Showing papers on "Proportional control published in 2003"

Robust load frequency control using genetic algorithms and linear matrix inequalities

Abstract: In this paper, two robust decentralized control design methodologies for load frequency control (LFC) are proposed. The first one is based on H/sub /spl infin// control design using linear matrix inequalities (LMI) technique in order to obtain robustness against uncertainties. The second controller has a simpler structure, which is more appealing from an implementation point of view, and it is tuned by a proposed novel robust control design algorithm to achieve the same robust performance as the first one. More specifically, genetic algorithms (GAs) optimization is used to tune the control parameters of the proportional-integral (PI) controller subject to the H/sub /spl infin// constraints in terms of LMI. Hence, the second control design is called GALMI. Both proposed controllers are tested on a three-area power system with three scenarios of load disturbances to demonstrate their robust performances.

A comparative analysis of multiloop voltage regulation strategies for single and three-phase UPS systems

Abstract: Most of the many reported control algorithms for uninterruptible power supplies (UPSs) use either filter inductor or filter capacitor currents as feedback variables to regulate the output voltage. This paper explores the fundamental performance issues associated with the use of these quantities as feedback variables, with a view to determining their contribution to the transient system response and output harmonic compensation in any particular situation. A proportional plus resonant (P+resonant) compensator is then added into the outer voltage regulation loop to achieve zero steady error, to develop a high performance UPS control algorithm, which is applicable to both single-phase and three-phase systems. Theory, simulation, and experimental results are presented in the paper.

GA-based multiobjective PID control for a linear brushless DC motor

Abstract: This paper presents a robust output tracking control design method for a linear brushless DC motor with modeling uncertainties. Two frequency-domain specifications directly related to the mixed sensitivity function and control energy consumption are imposed to ensure stability and performance robustness. With regard to time-domain specifications, the rise time, maximum overshoot and steady-state error of the step response are considered. A generalized two-parameters proportional, integral, and derivative (PID) control framework is developed via a genetic searching approach ensuring the specifications imposed. The proposed design method is intuitive and practical that offers an effective way to implement simple but robust solutions covering a wide range of plant perturbation and, in addition, provides excellent tracking performance without resorting to excessive control. Extensive experimental and numerical results for a linear brushless motor confirm the proposed control design approach.

Bi-directional field control for proportional control based generator/alternator voltage regulator

Abstract: An H-bridge switching topology for bi-directional field excitation to null the effects of a rotor's permanent magnets uses both a low-side and a high-side field excitation driver to control the rotor's average field current. A standard proportional control signal for generators using uni-directional field excitation is used to control an H-bridge for bi-directional field excitation. The H-bridge consists of two pair of power switches. In a preferred embodiment, the switches are n-channel MOSFETs. A drive circuit interfaces a logic block with the H-bridge in order to properly bias the power switches.

Design of incremental fuzzy PI controllers for a gas-turbine plant

Abstract: In this paper, incremental fuzzy proportional integral (PI) speed and temperature controllers for a heavy-duty gas-turbine plant are presented. To improve performance, an analysis of incremental fuzzy PI control is provided, and new fuzzy control rules are proposed. In applying the fuzzy PI control to a gas-turbine plant, all gains are optimized by an adaptive genetic algorithm. We show the performance improvement of the proposed controller compared with conventional PI controller via simulations.

On the stability and controller robustness of some popular PID tuning rules

Abstract: In this note, we study the stability and controller robustness of some popular proportional-integral-derivative (PID) tuning techniques that are based on first-order models with time delays. Using the characterization of all stabilizing PID controllers derived in a previous paper, each tuning rule is analyzed to first determine if the proportional gain value dictated by that rule, lies inside the range of admissible proportional gains. Then, the integral and derivative gain values are examined to determine conditions under which the tuning rule exhibits robustness with respect to controller parameter perturbations.

Dynamics and control of an electro-hydraulic fully flexible valve actuation system

Abstract: As the internal combustion engine moves into the 21/sup st/ century, fully flexible valve actuation (FFVA) systems are being proposed as an enabling technology for advanced internal combustion engine concepts. This paper focuses on exploring the dynamics and control of an electro-hydraulic fully flexible valve actuation system. Challenges and approaches for developing variable valve actuation systems are first outlined and discussed. Dynamic model of the electro-hydraulic actuator was obtained based on experimental data. A robust repetitive controller is then designed and implemented using a dSpace system. We are able to achieve valve profile tracking errors within 140 microns for a 9.5 mm lift at engine speed up to 3000 rpm. To demonstrate the flexibility and robustness of the system, we show real-time valve-lift profiles used to explore advanced combustion technologies.

Using a high order sliding modes for diving control a torpedo autonomous underwater vehicle

Abstract: In this paper, a high order sliding modes control (HOSMC) is used to control TAIPAN, a torpedo shaped AUV from LIRMM, France. The implementation of a second order sliding mode controller in this system is the main contribution of this work. Sliding mode control (SMC) is adequate for controlling AUVs, since it offers robustness in the presence of uncertainties parameters and environmental disturbances, however the main drawback is the chattering effects that stimulates high frequency vibration that can damage the actuators. HOSMC control preserves the properties of standard SMC and removes the chattering effects. The design of proportional derived (PD), SMC and HOSMC controller for control TAIPAN depth are described. A comparative study between the control laws is presented. The nonlinear hydrodynamic model of TAIPAN is used in the numerical simulations. Simulation results, that enlighten performance of the automatic controllers are shown.

NERC compliant decentralized load frequency control design using model predictive control

Abstract: This paper presents a decentralized model predictive control (MFC) design for the load frequency control (LFC) problem. The proposed algorithm has two objectives, (1) to assure compliance with control performance standards CPS1 and CPS2 set by NERC, and (2) to reduce wear and tear of generating units. A nonlinear simulation of a test system with multiple generation and distribution companies including regulation and load following services is performed to illustrate the proposed control scheme.

Coaxial two-wheeled vehicle

Abstract: PROBLEM TO BE SOLVED: To provide a coaxial two-wheeled vehicle which is stable against fluctuation of load weight and stably provides both attitude control and travel control. SOLUTION: An attitude controller 84 calculates a motor torque Tgyr for keeping a base at a target angle based on the deviation between a base angle instruction θref which is an attitude instruction and a current base angle θ 0 that is calculated using a gyro-sensor 13 and an acceleration sensor 14. Meanwhile, a position proportional controller 86R, a differentiator 88R, and a speed proportional controller 89R perform PD control for the deviation between the rotational position instruction Prefr of a motor rotor 92R for a right wheel and the current rotational position θr of the motor roller 92R. A current control amplifier 91R generates a motor current based on the value of a motor torque which is a control result added with an estimated load torque T 1 ' calculated using the motor torque Tgyr and a pressure sensor for driving the motor rotor 92R. COPYRIGHT: (C)2005,JPO&NCIPI

Position control apparatus for motor

Abstract: An electric motor position control apparatus in accordance with the present invention has a plurality of sets of control parameters including at least the proportional gain of a position control section and the proportional gain of a speed control section beforehand, wherein set selection and the measurement of the response state of an electric motor to a position command at the time when the electric motor is controlled by using the control parameters of the selected set are carried out sequentially, one preferable set is selected depending on the measured response state, the control parameters of the selected set are set, and the control parameters are changed as a set.

Intelligent feedforward control and payload estimation for a two-link robotic manipulator

Abstract: Conventional model-based computed torque control fails to produce a good trajectory tracking performance in the presence of payload uncertainty and modeling error. The challenge is to provide accurate dynamics information to the controller. A new control architecture that incorporates a neural-network, fuzzy logic and a simple proportional-derivative (PD) controller is proposed to control an articulated robot carrying a variable payload. An off-line trained feedforward (multilayer) neural network takes payload mass estimates from a fuzzy-logic mass estimator as one of the inputs to represent the inverse dynamics of the articulated robot. The effectiveness of the proposed architecture is demonstrated by experiment on a two-link planar manipulator with changing payload mass. Experimental results show that this control architecture achieves excellent tracking performance in the presence of payload uncertainty.

Experimental study of anti-swing crane control for a varying load

Abstract: This paper presents an experimental study of anti-swing control for a robotic crane carrying a suspended varying load. The anti-swing controller is based on swing angle feedback, and the controller suppresses the swing motion of the load while the crane carries the load to a desired location. The analysis includes the nonlinear dynamics of the crane and two-dimensional swing motion. A simulation study is performed to show the effectiveness of the swing angle feedback controller compared with Proportional and Derivative (PD) and full state feedback controllers. Also, the anti-swing controllers are successfully implemented on an actual test bed. The experimental study demonstrates that the proposed swing angle feedhack controller performs better in terms of the robustness to the payload change.

Feedback control of oscillatory thermocapillary convection in a half-zone liquid bridge

Abstract: Active feedback control was applied to suppress oscillations in thermocapillary convection in a half-zone liquid bridge. The experiment is on a unit-aspect-ratio liquid bridge where the most unstable azimuthal mode has wavenumber 2 when control is absent. Active control was realized by locally modifying the surface temperature using the local temperature measured at different locations fed back through a simple control law. The performance of the control process was quantified by analysing local temperature signals, and the flow structure was simultaneously identified by flow visualization. With optimal placement of sensors and heaters, proportional control can raise the critical Marangoni number by more than 40%. The amplitude of the oscillation can be suppressed to less than 30% of the initial value for a wide range of Marangoni number, up to 90% of the critical value. The proportional control was tested for a period-doubling state and it stabilized the oscillation to a periodic state. Weakly nonlinear control was applied by adding a cubic term to the control law to improve the performance of the control and alter the bifurcation characteristics.

Active queue management using proportional control and rate-based information

Abstract: Disclosed is an Active Queue Management method and apparatus which uses traffic rate information for congestion control. Using a nonlinear fluid-flow model of Traffic Control Protocol, a proportional controller in a closed loop configuration with gain settings characterized for stable operation allows a matching of the aggregate rate of the active TCP connections to the available capacity. Further disclosed is a method for calculation of the regime of gains for which stable operation of a given network obtains. This approach allows for capacity matching while maintaining minimal queue size and high link utilization.

Pseudo-PID tracking control for a class of output PDFs of general non-Gaussian stochastic systems

Abstract: In this paper a pseudo-PID control strategy is presented for a class of non-Gaussian stochastic systems. To control the output probability density functions (PDFs) to track a given target function, the PID-type control structure is imposed a priori. Following the B-spline approximation on the measured output PDFs, the control objective is transferred into the tracking of given weights which correspond to the desired PDF. For systems with or without model uncertainties, it is shown that the solvability can be cast into a group of matrix inequalities. This leads to a feasible controller design procedure that can guarantee the required tracking convergence with enhanced robustness.

Proportional control system for a motor

Abstract: The present invention provides a proportional control system for use in an HVAC unit within a ventilation system comprising a processing means (130) programmed with an air exchange - defrost cycle. One or more motor speed sensing means are positioned in the HVAC unit and operatively connected to the processing means (130) and one or more temperature sensing means (120) are positioned in the HVAC unit and operatively connected to the processing means (130) wherein the temperature and motor speed sensors determine the motor speed to be applied during the defrost cycle.

Position controller of motor

Abstract: A position controller of a motor in which the positioning set time can be shortened even if an external force is applied. A speed control section (13) comprises a low-pass filter (133) compensating for the speed control side delay having a transfer function corresponding to the delay of a speed control system. The speed control section (13) further comprises an integration control system including a speed integrator (132) for integrating the difference between a speed and a delay speed command obtained by inputting a speed command to the low-pass filter (133) compensating for the speed control side delay, a proportional control system delivering a command proportional to the speed command, and a multiplying means (134) for multiplying the sum of outputs from the integration control system and the proportional control system by a speed proportional gain and delivering the product as a torque command. A speed feedback low-pass filter (135) having a transfer function for preventing a ripple from appearing in the torque command due to a quantization error and/or a positional error at a position detecting section is also provided.

VGT turbocharger controlled by an adaptive technique

Abstract: This paper provides an adaptive technique for the control of the variable geometry turbine in a turbocharged compression ignition engine. The adaptive control is based on a one-step-ahead (OSA) technique and a least-square parameter estimator algorithm. In order to test the performance of the proposed control technique, a numerical model of the engine has been developed, which employs a thermodynamic (zero-dimensional) approach. The paper will show that the OSA technique is able to improve dramatically the control performance with respect to that provided by a commonly applied proportional integral derivative control technique.

Control apparatus for an electric power steering system

Abstract: A control apparatus for an electric power steering system is provided, which controls a motor for applying assist steering torque to a steering line of a vehicle at least according to steering torque signal of the steering line, vehicle velocity signal and motor current signal. The control apparatus includes a target current controller for setting target current signal for driving the motor, a deviation calculator for computing a deviation between the target current and motor current signals, a deviation adjuster for adjusting the deviation with a variable gain according to the vehicle velocity signal, a proportional element for executing proportional control for the motor, an integral element for executing integral control for the motor and an gain adjuster for adjusting the gain according to a differential of the steering torque signal.

Optimal distributed power control in cellular wireless systems

Abstract: In this paper, an optimal fast closed-loop SIR-based power control scheme is proposed for CDMA systems. The state-of-the-art of this power control algorithm is that the power evolution is directly driven by the error between the actual SIR and the desired SIR. The amount of power change is proportional to the error, and the optimal gain is chosen to achieve the minimum error at the next time instant. Assuming perfect estimation and prediction, the error between the desired SIR and the real value of SIR goes to zero in one step. In practical situations, where the estimator need several (3-4) steps to make accurate estimation and prediction, the error between the desired SIR and the real value of SIR goes to zero in several (4-5) steps. The proposed controller is an estimator based controller. The performance of the estimator will have direct impact on the performance of the power control scheme. Simulations of a CDMA system are performed to demonstrate effectiveness of the proposed power control scheme. The simulation results, in all cases, confirm theoretical analysis. These results indicate that the proposed optimal power control scheme is a very promissing solution to the distributed fast closed-loop power control problem in wireless systems, both theoretically and practically. I. Review of SIR based Power Control in Cellular Wireless Systems In a cellular wireless network, certain quality-of-service (QoS) should be maintained for all active users in the network. A quantity that measures the user’s provided QoS is the signal-to-interference ratio (SIR). The initial work on SIR-based power control schemes for narrowband systems has been done by Zander [1]-[3]. Power control schemes can be centralized [1]-[3] or distributed [2],[4],[6] according to the nature of computations. A centralized controller has information (e.g., all the link gains) for each user and it decides control actions for all users. On the other hand, a distributed controller only uses local information to make a control action for a user. For example, [2],[4],[6] only use information about user’s own link gain and/or SIR to make a decision about their transmitted power. The algorithm convergence has to be studied carefully when a distributed power control scheme is used. The distributed power control algorithm by Foschini [6] was shown to converge either synchronously [6] or asynchronously [9]. The basic model in [6] is relaxed in [9] to allow asynchronism. Propagation delay is also considered in [9]. A framework for convergence of the generalized uplink power control was proposed by Yates [10]. In recent years, there have been increasing interests in applying code-division-multipleaccess (CDMA) techniques to cellular wireless networks. Unlike the narrowband systems, users in a CDMA system share the same frequency all the time by using a specific spread spectrum pseudonoise code for each user. The system performance mainly depends on socalled multiple access interference (MAI), which is caused by the cross-correlations between the desired signal and other signals. Open-loop power control has been employed to combat the path loss and shadow fading. The average power control in [10],[22] keeps the local mean received power to a constant value, which mitigate the effect of shadowing and near-far problems. In IS-95B [20] and CDMA2000 [21], fast closed-loop power control is proposed to fight medium to fast fading. In [11]-[12], it is shown that when power control rate is higher, it can partially accomodate the effect of fast fading. Herdtner and Chong [9] considered a simple distributed power control scheme in which the convergence condition was given. Wu [13] extended Zander’s problem formulation to CDMA systems by reordering the number of users in different cells. Song et.al. [14]-[15] and Gunnarsson et.al. [16]-[17] considered up/down power control and closed-loop power control with other nonlinear elements within the framework of nonlinear control systems. [14]-[15] gave guidelines for choosing the appropriate power control step size in IS-95. In [16]-[17], PID controllers were designed to overcome the effects of time-delay in the feedback loop. Filtering techniques have been also used to design power control schemes. Leung [18] proposed a power control scheme for TDMA data service based on the Kalman filtering technique. In [31], a linear prediction of received power is made at the base station to predict the power control bit one step ahead. Both approaches assume that the interference is Gaussian. In this paper, an optimal fast closed-loop SIR-based uplink power control scheme is proposed for CDMA systems. In Section 2, a proportional controller is proposed and the optimal power control gain is derived by unconstrained optimization. In Section 3, the constraints are imposed on the maximum and minimum values of transmitter power. By applying the Kuhn-Tucker conditions, we derive the optimal gain for the proportional controller. Using Bellman’s optimality principle, the power control scheme achieves optimality in the whole time interval of interest. The proposed controller is an estimator based controller. The performance of the estimator will have direct impact on the performance of the power control scheme. Section 4 gives our choice of the estimator. In contrast to the well-known Kalman filter, which assumes that system and measurement disturbances are white Gaussian stochastic processes and requires the knowledge of their statistics, the H∞ filter, used in the proposed scheme, facilitates the system filtering regardless of the nature of the system and measurement disturbances. It meets our estimation requirement since the fluctuation of the interference is not Gaussian and its statistics is not known in general [18]. Simulations of a CDMA system are performed to demonstrate the effectiveness of the proposed power control scheme. The results are shown in Section 5. II. Optimal SIR-based Distributed Power Control by Unconstrained Optimization In this paper, only uplink (mobile-to-base) power control is considered. Suppose that there are N active users in the system. The Signal-to-Interference Ratio (SIR) in a CDMA system is defined as Definition 1: The SIR of an active link from mobile station i to base station n in a wireless system is defined as γni = Lhnipi ∑ j 6=i hnjpj + σ 2 (1) where hni is the link gain from mobile station i to base station n. We assume that L is the processing gain in spread spectrum wireless systems, e.g., in CDMA 2000, L=64 or 128 or 256. Let us denote the denominator by Ii, which represents the received interference, then the SIR can be rewritten as γni = Lhnipi Ii (2) Assuming that a mobile only transmits to one base station during the time of power control, then γni can be simplified as γi. Let δi = Lhni Ii denote the channel variation [11]. δi will be estimated and predicted in the proposed power control scheme. Given that a mobile station and its base station communicate directly to each other, we assume that hni can be estimated accurately. We also assume that the received interference Ii can be measured at each time step. The received interference is the difference between the total received power and the desired signal power [10]. The main idea of the proposed algorithm is to make the transmission power proportional to the error between the actual SIR and the desired SIR. Define the transmission power change from time step k to k + 1 as ∆pi(k + 1) = pi(k + 1)− pi(k) (3) where pi(k) and pi(k + 1) are the transmission powers from mobile i to the base station at the time instants k and k +1, respectively. Let the error between the actual SIR (γi(k)) and the desired SIR (γ i ) be denoted by ei(k) for mobile i at the time instant k, ei(k) = γ tar i − γi(k) (4) We propose the following power control algorithm ∆pi(k + 1) = αi(k)ei(k) =⇒ pi(k + 1) = pi(k) + αi(k)(γ tar i − γi(k)) (5) where αi(k) is the gain to be determined through the optimization procedure in which the square of the error is minimized (theoretically reduced to zero in each discrete-time instant k). The main result of this paper is presented in the following theorem. Theorem 1: Define the performance criterion at the time instant k as Ji(k) = min αi(k) (ei(k + 1)) 2 , i = 1, 2, ..., N. (6) The optimal gains of the power control algorithm (5) that minimize Ji(k) at every time instant k are given by

Work vehicle including start-up control current calibration mechanism for proportional control systems

Abstract: A method of calibrating the control current start-up threshold in a proportionally controlled drive system (11) for a work vehicle (10) is disclosed. To determine a current threshold value for use in the system (11) a control current (IC1/IC2) exhibiting a relatively low value is first applied to the system. Subsequently, the steps of repetitively increasing the control current to a control current start value at which system motion starts and decreasing the control current to a control current stop value at which system motion substantially stops are repetitively conducted. The resultant control current start values and control current stop values are stored in a memory (117). The stored control current start values and control current stop values are then averaged to determine a control current threshold value for use in controlling the system.

Sensorless vector control of induction motor using improved self-tuning fuzzy PID controller

Abstract: This paper presents a neural network based self-tuning fuzzy PID control scheme with variable learning rates for sensorless vector controlled induction motor drives. When induction motor is continuously used long time, its electrical and mechanical parameters would change, which degrade the performance of PID controller considerably. This paper re-analyzes the fuzzy controller as conventional PID controller structure, introduces a single neuron with a back-propagation learning algorithm to tune the control parameters, and proposes a variable learning rate to improve the control performance. For sensorless vector control, the rotor speed is estimated using MRAS (model reference adaptive system). The proposed scheme is simple in structure and its computational burden is small. The performance of the proposed scheme is evaluated on some experimental studies.

A multi-rate nonlinear state estimation for hard disk drives

Abstract: In this paper, we propose a new multi-rate state estimator for seeking control of hard disk drives, which has a proportional, integral, and discontinuous error feedback structure to improve robustness. Conventional state estimators do not have enough accuracy under the existence of external disturbances and model uncertainty. With the proposed estimator, the seeking control system of hard disk drives can have better robustness. Our main focus is on the discontinuous action, which alleviates the estimation error caused by, for example, actuator gain variations. Integral action is secondarily introduced not only to cancel out a quasi-constant disturbance and uncertainty, but also to reduce the chattering motion caused by the discontinuous feedback. Simulations and experiments have been carried out to validate our proposed multi-rate state estimator. Finally, an experimental example of seeking control for a single stage actuated hard disk drive is demonstrated.

Position controller of motor

Abstract: PROBLEM TO BE SOLVED: To provide a position controller of a motor capable of adjusting a control parameter in a short period of time with high responsiveness, without measuring in advance the frequency characteristics of an object to be controlled that has a resonance frequency. SOLUTION: The positional controller of a motor is equipped with a plurality of control parameter sets in advance which contain at least a proportional gain of a positional control part and that of a speed control part. Selecting a set and measuring a response state of a motor to the positional instruction when the motor is controlled using the control parameter of a selected set are sequentially performed. A desired single set is selected according to a measured response state. A set of selected control parameters is established and the control parameters are changed as a set. COPYRIGHT: (C)2004,JPO

Active suppression of finite-amplitude Rayleigh–Bénard convection

Abstract: We study by a fully nonlinear three-dimensional pseudospectral time-splitting simulation, the feedback control of a layer of fluid heated from below. The initial condition corresponds to a steady large-amplitude preferred convection state obtained at Prandtl number of 7.0 and Rayleigh number of 104, which is about six times the Rayleigh critical value. A robust controller based on the LQG (linear–quadratic–Gaussian) synthesis method is used. Both sensors and actuator are thermal-based, planar, andassumed to be continuously distributed. The simulated results show that large-amplitude steady-state convection rolls can be suppressed by the linear LQG controller action. The Green's function of the controller gives the shape of the control action corresponding to a point measurement. In addition, for Rayleigh numbers below the proportional feedback control stability limit, this controller appeared to be effective in damping out steady-state convection rolls as well. However, in a region very near the proportional control stability limit, proportional control action induces subcritical g-type hexagonal convection, which is obtained here through direct simulations. Note that well above this proportional control limit, the LQG still damps out all convection. The nonlinear plant model is validated by comparing check cases with published results.