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Showing papers on "Robust control published in 1981"


Journal ArticleDOI
TL;DR: Singular perturbation analysis is employed to study the robustness of output feedback control schemes for linear time-invariant systems and it is shown that such a strategy may, in general, be destabilizing even when the neglected modes are asymptotically stable.
Abstract: Singular perturbation analysis is employed to study the robustness of output feedback control schemes for linear time-invariant systems. The effect of designing the control strategy using a model that neglects unknown parasitic elements is considered. It is shown that such a strategy may, in general, be destabilizing even when the neglected modes are asymptotically stable. Special structures that will not permit this situation and will guarantee asymptotic stability are illustrated.

94 citations


Journal ArticleDOI
01 Dec 1981
TL;DR: The decentralized robust servomechanism problem with constant disturbances/set points is considered in this paper for large flexible space structures (LFSS) and it is shown that for LFSS with point force actuators co-located with displacementrate sensors that the decentralized fixed modes are precisely equal to the centralized fixed modes of the system.
Abstract: The decentralized robust servomechanism problem with constant disturbances/set points is considered in this paper for large flexible space structures (LFSS). It is shown that for LFSS which have colocated, mutually dual sensors and actuators, the decentralized fixed modes [1] of the system are precisely equal to the centralized fixed modes [2] of the system. Simple necessary and sufficient conditions are then obtained for a solution to exist for the robust decentralized servomechanism problem [3] for the system. A controller is demonstrated which, for this class of LFSS systems, eliminates the "spillover problem." A two-hundreth-order numerical example of an LFSS control problem using the Purdue model [4] is included to illustrate the results.

71 citations


Journal ArticleDOI
TL;DR: In this paper, a separation roll autopilot is designed for air-launched missiles using classical control theory and modern control theory to obtain an optimal low frequency performance, where the autopilot design is carried out by decoupling the pitch, yaw and roll channels.
Abstract: The direct application of optimal control techniques to a complete autopilot design leads to a control system which requires excessive instrumentation and is sensitive to variations in the high frequency model A better approach is presented which utilizes classical control theory to bound the high frequency design and modern control theory to obtain optimal low frequency performance Results are presented for a separation roll autopilot demonstrating the appropriate tradeoffs and benefits associated w i t h the new design procedure Air launched missiles require active autopilot control for safe separation from modern launch aircraft because the f low field in the vicinity of the aircraft causes large torque disturbances on the missile and because the aircraft may be m=euvering when it releases its missile The effect of these disturbances and initial conditions are typically sensed by rate gyros and accelerometers whose out puts are connected through autopilot control circuitry to f in actuators Initially autopilot design is carried out b 1 decoupling the pitch, yaw and roll channels ( When this is done,classicd control theory has proven itself to be a valuable and efficient tool for autopilot design However aerodynamic crosscouplin g exists because the surface features of the missile create asymmetric flow fields over the control surfaces at c??fferent orientations of wind angle and angle of attack A simplified block diagram showing the cross-coupling appears in Fig I Here, if the roll rate response time is close enough to the pitchfyaw response time and the cross-coupling aerodynamic gain is high enough, instability can result Therefore successful autopilot design must take into consideration aerodynamic cross-couph g Althou h classical design techniques are well established fi 9 345) and relatively straight forward for planar autopilot design, trial and error must b? A I ROLL AUTOPILOT 1 ACTUATOR AND a L SENSOR -

59 citations


Journal ArticleDOI
TL;DR: In this paper, the feasibility of the variable measurements structure is investigated within the framework of controlling a tubular chemical reactor and an on-line sequential analysis of the temperature measurements along the length of the reactor, allows a fast and time-adaptive selection of the best measurements to be used in a low order, simple and robust control scheme.

46 citations


Journal ArticleDOI
TL;DR: In this paper, an online sequential analysis of the measurement equations is presented, which allows for a fast and robust updating of the best measurement structure for the control of several processing systems where updating the measurements' configuration would result in a robust control behavior.
Abstract: The idea of using variable measurement structures for chemical process control is an attractive one but in the past it has encountered significant computational and implementational difficulties. In the present work an on-line sequential analysis of the measurement equations is presented, which allows for a fast and robust updating of the best measurement structure for the control of several processing systems where updating the measurements' configuration would result in a robust control behaviour. The present paper develops the theoretical foundations for the concept of the variable measurement structures, and implements it for systems operating in a pseudo-steady state or dynamic environment. Furthermore, a strategy is developed for the identification of the optimum measurement structure in the presence of disturbances. Finally the concept of variable measurement structures is discussed with reference to the control of two processing units of interest to the chemical industry ; a distillation column an...

33 citations


Book
01 Jan 1981
TL;DR: In this article, the problem of servomechanism control of unknown multi-input, multi-output linear systems with stochastic disturbances is addressed by introducing a jump process in the disturbances.
Abstract: The problem of servomechanism control of unknown multi-input, multi-output linear systems with stochastic disturbances is addressed here. In deterministic framework Internal Model Principle gives linear stationary controller structures which are robust (or structurally stable) with respect to uncertainty in system parameters, and allow asymptotic tracking of non-decaying reference signals in presence of non-decaying disturbances. An appropriate stochastic framework that reflects important characteristics of realistic disturbances for this robust servomechanism problem is obtained by introducing a jump process in the disturbances. Discrete-time adaptive control schemes based upon this framework are developed so that stopping of adaption results in a robust servomechanism. For a stochastic approximation type update it is shown that strict positive realness of a certain operator associated with a prediction form of the system is sufficient for global convergence of the resulting self-tuning scheme with probability one. The resulting control gives asymptotically optimal control performance.

11 citations


Dissertation
01 Jan 1981

10 citations


Proceedings ArticleDOI
01 Dec 1981
TL;DR: In this article, Lyapunov stability results are summarized and applied to examine the behaviour of adaptive identification and control algorithms applied to non-stationary plants where certain persistency of excitation conditions are satisfied.
Abstract: Lyapunov stability results are summarized which are robust in character. These results are applied to examine the behaviour of adaptive identification and control algorithms applied to non-stationary plants where certain persistency of excitation conditions are satisfied.

10 citations


01 Dec 1981
TL;DR: The Doyle and Stein robustness enhancement technique for continuous-time LQG stochastic controllers was investigated in application to simple examples and a realistic Apollo Command Service Module/Lunar Module Thrust Vector Control System that exhibited severe robustness problems in its initial design.
Abstract: : The Doyle and Stein robustness enhancement technique for continuous-time LQG stochastic controllers was investigated in application to simple examples and a realistic Apollo Command Service Module/Lunar Module Thrust Vector Control System that exhibited severe robustness problems in its initial design. This technique was then extended to discrete-time systems in two ways. First, the continuous-time controller to which the Doyle and Stein technique had been applied was discretized using first order approximations. Second, an approximation to their continuous-time technique was developed for sampled-data control systems. In addition, an attempt was made to enhance the robustness of sampled-data systems by directly picking the gain of the Kalman filter within the controller structure based on an approach similar to that of Doyle and Stein.

9 citations


Journal ArticleDOI
TL;DR: In this article, a fixed gain controller with three paralleled gyros and dynamic output feedback is designed to meet the pole region requirements of an F4-E aircraft with additional horizontal canards.

9 citations


Journal ArticleDOI
TL;DR: The TRANSRAPID-Versuchsanlage im Emsland and the Optimale Regelung linearer deterministischer Prozesse: Energieoptimale Fahrprogramme für Schienenfahrzeuge.
Abstract: [1] Eitlhuber, E.: Die TRANSRAPID-Versuchsanlage im Emsland. Eisenbahntechnische Rundschau 29 (1980), S. 409^414. [2] Kraft, K.H.: Leistungsgrenzen im Schnellbahnnetz. Statusseminar Magnetbahnentwicklung VIII, Bad Reichenhall 1980. [3] Schnieder, E.: Entwurf und Simulation einer Fahrzeugsteuerung für zukünftige Magnetschnellbahnen. Statusseminar Megnetbahnentwicklung VIII, Bad Reichenhall 1980. [4] Pontrjagin, L.S.: Mathematische Theorie optimaler Prozesse. Verlag: R. Oldenbourg, München 1967. [5] Äthans, M„ und Falb, P.: Optimal Control. Verlag: McGraw-Hill, New York 1966. [6] Weihrich, G.: Optimale Regelung linearer deterministischer Prozesse. Verlag: R. Oldenbourg, München 1973. [7] Horn, P.: Über die Anwendung des Maximumprinzips von Pontrjagin zur Ermittlung von Algorithmen für eine energieoptimale Zugsteuerung. Wissenschaftliche Zeitschrift der Hochschule für Verkehrswesen „Friedrich List\" (Dresden) 18 (1971), S. 919-943. [8] Schmidt, G., und Torres-Peraza, M.: Energieoptimale Fahrprogramme für Schienenfahrzeuge. Glasers Annalen (Zeitschrift für Eisenbahnwesen und Verkehrstechnik) 93 (1969), S. 265-270.

Proceedings ArticleDOI
01 Dec 1981
TL;DR: Frequency-shaping methods developed for control law design are extended for robust state estimation and for robust feedback control when a filter is used for state estimation.
Abstract: Frequency-shaping methods developed for control law design are extended for robust state estimation and for robust feedback control when a filter is used for state estimation. Robustness is achieved by reducing filter gain outside model bandwidth. The frequency-shaping of cost functionals can also be used to design several low-order controllers for a high-order system. A complete design algorithm has been developed. Physical knowledge of the system as well as estimation requirements can be incoprorated in the estimator. A highly robust control system can be obtained when a frequency-shaped estimator is used in feedback design.

Journal ArticleDOI
H. Mayeda1, S. Miyoshi1
TL;DR: In this paper, the robust compensator of the tracking problem with internal stability is investigated for the structured systems, and a design scheme of the robust compressive compensator is proposed, use being made of the structure of the system.

Journal ArticleDOI
TL;DR: In this paper, a robust control strategy for tracking a given reference signal input independent of the disturbance signals and the process parameter variations, and for ensuring zero asymptotic digital control signal input is proposed.

Proceedings ArticleDOI
01 Dec 1981
TL;DR: In this article, the steady state tracking and regulation errors are considered for a controlled linear time-invariant system which includes either a feedforward compensator or a robust servo-compensator.
Abstract: The steady-state tracking and regulation errors are considered for a controlled linear time-invariant system which includes either a feedforward compensator [1] or a robust servo-compensator [2]. The controlled system is subjected to classes of reference and disturbance inputs larger than and including the class of inputs for which the compensator was designed, and the resulting steady-state error is parameterized in terms of generalized error coefficients. These define the steady-state error in terms of plant and controller parameters, and so represent a generalization of the error coefficients of classical control theory. It is then shown that exact steady-state error regulation may be achieved in the robust servomechanism controller for a class of disturbance/reference-input signals which is larger than the nominal class of input signals for which the controller is designed.

Proceedings ArticleDOI
01 Dec 1981
TL;DR: In this paper, a new approach to control structure synthesis using a frequency domain description of the system is suggested, where the screening of alternate control structures is carried out in two stages, at the first stage the fundamental limitations to control quality, which are shown to be transmission zeros and time delays, are identified and preliminary control structure selection is made.
Abstract: The traditional methods for the actuator and sensor selection based on LQG theory have found only limited use in process control. The main reason is that LQG theory offers a handy design tool but the numerical value of the quadratic performance index lacks practical significance. A new approach to control structure synthesis using a frequency domain description of the system is suggested here. The screening of alternate control structures is carried out in two stages. At the first stage the fundamental limitations to control quality, which are shown to be RHP transmission zeroes and time delays, are identified and preliminary control structure selection is made. In the second stage the performance of the remaining systems is compared when they are robust with respect to a prespecified model-plant mismatch. The intuitive appeal of this screening procedure should make it attractive for industrial applications. Some features of this new method are illustrated on a heat exchanger network and a distillation column.

Journal ArticleDOI
TL;DR: In this paper, an inverse optimal control problem is formulated to develop robust control laws for purely oscillatory systems, where the optimal control solution requires output feedback with specified constraints, leading to robustness with respect to unmodeled modes and a large class of parameter variations.
Abstract: An inverse optimal control problem is formulated to develop robust control laws for purely oscillatory systems. The optimal control solution requires output feedback with specified constraints, leading to robustness with respect to unmodeled modes and a large class of parameter variations. The robustness properties are proved directly from known properties of control laws resulting from quadratic performance indices. The control laws are useful for poorly damped flexible structures.


Journal ArticleDOI
TL;DR: In this article, a mathematical model of a liquid metal fast breeder reactor (LMFBR) was developed and a variety of system models over the whole load range from 30 % to 100 % of full load were investigated and compared.

Journal ArticleDOI
TL;DR: The structural optimality of optimal control is defined as its invariant optimality in the usual sense of minimizing some quadratic cost, under the presence of free structural variations sufficiently small in the system parameters.

Journal ArticleDOI
TL;DR: In this paper, the overall dynamics of Maglev vehicles is investigated, regarding vehicle, suspension control and guideway, and the mathematical description results in a very complicated high-order model containing uncertain parameters for the suspension magnets.

Journal ArticleDOI
Y. Kida1, E. Masada1
TL;DR: In this paper, a controller and an observer with some optimality for the model is constructed and its robustness is shown, and the relation between the original disturbance and the state vector of the observer is considered.

Book ChapterDOI
01 Jan 1981
TL;DR: In this article, an electropneumatic four-way-spool valve + double acted piston servomotor is controlled by a special designed compensator, which is solved as a problem of the poles allocation and structural stability.
Abstract: A new system configuration of a pneumatic actuator is presented. An electropneumatic four-way-spool valve + double acted piston servomotor is controlled by a special designed compensator. By using a proper local linearization and an improved choice of the state variables of the controlled pneumatic subsystem, the synthesis of a compensator is solved as a problem of the poles allocation and structural stability. To prove the system compatibility, meaning the robust control in spite of the nonlinear influence of the pneumatic actuator, a simulation program is successfully developed. An significant improvement of the actuator dynamics with respect to the disturbance rejection is reported and the replacement of conventional positioner becomes possible.

Proceedings ArticleDOI
01 Dec 1981
TL;DR: A multivariable Wiener-Hopf control design is used to provide high gains in the necessary frequency range and low gaines outside this range, in order to achieve performance and stability robustness.
Abstract: A method for the sythesis and analysis of robust control designs for high performance manipulator arms is described. Input-output norms are used to analyze the robustness of flexible manipulator control designs in the presence of flexible mode spillover and parameter uncertainty. A multivariable Wiener-Hopf control design is used to provide high gains in the necessary frequency range and low gaines outside this range, in order to achieve performance and stability robustness.

Proceedings ArticleDOI
01 Dec 1981
TL;DR: An approximate solution to the dual control problem is proposed, based on a minimax criterion and a loss function which penalizes the difference between the quadratic loss associated with a given controller and that which could be achieved if all unknown parameters were known.
Abstract: An approximate solution to the dual control problem is proposed. The new algorithm is based on a minimax criterion and a loss function which penalizes the difference between the quadratic loss associated with a given controller and that which could be achieved if all unknown parameters were known. The approximate solution, while using Lainiotis' multiple model adaptive controller (MMAC) avoids most of the difficulty associated with the standard application of MMAC. In particular, it is no longer required (or even desired) that the parametric uncertainty space be finite. Two or three control-MMAC's perform extremely well in the presence of convex uncertainty spaces. Furthermore, the practical problems uncovered in the F8 DFBW MMAC effort are eliminated because they are automatically handled by the minimax design algorithm. Finally, in contrast with other dual control algorithms, the proposed technique requires only a relatively small amount of real time processing (that required by standard MMAC algorithms).