Tightly Coupled Cooperation Among Independent Agents

Abstract

Coordination is defined as ”the harmonious functioning of parts for effective results” (Mish 1996). When applied to multiple robot systems, coordination is classified by one of two categories: collaboration or cooperation. Each component contributes to the harmonious functioning aspect of Coordination. Collaboration occurs when multiple robots engage in separate independent tasks to fulfill a higher goal. Collaboration is limited to situations where there is no requirement for synchronization on the tasks. An example of this is in distributed mapping: each robot’s progress on generating its portion of the map is unaffected by the progress of other robots. Cooperation, on the other hand, occurs when multiple robots engage in similar or identical tasks that are mutually dependent (coupled) in pursuit of a higher goal. These tasks require at least some degree of synchronization, and cooperative tasks fall on a spectrum that spans from loosely coupled to tightly coupled tasks. More tightly coupled tasks require a greater degree of synchronization. Cooperative box pushing is an example of a somewhat tightly coupled task, since the synchronization requirements are mostly limited to constraining the deviation from the intendended course. Cooperative lifting is a tightly coupled cooperative task because the robots must keep the item fairly level. This way, the robots avoid an uneven distribution of the weight and minimize the risk of damage to themselves and the item. With highly independent autonomous systems, collaboration and loosely coupled cooperation are readily achieved. This is because each individual task completion is seen as a fulfillment of a subgoal pertaining to the overall goal. Though the apparent progress of a loosely coupled cooperative tasking may vary temporally, delaying the deactivation of the task until it remains complete for a minimum time period can ensure successful completion. However, it is much more difficult to construct a system that can perform