Calibration of Swashplate for a Helicopter with Vision Based Measurements

In an eCCPM helicopter, at least three servos have their movement combined together to control the swashplate. All of these servos are small in size and driven by pulse width modulated (PWM) signals. In the model to control a miniature unmanned helicopter, the swashplate is a very important module. This paper proposes a partial linear method to calibrate the swashplate of an eCCPM helicopter. The method linearizes the mechanism of swashplate and obtains a calibration matrix. The goal is to achieve the conversion calculation between PWM signals and the output angles of swashplate, which contain the collective pitch angle, the elevator angle and the aileron angle. This paper utilizes image recognition technology to measure the output angles of swashplate. Experimental results show that this partial linear calibration method has small error and no singularity, and performs excellently in actual flight.