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Output negative feedback

Figure 1.2. A block diagram representation of a single-input single-output negative feedback system. Labels within the boxes are general. Labels outside the boxes apply to the simplified pH control discussion. Figure 1.2. A block diagram representation of a single-input single-output negative feedback system. Labels within the boxes are general. Labels outside the boxes apply to the simplified pH control discussion.
For all commercial devices, the proportional gain is a positive quantity. Because we use negative feedback (see Fig. 5.2), the controller output moves in the reverse direction of the controlled variable.1 In the liquid level control example, if the inlet flow is disturbed such that h rises above hs, then e < 0, and that leads to p < ps, i.e., the controller output is decreased. In this case, we of course will have to select or purchase a valve such that a lowered signal means opening the valve (decreasing flow resistance). Mathematically, this valve has a negative steady state gain (-Kv)2... [Pg.83]

Say we want to control the liquid level in a tank by manipulating the inlet flow rate (Fig. 5.8). If the liquid level drops below the set point, the controller will increase its output signal to open up the inlet valve and increase liquid flow. The changes in controlled variable and controller output are in opposite directions. This is a consequence of how the error is defined in a negative feedback system. [Pg.100]

Figure M5.3. A sample negative feedback closed-loop generated within Simulink. This servo system has a first order process function and uses a PID controller. The output is sent to a graphing tool for plotting. Figure M5.3. A sample negative feedback closed-loop generated within Simulink. This servo system has a first order process function and uses a PID controller. The output is sent to a graphing tool for plotting.
Because of the negative feedback regulation of thyroid function, thyroid activation can be inhibited by administration of T4 doses equivalent to the endogenous daily output (approx. 150 pg/d). Deprived of stimulation, the inactive thyroid regresses in size. [Pg.244]

Findings of the cortisol response to DEX are compatible with both the enhanced negative feedback inhibition model and adrenal insufficiency. However, in the latter case, one would not expect that a reduced cortisol level to result from, or even be accompanied by, changes in the GR, but rather, would reflect reduced adrenal output rather than an enhanced containment of ACTH. [Pg.393]

Table 4 Summary of data from studies supporting enhanced negative feedback or reduced adrenal output in PTSD ... Table 4 Summary of data from studies supporting enhanced negative feedback or reduced adrenal output in PTSD ...
At present, there is no standard definition of a servomechanism. Some engineers prefer to classify any system with a feedback loop as a servomechanism. According to this interpretation, an electronic amplifier with negative feedback is a servo. More frequently, however, the term servomechanism is reserved for a feedback control system containing a mechanical quantity. Thus, the IRE defines a servomechanism as "a feedback control system in which one or more of the system signals represents mechanical motion . Some would restrict the definition further by applying the term only to a special class of feedback control system in which the output is a mechanical position... [Pg.280]

Cortisol concentration is described by a nonlinear time-delay differential equation [47,519] with two terms, i.e., a secretion rate term that adheres to the negative feedback mechanism [520, 521] and drives the pulsatile secretion, and a first-order output term with rate constant ka ... [Pg.335]

The output of the recycle block is added to the original input to the process u, and the sum of these two signals enters the forward block Gp(s>. It is important to note that the recycle loop in this process features positive feedback, not negative feedback that we are used to dealing with in feedback control. Most recycles produce this positive feedback behavior, which means that an increase in the recycle flowrate causes an increase in the flowrates through the process. [Pg.24]

The pituitary output of corticotropin responds rapidly to physiological requirements by the familiar negative-feedback homeostatic mechanism. Since the of corticotropin is 10 min and the adrenal cortex responds rapidly (within 2 min) it is plain that adjustments of steroid output can be quickly made. [Pg.675]


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