Is that a robotic insect on your shoulder?

Harvard University’s Dr. Kevin Ma and Dr. Robert Wood, along with their team, recently performed a successful test flight of the smallest flying robot ever built. This success also came with a few strings attached.

The first versions of the insects are tied by very thin cables to both the power source and the computer controlling the fly’s flight. Before the tiny drones can be used for any practical purposes, high density fuel cells smaller than currently available are needed. In addition, even tinier processors allowing both on-board reflexive responses and radio, wifi, microwave or some other communications from the controlling computer must be produced.

Such a small brain to control the robot fly’s movements is being worked on by Gu-Yeon Wei and David Brooks from the Harvard School of Engineering and Applied Sciences (SEAS).

The prototypes used in the demonstration of the robotic insects weigh in at only 80 milligrams.  They accomplished controlled jaunts through the air for short periods through the  vigorous flapping of their wafer-thin mechanical wings.  The flies (which are about the size of a U.S. penny), move the wings at the rate of 120 beats per second. That’s that same as a Syrphis Fly, but slower than a housefly (190).

During the tests conducted by the scientists, the test machines are able to move in basic patterns such as hovering. Hovering is accomplished when the forces of thrust motion and lifting motion continually buffeting the robot are compensated for very quickly via the movements of the wings, whether insect or robot.

At the very small size scale that the robot flies move in, trivial changes in airflow can cause catastrophic effects on the stability of the fly. Because of this, the navigating system must respond almost immediately to retain a smooth flight. After about 20 seconds, the flies crash, due to, perhaps, the lack of an on-board stabilization system.

During those 20 seconds, however, the fly is more than able to move and react quickly enough to easily elude the attempts of any human to swat it, or even touch it. This may be a by-product of the precision of the movement the wings are capable of.

The speed of the moving of the wings is accomplished through the use of a piezoelectric material. This is a ceramic substance that expands and contracts when an electric field is applied. This means the “muscle” contracts at the speed of the electric charge applied to it. Very quickly, indeed.

Kevin Y. Ma, co-lead author of the paper concerning the robots, and a graduate student oa SEAS said, “Large robots can run on electromagnetic motors, but at this small scale you have to come up with an alternative, and there wasn’t one.”

The hinges of the wings are thin joints of plastic. They are placed inside of the carbon fiber body frame of the robot fly. The system that controls the rotating movements of the wings must be carefully linked to the feedback of the movements. Amazingly, the two wings are controlled by separate systems.

When the researchers turned the juice on and then off, alternating very quickly, the piezoelectric substance acts just in the manner of the actual fly’s diminutive muscles. This experiment has lead to other researchers delving into the workings of organic flies in hopes of discovering ways to better the robots design.

Uses of the results produced by the robotic fly research might be: include distributed environmental monitoring, search-and-rescue operations, assistance with crop pollination, or, of course, surveillance, by the police or military.

The research described in this article was supported by the National Science Foundation and the Wyss Institute for Biologically Inspired Engineering at Harvard.