Transactions of the Institute of Measurement and Control

O'Connor, B.

doi: 10.1177/014233128901100301pmid: N/A

A method involving a computer is described for selecting resistors for precise analogue instrument circuits. A statistical analysis is carried out which provides formulae for calculating the probability of non-duplication of resistors, and also the predicted discrepancy for specified group and batch sizes. Theoretical and actual values are compared: the agreement is such that the theoretical formulae can be used confidently to specify batch sizes to obtain indicated discrepancies for given group sizes. The method is of practical importance in selecting closely matched resistor ratios, and matched resistors, for precise analogue circuits.

Coates, Prof R.; Cheung, K.Y.; Mathams, R.F.

doi: 10.1177/014233128901100302pmid: N/A

This paper describes the design and performance of a digital filter basfd upon the FAD (Filter And Detect) integrated circuit. Although the filter was initially devised to provide economical and flexible processing for low-and medium-frequency sonar system testing, simulation and signal processing, it may also be applied to a wide range of fixed-parameter or time-variable filtering tasks in the frequency band to 40 kHz.

Bailey, W.N.; Abdullah, F.

doi: 10.1177/014233128901100303pmid: N/A

A computer package MEDIEM (Multi-Energy-Domain-Interactive-Element-Modelling) has been developed for the purpose of interactive modelling of multi-energy domain systems. Model entry is effected interactively, using a mouse, by drawing a 'structure graph' from a set of defined elements in a fixed menu display. This allows rapid and efficient model development from which time and/or frequency-response information can be displayed. The package can be applied to mechanical, electrical, thermal and fluid systems (inclusive of energy conversion) provided that they can be treated on a lumped parameter basis. The paper illustrates the features of MEDIEM by way of simple examples covering electrical circuits, hydraulically coupled tanks, a vehicle suspension system, an electro-mechanical vibrator and two feedback control systems.

Al-Assadi, Salem A. K.; Marouf, Azzam A.

doi: 10.1177/014233128901100304pmid: N/A

A computer-aided method for the computation of optimal discrete models with reduced orders for control systems is presented in this paper. The method used for simplification utilises a time-domain-optimisation technique to search for optimum values for the parameters of prespecified reduced-order discrete-time models for control systems. The measure of success of simplification is taken to be the minimum integral squared error between the step responses of the simplified discrete-time models and that of the actual system at sampling instants. Two examples are considered to illustrate the usefulness of the method in simplifying control systems given in various forms. One of the examples considered was to obtain reduced-order discrete-time models for a fourth-order Butterworth filter. The method proved to be powerful in finding the optimal discrete models with reduced orders for both short and long sampling periods.

Sharp, J.M.; MacCarthy, B.L.; Burns, N.D.

doi: 10.1177/014233128901100305pmid: N/A

This paper describes the development of sensitive transducers to measure dynamically forces associated with the interaction of cams, needles and yarn in the weft knit process. The design principles of cam and yarn force transducers are discussed and their integration into a microcomputer-based control system is described. The experimental results demonstrate the range of application and the sensitivity of the transducers. The transducers were particularly important in validating theoretical models of the system and highlighting their deficiencies. The system provides the basis for the development of future test and control instrumentation on this type of machinery.

Takahashi, Yoshihiko; Takahashi, Atsushi

doi: 10.1177/014233128901100306pmid: N/A

A linear driving technique with a small degree of wobbling for an optical disc cutting machine is discussed. The track-pitch in the order of one micrometre causes low-velocity linear driving, by means of which the stage holding the exposure optics is carried in the disc radius direction, while the disc is rotating. In order to obtain low velocity, a calculating technique using the displacement output from a laser interferometer was adopted. A voice-coil motor drove the moving part directly as an actuator, and, for maintaining the accuracy of the calculated digital velocity, a digital state-variable feedback control was applied. This paper describes the main features of the mechanical system and its mathematical model in the form of a pulse transfer function, the low-velocity detection using a laser interferometer and the stability of the laser interferometer, the digital state-variable feedback control, and the simulation and experimental results. Finally, a small amount of wobbling, less than ± 0.13 μm with 80 μm/s velocity was achieved, and the validity of the proposed technique was confirmed.

Whitehead, D.G.; Fleming, A.R.; Bell, I.M.; Pugh, A.; Sweeting, P.

doi: 10.1177/014233128901100307pmid: N/A

Check weighing of products during manufacture is required frequently. Commonly, these products are to be weighed while moving through the manufacturing process. This paper describes a method for capturing the weight of such products 'on the fly' using digital filters to extract the signal from the high ambient noise. A repeatability of better than ±0.3% in weight acquisition can be obtained by this approach.