Search results for "Computer Science::Systems and Control"
showing 10 items of 54 documents
A theoretical study of the electronic spectrum of styrene
1999
Abstract The electronic spectrum of styrene has been studied by using multiconfigurational second-order perturbation theory (CASPT2). The study includes geometry optimization of the ground state, the lowest triplet state, and the lowest singlet excited state. The covalent 2 1 A ′ state placed vertically at 4.34 eV is assigned to the first band. The 1 1 A ′→3 1 A ′ transition located at 4.97 eV is responsible for the second band. The most intense feature involves the 5 1 A ′ state, which is calculated to lie 6.19 eV above the ground state. The lowest singlet–singlet Rydberg transition (3s) is predicted to occur at 5.85 eV.
Stability of genetic regulatory networks with time-varying delay: Delta operator method
2015
This paper investigates the stability problem for a class of uncertain genetic regulatory networks (GRNs) with time-varying delay via delta operator approach. Both the parameter uncertainty and the generalized activations are considered in the model under study. By constructing an appropriate Lyapunov-Krasovskii functional, the stability and robust stability conditions of GRNs are presented under the delta operator frame. These conditions can be expressed in terms of linear matrix inequalities (LMIs). Finally, a numerical example is employed to illustrate the effectiveness of the proposed results.
Coupled cluster calculations of the vertical excitation energies of tetracyanoethylene
2003
The vertical spectrum of tetracyanoethylene was studied using coupled cluster theory. It was found that the lowest singlet-singlet transition, which corresponds to the excitation from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) excitation, occurs at 5.16 eV in the gas phase and is lowered approximately 0.1 eV due to solvent effects in acetonitrile. A parallel study on the ethene spectrum showed the quality of the basis sets and methods used, by placing the V state 7.92 eV above the ground state and giving an energy for the 0-0 transition of 5.42 eV to be compared with the experimental value of 5.50 eV.
An ab initio study of the electron affinity of O2
1993
Abstract Coupled pair functional, multiconfigurational second-order perturbation theory, and multireference CI methods have been applied in a calculation of the electron affinity of the oxygen molecule. The convergence of the theoretical result has been checked with respect to a systematic expansion of the one-electron basis and the multireference CI wavefunction. The best calculated value, 0.39 eV, is 0.06 eV smaller than the recent experimental value 0.45±0.01 eV.
Photoconductivity & photoelectron emission of LiGaO2 crystal excited in intrinsic absorption range
2019
This research is funded by the Latvian Council of Science, project “Research of luminescence mechanisms and dosimeter properties in prospective nitrides and oxides using TL and OSL methods], project No. lzp-2018/0361.
Control for Networked Control Systems with Time Delays and Packet Dropouts
2013
This paper is concerned with the control issue for a class of networked control systems (NCSs) with packet dropouts and time-varying delays. Firstly, the addressed NCS is modeled as a Markovian discrete-time switched system with two subsystems; by using the average dwell time method, a sufficient condition is obtained for the mean square exponential stability of the closed-loop NCS with a desired disturbance attenuation level. Then, the desired controller is obtained by solving a set of linear matrix inequalities (LMIs). Finally, a numerical example is given to illustrate the effectiveness of the proposed method.
Robust Predictive Control of a variable speed wind turbine using the LMI formalism
2014
This paper proposes a Robust Fuzzy Multivariable Model Predictive Controller (RFMMPC) using Linear Matrix Inequalities (LMIs) formulation. The main idea is to solve at each time instant, an LMI optimization problem that incorporates input, output and Constrained Receding Horizon Predictive Control (CRHPC) constraints, and plant uncertainties, and guarantees certain robustness properties. The RFMMPC is easily designed by solving a convex optimization problem subject to LMI conditions. Then, the derived RFMMPC applied to a variable wind turbine with blade pitch and generator torque as two control inputs. The effectiveness of the proposed design is shown by simulation results.
Velocity sensorless control of a PMSM actuator directly driven an uncertain two-mass system using RKF tuned with an evolutionary algorithm
2010
This paper proposes a solution to tune an observer keeping robust closed loop performances for the sensorless motion control of an uncertain mechanical load directly driven by a PMSM through a flexible axis. An evolutionary algorithm optimizes the observers degrees of freedom. Experiments show that performances are effectively maintained.
Stability and Noises Evaluation of Fuzzy Kalman UAV Navigation System.
2009
In this paper a new Fuzzy/Kalman navigation system for Unmanned Aerial Vehicles (UAV) is presented. A closed loop velocity Fuzzy navigation system is proposed for stabilizing the UAV in a reference trajectory generated dynamically and for obtaining a forward velocity command. The Kalman's filter (KF) is included in the feedback line of the fuzzy control system to filter the internal noise of the sensors and to evaluate the external noise due to possible perturbations of the nominal motion. The efficiency of the navigation system has been shown through experimental tests in a Matlab environment.
Robustness Analysis of an Extended Kalman Filter for Sensorless Control of Induction Motors
2010
This paper deals with robustness analysis of Extended Kalman Filters (EKFs) for sensorless motion control of induction motors. Analysis is carried out by means of simulation experiments considering a conventional EKF, in which system and measurement noise covariance matrices are constant, and an adaptive EKF in which the system noise covariance matrix is updated on-line using a PID-type algorithm driven by the stator current estimation errors.