A. The average surface temperature on Mars is -63 °C, so temperature control is used to drive a heating element, or a heater, inside the Martian home. You decided to use an electric heater placed in the middle of the home as your heat source. To measure the temperature, you decided to put a thermocouple above the door entrance: 1. In order to guarantee that the Martian people will live, you decided to make a closed-loop control system. Based on the exact scenario given, clarify the following: a. Which part resembles the feedback path. b. What is the set value. c. What are the controlling and the controlled variables.
task 2
A. The average surface temperature on Mars is -63 °C, so temperature control is used to drive a heating
element, or a heater, inside the Martian home. You decided to use an electric heater placed in the middle of the home as your heat source. To measure the temperature, you decided to put a
thermocouple above the door entrance:
1. In order to guarantee that the Martian people will live, you decided to make a closed-loop
control system. Based on the exact scenario given, clarify the following:
a. Which part resembles the feedback path.
b. What is the set value.
c. What are the controlling and the controlled variables.
d. When you build the Martian dome for the first time, the temperature is -63 C, calculate the absolute error.
e. If your thermo-couple measures the values from is -200 to 1500,
calculate the error as a percentage.
2. Consider the case when an astronaut comes from the Martian surface into the home.
Temperature is expected to drop due to the exposure to the Martian cold wind. From the
instance of opening the door until the instance of returning the temperature of the home to its
set value, clarify the following:
a. The dead-time in this case happens twice, describe the two events in this
scenario.
b. Based on the dead-time, do you expect the room to be generally colder
or warmer than the set-point? explain why based on the described
configuration of the control system.
c. What is process lag in this case? What is its relation with the actuator
capacity.
d. If you want to reduce the control lag, which component of the system
will you modify.
B. Now you have enough background to do the actual design of the process controller. The researchers in
your department decided to start with a proportional controller, determine the following:
i. To find a suitable value for the proportional gain used for the P mode controller, you
used an open loop tuning method. You have disconnected the heater off of the
controller, and applied 500 Watts to it while it is rated power is 2000 Watts. Then you
have recorded how the temperature rises with time and plotted the following process
reaction curve accordingly, find a suitable value for the proportional gain given that KP = 0.7 x P / ML.
Figure 3 - Process Reaction Curve after applying a 500 W test actuating signal to the heater directly.
ii. Using the value of the proportional gain you just have calculated in [i], find the
correction signal value as a percentage, if an error of -3% occurs to the system
temperature, and the zero-error actuator signal is set at 20%.
iii. Based on the values you found in the previous question for P and e (%), and assuming
you controller uses a 4-20 mA current loop protocol to control a 2 KW heater. Find:
1. The real temperature when the error is -3%.
2. The current that is transmitted by the controller as an actuating signal
3. The power at which the heater will run at.
[The sensor as indicated previously has a range of -200 to 1500 C, the heater runs
at 0.4 KW when the set and real values are equal, and a rated power of 2 KW].
iv. You have considered the possibility of the dome suffering a permanent leakage of heat
due to a worn-out part in the dome surface. Would the proportional controller be able
to compensate this permanent change in temperature? In other words, would the
proportional controller be able to return the dome temperature to 25 °C? If yes explain
why, if Not then what would you do to the control system to guarantee that the
temperature will return to 25 °C? Propose two solutions.
solve all,or only part A(1 & 2)
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