Research On Attitude Measurement And Control Technology Of Multi-rotor Aircraft

With the development of micro-electro-mechanical technology and the needs of scientific research and production and life,multi-rotor aircraft have been widely used in the fields of agricultural plant protection,emergency rescue,space exploration,aerial photography and entertainment.The attitude measurement and control strategy of the multi-rotor aircraft is the basis for its stable and safe flight.This paper focuses on the attitude measurement and flight control methods of multi-rotor aircraftIn this paper,the experimental platform of multi-rotor aircraft is built to provide experimental platform and theoretical basis for information fusion and control method research.The six-degree-of-freedom nonlinear control model and the actuator model of the multi-rotor aircraft are established.Based on the principle of attitude solution of inertial sensor,the inertial sensor used in the experimental platform is calibrated by the unsupported calibration method.According to the nonlinear state model of attitude fusion system,the problem of model linearization is solved by using trackless kalman filter,the estimation of horizontal position information fusion is made by using accelerometer and GPS,and the combination of ultra-sonic sensor and barometer is introduced to realize the height information fusion.Secondly,the multi-rotor dynamic model is decoupled into three linear models of translation,height and attitude through the linearization of the multirotor aircraft system model.Based on the analysis of the stability and controllability of the multi-rotor system,an improved PID control method with guaranteed direction saturation function is proposed to avoid controller saturation and loss of control.Finally,the robust output feedback tracking controller based on ESO is designed by sliding mode differentiator,which fully considers the parameter uncertainty and external inter-ference of the multi-rotor vehicle,and improves the trajectory tracking accuracy of the control systemThe main innovations of this paper are as follows1.The multi-sensor layered fusion pose estimation algorithm is proposed.Aiming at the characteristics of high frequency noise,cumulative drift and pose fusion state model of the inertial sensor,a three-level combined information fusion algorithm is proposed,which divides the pose information fusion system into three parts:pose fusion,horizontal position fusion and height information fusion.According to the nonlinear characteristics of the attitude solu-tion model,the linear process of equation of state is effectively avoided by using the unscented kalman filter(UKF)JIS algorithm.According to the linear model of the fusion of accelerom-eter and GPS position information,the measured value of accelerometer is taken as the input control quantity of the equation of state,and the horizontal position information is predicted effectively.In order to improve the accuracy of height information,the weighted algorithm of disperse kalman filter is used to combine the measurement information of ultrasonic sensor and barometer.The method can not only reduce the vector dimension of pose state space but also improve the fault tolerance of the measurement system2.A nonlinear PID control method with guaranteed direction saturation function is proposed.Aiming at the condition of the large Angle will lead to flight controller saturation,ig-nored in the process of mathematical modeling of the system interference,saturation and other factors will directly affect the control system performance and even cause controller failure,the combination of multiple rotor aircraft,the coupling characteristics of the underactuated USES improved cascade of double closed loop PID control algorithm,using the velocity error respec-tively designed position and attitude control,on the basis of this controller direction saturated function is required,and the stability of the closed-loop control system is demonstrated.This method not only weakens the saturation effect,but also ensures that the output trajectory is in the same direction as the desired trajectory.Matlab/simulink was used to model the four-rotor system,and the simulation verified that the method could meet the trajectory tracking control requirements of the aircraft3.A trajectory tracking control method based on robust output feedback strategy is pro-posed.Aiming at the parameter uncertainty and external disturbance of the multi-rotor,the unmeasurable states in the rotating subsystem are reconstructed by the extended state observer(ESO)method,and the first-order dynamic sliding mode differentiator(SMD)method is used to compensate the system disturbance.This method avoids the tedious calculation,establishes the robust output feedback tracking controller based on ESO,realizes the stable trajectory tracking control of the multi-rotor aircraft under the condition of parameter uncertainty and composite interference,and guarantees the asymptotic stability of the aircraft in a large range.Numerical simulation is carried out to verify the effectiveness and superiority of the proposed control strategy.