Showing papers on "Open-loop controller published in 1986"

Internal model control: PID controller design

Abstract: For a large number of single input-single output (SISO) models typically used in the process industries, the Internal Model Control (IMC) design procedure is shown to lead to PID controllers, occaslonally augmented with a first-order lag. These PID controllers have as their only tuning parameter the closedloop time constant or, equivalently, the closed-loop bandwidth. On-line adjustments are therefore much simpler than for general PID controllers. As a special case, PIand PID-tuning rules for systems modeled by a first-order lag with dead time are derived analytically. The superiority of these rules in terms of both closed-loop performance and robustness is demonstrated.

Microcomputer Control of Switched Reluctance Motor

Abstract: A microcomputer-based four-quadrant control system of a switched reluctance motor is described. The control was implemented with a speed feedback loop, a torque feedback loop, and both the torque and speed feedback loops combined. In addition the controller incorporates a startup operation, sequencing, and synchronized angle steering control. The angle controller was designed using dedicated digital hardware, whereas the other functions were implemented using an Intel 8751 single-chip microcomputer. The complete control system was tested in the laboratory with a 5-hp drive, and the test results were found to be excellent.

Observability of discrete event systems

Abstract: Using a nondeterministic state model for a discrete event process the problem of determining the current state of the system from a sequence of past events and state observations is examined. Conditions under which it is possible to truck the state of the process with sufficient accuracy to implement a given feedback control are determined.

Tuning of Field-Oriented Induction Motor Controllers for High-Performance Applications

Abstract: A tuning procedure for high-performance (e.g., axis feed type) applications of feedforward field-oriented controllers is developed and demonstrated. The theoretical basis of the procedure is explained via a novel form of dq vector diagram. This diagram displays both steady and transient states simultaneously. This format also provides substantial insight into the expected behavior of mistuned controllers, especially for analyzing transient torque performance. The procedure is unambiguous to implement, and it requires no additional sensors beyond those required for the feedforward controller.

Adaptive control technique for a dynamic system

Abstract: A controller for a voice coil motor driven disk file actuator is described. The device has an online adjustable gain characteristic for controlling movement of the actuator assembly and an estimator that estimates actuator velocity and bias. Forward gain is estimated from position and coil current measurements and compared with a nominal value to create an error signal used to adjust the controller and estimator gain characteristics. The control technique allows changes in the open loop system without changing the closed loop performance. By monitoring loop gain it is possible to alter compensator gains to maintain a constant closed loop performance.

Method and apparatus for fault tolerant communication within a computing system

Abstract: A method and apparatus for fault tolerant communication among a plurality of I/O controllers and a communication controller using an I/O bus having byte-parallel and bit-serial data lines. Each controller is connected to the bit-serial and byte-parallel data lines and the CPU communication controller is capable of selectively indicating which set of lines shall be used for communicating information. When serial communication is desired, a switching signal is transmitted by the CPU communication controller on the serial data line whereupon the I/O controllers switch communication from the byte-parallel data lines to the bit-serial data line. Serial arbitration conflicts are avoided by allocating a time interval to each I/O controller. Each time interval is divided into 3-bit periods. An arbitrating I/O controller asserts the first itself bit true, asserts the second bit false, and disconnects from the bus during the third bit period to separate in time the modules connected to the bus from each other. The CPU communication controller in an operating system initializes newly-inserted modules and synchronizes unsynchronized modules by generating a signal on the bus for prescribed periods of time after which synchronizing control modules within each I/O controller synchronizes the I/O controller with the rest of the system.

Glassware forming apparatus with distributed control

Abstract: An improved electronic control system for glassware forming apparatus having a heirarchy of machine level supervisory controllers (including a machine controller and an operator communications controller), section controllers, and individual mechanism controllers. The mechanism controllers may be dedicated to the control of a variety of functions admitting of automated control, such as servo-control of electrical motors, sequencing of solenoid valves, generating alarm signals, etc. The mechanism controllers include separate control programs designed for their associated forming mechanisms, and are subject to on-off timing control in real time from the section level controllers. In general, the machine controller and operator I/O controller handle set-up, operator modifications during operation, and other "non-real-time"interactions with the mechanism controllers; the machine controller also coordinates the operation of a plurality of mechanism controllers in accordance with machine-level parameters.

Compact disc drive apparatus having an interface for transferring data and commands to and from a host controller

Abstract: A drive apparatus for an optical disc read system. An interface is provided to a host controller for reading out data on a compact disc. The read out data is converted from parallel to serial format, and transmitted with a clock stream to the host controller. Host controller commands are transmitted to the drive apparatus which recognizes the command as either allowable or non-allowable. The interface provides signalling to the host controller of drive error conditions, spin up/non-spin up conditions, and non-allowable command situations for the controller.

Design of Optimal Control Systems with Stable Feedback

Abstract: The problem of stabilizing a single-input single-output system using stable feedback is considered. The performance index that is minimized is the weighted sensitivity of the closed-loop system to external disturbances. However, the resulting feedback associated with the minimum value of the optimality criterion turns out to be irrational. A design algorithm has been developed to find an approximation whose deviation from a sub-optimal system lies within a pre-specified error bound.

Force-position-velocity control with self-tuning for robotic manipulators

Abstract: The force-path control of a robotic manipulator is presented here in the joint and in the Cartesian coordinate systems. An autoregressive model with external excitation (ARX-model) is introduced for designing an adaptive controller with self-tuning. The controller minimizes the conditional expectation of the sum of a quadratic position (velocity) error and a quadratic force error while satisfying the constraint of the ARX-model with the estimates substituted for the unknown parameters. The basic approach is used to obtain an adaptive controller which operates on the variables expressed in the joint coordinates. Another adaptive controller is similarly determined for the system variables of the Cartesian coordinate system. The adaptive controller for force-path control introduced here has the form similar to that of hybrid force/position controller of [5], but with time varying gains.

Open-loop brushless motor control system

Abstract: The speed command for an open-loop brushless motor speed control system is overridden whenever the speed of the motor is less than a relatively low reference speed in order to quickly accelerate the motor to a running speed, despite a relatively low speed command. In the event of a motor overcurrent condition, the override is itself overridden to protect the controller.

Feedforward Control Techniques to Achieve Fast Settling Time in Robots

Abstract: Robots experience vibration problems when commanded to perform rapid motions which excite system resonances. To reduce the time required to arrive and stop at the commanded position, both move time and settling time must be reduced. The control scheme presented in this paper is designed to achieve these objectives using a modified state-variable feedback controller. The conventional controller is modified with the addition of a suitably-shaped feedforward forcing function which is designed to minimize both move time and residual vibration amplitudes. This modified control system is described and performance evaluations are presented on a typical flexible dynamic system.

Design of tunable digital set-point tracking PID controllers for linear multivariable plants using step-response matrices

Abstract: It is shown that the proportional, integral, and derivative controller matrices embodied in tunable digital PID controllers for linear multivariable plants can be directly determined from open-loop tests performed on asymptotically stable plants, thus circumventing the need for mathematical models. The class of multivariable plants for which digital PID controllers are superior to digital PI controllers is identified, and the effectiveness of the resulting design methodology is illustrated by designing a tunable digital set-point tracking PID controller for a distillation column.

A Microcomputer-Based Self-Tuning IP Controller for DC Machines

Abstract: The problem of designing an adaptive controller for dc drives operating under varying load conditions is addressed. A robust self-tuning controller that can track a constant reference and reject constant load disturbances is developed. The controller is shown to have an adaptive integral-proportional (IP) structure. The proposed controller is implemented in a microcomputer and a dc motor is controlled under varying load and operating conditions. Experimental results show that the controller possesses excellent adaptation capability as well as transient recovery under load changes.

Design of an Adaptive Controller for Microcomputer Implementation

Abstract: A design procedure for an adaptive controller is described and applied to the design of a velocity controller for small dc motors. The basic concept has been to determine a small set of controllers each of which is capable of maintaining stability and acceptable performance over a specific region of motor load parameters. Optimal control theory is used to define the control coefficients while cluster analysis and decision function techniques from pattern recognition theory are used to determine each controller's region of applicability. Simulation results are presented to verify performance improvements using the design procedure. The design procedure produces an adaptive controller which is computationally feasible for implementation in small microcomputer systems.

Automated controller tuning for HVAC applications

Abstract: The application of a computer-assisted controller tuning program, an automatic tuning controller, and a self-tuning controller to heating, ventilating, and air-conditioning (HVAC) processes is reported. Automated controller tuning addresses two fundamental problems in HVAC control applications: the time-consuming initial tuning of the controller and the requirement for periodic controller retuning as system loads change. The tuning methods described in this paper rely on the estimation of a process model for calculating proportional-integral (PI) control parameters. An evolutionary approach in the development of automated tuning methods allows the transfer of valuable experience.

Linking system for programmable controller

Abstract: In a programmable controller linking system, a plurality of programmable controllers PC1,PC2 ...PCN are connected to one master controller MC and sequences of the programmable controllers are programmed in used of addresses representing optional input/output memory areas MA1 to MAN. Link tables are prepared by automatically alotting input/output memory areas MA1 to MAN of the programmable controllers PC1,PC2,...PCN, to the inner relays, with respect to addresses of the respective programmable controllers PC1,PC2...PCN except for the subject programmable controller,the thus prepared link tables 2 are registered in the master controller MC, and all the link tables are coilected from the respective programmable controllers in the master controller MC at the link starting time to prepare an editorial link table by collecting common portions of the collected link tables. The input/output side address tables are provided for the master controller MC and the respective programmable controllers, respectively, so that the data is periodically accessed and linked between the master controller MC and the respective programmable controllers in accordance with the input/output side address tables.

Improvement in Arterial Oxygen Control using Multiple Model Adaptive Control Procedures

Abstract: A computer-based proportional-integral (PI) controller has been developed to control arterial oxygen levels in mechanically-ventilated animals. Arterial oxygen saturation is monitored using a non-invasive oximeter and control is effected by adjusting inspired oxygen fraction. The performance of the feedback system is sensitive to the open-loop gain so that the desired transient specifications can only be achieved by empirical adjustment of a PI controller. Because the open-loop gain includes the animal's response, it may vary with time and with the administration of positive end-expiratory pressure. Multiple model adaptive control procedures were therefore used to desensitize the system to these gain variables. Computer simulations demonstrated the effectiveness of the algorithm over a wide variation of plant parameters. A comparison with a fixed well-tuned proportional-integral controller showed an improvement in the regulatory response to a step disturbance. Animal experiments reiterated the feasibility of using multiple model adaptive control procedures in arterial oxygen saturation regulation.

Solid state electronic irrigation controller

Abstract: A solid state electronic controller for electrically-operated water sprinkler valves in an irrigation system. The controller is constructed to control a number of different water sprinkler valves in each of a number of different watering zones, for successive time intervals at one or more preset time periods during each day of the week. The controller includes a liquid crystal display which exhibits instruction words and numbers to facilitate the programming of the controller, for monitoring the operation of the controller, and also for exhibiting malfunctions in the system.

Multivariable adaptive controller for a turbogenerator

Abstract: The paper describes the design and application of an adaptive controller which overcomes the nonlinearity of the turbogenerator system. The controller tracks the operating conditions and updates an optimal controller as conditions change. Modelling of the turbogenerator employs an output prediction equation and recursive least-squares algorithm. The design uses identified input/output models, obtained over a range of operating conditions in the PQ-plane. Optimal controllers are designed offline for each zone of the PQ-plane and stored in online memory as a look-up table. The computer monitors the operating conditions of the generator and selects the corresponding optimal controller. The paper presents a practical comparison between the fixed-gain and the look-up-table controllers over a wide range of operating conditions, with various fault conditions, including transient stability boundaries of each controller. The results show that a very high quality of control may be achieved using this adaptive controller.

Parametric State Feedback Control with Response Insensitivity

Abstract: A recent parameterization of the class of linear feedback controllers which assign a set of desired self-conjugate eigenvalues to the closed-loop system is used to formulate and solve a fundamental response insensitivity problem It is established to what extent state feedback control can be used to render the closed-loop system response insensitive to possibly many not necessarily small parameter variations in the open-loop state-space model A nonconservative sequential design procedure is developed for making as many of the closed-loop system eigenmodes as possible totally insensitive while retaining arbitrary assignment of the maximum number of closed-loop eigenvalues The main result is a class of desensitizing fixed gain state feedback controllers explicitly specified by a set of free parameters which may be chosen to satisfy additional design requirements

Towards robust adaptive control with extended predictive control

Abstract: A robust version of the self-tuning controller was developed by extending the prediction horizon and using a set of successive prediction values in a multistep cost index.

Nonlinear Heat Exchanger Control through the Use of Partially Linearized Control Variables

Abstract: The use of partial linearization by nonlinear state variable feedback has been proposed as a means of reducing the detrimental effects of severe system nonlinearities upon the performance of linear control schemes used with severely nonlinear systems. In this paper a set of generalized transformed variables are derived for a single pass shell and tube heat exchanger using this technique. The implementation of these generalized transformed variables, which reduce the apparent nonlinear behavior of single pass heat exchangers, eliminates the need to rederive a nonlinear transformation for each heat exchanger control design. The open loop behavior of the system is examined in the time domain to evaluate the ability of the transformed variables to reduce the asymmetry of system response to changes to system inputs. The closed loop performance of the chosen system is evaluated for both servo and regulator control. Finally, the effect of model error upon the robustness of the closed loop controller performance is examined.

Adaptive PI dead-beat controller for motor vehicles

Abstract: A method for controlling process variables is presented in which an adaptive discrete PI dead-beat controller is used. The dead-beat controller is supplemented by an adaption block which automatically follows the control parameters. In this way, the control circuit behaves according to its design under all operating conditions. The adaption block comprises essentially a Kalman filter and an identification algorithm. The control behaviour is particularly suitable for travel speed controllers or idling speed controllers in motor vehicles.

Experiments on manipulator gross motion using self-tuning controller and visual information

Abstract: A picture of a scene is used to extract information for an adaptive control algorithm. The object of interest is first located by means of a classifier. The position and orientation of the object are determined from a binary picture. The desired path that the gripper of the manipulator is to follow is specified by discrete points, first in the Cartesian and then in the joint coordinate system. The adaptive self-tuning controller is outlined. The controller design is based on a time series difference equation model in which the parameters are estimated on-line. The gains of the controller are tuned so that a quadratic performance criterion is minimized. The performance of the system designed is then tested experimentally, and the results are presented.