Tyreus Tuning

Click the Closed loop ATV bullet, start the simulation mnning, and click the Start test button. After several cycles, click the Pause button to stop the simulation and click the Finish test button at the bottom of the Tune window (see Fig. 3.79). The ultimate gain (3.73) and the ultimate period (4.8 min) are displayed, as shown in the left side of Figure 3.80. To calculate the controller tuning constants, click the Tuning parameters page tab on the Tune window and select either Ziegler-Nichols or Tyreus-Luyben. 

Then click the Calculate button shown on the right side of Figure 3.80. The calculated tuning can be used in the controller by clicking the Update controller button. The Tyreus-Luyben settings are Kc= 1.16 and 7>= 10.6 min. The plot at the bottom of the figure shows that these settings yield a stable temperature controller. When the simulation is restarted after the test, the temperature is driven to the setpoint value in about 30 min with a smooth trajectory. 

Ziegler-Nichols (ZN) and Tyreus-Luyben (TL) PI tunings are evaluated. Ultimate gain and frequency are obtained by performing relay-feedback tests. Temperature control loops have three 20-s lags. The pressure control loop has two 30-s lags. There is a... 

The first controller GCuS) sees a coupled openloop transfer function in which the second controller is nested, because the controller Gq ,> is on automatic. The 67 i(v) controller is tuned by finding the ultimate gain and period and using the Tyreus-Luyben settings. The settings of this PI controller are Kc2 = 2.13 and r/2 = 1.94. 

Figures 6.14 and 6.15 give dynamic responses of the tray temperatures, reboiler heat input, and bottoms product impurity. The temperature loops were tuned using the TL (Tyreus-Luyben) tuning rules after the ultimate gain and ultimate frequency had been determined using a relay-feedback test. Two 0.5-minute first-order lags are used in the temperature loop. Temperature transmitter spans are 100T. The ultimate gain and period for the tray 6 temperature loop are 4.2 and 2.7 minutes, and for the tray 14 loop are 12.7 and 2.5 minutes. These results reflect the fact that the process gain is higher when tray 6 is...

The critical product-quality and safety-constraint loops were tuned by using a relay -feedback test to determine ultimate gains and periods. The Tyreus-Luyben PI controller tuning constants were then implemented. Table 11.12 summarizes transmitter and valve spans and gives controller tuning constants for the important loops. Proportional control was used for all liquid levels and pressure loops. 

Another tuning approach that was developed for processes that behave like an integrator plus deadtime system is the Tyreus and Luyben (TL) settings ... 

The final control structure is shown in Figure 7.46. Both the R/F and the QR/F ratios are installed. Of course the temperamre controller must be retuned. Relay-feedback testing and Tyreus-Luyben tuning give Kc = 1.96 and ti = 11.9 min. The composition controller also must be retuned but changes only slightly. 

The tray temperature controllers are tuned by inserting a 1 min deadtime in the loop and using the relay-feedback test to determine the ultimate gain and ultimate frequency. Then, the Tyreus-Luyben settings are used. Table 8.2 gives the tuning constants. 

Since the reflux-drum level loop is nested inside the temperature loop, the level loop is tuned first. A relay-feedback test and Tyreus-Luyben tuning rules give the results shown in Table 8.5. Notice that the gain and integral times are very much different than a conventional level control loop. The integral time is about 8 min and the gain is only 0.3. 

The four composition control loops each have a 5 min deadtime. They were tuned using a sequential method. Because reboiler heat input affects aU of the controlled variables fairly quickly, the Xb(x/<2r loop was tuned first with the other three controllers on manual. Relay-feedback testing was used to find the ultimate gain and period. Tyreus-Luyben tuning rules were used. Next, since reflux affects all compositions, the Xixt)IR loop was tuned using the same procedure with the Xb(j) Q loop on automatic. Then the Xs(x> loop was tuned with the two loops on automatic. Finally, the ypio(x) loop was tuned with the other three loops on automatic. Table 12.2 gives controller tuning results for aU four loops. 

All four loops contain 5 min dead times. The loops in each column were tuned sequentially with the reboiler heat input loop closed first with the reflux loop on manual. Relay-feedback and Tyreus-Luyben tuning were used. Then, with the reboiler heat input loop on automatic, the reflux loop was tuned. Table 12.2 gives the tuning parameters. 

Reflux-drum temperature in the stripper is controlled by manipulating stripper reboiler duty (temperature controller TCS in Fig. 14.10). A 1 min deadtime is inserted in the loop, and relay-feedback testing and Tyreus-Luyben tuning give tc = 2.65 and Tj= 13.2 min. 

The ramp disturbances are imposed on the process using each of the three control structures. The temperature and valve-position controllers are tuned by running relay-feedback tests. Deadtimes of 1 min are used in these loops. Temperature controller TCI is tuned at the normal design feed flow rate (4000 kmol/h), and Tyreus-Luyben tuning give Kc = 31 and Ti = 9.2min. 

The tuning of the temperature controller is different with and without the QR/F ratio since in the former case the controller output is reboiler duty while in the latter case it is the QR/F ratio. A 1 min deadtime is inserted in the temperature measurement. Relay-feedback testing and Tyreus-Luyben tuning give Kc = 0.636 and Ti = 14.5 min using a temperature transmitter range of 300-400 K and a controller output range of 0-0.05 ratio. 

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