# A Survey on Swarm Robotics for Area Coverage Problem
## 5 Mobile Robots Hardware Used for Swarm Robotics  
The type of hardware used in swarm robots varies based on the coverage needs. The various types of hardware include cameras, controllers, actuators, and sensors [67; 68]. Each component in the hardware is used to perform a specific task that assists in the functionality of each robot in the swarm [69]. Sensors are essential in facilitating information or data about the surrounding environment; mapping is called mapping. Swarm robots use sensors to analyse the topography of a domain by detecting key features, like land, roads, paths, and obstacles, among other feasible features [70]. The I.R. Proximity Sensor is the standard type of sensor that detects obstacles in swarm robots [71]. Controllers are essential to the swarm robot hardware [72]. Two approaches are used in controlling swarm robots, which include a centralised and decentralised control system [73]. Centralised control is a situation where a lead robot is responsible for dictating the movement of all robots in the swarm [74]. In contrast, a distributed approach is used where each robot in the swarm plans and dictates its movement [75]. The controllers are fused with communication devices to enhance efficiency in covering a large area. Wireless devices like the Internet, Bluetooth, infrared, and LED lights are examples of communication devices that improve the functionality and movement of swarm robots [76]. The selection and application of each controller or communication device depend on the swarm device's type and function. Moreover, power is essential hardware in the swarm robot. Ideally, swarm robots are small; hence, ample power is needed to ensure that the device functions appropriately [77]. It is the role of the power supply unit to ensure that there is an optimal supply of power for the swarm robots. Most swarm robots use lithium batteries with a power voltage capacity of between five and twenty-five of direct current [78]. The batteries provide consistent and high-density voltage in small batteries that can be fitted in small swarm robots. They are some of the robot platforms that are developed and used for swarm robotics as follows:  
Ref. [79] proposed GRITSBot. It is an inexpensive microrobot used for swarm robotics. It allows the user to manage giant cooperative robots and has features encompassing automatic sensors, autonomous recharging, wireless robot reprogramming, and multiple robots. GRITSBot was presented to decrease various robot testbeds to fit on a table and achieve experiments available to many users. GRITSBot is used for an R-shaped area of coverage in the testbed, using thirteen GRITSBot robots distributed in this shape [80]. Ref. [81] proposed milli-robot-Toronto (mROBerTO) has become more prevalent in recent years, particularly for swarm robotics studies, enabling researchers to perform many experiments through many robots in limited areas. Roberto is a new open-source modular design of millirobot) with a \(16\times 16\) mm\({}^{2}\) design, including various sensors such as proximity, IMU, compass, ambient light, and a camera. Roberto is capable of formation control, using an I.R. emitter and detector add-on. It has communication through Bluetooth, ANT+, or both simultaneously. It uses an ARM processor with 256 KB of memory and has the ability to program over the air to handle complex tasks. Roberto robots monitor and explore unknown area coverage via collective behaviour. Also, it is used for robot aggregation in an exciting area [82]. Ref. [83] developed a TurtleBot3 burgers which is the development of TurtleBot2, TurtleBot1, and iRobot's Roomba, respectively. ROS has managed all of these versions (Robot Operating System: a framework for research in robotics). TurtleBot3 is general hardware in a lot of robotics research, as it can solve the shortcomings of old versions. It is a low-cost platform, easily adaptable to particular needs, programmable in MATLAB and Python, and has 360-degree LiDAR (Light Detection and Ranging) sensor.