摘要:

The large number of control devices which had been invented over the previous two centuries led, by about 1930, to the conception of a control theory with fundamental principles basic to all forms of control. The last war saw the use of this theory to develop sophisticated mechanisms of high precision. The paper gives the development of the science and engineering of control over the last 40 years. In engineering the increasing importance of the effects of nonlinearity is emphasised, and the spinoff resulting in unconventional electrical machines is described including the development of magnetic levitation. During this period control theory has also been introduced into a wide variety of other branches of knowledge. The greatest impact has probably been in medicine, with the body now being regarded functionally as a complex, dynamic control system. The heart-lung combination was eventually seen to be a ‘self-adaptive’ system, and the study had an effect on engineering design. Other areas described include sociology, economics and management. The basic tenets of the accuracy of measurement, the speed of measurement and ‘dead time’, well established in engineering, are shown to be equally fundamental in management and economics.

DOI:10.1049/ip-a-1.1985.0001

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper makes the claim that civilisation is founded on the work of engineers. It takes its title from the book of Ecclesiasticus, which speaking of craftsmen says that ‘by their work is the city established’. The paper argues further that management and design are the core of engineering. It gives the view that there is an organised framework of concepts and principles underlying both management and design and that these concepts and principles are closely linked. It illustrates this view by outlining some principles of systematic design methodology. It presents a model of the design process and highlights some components of the process: the establishment of objectives, the generation of design concepts and the taking of decisions. It concludes with the view that the advancement of the science of management and of design is one of the objectives of the IEE's Management & Design Division.

DOI:10.1049/ip-a-1.1985.0002

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Computer-aided engineering is an all-embracing term to cover the drawing together of all aspects of the design and manufacture of a product. CAE systems can now be purchased which can greatly assist the engineer in his efforts to produce a better, more competitive product in a shorter time. The introduction of CAE causes changes in the structure of a company. Human communication becomes vitally important. The CAE engineer requires a broad appreciation of a wide range of disciplines. Advanced CAE will mean the introduction of expert systems technology and the knowledge engineers to advise on its successful implementation. The fundamental point to grasp is that CAE is simply one more step in an age-old process in which we seek to better understand and model the physical world: ‘man is basically a model builder’.

DOI:10.1049/ip-a-1.1985.0003

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Stable electromagnetic levitation of spinning conducting cylindrical rotors has been demonstrated theoretically for the first time. General expressions of the quasistationary magnetic vector potential, for a rotating, conducting, cylindrical shell in the proximity of a distribution of parallel straight wires carrying currents, have been obtained by assuming a two-dimensional field. For a practical range of geometric and electric parameters of a thin cylindrical shell rotor, the static stability conditions, losses and torque/speed characteristics are quantitatively derived. Speeds of rotation of up to twenty thousand revolutions per second have been analysed. The results of this study can be applied to the design of electromagnetically levitated and driven rotors.

DOI:10.1049/ip-a-1.1985.0004

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper describes a method for the synthesis of the electrostatic field corresponding to the potential of boundaries of an unknown shape. The proposed algorithm makes it possible to determine the optimal boundary structure of the region where it is necessary to obtain a specified electrical field distribution. The main idea is based on the application of one of the regularisation methods for solving the ill-conditioned, under-determined algebraic system of equations resulting from the application of the finite-element method. Numerical calculations performed in an example demonstrate all the features of the proposed method.

DOI:10.1049/ip-a-1.1985.0005

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A method of employing space-periodic magnetoresistive transducers for the direct measurement of the speed of magnetic recording tape is described. The method is, in principle, similar to that devised for measuring strip speed in steel mills, using an inductive transducer. The wavelength-selective transducer is connected in a feedback configuration to an inductive write head placed upstream of the transducer, and the system records an ideally constant-wavelength pattern on the tape, so that the frequency of the transducer output is a direct measure of the tape speed. A digital variable delay line is used to compensate for slight variations in the recorded wavelength caused by variable phase delays encountered in the feedback loop. The error in the speed measurement is less than 0.1%. Three different experimental transducers are investigated, each of which is less than 2 mm long and utilises trackwidths of 100 μm or less.

DOI:10.1049/ip-a-1.1985.0006

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A substantial decrease in efficiency compared with the standard lightning impulse occurs in the production of very short-tailed lightning impulses by means of the Marx generator. A modification of one of the typical Marx circuit configurations, i.e. the series connection of a sphere gap and an inductance to the tail resistance, is suggested here to overcome this drawback. Digital simulation of the phenomena involved and extensive experimental work prove this solution to be suitable for the purpose.

DOI:10.1049/ip-a-1.1985.0007

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A method and boundary probe using an AC bridge as a sensor is described, by means of which the current densityJ, electric fieldE, conductivity σ and complex permittivity of an ionised gas may be determined at a point on its boundary. The probe itself is a three-terminal capacitor transformed into one flat plane, with typical diameters of 1 mm to 3 mm. Fitting flush with the electrode or vessel boundary, it has excellent positional discrimination because of its small size. Using a modern AF to RF transformer ratio bridge as the sensor, the several quantities may be measured to better than 5% for so lightly ionised a gas as a corona at NTP. The calibration is independent of space-charge density and carrier mobility. At low diagnostic frequencies below the relaxation frequencies for the ions or electrons under observation, the measurement essentially records DC values of σ,EandJ. The method is also suitable for use with electrolytes and powders.

DOI:10.1049/ip-a-1.1985.0008

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The theory of coherent shift-and-add imaging is summarised, is extended to be more generally applicable than in Parts 1 and 2, and is illustrated with the results of computer simulations and laboratory experiments. 2-dimensional images of collections of cylindrical objects (immersed in a water tank into which plastic containers filled with animal offal can be introduced) are reconstructed by shift-and-add (in both its elementary and extended forms) from wideband ultrasonic signals scattered over a wide angle.

DOI:10.1049/ip-a-1.1985.0009

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper is concerned with the assessment of the electrical environment in the vicinity of HVDC transmission facilities; the ion flow electrification phenomenon has been recognised as the subject of extensive research. The determination of current and electric field at ground level under the facilities and the estimation of electrification quantities on objects placed in an ion flow field is the basis of the design of conductor geometries. It has been found from measurements of current and field using the model-scale and full-scale transmission lines, that the current distribution at ground level is strongly influenced by wind, although the effect of wind on electrification quantities on an object placed in the ion-flow field is not understood in detail. In the present study, the electrification current and voltage on a cylindrical object placed in an air stream containing unipolar ions are estimated from analytical and numerical calculations, and the influences of wind, the leakage resistance and the object arrangement on the ion trajectory and electrification quantities are discussed.

DOI:10.1049/ip-a-1.1985.0010

出版商:IEE    

年代:1985

数据来源: IET