1. ME 322: Instrumentation Lecture 37 April 22, 2015 Professor Miles Greiner Proportional control characteristics, Shift register and integral control program

2. Announcements/Reminders HW 12 Due Friday X2 (write a Proportional Control VI) HW 13 Due Monday L12PP (on/off, proportional and integral control) HW 14 Due Wednesday X3 Review for final (Next Wed. & Fri.) Open Lab Practice (Next Saturday and Sunday) Lab Practicum Finals (Schedule on WebCampus) – Guidelines http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/Tests/Index.htm This week: Lab 11 Unsteady Karmon Vortex Speed One-hour periods with your partner How is it going?

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

4. Proportional Control Current Temperature

5. Proportional Control VI construction (start at midpoint)midpoint

7. Set-Point, Lower-Control, and Measured Temperatures vs Time

8. Unsteadiness and Error versus DT Unsteadiness T RMS decreases as DT increases – And as T SP decreases – Want this to be zero The average steady-state error e = T SS -T SP – Is positive for DT = 0, but decreases as DT increases – Magnitude increases as DT increases – Want this to be zero

9. Proportional Control is Flawed Proportional control is able to eliminate unsteadiness. But, we found that if DT is large enough to make the temperature steady, then the steady-state temperature is below the desired set-point value What should Q (and FTO) be?

10. Energy Balance T Q IN = FTO(Q MAX ) Q OUT = hA(T-T ENV ) T ENV

11. Integrate Error If T-T SP > 0, then Decrease FTO If T-T SP < 0, then Increase FTO

12. How to implement this in LabVIEW

14. Figure 2 VI Block Diagram

15. Figure 1 VI Front Panel Plots help the user monitor the measure and set- point temperatures T and T SP, temperature error T– T SP, and control parameters

16. 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)