Sunlight, batteries and flying machines - Engineering & Natural Sciences

Sunlight, batteries and flying machines

It has been well over 100 years since Wilbur and Orville Wright achieved the dream of mechanized flight above the shifting sands of Kitty Hawk, North Carolina. Since then, humans’ fascination with flying machines has intensified and led to technologies that would have made those pioneers proud.

group of five young men outdoors assembling a glider
Mechanical engineering team assembles custom glider for high-speed taxi tests

Some of the latest inventors in what the Smithsonian Institution calls the aerial age are recent graduates of The University of Tulsa’s electrical and computer engineering (ECE) and mechanical engineering (ME) programs. During the spring semester of their senior year, the ECE team SolAero, comprising Duke Schaffner (BS ’21), the team lead, Patrick Maley (BEE ’21) and Eli Dittus (BEE ’21) focused on developing an electrical power and autonomous control system for an unmanned aerial vehicle (UAV).

This project was a thorough interdisciplinary venture. SolAero carried out its work in conjunction with that of a ME team led by Michael Heins (BS ’21), which developed a new high-efficiency airframe. In addition, professors Steven Tipton from ME, Parameswar Hari from physics and Kaveh Ashenayi from ECE provided critical assistance to the teams in the areas of aerodynamics, solar capture and power conversion respectively.

young man carrying a large red and white model airplane
Electrical and computer engineering team gathers at the airfield for flight tests

Assistant Professor of Electrical and Computer Engineering Loyd Hook organized the teams, which then collaborated to create a proposal for a NASA grants. Despite not obtaining NASA funding on the first try, the teams pushed forward with developing a working prototype, collect data and then use that data for another proposal submission in June 2021.

Power and control

“My SolAero teammates and I started in January by building the basic power and control system in a small Cessna RC plane that I constructed out of poster board,” explained Schaffner. “We chose poster board because it’s cheap and durable. It also allowed us to learn the working principles of the equipment – autopilot, LiPo batteries, servos, motor and electronic speed controller.”

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In the middle of February, Schaffner, Maley and Dittus then moved on to installing the power and control systems in a larger Citabria-style RC aircraft. Testing and optimizing the systems followed, and then the team undertook its first test flight on March 19. “This milestone enabled us to adjust many of the plane’s parameters to optimize flight and control,” said Schaffner. That same day, they conducted their first, brief autonomous loiter.

red and white model Citabria aircraft with solar panels affixed to the wings
Citabria airplane used to test solar power and control technologies

Schaffner and his teammates applied what they learned from this flight and the data they collected to then start configuring further autonomous features. At the same time, Maley installed the solar panels on the wings and connected the charging circuit to the power system.

With the solar charging ready and the autonomy configured, Schaffner, Maley and Dittus set out on April 10 for their second test flight. Unfortunately, cloudy skies meant lackluster solar-charging data and the solar panels affected the shape of the wing and made the plane much harder to fly. True to the adage that “things happen in threes,” the plane’s tail wheel also broke off. It was time for the men of SolAero to call it a day.

“Working with the control system, I gained a lot of knowledge about planes and flying in general, as well as the different functionalities of an autopilot and how it works with the different components of a UAV. Working with the power system, I learned a lot about working with solar cells.

“It was interesting seeing the current and voltage characteristics throughout the system, and how they changed during operation – specifically, analyzing the current, voltage and power characteristics of the solar cells during flight. I was able to see how the position and orientation of the aircraft with respect to the sun and the power consumption of the plane itself affected the power generated by the solar cells. And I was able to create a program that would accurately predict the power produced by the solar cells based on the position and orientation of the aircraft. I believe this could be helpful when developing advanced autonomy algorithms to maximize solar exposure in the future.” — Duke Schaffner (BS ’21)

young man wearing a blue shirt while seated and operating a remote-control device
Electrical and computer engineering PhD candidate Khashayar Niki Maleki flying a “chase” drone to support flight tests

After replacing the tail wheel and fixing the aerodynamics of the solar cells, the crew set out to fly again on April 19 – thankfully, a calm, sunny day. “We got several flights in and were able to tune many of the autonomy parameters,” Schaffner noted. “With the tuned aircraft, we did an extended autonomous loiter and a 4-waypoint autonomous mission. We also collected plenty of solar-charging data.”

The one thing the team struggled with on April 19 was autonomous landings. However, by looking over the day’s data and making adjustments accordingly, they flew their craft again on April 30 and made several autonomous touchdowns. That outing came to an enforced end, however, when the plan crashed into a tree.

Nevertheless, SolAero collected abundant data, which they are now using to revise their NASA proposal in the hope of securing future funding. The proprietary solar cell augmentation process that will be used for that stage of the project is being developed by Professor Hari and his colleagues.

Once they submit that proposal, the work on the SolAero project will be complete for the time being. Schaffner has accepted a position with ConocoPhillips’ IT division, Dittus landed an apprenticeship with an audio equipment developer and Maley plans to return to TU to start graduate studies in the fall.

Parameswar Hari’s expertise in solar cell technology is also central to the recently announced partnership between The University of Tulsa and Skydweller Aero Inc., which is based on a Small Business Technology Transfer award by the U.S. Air Force to research high-efficiency, cost-effective solar panels for UAVs.

Are you interested in helping develop innovative technologies that will make the future cleaner and safer? Then consider enrolling in one of the exciting programs on offer through TU’s College of Engineering and Natural Sciences.