Dynamic Compass Models and Gathering Algorithms for Autonomous Mobile Robots

Distributed Computing by Mobile Robots: Gathering

“…In the synchronous models (Fsync and Ssync), the cycles of all robots are fully synchronized: the sensors that become active do so all at the same time and each operation of the life cycle is performed by all robots simultaneously [1,6,11,13,19,20,21,29,41,52]. In the asynchronous model (Async), there is no global clock, and the robots do not have a common notion of time; furthermore, the duration of each activity (or inactivity) is finite but unpredictable [15,26,27,36,46].…”

“…With respect to the level of global agreement on the local coordinate systems, different assumptions are made, ranging from availability of a global positioning system [31,32,35,40,43], to the agreement on the direction and orientation of both axes but not on the unit of distance nor the origin (e.g., as provided by a compass) [26,27], to partially accurate agreement on the direction and orientation (e.g., inaccurate compass) [34,36,49], to the absence of any relationship among the local coordinate systems of different robots [6,27,52], i.e., when the robots are disoriented.…”

Computing by Mobile Robotic Sensors

“…In fact, algorithmic robotic research usually assume unlimited visibility: the entities are capable of determining the location of all other regardless of their position in the region, e.g. [1,9,12,19,35,52,53,70,77,81,83,91]. Additional differences between robotic sensors and traditional models of autonomous robots and micro-robots robotic sensors are that usually the robots are more powerful (both memory-wise and computationally) than sensors, and typically there is no requirement for the robots to reach a state of static equilibrium (e.g., in most cases the swarm just converges towards a desired formation or pattern).…”

“…For example (see Figure 2), sensor s in transit towards its destination, is seen by r; however, s is not aware of r's existence and, if it starts the next cycle before r starts moving, s will continue to be unaware of r. This (realistic but more difficult) model, sometimes called Corda, is used e.g. in [9,35,33,34,52,53,70]. While s is moving, r enter state Locate and sees s; however, s is still unaware of r. After s passes the visibility circle of r, it is still unaware of r.…”

“…Another important concern is clearly the one of the presence of possible faulty sensors. The fault-tolerant issues have been recently addressed in [1,52,79], but only in the unlimited visibility setting.…”