Information-Cost-Reward Framework

 

Overview


Kilobots communicating

The Information-Cost-Reward (ICR) framework represents a novel approach to understanding robot swarms that perform foraging. During foraging, robots need to search for worksites in an unknown environment and either perform work on them (for example, in the case of area surveillance), or collect items from the worksites and bring them to a designated location (for example, in resource collection applications). The ICR framework relates the way in which robots obtain and share information about where work needs to be done to the swarm’s ability to use that information to perform work efficiently, given a particular task and environment.

What is it about?

A graphical representation of the ICR framework A swarm is understood as a single entity that acts on its environment in order to perform some work and get reward. Reward, placed in worksites, is dispersed in the environment in a certain way, and there is a certain probability, p(W), associated with a worksite being located at a given place. Scouts play the role of the swarm’s sensors. They find new information about where worksites are, decreasing the amount of uncertainty cost, CU, that the swarm pays. Since the swarm has new information about worksites, expected reward, R', is generated. When they get the new piece of information, scouts can become workers, but they can also pass that information to other members of the swarm, recruiting more workers. Discovering and sharing of information is characterised by the information gain, I.

Workers act as actuators of the swarm. They can share information with each other and they do work, turning the information that they have into the actual reward, R. However, there is a potential, unique to each combination of a robot control strategy, environment structure, and swarm mission, that the workers have to pay displacement cost, CD, in order to use their information. For example, some workers might be recruited away from worksites and they therefore need to travel to their worksite to get reward. Furthermore, workers eventually cause worksites to become depleted. This can result in misinformation cost, CM, being paid by robots that are away from their worksites and therefore do not know that the worksites are depleted. At the same time, depletion of worksites decreases p(W), causing scouts to become less successful over time.

Have a closer look at how these metrics are calculated and how the costs change over time.

Applications


The ICR framework has the following applications:

  • It relates micro-level robot behaviour to a macro-level swarm performance by precisely identifying various costs that the robots pay
  • It can aid creation of hypotheses about swarm performance in new missions
  • It provides a first step towards a swarm design methodology where suitable robot behaviour can be chosen based on its effect on swarm performance in a given swarm mission