Showing papers on "Open-loop controller published in 2001"

An optimal fuzzy PID controller

Abstract: This paper introduces an optimal fuzzy proportional-integral-derivative (PID) controller. The fuzzy PID controller is a discrete-time version of the conventional PID controller, which preserves the same linear structure of the proportional, integral, and derivative parts but has constant coefficient yet self-tuned control gains. Fuzzy logic is employed only for the design; the resulting controller does not need to execute any fuzzy rule base, and is actually a conventional PID controller with analytical formulae. The main improvement is in endowing the classical controller with a certain adaptive control capability. The constant PID control gains are optimized by using the multiobjective genetic algorithm (MOGA), thereby yielding an optimal fuzzy PID controller. Computer simulations are shown to demonstrate its improvement over the fuzzy PID controller without MOGA optimization.

Distributed model predictive control

Abstract: We explore a distributed model predictive control (DMPC) scheme. The controllers apply model predictive control (MPC) policies to their local subsystems. They exchange their predictions by communication and incorporate the information from other controllers into their local MPC problem so as to coordinate with each other. For the full local state feedback and one-step delayed prediction exchange case, stability is ensured for controllable systems satisfying a matching condition by imposing stability constraints on the next state in the prediction. An example of multi-area load-frequency control is used as an example application for this DMPC scheme to show the performance of the scheme.

A new controller architecture for high performance, robust, and fault-tolerant control

Abstract: We propose a new feedback controller architecture. The distinguished feature of our new controller architecture is that it shows structurally how the controller design for performance and robustness may be done separately which has the potential to overcome the conflict between performance and robustness in the traditional feedback framework. The controller architecture includes two parts: one part for performance and the other part for robustness. The controller architecture works in such a way that the feedback control system can be solely controlled by the performance controller when there is no model uncertainties and external disturbances and the robustification controller can only be active when there are model uncertainties or external disturbances.

Self-clocking multiphase power supply controller

Abstract: A ripple-mode controller provides reliable operation in multi-phase power supply circuits, over a variety of operating conditions. Cross-phase blanking allows the controller to preserve the desired phase relationship between the switching pulses its provides to the different output phases, and permits the controller to operate each output phase at nearly 100% duty cycles. Active current sharing compliments blanking operations by adjusting the width of switching pulses the controller provides to one or more of the output phases based on detecting load current imbalances between the different output phases. With active current sharing, the controller prevents one or more output phases from carrying excessive portions of the load current. Further complimenting its operation, the controller may include virtual ripple generation to increase the noise immunity of its ripple-mode regulation.

A nonlinear state observer for the sensorless control of a permanent-magnet AC machine

Abstract: This paper presents a sensorless speed regulation scheme for a permanent-magnet synchronous motor (PMSM) based solely on the motor line currents measurements. The proposed scheme combines an exact linearization-based controller with a nonlinear state observer which estimates the rotor position and speed. Moreover, the stability of the closed-loop system, including the observer, is demonstrated through Lyapunov stability theory. The proposed observer has the advantage of being insensitive to rotation direction. It is shown how a singularity at zero velocity appears in the scheme and how it can be avoided by switching smoothly from the observer-based closed-loop control to an open-loop control at low velocity. The system performance is tested with an experimental setup consisting of a PMSM servo drive and a digital-signal-processor-based controller for both unidirectional and bidirectional speed regulation.

Tension control for winding systems with two-degrees-of-freedom H/sub /spl infin// controllers

Abstract: In web transport systems, the main concern is to control independently speed and tension in spite of perturbations such as radius variations and changes of setting point. Multivariable controllers including gain scheduling have already given good results in that sense. Nevertheless, in these control techniques, tracking properties and perturbation rejection are interdependent and cannot be specified separately. In this paper, we present multivariable H/sub /spl infin// robust control with two degrees of freedom (2DOF) and gain scheduling applied to winding systems. Three controller structures are considered: a global controller, a semidecentralized controller, and a semidecentralized controller with overlapping. Simulation results are given, based on a nonlinear model identified on an experimental bench. In each case, the 2DOF controller is compared to the classical 1DOF controller. The 2DOF approach allows improving significantly disturbance rejection while reducing coupling between tension and velocity.

A fuzzy sliding controller for nonlinear systems

Abstract: It is well known that sliding-mode control can give good transient performance and system robustness. However, the presence of chattering may introduce problems to the actuators. Many chattering elimination methods use a finite DC gain controller which leads to a finite steady-state error. One method to ensure zero steady-state error is using a proportional plus integral (PI) controller. This paper proposes a fuzzy logic controller which combines a sliding-mode controller (SMC) and a PI controller. The advantages of the SMC and the PI controller can be combined and their disadvantages can be removed. The system stability is proved, although there is one more state variable to be considered in the PI subsystem. An illustrative example shows that good transient and steady-state responses can be obtained by applying the proposed controller.

Distributed control network for irrigation management

Abstract: A system and method for operating a distributed control network (fig3) for irrigation management The system incorporates several irrigation controllers (15) wherein each of the controllers (15) can transmit, receive and respond to commands initiated by any device or satellite controller (15) on the network (fig3), a communication bus (23) that is connected to the controllers (15), a central computer (25) that is connected to the bus (23), several sensing devices (21) that are connected to each controller (15), and several sprinkler valves (17) that are connected to each controller (15) The controllers (15) can be operated in local mode via a user interface and in a remote mode via a wireless connection (27) The controllers (15) are capable of monitoring and acknowledging the commands that are transmitted on the bus (23)

High-performance fully digital switched reluctance motor controller for vehicle propulsion

Abstract: A high-performance fully digital controller has been designed for the control of a switched reluctance (SR) motor built for vehicle propulsion. The SR machine is specifically designed and built to have high density and low noise. The controller is designed to maximize the machine efficiency, the peak overload capability, and to minimize torque ripple at low speed. Lookup tables are stored in a digital-signal-processor-based controller to calculate the control parameters online. Three interpolations, between torque command, motor speed, and battery voltage, are performed to obtain the control parameters. Difficulties associated with the interpolation scheme are addressed. A high-bandwidth fully digital proportional plus integral current regulator has been designed for the control of the phase current. Advantages as well as the difficulties with the operation of the SR machine and its control have been addressed. A complete characterization of the controller for the entire torque-speed plane has been made through extensive dyno testing. Simulation and dyno test results have been presented to demonstrate the performance of this controller.

High precision linear motor control via relay-tuning and iterative learning based on zero-phase filtering

Abstract: In this paper, with a modest amount of modeling effort, a feedback-feedforward control structure is proposed for precision motion control of a permanent magnet linear motor for applications which are inherently repetitive in terms of the motion trajectories. First, a proportional-integral-derivative (PID) feedback controller is designed using an automatic relay tuning method. An iterative learning controller based on zero-phase filtering is applied as feedforward controller to the existing relay-tuned PID feedback controller to enhance the trajectory tracking performance by utilizing the experience gained from the repeated execution of the same operations. Experimental results are presented to demonstrate the practical appeal and effectiveness of the proposed scheme.

Hybrid fuzzy proportional-integral plus conventional derivative control of linear and nonlinear systems

Abstract: This paper presents a new approach toward the optimal design of a hybrid proportional-integral-derivative (PID) controller applicable for controlling linear as well as nonlinear systems using genetic algorithms (GAs). The proposed hybrid PID controller is derived by replacing the conventional PI controller by a two-input normalized linear fuzzy logic controller (FLC) and executing the conventional D controller in an incremental form. The salient features of the proposed controller are as follows: (1) the linearly defined FLC can generate nonlinear output so that high nonlinearities of complex systems can be handled; (2) only one well-defined linear fuzzy control space is required for both linear and nonlinear systems; (3) optimal tuning of the controller gains is carried out by using a GA; and (4) it is simple and easy to implement. Simulation results on a temperature control system (linear system) and a missile model (nonlinear system) demonstrate the effectiveness and robustness of the proposed controller.

An adaptive fuzzy sliding-mode controller

Abstract: This paper deals with a new adaptive fuzzy sliding-mode controller and its application to a robot manipulator arm. The theory for this approach and for the heuristics-based linguistic adaptation is presented, and a mathematical description is derived. Furthermore, an application of this adaptive controller for a two-link robot arm is shown. The obtained results show the high efficiency of the new controller type.

A globally stable state feedback controller for flexible joint robots

Abstract: The paper addresses the problem of controlling the joints of a flexible joint robot with a state feedback controller and proposes a gradual way of extending such a controller towards the complete decoupling of the robot dynamics. The global asymptotic stability for the state feedback controller with gravity compensation is proven, followed by some theoretical remarks on its passivity properties. By proper parameterization, the proposed controller structure can implement a position, a stiffness or a torque controller. Experimental results on the DLR lightweight robots validate the method.

The application of ANN technique to load-frequency control for three-area power system

Abstract: This paper includes an application of layered artificial neural network controller to study the load-frequency control problem in a power system. The control scheme guarantees that steady state error of frequencies and inadvertent interchange of tie-lines are maintained in a given tolerance limitation. The proposed control has been designed for a three-area interconnected power system such that two areas include steam turbines and the other area includes a hydro turbine. Only one artificial neural network (ANN) controller, which controls the inputs of each area in the power system together, is considered. In the study, a back propagation-through-time algorithm is used as a neural network learning rule. The performance of the power system is simulated by using a conventional integral controller and ANN controller, separately. By comparing the results for both cases, the performance of an ANN controller is better than conventional controllers.

Unit controller with integral full-featured human-machine interface

Abstract: An integrated unit controller/human-machine interface is disclosed which incorporates high-speed redundant control, sequence of events, supervisory control and data acquisition, alarm handling, trending & historian, process graphics and “open” communications in a compact form factor enclosure (the front panel less than 5×6 inches). The unit controller is composed of two primary hardware elements: the controller module (single or redundant) and the palm type computers (P/PC)-based human-machine interface (HMI) with touch screen. The controller covers a wide span of applications, from single process unit control to networked multi-unit management.

Further results on variable output feedback controllers

Abstract: Zak and Hui (1993) proposed a sliding mode controller for linear multiple-input-multiple-output (MIMO) systems using static output feedback. The author's previous paper (1996) provides an improvement of the output feedback controller of Zak-Hui for a class of linear single-input-single-output (SISO) systems that eliminated two important limitations: 1) system uncertainties must be bounded by the system output; and 2) a requirement of a matrix inequality. The controller developed previously can guarantee global closed-loop stability. This paper extends the previous results to linear MIMO systems. It is emphasized that the proposed MIMO controller yields global closed-loop stability whereas the one in Zak-Hui can only guarantee local stability. An application of the proposed MIMO controller to an aircraft model is included to show the effectiveness of the method.

Nonlinear state feedback controller for nonlinear systems: Stability analysis and design based on fuzzy plant model

Abstract: This paper presents the stability analysis of a fuzzy-model-based control system consisting of a nonlinear plant and a nonlinear state feedback controller and the design of the nonlinear gains of the controller. The nonlinear plant is represented by a fuzzy model having p rules. A nonlinear state feedback controller is designed to close the feedback loop. Under this design, the stability condition is reduced to p linear matrix inequalities. An application example on stabilizing a mass-spring-damper system will be given.

Redundant controller data storage system having hot insertion system and method

Abstract: A redundant controller data storage system having a hot insertion system and method is described. In one aspect, the method of hot inserting a controller in a redundant controller system includes configuring a first controller to include a first memory, a task processor and a system operation processor. The first memory includes a first memory image. The redundant controller system is operated via the first controller. The system operation commands are processed via the system operation processor. A second controller including a second memory, is inserted into the redundant controller system. Background tasks are processed during the processing of system operation commands via the first controller using the task processor, including copying the first memory image to the second memory.

RF home automation system with replicable controllers

Abstract: The present invention relates to a wireless home automation system having controllers for controlling a broad variety of functions via two-way communication with a plurality of devices More specifically, the invention relates to sharing information related to the system between controllers, eg by updating a second controller with the newly learned information of a first controller, or by replicating a controller by making a second controller a complete copy of a first controller The information can be shared by generating and transmitting, with a first controller, a list of device identifiers of devices controlled by the first controller to a second controller The list is received by the second controller and stored in a memory of the second controller dedicated to store device identifiers of devices controlled by the second controller This function proves advantageous when new controllers are introduced or if a controller is lost, worn out, or destroyed

Modeling and controller design of an electromagnetic engine valve

Abstract: A control-oriented linear model was constructed for an electromagnetic camless valvetrain (EMCV) based on a gray-box approach that combines mathematical modeling and system identification. An inner-loop feedback stabilizing controller and a cycle-to-cycle repetitive learning feedforward controller were designed for the EMCV to meet the quiet-seating requirement. The performance of this control system is demonstrated by experimental results.

Steady-state model for VSC based HVDC and its controller design

Abstract: In this paper, a steady-state model of a VSC (voltage source converter) based HVDC system has been developed. According to this model, the corresponding relationship between the two controlling and the two controlled variables of the VSC is determined. Furthermore, a nonlinear control strategy combining an inverse model controller with a PI controller is proposed, and a nonlinear compensation method is adopted for the DC voltage PI controller. Digital simulation shows the validity of the established steady-state model and the feasibility of the proposed control strategy.

Model matching for finite-state machines

Abstract: The problem of model matching for finite state machines (FSMs) consists of finding a controller for a given open-loop system so that the resulting closed-loop system matches a desired input-output behavior. In this paper, a set of model matching problems is addressed: strong model matching (where the reference model and the plant are deterministic FSMs and the initial conditions are fixed), strong model matching with measurable disturbances (where disturbances are present in the plant), and strong model matching with nondeterministic reference model (where any behavior out of those in the reference model has to be matched by the closed-loop system). Necessary and sufficient conditions for the existence of controllers for all these problems are given. A characterization of all feasible control laws is derived and an efficient synthesis procedure is proposed. Further, the well-known supervisory control problem for discrete-event dynamical systems (DEDSs) formulated in its basic form is shown to be solvable as a strong model matching problem with measurable disturbances and nondeterministic reference model.

A method and apparatus for an active standby control system on a network

Abstract: A method and apparatus for providing an active standby control system comprising the steps of providing a first and second controller, each controller having an operating state. Each controller is operably connected to a network. Assigning a network identifier, i.e., Internet Protocol, Media Access Control address, etc., to each controller and sensing the operating state of each controller. The network identifier of each controller is determined by the operating state of each respective controller.

Robust PI controller design for nonlinear systems via fuzzy modelling approach

Abstract: The design problem of proportional and proportional-plus-integral (PI) controllers for nonlinear systems is studied. First, a Takagi-Sugeno fuzzy model with parameter uncertainties is used to approximate the nonlinear systems. Then a numerically tractable algorithm based on the technique of iterative linear matrix inequalities is developed to design a proportional (static output feedback) controller for the robust stabilization of the system in Takagi-Sugeno fuzzy model. Thirdly, we transform the problem of PI controller design to that of proportional controller design for an augmented system and thus bring the solution of the former problem into the configuration of the developed algorithm. Finally, the proposed method is applied to the design of robust stabilizing controllers for the excitation control of power systems. Simulation results show that the transient stability can be improved by using a fuzzy PI controller when large faults appear in the system, compared to the conventional PI controller designed by using a linearization method around the steady state.

Towards pronking with a hexapod robot

Abstract: : This paper presents a pronking controller for our six-legged robot RHex. Development of the controller begins with a passive-dynamics approach, ensuring that the robot is naturally suited to running. Running with flight phase is then achieved using only proprioceptive (joint angle sensing only) feedback for touchdown detection and for tracking fixed joint reference trajectories. Body pitch oscillation is attenuated by means of an open loop leg speed change during stance. The robot achieves speeds of about two body lengths per second with a specific resistance of 1.85.