A robust tiny flapping mechanism and an adaptive attitude estimation strategy design of a micro aircraft under high frequency vibration

The high frequency flapping motion contributes to the lift generation of micro aircraft, but it sets higher standards for the mechanism design and attitude estimation. The flapping mechanism needs to be robust, but light to generate a constantly time-varying force to balance the weight. This force could also cause a significant flapping acceleration disturbance to the attitude sensor, accelerometer, even in steady status. In this paper, a crankshaft slide rail flapping mechanism is designed and it has advantages in terms of weight, volume and number of parts used. Its kinematic formula is deduced and a perfect symmetric flapping trajectory is proved to be generated. This mechanism has been proved to be efficient in actual flight. Based on the deduced kinematic formula of the flapping mechanism, the flapping motion can be obtained and it is input to the aerodynamic model. The flapping acceleration can be solved and is utilized to compensate the flapping acceleration disturbance of the accelerometer. The residual of the compensated flapping acceleration is further adapted by the harmonic based adaptive estimation for its periodic part and the covariance based adaptive compensation for its random part. The proposed attitude estimation strategy with flapping acceleration compensation and adaption is compared with other methods and proved to be more accurate in both offline test and closed loop test.