Load response

Dynamic load response time This is the amount of time it requires the power supply to recover to within load regulation limits in response to a step change in the load. 

The only function of the voltage feedback loop is to hold the output voltage(s) at a constant value. Complications arise in areas such as transient load response, accuracy of the output(s), multiple outputs, and isolated outputs. All of these individually can be nightmares for the designer, but if the design approaches are understood then each factor can easily be satisfactorily addressed. 

On the other hand, for aircraft and spacecraft structures, real laminate behavior is pretty typically linear. Laminate behavior is reasonably linear even with some 45° layers which you would expect to contribute their nonlinear shear deformation characteristic to the overall laminate and degrade its relative performance. If you go beyond the behavior of a laminate and look at a large structure, typically the load-response characteristics are linear. Even around a cutout, linear behavior exists. Beyond that apparent linear performance of many laminates, you might not like to operate in some kind of a nonlinear response regime. Certainly not when in a fatigue environment and probably not in a creep environment either would you like to operate in a nonlinear behavior range. 

Secondly, these quotations emphasize the fact that the same river input that fuels longitudinal heterogeneity in reservoirs also forms a strong link between the reservoir and its watershed (e.g., [6]). This link has been conceptualized mostly in the form of load-response empirical models [7, 8], or mass-balance approaches [9]. Curiously, empirical modelers usually consider reservoirs as stirred reactors, ignoring the longitudinal spatial heterogeneity present in most situations and processes. 

Figure 9-4 Too Little Phase Margin Shows Up in a Step-Load Response Test...

Most disturbances in chemical engineering systems are load disturbances, such as changes in throughput, feed composition, supply steam pressure, cooling water temperature, etc. The feedback controller s Auction when a load disturbance occurs is to return the controlled variable to its set-point by suitable changes in the manipulated variable. The dosedloop response to a load disturbance is called the regulator response or the closed-loop load response. 

Unfortunately much of Ais interaction analysis work has clouded the issue of how to design an effective control system for a multivariable process. In most process control applications the problem is not setpoint responses but load responses. We want a sy stem that holds the process at the desired values in the face of load disturbances. Interaction is therefore not necessarily bad, and in fact in some systems it helps in rejecting the effects of load disturbances. Niederlinski [AIChE J 1971, Vol 17, p. 1261) showed in an early paper that the use of decouplers made the load rejection worse. 

One of the major questions in multivariable control is how to tune controllers in a diagonal multiloop SISO system. If PI controllers are used, there are 2N tuning parameters to be selected. The gains and reset times must be specified so that the overall system is stable and gives acceptable load responses. Once a consistent and rational tuning procedure is available, the pairing problem can be attacked. 

Now we must specify the desired load response of the output. The ideal response would be to keep the output at zero, but this of course is not possible. The best that we could do would be to detect the error at the first sampling period and drive the process back to zero at the second sampling period. During the first sampling period, the system responds in an openloop manner to the load disturbance. So at t = Tj the output will be... 

A comparison between the step load response using the transient domain model and the state space average model is shown in Fig. 4.49, while a similar comparison of the output inductor current during the transient step load is shown in Fig. 4.50. 

Figure 4.50 Average versus transient model step load response of inductor current.

Figure 4.53 SIMetrix results transient model, step load response, inductor current...

European Stationary Cycle. Smoke is measured over European Load Response test b0.36 g/km for engines >85 kW °New limit introduced in October 1998... 

Fig. 1. Load response of the closed loop IPDT system (proposed continuous line, Luyben [10] dotted line).

It is clear that for the set point change the two methodologies offer comparable performance (

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Fig. 9. Load response of the FOPTD/PID system for different values of 0.

Fig. 10. Load response of the FOPTD/PID system using the proposed (continuous line), CM (dash dotted line), and the IMC method (dotted line) for...

FIG. 8-24 Transition from well-damped load response to instability develops as loop gain increases. 

FIG. 8-26 Minimum-IAE tuning gives very satisfactory load response for a distributed lag. 

A step change in set point, however, may be a poor indicator of a loop s load response. For example, a liquid-level controller does not have to integrate to follow a set-point change, as its steady-state output is independent of the set point. Stepping a flow controller s set point is... 

FIG. 8-27 The optimum settings produce minimum-IAE load response. (a) The proportional band primarily affects damping and peak deviation. (b) Integral time determines overshoot. 

Table 8-2 summarizes these rules for minimum-lAE load response for the most common controllers. The process gain and time constant im are obtained from the product of Gt, and Gp in Fig. 8-23. Derivative action is not effective for dead-time-dominant processes. Any secondary lag, sampling interval, or filter time constant should be added to dead time 0. 

FIG. 8-29 Tuning proportional and integral settings to optimize set-point response degrades load response using a separate set-point gain adjustment allows both responses to be optimized. 

The variability of the process parameters with flow causes variability in load response, as shown in Fig. 8-50. The PID controller was tuned for optimum (minimum-IAE) load response at 50 percent flow. Each curve represents the response of exit temperature to a 10 percent step in liquid flow, culminating at the stated flow. The 60 percent curve is overdamped and the 40 percent curve is underdamped. The differences in gain are reflected in the amplitude of the deviation, and the differences in dynamics are reflected in the period of oscillation. 

The tuning settings based on the process reaction curves obtained by the open-loop tuning method, in addition to the Ziegler-Nichols method (Table 2.38), can also be selected by other methods. Figure 2.39 compares the load responses and Figure 2.40 compares the set point responses of these methods. 

Load responses of the different tuning techniques (example). 

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