Designing an Architecture for Adjustably Autonomous Robot Teams

Abstract

We are beginning a project to develop fundamental capabilities that enable multiple, distributed, heterogeneous robots to coordinate in achieving tasks that cannot be accomplished by the robots individually. The basic concept is to enable the individual robots to act fairly independently of one another, while still allowing for tight, precise coordination when necessary. The individual robots will be highly autonomous, yet will be able to synchronize their behaviors, negotiate with one another to perform tasks, and “advertise” their capabilities. This architectural approach differs from most other work in multi-robot systems, in which the robots are either loosely coupled agents, with little or no explicit coordination [1,4,5], or else are tightly coordinated by a highly centralized planning/execution system [3]. Our proposed architecture will support the ability of robots to react to changing and/or previously unknown conditions by replanning and negotiating with one another if the new plans conflict with previously planned-upon cooperative behaviors. The resulting capability will make it possible for teams of robots to undertake complex coordinated tasks, such as assembling large structures, that are beyond the capabilities of any one of the robots individually. Emphasis will be placed on the reliability of the worksystem to monitor and deal with unexpected situations, and flexibility to dynamically reconfigure as situations change and/or new robots join the team.

A main technical challenge of the project is to develop an architectural framework that permits a high degree of autonomy for each individual robot, while providing a coordination structure that enables the group to act as a unified team. Our approach is to extend current state-of-the-art hierarchical, layered robot architectures being developed at NASA JSC (3T) [2] and CMU (TCA) [6] to support distributed, coordinated operations. Our proposed architecture is highly compatible with these single-agent robot architectures, and will extend them to enable multiple robots to handle complex tasks that require a fair degree of coordination and autonomy.

As second technical challenge is to use distributed techniques to provide coordinated control of complex, coupled dynamic systems. For example, a mobile manipulator may have many degrees of freedom and controlling them all from a single controller would be complicated and computationally expensive. However, by breaking the complicated control problem into several simpler control problems and then having the simpler control problems coordinate and cooperate with each other to achieve a task we can reduce complexity and computational requirements. This approach will require the architectural support described in the previous paragraph.