摘要:

The response and stability limits of computer-operated control and surveillance systems that employ variable sampling rates are investigated. Stability calculations and simulated results are presented.

DOI:10.1049/ip-d.1991.0026

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper describes a searching algorithm, based on the Routh array, to determine the unknown coefficients of a Hurwitz polynomialĀ(s) of degreen, where polynomialP(s) of degreem−1(m−1<n) is given and determines the firstmcoefficients. Sufficient conditions are derived to ensure that no solution exists, and a criterion of failure of the search is also derived and is shown to be both necessary and sufficient. Some examples are given, and it is demonstrated that increasing the number of restrictions on the ranges of the search increases the speed of solution and the number of solutions found. It is also shown that increasing the number of trials (Np) increases the time taken and the number of solutions found. The examples illustrate how the given polynomialP(s) restricts the range of values of the unknown coefficients and how, in particular, this may lead to a need for very large or very small gains for implementation of state variable feedback.

DOI:10.1049/ip-d.1991.0027

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A number of methods have been proposed for the identification and self learning of relational fuzzy models. The paper compares some of the methods and looks at their tolerance to noise and to the choice of initial fuzzy ranges. Data from runs of a simulated fed-batch fermenter are used as a test case. The results show that identified relational models can give as good results as rule-based models and can be made to be very tolerant of noise in the identification data.

DOI:10.1049/ip-d.1991.0028

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A system (A,Bd) with two input channels which correspond to its two interconnected subsystems (A11,B22) and (A22,B22), is considered. The conditions for (A,Bd) to be controllable by only one of the input channels are then formulated. The conditions found replace the usual controllability conditions and involve only certain submatrices of the initial system matricesAandBd; as such, they are particularly well suited for the analysis of large-scale systems.

DOI:10.1049/ip-d.1991.0029

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Two types of asymptotic observer are constructed for constrained robot systems in this paper. Since a constrained robot, in general, involves a set of differential equations and a set of algebraic equations, both differential and algebraic variables should be estimated. This gives arise to difficulty in estimating the algebraic variables which are the contact forces. The difficulty is eased by introducing a nonlinear transformation. Although the transformation causes nonlinear coupling on the input, asymptotic observers can be constructed in terms of the transformed system by a special treatment. Since both the contact force and the motion of the robot can be directly estimated, the observers may be useful for the controller design of the constrained robot system.

DOI:10.1049/ip-d.1991.0030

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper reports the activities of a community club formed to design and build an operational real-time knowledge based system for process control. It gives the background to the club and the mechanisms developed to ensure the dissemination of the knowledge gained during the development of the project. A set of requirements for real-time knowledge based systems is presented, and a description of the system developed to satisfy this is given. This provides for the representation of procedural and declarative knowledge sources, allows temporal reasoning, and has facilities for representing and reasoning with uncertain information. It also describes an advanced system for time-constrained reasoning in terms of a priority scheduler dealing with autonomous activities. A description of the application demonstrator chosen from the club members is given. This is a quality control task on a batch chemical process with wide variation in feedstcok quality and uncertain and inaccessible measurements. An extensive performance evaluation of the operational system is presented, showing that the performance of the system is comparable to that of the best operators and considerably better than the standard operating procedures. Finally, conclusions on the success of the club and the technology are given, and suggestions for future work provided.

DOI:10.1049/ip-d.1991.0031

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The optimal control of stochastic systems, such as a thin rib machining process, can lead to improved productivity and enhanced accuracy. This paper addresses the problem of identification and optimal control of stochastic tool path error in a thin rib machining process, both analytically and experimentally. Tool path error, in numerically controlled machines, consists of both deterministic and stochastic components and is defined as the vector difference between the programmed path and the actual path taken by the tool relative to the workpiece. A methodology is developed to identify the cutting process parameters based on experimental data from the thin rib machining of microwave guides. An LQG optimal controller was designed to minimise the stochastic tool path error. The results of optimal controller simulation are discussed. The microprocessor-based online optimal controller was validated, on a small computer numerically controlled (CNC) milling machine, to demonstrate improved performance in the thin rib machining of microwave guides.

DOI:10.1049/ip-d.1991.0032

出版商:IEE    

年代:1991

数据来源: IET

摘要:

This work considers the tracking of a command or reference input, whose future values are known up to a given horizon. The approach used is to solve a spectral factorisation for the optimal closed-loop poles, followed by a set of equations which give additional system zeros. This set of equations arises from a least-squares optimisation-based procedure, previously used to design moving-average prefilters for systems with prespecified closed-loop poles. It is demonstrated how the equations for the prefilter coefficients decouple when the closed-loop poles are chosen from the appropriate spectral factorisation. This allows the computation of the coefficients to be simplified. For the finite preview case, it is shown how the structure of the command generator transfer function affects the design. The known result that, for infinite preview, the optimal prefilter is a matched filter whose coefficients are independent of the reference input, is also obtained. An example is given, illustrating the design procedure for various reference inputs. The work is also applied to the simulation of an aircraft terrain-following system.

DOI:10.1049/ip-d.1991.0033

出版商:IEE    

年代:1991

数据来源: IET

摘要:

There are many control system applications where there is a requirement to track a reference signal which is periodic. Examples of this type of application include scanning systems such as those for optical surveillance or radar tracking, and industrial automation systems where robots repetitively follow set trajectories. The conventional integral compensator gives zero error at steady state by providing an infinite gain in the forward path of a control compensator. A compensator based on a digital comb filter can be used to provide infinite gain at a set of harmonically related frequencies. In this way it is possible to provide a digital comb compensator which gives zero steady-state error to a periodic input. The poles of the compensator are determined by the tracking requirement; the zeros must be designed so that the phase shift in the plant will not cause closed-loop instability. An example is given where the shaft angle of a small motor is controlled to track a periodic reference input.

DOI:10.1049/ip-d.1991.0034

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Improvements to the control of the temperature in greenhouses heated by hot water pipes were developed in order to enhance both energy conservation and crop protection. Acceptable control can be obtained in some greenhouses by feedback of internal air temperature samples only, but much more robust control is obtained if heating pipe temperatures are included in the feedback. The heating system has long time constants, and with digital control the use of a relatively coarse sampling interval leads to better control. Gain coefficients for the feedback can be estimated from analysis of the uncontrolled response to heating if the pole positions for the controlled response are chosen. Suitable pole positions give slightly soft control, and the heating and cooling rates demanded can be achieved with limited adjustments of the heating valve.

DOI:10.1049/ip-d.1991.0035

出版商:IEE    

年代:1991

数据来源: IET