Swarm robotics

Swarm robotics is an approach to the coordination of multiple robots as a system which consist of large numbers of mostly simple physical robots. It is supposed that a desired collective behavior emerges from the interactions between the robots and interactions of robots with the environment. This approach emerged on the field of artificial swarm intelligence, as well as the biological studies of insects, ants and other fields in nature, where swarm behaviour occurs.

Definition
The research of swarm robotics is to study the design of robots, their physical body and their controlling behaviours. It is inspired but not limited by the emergent behaviour observed in social insects, called swarm intelligence. Relatively simple individual rules can produce a large set of complex swarm behaviours. A key-component is the communication between the members of the group that build a system of constant feedback. The swarm behaviour involves constant change of individuals in cooperation with others, as well as the behaviour of the whole group.

Unlike distributed robotic systems in general, swarm robotics emphasizes a large number of robots, and promotes scalability, for instance by using only local communication. That local communication for example can be achieved by wireless transmission systems, like radio frequency or infrared.

Goals and applications
Miniaturization and cost are key factors in swarm robotics. These are the constraints in building large groups of robots; therefore the simplicity of the individual team member should be emphasized. This should motivate a swarm-intelligent approach to achieve meaningful behavior at swarm-level, instead of the individual level.
Much research has been directed at this goal of simplicity at the individual robot level. Being able to use actual hardware in research of Swarm Robotics rather than simulations allows researchers to encounter and resolve many more issues and broaden the scope of Swarm Research. Thus, development of simple robots for Swarm intelligence research is a very important aspect of the field. The goals include keeping the cost of individual robots low to allow scalability, making each member of the swarm less demanding of resources and more power/energy efficient.

One such swarm system is the LIBOT Robotic System that involves a low cost robot built for outdoor swarm robotics. The robots are also made with provisions for indoor use via Wi-Fi, since the GPS sensors provide poor communication inside buildings. Another such attempt is the micro robot (Colias), built in the Computer Intelligence Lab at the University of Lincoln, UK. This micro robot is built on a 4 cm circular chassis and is low-cost and open platform for use in a variety of Swarm Robotics applications.

Advantages and disadvantages
The most frequently cited benefits are:

low cost for more extensive coverage;
a redundancy capacity (if one of the robots fails due to a failure, blockage, etc. another robot can take steps to troubleshoot or replace it in its task).
the ability to cover a large area. Duarte & al. have for example shown (via a simulation applied to the case of the island of Lampedusa) in 2014 that a swarm of 1000 small aquatic drones dispersed at sea from bases could in 24 hours make a surveillance report on a maritime band 20 km long;

To date, swarms of robots can only perform relatively simple tasks, they are often limited by their need for energy. More generally, the difficulties of interoperability when one wants to associate robots of nature and of different origins are also very limiting.

Properties
Unlike most distributed robotic systems, swarm robotics insists on a large number of robots 6 and promotes scaling, for example the use of local communications in the form of infrared or wireless.

These systems are expected to have at least the following three properties:

robustness, which implies the ability of the swarm to continue to function despite the failures of certain individuals and / or changes that may occur in the environment;
flexibility, which implies a capacity to propose solutions adapted to the tasks to be performed;
the "scaling", which implies that the swarm must function regardless of its size (from a certain minimum size).

According to Sahin (2005) and Dorigo (2013) in a swarm robotic system, in the swarm:

Each robot is autonomous;
robots are usually able to locate themselves relative to their closest neighbors (relative positioning) and sometimes in the global environment, even if some systems try to do without this data;
the robots can act (eg to modify the environment, to cooperate with another robot);
The detection and communication capabilities of robots between them are local (lateral) and limited;
the robots are not connected to a centralized control; they do not have the global knowledge of the system in which they cooperate;
the robots cooperate to perform a given task;
emerging phenomena global behaviors can thus appear.

Applications
Potential applications for swarm robotics are many. They include tasks that demand miniaturization (nanorobotics, microbotics), like distributed sensing tasks in micromachinery or the human body. One of the most promising uses of swarm robotics is in disaster rescue missions. Swarms of robots of different sizes could be sent to places rescue workers can't reach safely, to detect the presence of life via infra-red sensors. On the other hand, swarm robotics can be suited to tasks that demand cheap designs, for instance mining or agricultural foraging tasks.

More controversially, swarms of military robots can form an autonomous army. U.S. Naval forces have tested a swarm of autonomous boats that can steer and take offensive actions by themselves. The boats are unmanned and can be fitted with any kind of kit to deter and destroy enemy vessels.

Most efforts have focused on relatively small groups of machines. However, a swarm consisting of 1,024 individual robots was demonstrated by Harvard in 2014, the largest to date.

Another large set of applications may be solved using swarms of micro air vehicles, which are also broadly investigated nowadays. In comparison with the pioneering studies of swarms of flying robots using precise motion capture systems in laboratory conditions, current systems such as Shooting Star can control teams of hundreds of micro aerial vehicles in outdoor environment using GNSS systems (such as GPS) or even stabilize them using onboard localization systems where GPS is unavailable. Swarms of micro aerial vehicles have been already tested in tasks of autonomous surveillance, plume tracking, and reconnaissance in a compact phalanx. Numerous works on cooperative swarms of unmanned ground and aerial vehicles have been conducted with target applications of cooperative environment monitoring, convoy protection, and moving target localization and tracking.

Drone displays
A drone display commonly uses multiple, lighted drones at night for an artistic display.

In Popular Culture
A major subplot of Disney's Big Hero involved the use of swarms of microbots to form structures.

Research
They cover many topics including:

software and software enhancement;
improving the robots themselves. In 2010, two Swiss researchers from Lausanne (Floreano & Keller) proposed to draw inspiration from Darwinian (adaptive) selection to develop robots;
the ability to evolve in 3 dimensions (in the air for a fleet of aerial drones, or underwater for a swarm of underwater robots), for example for the study of the dynamics of water bodies and marine currents;
improving their ability to cooperate with each other or with other types of robots;
on swarm behavior assessment (video tracking is essential to study swarm behavior in a systematic way, even if other methods exist, such as the recent development of ultrasonic tracking.) Further research is needed to establish a methodology suitable for the design and reliable prediction of swarms when only the traits of individuals are known);
comparing the respective advantages and disadvantages of top-down and bottom-up approaches.

Source from Wikipedia