Flapping wings 500 times per second, weighing only 0.6 grams, collision tumble can also immediately resume flying, this is not some kind of insect, but a real artificial drone.
Its size is like a bumblebee, its appearance is like a tape box with wings, the body consists of four main parts: fuselage, transmission, wing hinges and wings.
Inspired by the mosquitoes that often sting us: If a mosquito is on your face, even if you swat it quickly, it may slip away and can quickly fly back to your face to continue “buzzing”, which is certainly annoying, but also shows that mosquitoes and other small insects have a very high flight flexibility. For example, a fruit fly can flip over in 40 milliseconds when upside down on the ceiling.
These seemingly “insignificant” functions of insects have always been difficult to achieve in artificial flying robots, and the “insect drone” in the previous article was developed by Kevin Chen, an assistant professor in the Department of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology (MIT). Chen, assistant professor of electrical engineering and computer science at the Massachusetts Institute of Technology (MIT), has developed an artificial flying robot with “insect functions”.
The paper, entitled “Collision Resilient Insect-Scale Soft-Actuated Aerial Robots with High Agility,” was recently published in IEEE Transactions on Robotics. (With High Agility).
Talking about the original idea of the research, Kevin Chen said many UAVs are very large and mostly used for outdoor flight. But there are few insect-sized Drones that can fly in complex, chaotic spaces.
He said that the construction of “insect drones” is completely different from large drones, which are usually powered by electric motors, and using such motors in “insect drones” will reduce their efficiency, so it is necessary to give The “insect drone” has to find a replacement for the electric motor.
Insect drone in flight
The main alternative was a small, rigid actuator made of piezoelectric ceramic material, but this actuator is so fragile that it would be difficult to withstand a collision about once a second if it were used in an insect drone. For this reason, they have developed a new type of elastic dielectric actuator.
The “heart” of the “insect drone”: a new elastic dielectric actuator
It is reported that Kevin Chen designed a new elastic dielectric actuator with better flexibility by using a soft actuator, which is made of a thin rubber cylinder wrapped with carbon nanotubes.
When voltage is delivered to the carbon nanotubes, electrostatic pressure is generated, which in turn squeezes and stretches the rubber cylinder, and this repeated squeezing and stretching allows the wings of the “insect drone” to flap quickly.
In a nutshell, the actuator is the key to improving the performance of the drone. In the actuator, the length, width and thickness of the elastomer sheet are 8 mm, 50 mm and 210 microns, respectively. After the elastomer is rolled into a cylinder, carbon fiber caps are attached to the ends and can be connected electrically and mechanically at the same Time.
During fabrication, the team improved resistance production efficiency by reducing contact resistance. Overall, the new actuator can be driven at higher voltages and higher frequencies, and performs better in resonance and free displacement tests.
The final actuator was designed to allow the wings to flap 500 times per second, giving the drone true insect-like agility.
In flight, if you hit it with your hand, it can also be like a mosquito that can’t be swatted, and can resume flight in 0.16 seconds, in addition to air tumbling and other actions.
It is reported that, compared to the team’s previous work, the design of the new drive, its output power density compared to the previous increased by 100%, 560% more efficient energy transfer.
In a nutshell, the drive is like the “heart” of the “insect drone”, after finishing the “heart”, they began to design the other “organs” of the drone Once the “heart” was fixed, they began to design the other “organs” of the drone.
Based on the new data analysis, they redesigned the transmission, wing hinges and wings of the drone, in which the skeleton material of the wings is carbon fiber, and the wings are polyester fiber, which looks like the realistic feeling of cicada wings.
The position shown is the drive
The final “insect drone”, in addition to hovering flight, also has an ascent speed of 70 cm / sec. According to the team, this speed makes the drone one of the fastest soft-moving robots available.
In addition, the UAV has a lift-to-weight ratio of 2.2:1, which means it can carry a payload approximately equal to its weight.
Initial tests and calculations show that the drone can fly for approximately 10-30 seconds using an off-the-shelf lithium polymer battery (LiPo), of which the alloy wire underneath the drone, is primarily used for power. Zhijian Ren told DeepTech: “At the moment, the signal is still output from the controller, and the drone is powered by a voltage amplifier after boosting. Our next plan is to let the drone fly ‘more freely’ with batteries.”
The design of the “insect drone”: it can still “survive” when it encounters a collision
Compared to previous work, the robot’s transfer length was increased from 400 microns to 500 microns, and the hinge size was adjusted to 2.05 mm and 0.10 mm, respectively.
The hinges are made of 12.7 micron thick polyimide film. The new actuator, robotic gearbox and wing hinge “combine” to increase the net lift of the UAV by 83% compared to previous work.
They also further improved the wing design so that the drone can operate under greater aerodynamic loads and “survive” a collision.
To improve wing stiffness, the team used a new type of carbon fiber. They also modified the position of the wing roots and changed the aircraft’s inner beam from a curved to a straight design, which improves the wing’s crash robustness.
In addition, the leading edge wing beam and diagonal wing beam of the wing are aligned with the direction of the carbon fiber, which increases the stiffness of the wing, thus helping the UAV to recover from a collision, as well as to make flips and other maneuvers.
In the flight demonstration, they also found that the drone could achieve controlled hovering flight, as shown in the image sequence below, which shows the drone in flight with a 10-second hover.
In this 10-second hover flight, the altitude error is less than 0.5 cm and the drift in the xy plane is less than 4 cm.
During the hovering flight, the input voltage amplitude of the driver changes slowly under hovering conditions, with the voltage going up and down by 20 V. In contrast, during the rapid fuselage flip, the voltage amplitude of the driver will drop from nearly 2000 V to less than 200 V at 2-3 wing beats (60 ms).
The large voltage change will cause great transient strain on the actuator, but because the actuator is made of elastomer, it is more tolerant than a rigid actuator.
To demonstrate the drone’s agility, they also performed a controlled ascent flight, and fitting results showed that the drone reached an ascent speed of 70 centimeters per second, more than tripling its maximum ascent speed compared to their previous work.
In addition to demonstrating hovering and ascent flight, the drone can also recover from in-flight collisions through feedback control. Figures a-c below show the first collision recovery demonstration, in which they push the drone downward, but this perturbation has a negligible effect on it.
After the drone is hit, the fuselage height decreases by 4 cm, and then it gradually returns to the hovering set point. This shows that the “insect drone” has sufficient control and recovery ability during flight disturbance.
During the period, they did five experiments to verify the air-flip capability of the drone.
It is said that the air-flip demonstration requires a driver to handle the huge amount of transient changes in the input signal.
Talking about the application, Ren Zhijian said, “It can be used in basically all current UAV application scenarios, in search and rescue and exploration, and can enter more narrow and closed spaces. Other application areas are wild natural environment inspection, crop pollination, etc. Benefiting from the advantages of bionic and miniature, this drone will basically not disturb wildlife.”
He added: “The recent Trail rover carried the latest drone, which had to increase its speed exponentially to take off and operate due to the thin atmosphere. And the soft dielectric drive we designed this time has an advantage over conventional motors in high-frequency motion, while not interfering with the drone’s flight in low-gravity environments.”
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