摘要:

A self-tuning model-based approach to extremum control described where a number of control variables can be manipulated to maximise a scalar output. A number of possible estimation models are considered and the local convergence properties of the resulting self-tuning algorithms are investigated.

DOI:10.1049/ip-d.1993.0009

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The paper details the design and experimental implementation of a practical discrete-time version of a sliding-mode controller. The controller is derived and proven robustly stable to bounded plant modelling errors and exogenous disturbances. Sliding-surface design is treated as an energy minimisation problem where state energy during sliding on the surface is minimised according to a linear quadratic measure. Analysis of the properties of the control system lead to static and dynamic optimal switching gains. Application of the controller to simulated and experimental versions of a coupled-drives apparatus provide evidence of the robust performance and stability of the controller with classical linear quadratic optimal control. Also demonstrated is the compared effectiveness of the dynamic optimal switching gain.

DOI:10.1049/ip-d.1993.0010

出版商:IEE    

年代:1993

数据来源: IET

摘要:

New insights on the role of the innovations system representation in the context of the optimal LQG (H2) ‘standard’ problem are provided. The optimal controller is derived by using polynomial matrix techniques based on an innovations representation of the system. This can be obtained from the physical description by solving an appropriate minimum mean-square error filtering problem. The key result is that both the descriptions share the same optimal controller. A quite general cascade control structure is revisited in the present setting and the appropriate filtering problem is solved. The optimal controller is further obtained and the overall design procedure is compared with the one based on the physical system description. As a result, both a generalisation of the solution for the proposed cascade control problem and a better understanding of the role of the innovations system representation are provided.

DOI:10.1049/ip-d.1993.0011

出版商:IEE    

年代:1993

数据来源: IET

摘要:

An optimal multivariable proportional-integral (PI) controller with preassigned eigen spectrum is designed so that the system output would track constant reference inputs in spite of constant but unknown plant disturbances. A sequential strategy for modal servomechanism design is given for the above problem. In addition, since the proposed PI controller is of state feedback type, an observer capable of estimating the unmeasurable state variables in spite of the presence of unknown disturbances is introduced, thus resulting in a suboptimal overall system. The separation property for the overall servo/observer system is illustrated. The design strategy is successfully used for position control of a brushless DC motor, and in a regulator mode for controlling a headbox which is an integral part of the modern paper machines used in the pulp and paper industry.

DOI:10.1049/ip-d.1993.0012

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The problem of the global output tracking is considered for a class of single-input single- output nonlinear systems. The class of nonlinear systems considered is constituted by the systems linearisable via state feedback, while the class of reference signals to be asymptotically tracked is constituted by the reference outputs obtained by assigning polynomial reference signals to the state variables. A procedure for the design of a compensator is proposed, which ensures a global convergence property, under sufficient conditions, which, in the case of linear systems, reduce to the absence of invariant zeros in the origin of the complex plane. No minimum phase requirement is needed for applying the procedure. The paper ends with an example and some simulation runs which show the effectiveness of the controller proposed here.

DOI:10.1049/ip-d.1993.0013

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The paper presents a hybrid state-space self-tuner using a new dual-rate sampling scheme for digital adaptive control of continuous-time uncertain linear systems. A state-space-based recursive least-squares algorithm, together with a variable forgetting factor, is used for direct estimations of both the equivalent discrete-time uncertain linear system parameters and the associated discrete-time state of a continuous-time uncertain linear system from the sampled input and output data. An analogue optimal regional pole-placement design method is used for designing an optimal observer-based analogue controller. A suboptimal observer-based digital controller is then designed from the designed analogue controller using digital redesign technique. To enhance the robustness of parameter identification and state estimation algorithms, a dynamic bound for a class of uncertain bilinear parameters and a fast-rate digital controller are developed at each fast-sampling period. Also, to accommodate computation loads and computation delay for developing the advanced hybrid self-tuner, the designed analogue controller and observer gains are both updated at each slow-sampling period. This control technique has been successfully applied to benchmark control problems.

DOI:10.1049/ip-d.1993.0014

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The robust adaptive control of time-varying linear systems in the presence of bounded external disturbances is discussed. A new polynomial approximation scheme is proposed to approximate unknown time-varying parameters of the plant. A modified least-squares estimator with a relative dead zone is applied to identify the resulting unknown parameters. The control law is derived by minimising a quadratic cost function which penalises both model tracking errors and excessive control actions. It is shown theoretically that robust stability can be established in the presence of unmodelled dynamics due to approximate errors and external disturbances. Simulation results demonstrate the effectiveness of the proposed new controller.

DOI:10.1049/ip-d.1993.0015

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The subject of the paper is the robust control of a class of sampled-data nonlinear systems with real time-varying parameter uncertainty and unknown cone-bounded nonlinearity. We consider the problems of robust stabilisation and robust performance in anH∞sense, and attention is focused on the design of linear dynamic sampled-data output feedback controllers. A control design methodology is proposed for solving both problems by recasting them into ‘scaled’H∞control problems for a related system which involve neither parameter uncertainty nor unknown nonlinearity.

DOI:10.1049/ip-d.1993.0016

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The implementation of the decomposition of linear discrete-time multivariable problems through either singular values/principal directions, or eigenvalues/eigenvectors is inherently anti-causal. One way to avoid this is to introduce a ‘pseudodelay’ into the controller, but this is undesirable. Here the problem is examined in the scalar case, and a new algorithm proposed which deploys a kernel to characterise all the available degrees of freedom, and thus overcome completely the problems of delay and anticausality.

DOI:10.1049/ip-d.1993.0017

出版商:IEE    

年代:1993

数据来源: IET

摘要:

TheH∞filtering problem of state estimation for LTI systems is considered. The LTI system is driven at its input and corrupted at its output by processes with known energy bounds (but unknown spectral densities), and state estimates are sought such that the energy of the estimation error is minimised. TheH∞fitering problem is formulated as a model-matching problem and is solved using a state-space based algebraic approach. A characterisation for a family ofH∞filters is obtained in the form of a linear fractional transformation. It is shown that theH∞filter generalises the Kalman filter and a condition is given under which theH∞filter reduces to the Kalman filter. A derivation for minimum-entropyH∞filters is given.

DOI:10.1049/ip-d.1993.0018

出版商:IEE    

年代:1993

数据来源: IET