The principle of the camera stabilization using brushless direct drive motors
- In fact, gimbal based on BLDC motors is very similar to regular gimbal based on hobby servo. The main difference - each axis of rotation passes through the center of gravity (CG) of the "Camera + frame" system and rigidly connected to the BLDC motor. The absence of gear - a fundamental point that lets you use the inertia of the system is not to harm, but for good. In case of ideal balance of the camera, the rotor rotates freely without resistance and even without need of applying extra control force, which allows the camera to unleash from the disturbance from UAV frame. In addition, there is no backlash inherent gears or belts.
BLDC motor works not in its usual mode, but as an DC-electromagnet generating high torque to hold camera. Therefore it is NECESSARY to rewind motor with thinner wire to increase its resistance and torque. Recommendations for winding motors of different sizes are collected in section Electronic / Motors.
To control the motors, a special controller was designed. It receives information from gyroscopes and accelerometers mounted on the camera platform. A standard IMU algorithm is used to define camera inclination angles. With the remote control, operator sets desired tilt angle. PID-controller calculates the amount of compensation and send command to the power unit, which controls the current in the windings and thus the direction of the vector of magnetic field in the stator. Magnetic field moves the rotor to the right position.
- Due to using IMU, mechanical part of the
system is a very simple. There is no need in complex and expensive
high-definition encoders for each axis. Just mount tiny IMU board
on the camera platform, connect wires to controller and motors and
It will give impressive quality of stabilization compared to regular servos.
- The possibility of precise balancing on three axes. The better the balance, the lower the current need for stabilization.
- Mechanical rigidity of bearing elements to prevent resonances from working propellers in flight
- Minimizing friction in the joints. The better the gimbal axis are unleashed from UAV camera platform, the less effort is required from the engine to stabilize
Elimination of vibrations from the main UAV
frame. The vibrations have a negative
impact on the quality of the video. But another negative effect in
this system is that vibration will lead to self-excitation of the
Many mechanical solutions can be found in the Mechanics section. Some solutions are accompanied by drawings and tips for assembly.