A Qualitative Physics Based on Confluences

To a large extent the robotics and the newer virtual reality (VR) research communities have been working in isolation. This article reviews three areas where integration of the two technologies can be beneficial. First, we consider VR-enhanced CAD design, robot programming, and plant layout simulation. Subsequently, we discuss how VR is being used in supervisory teleoperation, for single operator-single robot systems, single operator multiplexed to several slave robots, and collaborative control of a single robot by multiple operators. Here VR can help overcome problems related to poor visual feedback as well as system instabilities due to time delays. Finally, we show how robotics can be beneficial to VR in general, since robots can serve as force feedback interfaces to the simulation. Newer back-drivable manipulators offer increased safety for the user that closely interacts with the robot. The synergy between the fields of robotics and virtual reality is expected to grow in years to come.

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Invited review: the synergy between virtual reality and robotics

A new robotic crawler is being developed for inspection of large aircraft external surfaces. The multifunction automated crawling system (MACS) has been designed and fabricated to carry miniature instrumentation to perform a wide variety of tasks while being attached to an aircraft's surface. The immediate application of MACS is inspection of the exterior of large military aircraft such as the C-5. Various inspection payload modules could be incorporated onto the MACS crawler to perform the desired inspections. MACS employs ultrasonic motors for mobility and suction cups for surface adherence. MACS has two legs for linear motion and a rotation element for turning, enabling any simultaneous combination of motion from linear to rotation about a central axis.

The multifunction automated crawling system (MACS)

The Web Interface for Telescience (WITS) is an Internet-based tool that the Mars Pathfinder mission used for both mission operations at JPL and public outreach. WITS enables the viewing of downlinked images and results in various ways, terrain feature measurement and annotation, and planning of daily mission activities. WITS is written in the Java language and is accessible by mission scientists and the general public via a web browser. The public can use WITS to plan and simulate their own rover missions. WITS will also be used in the 1998 lander and 2001, 2003, and 2005 rover missions to Mars.

Mars pathfinder mission Internet-based operations using WITS

Motions of mobile robots need to be optimized to minimize their energy consumption to ensure long periods of continuous operations. Shortest paths do not always guarantee the minimum energy consumption of mobile robots. Moreover, they are not always feasible due to climbing constraints of mobile robots, especially on steep terrains. We utilize a heuristic search algorithm to find energy-optimal paths on hilly terrains using an established energy-cost model for mobile robots. The terrains are represented using grid-based elevation maps. Similar to A*-like heuristic search algorithms, the energy-cost of traversing through a given location of the map depends on a heuristic energy-cost estimation from that particular location to the goal. Using zigzag-like path patterns, the proposed heuristic function can estimate heuristic energy-costs on steep terrains that cannot be estimated using traditional methods. We proved that the proposed heuristic energy-cost function is both admissible and consistent. Therefore, the proposed path planner can always find feasible energy-optimal paths on any given terrain without node revisits, provided that such paths exist. Results of tests on real-world terrain models presented in this paper demonstrate the promising computational performance of the proposed path planner in finding energy-efficient paths.

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A Constraint-Aware Heuristic Path Planner for Finding Energy-Efficient Paths on Uneven Terrains

The new task lines and motion guides approaches to telerobotics are described. Motion guides is a new paradigm for teleoperation of a robot where the path is teleoperated rather than the robot, and the robot is constrained to follow the path. Continuous commands to the robot are only one dimensional: forward, back, or halt along the motion guide. Task lines have subtasks attached to motion guides. The task lines and motion guides have been implemented in a virtual reality environment to enable task description and execution to be done in a natural virtual reality graphics environment rather than via direct interaction with a command program. Subtasks are represented in the virtual reality environment by icons attached to the motion guides. The combination of task lines and motion guides is valuable for ground control of Space Station robots, which is the initial application for this technology.

Task lines and motion guides

The new task lines and motion guides approaches to telerobotics are described. Motion guides is a new paradigm for teleoperation of a robot where the path is teleoperated rather than the robot, and the robot is constrained to follow the path. Continuous commands to the robot are only onedimensional: forward, back, or halt along the motion guide. Task lines have subtasks attached to motion guides. The task lines and motion guides have been implemented in a virtual reality environment to enable task description and execution in a natural, virtual reality graphics environment rather than via direct interaction with a command program. Subtasks are represented in the virtual reality environment by icons attached to the motion guides. The combination of task lines and motion guides is valuable for ground control of Space Station robots, which is the initial application for this technology.

Task Lines and Motion Guides

Planetary surface science operations performed by robotic space systems frequently require pointing cameras at various objects and moving a robotic arm end effector tool toward specific targets. Earlier NASA Mars Exploration Rovers did not have the ability to compute actual coordinates for given object coordinate frame names and had to be provided with explicit coordinates. Since it sometimes takes hours to more than a day to get final approval of certain calculated coordinates for command uplink via the Earth-based mission operations procedures, a highly desired enhancement for future rovers was to have the onboard automated capability to compute the coordinates for a given frame name. The Mars Science Laboratory (MSL) rover mission is the first to have a centralized coordinate transform database to maintain the knowledge of spatial relations. This onboard intelligence significantly simplifies communication and control between Earth-based human mission operators and the robotic rover on Mars by supporting higher level abstraction of commands using object and target names instead of coordinates. More specifically, the spatial relations of many object frames are represented hierarchically in a tree data structure, called the frame tree. Individual frame transforms are populated by their respective modules that have specific knowledge of the frames. Through this onboard centralized frame tree database, client modules can query transforms between any two frames and support spacecraft commands that use any frames maintained in the frame tree. Various operational examples in the MSL mission that have greatly benefitted from this onboard centralized frame tree database are presented.

Onboard centralized frame tree database for intelligent space operations of the Mars Science Laboratory Rover.

The telerobot interactive planning system (TIPS) has been developed to provide automated task planning and reasoning for satellite servicing in NASA's Jet Propulsion Laboratory telerobot testbed. The strategy taken in this development is that an interface between a partially autonomous system and external sources of knowledge is a feature which enables application of technology not yet fully autonomous. Interactive features, both between the operator and TIPS and among the reasoning engines within TIPS, result in a system which has greater robustness than the reasoning engines alone could provide.

Autonomy through interaction - The JPL telerobot interactive planning system

A qualitative reasoning planner for determining robot control parameters to drive manipulation actions has been developed, integrated into a telerobot system, and demonstrated for a match striking task. The planner consists of a qualitative reasoner and a numerical execution history which interact to jointly direct and narrow the search for reliable numerical control parameter values. The planner algorithm, implementation, and an execution example are described. The relationship to previous qualitative reasoning work is also discussed.

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Stephen F. Peters

Papers

Task lines and motion guides

Task Lines and Motion Guides

Onboard centralized frame tree database for intelligent space operations of the Mars Science Laboratory Rover.

Autonomy through interaction - The JPL telerobot interactive planning system

Planning robot control parameter values with qualitative reasoning