Transactions of the Institute of Measurement and Control

Tou, S.K.W.; Liu, C.Y.; Ng, K.L.

doi: 10.1177/014233128801000201pmid: N/A

An alternative design of twin-wire resistance probe manometer uses air trapped in one manometer tube to permit differential pressure measurements. The paper investigates the effects of initial size of trapped air pocket and its thermodynamic properties on the performance of the manometer, and suggests a calibration curve.

Dodds, S.J.; Milne, P.A.

doi: 10.1177/014233128801000202pmid: N/A

A simple and easily implemented method is presented here for automatic on-board estimation of a critical parameter of the control jet (thruster) impulse transfer characteristic. This facilitates optimal control with regard to thruster lifetime, fucel consumption and pointing accuracy, despite uncertainties in the thruster performance, The new estimator facilitates automatic, in-orbit adaptation of the attitude control system to slow changes in the control jet characteristics, thereby maintaining optimal performance.The parameter estimator is intended for microprocessor implementation and assumes the use of a state estimator. Attention is restricted to a single, isolated axis. No difficulty is envisaged in developing the technique further to cater for three-axis stabilised spacecraft with significant inter-axis couplingThe parameters to be determined are the intercepts on the characteristics of each control jet relating the actual jet firing time to that demanded.A mismatch in these parameters gives rise to a state estimator transient following a jet firing. This provides the stimulus to the parameter estimator, which is basically a resettable pure integrator. The intercept estimate is updated by an amount proportional to the integral of the state estimator error taken over a finite period, commencing at the beginning of the jet firing. Suitable choice of the gain of proportionality yields dead-beat parameter estimation.Besides compensating for jet firing time mismatch, the control system is shown to be capable also of compensating for uncertainties in the thrust level for short turn-on times.

Chiu, P.C.; Leung, T.P.

doi: 10.1177/014233128801000203pmid: N/A

A mathematical model is proposed for a low-pressure experimental pneumatic servomechanism which exhibits hysteresis characteristics at the torque motor and the servo spool valve assembly, nonlinear mass flow through the spool valve opening, and friction at piston and rod-end seals. Systems parameters are determined experimentally and correlated empirically. A single-board microcomputer is used for both servomechanism control and data acquisition purposes. The model predicts the experimental responses of three control algorithms with good accuracy. In particular, the response of PD with hysteresis compensation control shows no overshoot and minimal steady-state error when a step change of reference input is applied.

Flood, R.L.

doi: 10.1177/014233128801000204pmid: N/A

The essence of this paper recommends some major shifts in emphasis and approach, away from the scientific base of traditional systems science (as exemplified by traditional measurement and control methods) toward interpretive, subjective methods, when context relates to social situations. Radical change in place of regulation will also be discussed. This paper is equally a review paper, in that an historical overview is necessarily taken, and the development of systems science is traced therefrom. Particular attention is paid to systems in organisation theory and so-called problem solving'.

Bumby, J.R.; Masding, P.W.

doi: 10.1177/014233128801000205pmid: N/A

This paper describes the design and development of a test-bed facility for hybrid internal-combustion-engine/battery-electric vehicle power trains. The control hierarchy within the microprocessor control systems is discussed, and the influence this has on the software design is described. The instrumentation and computer software systems necessary for both data acquisition and drive train control are described. It is shown that drive train control over an urban cycle can be successfully achieved using a modified proportional-plus-integral controller.

Huang, S.M.; Xie, C.G.; Stott, A.L.; Green, R.G.; Beck, M.S.

doi: 10.1177/014233128801000206pmid: N/A

Electrostatic charge generated in solids/air two-component flows can cause significant errors in solids-concentration measurement systems based on capacitance techniques, and, in the worst case, can overload or even damage the measuring circuits. A transformer ratio-arm bridge capacitance transducer, incorporating synchronous demodulation and a noise attenuating input amplifier, has been developed for this type of application. The transducer has been tested on several solids-flow plants. It shows a very high immunity to charge interference and it is capable of withstanding large magnitudes of electrostatic interference without being overloaded.

Postlethwaite, I.; O'Young, S.D.; Gu, D.-W.

doi: 10.1177/014233128801000207pmid: N/A

Stable-H is a CAD package for designing H∞ optimal controllers for linear, time-invariant finite-dimensional continuous-time, multivariable systems. H2 (eg, LQG) optimal controllers can also be designed but the main purpose of Stable-H is H∞design. The name Stable-H was coined because the package optimises, over the set of all stabilising controllers, the H∞ or H2norm of a given cost function. In this paper we will describe the important features of Stable-H and give an example of its application.

Atherton, A.

doi: 10.1177/014233128801000208pmid: N/A

A calibration exercise provided a preliminary investigation into the compatibility with IPTS-68for temperatures below 0°C of thermometers with low temperature coefficients. Further data, obtained for temperatures up to 300°C, support a previous hypothesis that divergence from the IPTS-68 is largely a result of stem-heat-transmission errors.