Browsing by Author "Rodd, M G"

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    A high level disc controller
    (1979) Feyder, Barry; Rodd, M G
    Since the emergence of the digital computer in the 1940s, computer architecture has been largely dictated by the requirements of mathematicians and scientists. Trends have thus been towards processing data as quickly and as accurately as possible. Even now, in the age of large scale integration culminating in the microprocessor, internal structures remain committed to these ideals. This is not surprising since the main users of computers are involved with data processing and scientific computing. The process control engineer, who turned to the digital computer to provide the support he required in his ever increasing strive towards automation, has had therefore to use these generalized computing structures. His basic requirements however, are somewhat different to those of the data processing manager or the scientific user. He has to contend with an inherent problem of synchronizing the computer to the real-world timing of his plants. He is far more interested in the response time of the computer to an external occurrence than he is to sheer 'number-crunching' power. Despite the trends in process control towards distributed computing, even the most advanced systems require a relatively large central processor. This processor is called upon to carry out a wide variety of different tasks most of which are 'requested' by external events. Multiprogramming facilities are therefore essential and are normally effected by means of a real-time operating system. One of the prime objectives of such a real time operating system is to permit the various programs to be run at the required time on some priority basis. In many cases these routines can be large - thus requiring access to backing storage. Traditionally the backing store, implemented by a moving-head disc for example is under the control of the real-time operating system. This can have serious consequences. If real-time requirements are to be met, transfer to and from the disc must be made as rapidly as possible. Also, in initiating and controlling such transfer, the computer is using time which otherwise could be avai1ab1e for useful, process-orientated work. With the rapid advancement of digital technology, the time is c1ear1y right to examine our present computer architecture. This dissertation explores the problem area previously discussed - the control over the bulk storage device in a real-time process-control computer system. It is proposed that a possible solution lies in the development of an intelligent backing-store controller. This essentially combines the conventional low-level backing store interface with a special purpose processor which handles all file routines. This dissertation demonstrates how such a structure can be implemented using current technology, and will evaluate its inherent advantages.
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    A microprocessor based weighing and feed control system
    (1975) Potgieter, J H; Rodd, M G
    This paper describes the development of a micro-processor based computer control system for the raw material weighing and feed system of a submerged arc ferro-alloy furnace. The system is designed to replace the more conventional semi-automatic analogue controller at present in use in many installations. It may be used either as a stand-alone unit or as an out-station in a distributed control computer-based system. In the latter, the micro-processor unit forms an intelligent peripheral to the central control computer.
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    Slurry flowmetering using correlation techniques
    (1979) Leitner, Johann Robert; Rodd, M G
    A review of slurry flowmeters leads to the conclusion that most are unsuited for measuring the flowrate of abrasive and corrosive slurries such as are found in the gold mining industry in South Africa. An alternative flowmeter based on cross-correlation techniques is thus proposed. Random signals generated by the flowing fluid are measured at two points a known distance apart in the direction of the flow. Assuming that this distance is not "too" large, the downstream signal is a time-delayed replica of the upstream signal. This delay equals the time it takes flow discontinuities to travel between the two measuring locations and can be obtained by cross-correlating the two flow signals and finding the position of the correlation peak. An analysis to establish a theoretical-basis for the method is performed and an attempt is made to model the flowmeter consisting of the two transducers a known distance apart. A review of transducers for converting time-varying spatial flow patterns into electrical signals is undertaken and leads to ultrasonic transducers being chosen as most suitable for slurry flowrate measurements. Such transducers are non-intrusive and can be of a clamp-on type. The characteristics and requirements of ultrasonic transducers for correlation flowmetering are investigated and a suitable clamp-on design is described.