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At least 1,405 records · Page 78

Synchronized computational architecture for generalized bilateral control of robot arms

A master six degree of freedom Force Reflecting Hand Controller (FRHC) is available at a master site where a received image displays, in essentially real time, a remote robotic manipulator which is being controlled in the corresponding six degree freedom by command signals which are transmitted to the remote site in accordance with the movement of the FRHC at the master site. Software is user-initiated at the master site in order to establish the basic system conditions, and then a physical movement of the FRHC in Cartesean space is reflected at the master site by six absolute numbers that are sensed, translated and computed as a difference signal relative to the earlier position. The change in position is then transmitted in that differential signal form over a high speed synchronized bilateral communication channel which simultaneously returns robot-sensed response information to the master site as forces applied to the FRHC so that the FRHC reflects the feel of what is taking place at the remote site. A system wide clock rate is selected at a sufficiently high rate that the operator at the master site experiences the Force Reflecting operation in real time.

Szakaly, Zoltan F.↗

Science strategy and rationale for robotic missions to Mars

The scientific rationale for robotic missions to Mars follows a strategy in which a global data set and general understanding of the planet proceeds to progressively greater detail about specific scientific questions and candidate landing sites. In particular, a global understanding of Mars will be obtained from the Mars Observer mission and the Network Mission. The Site Reconnaissance Orbiter and the Sample Return mission will allow extensive testing and reevaluation of the knowledge about Mars and potential landing sites. Finally, a number of Rovers will provide detailed information on trafficability, resource availability, habitability, and science potential of candidate landing sites. The robotic mission set will also identify important scientific questions that can be addressed at potential landing sites.

Golombek, Matthew↗

Robotic missions to Mars - Paving the way for humans

NASA is in the planning stages of a program leading to the human exploration of Mars. A critical element in that program is a set of robotic missions that will acquire information on the Martian environment and test critical functions (such as aerobraking) at the planet. This paper presents some history of Mars missions, as well as results of recent studies of the Mars robotic missions that are under consideration as part of the exploration program. These missions include: (1) global synoptic geochemical and climatological characterization from orbit (Mars Observer), (2) global network of small meteorological and seismic stations, (3) sample returns, (4) reconnaissance orbiters and (5) rovers.

Pivirotto, D. S.↗

Random field estimation approach to robot dynamics

The difference equations of Kalman filtering and smoothing recursively factor and invert the covariance of the output of a linear state-space system driven by a white-noise process. Here it is shown that similar recursive techniques factor and invert the inertia matrix of a multibody robot system. The random field models are based on the assumption that all of the inertial (D'Alembert) forces in the system are represented by a spatially distributed white-noise model. They are easier to describe than the models based on classical mechanics, which typically require extensive derivation and manipulation of equations of motion for complex mechanical systems. With the spatially random models, more primitive locally specified computations result in a global collective system behavior equivalent to that obtained with deterministic models. The primary goal of applying random field estimation is to provide a concise analytical foundation for solving robot control and motion planning problems.

Rodriguez, Guillermo↗

Acceleration and torque feedback for robotic control - Experimental results

Gross motion control of robotic manipulators typically requires significant on-line computations to compensate for nonlinear dynamics due to gravity, Coriolis, centripetal, and friction nonlinearities. One controller proposed by Luo and Saridis avoids these computations by feeding back joint acceleration and torque. This study implements the controller on a Puma 600 robotic manipulator. Joint acceleration measurement is obtained by measuring linear accelerations of each joint, and deriving a computationally efficient transformation from the linear measurements to the angular accelerations. Torque feedback is obtained by using the previous torque sent to the joints. The implementation has stability problems on the Puma 600 due to the extremely high gains inherent in the feedback structure. Since these high gains excite frequency modes in the Puma 600, the algorithm is modified to decrease the gain inherent in the feedback structure. The resulting compensator is stable and insensitive to high frequency unmodeled dynamics. Moreover, a second compensator is proposed which uses acceleration and torque feedback, but still allows nonlinear terms to be fed forward. Thus, by feeding the increment in the easily calculated gravity terms forward, improved responses are obtained. Both proposed compensators are implemented, and the real time results are compared to those obtained with the computed torque algorithm.

Mclnroy, John E.↗

Application of automation and robotics to lunar surface human exploration operations

Major results of a study applying automation and robotics to lunar surface base buildup and operations concepts are reported. The study developed a reference base scenario with specific goals, equipment concepts, robot concepts, activity schedules and buildup manifests. It examined crew roles, contingency cases and system reliability, and proposed a set of technologies appropriate and necessary for effective lunar operations. This paper refers readers to four companion papers for quantitative details where appropriate.

Woodcock, Gordon R.↗

A robotic return to the moon

The autonomous lunar precursor mission presently proposed for low cost manned revisits to the lunar surface, designated 'Lunar Oasis by Automation and Robotics', employs two self-similar robotic vehicles, and three experimental 'biovolumes' which are directly derived from the lunar landers that are initially entrusted with fulfilling mission hardware-delivery requirements. The two vehicles would support the experimental biovolumes by returning resources for use in physicochemical or biological processing. Delivered resources would be combined with those in situ to furnish reconfigured biovolumes with the capabilities for autonomous biological growth and wastes-reprocessing demonstrations.

Luttges, Marvin W.↗

A unified perspective on robot control - The energy Lyapunov function approach

A unified framework for the stability analysis of robot tracking control is presented. By using an energy-motivated Lyapunov function candidate, the closed-loop stability is shown for a large family of control laws sharing a common structure of proportional and derivative feedback and a model-based feedforward. The feedforward can be zero, partial or complete linearized dynamics, partial or complete nonlinear dynamics, or linearized or nonlinear dynamics with parameter adaptation. As result, the dichotomous approaches to the robot control problem based on the open-loop linearization and nonlinear Lyapunov analysis are both included in this treatment. Furthermore, quantitative estimates of the trade-offs between different schemes in terms of the tracking performance, steady state error, domain of convergence, realtime computation load and required a prior model information are derived.

Wen, John T.↗

Decentralized digital adaptive control of robot motion

A decentralized model reference adaptive scheme is developed for digital control of robot manipulators. The adaptation laws are derived using hyperstability theory, which guarantees asymptotic trajectory tracking despite gross robot parameter variations. The control scheme has a decentralized structure in the sense that each local controller receives only its joint angle measurement to produce its joint torque. The independent joint controllers have simple structures and can be programmed using a very simple and computationally fast algorithm. As a result, the scheme is suitable for real-time motion control.

Tarokh, M.↗

Nonlinear feedback method of robot control - A preliminary experimental study

The nonlinear feedback method of robot control has been experimentally implemented on two PUMA 560 robot arms. The feasibility of the proposed controller, which was shown viable through simulation results earlier, is stressed. The servomechanism operates in task space, and the nonlinear feedback takes care of the necessary transformations to compute the necessary joint currents. A discussion is presented of the implementation with details of the experiments performed. The performance of the controller is encouraging but was limited to 100-Hz sampling frequency and to derived velocity information at the time of the experimentation. The setup of the lab, the software aspects, results, and the control hardware architecture that has recently been implemented are discussed.

Tarn, T. J.↗

Autonomous robot using infrared thermal camera to discriminate objects in outdoor scene

A complete autonomous legged robot is beig designed at Carnegie Mellon University to perform planetary exploration without human supervision. This robot must traverse unknown and geographically diverse areas in order to collect samples of materials. This paper describes how thermal imaging can be used to identify materials in order to find good footfall positions and collection sites of material. First, a model developed for determining the temperature of materials in an outdoor scene is presented. By applying this model, it is shown that it is possible to determine a physical characteristic of the material: thermal inertia. Second, experimental results are described that consist in recording thermal images of an outdoor scene constituted with sand and rock. Third, results and limitations of applying the model to experimental images are analyzed. Finally, the paper analyzes how basic segmentation algorithms can be combined with the thermal inertia segmentation in order to improve the discrimination of different kinds of materials.

Caillas, C.↗

Simulation of cooperating robot manipulators on a mobile platform

The dynamic equations of motion are presented for two or more cooperating manipulators on a freely moving mobile platform. The system of cooperating robot manipulators forms a closed kinematic chain where the force of interaction must be included in the formulation of robot and platform dynamics. The formulation includes the full dynamic interactions from arms to platform and arm tip to arm tip, and the possible translation and rotation of the platform. The equations of motion are shown to be identical in structure to the fixed-platform cooperative manipulator dynamics. The number of DOFs of the system is sufficiently large to make recursive dynamic calculation methods potentially more efficient than closed-form solutions. A complete simulation with two 6-DOF manipulators of a free-floating platform is presented along a with a multiple-arm controller to position the common load.

Murphy, Stephen H.↗

More About Architecture For Intelligent Robotic Control

Boolean neural networks proposed to implement part of intermediate level of hierarchical architecture of control system for artificially intelligent control of robot hand. Concept described in "Architecture for Intelligent Control of Robotic Tasks" (NPO-17871). Rule level of architecture implemented in two Boolean neural networks operated and updated in alternation. No explicit programming of network. Internal configuration not unique but, depends on initial state and history of previous adaptations. Accepts new rules sequentially presented by external controller.

Fiorini, Paolo↗

Algorithm For Simplified Robotic Tracking Of Weld Seams

Algorithm computes small cross-seam corrections to programmed path of welding robot. Intended for use with add-on vision system loosely coupled to robot, transmitting small amount of information about weld seam ahead of torch. Position of welding torch in reference frame of moving window estimated on basis of data on weld seam and speed of torch. Does not need data on position of torch, and does not transform data on seam to another reference frame.

Gutow, David A.↗

Orbital Welding Head Held By Robot

Orbital welding head positioned by robot controls motion and voltage of arc-welding torch mounted in head. New head encircles part at torch end, and held and manipulated by robot arm at opposite end. Entire welding operation automated. Useful for operations in hazardous environments.

Gangl, Kenneth J.↗

Robot Control Based On Spatial-Operator Algebra

Method for mathematical modeling and control of robotic manipulators based on spatial-operator algebra providing concise representation and simple, high-level theoretical frame-work for solution of kinematical and dynamical problems involving complicated temporal and spatial relationships. Recursive algorithms derived immediately from abstract spatial-operator expressions by inspection. Transition from abstract formulation through abstract solution to detailed implementation of specific algorithms to compute solution greatly simplified. Complicated dynamical problems like two cooperating robot arms solved more easily.

Rodriguez, Guillermo↗

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↗

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.↗