The drone with legs has finally learned to walk



Russian and Kazakh engineers have taught a drone with legs that can land on uneven surfaces, walk on them. The development will allow the use of drones during rescue operations after earthquakes or in other places with uneven terrain, the authors of an article in the IEEE Journal on Miniaturization for Air and Space Systemssay.


When developing a robot, engineers usually select a design based on future tasks. If the robot needs to move on a relatively flat surface, it is most effective to use wheels. In difficult terrain with many small elevation differences, walking or crawling robots are more optimal. And for large differences in altitude, only an aircraft is suitable, but in return for the ability to fly, developers have to put up with a short time of operation of the device.

For many years, engineers from various organizations have been working on hybrid robots that combine the ability to fly and move efficiently on the ground. So far, these developments are at the prototype stage and are almost not used in practice, and the main design type in them is a combination of a wheeled robot and a multi-copter, both in the form of a single object and in the form of a pair of robots.

Engineers led by Dzmitry Tsetserukou of Skoltech have created a drone with legs, which can stop the propellers and move at a walk after landing. The drone itself was developed as part of another effort in 2018 when engineers were creating a multi-copter with the ability to land on uneven surfaces. It is based on a DJI F550 frame with a Naza-M flight controller, and the authors installed four legs on the lower part of the body. They are assembled from two long sections and one short "stop". In the" hip "and" knee "sections are connected by servomotors with torque sensors, and above the "foot" is a passive joint.

Kinematic diagram of the robot / Grigoriy Yashin et al. / IEEE Journal on Miniaturization for Air and Space Systems, 2020

The authors developed a walking mode for the robot, which they compare to walking a person with a broken leg on crutches. In this mode, the robot stands with two opposite feet along the direction of walking. Then he first leans back, moves the front leg forward and shifts the centre of mass, and then Vice versa leans forward and attracts the back leg. Simultaneously with the transfer of the centre of mass, the side legs move. All legs in this mode move along parabolic trajectories, which helps to step over obstacles.

One drone walk cycle. The points indicate the original places where the feet came into contact with the surface / Grigoriy Yashin et al. / IEEE Journal on Miniaturization for Air and Space Systems, 2020

Engineers tested the performance of the algorithm on the robot and during experiments found out that it is most efficient to move the legs so that the centre of mass is shifted along a cycloid trajectory. They also checked the accuracy of the robot's movements by giving it a command to move along a given trajectory and comparing the results with calculations. Tests have shown that the accuracy (standard deviation) of the step length reaches 9.8 millimetres (with a step length of six centimetres), and the accuracy of following the direction is nine degrees.


Another feature of the drone is the ability to land on uneven and sloping surfaces by placing your feet at an angle. Recently, Canadian engineers also taught a drone to land on a sloping roof, but in a different way. Immediately after touching the surface, the drone turns on reverse thrust and presses itself to the surface to avoid high bounces after the first contact.


Photo: Grigoriy Yashin et al. / IEEE Journal on Miniaturization for Air and Space Systems, 2020

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