ME 322: Instrumentation Lecture 38 April 24, 2015 Professor Miles Greiner Integral Control

Announcements/Reminders College of Engineering Innovation Day: Friday, May 1, events/innovation-day events/innovation-day HW 12 Due now HW 13 Due Monday- L12PP (proportional/integral control) HW 14 Due Wednesday- X3, Last HW assignment Review Labs 10, 11, and 12: Wednesday and Friday Open Lab Practice: next Saturday and Sunday Lab Practicum Finals, start a week from Monday – Schedule on WebCampus – Guidelines: Next week: Lab 12 Feedback Control

Two Extra-Credit Opportunities National Instruments (NI) On-line LabVIEW Training Wednesday, April 29, 2015, 1:30 to 3:30 pm – Will that timing work? If not, when would? See instructions on WebCampus – Sign-up and actively participate to receive credit – Use your own computer or one on campus – Need headset or speakers (and microphone?) 1% of grade Lab 12.1 (Do at home, Due last lecture) See Lab 12 instructions (study effect of DT, DTi, T SP, heater and TC locations) Check out Lab-in-a-Box for DeLaMare Library Only 0.5% of grade

Lab 12 Setup Measure the beaker water temperature using a thermocouple/conditioner/myDAQ/VI Use myDAQ analog output (AO) connected to a digital relay to turn heater on/off, and control the water temperature – Use Fraction of Time On (FTO) to control heater power

Last HW: Proportional Control

Proportional Control VI You did this in HW

Integrate Error When T-T SP > 0 Decrease FTO i When T-T SP < 0 Increase FTO i

How to implement in LabVIEW

Figure 2 VI Block Diagram Modify proportional VI – entation/Labs/Lab%2012%20Thermal%20Control/Lab%20Index.htm entation/Labs/Lab%2012%20Thermal%20Control/Lab%20Index.htm

Figure 1 VI Front Panel Plots help the user monitor the time-dependent measured and set-point temperatures T and T SP, temperature error T–T SP, and control parameters

Modify Proportional Control Shift register, input DTi – Add FTOi to FTOp Display FTOi (bar and numerical indicators) Add 10log(DTi) and log(DTi) to plots Add Write to Measurement File VI – Use next available file name – Microsoft Excel – One time column

Process Sample Data

Figure 3 Measured, Set-Point, Lower-Control Temperatures and DTi versus Time Data was acquired for 40 minutes with a set-point temperature of 85°C. The time-dependent water temperature is shown with different values of the control parameters DT and DTi. Proportional control is off when DT = 0 Integral control is effectively off when DTi = 10 7 (10log(DTI) = 70)

Figure 4 Temperature Error, DT and DTi versus Time The temperature oscillates for DT = 0, 5, and 15°C, but was nearly steady for DT = 20°C. DTi was set to 100 from roughly t = 25 to 30 minutes, but the systems oscillated, and so it was increased to The controlled-system behavior depends on the relative locations of the heater, thermocouple, and side of the beaker, and the amount of water in the beaker. These parameters were not controlled during the experiment.

Table 1 Controller Performance Parameters This table summarizes the time periods when the system exhibits steady state behaviors for each DT and DTi. During each steady state period – T A is the average temperature – T A – T SP is an indication of the average controller error. – The Root-Mean-Squared temperature T RMS is an indication of controller unsteadiness

Figure 5 Controller Unsteadiness versus Proportionality Increment and Set-Point Temperature T RMS is and indication of thermocouple temperature unsteadiness Unsteadiness decreased as DT increased, and was not strongly affected by DTi.

Figure 6 Average Temperature Error versus Set-Point Temperature and Proportionality Increment The average temperature error – Is positive for DT = 0, but decreases and becomes negative as DT increases. – Is significantly improved by Integral control.

Proportional-Control Energy-Balance T Q IN = FTO(Q MAX ) Q OUT = hA(T-T ENV ) T ENV