Prof. Harikumar Kandath enumerates all that it takes for efficient traffic management of uncrewed aerial vehicles.
By the end of this decade, the number of registered uncrewed aerial vehicles (UAVs) in India will go to a few lakhs from the present value of close to 30,000 (source DigitalSky, Govt. of India). Efficient implementation of unmanned aircraft system traffic management (UTM) will be the key to reliable, safe and scalable UAV flights. UTM services primarily include offline mission planning, online motion planning, health monitoring and flight safety system, identifying intruders and handling emergency scenarios. The offline mission planning is global and provides feasible flight trajectories for UAVs in a given airspace.
UTM Planner
The feasible trajectories should maintain the required physical separation between the UAVs. The planner should consider the types of UAV (fixed-wing/multi-rotor/hybrid-VTOL), their navigational performance, atmospheric conditions like wind speed and direction, time constraint for each UAV to complete the mission, static obstacles, and no-fly zones. The online motion planner is invoked locally when a UAV encounters either a static obstacle unknown to the offline mission planner, or a dynamic obstacle. The UAV returns to the pre-defined trajectory once the obstacle avoidance is completed.
Flight Safety
The health monitoring flags the faulty operation of the UAV sensors and actuators. The flight safety system receives inputs from the health monitoring system and takes measures like switching to redundant sensors/actuators or abrupt termination of the flight. In the case of emergency landing, a suitable landing location ought to be identified through local search and sense methods. Identifying the intruding air vehicle is primarily done using anti-UAV systems. The confirmation of intruders leads to an emergency situation that can even result in the temporary cease of flight operations.
Central Controller of UTM
A ground control station (GCS) is the central node that plans and controls the entire UTM system. The GCS should have sufficient computing capabilities to execute offline mission planning algorithms. A large database of the authorized UAVs that utilizes the given airspace along with the real-time weather information from the service provider is needed for the mission planning. A robust communication network is also necessary to monitor all the UAVs. The real-time flight data received from the UAVs has to be displayed, analyzed and stored.
Essential Hardware and Infrastructure
The primary sensors required for UAV flights are the inertial measurement unit (IMU), magnetometer, GPS, altimeter and the airspeed sensor. The obstacle avoidance requires additional sensors like LIDAR, camera, and RADAR. A companion computer to process the data from obstacle avoidance sensors and health monitoring sensors is essential apart from the main flight computer. A robust communication device is needed to transfer the real-time flight data to the GCS. Launch and landing facilities (Vertiports) are to be constructed and maintained to ensure smooth take-off and landing operations.
Risk Factors
There are multiple risk factors like network security, loss of flight stability, loss of communication, attack of intruder UAV to be considered while designing the UTM system. Compromise of network security can lead to a catastrophic situation. Loss of flight stability might result in damage to life or property. Recovery of a vehicle from unstable flight conditions using a remotely operated pilot is a daunting task. Intermittent loss of communication can be tolerated but permanent loss should result in emergency landing of the vehicle. Identifying intruder UAVs in low altitude flight regime is a challenging task. A robust anti-UAV system that can detect, identify, track, intercept and mitigate the intruder UAV is needed.
Feasibility of Large Scale UAV-based Applications
Considering the risk factors involved, the air traffic density achievable will be far less than the theoretically available space to fly. The infrastructure development and maintenance cost will be a significant factor that will determine the economic aspect of UTM-based transport. The major areas of interest would be air ambulance, medical supply delivery, and long distance transport of goods. Thus the medium (>25 Kg) and large (>150 Kg) category UAVs will be the candidates that would be preferred for these applications. The use of UAVs in densely populated cities for large scale parcel delivery seems to be far-fetched as of now.
This article was initially published in the October edition of TechForward Dispatch