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Classical control methods are still in vogue because of their ability to guide us, rather intuitively, in achieving desired responses with appropriate tradeoffs. Nevertheless, there are some inherent limitations and difficulties. This article puts forward some of the questions that troubled us and proposes a new approach to the lead-lag compensation of single-input, single-output, linear time-invariant systems, the ones we were introduced to in our first course on control systems. The target specifications we have taken are meant for standard second-order systems. We show that both the transient and steady-state needs are met using the proposed nonconventional lag-lead compensator. The superiority of this new compensator model is reported in this article with some case studies as well as experimental results.

A nitrifying activated sludge process with ammonium feedback and inflow feedforward control is studied. The feedback and feedforward measurements are subject to time delay and the control loop includes a saturation. A Hammerstein-based model is therefore identified, including process delays and the nonlinearity. A Monod-type nonlinearity is used, as motivated by the oxygen injection efficiency reduction, with increasing dissolved oxygen concentration. The proposed feedback control strategy includes tuning of a linear lag compensator that has a limited low-frequency gain which allows global stability to be established with the Popov criterion. The feedforward controller attenuates the disturbance and provides an overall improvement of the control strategy. The performance of the combined feedback and feedforward aeration controller is evaluated with a benchmark model.

This study presents an inverter current sampled double-loop proportional multi-resonant (PMR)-based control technique for three-level (3L) three-phase four-leg (3P4L) advanced T-type neutral point clamped (AT-NPC) stand-alone mode inverter. Apart from the conventional linear controller the PMR controller has the ability to track a sinusoidal reference and does not require any axis transformation. Therefore, the main advantage of the proposed control technique for a 3P4L inverter is to independently control the output phase voltages when feeding a single phase and/or three phase loads. This is achieved by the inverter current sampled double-loop controller with a lead compensator in order to increase the control system phase margin unlike the capacitor current sampled controller. Thus, the harmonic compensation capability of the controller is increased which strengthens the controller against highly non-linear load types. The design procedures of the controller for the system are analytically explained. Then, the steady-state and dynamic performance of the controller is tested in a 3L 3P4L AT-NPC inverter system through many simulations and experimental studies. The results verify the fast-dynamic performance and the achievement of the low total harmonic distortion with a maximum of 2.89% for the 3L 3P4L AT-NPC inverter system even under serious non-linear load type. Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [215E357] This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under Project 215E357. WOS:000520421100025 2-s2.0-85082387573

In this paper, the systematic design procedure of the proposed lead-lag direct power model predictive controller (L2DP-MPC) for active-front-end (AFE) rectifier is presented. First, the parametric design procedure of the linear proportional-integrator (PI) and lead-lag controllers are described. Then, in the lead-lag control system, the inner-loop current controller is replaced by the non-linear DP-MPC controller to form the proposed L2DP-MPC. Moreover, a comparative study between four designed controllers including the PI, lead-lag, PI-DP-MPC, and the proposed L2DP-MPC is performed from various aspects. All of the controllers are applied to the three-level active-neutral-point-clamped (3L-ANPC) AFE rectifier to evaluate the performance of each controller. The presented simulation results verify the performance, feasibility, and superiority of the proposed L2DP-MPC over the PI, lead-lag, and PI-DP-MPC methods.

In this article, based on classical control theory, the design and implementation of a novel control strategy to reduce the effects of dead zone and friction in the design of position control systems for DC motors is presented. The classic linear controller, consisting of a dual integrator and a lead compensator, results in an easy to implement control system that also, through the classic gain margin and phase margin indicators, guarantees stability and robustness conditions. To test the validity of this strategy, it is implemented using the Quanser DC Motor Control Trainer system resulting in a system capable of reducing unwanted oscillations, stick/slip effect, without inducing chattering in the control variable.

In stand-alone or islanded DC microgrids, sharing of the load between parallel-connected converters is usually achieved using the droop control method. Two main types of droop control are used with DC microgrids: the impedance (V-I)droop control method and the admittance (I-V) droop control method. Droop control permits the sharing of load between parallel-connected converters, but it creates a voltage deviation in the DC microgrid voltage. Voltage restoration control is then required to restore the DC microgrid voltage back to its preset value. This paper proposes a novel I-V droop control method using a modified lag compensator which combines voltage control and load sharing between the parallel-connected converters within the DC microgrid. The proposed control system is made up of two nested controllers: an inner Proportional Integral (PI) current controller and an outer modified lag compensator which controls the voltage and the droop. An addition outer loop is used for voltage restoration. The proposed control system was simulated using Simulink. Simulation results are shown for the operation of two Buck converters connected in parallel and sharing a common resistive load.

Design methods for control systems based on plant models have been developed for many years. If a mathematical model is accurately obtained from the input-output relation of a plant, then the designed controller for the model performs well for the control system connected with the plant. However, the desired control performance might not be achieved when there is an undeniable modeling error. To overcome this problem, the authors proposed the model error compensator (MEC) to minimize the effect of the modeling error between the plant and the model. The MEC works well for many control systems, such as unstable systems and non-linear systems. However applying the MEC to non-minimum-phase plants is difficult because of their control system structures. Non-minimum-phase plants are well known for being difficult to control. This paper proposes an MEC with a parallel feed-forward filter (PFF). The PFF is used to cancel the non-minimum-phase characteristics of the plant. The effectiveness of the proposed method is illustrated through numerical examples.

In process control industries, one of the major and serious problems is presence of overshoot on controlled variables. This paper deals with the elimination overshoot in step response by using conventional PID controller with cascading of lead compensator. The proposed cascade technique consists of inner loop with lead compensators and outer loop with PID controller. The processes industry consists of many control loops and most of the control loops are consists of PI and PID controller. The PI/PID controller is used in the control loop with unstable system, the time response is oscillatory due to gain margin and phase margin. The proposed idea is to use the cascade control principle to control the unstable system with cascaded PID and Lead compensator. The compensator is used to compensate desired phase margin value of system and then make use of the PID controller is to control the system with robust, reduced order response, and thus, suppressing the overshoot in time response. The validity of the proposed approach is verified through simulation for the level control of unstable biochemical reactor.

This paper proposes a two-loop position/speed control system for linear DC motors. The control system is based on the parameterization of lead compensator using the genetic algorithm (GA) optimization method. A performance criterion including the information of overshoot, rise time, settling time, and steady-state error is proposed as the objective function. The linear DC motor is modeled using Simscape toolbox in MATLAB/Simulink platform. The simulation shows that the results successfully demonstrate the effectiveness and good dynamic performance of the proposed two-loop control system under specific constraints and various test conditions. In addition, the results show that the adopted method can perform an efficient search for the optimal parameters of the used controller.

Droop control is used to obtain load sharing between paralleled converters within a standalone/islanded DC microgrid. There are two main types of droop control methods used in DC microgrids; the impedance (V-I) droop and the admittance (I-V) droop. This paper presents an alternative droop control system built on the I-V droop method. The proposed alternative droop control system uses a modified Lag compensator to obtain voltage control, as well as load sharing between the paralleled converters within the DC microgrid. The control system consists of two nested controllers, an inner Proportional-Integral (PI) controller to control the current, and an outer modified Lag compensator to control the voltage and the droop. The proposed control system was modelled in Simulink, and the operation was tested by simulating two paralleled buck converters operated in the continuous current mode while sharing a common resistive load.

In this paper we introduce a novel benchmark problem to study the control of magnetic needle with two degrees of rotational freedom in a uniform magnetic field. Magnetic needle in an external magnetic field has stable and unstable equilibrium points, which depends on it's orientation. Our idea is to control the magnetic needle near it's unstable equilibrium point. Dynamics of the system is derived using Lagrangian energy based technique. The nonlinear system dynamics are linearized at unstable equilibrium point and the controllers are designed for this linear system, and the same controllers are applied to nonlinear system. The difference in tracking performance for linear and nonlinear system is observed using PD, PID, lead, lead lag compensators and state feedback, feed forward integral controller and H ∞ , quantitative feedback controllers. Further, control effort for all the above controllers are computed.

With the continuous expansion of wind farm clusters, the multi-terminal modular multilevel converter based high voltage direct current (MMC-HVDC) transmission has been employed for wind power delivery. To improve the control flexibility, dynamic voltage adjustment speed and rationality of power allocation, various coordination control methods have been recently investigated in multi-terminal MMC-HVDC transmission system. An attempt is made in this paper to contribute to the optimization of coordination control in the multi-terminal MMC-HVDC system connected to wind farms. Based on the analysis of DC voltage, power deviation and droop coefficient, an improved droop control strategy with adjustable coefficients is first proposed and thereby applied to multi-terminal MMC-HVDC transmission system with wind farm clusters. Arguably, the droop coefficient correction should be an effective method for optimizing power allocation and reducing DC voltage deviation between the receiving converters. In addition, a lag compensator is introduced to improve the response speed of the inner loop controller when the improved droop control is adopted. Furthermore, the influence of droop coefficients on the stability of the control system is discussed, and the dynamic response of the improved control system is also analyzed under the different droop and time coefficients, which can provide guidelines for the control optimization of multi-terminal MMC-HVDC system. Finally, a model of a five-terminal MMC-HVDC transmission system is built based on the RT-LAB simulator, and the simulation results show that the proposed method can not only optimize the voltage control and power allocation, but also improve the system response speed.

Over the last decade, numerous control schemes have been proposed by researchers for quasi Z source inverter (qZSI) to provide fast dynamic response and good transient performances. This paper proposed a novelty and an effective tuning method of dual-loop controller based on lead compensator and proportional (P) controller for single-phase qZSI to ensure reliable DC-link power regulation. Specifically, lead compensator and P controller act as voltage control and current control loop, respectively, to generate the desired shoot-through duty cycle feeding towards the unipolar carrier based pulse width modulation (CB-PWM). The lead compensator contributes to move the system poles from the left to the right half of the s-plane while the P controller damps any high frequency oscillation occurrence caused by the newly sited complex conjugate pole pair. To demonstrate the effectiveness and the feasibility of the proposed controller, the qZSI is utilized as a static synchronous compensator (STATCOM) system to provide reactive current compensation at the point of common coupling (PCC). All simulation models and results which documented in this paper are carried out using MATLAB/Simulink software.

The emergence of quasi Z source inverter (qZSI) in 2008 has grabbed researchers’ attention to explore new enhancement control schemes and modulation techniques in the past decade. This paper proposed a single-phase qZSI with lead compensator in the control system driven by unipolar carrier based pulse width modulation (CB-PWM) technique. Specifically, the lead compensator acts as qZSI’s outer voltage loop controller while the current inner control loop is attained via the conventional proportional (P) controller. When compared with traditional dual loop based proportional integral (PI)-P controller, the proposed controller demonstrates its superiority for the qZSI to achieve good dynamic, steady-state, and transient performances under both the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) operations. All design procedures are presented thoroughly in this paper and the effectiveness and theoretical analysis of the proposed approach are verified through simulation using MATLAB/Simulink software.

Lag-lead compensators are well known in automatic control engineering. They have 3 or 4 parameters to be adjusted (tuned) for proper operation depending on the compensator order. The frequency response of the control system or the root locus plot are traditionally used to tune the compensator in a lengthy procedure. A selected very slow second-order process has a time response to a unit step input of 150 seconds settling time is controlled using a first-order lag-lead compensator (through simulation). The lag-lead compensator is tuned by minimizing the sum of square of errors of the control system using MATLAB. Four functional constrains are used to control the performance of the lag-lead compensated control system. The result was reducing the settling time to only 0.666 seconds. The steady-state characteristics of closed-loop control system using the first-order lag-lead compensator were excellent. It was possible reduce the steady-state error to less than 0.01 using the tuned first-order lag-lead compensator.

This paper proposed a method of adaptive controller with a lead-lag parameters compensator and applied to a kind of aircraft boundary control system (ABCS). This method ensures optimization of fuzzy logic control function, and guarantees on-line adaptation of domain in aircraft boundary control system, which can make a great progress in dynamic characteristics and adaptabilities of flight control system. A proposed hybrid adaptation algorithm has been tested in the analogy flight practice speed control system of an induction motor drive. The digital simulation results demonstrated that it could improve transient properties in flight boundary control system, and provide well disturbance rejection in spite of its simplicity.

This work implements two feedback control systems to stabilize the angular position of the shaft of a torsional plant subjected to torsion. The first control system stabilizes such a position using an IO (Integer Order) compensator, while the second employs a FO (Fractional Order) one. The latter compensator uses the structure (the transfer function) of the former. That is, to obtain the FO compensator from the IO compensator, we need to make fractional all s operators of the transfer function representing the IO compensator. Therefore, we require to replace the Laplace operator s by sα, where α is a fractional number between 0 and 1. Experimental results obtained with the implementation of both feedback control systems demonstrated that the steady–state error, the settling time and the overshoot of the controlled output were reduced (improved) by the FO control system.

This paper compares lead compensation and droop control of a 10MW lithium-ion based battery energy storage system (BESS) designed to maintain load frequency control (LFC) by dispatching regulating reserves of active power to a 91MW test section of the Maui, Hawaii island grid model with wind generation of 30MW. The test section is part of an existing larger Maui grid model developed by General Electric in Siemen's Power System Simulator for Engineering, and the BESS model is based on Electric Power Research Institute's CBEST battery model. Performances of the two controllers are compared to minimize the deviations in grid frequency caused by wind power variations and loss of generation. The results show using the BESS to provide LFC via lead compensator caused a significant reduction in frequency volatility and the magnitude of the frequency deviations in comparison to a microgrid without a BESS and using the BESS to provide traditional droop control. The advantage of the LFC over Base Case (no BESS) and the Droop Control case (Case 2) is that is more effective at reducing the frequency deviation caused by a disturbance on the microgrid.

In this paper stability problem of double inverted pendulum controlled by a fractional differential compensator is investigated. Pendubot is an underactuated mechanical system, i.e. it has only one control input and two degrees of freedom. Detailed mathematical model of Pendubot is derived using the Rodriguez method and then fractional order lead compensator is introduced in order to stabilize it around unstable upright position. D-decomposition method is used to solve the problem of asymptotic stability of closed loop system. Stability regions in control parameters space are calculated using this technique, which allows tuning of the fractional differential compensator to be carried out.

In process control industries, one of the major and serious problems is presence of overshoot in controlled variables. This paper deals with elimination of overshoot In step response by using conventional PID controller with cascade lead compensator. In this cascade technique, lead compensator is used in the inner loop and PID controller connected in the outer loop. The process industry consists of many control loops and most of the control loops consists of PI and PID controller. The PI/PID controller is used in the control loop with third or higher order process. The time response is oscillatory due to gain margin and phase margin. The proposed idea is to use the cascade control principle to control the third order system with cascade PID controller and Lead compensator. The compensator is used to compensate the desired phase margin value of system and the PID controller is to control the system with reduced-order response and to suppressing the overshoot. The validity of the proposed approach is verified through simulation for the level control in three tank interacting system.

Recently, a variety of differential power-processing (DPP) architectures have been shown to improve the efficiency of photovoltaic (PV) systems. This paper proposes a simple control strategy for the isolated-port DPP architecture, and provides a comprehensive stability analysis for this system. The proposed controller drives the duty-cycle of the differential submodule integrated converters (subMICs) in proportion to a voltage difference between the submodule and the isolated-port. This method requires no additional sensing, complex processing, or communication between subMICs, and is therefore well suited for low-cost integrated hardware solutions. Stability of the resulting high-order nonlinear system is analyzed both in the time and frequency domains. A decoupled model is developed that reduces the high-order system dynamics to a 1-D control loop, which allows stable, well-behaved responses using a proportional or a lag compensator. Experimental results for a 72-cell PV module with three subMICs verify static and dynamic operation, and show that overall PV module efficiency exceeds 99% with no shading, and is higher than 96% under significant (50%) shading.

According to the characteristics of the internal model control and feed-forward control and Combining the both advantages, the compound control system of the internal model add feed-forward compensator was designed. In order to improve the dynamic performance of the control system, online identification method is adopted to establish the internal model. The designs of the internal model controller and feed-forward compensator were detailed instructions. The simulation shows that the compound control system have not only good dynamic performance, high tracking precision and strong anti-jamming capability, but also have the change of system parameters with strong robustness.

Control valve stiction is a common problem experienced by process control loops and is one of the main causes of loop cycling during a control session. This paper proposes a simple effective stickband compensator which was applied to a plant for reducing stickband and limit cycle amplitude within a unity feedback system. The technique is based on a 'stickband-jacket' applied across the input and the output of the actual control valve. The feedback error signal is used to vary the width of the stickband and limit cycle frequency. The compensator adds a single increment to the controller's degree-of-freedom and can be easily added to any existing control loop.

The robust control design method has been studied in recent decades. A control system works well under the modeling errors and disturbances if controller design is based on the robust control method. However, it is well known that in control systems, generally, there exists a trade-off between control performance and robustness. To overcome the trade-off problem, this paper proposes an internal model type compensator structure that minimizes the modeling gap between the nominal model and actual plant dynamics. By using the proposed compensator, the dynamics of the compensated system closes to that of the nominal model. Then, a design method of the compensator parameters is also proposed for minimizing a set of plant dynamics. The proposed design method is reduced to the standard µ design control problem. If we use the proposed compensator for control systems instead of the plant itself, the output performance might be better despite plant uncertainty. Given that the proposed compensator can be used for the control of not only linear but also nonlinear plants, we can easily achieve robust control of nonlinear systems. The effectiveness of the proposed method is shown by numerical examples.

This paper discusses the application of a lead compensator with complex pole and complex zero for a missile. It is compared with a lead compensator with real pole and real zero. A typical laser guided missile control system is considered for the performance comparison of both the compensators. Simulation studies carried out with MATLAB brings out the scope of using complex compensator in missile guided systems.

The purpose of this study is to achieve high-precision and high-bandwidth reference tracking control for an electric hydrostatic actuator (EHA). First, the pole placement method and the zero placement method were used to design a reference input tracking controller consisting of a PI-D controller and a feed-forward controller for the EHA-driven system. The feed-forward controller exhibited a high gain symptom in the frequency response as the actuation frequency of the system increased. An input shaping filter (ISF) with the style of a lag compensator was incorporated into the control system to suppress the increase in the control gain in the high-frequency range. The effectiveness of the proposed control system was evaluated by conducting experiments. The results indicate that the application of the proposed control system, including the ISF, can greatly improve the reference tracking control performance of the EHA-driven system. In addition, the proposed control system using the ISF is stable with a sufficient margin for a broad frequency range.

In this paper, a simple approach for the lead-lag compensator design based on vector margin and steady-state error of the step response of the overall control system is proposed. The main reason for including the vector margin in compensator design is to take the stability robustness of the overall system into consideration. A simple performance index is defined for the given control system in terms of the vector margin and the percentage steady-state error of the step response. The particle swarm optimization (PSO) is used to evolve the candidate design parameters of the compensators in order to find the best set of design parameters. Three numerical examples are provided to illustrate the use and the effectiveness of the proposed method.

Vibration control of a two-mass resonant system such as a rolling machine is an important problem in industrial applications, because vibration causes a decrease in task accuracy and the destruction of materials. Taking this into the accounts, state feedback control, H∞ control, and resonant ratio control based on a lumped parameter system have been researched for the vibration suppression of a system with a flexible mechanism. On the other hand, methods in distributed parameter model need a lot of calculation in time domain design.In this paper, by considering the distributed parameter system in the Laplace domain, a compensator based on a wave equation is proposed. In addition, a two-mass resonant system is controlled using the proposed compensator. The proposed control system with the wave compensator has a simple structure. Therefore, it is easy to set the control parameters in the proposed control system. The effectiveness of the proposed method is verified by experimental results for a two-mass resonant system.

It is well known that the communication delay due to the phasor measurement in wide area monitoring system (WAMS) as well as various system operating conditions such as heavy line flows and unpredictable network structures, may deteriorate the wide-area stabilizing control effect. To overcome this problem, the inverse input and output multiplicative model is proposed to represent unstructured uncertainties due to system operations and communication delay in the robust centralized damping controller design of superconducting magnetic energy storage (SMES) based on WAMS. The structure of centralized controller for SMES is the practical 1st-order lead/lag compensator. To automatically tune the control parameters, the optimization problem based on the enhancement of damping performance and system robust stability margin is achieved by particle swarm optimization. Simulation studies in the West Japan six-area interconnected system confirm that the proposed robust SMES centralized controller is superior to the conventional SMES centralized controller in terms of damping performance and robustness against system and time delay uncertainties.

This paper is concerned with the active isolation of a system containing a distributed parameter isolator using absolute velocity feedback control. The main differences between this type of system and one with a massless isolator, is that there are isolator resonances. It is shown that the vibration at these resonance frequencies cannot be suppressed using a simple velocity feedback control strategy. Moreover, it is found that the isolator resonances can cause the control system to become unstable, if the isolated equipment is supported on a flexible base. A stability criterion based on the mode shapes of the system is presented. Two techniques to stabilise the system are investigated and compared. The first involves the addition of mass on the base structure, and the second involves an electronic lead compensator. Experimental results are presented to support the theoretical findings. It is shown that even if the instability due to the isolator resonances and flexibility of the base can be prevented, the instability due to the flexibility of the equipment remains a problem.

This paper proposes a robust power controller design of superconducting magnetic energy storage (SMES) based on wide area synchronized phasor measurement units (PMUs) for stabilization of inter-area oscillation. The structure of active and reactive power controllers of SMES is the first-order lead/lag compensator. Assuming multiple PMUs are located in an interconnected power system, the steady state phasor data are obtained by applying the small load perturbation. Using the phasor data, the simplified oscillation model (SOM) included with SMES power controllers can be identified and applied to estimate the dominant inter-area oscillation modes. In the robust control design, unstructured system uncertainties such as various operating conditions, system parameters variation, etc., are represented by the inverse additive perturbation and included in the SOM. To enhance the system robust stability margin, the optimization of SMES control parameters is solved by genetic algorithm in the SOM. Simulation studies in the West Japan 6-machine power system confirm that the robustness of the proposed SMES is much superior to the conventional SMES against various operating conditions and fault locations.

The intrinsic transient performance capability and limitation of integrated solid oxide fuel cell (SOFC) systems is evaluated based on the system balance-of-plant response and fuel cell operating requirements (i.e., allowable deviation from nominal operation). Specifically, non-dimensional relations are derived from conservation principles that quantify the maximum instantaneous current increase that a solid oxide fuel cell system can safely manage based on (1) the desired fuel cell operating point, (2) the maximum allowable fuel utilization, (3) the maximum average fuel cell temperature deviation, (4) the response delay and (5) the operating requirements of the system balance-of-plant components. New non-dimensional numbers representing the ratio of species or thermal convection to volumetric capacitance in the fuel cell during balance-of-plant delay have been developed. The analyses indicate: (1) SOFC intrinsic transient performance is largely limited by fuel processor flow delays that can cause fuel depletion in the anode compartment and (2) that with proper system actuators and control design transient operation of SOFC systems should be possible while maintaining SOFC average temperature within a degree. The SOFC system fuel processor lag appears to be the cause of SOFC load following limitation, while lag in air handling appears to be manageable. To demonstrate methods to avoid fuel depletion limitation a fuel flow lead compensator is developed. Integrated system simulations with proper control demonstrate significant SOFC transient performance within fuel cell operating requirements. © 2008 Elsevier B.V. All rights reserved.

Lead/Lag controllers are used extensively in industry and there is no straight forward and general solution to the problem of calculating all stabilizing parameters of Lead/Lag controllers. In this paper, a linear programming approach is proposed to calculate all stabilizing parameters of Lead/Lag type controllers for a given continuous-time plant from an arbitrary order. The proposed method is based on the extension of Hermite-Biehler Theorem, which has been proposed for calculating all stabilizing PID gains for a given continues-time system in [6]. The linear programming nature of the proposed approach is its main advantage, which leads to the computer-aided computation of the above problem. The applicability of the method is verified through a numerical example.

A frequency-shaped high-gain (FSHG) compensator is proposed and implemented for optical disk drive control systems, such as CD or DVD servo systems. The FSHG compensator is obtained by modifying an error-based disturbance observer. The FSHG compensator can be easily realised as a form of a low cost analogue circuit. The disturbance rejection performance can also be easily improved by filter parameters in the FSHG compensator. Design guidelines for the filter parameters (numerator order and filter time constant) are also suggested in this paper. Finally, the effectiveness of the FSHG compensator is shown through experimental results showing disturbance rejection performance evaluated under forced disturbances.

Shallow slurry injection is considered to be the most efficient way to reduce the ammonia emission by agriculture, but its performance is highly dependent on the injection depth. An automatic electro-hydraulic depth control system was developed to maintain the injection depth within narrow margins around the desired value. It utilised the hydraulic system of the four-point linkage of the slurry tanker to change the position of the injector with respect to the tanker in order to minimise the difference between the desired height of the supporting frame of the injector and the height measured by means of an ultrasonic sensor. Based on a grey-box model, the performance of different control algorithms was compared by simulation with this model. Although the bandwidth of the system with a lead compensator was slightly larger than with a proportional controller for a linearised model structure, the performance of both controllers was comparable when actuator saturation was taken into account. Because of its simplicity, the proportional controller was implemented. Comparison of the performance of the depth control system with the commercially available pressure control system on two fields with a high and a low soil penetration resistance showed that the depth control system outperforms the pressure control system in terms of overall mean error (51–78% more accurate) and standard deviation (16–44% less variation) for all parallel runs.

To achieve high-speed and high-precision position control for semiconductor product machines and industrial robots, the full-closed feedback control is applied. Many control methods have been proposed for such a system. In general, P,PI/I-PI control which is one of PID control is applied to a lot of industrial applications. However, in case of changing mechanical characters of control target, the parameters of P,PI/I-PI control have to be changed for keeping a good motion performance. In this paper, we propose a new P,PI/I-P control method which is with nonlinear compensator. The algorithm of nonlinear compensator is based on sliding mode control with chattering compensation. The effectiveness of proposed control method is evaluated by using full-closed single axis slider system via point to point control and contour control in the case of changing load. From the experimental results, the proposed control method has robustness in the case of changing acceleration/deceleration of control reference, changing load and low velocity contouring motion.

Capability and meanwhile simplicity have stupendously expanded the area of application of linear controllers in the industrial activities, particularly the control of robotic arms, and other devices. The ultimate goal to accomplish this project is to show this capability in the frame of movement control of the arm of a quality control unit (side device), which forms a part of an automatic cell together with an indexing table. The fact that the existence of the gearbox, dramatically decreases the effects of non-linear dynamic of the arm to linear dynamic of the DC motor, justifies the idea of designation and implementation a linear controller like Lead-Lag to control the said arm. Of course, we need to apply some other equipment like DC motor torque control system, sensors, and related interface circuits. In this article, it will be observed that how the above goal will be accomplished by linear identification of the system with the method of step response identification and then digital implementation of the said controller in computer and application of the arm motor torque control.

A control algorithm for a hybrid compensator based on a concept of running complex RMS values of the fundamental harmonic of voltages and currents is presented in the paper. The hybrid compensator is composed of an adaptive passive balancing compensator, controlled in the frequency-domain, and a current source, controlled in the time-domain. The algorithm used for the compensator control is rooted in a new approach to the power theory of electrical systems with quasi-periodic waveforms. It is based on the concept of running quantities and a forward extrapolation of the power properties of a time-variant load. Experimental results obtained using such an algorithm for controlling a laboratory prototype of the hybrid compensator are presented in the paper.

To measure the soil compaction online by measuring the draught on a cutting tool or subsoiler, the moisture content should be known and the cutting depth should remain constant. In this paper the depth controller of a subsoiler is designed. The three-point hitch is used as a correction mechanism to adjust the cutting depth by utilising the signal output of a depth sensor, which consisted of a swinging arm metal wheel and a linear variable displacement transducer (LVDT). An extra control loop is constructed around the existing position control loop of the three-point hitch. Based on a semi-analytical model multiplied by a conversion factor, a proportional (P) controller, a lead compensator, a proportional integrative derivative (PID) controller and a PID controller with filtered derivative (D), actions are designed. All controllers provided satisfactory results, with the latter showing the best performance in practice. It could also be demonstrated that, with the hardware used, no further improvement can be achieved by increasing the complexity of the controller.

This paper presents a high precision positioning mechanism design with dual actuator. In the fields of micro positioning, micromanipulation and micro test instrument, the required motion precision is continuously increasing. Dual servo system consisting of a coarse stage and a fine motion stage with VCM and PZT is proposed. Mechanical mechanism is designed with the leaf spring type of a flexure hinge joint. Lead compensator is applied to this control system, and is designed by PQ method.

This paper describes the design, modelling, fabrication and control of an attraction type electromagnetic levitation prototype with single-axis control. The system is simulated using standard FEM packages and used in control system related investigations. The mathematical model of the system has also been derived. Experiments have also been carried out. Practically evaluated system parameters show excellent agreement with the values estimated using FEM calculations. Two stabilising controllers, an inner current controller (P controller) and an outer position controller (lead compensator) have been designed for this system and also implemented on the practical setup.

A new systematic procedure for synthesis of nonlinear lead-lag controllers for highly nonlinear unstable plants is developed. The procedure is to stabilize the unstable plant followed by generation of sinusoidal-input describing function (SIDF) models at various operating regimes of interest. The unstable plant frequency domain behavior is extracted, and a set of linear lead-lag controllers are designed that would force the open-loop behavior of the system (comprised of the lead-lag controller and the nonlinear plant) and mimic that of desired. Finally, a describing function inversion is used, and the nonlinear functions describing the values of the lead-lag coefficients as a function of the error signal are obtained. Experimental results are presented for verification, and bounded-input bounded-output stability is demonstrated by successful generation of the describing function models of the closed-loop system comprised of the synthesized nonlinear lead-lag controller and the nonlinear plant.

Controlling the solar panels to extract maximum solar energy is an important concern of control engineers these days. An approximate second order model of a sun seeker control system is controlled using lead, lag, and lead-lag controller. The response of these controllers is compared with the proposed robust controller. Subsequently it is observed that the robust controller outperforms in providing reliability and stability in case of parameter variations under practical circumstances. The results are simulated in MATLAB.

A SISO control system is built by using a volume displacement sensor and a set of actuators driven in parallel with a single amplifier. The actuators location is optimized to achieve an open-loop transfer function which exhibits alternating poles and zeros, as for systems with collocated actuators and sensors; the search procedure uses a genetic algorithm. The ability of a simple lead compensator to control this SISO system is numerically demonstrated.

The development of a static, synchronous, reactive-power compensator based on a semiconductor voltage converter is considered. Power components and the design of the control system are also presented.

A universal design chart for lag-lead compensators is given. This chart allows compensators to be designed without trial-and-error while meeting four specifications: steady-state error; phase margin; gain margin; and gain (or phase) crossover frequency.

This paper investigates the control of a linear ball-screw stage driving a two-mass load. Due to the high speed-reduction ratio, the angular displacement of the driving motor is insensitive to the flexible oscillations. The bandwidth of the closed-loop system is thus constrained by the light damping of the flexible load. As a remedy, an accelerometer is installed on the flexible load. A lead compensator based on acceleration and angular displacement feedback is devised via root-locus analysis. Performance of the control system is illustrated with numerical simulations and confirmed by experimental results.

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.

In Network control system, the random Network time-delay exists in the forward path and feedback path, which will affect the stability of control system. To eliminate the influence of time-delay, the compensator is installed in Network control system. But the form of compensator in Network control system is alterable, different form for compensator will affect the characteristic of control system in deeply. In the paper, we study the different form for compensators how to affect the characteristic of Network control system, and design an appropriate form of compensator. It also can be proved by theory and experiment that the compensator can avoid the problems of model error and needn't to prediction of the Network time-delay. The compensator can also be used for Network control system of UDP or TCP transport protocols.

This paper describes a control method to widen the frequency bandwidth of a voltage control system for a switching regulator, which is based on a coprime factorization description of the system. First, this paper clarifies the control performance of a conventional voltage control method with a proportional-integral control element and a phase lead element, which does not widen the frequency bandwidth enough. Next, a new voltage control method with a compensator based on the coprime factorization description of the system is proposed. The compensator employs a two-degrees-of-freedom control system, and is made up of a stabilizing dynamic compensator and a reference signal response dynamic compensator. Furthermore, one possible design of the two dynamic compensators, and the simulation and experimental results for the test switching regulator are presented.