Overcoming Obstacles Related to Operating Fleets of Drones

Drones are already in use by search and rescue teams to find missing hikers. Farmers use them to fly over fields to inspect crops. Soon, delivery companies will employ drones to drop packages at a person’s doorstep.

Borzoo Bonakdarpour is working on ways to improve efficiency and maintain security when operating a fleet of drones. (Photo courtesy of the College of Liberal Arts and Sciences)

With so many applications developing for this technology, an Iowa State University scientist says the following step is to increase capacity by launching fleets of drones. But making that happen is not as easy as deploying several aircraft simultaneously. Borzoo Bonakdarpour, an assistant professor of computer science, says unlike steering a single drone by remote control, working a fleet necessitates an automated system to synchronize the task, but allows drones to autonomously react to a crash, weather, or unforeseen events.

The operating system must be reliable and secure. The drones need to talk to one another without a central command telling each unit where to go and what to do when conditions change. We also want to optimize the time and energy to complete the task, because drone batteries only last around 15 or 20 minutes.

Borzoo Bonakdarpour, Assistant Professor of Computer Science, Iowa State University.

To attack this issue, Bonakdarpour and his colleagues created a mathematical model to compute the cost – time and energy – to fulfill a task based on the number of drones and accessible recharging stations. The model takes into account the energy necessary for each drone to fulfill its portion of the task and fly to a charging station as necessary.

On paper, the solution is fairly easy for a team of computer experts, but Bonakdarpour says transitioning from theory to execution is not as simple. “As we work on one problem, we actually find new problems we must solve. It’s challenging, but that’s also what makes it exciting,” he said.

For instance, if a battery endures 15 minutes in the lab, it may decrease to 10 minutes on a cold or hot day outside. Finding charging stations is another concern. The ideal placement may be in the middle of a lake and unreachable in reality.

Managing tradeoff between energy and security

Grounded on their model, Bonakdarpour, Anh-Duy Vu with McMaster University, Canada; and Ramy Medhat with Google in Waterloo, Canada, formulated four operating approaches – three offline optimization methods and one online algorithm. While an offline method is restricted due to the preprogrammed flight paths do not permit drones to react to unforeseen events or changing conditions, Bonakdarpour says it offers the base for the online algorithm to work.

The scientists carried out a string of simulations using four drones to examine the efficiency and security. They learned the online algorithm successfully managed the security-energy tradeoff within the energy parameters of the drones. The fleet accomplished all assigned tasks and over half of the authentication checks. The scientists recently showcased the findings at the International Conference on Cyber-Physical Systems in Canada.

Defending against hackers, rogue drones

Operating an automated convoy of drones poses security hazards that are less of an apprehension when steering a single drone by remote control. Bonakdarpour says with automation, drones need to receive GPS signal and position regularly. If the signal fails or the drones fly into a zone where GPS is denied, it can quickly become an issue.

If you’re driving your car and lose GPS, your driving skills don’t depend on that signal. You may miss an exit, but loss of signal for a minute is usually not a big deal. However, with drones just a few seconds is not tolerable.

Borzoo Bonakdarpour, Assistant Professor of Computer Science, Iowa State University..

Software bugs or faults may make a drone to fly off course and not obey direction to fulfill the mission. Bonakdarpour says hackers can also transmit the incorrect signal or work a drone to impersonate the fleet. While discovering solutions will require some time, Bonakdarpour says the technology exists to ensure it happens. However, it will also require industry support to construct infrastructure and charging stations as well as regulatory modifications to permit the operation of a fleet of drones.  

Researchers tested the operating models in a series of lab simulations. (Video courtesy of Borzoo Bonakdarpour)

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