← Robot list · Robots in the real world course
Turn the robot with the mouse or your finger. Click an axis (a coloured circle or a card) to light up its ring and its axis and to read its description, press X-ray to look inside at the motors, gearboxes, controller and cables, and move each joint with its slider.
Move the sliders like the sticks of a remote control. At zero the drone hovers where it is.
Four brushless motors, each with a propeller. Two turn clockwise and two anticlockwise, so that the torques cancel in hover. Thrust grows with the square of the speed.
A light X frame (carbon fibre or plastic) that holds the motors at equal distance from the centre and carries the landing legs.
The brain: it reads the gyroscope and accelerometer (IMU) hundreds of times per second and corrects the four motor speeds to keep the attitude. Seen in X-ray.
One electronic speed controller per motor turns the battery current into the three-phase current of the brushless motor. Seen in X-ray.
A lithium-polymer pack: the heaviest part and the limit of the flight time (10 to 30 minutes). It sits under the centre to keep the drone balanced. Seen in X-ray.
GPS and compass for position, barometer for altitude, and here a camera on a gimbal. Other drones carry lidars, sprayers or packages.
The drone really flies: a rigid-body simulation (mass 1.2 kg, thrust-to-weight ratio 2) with a flight controller and a mixer that turns your four commands into the four motor thrusts. Roll and pitch are target angles: to go sideways the drone has to tilt first, because it is underactuated (6 degrees of freedom, 4 motors). The two blue propellers turn one way and the two white ones the other way, so that their reaction torques cancel; the yaw command makes them unequal. The model is simplified.