You want to buy a quadrocopter?
We would like to explain briefly what a Quadrocopter is and what you should pay attention to the when buying a quadrocopter. A quadrocopter is a multicopter with four rotor blades. These are usually driven by brushless DC motors, which are at the same height level. Two rotors turn clockwise, the other two counter-clockwise. This allows the quadrocopter to start and land vertically. These motors are installed at the end of the four jibs and a lithium-polymer battery is usually used as a source of energy.
Construction of a quadrocopter:
Quadrocopters can be constructed in different ways. Although the air screws are all at the same level, the booms, and therefore also the motors, can either be arranged in Plus (+) or in the X or H shape. In the first case, a simpler control is possible because only one pair of motors is used in the case of control change of the longitudinal or transverse axis. The situation is different with the X and H arrangement, because the motors are offset by 45 degrees in the direction of a boom and in the direction of flight. Therefore, all four motors must be used at the same time. However, this is only a small drawback, since this can result in higher torsional accelerations. In addition, this design is more suitable for cameras – it offers a larger field of view since no propellers disturb the view.
Another, but much more rare, design is the Y4 shape. The structure is similar to a tricopter. Two booms move forward from the fuselage. At the rear, two rotors are arranged centrally and behind each other. The shape is similar to a “Y”.
How is the Quadrocopter controlled?
The lift and drive is achieved by increasing or reducing the rotational speed, which in turn leads to a rise or fall. As already mentioned, two of the four rotors rotate counterclockwise. This is necessary to neutralize the occurring forces of the propellers on the fuselage. A well-dimensioned Quadrocopter should take off at medium rpms – only then are there adequate power reserves available in case of need for maneuvering.
Each aircraft has three axes: the vertical axis, also known as the yaw axis, the longitudinal axis and the transverse axis. All flight maneuvers depend on one or more of these axes.
If the quadrocopter is to be rotated about the vertical axis, different forces must act on the aircraft. For this purpose, the neutralized forces of the propeller rotating left and right must produce an imbalance. In other words, the rotational speeds of the left-hand and right-hand rotating air screws must be proportionally different.
In order to initiate a clockwise rotation around the longitudinal axis, the rotational speeds of the drives located to the left of the longitudinal axis must be significantly higher. In addition, the rotational speeds of the drives located to the right of the longitudinal axis must be proportionally reduced. The sum of the resulting forces must not change, otherwise the tail will break. These details apply to the Plus design.
Fortunately, intelligent control and stabilization electronics with gyroscopes take over the control of the motors and enables even beginners to fly quadrocopters. While the stern of a helicopter must be constantly corrected for a drift, this is not necessary with a quadrocopter. Even more sophisticated flight maneuvers such as reels, tight turns and even loops can be performed with some quadrocopters, depending on the control mode. There are two control modes, the three-gyro heading hold mode (HH), which is more difficult to fly but allows all flight maneuvers, as well as the ACC mode. It requires an additional acceleration sensor and aligns the aircraft horizontally when the joystick is centered. In order for the pilot to better recognize the flight direction of his quadrocopter on a distance, color propellers are usually used.