Open-loop testing

Open-loop testing with air or with the specified gas is relativcls straightforward, but there are difficulties in carrying out closed-loop (l sk with equivalent gases. 

Oil film seals, 304 On stream, 144 Open-loop testing, 417 Operation... 

The PBL reactor considered in the present study is a typical batch process and the open-loop test is inadequate to identify the process. We employed a closed-loop subspace identification method. This method identifies the linear state-space model using high order ARX model. To apply the linear system identification method to the PBL reactor, we first divide a single batch into several sections according to the injection time of initiators, changes of the reactant temperature and changes of the setpoint profile, etc. Each section is assumed to be linear. The initial state values for each section should be computed in advance. The linear state models obtained for each section were evaluated through numerical simulations. 

The open-loop test response fitted to a first order with dead time function GPRC can be applied to other tuning relations. One such possibility is a set of relations derived from the minimization of error integrals. Here, we just provide the basic idea behind the use of error integrals. 

As far as we are concerned, using the error integral criteria is just another empirical method. We are simply using the results of minimization obtained by other people, not to mention that the first order with dead time function is from an open-loop test. 

A. Tuning relations based on open-loop testing and response fitted to a first order with dead time function... 

The control loop was effectively opened for the open-loop test by injecting a voltage source directly into the FB/OCP pin. This voltage was adjusted to provide an output voltage of approximately 102 V. For the closed-loop test, this external voltage source was not used. 

As an example of an ATV test, consider its application to a dynamic simulator of a C3 (propylene/propane) splitter. Figure 15.48 shows an ATV test and an open-loop test on the same time scale for the bottom product composition control loop. Note that the four cycles of the ATV test required 6 to 8 hr, while the open-loop test required in excess of 60 hr. The ATV results were used with TL settings, and the results for three different tuning factors are shown in Figure 15.49. 

Ziegler and Nichols presented an open-loop test method in their classic paper on tuning control loops. The method consists of starting with the control loop at steady state, putting the controller in manual output so that there is no feedback response from any change in the process variable, and introducing a step change in the controller output (valve position). Then the results are used to characterize the process response by an apparent... 

The Z-N equations for predicting controller tuning constants from open-loop test results give a recommended proportional gain of = 12.3 and integral time constant of 7 =... 

In these closed test-loops components inserted in the reactor core, the coolant, instrumentation and heat transfer systems were completely separated fi om the main FFTF core, permitting the testing of fuels and materials over a wide range of temperatures in a controlled environment independent of the main reactor coolant system. The open loop test positions and integral components of the reactor core for testing large quantities of candidate fuel pins and assemblies were cooled by the reactor primary coolant system. 

Phase 3—Open-Loop Test This supplements the previous test by checking certain aspects not amenable to closed-loop evaluation. 

Model identification is the process of quantifying process dynamics. The techniques available fall into one of two approaches - open loop and closed loop testing. Open loop tests are performed with either no controller in place or, if existing, with the controller in manual mode. A disturbance is injected into the process by directly changing the MV. Closed loop tests may be used if a controller exists and already provides some level of stable control. Under these circumstances the MV is changed indirectly by making a change to the SP of the controller. 

The open-loop test gave a dead time of 40 sec. The volume of the sample piping divided by the sample flow was 15 sec. The remainder was probably distributed through the reactor and associated piping. 

Figure 9.18a shows the results of a sample open-loop test where lead screw exhibited friction induced vibration. It is interesting to notice that, unlike the lead screw angular velocity, motor angular velocity does not exhibit considerable... 

Fig. 9.18 (a) A sample of test results showing stick-slip in open-loop tests, (b) zoomed view. 

In controlling the temperature of three steel cylinders, the manipulated variables are the percentage of high state (heat on) and low state (heat off), whereas the controlled variables are the temperature of the steel cylinders in °C. The dynamic matrix was formulated by conducting open-loop tests on the three cylinders. The normalized response coefficients are obtained as follows... 

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