A PRECOMPENSATOR DESIGN TO ACHIEVE DECOUPLING IN THE FREQUENCY DOMAIN

This paper deals with the problem of designing a precompensator by using the frequency domain approach for systems which have weak inherent coupling. A necessary and sufficient new condition for decoupling is given which is the basis of the first algorithm suggested to achieve dynamic decoupling. Another algorithm is presented for the same purpose, by making use of the interactor matrix idea. For each method all the poles of the precompensator can be assigned arbitrarily and the construction does not depend upon the control law used

TRIANGULAR DECOUPLING THROUGH LINEAR STATE VARIABLE FEEDBACK

The paper studies the problem of triangular decoupling through l.s.v. f. using frequency-domain approaches. The interactor concept and the matrix fraction right description form are used to resolve the questions concerned with this problem and in turn an algorithm is given for triangularization of any right invertible proper system by using l.s.v.f. alone. The paper describes the use of triangular decoupling as an intermediate step for exact decoupling of systems having unstable decoupling zeros

Control and Supervision of Wind Energy Conversion Systems

This paper is about a PhD thesis and includes the study and analysis of the performance of an onshore wind energy conversion system. First, mathematical models of a variable speed wind turbine with pitch control are studied, followed by the study of different controller types such as integer-order controllers, fractional-order controllers, fuzzy logic controllers, adaptive controllers and predictive controllers and the study of a supervisor based on finite state machines is also studied. The controllers are included in the lower level of a hierarchical structure composed by two levels whose objective is to control the electric output power around the rated power. The supervisor included at the higher level is based on finite state machines whose objective is to analyze the operational states according to the wind speed. The studied mathematical models are integrated into computer simulations for the wind energy conversion system and the obtained numerical results allow for the performance assessment of the system connected to the electric grid. The wind energy conversion system is composed by a variable speed wind turbine, a mechanical transmission system described by a two mass drive train, a gearbox, a doubly fed induction generator rotor and by a two level converter

Benchmarking Tracking Autopilots for Quadrotor Aerial Robotic System Using Heuristic Nonlinear Controllers

This paper investigates and benchmarks quadrotor navigation and hold autopilots’ global control performance using heuristic optimization algorithms. The compared methods offer advantages in terms of computational effectiveness and efficiency to tune the optimum controller gains for highly nonlinear systems. A nonlinear dynamical model of the quadrotor using the Newton–Euler equations is modeled and validated. Using a modified particle swarm optimization (MPSO) and genetic algorithm (GA) from the heuristic paradigm, an offline optimization problem is formulated and solved for three different controllers: a proportional–derivative (PD) controller, a nonlinear sliding-mode controller (SMC), and a nonlinear backstepping controller (BSC). It is evident through the simulation case studies that the utilization of heuristic optimization techniques for nonlinear controllers considerably enhances the quadrotor system response. The performance of the conventional PD controller, SMC, and BSC is compared with heuristic approaches in terms of stability and influence of internal and external disturbance, and system response using the MATLAB/SIMULINK environment. The simulation results confirm the reliability of the proposed tuned GA and MPSO controllers. The PD controller gives the best performance when the quadrotor system operates at the equilibrium point, while SMC and BSC approaches give the best performance when the system does an aggressive maneuver outside the hovering condition. The overall final results show that the GA-tuned controllers can serve as a benchmark for comparing the global performance of aerial robotic control loops

Benchmarking Tracking Autopilots for Quadrotor Aerial Robotic System Using Heuristic Nonlinear Controllers

This paper investigates and benchmarks quadrotor navigation and hold autopilots’ global control performance using heuristic optimization algorithms. The compared methods offer advantages in terms of computational effectiveness and efficiency to tune the optimum controller gains for highly nonlinear systems. A nonlinear dynamical model of the quadrotor using the Newton–Euler equations is modeled and validated. Using a modified particle swarm optimization (MPSO) and genetic algorithm (GA) from the heuristic paradigm, an offline optimization problem is formulated and solved for three different controllers: a proportional–derivative (PD) controller, a nonlinear sliding-mode controller (SMC), and a nonlinear backstepping controller (BSC). It is evident through the simulation case studies that the utilization of heuristic optimization techniques for nonlinear controllers considerably enhances the quadrotor system response. The performance of the conventional PD controller, SMC, and BSC is compared with heuristic approaches in terms of stability and influence of internal and external disturbance, and system response using the MATLAB/SIMULINK environment. The simulation results confirm the reliability of the proposed tuned GA and MPSO controllers. The PD controller gives the best performance when the quadrotor system operates at the equilibrium point, while SMC and BSC approaches give the best performance when the system does an aggressive maneuver outside the hovering condition. The overall final results show that the GA-tuned controllers can serve as a benchmark for comparing the global performance of aerial robotic control loops

Association between oxidative stress and cord serum lipids in relation to delayed cord clamping in term neonates

Abstract Background Although delayed cord clamping (DCC) is a recent WHO recommendation, early cord clamping (ECC) is still a routine practice in many countries. Limited researches studied the effect of delayed cord clamping on oxidative stress in term neonates; In this study we aim to assess the influence of cord clamping either early or late on oxidative stress in term neonates and to evaluate the association of oxidative stress and cord blood lipids. Methods One-hundred mothers and their term neonates were included in the present study. Umbilical cord blood samples were collected from the umbilical vein and umbilical artery immediately following labor. Results Total cholesterol, total triglycerides and phospholipids levels were significantly higher in the ECC group than the DCC group (p < 0.001 in all). Plasma total antioxidant status was higher in the DCC group than the ECC group (p < 0.001). While, plasma hydroperoxides were lower in the DCC group than the ECC group (p < 0.001). Levels of erythrocytes catalase cytosol, superoxide dismutase and glutathione peroxidase were significantly higher in the DCC group than the ECC group (p < 0.001). Conclusion DCC was associated with a decrease in cord blood lipids and an augmented antioxidant activity. This suggests the protective effect of DCC on the future health of the term neonates and supports the application of DCC in active management of 3rd stage of labor in term neonates