Sruti Gan Chaudhuri

Robots with Lights: Overcoming Obstructed Visibility Without Colliding

Robots with lights is a model of autonomous mobile computational entties operating in the plane in Look-Compute-Move cycles: each agent has an externally visible light which can assume colors from a fixed set; the lights are persistent (i.e., the color is not erased at the end of a cycle), but otherwise the agents are oblivious. The investigation of computability in this model is under way, and several results have been recently established. In these investigations, however, an agent is assumed to be capable to see through another agent.

Circle formation by asynchronous fat robots with limited visibility

This paper proposes a distributed algorithm for circle formation by multiple autonomous mobile robots. The vision of each robot is limited to a maximum distance. The robots do not store past actions or records of past data. They are anonymous and cannot be distinguished by their appearances. All robots agree on a common origin and axes. Earlier works report algorithms for gathering of multiple autonomous mobile robots in limited visibility considering the robots to be dimensionless or points. This paper models a robot as a unit disc (fat robot). The algorithm presented in this paper also assures that there is no collision among the robots. The robots do not share a common clock. They execute the algorithm asynchronously.

Gathering asynchronous transparent fat robots

Gathering of multiple robots is a well known and challenging research problem. Most of the existing works consider the robot to be dimensionless (point). Algorithm for Gatheringfat robots (unit disc robots) has been reported for 3 and 4 robots. This paper proposes a distributed algorithm for Gatheringn (n≥5) autonomous, oblivious, homogeneous, asynchronous, fat robots. The robots are assumed to be transparent and they have full visibility.

Circle Formation by Asynchronous Transparent Fat Robots

This paper proposes a distributed algorithm for circle formation by a system of mobile robots. Each robot observes the positions of other robots and moves to a new position. Eventually they form a circle. The robots do not store past actions. They are anonymous and cannot be distinguished by their appearance and do not have a common coordinate system (origin and axis) and chirality (common handedness). Most of the earlier works assume the robots to be dimensionless (points). In this paper a robot is represented as a unit disc (fat robot). The robots are assumed to be transparent in order to achieve full visibility. However, a robot is considered as a physical obstacle for another robot. The robots execute the algorithm asynchronously.

Leader election and gathering for asynchronous fat robots without common chirality

This paper proposes a deterministic gathering algorithm for n ? 5 autonomous, homogeneous, asynchronous, oblivious unit disc robots (fat robots). The robots do not have common coordinate system and chirality. A robot can sense or observe its surroundings by collecting information about the positions of all the robots. Based on this information, they compute their destinations for moving and move there. Initially, the robots are stationary and separated. Robots are assumed to be transparent but solid. The algorithm for gathering is designed in such a way that the robots do not collide. In order to avoid collision we do not allow all the robots to move at a time. A unique robot, called leader is elected to move to its destination. No other robot moves till the leader reaches its destination. When the leader reaches its destination, another leader is selected from the remaining robots. However, leader election may not be possible in an arbitrary configuration. In this paper, we characterize all geometric configurations where leader election is possible and present an algorithm for leader election in such a case. An important property of our leader election algorithm is that it is possible to elect a leader from the remaining set of robots also.

Formation of General Position by Asynchronous Mobile Robots Under One-Axis Agreement

The traditional distributed model of autonomous, homogeneous, mobile point robots usually assumes that the robots do not create any visual obstruction for the other robots, i.e., the robots are see through. In this paper, we consider a slightly more realistic model, by incorporating the notion of obstructed visibility (i.e., robots are not see through) for other robots. Under the new model of visibility, a robot may not have the full view of its surroundings. Many of the existing algorithms demand that each robot should have the complete knowledge of the positions of other robots. Since, vision is the only mean of their communication, it is required that the robots are in general position (i.e., no three robots are collinear). We consider asynchronous robots. They also do not have common chirality (or any agreement on a global coordinate system). In this paper, we present a distributed algorithm for obtaining a general position for the robots in finite time from any arbitrary configuration. The algorithm also assures collision free motion for each robot. This algorithm may also be used as a preprocessing module for many other subsequent tasks performed by the robots.

Gathering Asynchronous Swarm Robots under Nonuniform Limited Visibility

This paper proposes a distributed algorithm for gathering a group of autonomous, homogeneous, oblivious, asynchronous mobile robots having limited visibility sensing ranges. To the best of our knowledge, all reported results have assumed that the visibility ranges are uniform for all the robots. In contrast, we consider that the visibility ranges of the robots are not uniform. Moreover, the robots have no knowledge about the visibility ranges of other robots. However, a lower bound on the visibility range of all the robots is known to all the robots.

Fault-Tolerant Gathering of Asynchronous Oblivious Mobile Robots under One-Axis Agreement

In this paper, we have studied one of the fundamental coordination problems for multi robot system, namely gathering, for n ≥ 2 asynchronous, oblivious mobile robots in the presence of f < n faulty robots. Earlier works have reported that, in general, to solve gathering problem for asynchronous robots, many assumptions are required, like multiplicity detection or total agreement in coordinate axis or constant amount of memory bits. However, in this paper we have proved that gathering of asynchronous robots is possible with less number of such assumptions and even in the presence of any number of faulty robots. In our case, the robots only agree on the direction and orientation of any one axis.

Gathering of Asynchronous Mobile Robots in a Tree

This paper addresses a robot-based distributed model which makes use of a group of small, inexpensive, identical, oblivious mobile robots placed in nodes of an anonymous and unoriented tree. The robots operate in Look-Compute-Move cycles; in one cycle, a robot takes a snapshot of the current configuration (Look), takes a decision whether to stay idle or to move to one of its adjacent nodes (Compute), and in the latter case makes an instantaneous move to this neighbour (Move). Cycles are performed asynchronously for each robot. In this paper, we present a distributed algorithm by which κ robots deterministically gather at a single uniquely marked node in a tree with η nodes. The robots have limited visibility and have no common agreement in coordinate axes.

Validation of a DiffServ based QoS model implementation for real-time traffic in a test bed

This paper presents a DiffServ based adaptive QoS model for real-time interactive traffic in constrained bandwidth IP network without over provisioning the users. A WRR based QoS scheduling algorithm has been implemented to allocate the network resources to the users. A tuning parameter for VBR real-time traffic is also introduced in order to provide fair performance to the non real-time traffic as well. The QoS model is implemented at the transmitter edge of the network. Edge switches and routers are configured with the proposed algorithm. The simulation (using NS2) and experimental results (using a test bed with real time network scenario) are presented for validation of the proposed model.