Showing papers on "Bang–bang control published in 2012"

FLC-Based DTC Scheme to Improve the Dynamic Performance of an IM Drive

Abstract: This paper presents a fuzzy logic hysteresis comparator-based direct torque control (DTC) scheme of an induction motor (IM) under varying dynamic conditions. The fuzzy logic controller (FLC) is used to adjust the bandwidth of the torque hysteresis controller in order to reduce the torque and flux ripples and, hence, to improve motor dynamic response. The effects of torque hysteresis bandwidth on the amplitude of torque ripples of an IM are also discussed in this paper. Based on the slopes of motor-estimated torque and stator current, an FLC is designed to select the optimum bandwidth of the torque hysteresis controller. This paper also proposes a simpler algorithm than the conventional trigonometric function-based algorithm to evaluate the sector number (required for DTC scheme) of the stator flux-linkage space vector. The proposed algorithm reduces the computational burden on the microprocessor. In order to test the performance of the proposed FLC-based DTC scheme for IM drive, a complete simulation model is developed using MATLAB/Simulink. The proposed FLC-based DTC scheme is also implemented in real time using DSP board DS1104 for a prototype 1/3 hp motor. The performance of the proposed drive is tested in both simulation and experiment.

A Wide-Speed High Torque Capability Utilizing Overmodulation Strategy in DTC of Induction Machines With Constant Switching Frequency Controller

Abstract: This paper presents a simple overmodulation method employed in direct torque control (DTC) constant switching frequency (CSF) controller of induction machines. The proposed overmodulation method is utilized to extend a constant torque region and hence produce high torque capability in field-weakening region with six-step operation. It will be shown that the overmodulation operation using the DTC-CSF scheme can be established by controlling the stator flux locus from circular to the hexagonal shape. This is achieved by modifying the flux error status produced from the flux hysteresis controller before it is fed to the lookup table. The main benefit of the proposed method is its simplicity since it requires only a minor modification to the conventional DTC hysteresis-based structure and does not require a space-vector modulator.

Online Computation of Hysteresis Boundary for Constant Switching Frequency Current-Error Space-Vector-Based Hysteresis Controller for VSI-Fed IM Drives

Abstract: This paper proposes a current-error space-vector-based hysteresis controller with online computation of boundary for two-level inverter-fed induction motor (IM) drives. The proposed hysteresis controller has got all advantages of conventional current-error space-vector-based hysteresis controllers like quick transient response, simplicity, adjacent voltage vector switching, etc. Major advantage of the proposed controller-based voltage-source-inverters-fed drive is that phase voltage frequency spectrum produced is exactly similar to that of a constant switching frequency space-vector pulsewidth modulated (SVPWM) inverter. In this proposed hysteresis controller, stator voltages along α- and β-axes are estimated during zero and active voltage vector periods using current errors along α- and β-axes and steady-state model of IM. Online computation of hysteresis boundary is carried out using estimated stator voltages in the proposed hysteresis controller. The proposed scheme is simple and capable of taking inverter upto six-step-mode operation, if demanded by drive system. The proposed hysteresis-controller-based inverter-fed drive scheme is experimentally verified. The steady state and transient performance of the proposed scheme is extensively tested. The experimental results are giving constant frequency spectrum for phase voltage similar to that of constant frequency SVPWM inverter-fed drive.

New Sensorless Rotor Position Estimator of a DFIG Based on Torque Calculations—Stability Study

Abstract: This paper presents a new sensorless method and its stability study for the estimation of the mechanical rotor position of the wound-rotor induction machine. The main purpose of this study is to implement the control of the doubly fed induction generator (DFIG). The method is based on the model reference adaptive system and uses the electromagnetic torque as the working error variable. The method does not need any information about the stator or rotor fluxes, and so, it is only indirectly dependent of the flux dynamics. As other methods proposed recently, this can also be implemented in the rotor or in the stator reference frames and with hysteresis or with proportional-integral controllers. The stability analysis gives an instability region on the rotor current dq plane described by a circle whose diameter is the no-load stator current. The method is robust to parameter variations depending only weakly on a single parameter. Simulation and experimental results show that the method is appropriate for the vector control of the DFIG although needing an additional approach to stabilize the system in the instability region.

A Fast-Response Pseudo-PWM Buck Converter With PLL-Based Hysteresis Control

Abstract: Hysteresis voltage-mode control is a simple and fast control scheme for switched-mode power converters. However, it is well-known that the switching frequency of a switched-mode power converter with hysteresis control depends on many factors such as loading current and delay of the controller which vary from time to time. It results in a wide noise spectrum and leads to difficulty in shielding electro-magnetic interference. In this work, a phase-lock loop (PLL) is utilized to control the hysteresis level of the comparator used in the controller, while not interfering with the intrinsic behavior of the hysteresis controller. Some design techniques are used to solve the integration problem and to improve the settling speed of the PLL. Moreover, different control modes are implemented. A buck converter with proposed control scheme is fabricated using a commercial 0.35-μ m CMOS technology. The chip area is 1900 μm × 2200 μm. The switching frequency is locked to 1 MHz, and the measured frequency deviation is within ±1%. The measured load transient response between 160 and 360 mA is 5 μ s only.

Erratum to “PI and fuzzy logic controllers for shunt active power filter—A report” [Isa Transactions 51, 163–169]

Abstract: The authors acknowledge certain errors in their recently published paper titled “PI and fuzzy logic controllers for shunt active power filter—A report. The ambiguity in bandwidth calculation of adaptive hysteresis controller and control aspects of dc-link voltage issues are addressed. The shunt APF system is validated through extensive simulation and the results are support features of the proposed technique.

Uncertain bang-bang control for continuous time model

Abstract: By using the equation of optimality in uncertain optimal control, an uncertain bang-bang control problem for a continuous time model is investigated. An example is given to illustrate the result obtained.

Near-Null Response to Large-Signal Transients in an Augmented Buck Converter: A Geometric Approach

Abstract: The maximum closed-loop bandwidth of a dc-dc converter is restricted to a fraction of its switching frequency when governed by a conventional average-based pulsewidth modulation (PWM) controller. Even an advanced geometric control is limited by internal slew rates. The bandwidth can reach or exceed the switching frequency through converter augmentation; however, this requires a nonlinear control algorithm and circuit arrangements. This paper considers methods of augmentation and control for a fast buck converter. Conditions for time-optimal transient recovery are obtained for both instantaneous and delayed transient disturbance detection. Design tradeoffs and control issues related to augmentation are considered here. The main switch is controlled using a fixed frequency PWM current-mode control with load current feedforward, and augmented switches are controlled using frequency-limited bang-bang control based on a geometric approach. A small-signal model is obtained and extended control bandwidth is demonstrated. Fast transient recovery is achieved for both single- and two-resistance augmentation. A prototype augmented buck converter is tested. Output voltage and inductor current overshoot and undershoot can be lowered more than with previous methods. It is possible to achieve near-null response in the sense of ripple band to a large-signal transient.

Current controlled voltage source inverter using Hysteresis controller and PI controller

Abstract: Current-controlled pulse width modulated (PWM) voltage source inverters are most widely used in high performance AC drive systems, as they provide high dynamic response. A comparative study between the Hysteresis controller and Proportional-Integral controller using PWM techniques for three-phase voltage source inverter was done. The comparison was done in terms of total harmonic distortion (THD) level at the three phase load current. Simulation was done with the help of Matlab-Simulink environment. The hysteresis controller provides gooddynamic performance, whereas the Proportional-Integral controller provides instantaneous current control and waveshaping, fixed inverter switching frequency resulting in better harmonics.

An optimizing start-up strategy for a bio-methanator

Abstract: This paper presents an optimizing start-up strategy for a bio-methanator. The goal of the control strategy is to maximize the outflow rate of methane in anaerobic digestion processes, which can be described by a two-population model. The methodology relies on a thorough analysis of the system dynamics and involves the solution of two optimization problems: steady-state optimization for determining the optimal operating point and transient optimization. The latter is a classical optimal control problem, which can be solved using the maximum principle of Pontryagin. The proposed control law is of the bang–bang type. The process is driven from an initial state to a small neighborhood of the optimal steady state by switching the manipulated variable (dilution rate) from the minimum to the maximum value at a certain time instant. Then the dilution rate is set to the optimal value and the system settles down in the optimal steady state. This control law ensures the convergence of the system to the optimal steady state and substantially increases its stability region. The region of attraction of the steady state corresponding to maximum production of methane is considerably enlarged. In some cases, which are related to the possibility of selecting the minimum dilution rate below a certain level, the stability region of the optimal steady state equals the interior of the state space. Aside its efficiency, which is evaluated not only in terms of biogas production but also from the perspective of treatment of the organic load, the strategy is also characterized by simplicity, being thus appropriate for implementation in real-life systems. Another important advantage is its generality: this technique may be applied to any anaerobic digestion process, for which the acidogenesis and methanogenesis are, respectively, characterized by Monod and Haldane kinetics.

Comparison of hysteresis control and reduced order linear quadratic regulator control for power factor correction using dc–dc cuk converters

Abstract: This paper focuses on a comparative study of a reduced order linear quadratic regulator control (ROLQR) and conventional variable frequency hysteresis controller (HC) for power factor correction, and their performances are compared A prototype of front-end AC–DC converter followed by DC–DC Cuk converter controlled by a dSPACE signal processor was set up for 60 watts Experimental results are presented to validate the simulation results Simulation and experimental results reveal that ROLQR control can achieve good output voltage regulation and also provide improved robustness in shaping the input current in the presence of load variations when compared to conventional HC

Regenerative Power-Optimal Reaction Wheel Attitude Control

Abstract: This paper develops an analytical instantaneous power-optimal attitude control for a spacecraft using an integrated reaction wheel–flywheel system allowing for energy storage and return. The control is formulated in a general manner to use an arbitrarily large number of reaction wheels. It is applicable to systems with redundant wheels spanning three-dimensional space, which are controlled by a general attitude control law. The instantaneous power usage is minimized by modifying the wheel control torques using the wheel torque null motion. In this study, reducing the wheel speed results in negative power usage with perfect energy recuperation. Applying the maximum available wheel torque constraints, the null torque solution space is reduced to a hyperdimensional vector geometry problem, and the power-optimal wheel control torques are uniquely determined. The control modifications are applied to both attitude regulation and tracking control laws, demonstrating its performance for a variety of initial spacecraft states. Not only does the new control maximize the energy extraction from the reaction wheels, it also maintains the smallest flywheel spin rates, which helps reduce the maneuver-wide power usage.

Synthesis of Optimal Bang–Bang Control for Cooperative Collision Avoidance for Aircraft (Ships) with Unequal Linear Speeds

Abstract: Close proximity encounters most often occur for situations in which participants have unequal linear speeds. Cooperative collision avoidance strategies for such situations are investigated. We show that, unlike the encounters of participants with equal linear speeds, bang–bang collision avoidance strategies are not always optimal when the linear speeds are unequal, and we establish the conditions for which no optimal bang–bang controls exist near the terminal time. Nevertheless, under certain conditions, we demonstrate that bang–bang collision avoidance strategies remain optimal for encounters of participants with unequal linear speeds. Such conditions are established, and it appears that they cover a wide range of important practical situations. The synthesis of bang–bang control is constructed, and its optimality is established.

Novel hysteresis controller based on a rotating coordinate system with direct d and q constraint

Abstract: With increasing decentralized power supply within the grids and a constantly growing number of active front end inverters (AFE) being connected to the grid there is a high demand on reactive power feeding to the grid. Actual Control processes, especially hysteresis controller, do not allow a direct active and reactive control without special transformations [1].

Self-tuning fuzzy logic control of a switched reluctance generator for wind energy applications

Abstract: This paper presents a new self-tuning fuzzy logic control (FLC) based speed controller of a switched reluctance generator (SRG) for wind power applications. Due to its doubly salient structure and magnetic saturation, the SRG possesses an inherent characteristic of strong nonlinearity. In addition, its flux linkage, inductance, and torque are highly coupled with the rotor position and phase current. All these features make the application of traditional controllers to the SRG difficult and unsatisfactory. The proposed controller consists of three main parts: turn-on and turn-off angle determination, self-tuning FLC for speed control, and a current controller. The turn-on and turn-off angle determination, as its name implies, controls the turn-on and turn-off angles of power switches to improve the efficiency and torque regulation of the SRG. The self-tuning FLC is the speed controller which has better adaptability than a traditional controller so that it provides better performance over a wide range of operating conditions. The current controller is basically a hysteresis controller which controls the phase current in accordance with the turn-on and turn-off angles. Simulation results are shown to verify the effectiveness of the proposed controller.

Optimization method for solving bang-bang and singular control problems

Abstract: In this paper we study optimal control problems with the control variable appearing linearly. A novel method for optimization with respect to the switching times of controls containing both bang-bang and singular arcs is presented. This method transforms the control problem into a finite-dimensional optimization problem by reformulating the control problem as a multi-stage optimization problem. The optimal control problem is partitioned as several stages, with each stage corresponding to a particular control arc. A control vector parameterization approach is applied to convert the control problem to a static nonlinear programming (NLP) problem. The control profiles and stage lengths act as decision variables. Based on the Pontryagin maximal principle, a multi-stage adjoint system is constructed to calculate the gradients required by the NLP solvers. Two examples are studied to demonstrate the effectiveness of this strategy.

Three-level hysteresis current control for a three-phase permanent magnet synchronous motor drive

Abstract: This paper presents a novel three-level hysteresis current control scheme for a three-phase permanent magnet synchronous motor (PMSM) fed by two single-phase four-switch voltage source inverters. Based on two-level hysteresis current control techniques for a single-phase four-switch inverter, a novel three-level PWM method for three-phase PMSM motor is implemented to reduce the magnitude and variation of the switching frequency. To obtain better harmonic performance, an improved variable band hysteresis method for three-level three-phase voltage source inverter is further proposed. Considering three states of output average voltage of the inverter, a new hysteresis controller with variable band calculated by the motor resistance, inductance, DC-link voltage, phase current and back-emf is designed to maintain constant phase leg switching frequencies. The proposed method is simple and effective, and verified by the simulation.

Optimal active control of a wave energy converter

Abstract: This paper investigates optimal active control schemes applied to a point absorber wave energy converter within a receding horizon fashion. A variational formulation of the power maximization problem is adapted to solve the optimal control problem. The optimal control method is shown to be of a bang-bang type for a power take-off mechanism that incorporates both linear dampers and active control elements. We also consider a direct transcription of the optimal control problem as a general nonlinear program. A variation of the projected gradient optimization scheme is formulated and shown to be feasible and computationally inexpensive compared to a standard NLP solver. Since the system model is bilinear and the cost function is non-convex quadratic, the resulting optimization problem is not a convex quadratic program. Results will be compared with an optimal command latching method to demonstrate the improvement in absorbed power. Time domain simulations are generated under irregular sea conditions.

Switching surfaces and null-controllable region of a class of LTI systems using Gröbner basis

Abstract: The problem of time optimal feedback control of a single input, continuous time, linear time invariant (LTI) system is considered. The control input is constrained to obey |u(t)| ≤ 1. It is known that the solution to this problem is bang-bang with the input switching between the extreme values ±1 according to some “switching surfaces” in the state space. It is shown that for a class of LTI systems, these switching surfaces can be represented as semi-algebraic sets and a method to construct these switching surfaces using Grobner basis, is proposed. Numerical simulations demonstrate the effectiveness of this feedback control strategy.

Analysis of Closed Loop Chopper Controlled Drive for PMDC Motors using PID Controller

Abstract: In orthopedic surgical simulators PMDC motors are used. A closed loop chopper controlled scheme employing PID controller is attempted in this paper, which employs two power electronic switches one for ON/OFF control and the other for speed control. The ON/OFF Control loop uses a hysteresis controller and a PID controller is used for effective speed control of the motor. The closed loop system is simulated using Matlab/Simulink. The responses of both the loops were analysed. The simulation results infer that this scheme can give efficient control of the motor.

Improved Hysteresis Current Controller to Drive Permanent Magnet Synchronous Motors through the Field Oriented Control

Abstract: Hysteresis current controller is used in many industrial applications because it has many advantages as fast, high dynamic performance and doesn't require any information about load parameters. The draw back of this current controller is varying switching frequency. This paper presents adaptive hysteresis current controller to control the inverter. It is used to reduce the ripple, total harmonic distortion and improvement the switching frequency through design of PI current controller. The performance of the drive system due to improvement in the hysteresis current controller is simulated through the matlab simulink. The modified hysteresis current controller is compared to conventional hysteresis controller under steady state and transient conditions with fixed load, sudden applied and sudden removal load and reversing load to show the effectiveness of this modification.

Modeling and control for variable-pump controlling variable-motor

Abstract: The variable-pump controlling variable-motor(VPCVM) is an essential nonlinear system with dual-input,single-output and coupling,for which regular control algorithms are ineffective to achieve the required control perfor-mances.Based on linearization theory for VPCVM,we propose an improved Bang-Bang control algorithm for tackling the nonlinearity and the unsolvable coupling.First we develop a mathematical model of VPCVM involving the multipli-cation nonlinearity with the output variable;and then,we linearize the model by using the feedback linearization theory.Based on the linearized model,we develop the improved Bang-Bang control algorithm to achieve the rapid control for VPCVM.Simulation results demonstrate that the proposed algorithm realizes the desired rapid control on VPCVM with performances higher than that of conventional control methods.Furthermore,this algorithm exhibits a strong robustness against the variations of rotational speed and load.

Power Closed-loop Control of Switched Reluctance Generator for High Efficiency Operation

Abstract: This paper describes a control method of turn-on/off angles to improve the efficiency of the switched reluctance generator(SRG) with a power closed-loop control system, and the inner-loop of the system is current hysteresis control. The SRG control system is constituted by the PI power controller and the two-level current hysteresis controller. By measuring and analyzing the system losses of different reference powers, speeds and turn-on/off angles, selection strategy of optimal turn-on/off angles is discussed. The proposed method is simple, reliable, and easy to achieve.

The effectiveness of fuzzy logic control for pv pumping system

Abstract: This paper presents an optimal operation of a photovoltaic pumping system. An analysis by witch the dynamic performances of a permanent magnet brushless DC (PMBLDC) motor is controlled through a hysteresis current loop and an outer speed loop with different controllers. The dynamics of the drive system with (PI) and a Fuzzy logic (FL) speed controllers are presented. In order to optimize the overall system efficiency, a maximum power point tracker is also used. Simulation is carried out by formatting the mathematical model for photovoltaic source, MPPT, motor and pump load. The results with FL speed controller show improvement in transient response of PMBLDC drive over conventional PI. The effectiveness of the FL controller is also demonstrated.

6-Periodic travelling waves in an artificial neural network with bang–bang control

Abstract: Doubly periodic travelling waves can be used to describe dynamic patterns of signals that govern movements of animals. In this paper, we study the existence of such waves in cellular networks involving the discontinuous Heaviside step function. This is done by finding ω-periodic solutions of an accompanying recurrence relation with a priori unknown parameters and the Heaviside function. Since analytic tools cannot be used to handle discontinuous models such as ours, existence of periodic solutions is investigated by means of symmetry, combinatorial techniques and accompanying linear systems. By such means, we are able to obtain all periodic solutions with least periods 1 through 6. Our techniques are new and good for other periodic solutions with relatively small periods.

Simultaneous Optimal Design of the Lyapunov-Based Semi-Active Control and the Semi-Active Vibration Control Device: Inverse Lyapunov Approach

Abstract: We address a simultaneous optimal design problem of a semi-active (SA) control law and design parameters in a semi-active control device for civil structures. The vibration control device (VCD) that is being developed by authors is used as the semi-active control device. The VCD is composed of a ball screw with a flywheel for the inertial resistance force and an electric motor with an electric circuit for the damping resistance force. A new bang–bang type semi-active control law referred to as inverse Lyapunov approach is proposed. In the inverse Lyapunov approach, the Lyapunov matrix in the bang–bang type semi-active control based on the Lyapunov function is searched so that the control performance of the semi-active control system is optimized. Design parameters to determine the Lyapunov function and those of the VCD are optimized with the genetic algorithm (GA). The effectiveness of the proposed approach is presented with simulation studies.

Intelligence control method and application for decomposing furnace

Abstract: In order to overcome the control difficulties resulted from the characteristics of decomposing furnace, such as non-linear, time-varying and large time delay, a multi-mode intelligent control method is proposed in the paper by the combination of fuzzy control, Bang-Bang control, feed forward control, expert control and variable integral PID control. This control method through a multi-mode intelligent control rules automatically identify the different modes and select a appropriate control algorithm to correct variable integral PID control. Industrial applications show that the control system has good robustness, obtain good control results, and enable enterprises to achieve 3% coal saving and its comprehensive energy consumption reduced by 1.5%.