Presentation on theme: "CHE 185 – PROCESS CONTROL AND DYNAMICS"— Presentation transcript:
1 CHE 185 – PROCESS CONTROL AND DYNAMICS WORKSHOP 4
2 The hazard of tuning PI controllers by trial and error WORKSHOP OBJECTIVES:1. Understand the need for integral action from the tank level control. It makes the closed loop gain one. (No offset)2. Draw a block diagram for a single closed-loop control based on known TF of each block.
3 The hazard of tuning PI controllers by trial and error WORKSHOP OBJECTIVES:3. Understand the reason for taking measures against integral windup.4. Know how to implement anti-windup measures.5. Derive the algorithm for PI control, in T. F., in analog form, and digital form.
4 ZIEGLER-NICHOLS TUNING METHOD SEE SECTION 9.3 IN TEXT FOR DETAILS.STEP 1 – PUT CONTROLLER IN P-ONLY AUTOMATIC CONTROLSTEP 2 – ADJUST K UNTIL LOOP OSCILLATES WITH CONSTANT AMPLITUDE , KUSTEP 3 – DETERMINE THE PERIOD, PU, OF OSCILLATION FROM THE LOOP
7 WORKSHEET RESULTSWhen you have determined best tuning values for disturbance rejection, record them below. Also record the number of tests you tried in your search for these best values. Kc = tI =Number of tunings tests performed =
8 WORKSHEET RESULTSIf clock time on the simulation is showing minutes, how many hours of process time did this loop tuning exercise take? At 8 hours/shift, how many loops could you tune per shift at this rate?Hours of process timed used =Number of loops tuned in 8 hour shift =
9 WORKSHEET RESULTSRepeat the above exercise with a set point tracking control objective. Start with your best disturbance rejection tuning values and determine by trial and error whether they are best for tracking SP steps from 50% up to 60% and back again.Record your best SP tracking tuning values:Kc = tI = Number of tunings tests performed =
10 WORKSHEET RESULTSIs your best tuning for set point tracking the same as your best tuning for disturbance rejection?Did having disturbance rejection tuning values as a starting point help you find set point tracking tuning values with fewer tests?