# A Survey on Swarm Robotics for Area Coverage Problem
## 5 Mobile Robots Hardware Used for Swarm Robotics
These features make it suitable for motion-planning applications [84]. Also, TurtleBot3 was used to cover a cluttered area that contained unknown obstacles; for example, some experiments used a swarm of TurtleBot Burger to cover different regions [66]. According to [85], e-puck 2 is the hardware extension of the e-puck. E-puck 2 is a Raspberry Pi-suitable platform and has high features used by swarm robotics. It is characterised by more powerful and better-equipped sensors containing WiFi, USB, RGB LED, and a long-distance sensor [86]. E-puck 2 is used for swarm robots in area coverage as an entrapping approach without a communication environment, like a battlefield, depending on the environment information, and the communication made indirectly by the sensors of the camera and laser sensors. Two models were used: GRN (Gene Regulation Network) for entrapping the target pattern and FSM (Finite-State Machine) for moving to the target and, at the same time, avoiding obstacles. Then, these e-puck 2 robots surround the target environment [87]. Many extensions of e-puck, such as Pi-puck, which is an extension for the e-puck and e-puck 2, allow a Raspberry Pi Zero single-board computer to be attached to the robot [88]. Ref. [89] developed Colias IV for studying models of intensive computational embedded, which is a good platform for presenting visuals in algorithms of swarm robotics. Itis a micro-ground mobile robot that occupies a diameter of 4 cm. It is characterised by a strong-ARM processor, has a set of various sensors comprising a small camera and two digital microphones, and has massive possibilities for connectivity. This miniature robot can sense and visually detect bio-inspired models. The benefits of this robot are its small size and depressed cost. The developed Robot Colias IV has revealed the potential for more research depending on multi-agent experiments, such as the aggregation behaviours in robot swarms for the coverage of a particular area. Ref. [90] proposed the WsBot, a tiny swarm robot with little cost used in many domains, especially in smart factories. It introduces characteristics like intelligent agents and industrial teams to perform a global task--the communication method with others for WsBot by Wi-Fi. WsBot can contribute fundamentally to smart factories through area coverage by many swarm robots. These robots have been used in many experiments to enhance manufacturing productivity by using ARENA (platform for small-scale warehouse logistics) to achieve the behaviours of intelligent agents inside it. In addition, it avoids environmental obstacles and improves brilliant manufacturing experiments without using an actual warehouse [91]. According to [92], HeRo 2.0 (Heathkit Educational Robot) is a newer version of the first, simpler version of the HeRo platform. It is a low-cost robot containing a 3D-printed body and off-the-shelf ingredients. This robot is used with swarm robots, according to convenience, for a wide range of applications. It is completely open-source and has various sensors. An Espressif ESP8266 (32-bits160 MHz) microcontroller is used in its main board to accomplish the motors' control and get and process data from the sensor [93]. Robust and reliable communication between robots occurs using built-in Wi-Fi in its microcontroller module. HeRo 2.0 uses a TCP/IP protocol connection to execute the ROS Robot Operating System) with a remote computer. It has two wheels with a maximum speed of 25 cm/s and eight I.R. sensors, which prepare light and proximity metrics for obstacle detection. The modular main board allows the user to include many other components for communication or localisation, like a camera, motors, displays, and transistors. It provides the feature of long-time autonomy for a robot through a powerful Li-Po battery. Many experiments use HeRo 2.0 robots to achieve area coverage tasks by avoiding local collisions with other robots and obstacles. Table 2 shows the specifications of each hardware model.