The gimbal stabilization mechanism is used to provide the stability to an object mounted on the gimbal by isolating it from the base angular motion and vibration. The purpose of this paper is to present a model of CONTROL servo system for one axis gimbal mechanism using a CASCADE PID CONTROLler. The gimbal torque relationships are derived by taking into consideration the base angular motion. The conventional PID CONTROLler and three CASCADE CONTROLler structures are investigated. The servo CONTROL loop is built and modelled in MATLAB/Simulink using these CONTROLlers. The simulation results are compared and the servo system performance is analysed for each CONTROLler in terms of performance criteria. The comparison results prove that a further improved system performance is achieved using I-PD CONTROLler as compared to the system performance obtained when the other CONTROLlers are utilized. The paper’s value lies in designing the servo CONTROL system using a modified CONTROLler composed of two parallel I-PD CONTROLlers related with a switch depend ing on the base angular rate as a threshold. The results show that the modified system satisfies the desired servo system requirements.

Due to increasing application of multi effect falling film evaporators in food industry. the exact modeling of these processes is important. The aim of this paper is use ability of nonlinear modeling in determining falling film evaporator state variables. Because of large time delays and process disturbances, the tight exact CONTROL of product concentration is difficult. By using the nonlinear modeling, the CONTROL of three effect falling film evaporator with the use of CASCADE CONTROL algorithm is analyzed This paper discusses the application and design of a CASCADE algorithm to CONTROL the product concentration in a milk powder three effect falling-film evaporator. It has been shown that the disturbance rejection properties can be significantly improved with CASCADE CONTROL while still maintaining the tracking properties.

This paper presents a new hierarchical robust algorithm to solve the position tracking problem, in presence of exogenous disturbances and modeling uncertainties, of a quadrotor helicopter. The suggested CONTROLler includes a nonlinear H∞ algorithm to track the reference trajectory in the outer loop and a nonlinear H∞ CONTROLler to stabilize the rotational movements in the inner loop. The resultant CONTROLler consists of three important parts to regulate tracking errors for translational and rotational motions, maintain robust performance confronting random disturbances and modeling uncertainties and reject the sustained disturbances from the system to vanish the steady-state errors. Analytical study on the stability of the CASCADE system is mentioned to verify the compatibility of two CONTROLlers considering coupling terms. Numerical performance analysis is accomplished using Monte-Carlo simulation. Statistical results obtained from 1000 simulations considering environmental disturbances and modeling uncertainties depict less than 5 cm for position tracking error and less than 2 degrees for attitude tracking error in steady state performance. The closed-loop performance of the CONTROLler is also compared with two previous algorithms by determining two numerical indexes for state tracking performance and CONTROL efforts, respectively. Simulation results of the suggested CONTROL algorithm depict a significant reduction in both indexes for a similar mission.

In this paper, stability of a group of networked CASCADE CONTROL systems based on a new continuous-time model is investigated and H∞,state feedback CONTROLlers considering H∞,norm bounded constraint are designed in order to attenuate external disturbances. The main objective of this research is to simplify stability analysis and provide the possibility of considering different configurations based on a continuous-time state-space model for these systems. To this aim, here it is assumed that data transformation between the secondary CONTROLler and the actuator is performed through a communication network. Using communication networks would result in some imperfections such as communication delay and data packet loss which are considered in the modelling of the system. Then, the state-space equations of the systems are converted to an equivalent augmented state-space equation. Stability of the system is analyzed based on the Lyapunov-Krasovskii theorem and using free weighting matrix method and CONTROLler gains as well as maximum allowable delay bound are computed. Simulation results confirm the validity of the proposed method.

In this paper, the problem of CONTROLling PWM single-phase AC/DC converters is addressed. The CONTROL objectives are twofold: (i) regulating the output voltage to a selected reference value, and (ii) ensuring a unitary power factor by forcing the grid current to be in phase with the grid voltage. To achieve these objectives, the singular perturbation technique is used to prove that the power factor correction can be done in the open-loop system with respect to certain conditions that are not likely to take place in reality. It is also applied to fulfill the CONTROL objectives in the closed-loop through a CASCADE nonlinear CONTROLler based on the three-time scale singular perturbation theory. Additionally, this study develops a rigorous and complete formal stability analysis, based on multi-time-scale singular perturbation and averaging theory, to examine the performance of the proposed CONTROLler. The theoretical results have been validated by numerical simulation in MATLAB/Simulink/SimPowerSystems environment.

The compressor CASCADE performance is significantly restricted by the secondary flow mainly presented as the trailing edge separation and corner stall. This paper develops a synthetic flow CONTROL approach in a high turning CASCADE using the vortex generator and slot jet approach. Numerical simulations were conducted to assess the flow CONTROL benefits and illustrate the flow CONTROL mechanisms. Four configurations, the baseline, the two individual approaches and the synthetic approach, were simulated to compare the separation CONTROL effects. The simulations show that all the three configurations achieve considerable improvements of the CASCADE performance and the CASCADE sensitivity to incidence angle is greatly decreased. The synthetic approach improves the most among them which is almost the superposition of the two individual ones. In the synthetic approach, the trailing vortex induced by the vortex generator suppresses the end wall cross flow and deflects the passage vortex, and then prevents the production of corner stall; at the same time, the slot jet speeds up the trailing edge separation caused by the CASCADE high camber. Owing to the combination of the two aspects, the synthetic approach restricts the developments of secondary flow and vortices in the CASCADE, and improves the outflow uniformity. The synthetic approach nicely utilizes the advantages of the two individual approach while avoids the shortages by the complementation, so it can achieve more powerful flow CONTROL effects. At the end, vortices models are established to illustrate the secondary flow structure and the flow CONTROL mechanisms.

The paper reports computational and experimental investigations carried out to CONTROL of laminar flow separation in LP turbine CASCADE blades at low Reynolds numbers. T106 LP turbine blade profile with a chord of 60 mm and blade spacing of 48 mm was used. The blade Zweifel loading factor was 1. 03. Passive separation CONTROL device of Gurney flaps (GFs) of different shapes and sizes were used. Computations were carried out in Ansys-CFX. A two-equation eddy-viscosity turbulence model, shear stress transport (SST) was considered for all the computations along with gamma-theta (transition model. Computations were carried out for five different Reynolds numbers. Lift coefficient, total pressure loss coefficient, overall integrated loss coefficient and ratio of lift coefficient to overall integrated loss coefficient were used as a measure of aerodynamic performance for the CASCADE. From the computations, Flat and Quarter Round GFs of heights of 1. 33% of chord were identified as the best configurations. Experiments in a seven bladed CASCADE were carried out for these configurations along with the basic configuration without GF at five Reynolds numbers. Experimental results agreed well with the computational results for these three cases at the five Reynolds numbers.