Citrus and strawberries are a big part of the economy in Florida, and with a variety of diseases taking their toll, ways of identifying the diseases earlier are critical.

Mechanical engineering associate professor Yunjun Xu and a group of his students have been creating the robot since 2013 when Xu and University of Florida agricultural engineer and associate professor Reza Ehsani landed a U.S. Department of Agriculture grant worth more than $1.2 million. The goal is to develop an automated system that would use robots and specialized sensors in the air and on the ground to detect and report disease in citrus groves and strawberry fields.

The prototype robot is the size of a small generator and carries eight cameras, spectral sensors, a GPS, four batteries, and complex software instructions to direct it to glide up one row and make a U-turn when needed before heading back down another row. It can adapt to roam in narrow or wide fields and can go for several miles before needing a charge. There is also a protected space onboard the robot to house the sensors. Xu’s graduate and many senior design course students worked as a team to create the working prototype.

“We are fine-tuning it now,” Xu said.

Currently, people have to go into the fields and search for symptoms of different diseases. This is time consuming, expensive and prone to error. Early detection of a disease is hard because people can only detect a disease when the symptoms are visible, and in some cases waiting for symptoms to appear could be too late for the best management, Ehsani said.

Ehsani and his students are progressing on the special sensors that will be able to detect and report disease information quickly. He works from his lab at the Citrus Research and Education Center in Lake Alfred and travels to �鶹ӳ����ý when needed.

Much of the first two years at �鶹ӳ����ý was spent on what Xu calls “less than glamorous work.” His team built the vehicle, developed software architecture, and tested out the prototypes to ensure they would work in field conditions where the soil type and terrain can be challenging. The team has another three years to complete the project.

Xu expects to continue testing and adapting the prototype robot before more field testing is completed this summer.  For now, Xu and his students continue to work on the robot, taking it apart to get into the engineering building and rebuilding it when it’s ready to hit the strawberry patch again.

“We’re getting there, one step at a time,” Xu said.

These picosatellites, which weigh less than 1 kilogram (about 2.2 pounds), are a lot less expensive than conventional large satellites and easier to launch into space as secondary payloads because they take up so little room on spacecraft.

But there’s one problem – many payloads require that the picosatellite point in a specific direction. That’s where a partnership between a planetary sciences researcher and an engineering associate professor at the �鶹ӳ����ý comes in.

Todd Bradley and Yunjun Xu went to grad school together and have stayed friends throughout their careers. They both have common interests in pico-scale satellite technologies and their applications in space science. When they both got jobs at �鶹ӳ����ý, they naturally started talking about their work. Soon a joint project evolved.

They wanted to test how well a picosatellite (more commonly known as CubeSat) can point a payload in zero gravity by using the Earth’s magnetic field.

“It’s just amazing how quickly the technology is moving,” said Nicolas Pelaez, one of two aerospace engineering students who worked on the project. “Everything is now getting smaller, so hopefully soon we’ll be able to do a lot more with picosatellites in space.”

The current team, including fellow student Chris Stevens, worked on the project for a year. They made significant modifications to a 10x10x10 cm satellite (about 4 inches cubed) and then suspended it in air on a string. Two Helmholtz coils on opposite sides of the cube produced magnetic fields to mimic the Earth’s own field. They tested and adjusted, tested and adjusted and then tested and adjusted again until they had a working model. The has provided support since 2009 when an engineering senior design team first began working on this project.

In February Bradley, Pelaez and Stevens got to ride a Zero-G plane – courtesy of NASA in Houston – for four days to test whether their control system worked. They experienced zero gravity 160 times during their flights to see if what worked in the lab, worked on the plane.

“It did, I can say it was successful,” said Bradley, who leads the zero-gravity experiments for the team. “We’re still combing through all the data we collected, but it worked just as we expected it would.”

When the plane hit zero gravity, the picosatellite free-floated. The team was able to instruct it to turn in specific directions and it oriented itself accordingly each time using the earth’s magnetic field. The experiments served as a flying laboratory to test the performance of the satellite because in the ground lab the satellite can only rotate around one axis.

The next step, Xu said is to hopefully obtain enough funding and find a flight opportunity to send it into a low Earth orbit.”

Pelaez will likely already have graduated by the time their satellite is launched, but he said the experience was priceless.

“I learned an insane amount during this project, with the two main areas of focus being simulations and software coding,” Pelaez said. “This experience has given me huge insight into how a real professionally run experiment should be conducted.”

He plans to eventually start his own space-related engineering business.

Bradley, who’s worked on several space missions including Messenger (orbiting Mercury), Cassini (studying the Saturn system), and OSIRIS-REx (an asteroid sample return mission), is optimistic that soon the technology will reach the point where the picosatellites will be able to carry more sophisticated science experiments.

As a member of �鶹ӳ����ý’s Center for Microgravity Research, he’s working on developing a scientific instrument that would study the dust particles found orbiting Earth. The device is small enough that it could be attached to a picosatellite and would collect dust data he needs. It could yield clues about how the planet was formed millions of years ago. The Space Research Initiative, through the Florida Space Institute, is funding research and development of the dust instrument.

“I think working together, collaboration between scientists and engineers can get us there,” Bradley said. “I really think that’s the best approach.”

�鶹ӳ����ý mechanical engineering associate professor Yunjun Xu is working with UF agricultural and biological engineer and associate professor Reza Ehsani to develop an automated system that would use robots and specialized sensors in the air and on the ground to detect and report disease in citrus groves and strawberry fields.

“One of the benefits of our project is making it automated, which can improve accuracy and reduce the cost of disease and stress detection,” Xu said.

�鶹ӳ����ý’s team, which includes Suhada Jayasuriya, a former �鶹ӳ����ý mechanical and aerospace engineering professor, and graduate students, is developing several robotic components for the ground vehicle that would be used – something akin to a small tractor. Xu is also creating a simulation environment to ensure the prototype system will work in the field.

Currently, people have to go into the fields and search for symptoms of different diseases. This is time consuming, expensive, and prone to error. Early detection of a disease is not possible because people can only detect a disease when the symptoms are visible, and in some cases waiting for symptoms to appear could be too late for the best management, Ehsani said.

“This project seeks to employ technologies that can significantly improve the efficiency and accuracy of detecting plant stress in the field at early stages of diseases,” he added. “The project proposes to use UAVs (unmanned aerial vehicles) and ground robots to monitor different crops. Small UAVs and robots can be the farmers’ eye in the sky and on the ground to monitor everything that is going on in the field.”

Continuously monitoring crops for any sign of biotic and abiotic stress can potentially help growers to better manage nutrition deficiencies and diseases, which could lead to better yield and profits. It can also potentially reduce excessive use of chemical inputs and their impact on the environment.

UF’s team, which is based at the Citrus Research and Education Center in Lake Alfred, will focus on the crop-stress sensing and monitoring systems.

“The work is just getting started and preliminary testing will not take place before next fall. Full-scale testing will occur in year four of the grant at a commercial site yet to be selected,” Xu said.

If successful, the technology developed and the protocol for using it would likely be applicable to other agricultural products, the researchers said.

The United States Department of Agriculture is the funding agency.