I’m new to working with drones and realized I don’t fully understand how they move forward.
From what I’ve learned, to move forward, the front motors reduce thrust (or the back ones increase thrust), tilting the drone forward. This creates a horizontal force that moves it. I also get that this tilt happens because the thrust change creates a torque, tilting the drone forward.
But here’s where I get confused: once the drone reaches the desired tilt angle, do the thrusts go back to their original values to stop rotation and hold the angle steady? Or do the front and rear motors keep a thrust difference even after the tilt is achieved? If they keep the thrust difference, wouldn’t that still cause a torque and make the drone keep rotating?
If I’m correct that the thrusts return to balance, could I use the drone’s thrust values, its mass, the tilt angle, and air resistance to calculate the distance it travels in a certain amount of time? If not, can someone explain why? And if the thrusts don’t return to balance, how does it stop rotating?
You might be overthinking this. The back motors speed up to tilt the drone forward, and the front motors stop it from flipping all the way over. Once it tilts, the only direction left for it to go is forward.
So, if I understand right, there’s still a small thrust difference between the front and back motors, but it’s so minor that it doesn’t keep rotating the drone? Does that sound correct?
And about the theoretical calculation—how can I use the thrust, mass, tilt angle, and air resistance to figure out how far the drone would go in a set time?
@Chen
If you’ve got all the variables, you could definitely calculate it. Or you could just check the GPS and get a much simpler answer. You might be overcomplicating something that doesn’t need that much effort.
@Chen
Yeah, the rotational forces are balanced because of the way the propellers spin in opposite directions. The drone’s controller adjusts them as pairs to maintain stability. When the back props increase thrust, one spins clockwise and the other counterclockwise to keep things steady.
As for the math, I’ve got no clue! Some days I’m just happy I remember to breathe, honestly.
You’re mostly right. To start tilting forward, the back motors speed up and the front motors slow down, creating a torque that pitches the drone downward. This causes it to rotate. Once it’s rotating at the desired speed, the motors balance out so there’s no more torque, but the rotation continues because of inertia. When the drone approaches the desired tilt angle, the front motors speed up and the back motors slow down to create a torque in the opposite direction, slowing the rotation until it stops at the angle you want. At that point, the drone’s thrust at an angle gives it forward movement.
You’re right that the back motors speed up compared to the front ones to tilt the drone and create forward movement. But it’s not as simple as setting the speeds once and leaving it. The drone has sensors that constantly monitor its tilt angle and adjust the motors to keep it steady. These same sensors also keep the drone level when it’s hovering.
For rotation, the diagonal pairs of motors adjust their speeds. For example, the front left and back right props spin one way, and the other diagonal pair spins the opposite way. By changing the speeds of one pair relative to the other, the drone can turn without affecting its stability.