Improved Control Algorithm Research Articles

Pole selection for structural control using the complex Fourier characteristics of the incoming earthquake

Structural control algorithms based on non-resonance theory are investigated. Specifically, a new approach for the selection of poles of the controlled system, based on complex Fourier coefficients of the incoming earthquake signal, suitable for pole allocation control algorithm, is proposed. The graphical representation of the complex Fourier coefficients of the incoming earthquake signal in the complex plane is used in order to choose the poles of the controlled system in such way that, first, resonance is avoided, and secondly, satisfactory levels of damping are obtained for each eigenmode, thus reducing the response. The potential applications and the effectiveness of the improved control algorithms are demonstrated by numerical examples. The simulation results indicate that a trade-off between the location of poles of the controlled structure and the structural response can be achieved. Copyright © 2006 John Wiley & Sons, Ltd.

Design of a Compact Series-Connected AC Voltage Regulator With an Improved Control Algorithm

This letter presents an improved control algorithm for the compensation of ac source voltage fluctuation. The proposed idea can be used to regulate both the overvoltage and undervoltage situations with only unidirectional energy transmission. Theoretical analysis has been achieved based on the power flow theory. A case study is demonstrated by means of a prototype experiment to prove its performance and effectiveness.

Development of an SMA Actuator for In-flight Rotor Blade Tracking

A new and improved solution to the helicopter blade-tracking problem has been investigated. A discrete, blade-installed actuator utilizing shape memory alloy (SMA) torsion tubes has been developed to enable in-flight rotor tracking. SMA torsion tubes from three materials were tested and one was selected for its cyclic stability. Improved tube fabrication, heating, end attachment methods, and locking schemes were developed. The final prototype actuator employed two biaxial SMA tubes for actuation/bias, an SMA-activated lock for power off operation, and integrated microprocessor control electronics. Tests under static and dynamic loading showed that actuation requirements, except for bandwidth, were met. Increased bandwidth may be obtained by improved control algorithms or cooling. The developed SMA actuator enables an in-flight, real-time adjustment of a blade-tracking tab. Projected payoffs are reduced maintenance cost as well as reduced helicopter vibrations and improved performance.

Effects of parasitics on the control of voltage source inverters

Advancements in AC industrial drives have been propelled through improvements in power electronics and control hardware. Improvements in insulated gate bipolar transistors (IGBTs) allowed faster switching speeds, which provides lower thermal losses. Digital signal processors and improved control algorithms allow AC drives to address applications previously handled by DC drives. Capacitive coupling between the IGBT, power structure, and control platform components influence drive dynamics and contributes to signal and waveform distortion. This differential and common mode capacitance is often disregarded as parasitics and not considered in designing the control. This paper decouples the major contributors to motor waveform distortion, analyzes them, quantifies them, and presents a correction strategy. Simulations validate the analysis and experimental results demonstrate the strategy's benefits.

Improved control algorithm for real‐time substructure testing

AbstractReal‐time substructure testing is a novel method of testing structures under dynamic loading. The complete structure is separated into two substructures, one of which is tested physically at large scale and in real time, so that time‐dependent non‐linear behaviour of the substructure is realistically represented. The second substructure represents the surrounding structure, which is modelled numerically. In the current formulation this numerical substructure is assumed to remain linear. The two substructures interact in real‐time so that the response of the complete structure, incorporating the non‐linear behaviour of the physical substructure, is accurately represented. This paper presents several improvements to the linear numerical modelling of substructures for use in explicit time‐stepping routines for real‐time substructure testing. An extrapolation of a first‐order‐hold discretization is used which increases the accuracy of the numerical model over more direct explicit methods. Additionally, an integral form of the equation of motion is used in order to reduce the effects of noise and to take into account variations of the input over a time‐step. In order to take advantage of this integral form, interpolation of the model output is performed in order to smooth the output. The improvements are demonstrated using a series of substructure tests on a simple portal frame. While the testing approach is suitable for cases in which the physical substructure behaves non‐linearly, the results presented here are for fully linear systems. This enables comparisons to be made with analytical solutions, as well as with the results of tests based on the central difference method. Copyright © 2001 John Wiley & Sons, Ltd.

OPTIMAL CONTROL OF WASTEWATER TREATMENT PLANTS VIA INTEGRATED NEURAL NETWORK AND GENETIC ALGORITHMS

The successful operation of wastewater treatment plants involves many uncertain factors. Not only the physical and chemical properties of wastewater streams but also the complexity of biological mechanism would significantly influence the performance of treatment process. Due to the rising concerns of environmental and economic impacts, improved control algorithms, using artificial intelligence technologies, have gradually received wide attention in the scientific community. This paper develops a genetic algorithm-based neural network for the assistance of intelligent controller design. An industrial wastewater treatment plant in Taiwan verified the applicability of such a methodology. The hybrid intelligent control technology applied in this paper is suitable to many other types of wastewater treatment plants by a slightly modified concept.

An improved control algorithm of shunt active filter for voltage regulation, harmonic elimination, power-factor correction, and balancing of nonlinear loads

This paper deals with an implementation of a new control algorithm for a three-phase shunt active filter to regulate load terminal voltage, eliminate harmonics, correct supply power-factor, and balance the nonlinear unbalanced loads. A three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC-VSI) with a DC bus capacitor is used as an active filter (AF). The control algorithm of the AF uses two closed loop PI controllers. The DC bus voltage of the AF and three-phase supply voltages are used as feedback signals in the PI controllers. The control algorithm of the AF provides three-phase reference supply currents. A carrier wave pulse width modulation (PWM) current controller is employed over the reference and sensed supply currents to generate gating pulses of IGBTs of the AF. Test results are presented and discussed to demonstrate the voltage regulation, harmonic elimination, power-factor correction and load balancing capabilities of the AF system.

DSP‐based implementation of an improved control algorithm of a three‐phase active filter for compensation of unbalanced non‐linear loads

AbstractThis paper deals with an implementation of a new control algorithm/or a three‐phase active filter (AF) to eliminate harmonics, compensate reactive power and to balance unbalanced non‐linear loads. An insulated‐gate‐bipolar transistor (IGBT)‐based current‐controlled pulse‐width modulated (PWM) voltage‐source inverter (VSI) with a DC‐bus capacitor is used as an AF. The reference supply currents are derived in phase with supply voltages using a sliding mode controller (SMC) over DC‐bus voltage of the AF.A digital signal processor (DSP) is used to implement the control algorithm of the AF. An indirect PWM current control over the reference and sensed supply currents is implemented for generating the gate signals for IGBT of the AF. Test results of the proposed AF are given to demonstrate the harmonic elimination, reactive power compensation and load‐balancing capabilities of the AF.

A control algorithm for three-phase three-wired active power filters under nonideal mains voltages

In this paper, a control algorithm for the performance improvement of three-phase three-wired active power filters under nonideal mains voltages is proposed and analyzed. It begins with an analysis of an instantaneous reactive power algorithm that was previously applied to the three-phase active power filter design. In that design, the circuit performance was found unsatisfactory under nonideal test scenarios. Our proposed design was, therefore, motivated in order to solve such problems. In the proposed scheme, not only was the control circuit simplified, but it also served as a potential candidate for the performance improvement of active filter design. The proposed algorithm has been implemented as a prototype. Results of experimental verification under various scenarios are presented.

An advanced electronic load governor for control of micro hydroelectric generation

This paper describes the original research and development of an electronic load governor which is microprocessor-based and incorporates three-phase balancing. The combined study and testing of the transient behaviour of the governor indicated the need for an improved control algorithm. The results of the implementation of the advanced algorithm in the control of micro hydroelectric power generation are presented and compared with the original algorithm.

An Improved Control Algorithm for an Electronic Load Governor

An Improved Control Algorithm for an Electronic Load Governor

Improvement of operation and availability of MSF plants

Ways to improve the safety, availability and efficiency of MSF plants by using improved control algorithms are described: state and adaptive proportional integral derivative (PID) controller or a self-setting function for conventional controllers. The efficiency of a single desalination line or of a complete plant may be improved by introducing optimization algorithms. Software packages monitoring the thermal and mechanical conditions of the plant allow early detection of faults and immediate initiation of counter-measures to avoid unplanned shutdowns, thus reducing costs and improving safety and availability of the hardware. Recent developments in diagnostic systems based on expert systems are discussed.

非線形摩擦を有する電動機速度制御系の特性解析と摩擦補償

Solid friction in machine elements is one of the dominant nonlinearities affecting the control accuracy of servo drive systems. Many schemes, including feedforward control, observer-based control and repetitive learning control have been proposed to compensate for nonlinear friction. These schemes show superior performance compared to that of the conventional P- and/or PI-controller; however, friction model errors and bandwidth restriction of the observer cause compensation errors, thus decreasing control accuracy. This paper presents a new control algorithm for performance improvement of a motor speed control system having nonlinear friction. By analyzing characteristics of conventional compensation control schemes during velocity reversal, the relation between control parameters and control accuracy is examined so as to explore problems with each scheme. Based on these analyses, a new feedforward control algorithm is proposed. The proposed algorithm is verified by analyses of control characteristics and experiments using a prototype. Experimental results show the superior performance improvement of the proposed algorithm.

Analysis and performance improvement of motor speed control system with nonlinear friction

AbstractSolid friction in machine elements is one of the dominant nonlinearities affecting the control accuracy of servo drive systems. Many schemes, including feedforward control, observer‐based control and repetitive learning control have been proposed to compensate for nonlinear friction. These schemes show superior performance compared to that of the conventional P‐ and/or PI‐controller; however, friction model errors and bandwidth restriction of the observer cause compensation errors, thus decreasing control accuracy.This paper presents a new control algorithm for performance improvement of a motor speed control system having nonlinear friction. By analyzing characteristics of conventional compensation control schemes during velocity reversal, the relation between control parameters and control accuracy is examined so as to explore problems with each scheme. Based on these analyses, a new feedforward control algorithm is proposed. The proposed algorithm is verified by analyses of control characteristics and experiments using a prototype. Experimental results show the superior performance improvement of the proposed algorithm.

Finite Element Analyses of Real-Time Stability Control in Sheet Forming Processes

Sheet metal forming processes involve the plastic deformation of a sheet of material into a desired shape. In practice, the uncontrolled variation of boundary and material conditions have made the continual reproducibility of a sheet forming process a very difficult operation. Recently, real-time control schemes based on simplified models of “average” in-process stresses and/or strains have provided a repeatability of end product quality in terms of final shape, failure modes, and/or material state. The success of these control schemes have warranted a more detailed investigation into the complete physics of the deformation process. This study takes one such operation, the axisymmetric cup-forming process, and conducts an off-line detailed analysis using the finite element method in order to obtain information on the state of the material during the deformation process. In our analysis, actual closed-loop feedback control laws which have previously been applied in experiments have been numerically simulated with a novel method of modifying the boundary conditions based on current conditions. This has lead to further understanding of the role of the control law in optimizing draw failure height. Our further investigation and analysis directly incorporates the predicted localized nature of failure of this process into the feedback loop and has lead to the construction of an improved control algorithm which has the potential of dramatically increasing the failure height and which can be used in on-line control of the process. The study clearly demonstrates the utility and power of using off-line detailed analyses which incorporate closed-loop feedback laws to obtain a better understanding of the physics of the deformations which occur during processing, and thereby greatly improve upon the algorithms which are used for real time control of forming or other processing.

SIZING AND LOCATING SURGE CAPACITY

Abstract Surge tanks for flow smoothing can represent a significant cost of a chemical plant. Several studies have addressed improved level control algorithms to optimize the use of an already specified surge volume. However, little attention has been given to optimally sizing and locating surge tankage in continuous processes. This research addresses this question. The strategy developed is applied to a multiple unit operation process and identifies one of several alternative control schemes as superior in terms of required surge tankage.

Diesel Engine Control Based on an ARMA Model

ABSTRACT This paper reports the modifications made to a microprocessor-based engine control system, which was previously reported (Zhang et al., 1987). The system was designed to improve the operating efficiency of a tractor diesel engine. Hardware improvements included adding instrumentation for sensing governor setting and modifying the driving mechanism for controlling the governor control lever. An ARMA model was developed to describe the dynamics of the engine-governor system. Lag-lead compensation algorithms based on the model were designed. Laboratory tests showed significant improvements in engine control performance with the improved control algorithms and the modified system hardware.

An improved control algorithm for an artificial beta-cell.

With the successful implementation of a computer analog for (ß-cell function to restore normal glucose tolerance in diabetic patients, one of the major obstacles to the ultimate development of an implantable ``artificial pancreas'' was overcome. The next step was to optimize the original algorithm and simplify the operation of the blood sugar control system to make it more amenable to miniaturization.

A Mathematical Model Of Premature BabyThermoregulation And Infant Incubator Dynamics

A thermodynamic mathematical model of premature infants placed in an infant incubator was developed in order to improve the control algorithm of this incubator. The premature infant's head was represented by a sphere, and the trunk and upper and lower extremities were represented by three cylinders. The sphere and cylinders were divided into two or three concentric layers to represent skin, muscle and core as appropriate for each anatomical structure. Heat flow between adjacent layers was modeled by conduction, and all layers exchanged heat by convection with a central blood compartment. All four skin layers exchanged heat with the environment by convection, radiation, and evaporation. Signals which were proportional to deviations from temperature set points in the brain and in skin were supplied to the model's regulator. The regulator then caused changes in the peripheral blood flow to occur in the skin layers of the appropriate segment in the body. A spatially lumped mathematical model of an infant incubator was developed based on accepted thermodynamic principles. The validity of the baby model was tested in 5 healthy premature newboms (body weight 1,210-1,740 g). The difference between experimental data from direct and indirect calorimetry and the model results averaged 0.1 ± 0.1, 0.2 ± 0.1 and 0.2 ± 0.2 (mean ± SE) °C for the rectum, trunk and head temperatures, respectively. The incubator model showed steady state error less than ± 0.1 °C for air and internal wall temperatures in the air servocontrol mode. The fall in air temperature for the simulation of opening of the front port of the incubator for five minutes was 1.4 °C. After closure of the front panel the incubator model showed a return to the initial temperature in less than 2 minutes. These results are in agreement with published data for this kind of incubator. In conclusion, the model is a good tool for designing improved control algorithms of incubators.