Presentation on theme: "CHE 185 – PROCESS CONTROL AND DYNAMICS"— Presentation transcript:
1CHE 185 – PROCESS CONTROL AND DYNAMICS WORKSHOP 4
2The 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.
3The 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.
4ZIEGLER-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
7WORKSHEET 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 =
8WORKSHEET 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 =
9WORKSHEET 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 =
10WORKSHEET 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?