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An efficient algorithm for frequency estimation from cosine-sum windowed DFT coefficients
Shin, Donghoon,Kwak, Chulhyun,Kim, Gwangtae Elsevier 2020 Signal processing Vol.166 No.-
<P><B>Abstract</B></P> <P>This paper presents an algorithm for estimating frequency of a complex sinusoid from three DFT coefficients. In particular, we consider the case where the signal is multiplied by a generic cosine-sum window for interference suppression. The algorithm is an interpolator that uses the peak sample in the DFT of the data and its two neighbors. The interpolator is based on a numerically efficient procedure which guarantees convergence to a solution. Performance of the proposed interpolator is shown to be nearly optimum and comparable to the best interpolator in the literature, while the computational burden required for the proposed algorithm is much lower than the generic numerical methods available. Degradation of performance due to interference is also investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A numerically efficient method for frequency estimation by Interpolation on DFT coefficients. </LI> <LI> The use of generic cosine-sum windows for interference suppression. </LI> <LI> Performance that nearly achieves the Cramer–Rao bounds. </LI> </UL> </P>
Donghoon Shin,Youngwoo Lee,Wonhee Kim,Chung Choo Chung 제어로봇시스템학회 2016 제어로봇시스템학회 국제학술대회 논문집 Vol.2016 No.10
In this paper, we present an observer based nonlinear controller using barrier Lyapunov function (BLF) for position tracking of Sawyer motor under yaw constraint. The dynamics of Sawyer motor is modified to apply BLF-based backstepping control design. To relax the matching condition, torque and force modulations are proposed. The modulations enable decoupling forces and torque of the Sawyer motor, and facilitate implementing the design of backstepping controller with the BLF. In addition, we propose a state augmented nonlinear observer to estimate the velocities, yaw rate, load forces and load torque. We show the closed-loop stability with a composite Lyapunov function. Simulation results validate the effectiveness of the proposed method.
TVWS assisted performance anomaly mitigation exploiting spectrum heterogeneity
Shin, Kyubo,Kim, Hyoil,Chun, Se Young,Shin, Donghoon Elsevier 2018 COMPUTER NETWORKS - Vol.141 No.-
<P><B>Abstract</B></P> <P>Super Wi-Fi is a Wi-Fi-like service utilizing TV white spaces (TVWS), which has been revealed to provide higher data rates in the outskirts of Wi-Fi’s coverage, thanks to the spectrum heterogeneity between Wi-Fi bands and TVWS. Motivated by this, this paper proposes co-locating a Super Wi-Fi access point (AP) with a Wi-Fi AP aiming to mitigate the performance anomaly of the WLAN by relocating low-rate Wi-Fi stations (STAs) to Super Wi-Fi in the outskirts of Wi-Fi’s coverage. Then, the proposed strategy can enhance average per-STA throughput of both Wi-Fi STAs and relocated Super Wi-Fi STAs while also improving the data rate of Super Wi-Fi STAs, than they would achieve with the legacy Wi-Fi. To quantify such performance improvement, we model the system as a series of two-dimensional Markov chains and provide an in-depth analysis of steady-state probabilities and per-STA throughput. Numerical analysis has shown that Super Wi-Fi co-location improves <I>not only</I> average per-STA throughput <I>but also</I> spectral efficiency, compared to the legacy Wi-Fi with 20 or 20+20 MHz bandwidth for the single BSS scenario. In addition, average per-STA throughput and spectral efficiency are also enhanced in the OBSS scenario both in rural and urban environments. Hence, the co-location strategy is proven to be quite effective in enhancing WLAN’s performance.</P>
Shin, Donghoon,Kim, Wonhee,Lee, Youngwoo,Chung, Chung Choo IEEE 2017 IEEE transactions on control systems technology Vol.25 No.4
<P>In this paper, we present nonlinear control with a state-dependant reset integrator (RI) for a class of singularly perturbed interconnected nonlinear system. There are many approaches to use integrator reset. But, it has not been reported yet how to design the reset surface influencing the performance of servo system. In this paper, we introduce how to design the reset surface using a Lyapunov function based on the slow subsystem. We design the reset surface, which is a function of a threshold for output tracking error, to guarantee that the Lyapunov function decreases at every reset time. Given the Lyapunov function, we introduce an optimization process to get the lowest bound of threshold. It is proven that the proposed method ensures the globally exponential stability of tracking errors. The proposed method provides the guidelines on how to determine the control gains and reset surface. A numerical example using a permanent magnet stepper motor is given to illustrate the design process for the proposed controller. We performed the experiments for a comparative study with the previous RIs. The experimental results validate the effectiveness of the proposed method.</P>
Shin, Donghoon,Lee, Geesu,Yi, Kyongsu,Noh, Kihan Professional Engineering Publishing Ltd 2016 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>This paper describes motorized active suspension damper control with dynamic friction and actuator delay compensation for an enhanced ride quality. The control algorithm consists of a supervisory controller, an upper-level controller and a lower-level controller. The supervisory controller determines the control modes, such as the passive control modes and the active control mode. The upper-level controller, which incorporates the existing actuator delay, computes the damping force using linear quadratic control theory. The actuator input is determined by the lower-level controller by compensating the dynamic friction torque. To estimate the sprung-mass displacement, the sprung-mass velocity, the unsprung-mass displacement and the unsprung-mass velocity, two state estimators are proposed. An adaptive observer is developed for the non-linear dry friction to estimate the ball-screw dynamic friction caused by the axial movement of the actuator and the viscosity. The performance of the proposed control algorithm was evaluated from simulations. It was shown from simulations that the proposed motorized active suspension damper control with a friction and delay compensation algorithm can improve the ride quality.</P>