# Charging Platform of Chess-Pad Configuration for Unmanned Aerial Vehicle (UAV)
## 1 Introduction  
Unmanned aerial vehicles (UAVs) are used for a wide range of functions. They can be controlled remotely by a ground pilot or pre-programmed to fly semi-autonomously or fully autonomously to a specified coordinate by Global Positioning System (GPS) navigation. The relatively short flight time, due to the low specific power capacity of the power sources, is one concern for the implementation of aircraft robots. The energy source required for a flight is stored in a battery that is typically a lithium-ion battery. Consequently, the most appropriate option for expanding its duration is to land on a unique rehabilitation platform. The platform can either exchange or charge the power source. These UAVs are also known as drones, which are impressive because they can operate in restricted areas and are highly maneuverable, finding applications within indoor and outdoor environments. Those applications include security, control, repair, shipping, delivery, search, rescue, and military [1, 2]. Multirotor UAVs with four propellers mounted on high-speed, brushless Direct Current (DC) motors or multi-rotor UAVs with four propellers fitted on brushless DC motors have many types of payloads. Those payloads include electric sensors and control systems to ensure a stable flight, high-resolution cameras, and objects for delivery [3]. A high-density lithium battery is selected for the proposed system since more energy has to be produced for a lifting force against gravity and should be in motionat all times whereby it requires a high motor energy consumption. Because of that, this multirotor UAV can only fly for a short time. A typical lithium battery can permit a flight time of 20-40 min [3; 4; 5], and this is the main drawback of these vehicles. Therefore, there is an apparent need to switch the battery periodically for longer terms of operation. Unfortunately, this charging task is carried out by direct human interference; this has inspired many researchers to automate this recharging procedure. Many proposed solutions have considered a UAV multi-copter charging station to extend the mission without the need for human intervention. In recent years, many works have focused on increasing flight time; three types of research are working on different solutions. The first approach is to provide a UAV with a larger battery power capacity, which necessarily leads to an increase in weight and thus negatively affects range and payload efficiency. The second is to adopt a battery replacement system that can swap batteries automatically directly after docking [6; 7; 8; 9]. This solution makes it possible for a UAV to fly back and continue its mission in a short period. However, with many mechanical elements, this system could be impractical due to cost and complexity. Another proposed solution comprises a laser beam device that transmits the power directly to the drone [10; 11; 12]. The method of laser powering was discovered by [PERSON] nearly half a century ago [13]. However, this method has a severe problem regarding safety, because a powerful laser can damage a human eye, as found in the research and experiments conducted by the authors of [14; 15]; this method is also impractical due to the low power charging efficiency and high current consumption of UAV motors. The third method of wireless charging is wireless power transfer (WPT) technology. This technology is familiar with many low power charging systems such as smartphones and electronic appliances [16; 17; 18; 19; 20]. This principle of this technology enables the transfer of electricity via a magnetic resonance between two different coils. The wireless power transfer technique can successfully transmit power over a range of up to 2 m [16]. Nevertheless, these kinds of charging systems that utilize magnetic resonant induction require little intervention and disruption to their surrounding environments [17; 21; 22; 23].