In 1994, the Carnegie Foundation for the Advancement of Teaching established the Carnegie Classification as a way to identify degrees of research excellence in universities and colleges in the United States. To be considered for one of the classification system’s prestigious rankings of R1 (Doctoral Universities – Very high research activity), R2 (Doctoral Universities – High research activity), or D/PU (Doctoral/Professional Universities), institutions have to fulfill a list of requirements. There are more than 5,000 universities and colleges in the United States. Of all of these institutions, only 131 of them have been awarded the Carnegie Classification’s highest ranking, R1.

One such institution is the Colorado State University (CSU), a public research university in Fort Collins, CO. Founded in 1870, CSU spans 4,773 acres at the base of the Rocky Mountains. With around 33,000 undergraduates, CSU is also nationally ranked as the 153rd best university in the US. Both faculty and students at CSU have been making amazing strides in technology at the school’s number of research labs. The Adaptive Robotics Lab has recently presented advancements for extending the flight time of a drone by enabling one to perch on various surfaces.

The Adaptive Robotics Lab is run by Assistant Professor of Mechanical Engineering, Dr. Jianguo Zhao. As outlined on the lab’s website, “The lab aims to design and build novel small and adaptive robots that can reconfigure their shapes, structures, or functionalities to fulfill multiple tasks (e.g., walking, flying, swimming) in diverse environments (e.g., on land, in the air, or underwater). Such robots will have diverse applications ranging from environmental monitoring, search and rescue, to military surveillance.” The current subjects the lab is working on revolve around interlink with soft, flying, and reconfigurable robotics. On November 11, 2020, under the mentorship of Dr. Zhao, engineering students Haijie Zhang, Elisha Lerner, and Bo Cheng published their research that combines all three principles being used in tandem with a drone.

Titled “Compliant Bistable Grippers Enable Passive Perching for Micro Aerial Vehicles”, the paper explains how the team created a robotic mechanism for a drone to perch on objects like the side of a building, street sign, powerline, pipe, or tree limb. The team was inspired by how a bird perches on such structures. For the project, the team used micro drones in the lab, but the robotic devices can be rescaled to attach to a drone of any size. As the opening lines of the paper states, “Micro aerial vehicles (MAV) with multiple rotors, or multicopters, have many promising applications ranging from environmental monitoring, agricultural inspection, to package delivery. These applications, however, usually face a critical problem: the flight time of MAVs is limited due to the low aerodynamic efficiency and high energy consumption.” Drone designers have long been looking for ways to have a drone “take a break” to conserve energy while en route.

The bistable grippers developed by Dr. Zhao’s students are 3D printed, soft, reconfigurable robotic devices that connect to a drone. Rather than moving through joints like traditional robotic devices, the bistable gripper has a softer form that moves more naturally. The movement is akin to how muscles flex and move as opposed to the bending of a joint. The device has a plunger like bar with two gripping prongs attached to it. When the bar comes in contact with pressure, the prongs fold together to perch. The paper goes on to describe the gripper’s two functions: “First, using bistability, it can passively switch from open to closed state using the impact between the gripper and the perching object, alleviating the requirement for precise motion control. Second, the gripper has two perching methods for different objects. For objects with a small height, it can form a closed diamond shape to encircle the objects (encircling method). For objects with a large height, the gripper’s two fingers can clip on each side of the objects to utilize the friction forces for perching (clipping method).”

The gripper attaches to the top of a drone. When a drone needs to perch on an object, say a pipe, the pilot positions it to line up with the structure. The pilot then flies the drone up to make contact with the surface. The plunger bar instantly registers the pressure contact from the pipe and mechanically activates the soft, reconfigurable gripping arms. Once perched, the drone can be remotely shut down to conserve battery power. Whey ready to resume flight, the pilot again remotely powers up the drone and disengages the gripper. The gripper device uses a minimal amount of battery power to activate and deactivate. The only real trick is for the pilot to be able to control the drone into flight as the gripper releases. However, for an accomplished drone pilot, this should be a relatively easy task.

While the concept of a drone that can perch like a bird to conserve energy isn’t novel, the model developed by Dr. Zhao’s students is. The fluidity of soft reconfigurable robotics means that the device has fewer parts and can thus weigh less, a critical detail for aerodynamics. It also means that the mechanics have less of a chance of kicking and failing as joint based robotics. Another bonus of this system is the fact that it is built with a 3D printer that greatly minimizes the cost while allowing the devices to be scaled to fit a drone of any size. For now, this is still just a research project, but it has tremendous applications for use in commercial drones. As Dr. Zhao said, “They can be very helpful in applications like search and rescue or environmental monitoring. they are very small, we can build many of them, we can deploy them autonomously, and they can talk to each other and get information back for us.” The research being done in labs like Dr. Zhao’s Adaptive Robotics Lab is exactly why CSU is ranked as an R1 institution.

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