TOKYO -- A Japanese graduate student has developed and marketed a small drone that can fly autonomously and stably without need for the global positioning system, or a remote controller.
The palm-size drone, called Phenox2, is now on sale.
"There is no other commercially available drone (of this size) that can fly autonomously without using a GPS and whose flight program can be changed freely by its user," said Ryo Konomura, the Ph.D. student at the University of Tokyo who developed the machine.
The development and commercial sale of Phenox2 comes amid growing expectations that such unmanned aerial vehicles will become widely used for business purposes such as spreading pesticides and delivering packages.
The key to the full-scale dissemination of drones is flight safety, and Phenox2 boasts stellar performance.
In a recent demonstration, the operator of a Phenox2 blew a whistle, and the drone took off. It rose to about 1.5 meters above the floor and hovered there without swaying from side to side or up and down.
When the operator pushed Phenox2 to one side with a hand, the drone returned to its original position quickly and smoothly and kept hovering. It can confirm and fine-tune its location in real time.
"It may appear to be easy (for a drone) to keep hovering in the same position. But it is difficult, actually," Konomura said with a smile.
Phenox2 is a compact quadcopter equipped with four propellers, and weighs only 75 grams. It does not require a remote controller, and is capable of flying autonomously and in a stable manner, thanks to various types of sensors on board.
To determine altitude, the drone has an ultrasonic distance meter, as well as a downward-pointing camera to image the floor and confirm its location based on the resulting images.
New image-processing technology devised by Konomura supports Phenox2's accurate autonomous flight.
The new technology extracts multiple characteristic points of the floor and carpeting, such as a pattern and stains, based on the images from the camera. The camera images the floor 30 times per second.
Konomura said that, if Phenox2 is moved to one side, it can determine its new location based on discrepancies in extracted characteristic points and then return to its original location by adjusting the rotational speed of its propellers.
Konomura had to overcome enormous challenges in developing a drone equipped with the new image-processing technology.
Processing images to extract characteristic points of the floor and carpeting in real time usually requires a large amount of storage for the image data. But storage that size would make the drone much heavier and bigger.
To shrink the drone, widely-used personal computer parts cannot be used in their original forms.
To break the development impasse, Konomura set his sights on a field-programmable gate array -- an integrated circuit designed to be configured by the user. He adopted the Zynq XC7Z010, an FPGA chip produced by U.S.-based semiconductor maker Xilinx, for Phenox2.
Using an algorithm for extracting characteristic points of the floor and carpeting, Konomura succeeded in processing image data in real time without storing the data in memory. He has already applied for a patent on this technology through the University of Tokyo.
To be sure, there are commercially available GPS-equipped drones that can autonomously fly routes set by their users. But Phenox2 can fly on its own, making judgments based on images from its cameras.
Phenox2 can fly autonomously, even inside rooms and in basements or other places where GPS radio waves cannot reach.
Konomura always keeps in mind his image of the ideal robot. "If a machine is to be called a robot, it must be capable of judging the situation on its own and moving autonomously," he said.
In June 2014, Konomura secured about $23,000 through crowdfunding service Kickstarter and used the funds to commercialize Phenox2. The drone is priced at 150,000 yen ($1,232), and is available over the Internet.
Phenox2 can do much more than just hover in place. The user can easily change the drone's flight program. For example, the drone is able to navigate an office hallway.
It has a forward-facing camera as well as the downward-facing one, and can shoot video. It also has a microphone and can distinguish and respond to sounds.
Konomura envisions Phenox2 being used as a "flying robotic security guard," able to detect and report suspicious persons and objects in offices at night.