摘要:

Simple stability bounds for closed-loop robustness in the presence of modelling errors are presented in terms of the steady-state gain of the model. The effects of user-specified prefilters upon these bounds are discussed, leading to guidelines for selection of the filters. This allows commissioning of the adaptive controller to be done on the basis of the robustness of the nominal closed loop to modelling errors, based only upon the estimated model and the particular control strategy to be employed.

DOI:10.1049/ip-d.1991.0002

出版商:IEE    

年代:1991

数据来源: IET

摘要:

This paper is concerned with the evaluation of self-tuning control algorithms for the multivariable control of distillation columns. Effective distillation control remains a key concern of industry because of the high energy consumption associated with distillation processes. The results presented here are taken from a continuing programme of investigations aimed at improving distillation column control performance. The performance of several multi-variable self-tuning strategies is evaluated by online application to a pilot-scale binary distillation column which is subjected to disturbances of ±25% step changes in feed flow rate. The performance of the multivariable algorithms is compared with that achieved using conventional digital multiloop PI/PID control. The results have demonstrated that use of multivariable self-tuning control, in particular multirate-multivariable self-tuning control, can provide better regulatory performance for feed flow rate disturbances than can be achieved using a multiloop PI/PID strategy.

DOI:10.1049/ip-d.1991.0003

出版商:IEE    

年代:1991

数据来源: IET

摘要:

An algorithm to incorporate pole restriction into the generalised minimum-variance stochastic self-tuning controller is proposed. The closed-loop poles of the system are restricted to a user-chosen circle in thez-plane to meet maximum percentage overshoot and settling time specifications. A deadband introduced to the basic pole restriction algorithm leads to a piecewise time-invariant controller. The deadband algorithm reduces computational requirements and enhances the stability robustness of the system. Finally, simulation results indicate that in the control of a plant that changes bandwidth significantly during operation, the pole restriction controller is superior to its pole placement counterpart.

DOI:10.1049/ip-d.1991.0004

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A nonlinear general predictive controller (NLGPC) is described which is based on the use of a Hammerstein model within a recursive control algorithm. A key contribution of the paper is the use of a novel, one-step simple root solving procedure for the Hammerstein model, this being a fundamental part of the overall tuning algorithm. A comparison is made between NLGPC and nonlinear deadbeat control (NLDBC) using the same one-step nonlinear components, in order to investigate NLGPC advantages and disadvantages.

DOI:10.1049/ip-d.1991.0005

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper describes the design and implementation of an unusual self-adaptive temperature control system for a nonlinear heated bar system. The design is based on a proportional-integral-plus (PIP) control scheme, combined with a special recursive algorithm which continually updates the estimates of the rapidly variable parameters which characterise a piecewise-linear model of the heated bar system. Amongst the novel features of this true digital control (TDC) system design are: the nonminimum states-space (NMSS) formulation of the control problem, which allows for state-variable feedback pole assignment using only sampled input and output signals in the control law; the incorporation ofa prioriinformation on the physical nature of the system into the recursive estimation algorithm in order to enhance its parameter tracking capabilities; the exploitation of multirate sampling; and the implementation of the linear PIP control law in a bang-bang mode using pulsewidth modulation.

DOI:10.1049/ip-d.1991.0006

出版商:IEE    

年代:1991

数据来源: IET

摘要:

This paper presents a hybrid state-space self-tuning control scheme using dual-rate sampling for suboptimal digital adaptive control of linear time-invariant continuous-time multi-variable stochastic systems with unknown parameters. An equivalent fast-rate discrete-time state-space innovation model (with estimated states) of the continuous-time system is constructed by using the estimated system parameters and Kalman gain. To utilise the existing optimal regional-pole assignment method developed in the continuous-time domain, the constructed fast-rate discrete-time model is converted into an equivalent continuous-time model for the development of a state-feedback optimal control law with pole placement in a specific region. The developed analogue optimal control law is then converted into an equivalent pseudo-slow-rate digital control law via the proposed digital redesign technique, which can be realised via slow-rate digital electronics. The proposed method enables the development of a digitally implementable advanced control algorithm for digital adaptive control of continuous-time multivariable stochastic systems which may be unstable and/or have nonminimum phase.

DOI:10.1049/ip-d.1991.0007

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The central task in power station control is to meet the system demand while minimising state and input variations in the plant. In order to achieve good set-point following, the control system must make good use of coupling between the different control loops and if possible use information about future set points to smooth out the control activity. Characteristic generalised predictive control sets out to achieve both these objectives and hence would seem ideally suited to power station control. The presence of some fast and slow dynamics implies that the boiler-turbine system is in essence a stiff problem; the characteristic generalised predictive control (GPC) algorithm is suitably extended to take direct account of this. Simulation results show that the characteristic GPC algorithm (a) provides a systematic means of approaching the boiler-turbine problem and (b) affords some improvements in performance over traditional PID control schemes.

DOI:10.1049/ip-d.1991.0008

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper describes an alternative view of parameter tracking in recursive estimation and self-tuning control which is based on transient specification. The specific aim is to provide a recursive estimator with parameter tracking features and prescribed transient behaviour. In particular, a class of algorithms is developed by viewing recursive estimators as dynamical systems. Anad hocmodification is introduced which attempts to specify the transient response of parameter estimates. The technique is analogous to pole placement in linear time-invariant dynamical systems, and as such offers a traditional control systems interpretation to parameter tracking.

DOI:10.1049/ip-d.1991.0009

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The current generation of adaptive predictive controllers uses a standard single-step-ahead estimator with multi-step-ahead predictors. In order to obtain satisfactory results in applications, data are bandpass filtered before being used in the estimator. This paper demonstrates that the use of a standard RLS estimator with no data filtering frequently results in unstable closed loops if the parameters are used in a multi-step-ahead control scheme. A multi-step-ahead cost is introduced for parameter estimation as adualof the control law. It is shown that the method is superior to the standard scheme. The frequency response properties of this estimator indicate that prefiltering of the data prevalent among the reported successful applications of the predictive controller is a natural outcome of this choice of the cost for the estimator scheme. The paper provides some useful guidelines for the choice of order and time constants of these filters.

DOI:10.1049/ip-d.1991.0010

出版商:IEE    

年代:1991

数据来源: IET

摘要:

This paper presents a new multivariable self-tuning feedforward controller which not only achieves pole assignment but also realises static and dynamic decoupling control. The proposed controller can handle systems with different time delays between inputs and outputs. It is able to eliminate tracking errors and the effect of measurable disturbances. Static and dynamic disturbance rejection is realised. Simple explicit self-tuning algorithms are given. Two simulation examples are given to show the effectiveness of the proposed controller.

DOI:10.1049/ip-d.1991.0011

出版商:IEE    

年代:1991

数据来源: IET