The Swarm-Copters system was developed at the University of North Texas as part of the Department of Computer Science and Engineering Senior Design course by Mark Moudy and his project team. The purpose of the Swarm-Copters system is to perform search and rescue operations by using a swarm of autonomous unmanned aerial vehicles (UAVs) to find missing persons while avoiding the risk of endangering lives and incurring exorbitant costs associated with traditional search and rescue (SAR) methods. The system was designed to use the Arducopter and QGroundControl open-source platforms.
The Swarm-Copters system uses multiple sensors to assist with flight, a camera system to provide a real-time view of the search area, and a centralized base station to control the search and rescue operation
Currently when a person gets lost, a rescue team is called into action to use a wide range of terrain-specific methods and tools to help locate the missing person. This system is problematic because it is expensive and there is a high risk of the rescuers becoming rescuees. Quadcopters are ideal for simulating a network of unmanned aerial vehicles (UAVs) in a search and rescue situation because they can be outfitted with a range of situation specific sensors, are easily mobilized, and can reduce risk to the rescuers. The system was developed using a swarm style approach which allows for two or more autonomous quadcopters to work together to complete a scan of a search grid.
The Swarm-Copters system is organized into two related but independent sub-systems, the quadcopters [Figure 1] and the base station [Figure 2]. The quadcopter sub-system is responsible for all flight functionality and receives task instructions from the base station which uses the onboard sensors and flight features to execute SAR missions. The base station is responsible for mission planning, capturing in-flight data, and issuing instructions to the quadcopter swarm. These two sub-systems are tied together via an XBEE point-to-multipoint network that allows both sub-systems to pass messages through the MAVLink communications protocol.
The Swarm-Copters system is capable of performing a broad scan of a defined area in the event of an SAR by using a swarm of UAVs to scan a search area and distribute the task among all available units. All UAVs checked into the system fly autonomously and are fitted with a range of sensors to provide real-time flight data and video feeds. UAVs are controlled via the base station which provides the operator with a heads up display of all flight information, mission planning and control capabilities. An Automated Flight Planning widget has been implemented to generate all intermediate waypoints and distribute the current SAR tasks among all UAVs checked into the system.
The Automated Flight Planning widget takes an input of either two or four control waypoints to define the boundaries of the search area. The widget automatically generates the UAV flight paths and evenly distributes the search area among all UAVs in the swarm through the use of a lawnmower search algorithm. [2] Refer to Figure 4 for a graphical representation. The automated flight plan also takes advantage of the evenly distributed workload among the UAVs to either complete the search faster or expand the effective search range of the system. After the flight plan has been generated, the user has the option to save the flight plan, upload it to the quadcopters, or delete the flight plan and start over
The Swarm-Copters system utilizes a lawnmower search algorithm to effectively traverse the search area and guarantee detailed coverage of the search area [2]. Each span lane generated for a given UAV’s flight path is set to the center of the width of the camera’s field of view to ensure full coverage of the search area. The guiding principle for the implementation of this search algorithm is to read the current position of the UAV and then calculate the motion required to arrive at a target waypoint. Once motion is calculated, we then calculate the heading trajectory and rate of speed reduction needed to stop the UAV at the ending waypoint.
The UAV swarm is simulated with two or more quadcopters that are each independently capable of autonomous flight. The quadcopters receive messages from the base station containing waypoint information and the specific flight mode to use while traversing between waypoints. Currently the system uses five main flight modes during autonomous SAR execution. Refer to Table 2 for more information about flight modes.
