No abstract

No abstract

This paper presents a binary observers based linearization feedback sliding mode controller for quadrotor subjected to disturbances and measurement delay. The quadrotor unmanned aerial vehicle is divided into two subsystems, i.e. rotational subsystem and translational subsystem. Disturbance observer based controller is proposed for the former sensitive to disturbances, and binary observers based one for the latter subjected to both disturbances and measurement delay. Binary observers, consisting of disturbance observer and delayed output observer with their interactions being considered, promise exponential convergences of estimations on disturbance and output to their real values, which are compensated in the feedback control loop. The stabilities of the closed-loop subsystems are demonstrated based on Lyapunov theory. In the presence of both disturbances and measurement delay, simulations are carried out to corroborate the effectiveness and robustness of the proposed controller with superior control inputs.

In this study, a novel method is proposed to deal with the problem of altitude measurement of a low-elevation target for very high frequency radars in complex terrains. The problem typically concerns about the direction-of-arrival (DOA) estimation method for closely spaced and correlated signals arose by multipath propagation, in which the multipath signal would be modulated by the rough and irregular reflecting surface, result in amplitude and phase perturbation and energy fluctuations of the receiving signals. A perturbation multipath propagation model is derived where the influence of irregular reflecting in complex terrain is taken as a random perturbation of the multipath signal. The spatial sparsity of the receiving signal is then exploited, and a weighted sparse Bayesian learning method is proposed to estimate both the random perturbation coefficients and DOA of the incident signal with high precision. Both the computer simulations and real data analysis indicate the efficiency and superior performance of the proposed method in dealing with altitude measurement in complex terrain.

No abstract