Reid L. Kress

Control of a teleoperator system with redundancy based on passivity conditions

Ways a stiffness controller can be used to control a teleoperator system with a redundant degree-of-freedom (DOF) slave manipulator and a dissimilar master are examined. No path planning is allowed because of the uncertainty of the environment and computational limitations. The proposed controller was implemented on the 7-DOF Center for Engineering Systems Advanced Research Manipulator slave manipulator with a 6-DOF Kraft master manipulator. The overall performance of this scheme and future directions are discussed.<<ETX>>

Internet-based robotics and remote systems in hazardous environments: review and projections

Robotic systems are used to perform maintenance functions in hazardous environments usually with the fundamental objective of reducing, or eliminating, human worker exposure to dangers. An obvious thought is how might Internet capabilities be used in such operations. This paper considers this general idea in terms of current research accomplishments, and the practical needs, constraints and concepts that are associated with the notion of using the Internet to reduce costs and enhance overall performance in robotic maintenance in hazardous environments.

Waste tank cleanup manipulator modeling and control

Waste tank cleanup is a current application area for robotics in the United States. As a result of tank access restrictions, designs for several current waste cleanup manipulator systems have long links with small cross-sections and variable lengths. In addition, as a result of anticipated payload capacity, these manipulator designs are hydraulically actuated. This paper takes two approaches to investigating the problem of the control of manipulators having variable-length flexible links and hydraulic actuators. First, a simulation of a hydraulically actuated, 2-DOF, polar (r-/spl Theta/), manipulator with one flexible link is used to illustrate the problem of applying controllers successfully developed for hydraulically actuated, fixed-length flexible manipulators to hydraulically-actuated, variable-length systems. Next, based upon the simulation results, simple controller modifications are proposed and are shown to work on a full-scale experimental test bed. Motion control of hydraulically actuated, variable-length flexible-link manipulators is the focus of this paper.

Simulation tools for robotic and teleoperated hazardous waste removal

The primary mission of Oak Ridge National Laboratory (ORNL) during World War II was the processing of pure plutonium metal in support of the Manhattan Project. Between 1943 and 1951, the Gunite and Associated Tanks (GAAT) at ORNL were built to collect, neutralize, and store the radioactive by-products. Currently, twelve gunite tanks and four stainless steel tanks are located on the ORNL complex. These tanks hold approximately 75,000 gal of radioactive sludge and solids and over 350,000 gal of liquid. Characterization studies of these tanks in 1994 indicated that the structural integrity of some of the tanks is questionable. Subsequently, there is presently an aggressive program directed towards the remediation and relocation of waste stored in the ORNL tanks. A number of factors complicate the remediation process. The material stored in these tanks ranges from liquid to sludge and solid and is composed of organic materials heavy metals, and radionuclides. The tanks, which range from 12 to 50 ft in diameter, are located below ground and in the middle of the ORNL complex. The only access to these ranks is through one of three access ports that are either 12 or 24 in. in diameter. These characteristics provide a daunting challenge: How can material be safely removed from such a confined structure? This paper describes the existing strategy and hardware presently used in the remediation process. This is followed by a description of an integrated hardware system model. This investigation has isolated a few key areas where further work is needed.

Modeling and control of a hydraulically actuated flexible-prismatic link robot

Most of the research related to flexible link manipulators to date has focused on single link, fixed length, single plane of vibration test beds. In addition, actuation has been predominantly based upon electromagnetic motors. Ironically, these elements are rarely found in the existing industrial long reach systems. This paper describes a new hydraulically actuated, long reach manipulator with a flexible prismatic link at Oak Ridge National Laboratory (ORNL). Focus is directed towards both modeling and control of hydraulic actuators as well as flexible links that have variable natural frequencies.

Hydraulically powered dissimilar teleoperated system controller design

Addresses two issues associated with the implementation of a hydraulically powered dissimilar master-slave teleoperated system. These issues are the overall system control architecture and the design of robust hydraulic servo controllers for the position control problem. Finally, a discussion of overall system performance on an actual teleoperated system is presented. (Schillings Titan II hydraulic manipulators are the slave manipulators and the master manipulators are from the Oak Ridge National Laboratory-developed Advanced Servo Manipulator).

Hydraulic manipulator design, analysis, and control at Oak Ridge National Laboratory

ABSTRACTIn the early developmental stages of robotics, hydraulics played an important role. Many of the early high-payload capacity manipulators were actuated by hydraulic cylinders and hydraulic rotary actuators. As the power-to-weight ratio of electric motors increased, they eventually came to be the preferred form of actuation for robotic manipulators because of the relative ease of operation, control, and maintenance for general cleanliness. Recently, however, task requirements have dictated that manipulator payload capacity increase to accommodate greater payloads, greater manipulator length, and larger environmental interaction forces. In order to successfully design, build, and deploy a new hydraulic manipulator (or subsystem), sophisticated modeling, analysis, and control experiments are usually needed. Oak Ridge National Laboratory (ORNL) has a history of projects that incorporate hydraulics technology, including mobile robots, teleoperated manipulators, and full-scale construction equipment. The...

Architecture for a human-robot symbiotic system

A description is given of a human-robot symbiont that is under development. The authors present an overview of the symbiotic system, motivating the architecture that has been developed. The architecture is a hierarchical structure that consists of several expert systems which reside above a robot control interface. This interface allows the manipulator to be operated in both a teleoperated and autonomous mode. All these processes coexist with the lower level of the hierarchy, which is a numerically intensive control algorithm. The architecture is implemented on five processors in a coarsely parallel system.<<ETX>>

Discrete event model of the remotely-operable TRU pipe connector

Chemical processes that involve hazardous materials may require remote handling for maintenance, repair, set up of new processes, or break down of existing processes. Remote handling dictates that pipe connections be made using a manipulator and various tools as well as specifically-designed fixtures or remotely accessible connectors. The TRU connector is a well-established, remotely-operable pipe connector. The connecting motion is accomplished via a screw-driven clamping device. Knowing the torque and power required to turn the screw and clamp or unclamp the connector is important for remote applications. An operator must be able to select the proper tool and manipulator to drive the screw and clamp or unclamp the connector. This paper describes an analytical model of the torque and power required to drive a TRU connector and presents the details of a discrete event model of a TRU connector in operation.

Inverse discrete event modeling for facility parameter estimation

Particular applications require analysts to estimate plant throughput from external observables via inverse modeling techniques. For example, auditors, law enforcement personnel, and financial planners might need to perform these types of analyses. Researchers at the SimCenter at The University of Tennessee Chattanooga have elected to model several simple basic production models as well as a fictional bicycle factory to do a preliminary investigation into the viability of implementing an inverse model using a discrete- event simulation software package. The fictional bicycle model will eventually include several simulation features such as a discrete event component, a flow portion, an agent based part, equation based power portion, and optimization. The results indicate that the approach is viable and that inverse modeling can be used to estimate internal activities. Future work will involve more detailed models with larger parameter sets.