Browsing by Subject "Velocity measurement"

Now showing 1 - 6 of 6

Open Access
Experimental results and bifurcation analysis on scaled feedback control for subsonic cavity flows
(IEEE, 2006) Yuan, X.; Caraballo, E.; Debiasi, M.; Little, J.; Serrani, A.; Özbay, Hitay; Samimy, M.
In this paper, we present the latest results of our ongoing research activities in the development of reduced-order models based feedback control of subsonic cavity flows. The model was developed using the Proper Orthogonal Decomposition of Particle Image Velocimetry images in conjunction with the Galerkin projection of the Navier-Stokes equations onto the resulting spatial eigenfunctions. Stochastic Estimation method was used to obtain the state estimation of the Galerkin system from real time surface pressure measurements. A linear-quadratic optimal controller was designed to reduce cavity flow resonance and tested in the experiments. Real-time implementation shows a significant reduction of the sound pressure level within the cavity, with a remarkable attenuation of the resonant tone and a redistribution of the energy into various modes with lower energy levels. A mathematical analysis of the performance of the LQ control, in agreement with the experimental results, is presented and discussed.
Open Access
Generation of parabolic bound pulses from a Yb-fiber laser
(Optical Society of American (OSA), 2006) Ortaç, B.; Hideur, A.; Brunel, M.; Chédot, C.; Limpert J.; Tünnermann, A.; Ilday F.Ö.
We report the observation of self-similar propagation of bound-state pulses in an ytterbium-doped double-clad fiber laser. A bound state of two positively chirped parabolic pulses with 5.4 ps duration separated by 14.9 ps is obtained, with 1.7 nJ of energy per pulse. These pulses are extra-cavity compressed to 100 fs. For higher pumping power and a different setting of the intra-cavity polarization controllers, the laser generates a bound state of three chirped parabolic pulses with different time separations and more than 1.5 nJ energy per pulse. Perturbation of this bound state by decreasing pump power results in the generation of a single pulse and a two-pulse bound state both structures traveling at the same velocity along the cavity. A possible explanation of the zero relative speed by a particular phase relation of the bound states is discussed. ©2006 Optical Society of America.
Open Access
High‐speed atomic force microscopy using an integrated actuator and optical lever detection
(A I P Publishing LLC, 1996-09) Manalis, S. R.; Minne, S. C.; Atalar, Abdullah; Quate, C. F.
A new procedure for high‐speed imaging with the atomic force microscope that combines an integrated ZnO piezoelectric actuator with an optical lever sensor has yielded an imaging bandwidth of 33 kHz. This bandwidth is primarily limited by a mechanical resonance of 77 kHz when the cantilever is placed in contact with a surface. Images scanned with a tip velocity of 1 cm/s have been obtained in the constant force mode by using the optical lever to measure the cantilever stress. This is accomplished by subtracting an unwanted deflection produced by the actuator from the net deflection measured by the photodiode using a linear correction circuit. We have verified that the tip/sample force is constant by monitoring the cantilever stress with an implanted piezoresistor.
Open Access
Incorporating doppler velocity measurement for track initiation and maintenance
(IET, 2006) Kural, F.; Arıkan, F.; Arıkan, Orhan; Efe, M.
Performance of multiple target tracking algorithms in complex environments heavily relies on the success of track initiation and measurement-to-track association algorithms. Doppler velocity measurement is the major discriminant of clutter from the target of interest with relatively higher velocities. This work summarizes the analytical derivations and presents simulation results about track initiation and maintenance using Doppler velocity reports along with the 3D position measurements extracted by a phased array radar.
Open Access
Performance evaluation of track association and maintenance for a MFPAR with doppler velocity measurements
(2010) Kural, F.; Arikan, F.; Arıkan, Orhan; Efe, M.
This study investigates the effects of incorporating Doppler velocity measurements directly into track association and maintenance parts for single and multiple target tracking unit in a multi function phased array radar (MFPAR). Since Doppler velocity is the major discriminant of clutter from a desired target, the measurement set has been expanded from range, azimuth and elevation angles to include Doppler velocity measurements. We have developed data association and maintenance part of a well known tracking method, Interacting Multiple Model Probabilistic Data Association.
Open Access
Performance improvement of track initiation algorithms with the incorporation of doppler velocity measurement
(IEEE, 2006) Kural, F.; Arıkan, F.; Arıkan, Orhan
In this study, to obtain the analytical expressions of false track initiation probability, elevation and Doppler velocity measurements extracted by a phased array radar are incorporated for the first time into the commonly used track initiation algorithms. With this study, the measurement set is expanded from a merely range and azimuth to include elevation and Doppler velocity. The analytical expressions of false track initiation probability depend on the parameters of the signal processing unit of the phased array radar, such as false alarm probability, true detection probability, signal-to-noise ratio and detector threshold. Furthermore, such expressions remove the necessity of very time-consuming simulations. The results indicate that using position and Doppler velocity measurements provide a reduction of false track initiation probability by a factor of 9 to 34 depending on the value of velocity and acceleration thresholds while supplying the design criterion of the true track initiation probability, ≥ 0.7.