Jonathan M. Cameron

Multiagent Mission Specification and Execution

Specifying a reactive behavioral configuration for use by a multiagent team requires both a careful choice of the behavior set and the creation of a temporal chain of behaviors which executes the mission. This difficult task is simplified by applying an object-oriented approach to the design of the mission using a construction called an assemblage and a methodology called temporal sequencing. The assemblage construct allows building high level primitives which provide abstractions for the designer. Assemblages consist of groups of basic behaviors and coordination mechanisms that allow the group to be treated as a new coherent behavior. Upon instantiation, the assemblage is parameterized based on the specific mission requirements. Assemblages can be re-parameterized and used in other states within a mission or archived as high level primitives for use in subsequent projects. Temporal sequencing partitions the mission into discrete operating states with perceptual triggers causing transitions between those states. Several smaller independent configurations (assemblages) can then be created which each implement one state. The Societal Agent theory is presented as a basis for constructions of this form. The Configuration Description Language (CDL) is developed to capture the recursive composition of configurations in an architecture- and robot-independent fashion. The MissionLab system, an implementation based on CDL, supports the graphical construction of configurations using a visual editor. Various multiagent missions are demonstrated in simulation and on our Denning robots using these tools.

Reactive control for mobile manipulation

Research for executing large-scale motions of mobile manipulators is described. Mobile manipulators are mobile bases with an attached arm which function in an integrated manner. Motivation is given for moving the arm while the base is moving. This paper applies reactive control concepts to achieve this type of motion. Tools for modeling integrated arm-vehicle kinematics and dynamics are discussed. Kinematics- and dynamics-based concepts are combined with reactive control approaches in order to move toward a practical level of complexity and performance. Simulation results are presented.<<ETX>>

Modeling mechanisms with nonholonomic joints using the Boltzmann-Hamel equations

This article describes a new technique for deriving dynamic equations of motion for serial chain and tree topology mech anisms with common nonholonomic constraints. For each type of nonholonomic constraint, the Boltzmann-Hamel equations produce a concise set of dynamic equations. These equations are similar to Lagranges equations and can be applied to mechanisms that incorporate that type of constraint. A small library of these equations can be used to efficiently analyze many different types of mechanisms. Nonholonomic constraints are usually included in a La grangian setting by adding Lagrange multipliers and then eliminating them from the final set of equations. The ap proach described in this article automatically produces a minimum set of equations of motion that do not include La grange multipliers.

Specification and execution of multiagent missions

Specifying a multiagent behavioral configuration requires both a careful choice of the behavior set and creation of a temporal chain executing the mission using those behaviors. This difficult task is simplified by applying an object-oriented approach to the design using a methodology called temporal sequencing to partition the mission into discrete operating states and enumerate the perceptual triggers causing transitions between those states. Several smaller independent configurations (assemblages) can then be created, each implementing one distinct operating state. Each assemblage consists of a collection of behaviors and a suitable coordination mechanism which causes the group to act as a single, coherent, behavior. The missions are specified in a structured user-friendly language targeted for military-style scout missions. Various multiagent missions have been demonstrated in simulation and results are shown using our Denning mobile robots.

Survival of falling robots

As mobile robots are used in more uncertain and dangerous environments, it will become important to design them so that they can survive falls. In this paper, we examine a number of mechanisms and strategies that animals use to withstand these potentially catastrophic events and extend them to the design of robots. A brief survey of several aspects of how common cats survive falls provides an understanding of the issues involved in preventing traumatic injury during a falling event. After outlining situations in which robots might fall, a number of factors affecting their survival are described. From this background, several robot design guidelines are derived. These include recommendations for the physical structure of the robot as well as requirements for the robot control architecture. A control architecture is proposed based on reactive control techniques and action-oriented perception that is geared to support this form of survival behavior.

Qualitative spatial understanding and reactive control for autonomous robots

The work involves integrating two paradigms for robust robotic systems: reactive control and qualitative spatial reasoning. The objective is to produce autonomous robots which can freely wander about, without harming themselves, while creating and improving maps of their environment which can then be used for navigation and planning. Reactive control provides a basic framework for developing and organizing behaviors for autonomous exploration and navigation. Qualitative spatial understanding provides an underlying representation and learning mechanism which will let the robot form spatial memories without requiring complicated object recognition or precise determination of environmental locations. The overall goal is to advance both areas of study for robotics as pertains to planning, learning, and real-time control.<<ETX>>

Autonomy architecture for aerobot exploration of Saturnian moon Titan

The Huygens probe arrived at Saturns moon, Titan, January 14,2005, unveiling a world that is radically different from any other in the solar system. The data obtained, complemented by continuing observations from the Cassini spacecraft, show methane lakes, river channels and drainage basins, sand dunes, cryovolcanos and sierras. This has led to an enormous scientific interest in a follow-up mission to Titan, using a robotic lighter-than-air vehicle (or aerobot). Aerobots have modest power requirements, can fly missions with extended durations, and have very long distance traverse capabilities. They can execute regional surveys, transport and deploy scientific instruments and in-situ laboratory facilities over vast distances, and also provide surface sampling at strategic science sites. This describes our progress in the development of the autonomy technologies that will be required for exploration of Titan. We provide an overview of the autonomy architecture and some of its key components. We also show results obtained from autonomous flight tests conducted in the Mojave Desert.

An Autonomy Architecture for Aerobot Exploration of the Saturnian Moon Titan

The Huygens probe arrived at Saturns moon Titan on January 14, 2005, unveiling a world that is radically different from any other in the Solar system. The data obtained, complemented by continuing observations from the Cassini spacecraft, show methane lakes, river channels and drainage basins, sand dunes, cryovolcanos and sierras. This has lead to an enormous scientific interest in a follow-up mission to Titan, using a robotic lighter-than-air vehicle (or aerobot). Aerobots have modest power requirements, can fly missions with extended durations, and have very long distance traverse capabilities. They can execute regional surveys, transport and deploy scientific instruments and in-situ laboratory facilities over vast distances, and also provide surface sampling at strategic science sites. This paper describes our progress in the development of the autonomy technologies that will be required for exploration of Titan. We provide an overview of the autonomy architecture and some of its key components. We also show results obtained from autonomous flight tests conducted in the Mojave desert.

Venus Aerobot Multisonde Mission

Robotic exploration of Venus presents many challenges because of the thick atmosphere and the high surface temperatures. The Venus Aerobot Multisonde mission concept addresses these challenges by using a robotic balloon or aerobot to deploy a number of short lifetime probes or sondes to acquire images of the surface. A Venus aerobot is not only a good platform for precision deployment of sondes but is very effective at recovering high rate data. This paper describes the Venus Aerobot Multisonde concept and discusses a proposal to NASAs Discovery program using the concept for a Venus Exploration of Volcanoes and Atmosphere (VEVA). The status of the balloon deployment and inflation, balloon envelope, communications, thermal control and sonde deployment technologies are also reviewed.

Modeling, simulation, and control of parachute/balloon flight systems for Mars Exploration

In this paper, we report some models devel- oped for analyzing Parachute/Balloon-assisted deployment of sensor packages within the Mars Aerobot Validation Pro- gram (MABVAP) at JPL. Two different scenarios are de- scribed: pointing dynamics and control of an articulated payload mounted on a superpressure balloon-supported gon- dola, and the dynamics of various flight train configurations with parachute and superpressure balloons in different ge- ometries and oscillatory regimes originated upon deploy- ment. These scenarios have been motivated by the need to predict and validate flight-train stability behavior upon deployment before and after tests have been made.