Mitch Pryor

A reusable software architecture for manual controller integration

This paper examines the commonalities of manual controllers used in robotics for teleoperation. These include devices ranging from simple joysticks to force-reflecting controllers. The similarities in functionality and behaviour of these controllers is further exploited to develop a reusable software architecture for manual controller interfacing. The development of this architecture is based on object-oriented design. The application of this design philosophy led to the development of a hierarchy of software components that are manual controller independent and also have a standardized interface. Reusability of these components is supported through generality and extensibility. The key design requirements for this architecture were: open-system, reusable, application independent, extensive error-handling and safety checking, applicability to real-time control and simulation, and reduction in program development time. This paper discusses the software analysis and design issues that were faced to meet the architecture requirements. Further, this architecture is demonstrated using four different manual controllers and a teleoperated dual-arm robotic manipulator.

Extended generalized impedance control for redundant manipulators

An impedance control method for redundant manipulators called an extended generalized impedance control is developed. It is based on an extended task space formulation and generalized impedance control. With generalized impedance control, the manipulators end-effector position and force tracking abilities can be balanced by properly adjusting impedance parameters. Null space motion is controlled by tracking a minimal parameterization of null space velocity. Redundancy is then exploited by specifying a desired null space velocity trajectory that optimizes a performance index. The control algorithm is implemented as part of OSCAR (Operational Software Components for Advanced Robotics), keeping with the generality concept. Therefore, it can be easily deployed with any serial manipulator. The effectiveness of the proposed controller is illustrated by computer simulations of a complex 10-DOF spatial manipulator performing a cutting task.

A software architecture for multi-criteria decision making for advanced robotics

Presents a framework that facilitates the development of multi-criteria decision-making software for redundant manipulator control. This software architecture is based on object-oriented design and it meets the requirements of generality, extensibility, computational efficiency, and reduction in program development time. Analysis, design, and implementation were the three steps in the development of this architecture. Analysis involved the study of the multi-criteria decision-making domain. This included the information flow between different criteria and also their fusion. The design phase involved extracting the commonalties of various criteria and the specification of abstractions that could best model these criteria. The application of this philosophy led to the development of an architecture that is robot independent, scaleable, supports standardized interfaces, and is applicable to real-time control and simulation. This architecture is demonstrated using a sample application for controlling a 10 DOF manipulator.

Drillstring Vibration Observation, Modeling and Prevention in the Oil and Gas Industry

As well designs become increasingly complicated, a complete understanding of drillstring vibrations is key to maximize drilling efficiency and reduce bit wear as well as prevent drillstring, tool, and borehole damage. This paper presents a review of the past fifty years of work on drillstring dynamics models and the proposed and accepted vibration mitigation applications within the drilling industry. Early modeling began with simplistic models in efforts to understand downhole processes. Once downhole sensors were deployed and the basic modes of vibration were understood, proprietary systems were developed and — only recently — successfully deployed to detect and mitigate the effects of certain undesired vibrational modes, specifically stick-slip torsional vibrations. Future systems and their effectiveness will depend on a refined understanding of the various modes of vibration and their interaction, as well as improved real-time downhole sensing techniques. Implementation of high-fidelity models to deduce and correct the downhole drillstring state will subsequently improve the operational drilling efficiency.Copyright

High-precision telerobot with human-centered variable perspective and scalable gestural interface

Telerobotics (i.e., remote-controlling robots) is highly attractive for tasks in potentially dangerous situations, e.g., search and rescue, space exploration, and handling hazardous materials. However, when telerobots are deployed to complete tasks, the human operator needs to develop task plan and figure out how to execute it using the available control interface. Inappropriate controls can lead to excessive cognitive load and long task completion times. If the human operator can interact with the robot in an intuitive way, he or she can focus more on the task. For that reason, we have designed a human-centered control interface that allows the operator to modify the user perspective, command via hand gestures and natural language, and scale human input motion to any suitable range on the robot. The interface consists of a Leap Motion Controller for hand tracking, microphone for speech detection, and a simple turn knob for varying the scaling factor between the human and robot motions. The teleoperator software utilizes the Robot Operating System (ROS) which enables open-source development and hardware agnosticism. In this paper we demonstrate the feasibility of the proposed system by executing a high-precision task of threading a needle. Furthermore, we present results from a usability study in where people were asked to complete high-precision tasks with both the developed human-centered gestural control input and a conventional functionality-centered drag-and-drop interface.

An Extended Kalman Filter for Collision Detection During Manipulator Contact Tasks

The development of control strategies that allow stiff industrial robots to operate safely in unstructured environments is a significant challenge. This paper integrates two strategies that improve safety for industrial manipulators in uncertain conditions. First, software compliance in the task space is implemented using force feedback. End-effector compliance is vital for many tasks, such as interacting with humans or manipulating uncertain payloads. Beyond compliance, a collision detection algorithm detects collisions based on joint torque deviation from a dynamic model. Collisions can be detected at any point along the manipulator via loading or impulse anomalies. Joint torque data is typically noisy, and the accuracy of the robot dynamic model is limited, so an Extended Kalman Filter (EKF) was developed to improve the torque estimates. Experiments and demonstrations were performed using a commercially available 7DOF industrial robot. The EKF improved collision detection during unplanned contact tasks, and the method described here is hardware agnostic and extensible.Copyright

Automating High-Precision X-Ray and Neutron Imaging Applications With Robotics

Los Alamos National Laboratory and the University of Texas at Austin recently implemented a robotically controlled nondestructive testing (NDT) system for X-ray and neutron imaging. This system is intended to address the need for accurate measurements for a variety of parts and, be able to track measurement geometry at every imaging location, and is designed for high-throughput applications. This system was deployed in a beam port at a nuclear research reactor and in an operational inspection X-ray bay. The nuclear research reactor system consisted of a precision industrial seven-axis robot, 1.1-MW TRIGA research reactor, and a scintillator-mirror-camera-based imaging system. The X-ray bay system incorporated the same robot, a 225-keV microfocus X-ray source, and a custom flat panel digital detector. The robotic positioning arm is programmable and allows imaging in multiple configurations, including planar, cylindrical, as well as other user defined geometries that provide enhanced engineering evaluation capability. The imaging acquisition device is coupled with the robot for automated image acquisition. The robot can achieve target positional repeatability within 17

Semiautonomous dual-arm mobile manipulator system with intuitive supervisory user interfaces

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Stabilization of nonlinear systems by switched Lyapunov function

in the 3-D space. Flexible automation with nondestructive imaging saves costs, reduces dosage, adds imaging techniques, and achieves better quality results in less time. Specifics regarding the robotic system and imaging acquisition and evaluation processes are presented. This paper reviews the comprehensive testing and system evaluation to affirm the feasibility of robotic NDT, presents the system configuration, and reviews results for both X-ray and neutron radiography imaging applications.Note to Practitioners—While looking for ways to improve throughput and increase efficiency in nondestructive imaging applications, the NonDestructive Testing and Evaluation Group at the Los Alamos National Laboratory decided to take a look at automation opportunities. Digital radiography and computed tomography are time-consuming processes, making them ideal candidates for robotic solutions. Radiography applications often require several images to be acquired from different angles and a lot of time they have to be very precise so that the feature of interest is identifiable and the resulting image meets the client’s requirements. With the robot acting as the motion control system, the imaged part can be placed directly in the beam path and oriented in six degrees of freedom. The robot can achieve significantly higher levels of precision than a human and has the ability to adjust the part while the source is active. The system also reduces levels of radiation our staff is exposed to, as the robot is setup to handle radioactive and hazardous parts. Not only does the robot move parts more precisely and with higher resolution than humans, but it also adds additional flexibility in the type and nature of images that the lab can produce. Future work will involve using this system for advanced automated scans such as achieving evenly spaced views around a sphere autonomously, since this system has not yet been used for more advanced scans beyond helical scanning. A tightly linked feedback loop between the robot and imaging code in which the imaging code would autonomously communicate to the robot what additional views are needed to reduce imaging error can also be explored.

A Black Box Model for Estimating Joint Torque in an Industrial Serial Manipulator

This paper presents the VaultBot dual-arm mobile manipulator and its integration with Robot Operating System, MoveIt!, and RViz, and thus demonstrate how two chronic issues with similar systems were addressed: overly complex integration and user control. Multiple levels of semi-autonomous control were developed for the base, manipulator(s), and coordinated motions involving both. Lower levels of autonomy are always available to increase operator comfort. In order to combat cognitive load increases from context switching the control methods take a human-centered approach by automatically adjusting perspective to keep tasks visualized relative to the operator. Sensor data is fused into a single window alongside the current robot state. These approaches are considered highly intuitive and can be used as effectively as socially well-established mouse-based interactive markers for teleoperation in even high-precision tasks.