MIT team designs and improves new "artificial muscle" material to drive micro-aircraft to achieve long-term high-precision flight

   A related paper was published under the title "A High-Lift Micro Aerial Robot Driven by Low-Voltage Long-Life Dielectric Elastomeric Actuators" and was selected as the cover article of the journal.

  Dielectric elastomer actuators can directly convert electrical energy into mechanical energy based on electric field driving, which can be used in the production of "muscles" of soft robots. However, compared to rigid actuators such as piezoelectric bimorphs and electromagnetic motors that drive rigid robots, most dielectric elastomer actuators on the market have lower power density and lifetime, and require higher drive voltages.

  To this end, a research team from the Massachusetts Institute of Technology designed a new dielectric elastomer actuator "based on parallel multilayer electrode material technology, with low driving voltage and strong durability", which can not only improve the power of micro air vehicles , and make it outperform other aircraft of the same scale in all aspects.

  It is understood that the aerial robot integrated with the dielectric elastomer actuator has the best performance and longest flight time among the existing acrylic aerial robots. Its hovering time reaches 20 seconds, and the position and attitude errors are less than 2.5 cm and 2 degrees, and achieved a long service life of more than 2 million driving cycles.

  Moreover, the lift-to-weight ratio of the robot has also been improved, from the previous 2:1 to 3.7:1, which is currently the best performance that can be achieved under the same size.

  Ren Zhijian, the first author of the paper, said that they were able to achieve such a breakthrough thanks to further reducing the thickness of each layer of elastic polymer in the dielectric elastomer actuator.

  In addition, the team made efforts to address the high driving voltage of dielectric elastomer actuators. Previously, the dielectric elastomer actuator needed to reach a working voltage close to 2000V to make the robot take off, and their newly developed dielectric elastomer actuator only needs an operating voltage of about 500V.

  From a materials standpoint, reducing the voltage means increasing the number of layers while reducing the thickness of each layer of elastic polymer, the researchers said. Although the idea is easy to come up with, there are various problems in the specific operation.

  For example, increasing the number of layers will increase the time to bake the polymer, and the overall fabrication time of the actuator will increase exponentially, which is not conducive to further reducing the thickness; moreover, as the thickness decreases, the air bubbles in the elastic polymer can easily become trapped in the elastic polymer. It is broken down during the power-on test, resulting in a decrease in the overall performance of the driver.

  Faced with these problems, the team conducted repeated fabrication process adjustments and sample tests, and introduced some targeted solutions, such as vacuuming immediately after each layer of elastic polymer spin-coating to greatly reduce air bubbles, and multiple exposures. into the oven and other specific processing details. In the process of constant exploration and trial, they finally found a relatively stable processing technology.

  Subsequently, they also conducted various comparative tests, such as static fan test, dynamic lift test and final aircraft take-off test. Through these tests, the researchers obtained complete data demonstrating that their latest machining process has indeed improved the overall performance of dielectric elastomer actuators and MAVs.

  Ren Zhijian said that most of their work was completed during the epidemic, so they needed to try as many different production processes as possible in the limited experimental time, analyze the data obtained from the test, and then think about how to improve.

  It is worth mentioning that they were accepted 3 months after the first draft was submitted, and it was a very smooth process overall. The reviewers believe that the research is of great significance in the fields of dielectric elastomer actuators and micro-UAVs, and praised the improved dielectric elastomer actuator fabrication process, saying "although simple and traditional , but very effective."

  Ren Zhijian also said that when he was studying at Carnegie Mellon University, he knew Suhan Kim, the co-first author of another paper, and the two had a certain tacit understanding, so they were able to distribute their experiments smoothly during the epidemic. tasks and communicate effectively at the same time.

  It is understood that Ren Zhijian graduated from the Department of Automation of Shanghai Jiaotong University with a bachelor's degree, and then went to the Department of Mechanical Engineering of Carnegie Mellon University to study for a master's degree.

  He said that the dielectric elastomer actuator developed by him is still in the laboratory stage, and there is still a certain distance to practical application. In the long run, this dielectric elastomer actuator-driven MAV can be used in rescue search, complex terrain exploration, and agricultural seeding.

  In the next step, the team intends to increase the controllability of the micro-UAV by optimizing its structural design on the existing basis. In addition, they also plan to design a lightweight power supply circuit based on low operating voltage to achieve the goal of wireless flight.



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