While-loop control

More microprocessor-based process equipment, such as smart instruments and single-loop controllers, with digital communications capability are now becoming available and are used extensively in process plants. A fieldbus, which is a low-cost protocol, is necessary to perform efficient communication between the DCS and these devices. So-called mini-MAP architec ture was developed to satisfy process control and instrumentation requirements while incorporating existing ISA standards. It is intended to improve access time while... 

The vectors X and Xo contain the state variables and the initial conditions vector, respectively, while Y)0 and Kc represent the bifurcation parameters for the open loop (uncontrolled, Kc = 0) and the closed loop (controlled, Y 0 = constant) systems, respectively, and f = t/eiiR-The column vectors X and Xo are... 

The base case and three alternatives were evaluated by controllability analysis [7, 8], firstly at steady-state. The conclusion is that the loops Q2 (reboiler duty) -1, and SS2 (side-stream flow)-I2 are more interactive than the loop controlling I3 with D2, D4 or Q4. The use of D4 offers the best decoupling of loops. In the base case and alternative B the effect of the variables belonging to S4 on I3 is enhanced by closing the other loops, while in alternatives A and C this effect is hindered. However, at this point there is not a clear distinction between the base case and alternatives. A dynamic controllability analysis is needed. 

While machine control is important, it is the polymer state (pressure, temperature, and morphology) that directly determines the molded part quality. As such, recent technology developments have focused on closing the loop between the machine parameters and the polymer state. Conformal cooling and pulsed cooling are two molding technologies that have been... 

While various automatic schemes for precise closed-loop control of the reference phase are possible [285], this deluxe feature is not usually present. Manual adjustment is accomplished by very carefully adjusting the phase for a maximum in detector crystal current (assuming that the resonator is well matched). 

The first problem which was evident during startup was that the steam reformer steam to carbon controls (S/C) were inherently unstable and that minor upsets would lead to plant trips due to low s/c ratio. While the control system is complex, by. modelling using dynamic simulation, it was easy to determine that one of the control loops was unstable due to the discrete sampling nature of the control system and the chosen tuning parameters. (Ref 2)... 

Because the fabrication process is such an essential part of microfluidics, an overview of the principles underlying the microfabrication technology is presented. Pressure, flow, and temperature measurements are essential variables for characterizing fluid motion in any system. An important goal is the design and construction of self-contained microfluidic systems. Because of their small size, incorporation of pressure, flow, and temperature sensors directly on the microfluid system chip is highly desirable. There are relatively few examples where microfluidic systems have been constructed with these on-board sensors. There have been so many microsensor developments in recent years that it is only a matter of time before such systems will appear. Small-scale actuators to provide either open- or closed-loop control of the flow in microchannels are needed and these efforts are addressed. While experimental work on fluid flow itself in microscale structures is rather sparse, some results will be presented that emphasize the similarity and/or differences between macroscopic and microscopic flow of liquids. Although there are not many applications of... 

The controller of the inner loop is PI with Kc2 and t/ = 0.5, while the controller of the outer loop is proportional with gain Kei. 

DC motor drives have always offered high torque at all speeds and exact control of motion speed. AC induction motors have reliably converted electricity into rotary power for many years, and recently adjustable-frequency controls add variable-speed capability. While AC motors were originally relegated to relatively simple tasks, such as varying the flow rates of fans or pumps, advances in both motor and control technologies have allowed their use in higher performance operations. They are reliable sources of fixed-speed and variable-speed rotating power. Electric drives with appropriate closed-loop control operate only when required. However, to avoid unsuccessful apphca-tions, it is important to properly match the load, motor, and controller. 

A servo press is a press machine with a closed-loop control of the position and/or force. Those machines can be operated in a path-driven, force-driven, or energy-driven mode and thus mark a fourth class of press machines. But those machines can only be operated in one of those modes, which is decided by the control system. A path-driven mode in servo presses requires a position feedback loop, a force-driven mode, and a current feedback loop, while the energy-driven mode does not require any feedback loop. 

The while loop performs a similar function, executing a code block repeatedly while a condition is true however, the loop control variable must be dealt with manually. 

The sequential evaluation operator is used to sneak two or more expressions into a place where, syntactically, only one expression is expected. For example, C while loops use a control expression to control the repetition of the loop. While loops execute so long as the control expression is true. A typical while statement is... 

As with a while loop, something in the body of the loop or the control expression presumably changes the value of the test expression, so that the loop will eventually terminate. 

The control expression of this while loop calls getchar to read in a character, assigns that character to the ch variable, and then runs the body of the loop (which in the above example is empty, causing the above code to read in and ignore all of the input). The loop terminates when getchar returns the value EOF (end of file a symbolic constant that is defined in the stdio.h include file). 

Amodel-based closed-loop controller was designed for maximization of polymer production under safe process condition in emulsion copolymerization processes, while keeping the copolymer composition constant [195]. The interesting feature of the proposed controller was the use of a fuzzy model for design of the optimum reference trajectories. 

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