A Subminiature Aerocraft With Autonomously Flying Capability

In recent years,Micro-Electro-Mechanical System,computer technology and automatic control theory have been greatly developed.Benefit from it,unmanned aerial vehicles,especially multi-rotor aerial vehicles,are gradually developing towards miniaturization,intelligence and clustering.As the most common multi-rotor aerial vehicle,the quadcopter has a simple mechanical structure and simple control methods,it can take off and land vertically,and hover in the air.Nowadays,the quadcopter has been widely used in military and civilian fields.In this paper,a subminiature quadcopter is designed,which can fly autonomously along the planned path,based on the quadcopter autonomous flight control technology.Firstly,this paper introduces the development history and research status of unmanned aerial vehicles.Then according to the basic structure and working principle of the quadcopter,this paper puts forward the technical indicators and design scheme,and introduces the design and implementation of the quadcopter from both hardware and software.Secondly,the attitude and position estimation algorithm are studied.The complementary filtering algorithm is adopted for the attitude estimation.It fuses the data of gyroscope,accelerometer and magnetometer to calculate the rotation quaternion.And then the rotation matrix and the attitude angles of the quadcopter can be obtained with quaternion.The Kalman filtering algorithm is adopted for the position estimation.It fuses the data of accelerometer,optical flow sensor,barometer and laser ranging sensor to calculate the displacement and velocity of the quadcopter by the state equations.Thirdly,the control algorithm of the quadcopter is studied.The position and attitude of the quadcopter are both controlled by two-stage cascade PID control algorithm.The position controller consists of a displacement controller and a velocity controller,and the attitude controller consists of an angle controller and an angular velocity controller.Finally,the path tracking algorithm of the quadcopter is studied.The quadcopter acquires the longitude and latitude information from GPS and altitude information from position estimation algorithm.Comparing them with the planned path,the quadcopter acquires the off-course information.And then,the quadcopter controls the flight direction by the PID control algorithm to track the path,so that the quadcopter can fly autonomously along the planned path.The experimental results show that the attitude and position estimation algorithm designed in this paper can provide relatively accurate attitude and position information for the quadcopter.In addition,the actual flight trajectory of the quadcopter is basically consistent with the planned path,which verifies the effectiveness of the flight control algorithm and the path tracking algorithm.