Optimal Mode Control Research Articles

Optimal Excitation Control System of Synchronous Generator in Big Disturbance Based on Improved LOEC Mode

Linear optimal excitation control (LOEC) mode takes the power system as multiple control target, it has better dynamic performance and adaptability in the vicinity of the equilibrium point. But when the disturbance is too large, the system performance will be deteriorated, meantime controlling lack the terminal voltage control. This paper presents the optimal excitation controller which has a wide excitation control system adapting to a wide range disturbance. The choice of variables is changed based on the variables used in the excitation control of exact linearization. The speed deviation differential is used to replace the electromagnetic power deviation in commonly optimal excitation control system, and the terminal voltage control is added. The improved excitation control system adaptability is enhanced. The simulation results show that the improved excitation controller has a wider adjustment range, anti-disturbance and strong characteristics.

Childhood determinants of blood pressure and prehypertension in adolescents - results from the SAPALDIA youth study

Background: Hypertension has become the leading risk factor contributing to the global disability adjusted life years. Adolescent hypertension is increasing, possibly due to the obesity epidemic, and is known to track into adulthood. The SAPALDIA Youth Study, a nested study within the adult Swiss Air Pollution And Lung and Heart Disease In Adults cohort (SAPALDIA), aims to investigate early life factors and cardiovascular health in adolescents, with a special focus on active tobacco exposure. Methods: 288 SAPALDIA offspring (mean age 15 years, sd 3.5) underwent clinical examination and reported on early life, health and lifestyle, smoking habits and disease history. Parental determinants and disease status were taken from the SAPALDIA adult cohort data. The mean of two blood pressure measurements, following standard protocols, was calculated for analyses. Prehypertension in childhood was defined as average systolic (SBP) or diastolic blood pressure (DBP) levels ≥90th percentile but <95th percentile for gender, age, and height, respectively in adolescents ≥120/80 mmHg (2). Descriptive and multi-level regression analyses were performed to investigate the independent impact of early life determinants on blood pressure and prehypertension. Results: Prehypertensive values were found in 24%. We confirmed the impact of BMI on SBP (1 mmHg/10 percentile points, 95% CI 0.04,0.14, DBP 0.02 mmHg, 95%Ci -0.02; 0.06), and of high physical activity (≥60 min strenuous activity/day, SBP -3mmHg, 95% CI -6.0; 0.1, DBP -2.2 mmHg, -4.5; 0.1) and found a borderline significance for weekly smoking on SBP (SBP 3.6 mmHg; 95% CI -0.82; 8.0; DBP 2.3 mmHg, 95% CI -1.2; 5.7). Additional adjustment for parental education, smoking and cardiovascular risk strengthened the adverse association seen for weekly smoking. Associations with DBP proved less significant. Similar results were found in analyses with prehypertension. Conclusion: A high percentage of youth presented with prehypertension. Considering the impact of modifiable risk factors, and the high risk of prehypertension turning into clinical hypertension, screening for prehypertension and risk factors in youth should be given full attention to reduce the population risk by optimal metabolic control and lifestyle modification. Reference: 1. National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents. Pediatrics 2004

Optimal Load Frequency Control in Two Area Hydro Thermal Deregulated System with Co-Ordinated Control of SMC-TCPS

This article looks into the implementation of TCPS (FACTS controller) with optimal sliding mode control strategy in order to solve load frequency Control problem in multi area deregulated hydro thermal system. When the system undergoes sudden disturbances the new coordinated control strategy can manage nonlinearities and uncertainties. This new technique of combination of TCPS and optimal sliding mode controller tested on two area hydro thermal deregulated power system including bilateral contacts. When compared with combination of TCPS and sliding mode observer based optimal controller and combination of TCPS and Conventional PI controller a dynamic response of the proposed TCPS and Optimal sliding mode controller has been observed.

Feasible study of a self-cooled solid desiccant cooling system based on desiccant coated heat exchanger

Solid desiccant cooling technology has become a research focus for its features of energy-saving and eco-friendly. However, widely adopted rotary desiccant wheel cooling system can't realize inner-cooling dehumidification process. In this paper, a novel self-cooled solid desiccant cooling system (SCDHE) is developed by integrating desiccant coated heat exchanger and regenerative evaporative cooler. In the system, regenerative evaporative cooler is adopted to produce chilled water, which is again pumped into desiccant coated heat exchanger in dehumidification process to realize self-cooled dehumidification process. Similarly, in regeneration process, hot water heated by low grade thermal energy is adopted to regenerate the coated desiccant material. A mathematical model is established to validate the feasibility and to analyze performance of this novel system. Also, effects of ambient air condition are predicted. It is found that SCDHE system is feasible, it can provide satisfied supply air to conditioned room under simulated ARI summer condition, and the required regeneration temperature is from 50 to 80 °C which is lower than rotary wheel desiccant cooling system. Also, there exists an optimal switch time and suitable control mode for system to obtain enhanced performance in terms of cooling power. Compared with conventional DCHE cooling system without regenerative evaporative cooling, SCDHE system can provide satisfied supply air while conventional system cannot, also it can obtain increased cooling power. Under simulation condition, cooling power of SCDHE system increases by about 30% compared with conventional DCHE cooling system.

An Adaptive Model for Calculating the Correlation Degree of Multiple Adjacent Signalized Intersections

As an important component of the urban adaptive traffic control system, subarea partition algorithm divides the road network into some small subareas and then determines the optimal signal control mode for each signalized intersection. Correlation model is the core of subarea partition algorithm because it can quantify the correlation degree of adjacent signalized intersections and decides whether these intersections can be grouped into one subarea. In most cases, there are more than two intersections in one subarea. However, current researches only focus on the correlation model for two adjacent intersections. The objective of this study is to develop a model which can calculate the correlation degree of multiple intersections adaptively. The cycle lengths, link lengths, number of intersections, and path flow between upstream and downstream coordinated phases were selected as the contributing factors of the correlation model. Their jointly impacts on the performance of the coordinated control mode relative to the isolated control mode were further studied using numerical experiments. The paper then proposed a correlation index (CI) as an alternative to relative performance. The relationship between CI and the four contributing factors was established in order to predict the correlation, which determined whether adjacent intersections could be partitioned into one subarea. A value of 0 was set as the threshold of CI. If CI was larger than 0, multiple intersections could be partitioned into one subarea; otherwise, they should be separated. Finally, case studies were conducted in a real-life signalized network to evaluate the performance of the model. The results show that the CI simulates the relative performance well and could be a reliable index for subarea partition.

Optimal control modification for robust adaptive control with large adaptive gain

In the presence of large uncertainties, a control system needs to be able to adapt rapidly to regain performance. Fast adaptation is referred to the implementation of adaptive control with a large adaptive gain so as to reduce the tracking error rapidly. However, a large adaptive gain can lead to high-frequency oscillations which can adversely affect robustness. A new adaptive law, called optimal control modification, is presented that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations. The modification is based on a minimization of the L2 norm of the tracking error bounded away from some lower bound, formulated as an optimal control problem. The optimality condition is used to derive the modification based on the Pontryagin’s Minimum Principle. The optimal control modification is shown to improve robustness of the standard MRAC without significantly compromising the tracking performance. Flight control simulations demonstrate the effectiveness of the new adaptive law. A series of recent, successful flight tests of this adaptive law on a NASA F/A-18A aircraft at NASA Dryden Flight Research Center further demonstrate the effectiveness of the optimal control modification adaptive law.

Multi-modes control method for spacecraft formation establishment and reconfiguration near the libration points

This paper studies Multi-modes control method for libration points formation establishment and reconfiguration. Firstly, relations between optimal impulse control and Floquet modes are investigated. Method of generating modes is proposed. Characteristics of the mode coefficients stimulated at different time are also given. Studies show that coefficients of controlled modes can be classified into four types, and formation establishment and reconfiguration can be achieved by multi-impulse control with the presented method of generating modes. Then, since libration points formation is generally unstable, mutli-modes keeping control method which can stabilize five Floquet modes simultaneously is proposed. Finally, simulation on formation establishment and reconfiguration are carried out by using method of generating modes and mutli-modes keeping control method. Results show that the proposed control method is effective and practical.

Sliding mode optimal control for linear systems

This paper addresses the optimal control problem for a linear system with respect to a Bolza–Meyer criterion with a non-quadratic non-integral term. The optimal solution is obtained as a sliding mode control, whereas the conventional linear feedback control fails to provide a causal solution. Performance of the obtained optimal controller is verified in the illustrative example against the conventional LQ regulator that is optimal for the quadratic Bolza–Meyer criterion. The simulation results confirm an advantage in favor of the designed sliding mode control.

On a generalization of the impulsive control concept: Controlling system jumps

This paper concerns the investigation of a general impulsive control problem. The considered impulsive processes are of non-standard type: control processes admit ordinary type controls as the impulse develops. New necessary conditions of optimality in the form of Pontryagin Maximum Principle are obtained. These conditions are applied to a model problem and are shown to yield useful information about optimal control modes.

UPFC for Enhancing Power System Reliability

This paper discusses various aspects of unified power flow controller (UPFC) control modes and settings and evaluates their impacts on the power system reliability. UPFC is the most versatile flexible ac transmission system device ever applied to improve the power system operation and delivery. It can control various power system parameters, such as bus voltages and line flows. The impact of UPFC control modes and settings on the power system reliability has not been addressed sufficiently yet. A power injection model is used to represent UPFC and a comprehensive method is proposed to select the optimal UPFC control mode and settings. The proposed method applies the results of a contingency screening study to estimate the remedial action cost (RAC) associated with control modes and settings and finds the optimal control for improving the system reliability by solving a mixed-integer nonlinear optimization problem. The proposed method is applied to a test system in this paper and the UPFC performance is analyzed in detail.

Domain of Pole Placement with Optimal Modal Control: Analysis of a System Represented by an Uncertain Model

The specific aim of this paper is to help the design of industrial process controls. Indeed, if an optimal control is chosen, a robust control is obtained. But on the other hand, the placement of the poles is not possible and thus, dynamics is not controlled. This is why in this paper an Optimal Modal Control, i.e. an Optimal Control (LQ criterion) with pole placement, is presented. The method is proposed to place the poles two by two and to obtain a positive-semidefinite resulting state-weighting matrix Q. So this method preserves the robustness of the Optimal Control and it enables to determine a domain of pole placement (D-domain).A stability robustness analysis of this type of placement is carried out upon a system represented by an uncertain model. A 2-dimensional system is studied and a numerical example is developed. The matrix Q is obtained in a diagonal form, which is useful for the designer.

Diabetes in elderly adults.

Diabetes is common in the elderly population. By the age of 75, approximately 20% of the population are afflicted with this illness. Diabetes in elderly adults is metabolically distinct from diabetes in younger patient populations, and the approach to therapy needs to be different in this age group. Diabetes is associated with substantial morbidity from macro- and microvascular complications. Several lines of evidence suggest that optimal glycemic control and risk factor modification can substantially reduce the risk of complications in elderly patients. In the past, treatment options were limited. However, recent studies have delineated several new and exciting therapeutic opportunities for elderly patients with diabetes.

Dynamic thermal model for predicting solar plant adequate energy management

As is known, efficient renewable energy plant designs should incorporate features that make maximum use of solar energy. In addition to the need of further development and experimental performance evaluation of the solar plant's energy, there is also the need to develop mathematical models for accurate prediction and control of the solar plant's thermal environment. These models can also be used as a design tool and in economic feasibility studies. In this paper, a dynamic mathematical model for predicting the thermal performance of a low temperature solar plant was developed. Consequently, the model gives the optimal control mode that offers maximum thermal efficiency to the plant. Validation of the model was performed for both the calculation of daily and long term performances (monthly and yearly) considering a large sized solar plant installed in the north of Tunisia. The result showed good reproduction of thermal performance. Furthermore, comparison of the plant measured variables with model predictions showed a high degree of correlation.

Implementation of coupled mode optimal structural vibration control using approximated eigenfunctions

With the approximately normalized eigenfunctions and matching modal equations obtained in a differential form, we have implemented the structural vibration control successfully. In applying the steady-state quadratic coupled mode optimal control algorithm for the control structure, i.e. the all-clamped square plate, the non-orthogonalized extra terms are evaluated. By the suitable formulation of a control system, we could simulate the modal responses of the first six modes showing the validity of proposed modal equations and all the control procedures are considered to be reliable as a structural vibration control scheme. Modal responses for single and double actuators are observed and by changing the other control factors such as impulse position and weighting matrices we could compare the control performance. Moreover, these simulation results provide ideas on how to select the optimal number and positions of the actuators.

Optimal pole placement in time-dependent linear systems

In this paper a problem of optimal modal control for general linear, time-dependent systems is posed and solved. We review the recent modal decomposition of the general linear system. We then pose the problem of controlling one unstable mode, with a specified new Lyapunov exponent, but minimizing the mean-square gain function. The method is applied to the shallow-angle re-entry of a Delta Clipper-like vehicle, and the modal decomposition leads to both stability information and characterization of how the trajectory is unstable. The unstable Lyapunov exponent is moved so that the trajectory is stable, as verified by closed-loop Lyapunov exponent analysis. When implemented within the original nonlinear system, the controller can handle initial errors at the kilometer level. Only 4% modulation of the original drag factor is required for control. I. Introduction T HE problem of control of constant coefficient linear systems is well understood, forming the basis of most of control theory. Control of time-dependent systems is not yet at the same level of understanding. Fairly comprehensive discussion of the time-periodic case have appeared: see Breakwell et al. 1 for the linear quadratic regulator for periodic systems and Calico and Wiesel2 for pole placement in periodic systems. Recently, the current author has successfully produced the modal decomposition for a general timedependent linear system3 and introduced the first pole placement algorithm for such systems. In this paper we extend the method to optimal pole placement and will successfully control a shallowangle re-entry trajectory by this new technique.

Thermal feedback control techniques for transistor–transistor logic triggered CO_2 laser used for irradiation of biological tissue utilizing infrared fiber-optic radiometry

A fiber-optic radiometer is used to monitor and control, in real time, the temperature of samples of biological tissue irradiated with a CO(2) laser. Several control algorithms are investigated and the optimal control mode is obtained. A silver halide infrared fiber is used both to deliver the CO(2) laser radiation needed to irradiate the target and to deliver the thermal radiation emitted from the target back to the radiometer. Such a system can be useful in medical applications of CO(2) lasers.

Simple Model for Optimal Control of Tall Buildings

An objective of this paper is to study control design based on incomplete measured data. An approximate modal method is used to estimate the modal responses of the structure, based on incomplete measured data. An optimal modal control technique is used to obtain the necessary control forces. Another objective is to study passive control design by means of base isolation. The third objective is to study the combined effects of both active and passive control designs. Examples of optimal active control of a two-floor and an eight-floor building modeled by simple shear beams, without and with passive base-isolation devices, are performed to demonstrate the efficiencies of the various control designs. These designs are developed from placing actuators at different locations and collecting incomplete measured data from selected sensor locations. Results on the reduction of the dynamic responses of the example buildings are then quantified and discussed.

Optimal Control of Tall Buildings

An analysis of optimal modal control for tall buildings subjected to earthquake excitation is presented. The output feedback control system is applied under the circumstances that the state of the plant cannot be completely and accurately observed. Since time delay always exists and some of the information about the system behavior is not known precisely, the effect of time delay is investigated and sensitivity analysis is performed and illustrated with numerical examples. It is shown that both time delay and the constraint of feedback amplitude affect the efficiency of controllers, and the errors of natural frequencies of critical modes are found to be the main source of system error. If the system dynamics cannot be described precisely, the precision can be complemented through accurate observations.

Optimal control mode of a biochemical feedback system

An optimal feedback system for constant-value control of biochemical reaction system was investigated by computer simulations. A feedback system containing a cyclic enzyme system where two enzyme types share a substrate in a cyclic manner, was found to be the most reliable one. This feedback system has a capability to keep the stationary value of the end product at a desired level against not only exogenous substrate supply but also endogenous parametric disturbances. The cyclic enzyme system installed as a control element of this feedback system played the role of comparator in this feedback system. The control made of this feedback system was in good agreement with that of a system established by means of optimization technique based on the maximum principle. Also bang-bang control could be performed in this biochemical feedback system as well as in electrical one.

Optimization of linear variable-structure systems

AN ITERATIVE algorithm is described and proved for finding an optimal control that satisfies the conditions of Pontryagin's maximum principle. The main advantages of the algorithm from the practical stand-point are: universality in the class of variable-structure system, stability of the computational process, monotonic convergence to the required solution, and the capacity to discover, maintain, and evaluate the parameters of sliding optimal control modes.