Research On Attitude Control System Of Handheld Camera Stabilized Gimbal

In recent years,with the continuous development of electronic technology,The application of unmanned aerial vehicles(UAV)has begun to expand from military to industrial and civil fields,The small multi rotor aircraft used for aerial photography has been widely used as a representative.To make the airborne camera get a stable image,a 2 or 3 axis stabilized gimbal is usually needed to isolate the change of the body’s attitude,the same problem is also faced in handheld camera.In this paper,the key problems in the attitude control of the handheld camera 3 axis stabilized gimbal are studied and the solutions are put forward.First,the main system structure of the stabilized gimbal is introduced and its working principle is analyzed.The main factors affecting the stability of the gimbal are also analyzed and the main methods to control the stability of the gimbla are put forward,whitch are attitude detection of the gimbal and the attitude control of the gimbal through the motor;Attitude detection module consists of three axis accelerometers,three axis gyroscopes and three axis magnetometers to collect attitude data in the attitude detection of the gimbal.The collected gyroscope data are processed by quaternion and fused with the other two sensor data,and the Euler angle of the gimbal with the earth as the reference coordinates is obtained;In view of the attitude motion control of the gimbal,the brushless DC motor is used as an actuator.The field oriented control(FOC)algorithm based on coordinate transformation is used as the control strategy of the motor.Some key links in the process of FOC have been solved,include measurement of rotor position by using a non-contact magnetic encoder and the acquisition of stator current by using a digital current sensor.The motor is driven by space voltage vector pulse width modulation(SVPWM).The simulation and experimental results show that the scheme is feasible.Besides,it can simplify the design of the circuit so that the size of the circuit board can be reduced and fit to the motor;In the process of the whole design of the system,the modularization design idea is adopted.Whitch is individual design of attitude detection module and motor control module.They communicate through UART serial port,which improves the reliability and expansibility of the system.In this paper,an experimental prototype of handheld stabilized gimbal was designed and made.For the attitude detection module,the results show that the full attitude detection of the gimbal is realized.The fluctuation range of each attitude angle is less than ±0.2° at rest.For the motor control module,the torque ripple is smaller.The overshoot is less than 5% of the step response of the speed.It is good to follow the reference angle and the positioning error at rest is less than 0.1°.