Workshop__1_solution_rmd_rev

Workshop__1_solution_rmd_rev - EDITED SOLUTIONS Workshop 1...

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Hands-on Workshop Series Solutions by Douglas J. Cooper Copyright © 2003 by Control Station LLC All Rights Reserved 1 Workshop 1 ANSWER KEY Exploring Dynamics of the Gravity Drained Tanks Objective: To generate open loop step test data and learn how to describe the observed dynamic process behavior with a first order plus dead time (FOPDT) model. Also, to learn about the nonlinear nature of processes. 1) We always begin a controller design by analyzing the dynamic behavior of the process, or how the measured process variable responds to changes in the controller output signal. Here we analyze the dynamic behavior of the gravity drained tanks process. Click the Case Studies button on the main Control Station screen. From the pop-up list of processes, click "Gravity Drained Tanks" to start the simulation. Study the graphic and observe how a change in the controller output signal will cause the valve position to change, which changes the flow rate of liquid into the top tank, which ultimately changes the level in the lower tank. Liquid level in the lower tank is our measured process variable. 2) The formal approach for analyzing the behavior of a process is to fit a dynamic model to process data. Good data starts with the process at steady state. The controller output signal is then moved far enough and fast enough so that it forces a clear response in the measured process variable. For a step test, the controller output signal is stepped from one value to another and the response of the measured process variable signal is recorded from initial steady state to final steady state. At the upper right of the draining tanks graphic on your screen, locate the white number box below the Controller Output label. The number displayed should be 70, corresponding to a 70% output signal from the controller. The most convenient way to step the controller output signal is to click once on this white number box. Alternatively, you may double click (click twice in rapid succession) the box. If you clicked once , the box will turn blue. For the first step test, type 80 into the box and press Enter. This will cause the controller output to step from its current value of 70% up to the new value of 80%, increasing the flow of liquid into the top tank and causing liquid level to rise. If you double clicked , a pop-up menu gives you the option of performing a step, oscillate, ramp or PRBS experiment. With the Step option active, type 80 as the Controller Output Value and then click Done at the bottom of the pop-up menu. 3) Watch as the process responds. When the measured process variable (liquid level) reaches its new steady
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Workshop__1_solution_rmd_rev - EDITED SOLUTIONS Workshop 1...

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