By Steve Hanley from CleanTechnica —- Worried that alterations to the Earth’s climate may wipe out all the bees, leading to a steep decline in the availability of fruits and vegetables? Fear not. Researchers at MIT say they have successfully created robot bees that can do the job of real bees just as well and maybe better in some cases. Why do we need robot bees? Because they can provide a more efficient method for artificial pollination, which will make it possible for farmers in the future to grow fruits and vegetables inside multilevel warehouses. That in turn would boost yields while mitigating some of the harmful effects traditional agriculture has on the environment.
Robot bees could someday swarm out of mechanical hives to rapidly perform precise pollination. Inspired by the anatomy of these natural pollinators. The researchers have overhauled their design to produce tiny, aerial robots that are far more agile and durable than prior versions. The new robot bees can hover for about 1,000 seconds — 100 times longer previously possible. The robotic insects, which weigh less than a paperclip, can fly significantly faster than similar bots while completing acrobatic maneuvers like double aerial flips. They are designed to boost flight precision and agility while minimizing the mechanical stress on their artificial wings. That will enable faster maneuvers, increased endurance, and a longer lifespan. The new design also has enough free space that the robot could carry tiny batteries or sensors, which could make it possible to fly on its own outside the lab.
“The amount of flight we demonstrated in this paper is probably longer than the entire amount of flight our field has been able to accumulate with these robotic insects. With the improved lifespan and precision of this robot, we are getting closer to some very exciting applications, like assisted pollination,” says Kevin Chen, an associate professor in the Department of Electrical Engineering and Computer Science. He is also the head of the Soft and Micro Robotics Laboratory within the Research Laboratory of Electronics and the senior author of an open-access paper on the new design published in the journal Science Robotics.
Prior versions of the robotic insect were composed of four identical units, each with two wings, combined into a rectangular device about the size of a microcassette. “But there is no insect that has eight wings. In our old design, the performance of each individual unit was always better than the assembled robot,” Chen says. This performance drop was partly caused by the arrangement of the wings, which would blow air into each other when flapping, reducing the lift forces they could generate. The new design chops the robot in half. Each of the four identical units now has one flapping wing pointing away from the robot’s center, stabilizing the wings and boosting their lift forces. With half as many wings, this design also frees up space so the robot could carry electronics.
The researchers also created more complex transmissions that connect the wings to the actuators, or artificial muscles, that flap them. These durable transmissions, which required the design of longer wing hinges, reduce the mechanical strain that limited the endurance of past versions. “Compared to the old robot, we can now generate control torque three times larger than before, which is why we can do very sophisticated and very accurate path-finding flights,” Chen says.
Yet even with these design innovations, there is still a gap between the best robotic insects and the real thing. For instance, a bee has only two wings, yet it can perform rapid and highly controlled motions. “The wings of bees are finely controlled by a very sophisticated set of muscles. That level of fine-tuning is something that truly intrigues us, but we have not yet been able to replicate,” he says.
Robot Bees 2.0
The wings of the robot bees are driven by artificial muscles — tiny, soft actuators made from layers of elastomer sandwiched between two very thin carbon nanotube electrodes and then rolled into a squishy cylinder. The actuators rapidly compress and elongate, generating mechanical force that flaps the wings. In previous designs, when the actuator’s movements reached the extremely high frequencies needed for flight, the devices often started buckling, which reduced the power and efficiency of the robot. The new transmissions inhibit this bending-buckling motion, which reduces the strain on the artificial muscles and enables them to apply more force to flap the wings.
Another new design involves a long wing hinge that reduces torsional stress experienced during the flapping-wing motion. Fabricating the hinge, which is about 2 centimeters long but just 200 microns in diameter, was among their greatest challenges. “If you have even a tiny alignment issue during the fabrication process, the wing hinge will be slanted instead of rectangular, which affects the wing kinematics,” Chen says.
After many attempts, the researchers perfected a multi-step laser-cutting process that enabled them to precisely fabricate each wing hinge. With all four units in place, the new robotic insect can hover for more than 1,000 seconds, which equates to almost 17 minutes, without showing any degradation of flight precision. “When my student was performing that flight, he said it was the slowest 1,000 seconds he had spent in his entire life. The experiment was extremely nerve-racking,” Chen says.
The new robot reached an average speed of 35 centimeters per second, the fastest flight researchers have reported, while performing body rolls and double flips. It can even precisely track a trajectory that spells out M-I-T. “At the end of the day, we’ve shown flight that is 100 times longer than anyone else in the field has been able to do, so this is an extremely exciting result,” he says.
Next, Chen and his students want to see how far they can push this new design, with the goal of achieving flight for longer than 10,000 seconds. That’s nearly 3 hours, which should really test the concentration of the students. Improving the precision of the robots so they can land and take off from the center of a flower is also part of the plan the researchers have for improving the robot bees they have created. Looking further out, the researchers hope to install tiny batteries and sensors onto the aerial robots so they can fly and navigate outside the lab. “This new robot platform is a major result from our group and leads to many exciting directions. For example, incorporating sensors, batteries, and computing capabilities on this robot will be a central focus in the next three to five years,” Chen says.
