Microprocessor-based control systems

Moderate to precise controls as for a.c. drives possible with the use of microprocessor-based control systems... 

Microprocessor-based control systems are being increasingly used in place of traditional instrumentation. Some accidents that have occurred on these systems are described in Chapter 20. 

Manufacturers now offer as standard microprocessor-based control systems as part of their gas turbine generator set. The set can therefore be controlled and monitored from panels adjacent to the machine or, if required, remotely from a central control room. In combined-cycle installations, the system would be linked into the... 

Multistep batch processes are amenable to microprocessor-based control systems. Porte et al. (1982) have shown that the seven-step process for making (1-ethyl-2-pyrrolidinyl) (2-... 

The sterilization process is controlled by the microprocessor-based control system. Temperatures and pressures are measured from the chamber... 

Microprocessor-based control systems are marketed under a variety of acronyms and not all will be true DCCSs. Of particular note are the Supervisory Control and Data Acquisition (SCADA) systems which form an increasingly central part of the operations of many industries (e.g. offshore oil and gas platforms, petrochemical complexes, pulp and paper works). SCADA describes a communications system whose principal function is to join instrumentation and control into a cohesive package(57) and, particularly, the supervision and management of remote ... 

Barker and Christie described a microprocessor-based control system for the control of textile drying processes [33]. In addition to the control of the dryer outlet moisture content, the computer-based system was used to optimize the energy use of the dryer. 

Microprocessor-based control system had also been implemented in a solar-tunnel dryer [35] and a pneumatic drum dryer [36],... 

FIGURE 57.11 Control system C for industrial spray dryers (a) outlet-temperature control with feedback from moisture content measurement (b) microprocessor-based control system. 

PSA systems are moderately reliable. The numerous valves associated with the process can cause unexpected shutdowns. The new PSAs are designed with alternate modes of operation, in which 100% of design capacity can be achieved while bypassing any failed valve or instrument, with only a slight loss of recovery. Failures are automatically detected and bypassed by the microprocessor-based control system. However, stronger and periodic control cycles are required. 

Reliability takes into account the on-stream factors which can cause unscheduled shut-downs. Membrane systems are extremely reliable with respect to the on-stream factor. The membrane separation process is continuous and few control components can cause a shut-down. Typically, the response to unscheduled shut-downs is rapid for GS whereas PSA systems are moderately reliable owing to the numerous valves associated with the process which can cause unexpected shut-downs. The new PSA are designed with alternative modes of operation, in which 100% of design capacity can be achieved while by-passing any failed valve or instrument, with only a slight recovery loss. Failures are automatically detected and by-passed by the microprocessor-based control system. Flowever, stronger and periodic control cycles are required. The cryogenic process is considered by refiners to be less reliable than PSA or membrane... 

Zilog in July 1976 introduced the Z-80, which was intended to be an improved 8080. It also used 8-b data and 16-b address, could execute all of the opcodes of the 8080 and added 80 more instructions. The register set was doubled and consisted of two banks, which could be switched. Two index registers (IX and lY) allowed for more complex memory instructions. Probably the most successful feature of the Z-80 was its memory interface. Until its introduction, dynamic random-access memory (RAM) had to be refreshed with rather complex external circuitry, which made small computing systems more complex and expensive. The Z-80 was the first chip to incorporate this refreshing capability on-chip, which increased its popularity among system developers. The Z-8 was an embedded processor similar to the Z-80 with on-chip RAM and read-only memory (ROM). It was available in clock speeds to 20 MHz and was used in a variety of small microprocessor-based control systems. 

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