Control system feedback

Other Considerations in Feedforward Control The tuning of feedforward and feedback control systems can be performed independently. In analyzing the block diagram in Fig. 8-32, note that Gy is chosen to cancel out the effects of the disturbance Us) as long as there are no model errors. For the feedback loop, therefore, the effects of L. s) can also be ignored, which for the sei vo case is ... 

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... 

Moderate to microproces.sor-based, fully programmable logic controls and feedback control systems are available, to provide smooth speed controls as good as a.c. drives... 

Figure 8.9(b) A general scheme illustrating speed control by feedback control system using an eddy current coupling... 

The AVR may be designed for variable duty, for automatic control of the reactive power, to the required level through feedback control systems. The machines will now operate only as synchronous condensers without performing any mechanical duty. 

In SVCs Ihe number of switchings is of no relevance, as they arc free from inrush currents. Switching is performed at the instant when the cuiTcnt wave is passing through its natural zero. Static devices in various combinations and feedback control systems, which may be computer-aided, can tilmost instantaneously (< I cycle) generate or absorb reactive power, as may be demanded by the system. Correction... 

A few TCRs to balance the reactive power supply. They may generate harmonics, which must be suppressed to avoid any resonance. T.SCs and TCRs are monitored through a feedback control system,... 

Any system in which the output quantity is monitored and compared with the input, any difference being used to actuate the system until the output equals the input is called a closed-loop or feedback control system. 

The closed-loop transfer function for any feedback control system may be written in the factored form given in equation (5.41)... 

Figure 9.18 shows a classical feedback control system D s) is a disturbance input, N s) is measurement noise, and therefore... 

A unity-feedback control system has a nominal plant transfer function... 

The use of hydraulic systems for the setting, operation and control of machine tools has increased significantly. Hydraulic mechanisms being inter-linked with electronic controls and/or feedback control systems. In machine tools, hydraulic systems have the advantage of providing stepless and vibration-less transfer of power. They are particularly suitable for the linear movement of tables and slideways, to which a hydraulic piston may be directly coupled. 

Design of injection molding equipment to produce car bumpers made from polymers Designing feedback control systems for bioreactors... 

Operating near the washout point maximizes the production rate of cells. A feedback control system is needed to ensure that the limit is not exceeded. The easiest approach is to measure cell mass—e.g., by measuring turbidity— and to use the signal to control the flow rate. Figure 12.5 shows how cell mass varies as a function of t for the system of Examples 12.7 and 12.8. The minimum value for t is 2.05 h. Cell production is maximized at F=2.37h. 

Example 14.1 shows how an isothermal CSTR with first-order reaction responds to an abrupt change in inlet concentration. The outlet concentration moves from an initial steady state to a final steady state in a gradual fashion. If the inlet concentration is returned to its original value, the outlet concentration returns to its original value. If the time period for an input disturbance is small, the outlet response is small. The magnitude of the outlet disturbance will never be larger than the magnitude of the inlet disturbance. The system is stable. Indeed, it is open-loop stable, which means that steady-state operation can be achieved without resort to a feedback control system. This is the usual but not inevitable case for isothermal reactors. 

Computer-Based Laboratory for Developing Practical Automated Feedback Control Systems for Batch Polymerizations... 

The batch process control system we ve purchased provides only a starting point for our process research lab we must also identify and test a comprehensive set of controlled devices and real-time process instruments for chemists and engineers to use as building blocks for real feedback control systems. The technologies we are evaluating for characterization of polymer batches at all process stages include ... 

Automated feedback control systems for batch polymerizations advantages, 475... 

Obviously, regulation of food intake depends on many neurotransmitters and hormones but this final section will outline the role played by central 5-HT transmission in this process. It had been the belief for some time that increased 5-HT transmission in the brain reduces food intake (Blundell 1977) and this certainly explains the satiety in rats that follows infusion of 5-HT into the paraventricular nucleus (PVN) of the hypothalamus. However, recent studies using microdialysis have found that 5-HT efflux in the lateral hypothalamus is itself increased by food intake, suggesting the existence of a feedback control system. In fact, because the increase in 5-HT efflux is greater in genetically obese rats than in their lean counterparts, it has been proposed that there is a deficiency in the 5-HT inhibition of food intake in obesity. 

Figure 2.29. Block diagram of a feedback control system.

The simple feedback control system below consists of a continuous-flow stirred tank, a temperature measurement device, a controller and a heater. 

We use a simple liquid level controller to illustrate the concept of a classic feedback control system.1 In this example (Fig. 5.1), we monitor the liquid level in a vessel and use the information to adjust the opening of an effluent valve to keep the liquid level at some user-specified value (the set point or reference). In this case, the liquid level is both the measured variable and the controlled variable—they are the same in a single-input single-output (SISO) system. In this respect, the controlled variable is also the output variable of the SISO system. A system refers to the process which we need to control plus the controller and accompanying accessories such as sensors and actuators.2... 

Figure 10.4. (a) A feedforward-feedback control system, (b) The diagram after moving G vGp. 

Figure 8 Feedback Control System Block Diagram. 9...

Figure 8 shows basic elements of a feedback control system as represented by a block diagram. The functional relationships between these elements are easily seen. An important factor to remember is that the block diagram represents flowpaths of control signals, but does not represent flow of energy through the system or process. 

Three-way catalysts are able to reduce NO as well as oxidize CO and hydrocarbons when the exhaust composition is held near the stoichiometrically balanced composition, or "stoichiometric point." This control of exhaust composition is accomplished, after the initial warmup period, through the use of the feedback control system illustrated in Figure 1 (2, 3, 4). ... 

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