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Flying, insect-like robots fly closer to the independent flight

  Image of a four-bladed robot.
Enlarge / The RoboBee XWing without power and electronics.

Noah T. Jafferis and E. Farrell Helbling, Harvard Microrobotics Laboratory.

Just When the researchers at Harvard announced more than six years ago that they had made tiny flying robots, they immediately talked about the prospect of autonomously working their tiny creations in complicated environments. This was highly optimistic as the robots tracked a couple of copper wires that provided power and control instructions. The robots were guided by a computer that monitored their position with a camera.

Since then, however, the team has been working to refine the tiny machines and, for example, give them improved landing skills. And today the team announces the first demonstration of a self-propelled flight. The flight is very short and not self-directed, but the small vehicle manages to carry both the power supply circuit and its own power source.

A Question of Miniaturization

There are two approaches to miniaturization that you can think of as top-down and bottom-up. From top to bottom, companies are shrinking their components and reducing their weight to fly ever smaller versions of quadcopter drones. Some of them are already available from 1

0 grams. However, this type of hardware faces some hard physical constraints that will limit the extent of its shrinkage. For example, more batteries are used for packaging and supporting hardware than for charge storage. And friction plays a dominant role in the performance of standard rotary engines.

The alternative is bottom-up. Start with something similar to the flying insect-like robots and find out how to expand their abilities. Not surprisingly, the Harvard team has chosen a bottom-up approach since building the insect-like robot.

The original design featured piezoelectric motors that quickly beat two wings and powered the robot. Power with the high voltage and fast oscillations was supplied from the outside. The same was true for flight control information: a camera system tracked the robot during the flight, and a computer made the necessary adjustments and sent the appropriate adjustments directly to the wings.

The goal of this work is to eliminate these from some of these external hardware, downsize it so it can be placed aboard the robot itself. In this new work, the researchers focused on the energy source that holds the robot in the air.

Shrinking the Energy

As mentioned above, batteries have problems shrinking to the weights required for it, as things like the case, wiring and materials used to collect charges always add weight, no matter how small the weight Energy storage is. The best battery the researchers could find weighed four times as much as the robot's prototype. Instead, the team turned to photovoltaic hardware, where a 10-mg device can generate more than 7 watts of power in full sunlight.

However, flying the original hardware would require about seven times the performance. Therefore, the researchers improved the efficiency of the robotic flight by increasing the wing area and at the same time slowing down the flapping of the wings. And the easiest way was to double the number of wings, with each actuator now beating with two wings. Together with some improvements to the actuators, these have increased the lift of the wings by almost 40%.

  The complete RoboBee X-Wing design, including performance and electronics. "Src =" https: //cdn.arstechnica.net/wp-content/uploads/2019/06/Integrated_Bee.image-jpeg-640x640.jpeg "width =" 640 "height =" 640 "srcset =" https: / /cdn.arstechnica. net / wp-content / uploads / 2019/06 / Integrated_Bee.image-jpeg-1280x1280.jpeg 2x
Enlarge / The complete RoboBee X-Wing design, including performance and electronics.

Noah T. Jafferis and E. Farrell Helbling, Harvard Microrobotics Laboratory

The next problem was the connection of the piezo actuators to the solar power source. The piezo actuators require a high voltage (200 volts) and a fast switching (200 hertz oscillations). These parts were assembled from a mix of handmade and handmade components.

The ultimate design is to place the solar panels on a stalk, a bit like an umbrella. This is done to prevent the panels from interfering with the airflow driven by the blades. The electronics, on the other hand, stick to the bottom of the robot and provide a little balance. The entire pack weighs only 90 milligrams and has a weight ratio of 4: 1. The somewhat cumbersome result, the authors refer to as RoboBee X-Wing.

Flight in short bursts

How does it work? Well, the attached video shows that it flies, but only extremely short; Typical flights last less than half a second and require the incoming light of three suns. The authors refer to this as "sustainable," which appears to expand the definition of the word. The robot usually manages the control simply by not flying long enough to deal with it.

A short video that describes the new flying robots. While the existing robot weighs only 90 milligrams, it can generate more than 350 milligrams of buoyancy. The authors estimate that they could almost double the weight of the vehicle while still maintaining enough lift for decent performance. In this way, the solar modules can easily be upgraded to increase power, integrate sensors on board, or transfer the control processing system to the vehicle – or possibly more than one of them.

The current RoboBee X -The wing design also has a lot of effort for improvement. The authors suggest redesigning the actuators to halve the required voltage to simplify the voltage conversion electronics. This electronics could almost certainly be miniaturized, which would further reduce the weight. Further improvement of the electronics should allow the robot to recover some of the power it consumes, effectively increasing available power. The researchers also want to investigate how air interacts with the four wings of the robot to further optimize buoyancy.

There is plenty of room for improvement, and there is no doubt that one day the RoboBee Mark II will be closer to the flight, and rightfully so called "sustainable." In this sense, the RoboBee X-Wing should be considered as a second prototype, as a successor to the first version, which is intended as a pioneer for new technologies. Arguing about the use of the word "sustainable" is secondary, as the goal of this machine is to find out whether a solar-powered version actually puts the hardware on the right track to bring it to sustainable flight, possibly with a useful payload ,

Nature 2019. DOI: 10.1038 / s41586-019-1322-0 (About DOIs).

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