Microprocessor-based control technology

With this technology it is now possible to achieve extremely accurate speed control of the order of 0.01 % to 0.001 %. To achieve such high accuracy in speed control, closed-loop feedback control systems and microprocessor-based control logistics can be introduced into the inverter control scheme to sense, monitor and control the variable parameters of the motor to very precise limits. 

Since the 1970s, process controls have evolved from pneumatic analog technology to electronic analog technology to microprocessor-based controls. Electronic and pneumatic controllers have now virtually disappeared from process control systems, which are dominated by programmable electronic systems based on microprocessor technology. 

Microprocessor technology permitted these technical issues to be addressed in a cost-effec tive manner. In the mid-1970s, a process control architecture referred to as a distributed control system (DCS) was introduced and almost instantly became a commercial success. A DCS consists of some number of microprocessor-based nodes that are interconnec ted by a digital communications network, often called a data highway. The key features of this architecture are as follows ... 

The rapid development of microprocessor technology has made distributed control possible and attractive. The use of reliable communication between a large number of individual controllers, each responsible for its own tasks rather than for the complete operation, improves the response of the total system. We can take PLC-based control as a typical example of central control system and LonWorks, developed by Echelon, as an example of distributed control system. In Lon Works, each automated device is controlled by a control module—LTM-IO (Figure 8). The control modules are connected on a LonTalk network that provides an ISO/OSI compatible protocol for communication. 

Both the IE I C systems (Protection and Safety related monitoring) and the control systons (characterized by the absence of control rods and by the "hot-cold" interface regulation inside the Density Locks) are designed utilizing a proven, distributed microprocessor-based technology. An advanced control room, vrith a wall panel information station and work stations for operators and supervisor is foreseen, taking into account the most recent achievements and improvements in the man-machine interface systems. 

In 1975, the PAR Model 374 Polarographic Analyzer was introduced, at a price of 9500. This instrument employed a 16-bit microprocessor to control acquisition and analysis of data. During data collection, scale expansion and autoranging were automatic, and invalid data points could be rejected by comparison with pre-set criteria. In the PLAYBACK mode, the entire curve was reread and plotted on the recorder, with all peaks on scale. If desired, baseline and background corrections were measured, and concentrations calculated from pre-set standards. This was the first pulse voltammetric instrument designed around a microprocessor. Like the Southern Analytical pulse instrument based on vacuum tube technology, it came a bit too soon, before the technology (or the customer) was quite ready. 

Silicon is the most technologically important material utilized today owing to its imique role in the fabrication of semiconductor devices and microprocessor chips. The understanding and control of silicon surfaces is of great importance in the production of silicon-based electronic devices, since the fraction of atoms... 

Measurement Devices and Final Control Elements This lowest layer couples the control and information systems to the process. The measurement devices provide information on the current conditions within the process. The final control elements permit control decisions to be imposed on the process. Although traditionally analog, smart transmitters and smart valves based on microprocessor technology are now beginning to dominate this layer. 

More recently, the applications for silicon now include electronics. A silicon-based device is found in almost every consumer product available in our world today. Even refrigerators now have extensive microprocessor controls, some fitted with television screens The popularity of flat-panel televisions has also employed silicon-based technology, especially for thin-fllm transistor liquid crystal displays (TFT LCDs). In addition to electronics, as the world looks for alternative sources of energy due to dwindling petroleum reserves, silicon-based photovoltaic devices will represent an increasingly important application for our society. 

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