QUESTION 1 (50 MARKS] An input step change from 20 to 35 m2/min is used to study the level behaviour of an evaporator. The level behaviour based on this step change is shown in Figure 1. Based on level response, it has been found the response required 8 min to reach the highest peak and reach settling time of 52 min. 12 10 Level (m) 4 Response 2 Figure 1 Based on Figure 1, it has been observed that the liquid level is below the desired set-point value. Thus suitable controller is needed for improving the level response in order to maintain liquid level at its set-point. Based on liquid level control development, the following information are used: (i) Level transmitter has a span of 1.5 m based on 0 to 50% range with time delay between 3 and 7 Transducer provides 3 to 12 psi based on 0 to 100% signal Control valve has been identified as first order with gain of 2.5 and time constant (ii) (iii) of 3 (iv) Disturbance transfer function is in the forms of first order with gain of 0.75 and time constant of 1.5 (v) Set-point transmitter is setup based on units step change (b) Determine the stability range of controller parameters based on Routh Stability Criterion. [16 Marks) APPENDIX 100 10 . . 1 iru Amplitude Ratio (AR) WAB ... PRESS 0.1 . 0.01 0.001 0.001 0.01 0.1 1 10 100 1000 90 45 0 0 +45 Best Phase Angle (Degree) * 1. ARENT 107 -135 -180 -226 011 with . . - + H. TATT 14. hrer- -270 0.001 PA! 0.01 0.1 1 10 100 1000 Frequency