimal predictor

Models of man making predictions of future states of discrete linear dynamic systems are considered. The task is forced-pace, but the pace is slow enough to eliminate the effects of reaction time and neuromuscular lag. The best of the several models considered includes the constraints of limited memory and observation noise.

Rouse, W. B.↗

Real-time control of the MIT vehicle emulation system

The MIT vehicle emulation system (VES) is an experimental facility designed to facilitate the study of controlling robots fixed to nonstationary bases. This includes assembly and repair manipulators attached to space vehicles, or to the space shuttle arm, as well as manipulators fixed to the bed of moving ground vehicles. Controlling manipulators under these conditions for endpoint force and positioning tasks requires both the development of new theory, and the development of a testbed for verifying theoretical results through experimentation. A description is presented of the technical details of the real-time controller for the second generation VES system.

Durfee, William K.↗

Extended Task Space Control for Robotic Manipulators

The invention is a method of operating a robot in successive sampling intervals to perform a task, the robot having joints and joint actuators with actuator control loops, by decomposing the task into behavior forces, accelerations, velocities and positions of plural behaviors to be exhibited by the robot simultaneously, computing actuator accelerations of the joint actuators for the current sampling interval from both behavior forces, accelerations velocities and positions of the current sampling interval and actuator velocities and positions of the previous sampling interval, computing actuator velocities and positions of the joint actuators for the current sampling interval from the actuator velocities and positions of the previous sampling interval, and, finally, controlling the actuators in accordance with the actuator accelerations, velocities and positions of the current sampling interval. The actuator accelerations, velocities and positions of the current sampling interval are stored for use during the next sampling interval.

Backes, Paul G.↗

Apollo 16 Press Kit

The Apollo 16 spacecraft is scheduled for launch on Apr. 16, 1972 from Complex 39A at the Kennedy Space Center, Florida by the Saturn V launch vehicle. Crewmen are mission commander John W. Young, command module pilot Thomas K. Mattingly II and lunar module pilot Charles M. Duke Jr. Objectives of the mission, to last up to 12 days, as outlined by NASA: to perform selenological inspection, survey and sampling of materials in a preselected region of Descartes using a lunar roving' vehicle; deploy and activate Apollo surface experiments; develop man's capability to work in the lunar environment; obtain photographs of candidate exploration sites; and toconduct inflight experiments and photographic tasks in lunar orbit. Following launch, the spacecraft will reach Earth Parking Orbit and remain in orbit for about two and one-half revolutions prior to Translunar Injection. Next, the Command and Service Module docks with the Lunar Module and the spacecraft "coasts" to the moon. In orbit around the moon, the Command and Service Module/Lunar Module combination will descend to within 50,000 feet of the lunar surface before undocking. The Lunar Module will continue to descend while the Command and Service Module returns to an orbit approximately 60 miles high. Stay time on the lunar surface is scheduled for approximately 73 hours. The ascent stage of the Lunar Module then lifts the astronauts back into lunar orbit where they will dock with the Command/Service Module. The Lunar Module is jettisoned and Transearth Injection follows. Just prior to reentry into the earth's atmosphere, the Service Module is jettisoned, and the astronauts in the Command Module splashdown in the Pacific Ocean. The target point for end-of-mission splashdown is at 05 degrees 0 minutes north latitude and 158 degrees 40 minutes west longitude or approximately 985 nautical miles south of Honolulu, Hawaii. Splashdown is scheduled for Apr. 28, 1972 at 10:30 a.m. Hawaiian Standard Time (2:30 p.m. CST). Recovery forces for Apollo 16, stationed in both the Atlantic and Pacific Oceans, will consist of three ships, nine aircraft and nearly 1,700 personnel. CTF-130 (Manned Spacecraft Recovery Force, Pacific) forces will be stationed south of Hawaii. Three ships, eight helicopters and three Air Force HC-130H aircraft, and nearly 1,100 personnel, will take part. Task Force 140 (Manned Spacecraft Recovery Force, Atlantic), comprising one ship, six HC-130H aircraft, three helicopters and approximately 300 personnel, will be positioned for possible launch abort operations. Two ships in the Atlantic will also be used for acoustical testing. Other forces, primarily aircraft and personnel of the Air Force Aerospace Rescue and Recovery Service will be on alert around the world for contingency recovery support.

Source record↗

Dual redundant arm configuration optimization with task-oriented dual arm manipulability

It is shown that the required motion and force trajectories of a given task can be abstracted by a series of desired manipulability ellipsoids, and that a task-oriented dual-arm manipulability measure (TODAMM) can be mathematically defined by quantifying how the manipulability of one arm affects the other and measuring the geometrical closeness between the desired and the actual manipulability ellipsoids. TODAMM can be used in the optimization of dual-arm joint configurations. The task-oriented manipulability measure developed can also be used in the joint configuration optimization of a single arm, providing efficient joint configurations in terms of joint motions and joint torques for the required Cartesian motions and static forces. The dual-arm joint configuration optimization based on TODAMM can be applied to a variety of tasks which require dual-arm cooperation.

Lee, Sukhan↗

Air forces on airfoils moving faster than sound

We are undertaking the task of computing the air forces on a slightly cambered airfoil in the absence of friction and with an infinite aspect ratio. We also assume in advance that the leading edge is very sharp and that its tangent lies in the direction of motion.

AIRFOILS, HIGH SPEED↗

Evaluation of force-torque displays for use with space station telerobotic activities

Recent experiments which addressed Space Station remote manipulation tasks found that tactile force feedback (reflecting forces and torques encountered at the end-effector through the manipulator hand controller) does not improve performance significantly. Subjective response from astronaut and non-astronaut test subjects indicated that force information, provided visually, could be useful. No research exists which specifically investigates methods of presenting force-torque information visually. This experiment was designed to evaluate seven different visual force-torque displays which were found in an informal telephone survey. The displays were prototyped in the HyperCard programming environment. In a within-subjects experiment, 14 subjects nullified forces and torques presented statically, using response buttons located at the bottom of the screen. Dependent measures included questionnaire data, errors, and response time. Subjective data generally demonstrate that subjects rated variations of pseudo-perspective displays consistently better than bar graph and digital displays. Subjects commented that the bar graph and digital displays could be used, but were not compatible with using hand controllers. Quantitative data show similar trends to the subjective data, except that the bar graph and digital displays both provided good performance, perhaps do to the mapping of response buttons to display elements. Results indicate that for this set of displays, the pseudo-perspective displays generally represent a more intuitive format for presenting force-torque information.

Hendrich, Robert C.↗

Problems and research issues associated with the hybrid control of force and displacement

The hybrid control of force and position is basic to the science of robotics but is only poorly understood. Before much progress can be made in robotics, this problem needs to be solved in a robust manner. However, the use of hybrid control implies the existence of a model of the environment, not an exact model (as the function of hybrid control is to accommodate these errors), but a model appropriate for planning and reasoning. The monitored forces in position control are interpreted in terms of a model of the task as are the monitored displacements in force control. The reaction forces of the task of writing are far different from those of hammering. The programming of actions in such a modeled world becomes more complicated and systems of task level programming need to be developed. Sensor based robotics, of which force sensing is the most basic, implies an entirely new level of technology. Indeed, robot force sensors, no matter how compliant they may be, must be protected from accidental collisions. This implies other sensors to monitor task execution and again the use of a world model. This new level of technology is the task level, in which task actions are specified, not the actions of individual sensors and manipulators.

Paul, R. P.↗

Baseline tests of an autonomous telerobotic system for assembly of space truss structures

Several proposed space missions include precision reflectors that are larger in diameter than any current or proposed launch vehicle. Most of these reflectors will require a truss structure to accurately position the reflector panels and these reflectors will likely require assembly in orbit. A research program has been conducted at the NASA Langley Research Center to develop the technology required for the robotic assembly of truss structures. The focus of this research has been on hardware concepts, computer software control systems, and operator interfaces necessary to perform supervised autonomous assembly. A special facility was developed and four assembly and disassembly tests of a 102-strut tetrahedral truss have been conducted. The test procedures were developed around traditional 'pick-and-place' robotic techniques that rely on positioning repeatability for successful operation. The data from two of the four tests were evaluated and are presented in this report. All operations in the tests were controlled by predefined sequences stored in a command file, and the operator intervened only when the system paused because of the failure of an actuator command. The tests were successful in identifying potential pitfalls in a telerobotic system, many of which would not have been readily anticipated or incurred through simulation studies. Addressing the total integrated task, instead of bench testing the component parts, forced all aspects of the task to be evaluated. Although the test results indicate that additional developments should be pursued, no problems were encountered that would preclude automated assembly in space as a viable construction method.

Rhodes, Marvin D.↗

A force-controllable macro-micro manipulator and its application to medical robots

This paper describes an 8-degrees-of-freedom macro-micro robot. This robot is capable of performing tasks that require accurate force control, such as polishing, finishing, grinding, deburring, and cleaning. The design of the macro-micro mechanism, the control algorithms, and the hardware/software implementation of the algorithms are described in this paper. Initial experimental results are reported. In addition, this paper includes a discussion of medical surgery and the role that force control may play. We introduce a new class of robotic systems collectively called Robotic Enhancement Technology (RET). RET systems introduce the combination of robotic manipulation with human control to perform manipulation tasks beyond the individual capability of either human or machine. The RET class of robotic systems offers new challenges in mechanism design, control-law development, and man/machine interface design. We believe force-controllable mechanisms such as the macro-micro structure we have developed are a necessary part of RET. Work in progress in the area of RET systems and their application to minimally invasive surgery is presented, along with future research directions.

Marzwell, Neville I.↗