A practical time-delay control scheme for aerial manipulators

Abstract

In recent years, aerial manipulators consist of unmanned aerial vehicles and robotic manipulators have been widely utilized in aerial operations. The complex dynamic coupling effects between unmanned aerial vehicles and robotic manipulators will bring some issues to the motion control. Therefore, the article proposes a new control scheme for aerial manipulators. The proposed method includes three elements, that is, time-delay estimation, backstepping design, and nonsingular terminal sliding mode. The time-delay estimation technique is adopted to estimate the complex system dynamics and to bring a model-free feature of the system. With the backstepping design, the proposed control strategy can ensure the asymptotic stability of the closed-loop system by recursive procedure. To deal with the unmodelling dynamics and disturbances, and to assure finite-time convergence of the system states, the nonsingular terminal sliding mode is adopted. By combining three elements, the tracking performance of aerial manipulators is improved under unmodelling dynamics and disturbances. Global stability of closed-loop control system is analyzed using Lyapunov stability theory. Finally, comparative simulations are conducted, and the results show that the proposed controller has better performance than a conventional proportional–derivative controller or a nonsingular terminal sliding mode controller.

Fault‐tolerant control of an aerial manipulator with guaranteed tracking performance

“…Besides Equation (1) and (2), the whole dynamic model of an aerial manipulator should also consider the dynamic interaction between the main‐body UAV and loading manipulator, which has been given in our early work 24 . Here, we need to simplify the complete dynamic model for the FTC controller design.…”

“…The elliptical helix trajectory is selected to verify the tracking performance of proposed controller 24 . An example of desired trajectory is designed as p d = [0.4sin(π t ), 0.4cos(π t )–0.4, 0.25 t ] m, ψ d = 0, as shown in Figures 5 and 6.…”

“…An aerial manipulator is a traditional high‐order system, the backstepping technique provides a system control framework for decomposing the high‐order nonlinear system into several low‐order subsystems, and simplifying the controller structure of each subsystem 24 . When an aerial manipulator system suffers from actuator faults or strong external disturbances, backstepping technique can not guarantee good dynamic characteristics, therefore, it is usually combined with other robust control methods to deal with such situations.…”

“…The interaction dynamics between the main‐body UAV and loading manipulator, and the manipulator and environment are complex. The extended state observer (ESO) provides an effective method to deal with the lumped disturbance 24,29 …”

Time-delay control of quadrotor unmanned aerial vehicles: a multiplicity-induced-dominancy-based approach

“…It is worthwhile highlighting that a considerable amount of prior works focuses on the communication and information exchange processes as the main sources of time-delays [3,31,46,55]. In this regard, the range of solutions to overcome such an issue goes from delay-optimization approaches [35] to Backstepping and non-linear control [20,30,38] yet, a vast variety of different approaches can be found in the literature, see for instance [25, 43-45, 48, 60]. Amidst the novel techniques regarding time-delay systems analysis, tracking the behavior of the roots of the characteristic equation, as in [8], has led to an increasing interest on exploiting the Multiplicity-Induced-Dominancy (MID) property which refers to a special condition where a given root of the characteristic function matches the spectral abscissa such that the corresponding spectral value is dominant.…”