How can a drone with 4 propellers (as in the photo) fly forwards or backwards. I think the propellers are all on the same level. There is then no propelling movement.
In: Engineering
As others have pointed out, it’s done with independently variable thrust, i.e. Making the propellors turn at different speeds, causing the drone to tilt in one direction.
This is also why 4 (or more) propped drowns are so dominant: using this system you can have the drone move in all 6 degrees of freedom without needing a single movable part (aside from the rotors themselves obviously)
While hovering, it is exactly how you described. But when going forward, the rear rotors speed up and the whole drone pitches forward a bit. Usually the drone has some sensors to measure the angle and holds it automatically. Because it is no longer level, the drone now flies forward and downward. The downward motion can be countered by increasing the rpm on all 4 motors simultaneously
If the rear two provide more lift than the front two, the drone will tip forwards.
Now the direction of thrust isn’t just straight down, it’s down and back. This pushes the drone forwards.
Some more complex drones can pitch the rotors themselves to direct thrust like a helicopter.
Two blades spin faster than the others causing it to tilt. This gives directional thrust. This is the same as a conventional helicopter except it achieves tilt by literally tilting its prop.
To move forward the propellers in the front slow down, causing the front to tip downward and all 4 propellers then aim forward. To fly backwards, the opposite.
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