Physics

Control engineering

Settling time

Nonlinear system

Variable structure control

Mathematics

Sliding mode control

Agronomy

Biology

Operating system

Engineering

Step response

Mathematical analysis

Artificial intelligence

Controller (irrigation)

Control (management)

Observer (physics)

Computer science

Mode (computer interface)

Quantum mechanics

State observer

Sign function

Control theory (sociology)

Lyapunov function

IEEE Transactions on Aerospace and Electronic Systems

In this article, a study of the appointed fixed time control problem is presented for the quadrotor unmanned aerial vehicle attitude control system subject to external disturbances. Based on the appointed fixed time sliding mode variable and the adaptive technique, a novel sliding mode observer is first established to estimate the external disturbances within the appointed settling time. Subsequently, an appointed fixed time controller is proposed to track the desired attitude regardless of the initial states. To circumvent the singularity problem of the above controller, a novel improved adaptive sliding mode control law is designed by employing a nonlinear function and a modified sliding mode observer. Moreover, the chattering phenomenon is attenuated by replacing the sign function with hyperbolic tangent function. The appointed practical fixed time stability of the closed-loop attitude control system is proved and analyzed rigorously utilizing the Lyapunov theory. Finally, the effectiveness and fine performance of the proposed schemes are illustrated by numerical simulation results.

Appointed Fixed Time Observer-Based Sliding Mode Control for a Quadrotor UAV Under External Disturbances