Dynamic Control of Defective Gap Mode Through Defect Location

A one dimensional model is developed for defective gap mode（DGM）with two types of boundary conditions：conducting mesh and conducting sleeve.For a periodically modulated system without defect,the normalized width of spectral gaps equals to the modulation factor,which is consistent with previous studies.For a periodic system with local defects introduced by the boundary conditions,it shows that the conducting-mesh-induced DGM is always well confined by spectral gaps while the conducting-sleeve-induced DGM is not.The defect location can be a useful tool to dynamically control the frequency and spatial periodicity of DGM inside spectral gaps.This controllability can be potentially applied to the interaction between gap eigenmodes and energetic particles in fusion plasmas,and optical microcavities and waveguides in photonic crystals.

Simple Method for Tethered Space Debris Retrieval

Space debris retrieval problem utilizing a tethered system in an elliptical orbit is studied in this paper.An analytical control law specified by a tether length rate for retrieval is derived from a dumbbell model of the system.The proposed control method can suppress large swings around the local vertical position of the tethered system.Under such a control strategy,the debris retrieval behaves in asymptotic stable motion towards the expected angle.The stability of the non-autonomous system during the retrieval control is analyzed using the Floquet theory.The result demonstrates that an orbital region exists,on which the retrieval process maintains asymptotically stable.The proposed analytical control law is validated via numerical simulations.

Analytical charge control model for AlGaN/GaN MIS-HFETs including an undepleted barrier layer

An analytical charge control model considering the insulator/AlGaN interface charge and undepleted Al-GaN barrier layer is presented for AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors （MIS-HFETs） over the entire operation range of gate voltage.The whole process of charge control is analyzed in detail and partitioned into four regions：Ⅰ—full depletion,Ⅱ—partial depletion,Ⅲ—neutral region andⅣ—electron accumulation at the insulator/AlGaN interface.The results show that two-dimensional electron gas（2DEG） saturates at the boundary of regionⅡ/Ⅲand the gate voltage should not exceed the 2DEG saturation voltage in order to keep the channel in control.In addition,the span of regionⅡaccounts for about 50%of the range of gate voltage before 2DEG saturates.The good agreement of the calculated transfer characteristic with the measured data confirms the validity of the proposed model.

Analytical libration control law for electrodynamic tether system with current constraint

This study focuses on stabilizing the libration dynamics of an electrodynamic tether system(EDTS)using generalized torques induced by the Lorentz force.In contrast to existing numerical optimization methods,a novel analytical feedback control law is developed to stabilize the in-plane and out-of-plane motions of a tether by modulating the electric current only.The saturation constraint on the current is accounted for by adding an auxiliary dynamic system to the EDTS.To enhance the robustness of the proposed controller,multiple perturbations of the orbital dynamics,modeling uncertainties,and external disturbances are approximated using a neural network in which the weighting matrix and approximation error are estimated simultaneously,such that these perturbations are well compensated for during the control design of the EDTS.Furthermore,a dynamically scaled generalized inverse is utilized to address the singular matrix in the control law.The closed-loop system is proven to be ultimately bounded based on Lyapunov stability theory.Finally,numerical simulations are performed to demonstrate the effectiveness of the proposed analytical control law.

Nonlinear optimal predictive controller for static var compensator to improve power system damping and to maintain voltage

The main objectives of this paper are to simul-taneously improve power system damping and to maintain voltage at the static var compensator(SVC)location bus simultaneously.A new controller for SVC with closed-form analytic solution nonlinear optimal predictive control(NOPC)law was presented.The controller does not require online optimization and the huge calculation burden can be avoided,so that the demand of real-time control can be sat-isfied.In addition,there are only two design parameters,which are the predictive period and control order;so it is easy to implement and test in practical use.Simulation results have shown that the controller can not only attenuate power system oscillation effectively but can also maintain voltage at the SVC bus location.