摘要:

The paper presents a general Lagrangian formulation capable of studying the nonlinear dynamics and control of spacecraft with interconnected members in a tree-type topology. The nonlinear control, based on the feedback linearization technique (FLT) is adopted. The simplicity of the control algorithm and its applicability to both rigid and flexible spacecraft make the technique quite attractive. Application of the formulation is illustrated using a spacecraft of contemporary interest, INdian SATellite-II (INSAT-II), a next generation of multipurpose communications spacecraft launched in August 1992. The uncontrolled dynamics show the spacecraft to be in an inherently unstable equilibrium orientation. Control, based on the FLT, is then applied to restore the desired attitude of the spacecraft. The performance of three sets of control gains are compared. Even if the satellite is initially subjected to a large disturbance of 1°in pitch, roll, and yaw, the controller is successful in reducing the attitude error to less than 0.1°in about 2 minutes. The control scheme works remarkably well even with the inclusion of flexibility and thermal deformations of the appendages.

ISSN:0020-7179    

DOI:10.1080/00207179308923014

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An adaptive self-tuning control scheme is developed for end-point position control of flexible manipulators. The proposed scheme has three characteristics. First, it is based on a dynamic model of a flexible manipulator described in cartesian coordinates, which eliminates the burden and inaccuracy of translating a desired end-point trajectory to joint coordinates using inverse kinematic relations. Second, the effect of flexibility is included in the dynamic model by approximating flexible links with a number of rigid sublinks connected at fictitious joints. The relatively high stiffness of the fictitious joints is shown to result in a decomposition of the model into two subsystems operating at different rates. This allows for stabilization of the oscillatory modes associated with the flexible links by a fast feedback control in addition to a slower control for trajectory tracking. Third, the control is constructed from measurements of the end-point position and deformations of the flexible links, with the manipulator parameters required to form the control obtained using a recursive least-squares estimation algorithm, which is fast enough for on-line applications. Satisfactory results are obtained from digital simulation of a two-link flexible manipulator.

ISSN:0020-7179    

DOI:10.1080/00207179308923015

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A simple and robust disturbance-based control (DBC) method is introduced in this paper which employs a nominal model as the disturbance observer to estimate the overall disturbance, which includes the model-plant mismatch error, unmeasured external disturbances and cross-coupling in multivariable systems. The feedback of the estimated disturbance can eliminate the effect of external disturbances and structured perturbation caused by parameter variation, and decouple a multi-input multi-output (MIMO) system into a number of single-input single output (SISO) nominal subsystems. The root-locus method can be used to analyse the stability of DBC controlled systems and derive the design criterion. Subsequently, a robust controller can be designed based on each SISO nominal system. DBC can help the application of theH∞theory and the achievement of diagonal dominance. Application of DBC on a Bosch SCARA-type robot is presented to achieve decentralized joint control. Simulation results confirm the viability of the proposed disturbance-based controller.

ISSN:0020-7179    

DOI:10.1080/00207179308923016

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The ordinary MOESP algorithm presented in the first part of this series of papers is analysed and extended in this paper. First, an analysis is made which proves that the asymptotic unbiasedness of the estimated state-space quadruple [AT, BT, CT, D] critically depends on the unbiased calculation of the column space of the extended observability matrix. Second, it is proved that the latter quantity can be calculated asymptotically unbiasedly only when the stochastic additive errors on the output quantity are zero-mean white noise. The extension of the ordinary MOESP scheme with instrumental variables increases the applicability of this scheme. Two types of instrumental variables are proposed: (1) based on past input measurements; and (2) based on reconstructed state quantities. The first type yields asymptotic unbiased estimates when the perturbation on the output quantity is an arbitrary zero-mean stochastic process independent of the error-free input. However, a detailed sensitivity analysis demonstrates that for the finite data-length case the calculations can become very sensitive; this occurs when the particular system at hand has dominant modes close to the unit circle. In the same sensitivity analysis it is shown that far more robust results can be obtained with the second type of instrumental variables when the true state quantities are used. A number of guidelines are derived from the given sensitivity analysis to obtain accurate reconstructed state quantities. Efficient numerical implementations are presented for both extensions of the ordinary MOESP scheme. The obtained insights are verified by means of two realistic simulation studies. The developed extensions and strategy in these studies demonstrate excellent performances in the treatment of both identification problems.

ISSN:0020-7179    

DOI:10.1080/00207179308923017

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A tracking control design is proposed for both holonomic and non-holonomic constrained mechanical systems from a unified viewpoint. It will be shown that, according to the number of control inputs, if the state variables are available and the output variables are chosen properly, then the exponentially global tracking of positions and constraint forces on the constraint manifold is achieved for holonomic control systems by a static state feedback controller. From the same point of view, for non-holonomic control systems, the globally exponential tracking of positions is achieved by just a dynamic state feedback controller. Finally, by means of much discussion and many simulations, two typical non-holonomic examples— edge and a vertical wheel—are given to illustrate the essential features of the proposed design method.

ISSN:0020-7179    

DOI:10.1080/00207179308923018

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We present a moving horizon feedback system, based on constrained optimal control algorithms, for linear plants with input saturation. The system is a non-conventional sampled-data system: its sampling periods vary from sampling instant to sampling instant, and the control during the sampling time is not constant but determined by the solution of an open-loop optimal control problem. This is a two-part paper. In this part, we show that the proposed moving horizon control system is robustly stable, whether the state of the plant is measurable or not. In the second part, we show that the proposed moving horizon control system is capable of following a class of reference inputs and suppressing a class of disturbances. Experimental results show that the behaviour of the moving horizon control system is superior to that resulting from some alternative control laws.

ISSN:0020-7179    

DOI:10.1080/00207179308923019

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We present a moving horizon feedback system, based on constrained optimal control algorithms, for linear plants with input saturation. The system is a non-conventional sampled-data system: its sampling periods vary from sampling instant to sampling instant, and the control during the sampling time is not constant, but determined by the solution of an open loop optimal control problem. In Part 1 we showed that the proposed moving horizon control system is robustly stable. In this paper we show that it is capable of asymptotically suppressing a class ofL∞bounded disturbances that are restricted to a subspace, and of asymptotically following a class of reference inputs that are continuously differentiable, bounded in magnitude and slope, and restricted to a subspace.

ISSN:0020-7179    

DOI:10.1080/00207179308923020

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Robust approximation and worst-case approximate modelling of stable shift-invariant systems from corrupted transfer function estimates are studied in theH∞sense. Connections between the problem formulations of the present work and certain problems of worst-case system identification, notably the Helmicki-Jacobson-Nett problem formulation for identification inH∞, are established. Issues of model set selection are addressed using then-width concept: a concrete result establishesa prioriknowledge for which a certain rational model set is optimal in then-width sense. A notion of robust convergence is defined so that any untuned approximation method satisfying it has a generic well-posedness property for systems in the disk algebra. The existence of robustly convergent approximation methods based on any complete model set in the disk algebra is shown in a constructive way. A framework is given in which approximate models can be obtained as stable perturbations of the true system: these can be combined with the classical Fejér and de la Vallée-Pous-sin polynomial approximation operators to provide robustly convergent approximation methods. Furthermore, concrete results are given for the fundamental problem of model reduction from corrupted transfer function estimates or from experimentally obtained models for the optimal Hankel norm approximation method and for a least squares method.

ISSN:0020-7179    

DOI:10.1080/00207179308923021

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The minimal control synthesis (MCS) algorithm is an adaptive control strategy that requires no prior knowledge of plant dynamic parameters, and yet is guaranteed to provide global asymptotic stability of the closed-loop system. The purpose of this paper is to present an extension to MCS that enables on-line identification of the plant parameters. It is emphasized that these parameters are not required for the MCS algorithm to function; instead, the parameters might be required for simulation exercises, conventional controller designs or on-line plant diagnosis. The theoretical assertions of MCS identification are supported by implementation of the algorithm on SISO and MIMO electro-mechanical plant.

ISSN:0020-7179    

DOI:10.1080/00207179308923022

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper the influence of uncertainty of linear discrete-time systems modelled with white parameters on the properties of mean-square stability and compensatability is considered. A measure for the uncertainty in the system matrices is introduced. This measure is also a measure for the uncertainty in the system in the sense that stability and compensatability decreases if this system uncertainty increases. It is indicated how to calculate numerically the mean-square stability and compensatability. The results are illustrated with examples.

ISSN:0020-7179    

DOI:10.1080/00207179308923023

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor