Micro-Doppler feature extraction of micro-rotor UAV under the background of low SNR

Micro-Doppler feature extraction of unmanned aerial vehicles(UAVs)is important for their identification and classification.Noise and the motion state of the UAV are the main factors that may affect feature extraction and estimation precision of the micro-motion parameters.The spectrum of UAV echoes is reconstructed to strengthen the micro-motion feature and reduce the influence of the noise on the condition of low signal to noise ratio(SNR).Then considering the rotor rate variance of UAV in the complex motion state,the cepstrum method is improved to extract the rotation rate of the UAV,and the blade length can be intensively estimated.The experiment results for the simulation data and measured data show that the reconstruction of the spectrum for the UAV echoes is helpful and the relative mean square root error of the rotating speed and blade length estimated by the proposed method can be improved.However,the computation complexity is higher and the heavier computation burden is required.

Opto propeller effect on Micro–Rotors with different handedness

Manipulating biomacromolecules and micro-devices with light is highly appealing.Opto driving torque can propel micro-rotors to translational motion in viscous liquid,and then separate microsystems according to their handedness.We study the torque of dielectric loss generated by circular polarized lasers.The unwanted axial force which causes the handedness independent translational motion is cancelled by the counter propagating reflection beams.The propelling efficiency and the friction torque of water are obtained by solving the Navier-Stokes equation.In the interesting range of parameters,the numerical friction torque is found to be linear to the angular velocity with a slope depending on the radius of rotor as r^3.The time-dependent distribution of angular velocity is obtained as a solution of the Fokker-Planck equation,with which the thermal fluctuation is accounted.The results shed light on the micro-torque measurement and suggest a controllable micro-carrier.

A review of optically induced rotation

The optical rotation technique arose in the 1990 s.Optical tweezer brought an ideal platform for research on the angular momentum of laser beams.For decades,the optical rotation technique has been widely applied in laboratory optical manipulation and the fields of biology and optofluidics.Recently,it has attracted much attention for its potential in the classical and quantum regimes.In this work,we review the progress of experiments and applications of optically induced rotation.First,we introduce the basic exploration of angular momentum.Then,we cover the development and application of optical rotation induced by orbital angular momentum,and the spin angular momentum is presented.Finally,we elaborate on recent applications of the optical rotation technique in high vacuum.As precise optical manipulation in a liquid medium enters its maturity,optical tweezers in high vacuum open a new path for the high-speed micro-rotor.