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Purpose To develop a simplified aluminum compensator system for total body irradiation (TBI) that is easy to assemble and modify in a short period of time for customized patient treatments. Methods The compensator is composed of a combination of 0.3 cm thick aluminum bars, two aluminum T‐tracks, spacers, and metal bolts. The system is mounted onto a plexiglass block tray. The design consists of 11 fixed sectors spanning from the patient's head to feet. The outermost sectors utilize 7.6 cm wide aluminum bars, while the remaining sectors use 2.5 cm wide aluminum bars. There is a magnification factor of 5 from the compensator to the patient treatment plane. Each bar of aluminum is interconnected at each adjacent sector with a tongue and groove arrangement and fastened to the T‐track using a metal washer, bolt, and nut. Inter‐bar leakage of the compensator was tested using a water tank and diode. End‐to‐end measurements were performed with an ion chamber in a solid water phantom and also with a RANDO phantom using internal and external optically stimulated luminescent detectors (OSLDs). In‐vivo patient measurements from the first 20 patients treated with this aluminum compensator were compared to those from 20 patients treated with our previously used lead compensator system. Results The compensator assembly time was reduced to 20–30 min compared to the 2–4 h it would take with the previous lead design. All end‐to‐end measurements were within 10% of that expected. The median absolute in‐vivo error for the aluminum compensator was 3.7%, with 93.8% of measurements being within 10% of that expected. The median error for the lead compensator system was 5.3%, with 85.1% being within 10% of that expected. Conclusion This design has become the standard compensator at our clinic. It allows for quick assembly and customization along with meeting the Task Group 29 recommendations for dose uniformity.

To improve the robustness and stability of the LCL inverter connected to weak grid, this paper proposes a novel active damping based on voltage of point common coupling ( $\text{v}_{pcc}$ ) feedback. A phase lead compensator is proposed in the $\text{v}_{pcc}$ feedback loop to compensate system phase margin (PM). Theoretical analysis of the effectiveness, detailed parameter setting, stability analysis for proposed active damping adopting lead compensator, named as LC AD, are all described. Simulation and experiment results show that comparing to conventional high pass filter (HPF) AD, the proposed LC AD provides more effective damping effect for the LCL inverter adopting quasi-proportional resonant (QPR) controller under weak grid.

This paper analyses Disturbance Observer- (DOb-) based robust force control systems in the discrete-time domain. The robust force controller is implemented using velocity and acceleration measurements. A DOb is employed in an inner-loop to achieve robustness, and another DOb, viz. Reaction Force Observer (RFOb), is employed in an outer-loop to estimate interaction forces and improve the performance of force control. First, the inner-loop is analysed. It is shown that the DOb works as a phase-lead/lag compensator tuned by the nominal design parameters in the inner-loop. The phase margin of the inner-loop controller and the bandwidth of the velocity-based (i.e., conventional) DOb are constrained not only by noise-sensitivity but also by the waterbed effect. This explains why we observe unstable responses as the bandwidth of the conventional DOb increases in practice. To eliminate the design constraint due to the waterbed effect, this paper proposes an acceleration-based DOb. Then, the robust force controller is analysed. It is shown that the design parameters of the RFOb have a notable effect on the stability of the robust force control system. For example, the robust force controller has a non-minimum phase zero (zeros) when the RFOb is not properly tuned. This may cause severe stability and performance problems when conducting force control applications. By using the stability and robustness analyses, this paper proposes new design tools which enable one to synthesize a high-performance robust force control system. Simulations and experiments are presented to validate the proposed analysis and synthesis methods.

This paper discusses the use of a stochastic metaheuristic population-based optimization algorithm known as the sine cosine algorithm (SCA) to design the parameters of a power system stabilizer (PSS) for damping electromechanical oscillations in a single machine connected to a large power system. The design of the PSS parameters was formulated as an optimization problem to minimize the objective function value. The SCA was used to obtain the best values of the PSS parameters under the objective function. Simulation was carried out by a linearized power system model. The lead lag controller was used as the PSS structure and the results from that were compared with those obtained by moth flame optimization and evolutionary programming. The results showed that the SCA is more effective than are the other techniques in exploration and exploitation to tune the PSS parameters and enhance the power system stability by damping oscillations in a range of loading conditions.

Dynamic inverse- (DI-) based control technique has been utilized in many applications and proven to be effective. Recently, the inverse dynamic control (IDC), an expansion to the classical DI technique, has been trending with implementation in many areas. It has been proved that IDC is capable of overcoming some limitations in DI-based techniques, particularly in cancellation of useful nonlinearities. This paper extends the implementation of IDC on the positional and speed control of the linear servo cart system. Simulation results further proves that IDC is an effective and robust controller evidently when comparing it with the proportional velocity and lead compensator controller.

Power System Stabilizer (PSS) is an important measure to increase damping and suppress low frequency oscillations of power system. During PSS test, the time constant of lead-lag compensator need to be configured, considering the inefficiency and optimization problem when configuring parameters empirically, this paper proposes automatic configuration method of PSS parameters based on Matlab, by setting the expected phase value at each frequency and constructing the objective function with the sum of phase differences square, the automatic calculation of PSS parameters under specific phase requirements at each frequency can be realized, the detailed steps of this method are given, and the method is verified during the PSS test of an 300Mw thermal-power generating unit finally.

Motivated by the empirical evidence of high-frequency lead-lag effects and cross-asset linkages, we introduce a multi-asset price formation model which generalizes standard univariate microstructure models of lagged price adjustment. Econometric inference on such model provides: (i) a unified statistical test for the presence of lead-lag correlations in the latent price process and for the existence of a multi-asset price formation mechanism; (ii) separate estimation of contemporaneous and lagged dependencies; (iii) an unbiased estimator of the integrated covariance of the efficient martingale price process that is robust to microstructure noise, asynchronous trading, and lead-lag dependencies. Through an extensive simulation study, we compare the proposed estimator to alternative approaches and show its advantages in recovering the true lead-lag structure of the latent price process. Our application to a set of NYSE stocks provides empirical evidence for the existence of a multi-asset price formation mechanism and sheds light on its market microstructure determinants. Supplementary materials for this article are available online.

For high-fidelity quantum operations in ion traps, it is important to maintain the secular frequency of the trapped ions at a constant value. The radial secular frequency is proportional to the amplitude of the radio frequency (RF) signal applied to ion traps. Owing to the changes in the ambient temperature of a helical resonator and the minute vibration of the optical table, the amplitude can vary. Recently, a method for reducing the fluctuation in the RF signal amplitude, using a commercial universal proportional-plus-integral (PI) controller, has been introduced, which, in turn, reduces the secular frequency drift of the trapped ions. The method improves the capability to maintain the secular frequency at a constant value. However, the structure of the controller is fixed, thus, the control method cannot be changed to suit different experimental conditions, and the different feedback configuration cannot be implemented to increase the resolution. In this paper, we develop a field-programmable gate array (FPGA)-based feedback controller that allows the implementation of various automatic control methods and feedback configurations. In our experiments, the fluctuation in the amplitude of the RF signal was 1.806% using a commercial universal PI controller. The fluctuation was reduced to 0.099% using the developed FPGA-based PI controller, and to 0.102% using the developed FPGA-based lag compensator. By employing the developed FPGA control method, many other automating control methods can be applied to achieve a stable and high-performance control of the secular frequency.

Traditional power systems based on synchronous generators often feature low frequency electromechanical oscillations. However, the integration of renewable energy sources through power converters can help tackling this issue. In fact, thanks to the concept of Virtual Synchronous Machine (VSM), it is possible to make the inverters behave as real synchronous machines (SMs). This way, the inverters can be integrated into the grid as traditional SMs and can even outperform them when it comes to damping low frequency oscillations in the power system. In order to do that, proper damping algorithms must be adopted in the VSM model. Therefore, this paper presents a simple and straighforward damping method for VSMs based on a single lead-lag filter acting on the VSM active power feedback. The proposed method and its integration in the VSM model are described. Then, the proposed solution has been experimentally compared to conventional methods, along with comparison metrics, to highlight its benefits.

The full-scale fatigue test of rotor blades is an important and complex part of the development of new wind turbines. It is often done for certification according to the current IEC (2014) and DNV GL AS (2015) standards. Typically, a new blade design is tested by separate uniaxial fatigue tests in both main directions of the blade, i.e. flapwise and lead lag. These tests are time-consuming and rather expensive due to the high number of load cycles required, up to 5 million. Therefore, it is important to run the test as efficiently as possible. During fatigue testing, the rotor blade is excited at or near its resonant frequency. The trend for new rotor blade designs is toward longer blades, leading to a significant drop in their natural frequencies and a corresponding increase in test time. To reduce the total test time, a novel test method aims to combine the two consecutive uniaxial fatigue tests into one biaxial test. The biaxial test excites the blade in both directions at the same time and at the same frequency, resulting in an elliptical deflection path of the blade axis. Using elliptical loading, the counting of damage equivalent load cycles is simplified in comparison to biaxial tests with multiple frequencies. In addition, the maximum loads in both main directions remain separated, while off-axis loading is introduced. To achieve such a test, specific load elements need to be arranged so as to equalize the natural frequencies of the test setup for both test directions. This is accomplished by adding stiffness or inertial effects in a specific direction. This work describes a new method to design suitable test setups. A parameterized finite element (FE) model of the test with beam elements for the blade represents the test setup. A harmonic analysis on the FE model can identify the load distribution and the test conditions of a specific test setup within seconds. An optimization algorithm that varies parameters of the model and searches for the optimal setup is then applied to the analysis. This approach allows the efficient determination of a test setup, suited to the predefined requirements. The method is validated by applying it to three different test scenarios for a modern rotor blade: (a) state-of-the-art uniaxial setups, (b) uniaxial setups including springs and (c) a biaxial setup. In conclusion, the resulting setups are evaluated in terms of test quality and efficiency.

Several active damping strategies have been proposed in the literature for grid-connected converters with LCL filter but there are not specific strategies for DFIG wind turbines. In this system, there is an interaction between the two converters of the back-to-back conversion structure, which must be properly modeled in order to design effective damping strategies for the LCL filter resonant poles. This paper proposes a robust active damping strategy for DFIG wind turbines with LCL filter that considers the special features of this system. In this technique the filter capacitor current is fed back through a lag compensator that adjusts the delay of the feedback loop to emulate a virtual impedance that has dominant resistive behavior in the range of possible resonance frequencies. It is shown that a similar damping of the LCL filter resonance is achieved when the strategy isimplemented in either of the two converters. This work was supported by the Spanish State Research Agency (AEI) under grants PID2019-110956RB-I00 /AEI/10.13039 and DPI-2016-80641-R.

Mechanical shim is an advanced technology for reactor power and axial offset control with control rod assemblies. To address the adverse accuracy impact on the ex-core power range neutron flux measurements-based axial offset control resulting from the variable positions of control rod assemblies, the lead-lag-compensated in-core self-powered vanadium detector signals are utilized. The prompt γ current of self-powered detector is ignored normally due to its weakness compared with the delayed β current, although it promptly reflects the flux change of the core. Based on the features of the prompt γ current, a method for configuration of the lead-lag dynamic compensator is proposed. The simulations indicate that the method can improve dynamic response significantly with negligible adverse effects on the steady response. The robustness of the design implies that the method is of great value for engineering applications.

We propose a method to infer lead-lag networks of traders from the observation of their trade record as well as to reconstruct their state of supply and demand when they do not trade. The method relies on the Kinetic Ising model to describe how information propagates among traders, assigning a positive or negative "opinion" to all agents about whether the traded asset price will go up or down. This opinion is reflected by their trading behavior, but whenever the trader is not active in a given time window, a missing value will arise. Using a recently developed inference algorithm, we are able to reconstruct a lead-lag network and to estimate the unobserved opinions, giving a clearer picture about the state of supply and demand in the market at all times. We apply our method to a dataset of clients of a major dealer in the Foreign Exchange market at the 5 minutes time scale. We identify leading players in the market and define a herding measure based on the observed and inferred opinions. We show the causal link between herding and liquidity in the inter-dealer market used by dealers to rebalance their inventories.

This paper investigates the human controllers’ sensitivity to added first-order lag-lead and lead-lag dy- namics in the controlled system dynamics using a cybernetic approach and a dedicated human-in-the-loop experiment. The extent to which human controllers will adapt their control dynamics to these added dynamics is objectively determined and explicitly compared to Maximum Unnoticeable Added Dynamics (MUAD) en- velopes from literature. Human control adaptation to added lag-lead and lead-lag dynamics is predicted for a wide range of lead and lag time-constants using offline human control model simulations, while a smaller subset of eight added dynamics settings, supplemented with a baseline condition, is tested in the experiment. Both the simulation predictions and experiment data show that human controllers will significantly adapt their control gains and lead time-constants to added lag-lead or lead-lag dynamics. Overall stronger adaptation is observed with added lag (i.e., high added dynamics lag time constants), which requires human controllers to generate more compensating lead equalization and results in degraded task performance. Collected sub- jective rating data also confirmed that added lag-lead dynamics were more noticeable for human controllers than added lead-lag. While overall these findings correspond well with literature, our experiment data shows that even for some conditions with added dynamics that remained within the MUAD boundaries statistically significant changes in human control gain and lead time-constants, compared to the baseline condition, occur.

The objective of this paper is the joint application of two different methodological concepts for the detection of lead-lag relationships in economic time-series in order to investigate their consistency and their potential complementarity. The first methodology, a time domain analysis based on vector error correction model, provides evidence about the existence of long-run equilibrium of the time-series and the short-run lead-lag behaviors. The second methodology, a time-frequency concept based on the phase difference of the cross-wavelet coherence, analyzes the lead-lag relationships across various timescales and reveals the altering of leadership over time. The two methods are applied to time-series of wealth-to-income ratio of four developed countries over the period 1970–2010 and analyze the lead-lag relationships of the countries in the long-run and in the short-run. The results show that the two methods are consistent in their major long-run findings, however, they reveal different aspects regarding the short-run dynamics of the lead-lag relationships. Furthermore, the results suggest the complementarity of the two methodologies in the context of a complete framework for the analysis of the lead-lag relationships in non-stationary economic time-series.

Twin rotor system is a laboratory setup resembling a simplified helicopter model that moves along both horizontal and vertical axes. The literature on control of twin rotor systems reflects a good amount of research on designing PID controllers and their extensions considering several aspects, as well as onsome nonlinear controllers. However, there is almost no previous work on design of lag-lead type compensators for twin rotor systems. In this study, by considering this open research problem, lag and lead type compensators are designed and then experimentally verified on the twin rotor system. Specifically, first, lag and lag-lag compensators are designed to obtain a reduced steady state error as compared with proportional controllers. Secondly, lead compensation is discussed to obtain a reduced overshoot. Finally, lag-lead compensators are designed to make use of their favorable properties. All compensators are applied to the twin rotor system in our laboratory. From experimental studies, it was observed that steady state error was reduced when a lag compensator was used in conjunction with a lead compensator.

To damp the LCL -filter resonance in a grid-connected inverter, the feedback of capacitor current is usually adopted, and it can be replaced by the feedback of capacitor voltage as a low-cost solution, if an accurate digital differentiator can be made. The best way for realizing such a differentiator has so far proved to be an indirect nonideal generalized integrator (GI). As a simple alternative, this paper proposes two digital differentiators, which are directly developed in the discrete domain. They are a first-order differentiator based on backward Euler plus digital lead compensator and a second-order differentiator based on Tustin plus digital notch filter. The basic idea of the proposed methods is to correct their frequency responses to match the ideal differentiator with embedded digital filters. It is shown that the proposed differentiators exhibit the same derivative performance as the nonideal-GI differentiator, and they are more attractive for digital implementations due to their direct discrete natures, compact expressions, and easy algebraic manipulations. In particular, the proposed first-order differentiator is most competitive for its general representation and simplest implementation. Finally, a 12-kW prototype is built, and experiments are performed to verify the theoretical analysis.

We employ the thermal optimal path method to explore both the long-term and short-term interaction patterns between the onshore CNY and offshore CNH exchange rates (2012-2015). For the daily data, the CNY and CNH exchange rates show a weak alternate lead-lag structure in most of the time periods. When CNY and CNH display a large disparity, the lead-lag relationship is uncertain and depends on the prevailing market factors. The minute-scale interaction pattern between the CNY and CNH exchange rates change over time according to different market situations. We find that US dollar appreciation is associated with a lead-lag relationship running from offshore to onshore, while a (contrarian) Renminbi appreciation is associated with a lead-lag relationship running from onshore to offshore. These results are robust with respect to different sub-sample analyses and variations of the key smoothing parameter of the TOP method.

To our knowledge, this paper is the first study on the effect of information arrival on the lead–lag relationship amongst related spot instruments. Based on a large data-set of ultra-high-frequency transaction prices time-stamped to the millisecond of the S&P500 index and its two most liquid tracking ETFs, we find that their lead–lag relationship is affected by the rate of information arrival whose proxy is the unexpected trading volume of these instruments. Specifically, when information arrives, the leadership of the leading instrument may strengthen or weaken depending on whether the leading or lagging instrument responds to that information. An increase in the unexpected volume of the leader strengthens its leadership whereas an increase in the unexpected volume of the lagger weakens this leadership. In addition to the strength of leadership, an increase in the unexpected volume in response to information arrival may also have opposite effects on the lead–lag correlation coefficient depending on whether that volume increase belongs to the leader or the lagger. Finally, we find that sophisticated investors have a more significant effect on the lead–lag relationship than non-sophisticated ones.

For a classic PLL with square waveform signals and lead-lag filter for all possible parameters lock-in range is computed and corresponding diagrams are given.

In this paper, a small-signal dynamic model of a single-machine infinite-bus (SMIB) power system that includes IEEE type-ST1 excitation system and PSS based on transfer fu¬n¬c¬¬tion structure is presented. The changes in the operating co¬n¬dition of a power system on dynamic performance have been exa¬m¬ined. The dynamic performance of the closed-loop system is ana¬lyzed base on its eigenvalues. The effectiveness of the par¬a¬m¬e¬t¬ers changes on dynamic stability is verified by simulation res¬u¬l¬ts. Three types of PSS have been considered for analysis: (a) the derivative PSS, (b) the lead-lag PSS or conventional PSS, and (c) the proportional-integral-derivative PSS. The objective fu¬nc¬t¬i¬o¬n is formulated to increase the dam¬¬ping ratio of the electromechanical mode eigenvalues. Simu¬la¬tion results show that the PID-PSS performs better for less ov¬e¬r¬shoot and less settling time comp¬ared with the CPSS and DPSS un¬der different load ope¬ration and the significant system pa¬r¬am¬eter variation conditions.

Goal. The aim of this paper is to conduct a comprehensive comparative analysis between five different controllers for a drug infusion system in total intravenous anesthesia (TIVA) administration. Methods. The proposed method models a dilution chamber with first order exponential decay characteristics to represent the pharmacokinetic decay of a drug. The dilution chamber is integrated with five different control techniques with a simulation-based comparative analysis performed between them. The design process is conducted using MATLAB SISOTOOL. Results. The findings show that each controller has its own merits and demerits. The results generated using MATLAB signify and confirm the effectiveness of PI and cascaded lead controllers, with cascaded lead controller as the best control technique to automate and control the propofol delivery. Conclusion. In this paper, different control techniques for measurement-based feedback-controlled propofol delivery is confirmed with promising results. Significance. The comparative analysis showed that this drug infusion platform, merged with the proper control technique, will perform eminently in the field of total intravenous anesthesia.

With the improvement of performance in the ultra-precision manufacturing engineering, the requirements for vibration isolation have become more stringent. In order to obtain a wider effective bandwidth and a higher performance of a multi-DOFs active vibration isolation system (AVIS), active hybrid control (AHC) technology is applied in this paper. AHC technology comprises a feedback active control (FBAC) technology and a feedforward active control (FFAC) technology. Absolute velocity feedback is employed to establish a sky-hook damping technology in FBAC technology. Velocity feedforward of base platform is adopted to build a lead-lag phase compensation (LLPC) technology in FFAC technology. Further, a coordinate vector conversion from unit level to system level is mentioned to describe the dynamic characteristic of the six DOFs AVIS applied in the ultra-precision field. And with the assistance of the transformed coordinate vector, the dynamic model of system level is built. Based on the establishment of the dynamic model and the research of AHC, an experimental platform which constitutes three vibration isolators and a real-time active control system is set up. The experimental results indicate that the amplitude of the resonant peak is further reduced significantly, compared to the general feedback control. And simultaneously active effective bandwidth is extended. AHC technology with sky-hook damping algorithm and LLPC control algorithm is verified to be more effective.

We propose a novel framework to investigate lead-lag relationships between two financial assets. Our framework bridges a gap between continuous-time modeling based on Brownian motion and the existing wavelet methods for lead-lag analysis based on discrete-time models and enables us to analyze the multi-scale structure of lead-lag effects. We also present a statistical methodology for the scale-by-scale analysis of lead-lag effects in the proposed framework and develop an asymptotic theory applicable to a situation including stochastic volatilities and irregular sampling. Finally, we report several numerical experiments to demonstrate how our framework works in practice., 37 pages, 2 figures. To appear in SIAM Journal on Financial Mathematics

The performance of current and voltage regulators during transients and steady-state is of primary concern for power converters intended for stand-alone applications. Dynamics performance and command tracking capability are enhanced by actively decoupling the controlled states variables. To further widen the current loop bandwidth while still preserving a well-damped system a lead compensator structure on the forward loop is proposed. A 3 kHz bandwidth with 0.707 damping factor is achieved for the inner current controller. Accordingly, also the voltage regulator bandwidth can be widen, thus requiring even more a proper anti-wind up scheme to avoid saturation of the integral term during demanding transients. Lab-tests are performed in accordance with standards imposed to uninterruptible power supplies, verifying the theoretical analysis.

State feedback decoupling permits to achieve a better dynamic response for Voltage Source in stand-alone applications. The design of current and voltage regulators is performed in the discrete-time domain since it provides better accuracy and allows direct pole placement. As the attainable bandwidth of the current loop is mainly limited by computational and PWM delays, a lead compensator structure is proposed to overcome this limitation. The design of the voltage regulator is based on the Nyquist criterion, verifying to guarantee a high sensitivity peak. Discrete-time domain implementation issues of an anti-wind up scheme are discussed as well. Laboratory tests in compliance with the standard for UPS systems (IEC 62040-3) are performed to validate the theoretical analysis.

Electric vehicles (EVs) has received an increasing interest from the power community and have become increasingly popular due to their importance in fighting climate change. An advanced power electronic converter remains the main and common topic for research in this area. In this paper, an advanced sliding mode control (ASMC) is designed for Four Phase Interleaved Boost Converter (FP-IBC). The novelty of the proposed controller relies on the use of an adaptive delay-time block with the conventional sliding mode control scheme which is designed based on chattering elimination method. The new scheme succeed to reduce the ripple contents in the converter's output voltage and inputs currents, and achieve fast convergence and transient response. An experimental comparison study has been investigated between the proposed controller and Self-tuning Lead Lag Compensator (SLLC). The comparison study is performed at different loading conditions using Super-Capacitor (SC) module. The experimental results show that the dynamic response of FP-IBC is significantly improved based on the proposed control design.

A model reference controller was designed for a unstable second-order system with time delay. The method basically derives the control law so as to make the error dynamics decay as per a third-order model. The resultant feedback control system was that of a lead-lag filter on the measurement y and a conventional Proportional - Integral - Derivative (PID) controller with a lead-lag filter in the forward path. The performance of the control system for both the servo and regulatory problems was better than that of Panda (Chemical Engineering Science, 64, pp. 2807-2816, 2009). The controller is robust for uncertainties in the model parameters such as time delay, time constant or process gain. � 2013 Copyright Indian Institute of Chemical Engineers.

To achieve high-speed, high-precision position control for semiconductor product machines and industrial robots, it is well known that PID control is widely applied (Kojima, T., 2004). Many PID control methods have been proposed for such a system so far. In general, proportional position control and proportional plus integral velocity control or integral plus proportional velocity control (P,PI/I-P), which is a type of proportional plus integral plus deferential control (PID), is applied in many industrial applications in Japan. However, the parameters of the control of P,PI/I-P must be changed to maintain a good motion performance when the characteristic of the control target change. As a method to compensate for a change of the control target, a disturbance observer is proposed (Ohishi, K. et al., 1999). Using this method, a load disturbance force is estimated based on a model set beforehand and adds an estimated disturbance force to a control input. However, it might cause the deterioration of the control performance when a control target model is different from real control target greatly. Furthermore, it is difficult to get a correct model because a lot of nonlinear elements such as the friction may change in control target in time and environment (Canudas-de-Wit, C. et al., 1995; Lischinsky, P. et al., 1999; Futami, S. et al., 1990; Otsuka, J. & Masuda, T., 1998; Iwasaki, M. et al., 2000; Tsuruta, K. et al., 2000, 2003). In addition, based on a control target model estimated in real time, the method to change the several control parameters is proposed to compensate it for a change of the control target (Kuwon, T. et al., 2006), but might cause the deterioration of the control response under the influence of an estimate error. Therefore, adaptive control (Suzuki, T., 2001; Sato, K. et al., 2005, 2006, 2007, 2008) and sliding mode control (Nonami, K. & Den, H., 1994; Utkin, V, I., 1977; Harashima, F. & Hashimoto, H., 1986; Fujimoto, T. et al., 2006) are given to solve these problems. However, that is hard to understand these methods to the engineer who got used to PID control; have a problem. In this chapter, we propose a new P,PI/I-P control method that includes a nonlinear compensator, that it is easy to understand for a PID control designer. The control objective is to get a high-speed and high-precision positioning response regardless of the case of control references or load characteristics change. The algorithm of the nonlinear compensator is based on sliding mode control with chattering compensation. The effectiveness of the proposed control method is evaluated with three kinds of single-axis slide system experimentally. The first experiment system is two slider tables comprised of an AC servo motor, a coupling and a ball-screw, the second one is a

The paper presents a direct digital method to the design of a discrete lead-lag compensator for a robust control. The design specifications on phase margin, gain margin and crossover frequency of the close-loop system can be obtained by using numerical and graphical solutions. The discrete design method proposed in the paper is also compared with the continuous-time case. Some numerical examples are presented. The proposed method can be useful both on educational and industrial environments.

In this article an approach based on inversion formulae is used for the design of lead–lag compensators which satisfy frequency domain specifications on phase margin, gain margin and phase (or gain) crossover frequency. An analytical and graphical procedure for the compensator design on the Nyquist and Nichols planes is presented with some numerical examples.

In this paper three different methods for the synthesis of lead-lag compensators that meet design specifications on the phase margin and the gain crossover frequency are presented. These numerical and graphical methods are based on the choice of a degree of freedom of the regulators. These procedures aim to satisfy an additional specification for robust control: the gain margin, the complementary modulus margin or a specification on the settling time of the controlled system.

Existing hydraulic dampers are passive devices, and their damping characteristics cannot be adapted to the varying damping needs of each different flight condition of a rotorcraft. Therefore, dampers and their interfaces to the rotor system are constantly subjected to large damping forces, which contribute to their damage and wear. In this work, we consider the possible use of a bypass valve as a means to reduce loads while still providing the required amount of damping for safe flight. Two different policies for the use of the bypass are considered: In the first and simplest of the two, the valve is opened of a constant amount, which varies only as a function of the vehicle flight speed, whereas in the second the valve aperture is modulated as a function of blade azimuth using a higher harmonic feedback law. The investigation on the load-reduction capabilities of the bypass augmented damper is conducted by using validated mathematical models of the A109E Power helicopter and of its damper. It is found that both policies are capable of delivering the required level of damping at substantially reduced loads, which for the speed-scheduled aperture drop at values that range between 30% and 60%, depending on the flight condition, of the loads generated by the standard passive device, and for the higher harmonic modulated law at values around 20%–25%.

2010 IEEE PES Transmission and Distribution Conference and Exposition: Smart Solutions for a Changing World --19 April 2010 through 22 April 2010 -- New Orleans, LA -- STATCOM controlled power system shows highlynon-linear characteristics. In such a structure, linear controllers are easy to apply but difficult to tune. Fine tuning of controller parameters is necessary to meet transient performance requirements. In this paper, control system parameters of a STATCOM which is constructed from two six-pulse voltage source based converters are optimized by Simplex algorithm which is a non-linear and non-gradient method. System objective function to be minimized is based on a performance index and expressed in terms of measured and desired values of system variables. After optimization, performance of STATCOM control system consisting of two PI controllers and two leag/lag compensators has been tested and verified through a number of simulation studies investigating step-response performance. Precise and quick responses have been observed with optimized parameters. © 2010 IEEE.

Using the direct synthesis method, a PID controller in series with a lead/lag compensator is designed for control of open loop integrating processes with time delay. Set-point weighting is considered for reducing the undesirable overshoot. Guidelines are provided for selection of the desired closed loop tuning parameter in the direct synthesis method and set point weighting parameter. The method gives significant load disturbance rejection performances. Illustrative examples are considered to show the performances of the proposed method. Significant improvement is obtained when compared to recently reported methods. � 2008 The Franklin Institute.

This paper proposes a novel hybrid motion- sensorless control system for permanent magnet synchronous motors (PMSM) using a new robust start-up method called I-f control, and a smooth transition to emf-based vector control. The I-f method is based on separate control of id, iq currents with the reference currents id* = 0 and iq* constant, and the reference frequency having ramp variation. This solution allows ultra low- speed sensorless control without initial rotor-position estimation, and without machine parameters identification. A first-order lag compensator is employed to ensure a smooth transition from I-f to emf sensorless vector control when the frequency reaches a certain level, and back. The PMSM rotor position and speed are extracted by using a PLL state-observer from the estimated rotor-flux, which is based on an equivalent integrator in close- loop with a PI speed-adaptive compensator to eliminate dc-offset and phase-delay. Digital simulations for PMSM start-up with full load torque are presented for different initial rotor-positions. The transitions from I-f to emf motion-sensorless vector control and back as well, at very low-speeds, are fully validated by experimental results. This method is suitable for both surface and interior PMSMs, but the paper refers directly only to surface PMSM. Other field of application might be in wind generators safe (faster) self-starting when they are connected to the grid, or moving the rotor a little for inspections/repairs, and for general industrial variable speed drives where slightly hesitant but full- load self-starting is allowable. This paper proposes a novel hybrid motion- sensorless control system for permanent magnet synchronous motors (PMSM) using a new robust start-up method called I-f control, and a smooth transition to emf-based vector control. The I-f method is based on separate control of id, iq currents with the reference currents id* = 0 and iq* constant, and the reference frequency having ramp variation. This solution allows ultra low- speed sensorless control without initial rotor-position estimation, and without machine parameters identification. A first-order lag compensator is employed to ensure a smooth transition from I-f to emf sensorless vector control when the frequency reaches a certain level, and back. The PMSM rotor position and speed are extracted by using a PLL state-observer from the estimated rotor-flux, which is based on an equivalent integrator in close- loop with a PI speed-adaptive compensator to eliminate dc-offset and phase-delay. Digital simulations for PMSM start-up with full load torque are presented for different initial rotor-positions. The transitions from I-f to emf motion-sensorless vector control and back as well, at very low-speeds, are fully validated by experimental results. This method is suitable for both surface and interior PMSMs, but the paper refers directly only to surface PMSM. Other field of application might be in wind generators safe (faster) self-starting when they are connected to the grid, or moving the rotor a little for inspections/repairs, and for general industrial variable speed drives where slightly hesitant but full- load self-starting is allowable.

A lead or lag compensator in series with a proportional-integral-derivative (PID) controller is designed for unstable processes with two unstable poles and a zero with time delay. Such transfer functions arise in modeling an isothermal continuous stirred tank reactor (CSTR) carrying out autocatalytic reactions, in crystallizers and in nonisothermal CSTRs. The direct synthesis method is used for the design of the controller. The desired closed-loop transfer function is specified to get the required PID controller with lead/lag compensator. Simulation studies are given to show the effectiveness of the proposed method. For systems with and without negative zero, significant improvement is obtained when compared to the method proposed by Lee et al., (Chem. Eng. Sci. 2000; 55: 3481–3493). Copyright © 2006 Curtin University of Technology and John Wiley & Sons, Ltd.

A discrete-time predictive current controller, for the application of active power filtering, is designed and analyzed in this paper. A modified algorithm of reference current prediction in the conditions of step change in amplitude and/or frequency is proposed. The theoretical analysis and the validity of the proposed method are verified by simulations. Comparison for the 5th and the 7th harmonic current control is made with the results achieved using synchronous PI plus lead compensator.

Fuzzy model based predictive functional controller (FPFC) is applied to the magnetic suspension system - a pilot plant for magnetic bearing. High quality control requirements are short settle time with a-periodical step response and zero steady-state error. Open loop unstable process was stabilised with linear lead compensator. The FPFC was used as a cascade controller. Due to some model uncertainties, the Takagi-Sugeno fuzzy model of stabilised system was obtained using fuzzy identification. Comparing to PID, it improved quality and robustness performance. With its computational efficiency, it proved to be ideal solution for high sampling frequency. Fil: Lepetic, Marko. University of Ljubljana; Eslovenia Fil: Skrjanc, Igor. University of Ljubljana; Eslovenia Fil: Chiacchiarini, Hector Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; Argentina Fil: Matko, Drago. University of Ljubljana; Eslovenia

This paper examines the lead–lag relationship between the FTSE 100 index and index futures price employing a number of time series models. Using 10-min observations from June 1996–1997, it is found that lagged changes in the futures price can help to predict changes in the spot price. The best forecasting model is of the error correction type, allowing for the theoretical difference between spot and futures prices according to the cost of carry relationship. This predictive ability is in turn utilised to derive a trading strategy which is tested under real-world conditions to search for systematic profitable trading opportunities. It is revealed that although the model forecasts produce significantly higher returns than a passive benchmark, the model was unable to outperform the benchmark after allowing for transaction costs.