A reduced order self-tuning controllerGoodhart, S.G.; Burnham, K.J.; James, D.J.G.
doi: 10.1177/014233129101300102pmid: N/A
As industrial users attempt to control systems exhibiting fast dynamic response characteristics, the demand for higher sampling rates and hence rapid controller calculations is becoming more apparent. This problem is compounded when considering the application of self-tuning control to non-linear systems exhibiting such characteristics, where, in order to maintain integrity of the self-tuner, enhanced estimation algorithms with increased computational complexities are required. In this paper a reduced order state-space self-tuning controller is proposed and its performance is compared by simulation studies to that of a standard implicit delay state-space self-tuning scheme. Whilst the same control objectives are achieved in a compatible manner it is shown that the reduced order scheme is significantly less computationally intensive and, as such, reduces the effects of computational delay in the overall closed-loop self-tuning scheme.
A self-learning fault-diagnosis systemZhang, J.; Roberts, P.D.; Ellis, J.E.
doi: 10.1177/014233129101300104pmid: N/A
This paper describes a self-learning fault-diagnosis system which can find any inappropriate settings of its parameters and, hence, improve its own performance. It diagnoses faults based on a deep qualitative model of the process being monitored. From this qualitative model, the expected behaviour of the process can be generated and, if it differs from the actual one, then it is perceived that a fault (or faults) occurs in the process. The diagnosis of sensor failures is based on a set of heuristic rules, while the other component failures are diagnosed by comparing the expected behaviour under a hypothesis with the actual one. The inappropriate settings of any threshold values, for converting quantitative values to qualitative values and for determining symptoms in the perception of sensor failures, are considered as a major reason for failures in diagnosis. Once such a failure occurs, the diagnosis system will inspect itself and find any inappropriate parameters. This is achieved by examining the recorded problem-solving history and performing backwards tracing through the model of the fault-diagnosis system. The expected output of the fault-diagnosis system is propagated backwards through this model. Any threshold values which are responsible for not giving the expected output are examined, and the inappropriate parameters are found. This self-learning fault-diagnosis system has been implemented in an expert systems shell: EXTRAN, and is applied to a pilot-scale mixing process.
An adaptive time-of-flight anemometerTatnall, M.L.; Sodhi, C.
doi: 10.1177/014233129101300106pmid: N/A
It is shown that the frequency of operation of self-oscillatory flowmeters fails to provide an absolute measure of fluid-flow velocity. A technique is described which makes use of the signals generated in a self-oscillatory system as adaptive markers for use in a time-of-flight method of flow measurement able to operate over a wide range of flow velocities. Experimental results are shown illustrating the operation of the device.
Predictive criteria for the optimisation of a vibrating-reed transducerMahgerefteh, Haroun; Al-Khoory, Hassan
doi: 10.1177/014233129101300107pmid: N/A
The optimisation of a vibrating-reed technique which is capable of measuring various properties such as fluid pressure, density, viscosity and mass under aggressive environments is described. The unit operates simply by utilising a stiff reed which is clamped securely at an intermediate point along its length. One end, mounted with an inert concentrated mass is exposed to the test environment, while the other is mechanically excited so that the system is sinusoidally vibrated at its first modal resonant frequency. Changes in the resonant conditions then reveal information about the physical properties of the fluid under test. The finite-element method of analysis adopted for a cylindrical reed reveals that optimum operating conditions in terms of output response are achieved with maximum reed diameter, minimum reed length and minimum mass ratio of the attached mass to that of the reed. The stability criteria on the other hand indicate that most stable operation corresponds to the clamping of the reed as far away as possible from its centre. The analysis also considers the effect of choosing different reed materials and shapes on the system's resolution and sensitivity. Most of the theoretical predictions are also confirmed by experimental evidence.