Design Of Automatic Control System Research Articles

Logic and the engineer

Present-day electrical engineers make frequent use of the concepts of logic in the design and operation of computers and automatic control systems. Some of these ideas date back more than 2000 years, when logic was concerned with ideas expressed in words. In the 19th century, mathematicians found it possible to work out logical problems by means of algebra. A new look was given to the subject in the 20th century with the use of electical circuitry to perform logic operations.

Application of Dynamic Programming to Automatic Control System Design

Application of Dynamic Programming to Automatic Control System Design

An Automatic Gas-Flow Control System Adaptable to Gas Field Production

Abstract Pan American Petroleum Corp. has installed a field wide automatic gas-flow control system which automatically maintains and transfers to the pipeline a volume of gas equal to the purchaser's demand. The system controls production from 32 gas completions in the South and Little Pecan Lake fields in Cameron Parish of Southwest Louisiana. The system is sufficiently flexible so that total field flow-rate changes or individual well flow-rate changes can be made fro in the master control station by the operator. All communication for the system is over a buried electrical multi-conductor cable. Sufficient data feedback and printout are available so that the entire field operation can be policed from the master control station.As a result of the installation, field operational attendance has been reduced from 24 hours/day to 8 hours/day. Other expense-saving and income-generating advantages resulted from the installation. Introduction The ever increasing operating costs necessary to produce liquid hydrocarbons and natural gas, and to deliver these commodities to pipelines have been a prime concern of producing companies in recent years. Much progress has been made in reducing operating expenses in the area of liquid hydrocarbon production and delivery. This has been accomplished by using new equipment and techniques and by installing automatic flow, test and delivery control systems. Progress made in the area of natural gas production and delivery has lagged behind the cost-reducing advances made in liquid production and delivery. New equipment and techniques have aided in the reduction of gas field producing expense. However, until recently few strides have been made in the design and installation of automatic flow control systems which will release operating personnel from time-consuming routine duties and thus enable them to perform more productive work.As another step in the necessary trend toward automation for operating cost production Pan American Petroleum Corp. recently installed an automatic gas-flow control system in the South and Little Pecan Lake fields of Southwest Louisiana. In these two natural gas fields, the production and delivery of gas have been made more dependable while operating expenses have been reduced as a result of this installation. The geographical location of the South and Little Pecan Lake fields is shown in Fig. 1. The location of the gas wells, canals and associated sites of importance within the field areas is illustrated in Fig. 2. These two fields are approximately 6 miles from the Gulf of Mexico, and the terrain is low, water-covered marshland, except for occasional elevated areas. Field Operation Before Automation The base from which all field operations are conducted is Tank Battery Island. This point is shown on Fig. 2. This site is centrally located in the two-field area and is accessible by automobile over a 6-mile lease road. Except for the production equipment installed at Tank Battery Island, all facilities in the two fields including the gas wells, separation and metering equipment, tank batteries and a dehydration-hydrocarbon recovery unit are accessible only by boat via the canal network. This network, which is illustrated by Fig. 2, comprises over 20 miles of man-made waterways. JPT P. 253^

Rapid Methods for the Solution of Automatic Control Equations

In automatic control and other branches of engineering it is frequently necessary to find the roots of an algebraic equation. One of the authors has presented iteration methods for solving for both real and complex roots by right-to-left synthetic division. These methods are convergent for many, but not all, classes of roots. This paper presents a study of the convergence of the methods and extends the methods to cover the regions of nonconvergence. In addition, an improved array is presented for checking the Routh-Hurwitz stability criterion. The use of the methods in analysis and design of automatic control systems is demonstrated by numerical examples.

Design of automatic control systems for the process industry

Abstract

Development of a Variable Control Feel Simulator

Operational achievements and trends which influenced the design of aircraft manual and automatic flight control systems are briefly reviewed. The general features of current designs are presented, and the importance of control feel as a design parameter is cited. Present day experimental methods pertaining to aircraft control feel characteristics are noted, and indicated needs in this area of research are defined. Equipment developed to meet these needs is described and its first application is discussed.

Electronic simulation and computer techniques in the design of automatic control systems

Computing techniques for the development of aircraft automatic control systems are described which commence with a completely theoretical investigation on an analogue computer, thence by the introduction of more and more actual components to a complete simulator. Preliminary component specifications are ascertained for any given overall system characteristics. The testing of components which have been developed for use in the actual system is carried out to check the final characteristics of the system. Techniques which have been developed for the inclusion of complex mechanical loads in such simulators, and also the part played by the human operator in a control system are described. The idea of a computer which is capable of automatically setting its own coefficients (i.e. system parameters) so as to give an optimized overall system response is discussed briefly.

The Information to be Displayed on an Automatic System in the Air

The paper outlines some of the factors to be considered in the design of any complete airborne automatic navigation and control system. It is pointed out that such a system should lower the work-load on the pilot or navigator as well as contributing to flight safety. Modern engineering techniques have produced a wide range of navigation devices, and their safe and economical use in a complete system involves the consideration of a control loop including the displays and the human navigator. The paper examines this navigation loop in some detail. Some simple and some more complex methods of securing safe operation are suggested.

Multi-loop automatic temperature control system design for fluid dynamics facility having several long transport delays

This paper describes the systems analysis and design of an automatic temperature control system in the world's largest fluid dynamics testing complex consuming 470 megawatts of drive power. The plant treated in this paper can be described mathematically as a 110th order system having 130 feedback loops. Facility component characteristics are mostly non-linear, with prominent distributed parameters and ten long, variable fluid transport delay times. Important simplifications introduced to make the analysis and design work tractable include: (a) Application of the mathematical analogy between the theory of electric transmission lines and gas flow to validate the separation of temperature and pressure variations, (b) Selection of control frequency to permit lumped-parameter representation, (c) Design and construction of special computer devices and circuitry to simulate transport delays from 0.2 to 141 seconds in length. These valid simplifications reduce the plant to a 14th order system having about 50 feedback loops. The simplified system is simulated on an analog computer for economical synthesis and design of the controllers.

The Behaviour of Linear Systems with Inputs satisfying certain Bounding Conditions†

ABSTRACT Linear filters with bounded inputs give outputs which arc also bounded. A method is described for obtaining the least upper bound of the output for the case whore bounds are specified both for the magnitude of the input and its rate of change. The result, which is obtained in the form of a procedure for constructing that input (satisfying the bounding conditions) which gives riso to the largest output, has applications in the design of automatic control systems.

Design and Operation of Automatic Temperature Control Systems of Vinyl-Chloride Auto-Claves

Design and Operation of Automatic Temperature Control Systems of Vinyl-Chloride Auto-Claves

The transfer function of a steadily diverging reactor

In the design of automatic control systems which operate a diverging reactor, e.g. automatic start-up systems, a knowledge of the transfer function of the recctor is required. General expressions for the gain and phase shift of a steadily diverging reactor as functions of frequency are derived. Numerical values have been computed for a reactor with six groups of 235U delayed neutrons. “Doubling times” of 1, 5 and 20 sec and mean neutron lifetimes of 10 −3, 10 −4 and 10 −6 sec have been considered and results for these values are shown graphically. The results show that the transfer function of a diverging reactor is significantly different from that of a reactor in the steady state. The differences are of such a nature as to decrease the phase and gain margins of stability of the control system. The additional stability margins required can be found from the graphs.

Predictor Control Optimalizes Control-System Performance

Abstract A new technique for the design of automatic-control systems with nearly optimum transient response has been developed. The fundamental concept in the new method is that the control or forcing of the output member must be performed in such a manner that the error or deviation and its derivatives should be reduced to zero in three steps for third and higher-order systems. These three steps consist of a single period of maximum corrective action which forces the controlled variable in the direction of decreasing error or deviation, a single period of maximum corrective action in the opposite sense to decelerate the controlled variable, and finally a force-free period at the end of which the error and its derivatives simultaneously go to zero. In the practical embodiment of this mode of control a proportional control action exists during the final phase. During this proportional control period, the controller corrects any errors introduced by the instrumentation during the initial phases. In addition to the superior transient performance, a predictor-control system has the advantage that its response is not affected by variations in gain, if the gain is sufficiently large, and that the allowable gain in the proportional region is considerably in excess of that permitted in conventional linear-type systems. As a result, the steady-state accuracy which can be obtained is not dependent on a critical gain setting and the system response and accuracy are not degraded by the incorporation of variable gain elements.

Combination Open-Cycle Closed-Cycle Systems

The ancient idea of a combination coarse and fine adjustment is shown to be applicable to the design of precision automatic control systems. In the particular class of systems discussed, the coarse adjustment is taken to be a separate element operated by the input, but outside the feedback loop. Its position outside the feedback loop qualifies the coarse controller as an open-cycle system, and makes it possible to introduce such elements without affecting the system's transient response adversely. In this way, interference equalization of dynamical distortion errors is possible without such critical dependence being placed on a knowledge of series elements of the system as is required for interference equalization by a controller in the feedback loop. Three broad types of open-cycle systems are discussed: series, parallel, and partially parallel. Each of these may be algebraic, differential, or a combination. The algebraic controllers are useful when the average value of the input signal is predictable-particularly where a repetitive duty cycle is encountered. The advantages of adding completely parallel open-cycle elements for improving speed range and reducing over-all cost are shown. Idea is also applicable to nonlinear and multiplicoupled systems.

Some Design Criteria for Automatic Controls

The design of automatic control systems to give ``optimum'' response is discussed in terms of the area between a step disturbance and the control response. It is shown that this ``control area'', and also a ``weighted control area'' may be calculated directly from the system parameters without finding the roots of an algebraic equation. Assumed optimum values of these areas permit direct synthesis of the necessary control sensitivities for an ``optimum'' control response. An example of an aircraft engine control is given and the connection with zero velocity error servos is shown.

Some design criteria for automatic controls

The design of automatic control systems to give ``optimum'' response is discussed in terms of the area between a step disturbance and the control response. It is shown that this ``control area'', and also a ``weighted control area'' may be calculated directly from the system parameters without finding the roots of an algebraic equation. Assumed optimum values of these areas permit direct synthesis of the necessary control sensitivities for an ``optimum'' control response. An example of an aircraft engine control is given and the connection with zero velocity error servos is shown.