Transactions of the Institute of Measurement and Control

Jaworska, I.; Finkelstein, L.

doi: 10.1177/014233129101300401pmid: N/A

This paper deals with the robustness problem of control systems; some robust stability measures in time and frequency models representations are quoted and their practical usefulness is discussed from the point of view of measurement theory.

Pyle, E.A.

doi: 10.1177/014233129101300402pmid: N/A

This paper considers the task of an optimal tools setting for a machining centre (MC) to allow a reduction in time spent in the resetting of tools from one batch of workpieces to another. A theoretical relationship drafted is in full agreement with findings gained as a result of analysis of some 15 000 workpieces. A three-dimensional representation of an optimal tools setting is offered. A definition of an optimal tools setting is given, valid for any type of machine-tool.

Gelaky, R.; Keating, D.

doi: 10.1177/014233129101300403pmid: N/A

Over the last 12 years, consistent effort has been directed toward the development of a usable sense of touch for machines. This research has been somewhat overshadowed by the ongoing development in artificial vision, but has remained important for specialised object identification applications. Over the aforementioned period, a great number of different transduction and measurement principles have been adopted, each claiming to offer certain desirable characteristics. The last five years have shown a reduction in the variation of methods being pursued.One of the main surviving transduction methods is based upon the variable-separation capacitive transducer. The method of capacitance measurement, adopted by two major American research teams developing such sensors, has been a simple charge amplifier. Their measurement methodology has limited the spatial resolution, or inter-tactel separation, and slowed the acceptance of an otherwise near ideal taction device.This paper describes the development, a design model and subsequent construction, of a variable-separation capacitive tactile system which employs an improved measurement system. The system permits the sensor spatial separation to be reduced to the limits of the physical construction method and no longer be confined by the measurement technique. This will, it is hoped, lead to the construction of larger, more densely packed, arrays capable of low-cost, efficient object recognition. The sensor performance, possible applications and intended direction for further research are also discussed.

Pears, N.E.; Bumby, J.R.

doi: 10.1177/014233129101300404pmid: N/A

Experimental results relating to the steering control system of an experimental autonomous vehicle operating in a pre-defined and structured environment are presented. A method of steering control is formulated which relates second-order criteria, such as rise time and damping factor, to the parameters of the control system. With the control system described, the vehicle can track a path of constant heading with very little steady-state error and, if the control parameters are chosen in the correct ratio, it will respond in a critically damped fashion to the step disturbances which are generated by position corrections. For a curved path, demand curvature is treated as an input to the system in order to eliminate steady-state offset errors in tracking. In order to make the vehicle's performance independent of velocity, control parameters are derived as simple functions of velocity. This has the effect of allowing the vehicle to manoeuvre more tightly at lower speeds, and makes use of the increased availability of drive-system torque at such speeds. In order to prevent stalling of the stepper-motor drive system at large changes in demand curvature, a method of limiting the rate of steering is described.

Richards, R.J.; Reay, D.S.

doi: 10.1177/014233129101300405pmid: N/A

As an initial step in a programme to test VSS controllers on robot arms, the VSS control strategy is applied to a single link and revolute joint. Experimental results demonstrate the successful use of this type of control and indicate the advantages to be gained by some of its suggested modifications.

Liu, C.Y.

doi: 10.1177/014233129101300406pmid: N/A

A precision twin-wire resistance-probe manometer has been developed for the purpose of measuring very low differential pressure. From the extensive performance tests conducted, it was found that the output voltage from the manometer is linearly proportional to the difference in pressure. Several ranges of calibration were made; the accuracy of the output depends upon the range and sensitivity setting of the manometer. For the range of 0-0.2 mm of water with a sensitivity setting of 1000 mVlmm, the accuracy of ±0.02 Pa (about ± 0. 002 mm of water) was achieved.

Endean, V.G.

doi: 10.1177/014233129101300407pmid: N/A

A novel adaptive procedure for stabilising certain types of non-linear, time-varying, discrete system is described. Its application to one-dimensional unimodal systems, which are particularly important in the dynamic modelling of biological populations, is illustrated. An unusual feature is that the controlled system automatically locates a natural equilibrium state, as opposed to being driven to a pre-defined set point. This has the important advantage in the control of biological populations of minimal interference with the system. Robust equilibrium is maintained, not only in the period-doubling and chaos regions, but also deep into the catastrophically unstable extinction region.

Xiaoping Yun, ; Daizhan Cheng,

doi: 10.1177/014233129101300408pmid: N/A

The problem of input-output decoupled linearisation of a general non-linear system = f(x, u), y = h (x) is studied. By defining an affine approximation, the solution of this problem is related to the established results of affine non-linear systems. An algorithm is given to compute the non-linear feedback for input-output decoupled linearisation. Under the standard assumptions, a condition for feedback stabilisation is also obtained.