In the future, autonomous drones can be used to transfer stocks between huge warehouses. The drone can fly into the semi -final structure of the size of several football fields, moving to hundreds of identical crossings before docking in a precise place where it is needed.
Most of today’s drones would probably have difficulty performing this task, because drones usually move outside with GPS, which does not work in internal environments. In the case of navigation in rooms, some drones employ a computer vision or lidar, but both techniques are unreliable in gloomy environments or rooms with ordinary walls or repetitive functions.
MIT scientists have introduced a modern approach that allows the drone to self -control or determine its position in internal environments, gloomy and low visibility. Aircraft is a key step in autonomous navigation.
Scientists have developed a system called Miflyin which the drone uses radio frequency waves (RF), reflected by a single marker placed in its environment, to autonomous self -control.
Because Mifly allows self -control only with one diminutive tag that can be placed in a wall such as a sticker, it would be cheaper and easier to implement than systems requiring many tags. In addition, because the Mifly marker reflects the signals sent by the drone, not generating its own signal, it can be supported with very low power.
Two ready -made radars mounted on a drone allow location in relation to the marker. These measurements are connected to the data from the on -board drone computer, which allows you to estimate its trajectory.
Scientists conducted hundreds of air experiments with real drones in internal environments and found that Mifly consistently located the drone at a distance of less than 7 centimeters.
“As the understanding of perception and calculations increases, we often forget about signals that are beyond a visible spectrum. Here we looked beyond GPS and a computer vision at millimeter waves, and in this way we have opened new drones in internal environments that were not possible before, “says Fadel Adib, associate professor at the Faculty of Electrical Engineering Engineering and Information Technology, director of the Signal Kinetics Group at Mit Media Lab and an older author A Paper about Mifly.
Adib joins the article by the authors and research assistants Maisa Lam and Laura Dodds; Aleine Eid, there was Postdoc, which is now an adjunct at the University of Michigan; and Jimmy Hester, CTO and co -founder of Atheraxon, Inc. The research will be presented at the IEEE conference on computer communication.
Distracted signals back
To enable drones self -control in gloomy, internal environments, scientists decided to employ a millimeter wave signals. Milimeter waves, which are widely used in current radars and 5G communication systems, work in the gloomy and can travel through daily materials such as cardboard, plastic and internal walls.
They decided to create a system that could only work with one tag, so it would be cheaper and easier to implement in commercial environments. To make sure that the device remained low power, they designed the reverse dispersion marker, which reflects the magic wave signals sent by the drone radar. The drone uses these reflections for self -control.
But the drone radar would receive signals reflected from all over the environment, not just tag. Scientists overcame this challenge using a technique called modulation. They configured the tag to add a diminutive frequency to a signal that distracts to the drone.
“Now the reflections from the surrounding environment are returning with one frequency, but reflections from the marker return with a different frequency. This allows us to separate the answers and simply look at the reply from the tag – says Dodds.
However, using only one marker and one radar, scientists could only calculate distance measurements. They needed many signals to calculate the location of the drone.
Instead of using more tags, they added the other radar to the drone, mounting one horizontally and one vertically. The horizontal radar has horizontal polarization, which means that it sends signals horizontally, while vertical radar would have vertical polarization.
They took into account polarization to tag antennas so that she could isolate separate signals sent by each radar.
“Polarized sunglasses receive some polarization of lightweight and block other polarities. We used the same concept for millimeter waves, “explains Lam.
In addition, they used various modulation frequencies to vertical and horizontal signals, which further reduced interference.
Thorough estimation of the location
This architecture of double polarization and double modulation gives the spatial location of the drone. But drones also move at an angle and rotate, so to enable the drone navigation, he must estimate his position in space in relation to six degrees of freedom – with the data of the trajectory, including the tone, deviation and the roller in addition to ordinary forward/ backward, backward, left/right and up/down.
“Drone rotation adds a lot of ambiguity to estimates a millimeter wave. This is a massive problem, because the drones rotate a bit when they fly – says Dodds.
They overcame these challenges, using a built -in inertial drone measurement unit, a sensor that measures acceleration, as well as changes in height and attitudes. By combining this information about a millimeter wave measure reflected by the marker, they allow Mifly to estimate the full position of the six -lane drone freedom in just a few milliseconds.
They tested a drone equipped with mifly in several internal environments, including in a laboratory, aerial space in mit and frail tunnels under the campus buildings. The system consistently achieved high accuracy in all environments, locating the drone up to 7 centimeters in many experiments.
In addition, the system was almost so precise in situations where the marker was blocked from the view of the drone. They achieved credible location estimates up to 6 meters from the marker.
This distance can be extended in the future using additional equipment, such as high -power amplifiers or by improving the radar and antenna design. Scientists also plan to conduct further research by including Mifly in the autonomous navigation system. This can allow the drone to decide where to fly and make a flight path with a millimeter wave technology.
“Infrastructure and locations that we prepare for this work are a strong foundation that can be more durable to enable various commercial applications,” says Lam.
These studies are partly financed by the National Science Foundation and Mit Media Lab.