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Showing papers on "Control theory published in 1976"


Journal ArticleDOI
TL;DR: The Internal Model Principle is extended to weakly nonlinear systems subjected to step disturbances and reference signals and is shown that, in the frequency domain, the purpose of the internal model is to supply closed loop transmission zeros which cancel the unstable poles of the disturbance andreference signals.

2,613 citations


Journal ArticleDOI
TL;DR: In this paper, a least-square Wiener-Hopf minimization of an appropriately chosen cost functional is proposed to obtain an asymptotically stable and dynamical closed-loop configuration irrespective of whether the plant is proper, stable, or minimum phase.
Abstract: In many modern-day control problems encountered in the fluid, petroleum, power, gas and paper industries, cross coupling (interaction) between controlled and manipulated variables can be so severe that any attempt to employ single-loop controllers results in unacceptable performance. In all these situations, any workable control strategy most take into account the true multivariable nature of the plant and address itself directly to the design of a compatible multivariable controller. Any practical design technique most be able to cope with load disturbance, plant saturation, measurement noise, process lag, sensitivity and also incorporate suitable criteria delimiting transient behavior and steady-state performance. These difficulties, when compounded by the fact that many plants (such as chemical reactors) are inherently open-loop unstable have hindered the development of an inclusive frequency-domain analytic design methodology. However, a solution based on a least-square Wiener-Hopf minimization of an appropriately chosen cost functional is now available. The optimal controller obtained by this method guarantees an asymptotically stable and dynamical closed-loop configuration irrespective of whether or not the plant is proper, stable, or minimum-phase and also permits the stability margin of the optimal design to be ascertained in advance. The main purpose of this paper is to lay bare the physical assumptions underlying the choice of model and to present an explicit formula for the optimal controller.

1,276 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that there is a robust controller for a linear, time-invariant, multivariable system (plant) that asymptotic tracking/regulation occurs independent of input disturbances and arbitrary perturbations in the plant parameters of the system.
Abstract: Necessary and sufficient conditions are found for there to exist a robust controller for a linear, time-invariant, multivariable system (plant) so that asymptotic tracking/regulation occurs independent of input disturbances and arbitrary perturbations in the plant parameters of the system. In this problem, the class of plant parameter perturbations allowed is quite large; in particular, any perturbations in the plant data are allowed as long as the resultant closed-loop system remains stable. A complete characterization of all such robust controllers is made. It is shown that any robust controller must consist of two devices 1) a servocompensator and 2) a stabilizing compensator. The servocompensator is a feedback compensator with error input consisting of a number of unstable subsystems (equal to the number of outputs to be regulated) with identical dynamics which depend on the disturbances and reference inputs to the system. The sorvocompensator is a compensator in its own right, quite distinct from an observer and corresponds to a generalization of the integral controller of classical control theory. The sole purpose of the stabilizing compensator is to stabilize the resultant system obtained by applying the servocompensator to the plant. It is shown that there exists a robust controller for "almost all" systems provided that the number of independent plant inputs is not less than the number of independent plant outputs to be regulated, and that the outputs to be regulated are contained in the measurable outputs of the system; if either of these two conditions is not satisfied, there exists no robust controller for the system.

1,199 citations


Journal ArticleDOI
TL;DR: Fuzzy algorithms based on linguistic rules describing the operator's control strategy are applied toControl of a warm water plant using fuzzy set theory.

299 citations


Journal ArticleDOI
TL;DR: In this article, a composite control system is designed to stabilize the inverted pendulum and swing the pendulum from the natural pendent position up to the inverted position, which is actually made.
Abstract: This paper relates to the design of a control system for a mechanical system which contains an unstable mode and to an experiment for demonstrating that the control theory may be applied to practical real systems. In this paper the object treated is the control of the pendulum-cart system, which has been studied by many control theorists and engineers as an inverted pendulum problem, and a composite control system is designed not only to stabilize the inverted pendulum but to swing the pendulum from the natural pendent position up to the inverted position, which is actually made. The experimental results are presented.

255 citations


Journal ArticleDOI
TL;DR: In this article, a path-dependent coordinate system for describing vehicle motion is defined, and the availability of motion quantities for control purposes is specified, and various designs, in which different types of compensation are employed, are evaluated in terms of specified requirements and attractive candidates are specified.
Abstract: Several facets of the automatic lateral control of individual ground vehicles are considered in detail. First, a path-dependent coordinate system for describing vehicle motion is defined, and the availability of motion quantities for control purposes is specified. Second, the lateral dynamics of a typical U.S. passenger sedan are empirically obtained and validated with data from full-scale studies. Third, various designs, in which different types of compensation are employed, are evaluated in terms of specified requirements and attractive candidates are specified. Finally, several controller designs were tested under full-scale conditions wherein a wire-reference configuration and a dual-mode test vehicle were employed. The latter was automatically steered on both straight and curving roads at speeds up to 35.8 m/s (80 mph). In one typical case, the maximum tracking error observed was 0.0635 m and occurred both when a sidewind was present and when the vehicle entered a curving section of roadway. Excellent lateral control-close tracking, good insensitivity to disturbance forces, and a comfortable ride-can be obtained using a relatively simple controller.

180 citations


Proceedings ArticleDOI
01 Jan 1976
TL;DR: In this article, the authors consider a class of dynamical systems subject to parameter and input uncertainty whose values range in a given compact set and deduce a feedback control that assures uniform asymptotic stability of the origin under all admissible uncertainties.
Abstract: We consider a class of dynamical systems subject to parameter and input uncertainty whose values range in a given compact set. Utilizing the philosophy of "worst case" design, we deduce a feedback control that assures uniform asymptotic (Lyapunov) stability of the origin under all admissible uncertainties.

138 citations


Patent
12 Jul 1976
TL;DR: In this article, the wall-jet principle is applied to a sensor electrode of an electrochemical cell such that a first potential level of the square wave voltage is used as a detecting potential and a second potential level is utilized as a cleaning potential.
Abstract: An electrochemical detector has an electrochemical thin-layer flow cell whose operation is based on the so-called wall-jet principle, in combination with a controller unit. The controller unit can apply a periodically changing voltage having a square wave voltage formation to a sensor electrode of the electrochemical cell such that a first potential level of the square wave functions as a detecting potential and a second potential level of the square wave functions as a cleaning potential.

134 citations


Journal ArticleDOI
TL;DR: In this paper, a decomposition-aggregation method is proposed to decompose a large linear system into a number of interconnected subsystems with decentralized (scalar) inputs or outputs, which can be used directly to construct asymptotic state estimators for large linear systems on the subsystem level.
Abstract: In this short paper we consider three closely related aspects of large-scale systems: decentralization, stabilization, and estimation. A method is proposed to decompose a large linear system into a number of interconnected subsystems with decentralized (scalar) inputs or outputs. The procedure is preliminary to the hierarchic stabilization and estimation of linear systems and is performed on the subsystem level A multilevel control scheme based upon the decomposition-aggregation method is developed for stabilization of input-decentralized linear systems. Local linear feedback controllers are used to stabilize each decoupled subsystem, while global linear feedback controllers are utilized to minimize the coupling effect among the subsystems. Systems stabilized by the method have a tolerance to a wide class of nonlinearities in subsystem coupling and high reliability with respect to structural perturbations. The proposed output-decentralization and stabilization schemes can be used directly to construct asymptotic state estimators for large linear systems on the subsystem level. The problem of dimensionality is resolved by constructing a number of low-order estimators, thus avoiding a design of a single estimator for the overall system.

106 citations


Patent
John E. Mosier1
31 Aug 1976
TL;DR: In this paper, a method and apparatus for simulating operation and control of a railway train having at least one locomotive in a locomotive set and a plurality of articulated cars is presented.
Abstract: A method and apparatus for simulating operation and control of a railway train having at least one locomotive in a locomotive set and a plurality of articulated cars. A simulator control station including a train speed control throttle and a train braking controller provides signals related to the degree of operation of the throttle and braking controller. Information relating to car consist, track profile and simulated train location for a predetermined section of track are provided together with data related to the simulated locomotive tractive effort and train braking. Coupling forces between each car throughout the extent of the train are calculated from the data and displayed at the simulator control station to enable a simulator control station operator to control the throttle and braking controller in response to the displayed coupling forces and thereby simulate operation and control of the train. Brake pressure distribution along the length of the train is also displayed.

99 citations


Journal ArticleDOI
TL;DR: In this article, a necessary and sufficient condition for feedback stabilization of neutral functional differential equations is presented. But this condition is not applicable to the case of nonconvex functions.
Abstract: In this paper, we prove a necessary and sufficient condition for feedback stabilization of neutral functional differential equations.

Proceedings ArticleDOI
01 Dec 1976
TL;DR: The load and frequency control of a three-area interconnected power system consisting of 9 synchronous machines and a minimum order robust decentralized controller which solves this problem, and also the general multi-area load and Frequency control problem, is obtained.
Abstract: The load and frequency control of a multi-area interconnected power system is studied. In this problem, the system is assumed to be subject to unknown constant disturbances, and it is desired to obtain, if possible, robust decentralized controllers so that the frequency and tieline/net-area power flow of the power system are regulated. The problem is solved by using some structural results recently obtained in decentralized control, in conjunction with a parameter optimization method which minimizes the dominant eigenvalue of the closed-loop system. A class of minimum order robust decentralized controllers which solves this general multi-area load and frequency control problem is obtained. Application of these results is then made to solve the load and frequency control problem for a power system consisting of nine synchronous machines (described by a 119th-order system). It is shown that the load and frequency controller obtained in this case is not likely to be significantly improved by using more complex controllers; in particular, it is shown that the conventional controller, used in regulating the net-area power flow of a system, is not likely to be significantly improved upon by using more complex controllers.

Book ChapterDOI
TL;DR: In this article, the authors discuss the problem of control of dynamic stochastic systems, where the performance index is taken as the expected value of a cost function and is to be minimized by a sequence of controls.
Abstract: Publisher Summary This chapter discusses the concepts and methods in stochastic control. In most control or multistage decision processes arising in engineering, economic, or biological systems, there are inherent uncertainties. These uncertainties prevent the exact determination of the effect of the controller's actions and deterministic control theory cannot be used. In many problems, the uncertainties that could arise in the system, as well as in the observations made on the system could be modeled as stochastic processes. These problems could be treated using stochastic control theory. The chapter discusses the problem of control of dynamic stochastic systems. The state of the type of system that is considered evolves according to the non-linear stochastic difference equations. The performance index is taken as the expected value of a cost function and is to be minimized by a sequence of controls. The choice of these controls, which is a multistage decision process, constitutes the stochastic control problem.

Patent
12 Jul 1976
TL;DR: In this article, a programmable multiple channel digital controller is used to generate control signals which are transmitted over electrical power lines of a building complex for enabling receivers associated with functional devices for controlling the operation of functional devices.
Abstract: A control system including a programmable multiple channel digital controller which is operable to generate control signals which are transmitted over electrical power lines of a building complex for enabling receivers associated with functional devices for controlling the operation of functional devices, the transmitter being operable to transmit control signals during selected ones of a plurality of data channels which define a data frame, and in one embodiment, different ones of the receivers are programmed to respond to control signals transmitted in different data channels for controlling the associated functional device In another embodiment, the transmitted control signals are coded to represent an address of one or more of the receivers and a control command, each receiver comparing its address with the transmitted address, and the addressed receiver effecting the control function represented by the control command

Journal ArticleDOI
TL;DR: In this article, a multilevel feedback control scheme is proposed for optimization of large-scale systems composed of a number of (not necessarily weakly coupled) subsystems, where local controllers are used to optimize each subsystem, ignoring the interconnections.
Abstract: A multilevel feedback control scheme is proposed for optimization of large-scale systems composed of a number of (not necessarily weakly coupled) subsystems. Local controllers are used to optimize each subsystem, ignoring the interconnections. Then, a global controller may be applied to minimize the effect of interconnections and improve the performance of the overall system. At the cost of suboptimal performance, this optimization strategy ensures invariance of suboptimality and stability of the systems under structural perturbations whereby subsystems are disconnected and again connected during operation.

Patent
29 Sep 1976
TL;DR: In this article, an industrial control processor is employed in a numerical control system to operate the servo mechanisms on a machine tool in response to a part program stored on a tape, which includes unique hardware and software features which also allow it to operate as a programmable controller to control the discrete digital devices associated with the machine tool.
Abstract: An industrial control processor is employed in a numerical control system to operate the servo mechanisms on a machine tool in response to a part program stored on a tape. The industrial control processor includes unique hardware and software features which also allow it to operate as a programmable controller to control the discrete digital devices associated with the machine tool. The industrial control processor is programmed with a conventional computer type instruction set to perform numerical control functions and is programmed with a programmable controller type instruction set to perform the machine dependent logic functions. The resulting system maintains the state-of-the-art capabilities of a computer numerical control (CNC) and adds to it the flexibility and programming ease of a programmable controller.

Patent
01 Mar 1976
TL;DR: In this article, a fluid control system (and controller and moisture sensor therefor) having one or more latching solenoid operated pilot control valves and a master control unit for controlling the valves is described.
Abstract: A fluid control system (and controller and moisture sensor therefor) having one or more latching solenoid operated pilot control valves and a master control unit for controlling the valves. The valves utilize a concentric arrangement of the major components thereof, each being coaxially located with respect to a single housing member. The control electronics may be battery operated and may locate with respect to one valve to provide drive signals to control one or more valves in sequence. The control electronics utilizes an oscillator such as a crystal oscillator with a chain of count down flip-flops to provide binary signals up to a period of preferably twenty-four hours or more. A manual selection is provided to select among the longer period signals to control the frequency with which the operating cycle is initiated, with a second manual control being used to select one of the lower frequency signals to control the duration for which each valve will remain open. Logic is provided so that only one valve will be open at any one time thereby providing for sequential rather than simultaneous operation of a group of valves during each watering cycle. Alternate embodiments utilizing light sensitive controls are also disclosed.

Journal ArticleDOI
TL;DR: In this article, stateplane analysis techniques are employed to study the voltage step-up energy-storage dc-to-dc converter with a constant on-time and a constant frequency controller.
Abstract: State-plane analysis techniques are employed to study the voltage stepup energy-storage dc-to-dc converter. Within this framework, an example converter operating under the influence of a constant on-time and a constant frequency controller is examined. Qualitative insight gained through this approach is used to develop a conceptual free-running control law for the voltage stepup converter which can achieve steady-state operation in one on/off cycle of control. Digital computer simulation data are presented to illustrate and verify the theoretical discussions presented.

Journal ArticleDOI
TL;DR: In this paper, a feedback stabilization of a linear hyperbolic boundary value control system is implemented, and the property of controllability of the control system yields the asymptotic stability of the feedback system.

Journal ArticleDOI
01 Aug 1976
TL;DR: In this paper, the authors describe controller synthesis procedures for specific classes of such systems and give some of the ways in which these controllers differ from those derived under the assumption of perfect knowledge of future plant behavior.
Abstract: Dynamic models in which the coefficient processes exhibit sudden changes at random time points can be used to make manifest the influences of subsystem failures or rapid changes in the environment in which a system must operate. Control and regulation of such systems is complicated by the uncertainty which surrounds the effect of future events on system behavior. A satisfactory control policy must quantitatively discount these events of uncertain occurrence to provide good performance for a variety of operating conditions. This paper describes controller synthesis procedures for specific classes of such systems and gives some of the ways in which these controllers differ from those derived under the assumption of perfect knowledge of future plant behavior.


Journal ArticleDOI
TL;DR: The use of fuzzy set theory to design controllers has been pursued as a combined project by the University of Manchester Institute of Science and Technology and the British Steel Corporation as mentioned in this paper, which has led to an on-plant trial at Cleveland Sinter Plant where anticipated improvements in plant performance were achieved.

Patent
Jr. Alton L. Loe1
18 May 1976
TL;DR: In this paper, an improved particleboard manufacturing system where the weight of each mat for forming a particleboard is continuously monitored and controlled by a process controller as the mats are formed on a moving conveyor is presented.
Abstract: An improved particleboard manufacturing system wherein the weight of each mat for forming a particleboard is continuously monitored and controlled by a process controller as the mats are formed on a moving conveyor. The actual weight of each mat is determined and utilized by the process controller to selectively control the speed of the conveyor and the rate at which wood particles are deposited by a series of formers that are located along the conveyor system to thereby control the weight of mats currently being produced. The process controller includes a control system for continuously controlling mat weight by supplying former speed control signals that are related to a predicted weight error signal, developed within the control system, and a measured weight error signal equal to the difference between a desired or target weight and the actual weight of each mat. A signal, equal to the difference between the measured error and the predicted error, is conditioned by a transfer function unit to supply a signal suitable for driving each former of the particle board manufacturing system. To provide a near optimal control system, the signal conditioning supplied by the transfer function unit is adaptively tuned on the basis of the measured weight error. A second control system is included in the process controller to provide automatic mat weight control whenever the system operator changes the production rate by altering the speed of the conveyor system. During such changes in production rate, this control system modifies the former speed based on changes in conveyor speed. A third control system, contained within the process controller, permits the controlled particleboard manufacturing system to be efficiently changed from the production of one grade of particleboard to another grade while minimizing the number of unacceptable mats that are produced. The process controller also includes a fourth control system that allows the controlled particleboard manufacturing system to be reactivated after a brief interruption in production without producing a large number of mats of an unacceptable weight.

Patent
16 Mar 1976
TL;DR: In this paper, a dynamic sound controller is designed to automatically adjust and shape the spectral distribution and amplitude of random masking noise before delivery via speakers to the environment of a room according to a preprogrammed timing sequence.
Abstract: A dynamic sound controller is designed to automatically adjust and shape the spectral distribution and amplitude of random masking noise before delivery via speakers to the environment of a room according to a preprogrammed timing sequence. In addition, the sound controller is capable of operating as a security and fire alarm system and is further capable of mixing a predetermined amount of background music and paging signals into the same set of speakers. The sound controller of the present invention is further adaptable to a variety of environmental detectors which adjust and shape the noise in response to such factors as temperature, humidity, light level, ionization level and background noise level. A method for shaping spectral distribution and for adjusting amplitude of masking noise in relation to the measured ambient and intrusion noise levels is disclosed.

Patent
27 Dec 1976
TL;DR: In this paper, a numerical control system for a machine tool is simulated in the read only memory of a computer which is used as a controller for the flow of digital information between the control display panel, the tape reader, a memory, the machine tool and other parts of the system.
Abstract: A numerical control system for a machine tool. The relay controls for the machine tool are simulated in the read only memory of a computer which is used as a controller for the flow of digital information between the control display panel, the tape reader, a memory, the machine tool and other parts of the system. Since the simulation is based on relay diagrams, the user can customize the control system to his requirements without having been previously trained in computer programming or computer systems. Also, since the control system is adapted to the machine tool by software changes, the same hardware is usable without modification by a variety of machine tools, such as turret lathes and milling machines, and under a variety of operation conditions. Data debouncing and diagnostic aids are included in the system.

Journal ArticleDOI
TL;DR: In this paper, a method is presented which transforms a large class of optimal control problems with fixed delays to non-delayed problems, thus permitting classical results to be used in their analysis.
Abstract: A method is exhibited which transforms a large class of optimal control problems with fixed delays to nondelayed problems, thus permitting classical results to be used in their analysis.

Patent
01 Nov 1976
TL;DR: In this paper, a control signal to the process is provided to a process model having a predictive element and a delay element adapted to reproduce as closely as possible the measured process variable to the control signal.
Abstract: In a process control system, a control signal to the process is provided to a process model having a predictive element and a delay element adapted to reproduce as closely as possible the action of the measured process variable to the control signal. The variable input signal to the process controller, upon which generation of the process control signal is based, is generated by multiplying the signal from the predictive portion of the process model by a correction factor generated in response to the ratio of the actual process measurement signal to the delayed model output signal.

Patent
10 Mar 1976
TL;DR: In this article, a demand controller for connecting and disconnecting loads from a power source has a plurality of control elements in two priority groups, an equal priority group and a set priority group.
Abstract: A demand controller for connecting and disconnecting loads from a power source has a plurality of control elements in two priority groups, an equal priority group and a set priority group. Loads are controlled by the control elements to be connected and disconnected. A control means directs signals for restoring and shedding the loads and for the priority between the two groups of control elements.

Journal ArticleDOI
01 Jan 1976
TL;DR: In this paper, a hierarchical structured, suboptimal controller for a linear stochastic system composed of fast and slow subsystems is presented, and it is proved that the controller is optimal in the limit as the separation of time scales of the subsystems becomes infinite.
Abstract: This short paper develops a hierarchically structured, suboptimal controller for a linear stochastic system composed of fast and slow subsystems. It is proved that the controller is optimal in the limit as the separation of time scales of the subsystems becomes infinite. The methodology is illustrated by design of a controller to suppress the phugoid and short-period modes of the longitudinal dynamics of the F-8 aircraft.

Patent
22 Apr 1976
TL;DR: A numerical control system utilizes a programmable sequence controller as a data transmitter for transmitting numerical control data from a digital computer to machine controllers associated with numerically controlled machine tools as discussed by the authors.
Abstract: A numerical control system utilizes a programmable sequence controller as a data transmitter for transmitting numerical control data from a digital computer to machine controllers associated with numerically controlled machine tools. The digital computer converts each of the least units of the numerical control data to a predetermined number of output commands and, upon request, transfers the output commands along with address codes to the sequence controller which has an input-output circuit connected at its output terminals with data input terminals of the machine controllers, so that by selectively setting and resetting the output terminals designated by the address codes, the sequency controller can supply the numerical control data to any one of the machine controllers.