Fred J. Oppel

Decentralized control of a collective of autonomous robotic vehicles

In this paper, the performance of a group of autonomous vehicles tracking a prescribed goal is analyzed. The vehicles are considered to be ground-based unmanned robots acting as a group to maintain an unbroken communication network in a building or some other region. Vehicle interactions are modeled as a chain of interconnected systems. The stability of the entire collective as well as individual vehicles is studied using largescale systems theory. Stability can be controlled via two key parameters: vehicle speed constant (maximum vehicle speed times sample time) and vehicle interaction gain. In addition to the stability analysis, simulation of a group of vehicles in a building with walls, doors, and other obstacles is studied with respect to maintaining a communication network among the vehicles at all times.

The Umbra Simulation Framework

Umbra is a new Sandia-developed modeling and simulation framework. The Umbra framework allows users to quickly build models and simulations for intelligent system development, analysis, experimentation, and control and supports tradeoff analyses of complex robotic systems, device, and component concepts. Umbra links together heterogeneous collections of modeling tools. The models in Umbra include 3D geometry and physics models of robots, devices and their environments. Model components can be built with varying levels of fidelity and readily switched to allow models built with low fidelity for conceptual analysis to be gradually converted to high fidelity models for later phase detailed analysis. Within control environments, the models can be readily replaced with actual control elements. This paper describes Umbra at a functional level and describes issues that Sandia uses Umbra to address.

The Umbra simulation framework as applied to building HLA federates

Sandias Umbra modular simulation framework was designed to enable the modeling of robots for manufacturing, military, and security system concept evaluation. Umbra generalizes data-flow-based simulation to enable modeling of heterogeneous interaction phenomena via a multiple worlds abstraction. This and other features make Umbra particularly suitable for developing simulation federates. Umbras HLA interface library utilizes DMSOs HLA Run Time Infrastructure 1.3-Next Generation (RTI 1.3-NG) software library to federate Umbra-based models into HLA environments. Examples draw on a first application that provides component technologies for the US Army JPSDs Joint Virtual Battlespace (JVB) simulation environment for Objective Force concept analysis.

High Level Architecture (HLA) federation with Umbra and OPNET federates.

Network-centric systems that depend on mobile wireless ad hoc networks for their information exchange require detailed analysis to support their development. In many cases, this critical analysis is best provided with high-fidelity system simulations that include the effects of network architectures and protocols. In this research, we developed a high-fidelity system simulation capability using an HLA federation. The HLA federation, consisting of the Umbra system simulator and OPNET Modeler network simulator, provides a means for the system simulator to both affect, and be affected by, events in the network simulator. Advances are also made in increasing the fidelity of the wireless communication channel and reducing simulation run-time with a dead reckoning capability. A simulation experiment is included to demonstrate the developed modeling and simulation capability.

Umbra's High Level Architecture (HLA) Interface

This report describes Umbras High Level Architecture HLA library. This library serves as an interface to the Defense Simulation and Modeling Offices (DMSO) Run Time Infrastructure Next Generation Version 1.3 (RTI NG1.3) software library and enables Umbra-based models to be federated into HLA environments. The Umbra library was built to enable the modeling of robots for military and security system concept evaluation. A first application provides component technologies that ideally fit the US Army JPSDs Joint Virtual Battlespace (JVB) simulation framework for Objective Force concept analysis. In addition to describing the Umbra HLA library, the report describes general issues of integrating Umbra with RTI code and outlines ways of building models to support particular HLA simulation frameworks like the JVB.