Closed-loop feedback control

Technology has been introduced for on-line estimation of the kappa number based on absorption of ultraviolet light (35). This breakthrough ia optical sensor technology permits closed-loop feedback control of digesters from on-line measurement of the kappa number. 

With years of research and development in the field of static drives, it is now possible to identify and separate the.se two parameters (f, and /, ) and vary them individually, as in a d.c. machine, to achieve extremely accurate speed control, even slightly better than in d.c. machines. In d.c. machines the armature current and the field strength arc also varied independently. A.C. machines can now be used to provide very precise speed control, as accurate as 0.001% of the set speed, with closed-loop feedback controls. This technique of speed control is termed I ield-oriented control (FOC) and is discussed below. 

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. 

Very accurate controls through microprocessor-based closed-loop feedback control systems... 

The dynamic behavior of industrial unit 1 is studied in this section. The steady-state behavior of unit 1 has been studied previously. Both open-loop and closed-loop feedback controlled configurations will be presented. 

Therefore, considerable efforts were made on deposition in the transition mode of the reactive magnetron discharge, where nonstable conditions are used and where closed-loop feedback control is mandatory for process stabilization. 

Olkkola KT, Tammisto T. Quantifying the interaction of rocuronium (Org 9426) with etomidate, fentanyl, midazolam, propofol, thiopental, and isoflurane using closed-loop feedback control of rocuronium infusion. Anesth Analg 1994 78(4) 691-6. 

The instrument may contain closed-loop feedback control (automated) features. The temperature of the reaction chamber may be controlled for kinetic measurements. An automatic titrator may sense the approach of an end point and slow down the addition of titrant near the end point for improved precision in locating the end of the titration, just as a human operator would, but-probably in a more reproducible fashion. The instrument may monitor its various functions and shut itself down if it malfunctions. 

Suppose the design of the engine conld be snbstantially improved snch that k conld be reduced to say 0.1 (approaching a valne for a typical closed-loop feedback controlled system). Table 2.5 shows comparable results to those given in Table 2.4. 

The torque produced by the motor is therefore reduced in proportion to the square of the rms value of the applied voltage. Circuits are available for both star and delta connected motors. Closed loop feedback control may be used to adjust the firing of the thyristors, thereby making accurate speed regulation possible. These systems are only used for small machines, e.g. up to 20 kW because they tend to produce many harmonic currents and voltages in the supply. 

Murray, C. J., Closed-Loop Feedback Controls Web Tension, Design News, pp. 82-83, Dec. 1988. 

A more general form for the closed loop (feedback) controlled process can be drawn as in Figure 5.41. 

The most important and challenging problems in active and passive stmctural control systems are the formulation and solution of optimal control and nonlinear constrained optimization needed to develop appropriate closed loop feedback control algorithms and the optimal placement, which is the central focus of this book. State-of-the-art techniques for optimal design of passive and active control systems are described in detail in various chapters written by researchers aroimd the world. I welcome this new book for offering a very good overview of the current developments in the field. 

Urea injection parameters are determined by NOx quantity in the exhaust (concentration and flow rate), temperature, and the amount of ammonia stored in the catalyst. There is normally closed-loop feedback control using an NOx sensor at the SCR exit, and in many applications, an NOx sensor is used upstream to determine inlet NOx levels. 

Models can often be used to guide the designed experiments that need to be run on the commercial process as part of the qualification effort. Out of this activity come the aims and limits of the process variables, which either directly or indirectly are under closed-loop feedback control and some of which are then monitored by statistical process control techniques (Ref 2). 

Injection Machine Barrel Design Each heated zone of the barrel (feed, transition, metering) should be controlled independently and should provide for accurate closed-loop feedback control. A bimetalUc barrel is recommended (an abrasive resistant carbide particle liner material inside an alloy steel outer shell). 

The addition of salt, acid, base or other appropriate chemicals to change the ion activity and control equilibrinm (exhanstion) can be done continuously in response to a pre-set program, or, through conductivity and pH measnrements, by closed-loop feedback control. 

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