Reverse thrust helped drone to land on an inclined surface

Canadian engineers have taught the drone to take the surface inclination angle up to 25 degrees. This drone immediately after touching the surface begins to rotate the propellers in opposite direction with maximum thrust. This allows him to quickly repay the Bouncing after landing and stay, say the authors of the article in the IEEE Robotics and Automation Letters.

Almost all drones are designed for landing on a smooth horizontal surface, they even sold folding mats that can be put on uneven ground with bumps or hollows. When boarding drones are often a little bounce after the first touch, and if the landing takes place on an uneven or inclined surface, this Bouncing can cause the drone will begin to shift to the side and either stay there, where he hoped the pilot either rolls over or touches the ground with screws.

There are projects in drones, capable of landing in such conditions that are hooked on the protrusions movable legs or areas with microseepage. But these mechanisms take the drone of the already low weight of the payload, and they are difficult to independently establish on common civilian quadcopters.

John bass (John Bass) and Alexis Lussie of Debian (Alexis Lussier Desbiens), working at Sherbrooke University have proposed a solution that potentially can be applied to many of the quadcopters without hardware modifications: after touch to transfer the motors in reverse mode to pull the screws pushed the drone to the surface. The drone uses a separate algorithm that is activated when the accelerometer detects an overload from 2g and above.

They used a modified DJI F450 quadcopter with long legs that when planting reversible bend and waver. The developers have created a model drone, which describes all its segments. In particular, it reflects the behavior of the legs during landing, describing them as separate segments attached to the main body of the apparatus through the spring. In addition, they created two separate models contact foot surfaces for surfaces with strong and weak grip.

Engineers tested first in simulation and then on real Dhron two algorithms. First after planting softens the rebound from the surface by shutting down the engines, and the second translates them into reverse mode with maximum thrust. Experiments have shown that the rotation of the screws in the back allows you to land the drone at a higher slope: 25 degrees on the surface with low friction and 20 degrees on the surface with high. In this simulation, the numbers were even higher.

The developers changed not only the degree of slope, but the rate of descent before touch the surface. The experimental data fairly well agreed with the results of the simulations revealed a threshold speed, after which the probability of a successful landing is sharply reduced. For surfaces with low grip, it is approximately 1.2 meters per second, and for a surface with a high threshold is much lower — 0,8-1 meter per second.

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