Research On Modeling And Control Method Of Moving Mass Quadrotor UAV

The moving mass control technology realizes the change of the mass center of the system by changing the position of the mass block installed in the aircraft,and makes the position vector of the combined force acting on the aircraft change with respect to the position vector of the center of mass of the aircraft system,thus changing the moment of the combined force relative to the center of mass of the aircraft to realize attitude maneuver.The control technology of moving mass has been put forward in the last century,and has been fully studied by researchers.It has a broad application prospect in rolling control of high speed reentry vehicle.The research in China started late,mostly in the modeling and simulation stage,so the development of the verification prototype is the basis of the application of moving mass technology.The four rotor is low cost,can realize fixed-point hover and low requirement on the site.It can be used as a demonstration and verification platform of the control technology.This paper provides theoretical support for demonstration and verification of the control technology on the four rotor UAV through simulation research.Firstly,the translational dynamics model of the three slide masses for four rotor UAV in the earth fixed coordinate system is established by Newton Euler vector mechanics.The dynamic model of the center of mass rotation around the system is obtained by the momentum moment theorem,and the translational and rotational kinematic models are derived.The same as the conventional four rotors,the pull force is generated by the rotor,the difference is that the control torque is produced by the joint cooperation of the rotor and the slider.Therefore,a compound control allocation algorithm of rotors and slides is designed.In order to control the supported test platform,the dynamic model is simplified reasonably.Based on the simplified mathematical model,the simulation analysis of the control capability of the single slide moving mass four rotor UAV is carried out.Then,based on Radau pseudospectral method,the shortest time trajectory optimization of four rotor UAV to the designated position is carried out.The optimal trajectory of three degrees of freedom is obtained by taking the pull force and the attitude angles as the optimal control variables.The six degree of freedom trajectory optimization is carried out by taking the force and the moments as the optimal control variables.Finally,the fixed-point hover controller is designed by PD control.The simulation results show that the time of hovering to the designated position by optimal control is less than that of PD control.Finally,the standard trajectory tracking control law is designed for real-time tracking given the standard trajectory by using the simplified single slider moving mass four rotor dynamics model in Chapter 2.The command attitude angle is calculated by the outer loop of the trajectory,and the command attitude angle is sent to the internal loop of attitude control for tracking.The command angular velocity is obtained from the command attitude angle,and then the angular acceleration tracking command angular velocity is designed based on the theory of inverter sliding mode structure.The simulation results show that the proposed algorithm can track the given spiral standard trajectory stably.Based on the backstepping control,the rotor total pull and moments are designed to track the outer loop trajectory and the internal ring command attitude angle.The simulation results show that the controller accuracy meets the requirements,and the results are compared with the sliding mode inverse control.In view of the problem that the output of the actual actuator has the upper limit,a tracking controller considering the saturation of the actuator is designed,and the output lower bound of the actuator is given when the specified trajectory is tracked stably.