## 2 UAV-Enabled ITS Framework
### First Layer: Technical Specifications
#### 2.1.1 Design and Specifications  
For the successful integration of UAVs into ITSs, the design and specifications of UAVs should adhere to the requirements. UAVs are categorized by their lift mechanism into three main types, fixed-wing, rotary-wing, and hybrid [14; 17], as depicted in Figure 2. Fixed-wing UAVs typically use propellers to provide horizontal thrust, making them more energy-efficient and able to achieve longer flight times than multi-rotor UAVs. Fixed-wing UAVs can vary in wing shape and configuration, including normal (straight), swept-back, swept-forward, and delta wings [18]. They are known for their stability, larger size, and superior flying capabilities, including better cargo capacity and endurance. However, their size makes them less versatile than rotary-wing UAVs. On the other hand, rotary-wing UAVs, or rotorcraft, generate lift with a single rotor or multi-rotor (two rotors or more). Multi-rotor UAVs are categorized based on the number of propellers into quadcopters, hexacopters, and octocopters. Additionally, multi-rotor UAVs can have variations in rotor arrangements, such as H, I, X, or Y configurations, which impact their flight dynamics and stability. These rotors, attached to the center body and pointed upwards, enable these UAVs to maintain a constant altitude and utilize their vertical take-off and landing (VTOL) capabilities. Despite their smaller size, rotary-wing UAVs offer more excellent maneuverability and versatility than fixed-wing UAVs. Additional efforts have been made to develop hybrid UAVs that combine the gliding capabilities of fixed-wing UAVs with the vertical takeoff and landing (VTOL) capabilities of rotary-wing UAVs [17; 18]. When selecting the most suitable UAV type for a specific ITS application, several factors must be considered, including the UAV's physical requirements, such as size, weight, maneuverability, flight time, and energy capacity. The size of the UAV should be appropriate for the type of operation as it directly impacts the total flight time and overall efficiency. For example, smaller and lightweight UAVs (typically under 2 kg) are primarily used for recreational purposes. Slightly larger UAVs (ranging from 2 kg to 150 kg) are commonly employed by private companies for tasks such as delivering packages, aerial photography, crop dusting, or powerline/pipeline inspection. Fixed-wing UAVs (exceeding 25 kg) are predominantly utilized by the military for armed reconnaissance and surveillance operations [14]. Rapid maneuverability is another critical attribute to consider in the design, as UAVs could encounter unexpected obstacles and sudden weather changes. Also, the weight of the UAV needs to be considered in the design since the required energy level and the UAV's physical load are related. The UAV's physical load must be as light as possible to maintain the necessary energy level. A heavier UAV structure requires more energy to maneuver, often resulting in a larger battery pack. The weight of a UAV is closely tied to the challenges of payload transportation. Several advancements, such as energy-based control (EBC), can stabilize the vehicle's translational dynamics and reduce payload oscillation. Additionally, a nonlinear state feedback controller utilizing linear matrix inequalities (LMI) can effectively manage the quadrotor's rotational dynamics [19]. Selecting the appropriate battery per the energy requirement is another crucial step toward designing an efficient UAV system [20]. Lithium polymer (LiPo) batteries are often employed as energy sources in UAVs due to their ability to provide a large amount of power, considering their size [21]. However, these batteries could be over-discharged or overcharged, leading to ignition. The voltage range for LiPo cells is approximately 3 V to 4.5 V. The type of motors used by UAVs often need higher and constant voltage to function properly.