Marsette A. Vona

Shady: Robust Truss Climbing with Mechanical Compliances

Many large terrestrial structures—towers, bridges, construction scaffolds—are sparse assemblies of rigid bars connected together at structural nodes. This is also true of many in-space structures such as antennae, solar panel supports, and space-station members. A long-term application of truss climbing robots is automated assembly, repair, and inspection of such truss-like structures: one or more climbing robots could grip the bars and locomote about the truss, conveying sensors, tools, or construction materials. The robot could then either carry out the desired task on its own or cooperate with a human [1,7].

Hierarchical control for self-assembling mobile trusses with passive and active links

This paper explores the space of active modular trusses, ranging from a passive truss with one independent active climbing module to fully self-reconfiguring dynamically controllable trusses comprised of active modules and passive struts. We describe a hardware design for truss climbing and present hierarchical algorithms for controlling hyper-redundant modular trusses

Lessons Learned from All-Terrain Hex-Limbed Extra-Terrestrial Explorer Robot Field Test Operations at Moses Lake Sand Dunes, Washington

The Jet Propulsion Laboratory (JPL) is developing the All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) as part of NASA’s Exploration Systems Mission Directorate, Exploration Technology Development Program (ETDP). The program develops technologies for surface mobility and equipment handling, human-system interaction, and lunar surface system repair, and constructs dexterous robots and autonomous rovers that can drive over rough terrain and help crew explore, assemble, and maintain a lunar outpost. ETDP sponsors a series of field tests at lunar analog test sites where prototype robots can operate in ways that simulate lunar surface conditions. In this paper, we describe the lessons learned about ATHLETE operations at the most recent lunar analog field test in June 2008 at Moses Lake Sand Dunes, Washington. The Moses Lake field test was structured as a series of “acts” which correspond to unpiloted and piloted missions to the lunar surface in the 2019 to 2022 timeframe. The field test took place over a period of two weeks and involved several robots from various NASA field centers, including the Chariot lunar truck from Johnson Space Center, the K10 planetary rover from Ames Research Center, and ATHLETE from JPL. Lessons learned from the Moses Lake field test will be incorporated into the evolving design of the ATHLETE operations system, and will be tested at subsequent field trials.

Voronoi Toolpaths for PCB Mechanical Etch: Simple and Intuitive Algorithms with the 3D GPU

We describe VIsolate (Voronoi Isolate), a system which performs geometric computations associated with toolpath planning for mechanical etch (also called isolation routing) of printed-circuit boards, including the computation of a novel Voronoi-based toolpath with some advantages over the current industry practice. We highlight how we use the 3D Graphics Processing Unit (GPU) to implement simple, intuitive algorithms in VIsolate, including polygon overlap detection, 2D offset, and constrained generalized Voronoi diagram computation, building on a method from [1]. Thus, this work also illustrates how we can employ the GPU as a rudimentary ‘ mind’s eye’ for the machine, allowing us to rapidly implement visually-intuitive geometric algorithms.

Hierarchical Decomposition and Kinematic Abstraction with Virtual Articulations

We introduce a novel hierarchical model to partition a kinematic system into a set of nested subsystems. This is framed in a mixed real/virtual context, where some joints and links may exist in simulation only. We then use this capability to build a precise form of kinematic abstraction, where a potentially complex subsystem can be virtually replaced by a simpler “interface.” Hierarchy and abstraction are interesting because they can help manage complexity in large (100+ DoF) mixed real/virtual mechanisms. We prove that checking if an abstraction is proper is PSPACE-hard, but show that even improper abstractions can be useful. Topological algorithms are presented for decomposing a hierarchical or abstracted kinematic system into subsystems that can be treated in isolation, thus speeding up kinematic computations. We demonstrate on a simulation of a hybrid serial/parallel modular tower with over 100 revolute joints.

Operating High-DoF Articulated Robots Using Virtual Links and Joints

This chapter presents the theory, implementation, and application of a novel operations system for articulated robots with large numbers (10s to 100s) of degrees-of-freedom (DoF), based on virtual articulations and kinematic abstractions. Such robots are attractive in some applications, including space exploration, due to their application flexibility. But operating them can be challenging: they are capable of many different kinds of motion, but often this requires coordination of many joints. Prior methods exist for specifying motions at both low and high-levels of detail; the new methods fill a gap in the middle by allowing the operator to be as detailed as desired. The presentation is fully general and can be directly applied across a broad class of 3D articulated robots.

A graphical operations interface for modular surface systems

This paper presents the design and implementation of algorithms for a new graphical operations interface system specifically adapted to operating modular reconfigurable articulated surface systems. Geometric models of heterogeneous robot modules may be connected and disconnected in this interface via drag-and-drop interaction. The resulting assemblies may further be kinematically operated through onscreen direct manipulation. The system maintains a reduced coordinate kinematic model for stability, accuracy, and performance. Key algorithms are presented to evolve this model as the user changes the assembled module topology. Though the presented algorithms are generic, application examples are given primarily for a simulation of NASA/JPLs reconfigurable TriATHLETE system for Lunar exploration. A second application example with a modular robot from the research literature is also included as a demonstration.

Using Virtual Articulations to Operate High-DoF Inspection and Manipulation Motions

We have developed a new operator interface system for high-DoF articulated robots based on the idea of allowing the operator to extend the robot’s actual kinematics with virtual articulations. These virtual links and joints can model both primary task DoF and constraints on whole-robot coordinated motion. Unlike other methods, our approach can be applied to robots and tasks of arbitrary kinematic topology, and allows specifying motion with a scalable level of detail. We present hardware results where NASA/JPL’s All-Terrain Hex-Legged Extra-Terrestrial Explorer (ATHLETE) executes previously challenging inspection and manipulation motions involving coordinated motion of all 36 of the robot’s joints.