Research On Control Algorithm Of Quadrotor

The quadrotor has the characteristics of nonlinearity,under-actuation and strong coupling.It is widely used in civil and military fields,such as electric power inspection,forest fire prevention,community security,etc.It brings new changes to human life and has important research value and significance.The working environment of the quadrotor determines that the object needs high precision,robust control algorithm to achieve its control,and the control algorithm should also have a certain degree of anti-interference and fault tolerance.In this paper,the quadrotor was used as the research object and the control algorithm of the quadrotor was studied.The control algorithm was designed for different external and internal disturbance problems.The main work is as follows:1.The mathematical model of the quadrotor was established,and the dynamic analysis of the quadrotor was carried out.Based on the Euler-Lagrange method and the Newton-Euler method,the dynamic model of the quadrotor was established.The Euler-Lagrange method is the most extensive modeling method.The Newton-Euler method considers the coupling relationship of attitude variables in attitude modeling.In the subsequent control algorithm design,the dynamic model was selected according to the specific control requirements.2.Aiming at the problem that the quadrotor is susceptible to external low frequency disturbance during flight,a disturbance observer based control algorithm was proposed according to the disturbance frequency.Considering the slow time-varying disturbance problem,the generalized proportional integral control based on the slow time-varying disturbance observer was proposed.The gyro effect of the quadrotor dynamics model was neglected.The slow time-varying disturbance observer can estimate the slow-time-varying disturbance value and provide disturbance compensation for the generalized proportional-integral controller.Generalized proportional integral controller can realize stable control under slow time-varying interference.Considering the increase of the disturbance frequency and the obvious change of the disturbance value,the fuzzy sliding mode control based on the nonlinear disturbance observer was proposed to establish the underactuated subsystem model considering the blade force.The nonlinear disturbance observer can realize the large frequency disturbance.The estimation of the fuzzy sliding mode control algorithm can avoid the sliding mode chattering problem caused by the tracking error in the traditional sliding mode control.The simulation results show that the two control algorithms based on the interference observer can achieve the desired control performance requirements.3.An attitude control algorithm based on robust differentiator was proposed for the quadrotor attitude system to be interfered by the high frequency external noise disturbance.The frequency domain performance analysis of the robust differentiator and other traditional differential trackers shows that the robust differentiator can achieve smooth filtering and accurate derivation of the signal.A PID(proportion integral derivative)control based on robust differentiator was proposed.The influence of different noise intensity on the attitude control of the quadrotor was considered,and the attitude angle and attitude angular velocity of the quadrotor were controlled.The simulation results show that the designed control algorithm can resist the influence of noise on the attitude control of the quadrotor.4.Aiming at the problem that the external noise disturbance environment and internal state feedback do not accurately affect the tracking accuracy and flight safety of the quadrotor,the control algorithm was designed by the linear active disturbance rejection control and nonlinear active disturbance rejection control switching.The stability analysis of the active disturbance rejection control algorithm proves the rationality of using the control algorithm.An ADRC(active disturbance rejection control)switching control based on robust differentiator was proposed to apply white noise of different intensity to four-rotor aircraft objects.The robust differentiator has the ability of signal filtering and derivation.The ADRC switching control switches the controller to improve the control precision and convergence speed according to the different characteristics of the linear extended state observer,and the nonlinear extended state observer.Extended state observer enables fault-tolerant control without angular velocity feedback.The simulation results show that the control algorithm has the anti-interference ability under the white noise environment,and can realize the tracking control of the desired trajectory of the quadrotor.