Abstract
This paper presents a new control approach for the trajectory tracking of a quadrotor in the presence of external disturbances. Unlike in previous studies using hierarchical control strategies, a nonlinear controller is designed by introducing new state transformations that can use Euler angles as virtual control inputs. Thus, the proposed method can eliminate the timescale separation assumption of hierarchical control strategies. To estimate the external disturbances involved in the translational and rotational dynamics of the quadrotor, disturbance observers are developed. Using state transformations and estimates of external disturbances, we design a robust nonlinear controller based on the dynamic surface control method. The stability of the closed-loop system is analyzed without separation into two subsystems. From the Lyapunov stability theory, it is proven that all error signals in the closed-loop system are uniformly ultimately bounded and can be made arbitrarily small. Finally, simulation results are presented to demonstrate the performance of the proposed controller.
Highlights
Quadrotors are widely used for military and commercial purposes because of their capabilities of vertical take-off and landing (VTOL) and free mobility [1]
To obtain a linearized model, the assumption that the quadrotor is moving around a hovering position is required, which causes the performance of linear control methods to degrade when aggressive maneuvers and external disturbances are applied [11]
We propose a new theoretical control approach different from hierarchical control for the trajectory tracking of a quadrotor in the presence of disturbances
Summary
Quadrotors are widely used for military and commercial purposes because of their capabilities of vertical take-off and landing (VTOL) and free mobility [1]. Electronics 2020, 9, 1624 prove the stability of the closed-loop system and control the position and attitude of the quadrotor simultaneously Nonlinear controllers such as backstepping [16], adaptive [17,18], sliding mode [19,20,21], and neural-network-based controllers [22,23] have all been proposed using hierarchical control strategies. Disturbances in the translational dynamics of the quadrotor are considered to obtain the desired Euler angles This implies that unlike a hierarchical strategy, the proposed method can achieve the desired tracking performance even if we choose low gains and disturbances exist in the translational dynamics. Since the proposed method does not require the instantaneous convergence of attitude control and obtains the desired Euler angles while considering disturbances, the desired tracking performance can be achieved with low gains.
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