Question

Let’s say we live in a country that gets very cold, in Northern America / Europe. In winter, we monitor the outside temperature, so that heaters can be switched on, inside the house. The idea is that, the colder it is outside, the warmer it should be inside. The heating side of things is just a heater that is either switched on, or switched off. Just from the information that has been given, please discuss this matter in depth. Provide reference to OPEN / CLOSED loop control, FEEDFORWARD / FEEDBACK control and MODULATING / ON_OFF control raised in the discussion.

Answer 1

Any physical system which does not have any feedback path thus it cannot sense its output value and apply changes to it, is an open loop control system. In case of open loop system, the output can only be altered by varying the input. For example, in case of a washing machine, there is no feedback system that could allow it to sense the speed of the rotor and alter it. It is also a ON-OFF system i.e. the motor can only be turned on or off, the system doesn’t allow it to rotate in variable speed.

In the other hand a closed loop system is the one which has feedback system, which allows it to compare its output to a desired value and apply changes to its output.

Implementation of the Idea:

In case of a room heater as described, it has to be a closed system as it needs to be controlled as per the temperature outside of the house. So the system will need a temperature sensor to measure the temperature outside and send control signal to the controller of the heater to set the required temperature to be maintained inside the house.

As the heater can only be turned on or off (Cannot be regulated), the system is to be operated by ON-OFF control. Thus in the program of the controller of the heater there has to be two variables, one is cut-in temperature and another is cut-off temperature. The cut-in temperature is the threshold temperature inside of the house that sends feedback signal to the controller to turn on the heater and cut-off temperature is the temperature which sends feedback signal to the controller to turn off the heater.

Now to achieve the condition of getting higher temperature inside the room as it gets colder outside, there has to be a temperature sensor outside of the house, which keeps sending feedback signal (data of current temperature outside the house) to the controller. And the controller has to be programed to increase the cut-off temperature as the temperature outside the house decreases and decrease the cut-off when the current temperature outside the house increases.