Research on a Robust Backstepping Attitude Controller for Multi-rotor Plant Protection UAV

The plant protection UAV is an important application equipment for precision spraying technology. However, in the process of spraying, the change of its own load will lead to the decline of control performance and disturbance rejection ability. In order to improve the control performance of the plant protection UAV, the application research of robust backstepping control strategy is carried out, and the Robust Backstepping Attitude Controller (RBAC) is designed to force the quadrotor to follow the desired attitude. Through simulation experiments, the control effect of RBAC and the Backstepping Terminal Sliding Mode Controller (BTSMC) in the literature are compared and analysed. The simulation results show that: RBAC can improve the dynamic performance of the system. The average settling time of the system is shortened by 404.663ms, which is 24.85% faster than that of the BTSMC system. Simultaneously, the system is insensitive to external unknown disturbance and has strong robustness.

Active disturbance rejection attitude control of unmanned quadrotor via paired coevolution pigeon-inspired optimization

Purpose The purpose of this paper is to develop a novel active disturbance rejection attitude controller for quadrotors and propose a controller parameters identification approach to obtain better control results. Design/methodology/approach Aiming at the problem that quadrotor is susceptible to disturbance in outdoor flight, the improved active disturbance rejection control (IADRC) is applied to design attitude controller. To overcome the difficulty that adjusting the parameters of IADRC controller manually is complex, paired coevolution pigeon-inspired optimization (PCPIO) algorithm is used to optimize the control parameters. Findings The IADRC, where nonlinear state error feedback control law is replaced by non-singular fast terminal sliding mode control law and a third-order tracking differentiator is designed for second derivative of the state, has higher control accuracy and better robustness than ADRC. The improved PIO algorithm based on evolutionary mechanism, named PCPIO, is proposed. The optimal parameters of ADRC controller are found by PCPIO with the optimization criterion of integral of time-weighted absolute value of the error. The effectiveness of the proposed method is verified by a series of simulation experiments. Practical implications IADRC can improve the accuracy of attitude control of quadrotor and resist external interference more effectively. The proposed PCPIO algorithm can be easily applied to practice and can help the design of the quadrotor control system. Originality/value An improved active disturbance rejection controller is designed for quadrotor attitude control, and a hybrid model of PIO and evolution mechanism is proposed for parameters identification of the controller.

Robust Attitude Controller for NASA Astrobee Robots Operating in the ISS

Free-flying robots have been recently developed to operate on-board the International Space Station (ISS) as semi-autonomous robotic assistants. NASA Astrobee robots are the new free-flyers proposed by NASA, and equipped with a 3 degree of freedom manipulator. This research aims to realize an accurate mathematical model of the robot attitude dynamics, and an attitude controller for the NASA Astrobee system. The robot has been modeled coupling the attitude dynamics with the manipulator motion, and robust attitude controllers are proposed to stabilize disturbances and configuration changes induced by the manipulator usage. First, a second-order twisting sliding mode controller is designed to achieve a trade-off among control law flexibility, robustness and accuracy. Among robust control strategies, sliding mode controllers are characterized as low complexity, and low computational cost control methods, making the system able to achieve reactivity and stability also when parameters are changed. The performance of the proposed control method are compared with a backstepping controller that include an iterative algorithm to compute an adaptive control, as function of disturbances and orientation error. The performance are evaluated and analyzed considering several scenarios in Matlab Simulink simulations, and combining Simulink and ROS Gazebo to run co-simulations with the NASA Astrobee simulator. Simulations with variable body mass, links masses, and different gripped objects have been run to test the controllers performance in off-design conditions.