There are 3 basic ways to coordinate 2 or more robots or team members:

In chronology-based coordination the order that the robots start and finish is critical.  There are nine  possible order configurations between any two robots or team members. For example:

Robot  A       Robot B

These coordination relationships are important  for a number of reasons.  But its usually easy to see if you ask yourself  when  this robot is performing this task  what are the other robots doing?  Should they be doing anything?   Does Robot A depend on Robot B for some reason.  While time or chronology coordination may on the surface appear straight forward, there are many pitfalls.  The robots to be coordinated are operating with different motor speeds and  different acceleration settings.  Power source can become a factor.   Things such as wheel size  can impact  distance vs. time calculations.   Even size and weight can become a factor when attempting to  coordinate  two or more robots based on time.

Robots can also be coordinated based on events. The relationships shown earlier for two or more robots also hold for event-based coordination. Robot  A may be a search  robot  that  is programmed to find an object and report the location of that object.  Robot B might be a retrieval robot.  Robot B is given the location of the object and then retrieves it.  Robot B cannot do its job until Robot A does its job.  The event that causes  Robot A to  stop processing is the location of the object and the event that causes Robot B to start its processing is the location of the object.

A message can be anything from a single character or number to a string containing any  kind of information.  In fact, any piece of data or information exchanged between two or more robots can be considered a message. We use several important message-passing schemes or paradigms to accomplish our robotic teamwork. For example:

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