Showing papers on "Proportional control published in 2007"

Predictive Control of a Three-Phase Neutral-Point-Clamped Inverter

Abstract: A new predictive strategy for current control of a three-phase neutral-point-clamped inverter is presented. The algorithm is based on a model of the system. From that model, the behavior of the system is predicted for each possible switching state of the inverter. The state that minimizes a given quality function is selected to be applied during the next sampling interval. Several compositions of are proposed, including terms dedicated to achieve reference tracking, balance in the dc link, and reduction of the switching frequency. In comparison to an established control method, the strategy presents a remarkable performance. The proposed method achieves comparable reference tracking with lower switching frequency per semiconductor and similar transient behavior. The main advantage of the method is that it does not require any kind of linear controller or modulation technique, achieving a different approach to control a power converter.

Predictive Torque Control for Inverter-Fed Induction Machines

Abstract: This paper presents a predictive control scheme that is suitable for the torque and flux control of multilevel inverter-fed induction machines. The control strategy combines the use of a proportional-integral controller to obtain good steady-state behavior and a predictive controller to achieve fast dynamic torque response. In this way, torque and stator flux references can be reached within one sample period. With the use of multilevel space phasor modulation, low torque and flux ripple are possible with fixed sample rate. Experimental and simulation results are presented in order to demonstrate the effectiveness of the proposed strategy

A Design Method for PI-like Fuzzy Logic Controllers for DC–DC Converter

Abstract: This paper proposes a novel design procedure of proportional and integral (Pl)-like fuzzy logic controller (FLC) for DC-DC converters that integrates linear control techniques with fuzzy logic. The design procedure allows the small signal model of the converter and linear control design techniques to be used in the initial stages of FLC design. This simplifies the small signal design and the stability assessment of the FLC. By exploiting the fuzzy logic structure of the controller, heuristic knowledge is incorporated in the design, which results in a nonlinear controller with improved performance over linear PI controllers.

A Model-Free Cross-Coupled Control for Position Synchronization of Multi-Axis Motions: Theory and Experiments

Abstract: In this brief, a model-free cross-coupled controller is proposed for position synchronization of multi-axis motions. The position synchronization error of each axis is defined as the differential position error between this axis and its two adjacent axes, which is then coupled with the position error to form a coupled position error. A proportional and derivative (PD)-type synchronization controller with feedback of this coupled position error is proposed and proven to guarantee asymptotic convergence to zero of both position and synchronization errors in a setpoint position control. A setpoint tracking controller is further developed by adding feedforward control terms and a saturation function to the PD synchronization controller. The proposed method is easy to implement in practice since it is model free and the control gains are time-invariant. Experiments are performed to verify effectiveness of the proposed approach

Optimal fast tracking observer bandwidth of the linear extended state observer

Abstract: In current industrial control applications, the proportional + integral + derivative (PID) control is still used as the leading tool, but constructing controller requires precise mathematical model of plant, and tuning the parameters of controllers is not simple to implement. Motivated by the gap between theory and practice in control problems, linear active disturbance rejection control (LADRC) addresses a set of control problems in the absence of precise mathematical models. LADRC has two parameters to be tuned, namely, a closed-loop bandwidth and observer bandwidth. The performance of LADRC depends on the quick convergence of a unique state observer, known as the extended state observer, proposed by Jinqing Han (1994). Only one parameter, observer bandwidth, significantly affects the tracking speed of extended state observer. This paper studies numerically the optimal fast tracking observer bandwidth and the absolute tracking error estimation for a class of non-linear and uncertain motion control probl...

Fuzzy–Neural Sliding-Mode Control for DC–DC Converters Using Asymmetric Gaussian Membership Functions

Abstract: A fuzzy-neural sliding-mode (FNSM) control system is developed to control power electronic converters. The FNSM control system comprises a neural controller and a compensation controller. In the neural controller, an asymmetric fuzzy neural network is utilized to mimic an ideal controller. The compensation controller is designed to compensate for the approximation error between the neural controller and the ideal controller. An online training methodology is developed in the Lyapunov sense; thus, the stability of the control system can be guaranteed. Finally, to investigate the effectiveness of the FNSM control scheme, it is applied to control a pulsewidth-modulation-based forward dc-dc converter. Experimental results show that the proposed FNSM control system is found to achieve favorable regulation performances even under input-voltage and load-resistance variations

The optimal location of piezoelectric actuators and sensors for vibration control of plates

Abstract: This paper considers the optimal placement of collocated piezoelectric actuator–sensor pairs on a thin plate using a model-based linear quadratic regulator (LQR) controller. LQR performance is taken as objective for finding the optimal location of sensor–actuator pairs. The problem is formulated using the finite element method (FEM) as multi-input–multi-output (MIMO) model control. The discrete optimal sensor and actuator location problem is formulated in the framework of a zero–one optimization problem. A genetic algorithm (GA) is used to solve the zero–one optimization problem. Different classical control strategies like direct proportional feedback, constant-gain negative velocity feedback and the LQR optimal control scheme are applied to study the control effectiveness.

Passivity-Based Control of Buck Converters with Constant-Power Loads

Abstract: This paper studies the control of buck converters subjected to constant-power loads using a passivity-based technique. This technique allows for global analysis and avoids the limitations present in small-signal-based techniques. Passivity-based control in this application leads to a systematic derivation of a linear proportional-differential controller. It is also proved that the equilibrium point is only locally stable due to the infeasibility of duty ratio values larger than unity. The paper presents a method to obtain the region of attraction and shows that this region is not affected by controller gains. Experimental work is included to verify the analysis.

Performance of a Simple Tuned Fuzzy Controller and a PID Controller on a DC Motor

Abstract: We are presenting the usefulness of an innovative method called simple tuning algorithm (STA) for tuning fuzzy controllers, it has only one variable to adjust to achieve the tuning goal, this in counterpart to other methods like the proportional integral derivative (PID) controller wish has three variables to adjust for the same goal. Comparative examples of the STA and the PID methods are presented in a speed control of a real DC gear motor application. The PID controller was tuned using the Ziegler-Nichols. In base of the obtained quantitative and qualitative measures and observations, we are concluding that the fuzzy controller performance outperformed the PID controller; moreover, the tuning process using the STA method was easier than using the Ziegler-Nichols method

Neural Network Control for Position Tracking of a Two-Axis Inverted Pendulum System: Experimental Studies

Abstract: In this paper, experimental studies of a decentralized neural network control scheme of the reference compensation technique applied to control a 2-degrees-of-freedom (2-DOF) inverted pendulum on an x-y plane are presented. Each axis is controlled by two separate neural network controllers to have a decoupled control structure. Neural network controllers are applied not only to balance the angle of pendulum, but also to control the position tracking of the cart. The decoupled control structure can compensate for uncertainties and cancel coupling effects. Especially, a circular trajectory tracking task is tested for position tracking control of the cart while maintaining the angle of the pendulum. Experimental result shows that position control of the inverted pendulum and cart is successful.

The myopic Order-Up-To policy with a proportional feedback controller

Abstract: We develop a discrete control theory model of a myopic Order-Up-To (OUT) policy reacting to a stochastic demand pattern with Auto Regressive and Moving Average (ARMA) components. We show that the bullwhip effect arises with such a policy despite the fact that it is optimal when the ordering cost is linear. We then derive a set of z-transform transfer functions of a modified OUT policy that allows us to avoid the bullwhip problem by incorporating a proportional controller into the inventory position feedback loop. With this technique, the order variation can always be reduced to the same level as the demand variation. However, bullwhip-effect avoidance always comes at the cost of holding extra inventory. When the ordering cost is piece-wise linear and increasing, we compare the total cost per period under the two types of control policies: with and without bullwhip-effect reduction. Numerical examples reveal that the cost saving can be substantial if the order variance is reduced by using the proportional controller.

Adaptive backstepping for switching control active magnetic bearing system with vibrating base

Abstract: This research aims to test the limits of control effectiveness for an active magnetic bearing (AMB) system subjected to external acceleration disturbances. An adaptive output backstepping controller is designed to compute nonlinear control currents of the magnetic bearing by accepting that the rotor and AMB parameters are unknown. The control currents of the electromagnets of the active magnetic bearing is switched according to the rotor position. The adaptive backstepping controller is experimentally verified in an AMB test system with vibrating base and the results are compared with proportional integrative derivative (PID) control results for the maximum amplitude of applicable disturbance.

Fast Worm Containment Using Feedback Control

Abstract: In a computer network, network security is accomplished using elements such as firewalls, hosts, servers, routers, intrusion detection systems, and honey pots. These network elements need to know the nature or anomaly of the worm a priori to detect the attack. Modern viruses such as Code Red, Sapphire, and Nimda spread quickly. Therefore, it is impractical if not impossible for human mediated responses to these fast-spreading viruses. Several epidemic studies show that automatic tracking of resource usage and control provides an effective method to contain the damage. In this paper, we propose a novel security architecture based on the control system theory. In particular, we describe a state-space feedback control model that detects and control the spread of these viruses or worms by measuring the velocity of the number of new connections an infected host makes. The mechanism's objective is to slow down a worm's spreading velocity by controlling (delaying) the number of new connections made by an infected host. A proportional and integral (PI) controller is used for a continuous control of the feedback loop. The approach proposed here has been verified in a laboratory setup, and we were able to contain the infection so that it affected less than 5 percent of the hosts. We have also implemented a protocol for exchanging control-specific information between the network elements. The results from the simulation and experimental setup combined with the sensitivity analysis demonstrate the applicability and accuracy of the approach.

Stochastic optimization of bipedal walking using gyro feedback and phase resetting

Abstract: We present a method to optimize the walking pattern of a humanoid robot for forward speed using suitable metaheuristics Our starting point is a hand-tuned open-loop gait that we enhance with two feedback control mechanisms First, we employ a P-controller that regulates the foot angle in order to reduce angular velocity of the robot's body Second, we introduce a phase resetting mechanism that starts the next step at the moment of foot contact Using a physics-based simulation, we demonstrate that such feedback control is essential for achieving fast and robust locomotion

Automatic Mode Switching of P/PI Speed Control for Industry Servo Drives Using Online Spectrum Analysis of Torque Command

Abstract: Conventional proportional/proportional-integral (P/PI) speed controller for today's servo drives has to be manually tuned at the controller switching set point by trial and error, which may translate into drive system downtime and a subsequent loss of productivity. The adjustable drive performance is heavily dependent on the quality of expert knowledge. The performance becomes inadequate in applications where the operating conditions change in a wide range, i.e., tracking command, acceleration/deceleration time, and load disturbances. In this paper, we discuss the demands on simple controls/setups for industry servo drives. Analyzing the frequency content of the motor torque command, P/PI speed control mode switching is automatically performed with only a prior knowledge of the mechanical time constant. The dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time over the entire set of operating conditions. For a comprehensive comparison of conventional P/PI control scheme, we carried out extensive tests on an actual servo system.

Enhanced ITER resistive wall mode feedback performance using optimal control techniques

Abstract: In order to achieve the highest plasma pressure limits in ITER, resistive wall kink mode stabilization is required A novel resistive wall mode linear observer and feedback controller designed using model reduction and optimal control theory and employing only proportional gain are described here that allow operation of ITER up to Cβ = 86% of the ideal wall limit using the present design external control coils The full VALEN finite element ITER model containing ~3000 modes was reduced to a minimum of 8 modes making real-time controller implementation possible We find an order of magnitude reduction of the required control coil current and voltage in the presence of white noise from the no-wall limit to the optimal feedback system performance limit as compared with a traditional, classical controller

System Identification and Control of an Aerobot Drive System

Abstract: Fast thrust changes are important for authoritive control of VTOL micro air vehicles. Fixed-pitch rotors that alter thrust by varying rotor speed require high-bandwidth control systems to provide adequate performace. We develop a feedback compensator for a brushless hobby motor driving a custom rotor suitable for UAVs. The system plant is identified using step excitation experiments. The aerodynamic operating conditions of these rotors are unusual and so experiments are performed to characterise expected load disturbances. The plant and load models lead to a proportional controller design capable of significantly decreasing rise-time and propagation of disturbances, subject to bus voltage constraints.

Adaptive Idle Speed Control for Internal Combustion Engines

Abstract: The paper presents an application of a recently developed adaptive posicast controller for time-delay systems to the idle speed control (ISC) problem in internal combustion (IC) engines. The objective is to regulate the engine speed at a prescribed set-point in the presence of accessory load torque disturbances such as air conditioning and power steering. The adaptive controller, integrated with the existing proportional spark controller, is used to drive the electronic throttle as an actuator. We present both simulation and experimental results which demonstrate the potential of the adaptive controller to improve the performance. In addition, the reduction in calibration time and effort which can be achieved with our approach is discussed.

Feedback control laws for proof-mass electrodynamic actuators

Abstract: This paper presents a simulation study about the stability and performance of a control system with five decentralized feedback control units mounted on a flat panel in order to reduce its vibration and sound radiation. Each control unit consists of a proof-mass electrodynamic actuator with a velocity sensor at its base. The aim is to design light, simple, robust and low cost control units which can be attached in large numbers to flexible structures in order to control their spatially averaged response and sound radiation at low audio-frequencies. Thus four basic feedback control functions have been studied: (a) proportional, (b) integral (c) derivative and (d) PID. Two types of controllers have been considered which drive the actuators either with current or voltage signals. This paper shows that proportional control loops generate active damping which effectively reduces the frequency averaged response of the plate except at the fundamental resonance frequency of the actuator and at higher frequencies where control spillover effects take place. The PID control loops can mitigate these control spillover problems with no loss of control performance. Finally, integral and derivative control loops are characterized by important stability issues and also produce little control effects since they generate active stiffness and active mass effects which just shift the resonances of the plate structure.

Reference adjustment for a high-acceleration and high-precision platform via A-type of iterative learning control

Abstract: This paper studies the repetitive motion control of a high-acceleration and high-precision platform driven by linear motors. The control scheme comprises an anticipatory iterative learning control (A-ILC) component and a cascaded control structure including an inner-loop velocity PI controller and an outer-loop position P controller. During the motion process, the cascaded controller remains invariant while the A-ILC adjusts the reference command cycle by cycle to achieve better performance. Experiments are carried out to validate the proposed control structure. The results confirm that the proposed control scheme can improve the system performance significantly in both low-speed trajectory tracking motions and fast point-to-point motion. In the experiments, P-type and D-type ILCs are also utilized to adjust the reference command. Compared with the A type, P-type ILC leads to larger tracking error bounds and D-type ILC lacks a fast convergence rate for low-speed motions, while for fast point-to-po...

Automating tuning of a closed loop controller

Abstract: The present invention is a novel device, system, and method for simultaneous selection of filters and loop proportional gain for a closed loop system. According to an exemplary embodiment of the present invention, a method provides an automated selection of the portion of the controller known as the speed loop compensator. The method may operate on a frequency response function that represents the dynamic response from an actuation force (e.g. motor torque) to the sensor used for feedback of speed control (e.g. motor encoder angle). The frequency response function may be represented as a series of complex numbers each with a corresponding frequency value. The tuning method determines the combination of filter parameters that allows the loop proportional loop gain (Kp) to be maximized while meeting a specified set of criteria for stability margins. Methods for selecting integral gain and reference model are also presented

A Unified Approach for Stabilization of Arbitrary Order Continuous-Time and Discrete-Time Transfer Functions with Time Delay Using a PID Controller

Abstract: The object of this paper is to find the stability regions of an arbitrary order transfer function with time delay using a unified approach for continuous and discrete- time systems. The stability boundaries of the proportional- integral (PI) controller, proportional-derivative (PD) controller and proportional-integral-derivative (PID) controller are found in terms of the proportional gain ( p K ), integral gain ( i

Robust Iterative Learning Control of Output PDF in Non-Gaussian Stochastic Systems Using Youla Parametrization

Abstract: In this paper a robust iterative learning control (ILC) based control strategy is proposed for the shape control of the output probability density functions (PDF) for dynamic stochastic systems subjected to non-Gaussian variables. Using the radial basis function neural network (RBFNN) approximations to instant output PDFs, the output PDF tracking problem has been reduced to the weight control of the neural network. Furthermore, by separating the whole control horizon into certain number of the time domain sub- intervals called Batches, a control algorithm is established where the Youla parametrization technique has been used together with a proportional plus differential (PD) version of the ILC. The proportional part of the ILC law looks after the tuning of the RBFNN basis function parameters (i.e., the RBF centers and widths) whilst the differential part of the ILC law is used to tune the parameters of Youla-parameterized controller so that the closed-loop output PDF tracking performance is improved versus the advances of batches along the time horizon. The analysis on the proposed ILC convergence is made and demonstrable simulation results are also provided to show the effectiveness of the obtained control algorithm.

Zero Vibration On-Off Position Control of Dual Solenoid Actuator

Abstract: Solenoids are low cost, high speed, nonlinear actuators commonly used in switching mode. This paper presents a dual solenoid actuator system for high speed positioning applications. A novel control method that combines on-off control and input shaping is used to obtain low vibration, smooth transients when compared with traditional proportional control and on-off control. Simulation results and experimental data confirm that this dual solenoid position actuator with novel control method is effective and practical.

Setpoint Chasing for Thruster-Assisted Position Mooring

Abstract: This paper presents a new concept for control of thruster-assisted position moored vessel using setpoint chasing. The mooring system is designed to compensate the mean environmental loads up to a certain limit of the environmental conditions. In the present industrial position mooring (PM) system, the thrusters are used to damp the vessel’s dynamical motions and to provide compensation of any line break. The main contribution in this paper is to extend the damping control used in industrial PM system with improved restoring and mean force control. In order to avoid conflicting control action with the mooring system, the equilibrium position of the uncontrolled vessel will be found using setpoint chasing. The setpoint chasing with proportional control will be developed to prevent a possible resonance situation by shifting the natural frequency of the moored vessel out of the bandwidth of the excitation loads. The setpoint chasing with integral control will improve the ability to prevent line break in extreme conditions by compensating the mean drift loads together with the mooring system. Simulation and experiment will be carried out to verify the advantages of the setpoint chasing strategies.Copyright © 2007 by ASME

Stability of a heat exchanger feedback control system using the circle criterion

Abstract: The standard linearized model of a controlled heat exchanger in the form of a system of two first-order PDEs is interpreted as an abstract semigroup system on an appropriately selected Hilbert state space. We analyse some its basis properties: exponential stability, admissibility of an observation functional and regularity of the system impulse response. Next we give a proof of a version of the circle criterion which bases on the use of the Leray–Schauder fixed point theorem jointly with a uniqueness result. The circle criterion is then implemented to a feedback control system of the heat exchanger with a proportional controller and a non-linear valve in the feedback loop. All considerations are illustrated by a numerical example of the heat exchanger installed in central heating system at the AGH University of Science and Technology, Cracow, Poland, for which we estimate feasible settlements of the proportional controller.

Step-Wise Optimum Adaptive Variable-Structure Load-Frequency Control Design Using Simulated Annealing

Abstract: This paper presents three optimum adaptive variable-structure controllers and their applications to load frequency control (LFC) of an interconnected power system, namely, optimum dither (DT), optimum proportional-integral (PI), and optimum variable input (VI) control. The aim of this work is to maintain robustness while reducing the chattering effect in variable structure control (VSC) at the same time fulfilling the LFC requirements. Contrary to the widely used trial-and-error technique, the proposed approaches allow the determination of the controller gains systematically and adaptively in a step-wise fashion using simulating annealing, a well known robust optimization technique. The VSC gains computation problem is converted to an optimization problem using a suitable cost function that is based on Lyapunov theory of VSC. Comparison study is carried out between the proposed approaches as applied to the power system subjected to disturbances variation and parameters change with the presence of the system inherent nonlinearity.