In the article, “The RoboBee Flies Solo,” Harvard John A. Paulson School of Engineering and Applied Sciences (2019) has stated that after decades worth of research, they have successfully developed the lightest ever vehicle to maintain sustained untethered flight on solar power.
They stated they have developed an extremely lightweight circuit and integrated high-efficiency solar cells to tackle the trade-off between mass and power. The addition of an extra pair of wings and a more efficient transmission gave the vehicle the extra lift it needed to forego the power cord and instead, integrates the smallest commercially available solar cells. These weigh in at 10 milligrams each and can harvest 0.76 milliwatts of power per gram, weighing the vehicle at 259 milligrams with a power consumption of 120 milliwatts. It stated their next aim was to add a control board to fly it outdoors.
What the team behind the RoboBee project has accomplished is remarkable, to say the least. They were able to maintain untethered flight, in a package that is no lighter than 259 milligrams. However, the project is still in its infancy stage and is unable to operate outside of controlled lab conditions.
The biggest factor as to why the RoboBee is not ready to explore the outdoors is how the solar panels are being utilised. Currently, it requires the intensity of 3 equivalent Sun lumens to power the circuitry. They were able to replicate this in the lab by using large Halogen lamps pointing directly at the solar panels. However, stated in the article, they reassured that they are planning to work on a model that is 25 percent times bigger than its current iteration. This would reduce the number of suns to 1.5, much closer to reality.
The next factor is that the current iteration does not have any onboard batteries. The solar panels that are affixed atop the RoboBee only power the actuators and circuitry. This means that if the solar panels are not directly facing the light source, due to a change in pitch or yaw, it would face a disrupt in power supply. This is evident in their test flight video, that demonstrates the RoboBee taking off, but a second later, it comes crashing down. The disrupt in power supply could be a cause of this. As stated before, a larger model of the RoboBee is being developed, and as such, will have space to hold batteries.
The last factor is that it currently does not have any flight control on board. In a closed environment, the RoboBee can maintain sustained flight. However in the outdoors without a flight control system, the RoboBee is unable to take into account external forces such as the speed of the air. This will cause the RoboBee to go haywire. A flight control system is imperative if the RoboBee is to fly outdoors.
It needs to be said that, RoboBee is not the first of its kind to have been developed. Researchers in the University Of Washington unveiled the RoboFly at the IEEE International Conference on Robotics and Automation in Brisbane, Australia in 2018. Both have similar ideas of attaining untethered flight, by using alternative sources of energy. Remarkably, the RoboFly is powered by a laser being pointed at its photovoltaic cell, which can harvest 250 milligrams to power the drone. However, when the laser misses its target, the drone will be powerless and will come down crashing. They stated that their next move was to develop a laser that will track the drone. This may not be so practical Thus, comparing the 2 drones, it can be said that the RoboBee, could be a more viable concept of untethered flight outdoors.
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