State Observer-Based Formation Tracking Control for Multiple Quadrotors

A distributed finite-time formation tracking control strategy based on a state observer is proposed for a group of under-actuated quadrotors, where only a part of the quadrotors can directly obtain the state information of the leader quadrotor. According to the strict feedback architecture of the quadrotor system, the dynamic model of the quadrotor is divided into the position and attitude subsystems, from which the position and attitude controllers are designed, respectively. First, given that not all quadrotors can communicate with the leader and obtain its state information under the condition of using a distributed formation control strategy, the distributed finite-time state observer is designed for each quadrotor to estimate its relative state information and that of the leader quadrotor. The stability analysis shows that the error of the state observer can reach zero in finite time. Second, a finite-time position controller is designed based on the observed results of the state observer. The stability analysis shows that the position controller can achieve stable tracking of the position of the leader quadrotor in finite time. Based on this finding, the desired attitude angle can be calculated according to the values of the position controller, and the attitude controller can be designed using the sliding mode control method. The stability analysis shows that the desired attitude angle of each quadrotor can be tracked in finite time. Finally, the simulations results show that the error of the designed state observer can reach zero in finite time, indicating that the state observer of each quadrotor can obtain the relative state information between itself and the leader quadrotor in finite time. The flight trajectory of each quadrotor can be used to generate and maintain the desired formation in finite time. © 2019, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.