BaseCam (AlexMos) SimpleBGC
The controller can be used for building
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.
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 all done!
It gives impressive quality of stabilization compared with regular servos.
Basic requirements for the mechanical design of gimbal frame
- 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 closed-loop controller.
Size of the controller, mm
The controller specifications
|Number of stabilization axes||2|
|Power supply voltage:||8..18V (3s-4s LiPo)|
|Maximum DC current to each motor||2.8A|
|Output current regulation:||8 or 32 KHz PWM|
|PC communication for configuration and upgrade:|
|Reverse polarity protection:||Yes|
|Dimensions:||50mm x 50mm (see drawing)
|Mounting holes:||M3, 45mm
To setup the controller, a special GUI is used. The complete setup procedure is described in the user manual.