Thermal Systems [Part 3]

Proportional Control

Lia and I worked on the MATLAB proportional control. We experimented it by using the heater on MotorCar and by simulation. It was interesting to see the similarities and differences in our simluation and experimented results. We used 20, 5, and 2 for the gain to be used in our system. With each gain, the system reached the target temperature differently.

Below are the experimental results of the system with the gain of 0.5W/K, 0.2W/K, and 0.05W/K. We found the system with the gain of 0.2W/K to be optimal because it reached the target temperature gradually without much oscillation. The system with 0.5W/K was provided too much power in the beginning and, as a result, it overshoot the target temperature. The system with 0.05W/K was not supplied with enough power to reach the target in the given time. (Also, it is interesting to note the unexpected dot plotted on our 0.5W/K graph. We do not know how it happened, but it happened!) We have submitted our deliveries to the Conference Drop Folder, and there should be all of our results for simulations for those systems.





Proportional and Integral Control

I found this exercise very interesting, maybe because I like the word "proportional" as I have explained in my blog entry for the MotorCar proportional control. With the gain that we found optimal in the previous exercise (gain = 5 in the units of our system), we were able to experiment the proportional integral control.

Here is the result of our experimentation on proportional integral control. In the beginning, full power is being supplied to the system to bring up the temperature to the target temperature. Once it reaches the target temperature of 340K, the power drops to near 0 to not over shoot the target. As time passes, there is more fluctuation in power setting because of the Law of Cooling. I just found it invigorating how the system adjusts its power setting proportional to the temperature or the error (target state - present state). It is amazing how the temperature is being kept almost constant at the target temperature throughout the time interval!


We also have the simulation of our Proportional integral control in the Conference Drop Folder. (I am only discussing about our experimental results here because they are more interesting!)