South Korean engineers have created a mechanical equivalent of the chameleon's tongue, which can almost instantly grab insects and attract them to itself. The device consists of a wind-up spring that first abruptly pushes the metal band forward, and then pulls it back using a clutch that can move between two drive disks. They demonstrated that the grip can fully extend and return in less than 550 milliseconds, and its mass is small enough to fit on a popular quadcopter. The article is published in the journal IEEE Robotics and Automation Letters.
Drones are increasingly used not only for shooting but also for delivering small parcels. For example, it is convenient to use them for the fast delivery of blood and other materials for medical analysis from one clinic to another. At the same time, drones still have a big problem with the flight time, which is usually about half an hour. And since the delivery drone either hangs up or sits down to pick up and deliver the cargo, a significant portion of the battery capacity is wasted. Recently, Japanese engineers showed a project of a station that attaches a parcel to a non-stop drone, adjusting to its trajectory, but to apply this method of collecting and dumping cargo, you need to modify the ground infrastructure.
Lee Dong-Jun Lee and Jong Gwang-Pil Jung of the Seoul National University of science and technology have created a prototype Grappler that runs at high speed and is light enough to be mounted on a typical quadcopter. The developers said that when creating the mechanism, they were inspired by the language of the chameleon — it is able to stretch for a distance of one and a half lengths of the animal's body, and at a speed of up to three and a half meters per second. Thanks to this, the prey does not have time to react to the attack. The key feature of the language and the mechanism created by the authors is not only the speed of forwarding movement but also the fact that after reaching the goal, they return almost at the same speed and almost without delay.
The engineers realized a fast speed when driving in both directions thanks to the use of two drives and a movable clutch between them. In the centre is a metal tape roulette, twisting into a spiral. On the sides of the belt, there are two pressing drive wheels. And between these wheels is a movable block with a winding spiral spring. Due to the fact that it is attached to the actuator from the side, it can move from side to side and contact the gears of one of the two drives, thereby determining the direction of movement of the belt. This made it possible not to use two separate coils or two motors, but simply to switch the same unit between the drives.
The prototype of the capture has a mass of 117.5 grams and dimensions of 12 by 8.5 by 8.5 centimetres. Engineers tested it by tracking movements using a high-speed camera. The test results showed that the grip can stretch out to a distance of 80 centimetres and return back, spending less than 550 milliseconds, and at the same time having a weight of 30 grams at the end. In addition to stationary tests, the developers also showed several first flights of a serial quadcopter with a fixed and working prototype of the capture.
Engineers have spied solutions for drones in the wild before. For example, in 2018, developers from the United States and Switzerland created a pair of drones that can open doors. One of them sticks to the smooth surface of the door using an artificial analogue of a Gecko's foot and presses on the door handle, and the second one hooks on the floor using spikes and pulls the door by a cable.
Photo: Dong-Jun Lee, Gwang-Pil Jung et al. / IEEE Robotics and Automation Letters, 2020