Research And Design Of A Nap-of-the-earth Quadrotor

With the flexible maneuverability and less geographical limitation,quadrotor has been widely used in military applications,aerial mapping,plant protection,scientific research,and etc.Aiming at the application of personnel search,for example after earthquake,and accurate detection in dangerous environment,a nap-of-the-earth autonomous exploration quadrotor is designed.The following main work has been carried out.First,in order to guarantee the validity of exploration,nap-of-the-earth flying requires the quadrotor not only be as close to the ground as possible,but also be able to follow the contour the land surface.By means of the high precision in short distance measurement,the height of the quadrotor to the ground is obtained by the ultrasonic sensor.The first-order low-pass filtering based on the dynamic change of the coefficients is used to process the height data.The double closed-loop PID control of altitude-velocity is adopted to effectively resist the interference.As the result,the quadrotor can stably fly at a given height from 3cm to 50 cm.Second,to autonomously detect complex environment,quadrotor is required to be able to autonomously navigate based on a given route.For this purpose,feedforward cascade PID control is used as the core controller.Considering the modeling error and channel coupling,Linear Active Disturbance Rejection Control(LADRC)is adopted to improve the stability and anti-jamming ability of navigation control.Multi-rate Kalman filter algorithm is used to fuse the data from GPS and accelerometer,which improves the accuracy of positioning and velocity measurement.Third,the real-time obstacle avoidance of the quadrotor is also studied.Aiming at two disadvantages of the traditional artificial potential field methods— local minimum point and unable to combine with a given route,the gravitational potential field and repulsion potential field are improved.A three-dimensional obstacle avoidance method based on improved artificial potential field is proposed.The ADAMS simulation results indicate that the algorithm can realize the real-time obstacle avoidance based on a given route.Finally,the system structure of the quadrotor is introduced in this paper.The operation performance of the quadrotor is tested.The results show that the quadrotor can realize all the functions of nap-of-the-earth autonomous exploration.