Showing papers on "Open-loop controller published in 1995"

Linear and nonlinear controller design for robust automatic steering

Abstract: For an automatic steering problem of a city bus the reference maneuvers and specifications are introduced. The robustness problem arises from large variations in velocity, mass, and road-tire contact. Two controller structures, both with feedback of the lateral displacement and the yaw rate, are introduced: a linear controller and a nonlinear controller. The controller parameters are first hand-tuned and then refined by performance vector optimization. Both controllers meet all specifications. Their relative merits are analyzed in simulations for four typical driving maneuvers. >

A fuzzy logic controller for an ABS braking system

Abstract: Anti-blocking system (ABS) brake controllers pose unique challenges to the designer: a) For optimal performance, the controller must operate at an unstable equilibrium point, b) Depending on road conditions, the maximum braking torque may vary over a wide range, c) The tire slippage measurement signal, crucial for controller performance, is both highly uncertain and noisy, d) On rough roads, the tire slip ratio varies widely and rapidly due to tire bouncing, and e) The braking system contains transportation delays which limit the control system bandwidth. A digital controller design was chosen which combines a fuzzy logic element and a decision logic network. The controller identifies the current road condition and generates a command braking pressure signal, based on current and past readings of the slip ratio and brake pressure. The controller detects wheel blockage immediately and avoids excessive slipping. The ABS system performance is examined on a quarter vehicle model with nonlinear elastic suspension. The parallelity of the fuzzy logic evaluation process ensures rapid computation of the controller output signal, requiring less time and fewer computation steps than controllers with adaptive identification. The robustness of the braking system is investigated on rough roads and in the presence of large measurement noise. This paper describes design criteria, and the decision and rule structure of the control system. The simulation results present the system's performance on various road types and under rapidly changing road conditions.

Robust Dynamic Inversion for Control of Highly Maneuverable Aircraft

Abstract: This paper presents a methodology for the design of flight controllers for aircraft operating over large ranges of angle of attack. The methodology is a combination of dynamic inversion and structured singular value (p) synthesis. An inner-loop controller, designed by dynamic inversion, is used to linearize the aircraft dynamics. This inner-loop controller lacks guaranteed robustness to uncertainties in the system model and the measurements; therefore, a robust, linear outer-loop controller is designed using /i synthesis. This controller minimizes the weighted HQO norm of the error between the aircraft response and the specified handling quality model while maximizing robustness to model uncertainties and sensor noise. The methodology is applied to the design of a pitch rate command system for longitudinal control of a high-performance aircraft. Nonlinear simulations demonstrate that the controller satisfies handling quality requirements, provides good tracking of pilot inputs, and exhibits excellent robustness over a wide range of angles of attack and Mach number. The linear controller requires no scheduling with flight conditions. HE objective of this paper is to present a method for design of flight controllers that provides desired handling qualities over a wide range of flight conditions with minimal scheduling. Acceptable stability and performance robustness must be maintained in the presence of unmodeled dynamics, uncertainties in the aircraft design model, and noisy sensor measurements. The aircraft considered in this paper is the NASA high angle-ofattack research vehicle (HARV), which is typical of future fighter aircraft. It is capable of flight at very high angles of attack and has thrust vectoring as well as conventional aerodynamic control surfaces.1 The unaugmented aircraft does not meet handling quality requirements and some type of augmentation is necessary. This paper considers only the longitudinal control. The controller relates pilot longitudinal stick input to the symmetric deflection of the stabilizer and the longitudinal deflection of the thrust vectoring vanes. The control design philosophy is to use an inner-loop, dynamic inversion controller and an outer-loop, linear \JL controller. The dynamic inversion controller linearizes the pitch rate dynamics of the aircraft; however, since model uncertainties prevent exact linearization, there will always be errors associated with this controller. A simple linear fractional transformation model of these errors is developed for use in design of the outer-loop /^ controller. This controller provides pitch rate following by minimizing the weighted //oo-norm of the difference between the actual aircraft pitch rate response to pilot stick inputs and the desired response to these inputs as given by a transfer function model based on standard handling quality specifications. Thus the outer-loop \Ji controller is an implicit model following design, which provides robustness to errors due to the lack of exact cancellation of the pitch rate dynamics by the dynamic inversion controller. Recently a number of papers have appeared that describe controllers for a highly maneuverable aircraft. In Refs. 2-5, application of linear multi-input/multi-output (MIMO) control design techniques to this problem were presented. In every case, excellent

Robust SVC controller design for improving power system damping

Abstract: The design of a robust controller for a static VAr compensator (SVC) to improve the damping of a power system is presented. The main contributions of the paper are to formulate and to solve the power system damping control problem using robust optimization techniques, and to synthesize the controller with explicit consideration of the system operating condition variations. Nonlinear simulations using the PSCAD/EMTDC software packages have been conducted to evaluate the performance of the closed-loop system. The results have indicated that the designed controller can provide positive damping to the system under a wide range of operating conditions.

Fuzzy learning control for a flexible-link robot

Abstract: There are two main drawbacks in fuzzy control: 1) the design of fuzzy controllers is usually performed in an ad hoc manner where it is often difficult to choose some of the controller parameters; and 2) the fuzzy controller constructed for the nominal plant may later perform inadequately if significant and unpredictable plant parameter variations occur. In this paper we illustrate these two problems on a two-link flexible robot testbed by: 1) developing, implementing, and evaluating a fuzzy controller for the robotic mechanism, and 2) illustrating that payload variations can have negative effects on the performance of a well designed fuzzy control system. Next, we show how to develop and implement a fuzzy model reference learning controller for the flexible robot and illustrate that it can automatically synthesize a rule-base for a fuzzy controller that will achieve comparable performance to the case where it was manually constructed, and automatically tune the fuzzy controller so that it can adapt to variations in the payload. >

Game machine controller

Abstract: A game machine controller with keys controls the movement of an image subject displayed on a monitor screen in an X- and a Y-axis direction. A first and a second controller section are coupled to each other by a coupling member. Relative displacement information of the first and second controller sections with respect to the coupling member is detected. The movement of the image subject in a Z-axis direction is controlled based on the detected displacement information.

Application of fuzzy controller to automatic generation control

Abstract: This paper describes an application of fuzzy logic to design a fuzzy controller for the automatic generation control (AGC) problem in power system studies. A two area power system is considered. Frequency and tie-line power deviations for a step load increase in one area are plotted as a function of time, and are compared with available responses using the classical integral controller

Multivariable nonlinear process controller

Abstract: A method and apparatus for a robust process control system that utilizes a neural-network multivariable inner-loop PD controller cascaded with decoupled outer-loop controllers with integral action, the combination providing a multivariable nonlinear PID and feedforward controller. The inner-loop neural-network controller is trained to achieve optimal performance behavior when future process behavior repeats the training experience. The outer-loop controllers compensate for process changes, unmeasured disturbances, and modeling errors. In the first and second embodiments, the neural network is used as an inner-loop controller in a process control system having a constraint management scheme which prevents integral windup by controlling the action of the outer-loop controllers when limiting is detected in the associated manipulated-variable control path. In the second and third embodiments, the neural-network controller is used without the integral controllers or the constraint management scheme as a simple PD feedforward controller.

Robust time-delay control of multimode systems

Abstract: This paper presents a procedure for the design of open loop controllers for flexible structures using multiple step inputs delayed in time The controller attenuates the residual vibration by cancelling the complex poles of the system Robustness is achieved by locating additional zeros at the cancelled poles of the system The paper begins by addressing the control of a single mode and examines the effect of user selected time-delays on robustness and the reference input Next, a procedure for the design of robust time-delay controllers for multiple modes with user selected time-delays is considered This is followed by a design of a minimum time-delay controller, such that the step input magnitudes are constrained to values between 0 and 1 Two examples, a spring-mass system and a single-link flexible-arm robot are used to illustrate the effectiveness of the proposed controller

State of the art of controlled AC drives without speed sensor

Abstract: The operation of speed controlled AC motor drives without mechanical speed or position sensors requires the estimation of internal state variables of the machine. The assessment is based exclusively on measured terminal voltages and currents. Low cost, medium performance sensorless drives can be designed using simple algebraic speed estimators. High-performance systems rely on dynamic models for the estimation of the magnitude and spatial orientation of magnetic flux waves in the stator or in the rotor. Open loop estimators and closed loop observers differ with respect to accuracy, robustness, and limits of applicability. The overview in this paper uses signal flow graphs of complex space vector quantities to give an insightful description of the physical and mathematical systems used in sensorless control. >

CMAC neural network controller for fuel-injection systems

Abstract: A new automotive fuel-injection controller using the cerebellar model articulation controller (CMAC) neural network is developed and implemented to maintain the engine air-to-fuel ratio at its stoichiometric value. The CMAC controller requires minimal a priori knowledge of the engine dynamics because it can learn the dynamics and adapt to changing conditions in real time. The CMAC controller is experimentally evaluated on a research vehicle in a configuration fully compatible with production hardware. Initial training followed by continual adaptation allows the CMAC controller to maintain desired performance under previously inexperienced driving conditions. >

Robust controller design for generator excitation systems

Abstract: This paper deals with the design and evaluation of a robust controller for generator excitation systems to improve the steady-state and transient stabilities. The unique approach used is to first treat the nonlinear characteristics of the system as model uncertainties, and then to take into account such uncertainties at the controller design stage using a robust control methodology. The performance of the controller has been evaluated extensively by nonlinear simulation. It is concluded that the robust controller provides better damping to the oscillatory modes of the system than the conventional PSS in all the cases studied. >

Flexible process controller

Abstract: A flexible process controller for coordinating the operations of various equipment is disclosed. Briefly stated, in the preferred embodiment of the present invention, various parameters of the sub-systems in a HVAC system are monitored and made alterable or changeable. These parameters are transmitted to and controlled by a flexible process controller which thereafter cooperates with a motor drive controller. Logic incident to and resident in the flexible process controller consider the various parameters monitored and allow the user or the system to minimize power consumption amongst one or more of the sub-systems while maximizing efficiency and operability.

Covariance control design for Hubble Space Telescope

Abstract: To improve the response to unexpected thermally induced disturbances, two new controllers are designed for the Hubble Space Telescope (HST) using covariance control techniques. The first controller minimizes the required control effort subject to inequality constraints on the output covariance matrix. The second controller is designed to satisfy both output covariance constraints and controller covariance constraints. The importance of the controller covariance constraint is to properly scale the controller for digital implementation in the control computer using fixed-point arithmetic. We provide a technique to integrate modeling, control design, and signal processing (in HST's fixed-point control computer), since these problems are not separable. Covariance control can easily accommodate the roundoff error and computational time delay. Compared with the existing HST controller design, the results show that the required pointing error specifications can be achieved with 85% less control effort and that the error due to the finite-wordlength implementation of the controller can easily be included in the optimal control design process.

A tracking controller for flexible joint robots using only link position feedback

Abstract: A dynamic output feedback controller for flexible joint robots is presented which guarantees asymptotic tracking of a desired trajectory, starting from arbitrary initial conditions. The controller needs only the measurements of the positions of the links and the knowledge of an upper bound on the initial tracking error. >

Self-optimizing detergent controller for controlling variable additive concentration level in a warewashing machine

Abstract: An apparatus and method for programming a controller to vary the concentration set-point of an additive as a function of time. The present invention insures that the additive is injected to the machine at proper times to allow for optimum efficiency and lowest cost. To vary the set-point according to the input parameters, the invention combines the features of a data entry device, a microprocessor, a clock, a controller, and sensors into one unit. The user may enter a time setting and set point into the controller, along with control parameters which allow the machine to control the additive injection based on different user-defined scenarios. The microprocessor then reads the settings and outputs an appropriate set-point value from the microprocessor to the controller. Thus, the user can manually or automatically change the response function if and when conditions change.

Receiver, automatic gain controller suitable for the receiver, control signal generator suitable for the automatic gain controller, reception power controller using the automatic gain controller and communication method using the receiver

Abstract: A receiver, an automatic gain controller suitable for the receiver, a control signal generator suitable for the automatic gain controller, a reception power controller using the automatic gain controller and a communication method using the receiver. The instantaneous power of a received signal output from a variable gain amplifier or attenuator is detected by a power detector. The detected instantaneous power is quantized by a comparator and filtered through a random walk filter. An up-down counter counts up or down in accordance with the increment signal or the decrement signal obtained by filtering. In this manner, error in the gain control of the variable gain amplifier or attenuator is obtained.

Video game controller for use with an exercise apparatus

Abstract: A video game controller for use with an exercise apparatus. The controller includes a gross motion sensor which is activated by the palm of the user's hand when the user's wrist is rotated. In this way, a "steering" input can be sensed by the controller and forwarded to the video game. The controller further includes a pair of "action" switches which may be conveniently activated by the user's fingers. The controller may be formed as an integral part of the exercise apparatus handle or as a separate member designed for convenient attachment to the handle in a retrofit application.

A desensitized controller for voltage regulation of power systems

Abstract: In this paper, a robust linear voltage controller is proposed to improve power system stability and performance under varying operating conditions. This controller includes an automatic voltage regulator and power system stabilizer. It limits the variations of the terminal voltage, damps electromechanical oscillations and increases the excitation during and after a short circuit in all operating points. The design method chosen to improve the parametric robustness is desensitivity. It is the first time that a parametric robust design method has been applied to resolve the problem of voltage regulation. The method's principles, when the parameter is a vector, are presented. The desensitized controller has a simple structure and therefore can easily be implemented. The results obtained with simulation software and with the Electricite de France Transient Network Analyser show the good performance and the advantages of the controller with respect to various disturbances. This method can be applied to ail kinds of generators, and is particularly well suited in the case of turbogenerators working under very different operating conditions. >

Robust current controller for three-phase inverter using finite-state automaton

Abstract: A novel feedback current controller for a three-phase load driven by a power inverter is proposed. The main design specifications are robustness to load electrical parameters, fast dynamical response, reduced switching frequency, and simple hardware implementation. To meet previous specifications a multi-variable hysteresis type controller is proposed, designed as a finite-state automaton and implemented with a programmable logic device. After a general introduction, system analysis is performed, control targets are specified, and the proposed control strategy is presented and discussed. Further, actual controller architecture, based on simple analog-logic hardware, is shown and experimental results are presented using an induction motor as the inverter load. However, this does not limit the wider applicability of the proposed controller that is suitable for different types of three-phase AC loads. >

Method and apparatus for storing and restoring controller configuration information in a data communication system

Abstract: A data communications system (100) has a controller (214) for managing the system containing a plurality of data communications devices (224). The data communication devices (224) have memory allocated for storing controller configuration information in order to serve as distributed controller backup units (226). If the controller (214) is replaced by a replacement controller (228), the controller configuration information is restored to the replacement controller (228) which receives the controller configuration information previously stored in the memory of the data communication devices serving as distributed controller backup units. The controller configuration information is stored in a page format (390) having identification (391), controller configuration information data (392), and error detection information (393).

Electric vehicle chassis controller

Abstract: A vehicle power controller for a vehicle including a motor that drives the vehicle, a plurality of sensors and a motor controller, wherein the plurality of sensors includes an accelerator sensor for sensing a position of an accelerator pedal and a brake sensor for sensing a position of a brake pedal, and wherein the motor controller controls torque output of the motor. The vehicle power controller includes three components. The first receives signals from the accelerator sensor and the brake sensor. The second converts the signals for the accelerator sensor and the brake sensor into a torque value, and the third outputs the torque value to the motor controller for controlling the torque output of the motor.

Fuzzy two-degrees-of-freedom speed controller for motor drives

Abstract: A fuzzy two-degrees-of-freedom (2-DOF) controller and its application to the speed control of an induction motor drive are presented in this paper. The proposed controller is composed of two fuzzy controllers to obtain good tracking and regulating responses. Unlike the conventional fuzzy controller, the error between the outputs of a reference model and the controlled drive is used to drive the proposed fuzzy controller. The drive rotor speed response can closely follow the trajectory produced by the reference model, and good load speed regulating response can also be obtained simultaneously owing to the possession of two-degrees-of-freedom in structure. Moreover, these performances are rather insensitive to the operating condition changes. The dynamic signal analysis as well as the construction of fuzzy control algorithms are described in detail. Some simulated and measured results are provided to demonstrate the effectiveness of the proposed fuzzy controller. >