Unmanned Aerial Tracking Drone

Project Description

The Forestry department at Northern Arizona University (NAU) has been conducting research on bat colonies in the forests of Northern Arizona. This research requires bats to be captured and then tagged with VHF (very high frequency) radio transmitters. During the day, when the bats are inactive in their roosts, the signal from these transmitters are tracked to determine the location of the bat colony. Currently, this is done by hiking into the mountains and triangularting the signal responses by hand; an exhausting and lengthy process. To ease the process, several iterations of an Unmanned Aerial Vehicle (UAV) have been designed by engineering students at NAU. The UAVs are designed to fly to a set height and travel in a programmed path that optimizes the telemetry between the transmitters and the receiver system carried on the UAV. Once a signal is found, the data collected needs to be analyzed to determine the direction of the signal. The determined direction is then be used to map a location for the next flight. By performing this flight in several places, the UAV could help triangulate the position of the roosts much faster and at less of a physical burden to the researchers.

The team’s client, Dr. Shafer, has been involved in projects that utilize telemetry and gained knowledge that was beneficial for the research on these bats. He was approached by a professor from another department and informed about the trouble that the researchers were having. Dr. Shafer generated the idea of using a drone for collecting the signal locations more efficiently. He then established the capstone team that would design the first model of this drone, and continues to guide the teams that produce each iteration.


The team was tasked with engineering the fourth iteration of the drone by designing a new frame that could meet more requirements. The project description was defined by Dr. Shafer as follows:
“I would like your project to develop an improved UAV design capable of lifting the animal tracking antenna and associated electronics. The total payload capacity should be between 1 and 2 lbs. The UAV design should be robust to field deployments (not delicate or hard to assemble). The UAV should also be collapsible so that it can be packed and carried into the field.”

In addition to this description the team also considered the requirements for the previous iterations of the drone. These requirements the drone be able to:

  • Execute a programmed flight path
  • Collect signal locations at several points along the path.
  • Return to operator
  • Withstand drops from distances of three feet with no damage and up to six feet with repairable damage.

Customer Requirements

The following Customer Requirements and weightings (out of 250) were developed to satisfy the customer needs:

Lightweight 80
Strong/Rigid 80
Collapsible 50
Low Center of Gravity 30
Aesthetics 10


The Lightweight and Strong/Rigid requirements were not only the highest weightings but also equal because they were the two main needs of the project. The UAV needed to be portable to the degree that it could be carried on long treks to data collection sites in rural and mountainous terrains without fatiguing the operator. Along with helping reduce operator fatigue, minimal weight was desired to extend operation time. For this project, lightweight is defined as under one pound. Additionally, the drone needed to be strong enough to sustain minimal damage in the event of a crash landing, as the wind conditions at the data collection sites are typically non-ideal for flight.

If the UAV was collapsible, it could be carried in a backpack, increasing the portability requested by the customer. Since collapsibility is a matter of convenience and not necessity, it has a lower rating than the aforementioned requirements.

The low center of gravity requirement was based on the customer request for stability during the drone flight. A low center of gravity provides inherent mechanical stability to the drone, before any aids need to be implemented electronically. Although this was important to the project, it was less intensive than the other tasks and, therefore, received a lower weighting.

Finally, the aesthetics requirement is not imperative to structural integrity or performance. However, the customer insisted this requirement be included. The drone is planned to be open-sourced but a professional frame design is more easily marketed for research grants.


Engineering Requirements

Engineering requirements are technical measurements and goals that help further define the customer requirements. Not all engineering requirements can be quantities, some are just more precise requirements for the design. All engineering requirements created for this project are described below.

Lightweight To make the UAV easily portable over long distance hiking (where larger weights would cause great fatigue) the frame needs to be lightweight. Considering 6 lbs to be around the largest weight desired to avoid fatigue, and the fact that the operator has 5 lbs of tracking equipment, the frame is desired to a weight under one pound.
High Power to Weight Ratio The UAV, including the tracking equipment rig, needed to have a high power to weight ratio as a built in factor of safety. The team’s target was a 2:1 power to weight ratio.
Durable The customer requested that the UAV sustain minimal damage from a 4 ft fall. This is to prepare the copter for rough landings during operation.
High Rigidity The motors create torsion during flight, requiring the adhesive affixing the joints to the arms must have a rigidity large enough to combat this effect.
Targeted Break Locations To protect the parts made of expensive and/or difficult to access material, breaking points are going to be designed into the cheaper frame part.
Low Storage Volume The backpacks used for these hikes are generally 50 L. However, the team is aiming for 25 L to account for the operator’s personal items (water, food, etc.).
No Tools Required for Construction To alleviate the amount of equipment the operators must carry on the hikes, the drone needed to be constructed without the use of extensive tools. Ideally, the frame would be able to be constructed without the use of any tools.
Small Parts Tethered to Copter Small parts are easily lost, especially with excessive relocation. To avoid excess cost for replacing these small parts the team made any part less than 2 in connect to the body of the UAV by magnet or tether.
Payload Under Prop Height Both requirements were to lower the center of gravity and provide the drone with an inherent stability during flight.
Payload Attached to Underside of Platform
Built from Easily Accessible Material The operators do not have large funding pools or access to advanced engineering materials. Therefore, in case of a fracture or break, the drone was constructed of cheap and easily accessible materials.
Cheap Material
Stable During Flight The operators are not experienced with flying drones so the drone was constructed to be as stable as possible.