In Figure 9.4 (a) can be seen images of the reservoir / tank water. There are water depth h, water discharge of Qin and discharge water out of Qout. Greater than the incoming water we can not predict. It could be a huge Qin Qin is very small or even no flow at all.
Water Reservoirs Figure 2.4 (a) and the Human Operator (b)
Figure 2.5 Process Controls in Humans (a) currency, (b) the brain and (c) hand
A sign is a point which shows the depth / height of the desired water, amounting H. It is expected from this system height or depth of the water is always at H, no higher and no lower. If it happens is the height or depth of the water is not equal to H so that there is a mistake or error. For the purpose of the system can be achieved, namely to maintain the value of the actual altitude or water depth (h) is always equal to H, it would require an operator to control every condition occurs, as shown in Figure 2.4 (b).
What is done by a human operator so that a height or depth of the water can be dipertahan right at level A (depth of H)? What is the process that occurs from these illustrations?
Obviously easily bias we answer when we look at Figure 2.4 (b). Operators will open or close the valve / valve on the pipe to the direction of discharge. Obviously if the actual water depth (h) is greater than the value of the desired depth (H) then an operator or guard will open the water valve / valve, so that the depth of the water will be reduced, of course, the value of h will approach H.
Conversely, if the actual water depth below the depth of the water is expected, then surely performed by an operator or keeper of the water is shut valve / valve, so that will happen is that the actual water level will rise in line with the flow of water from the Qin.
It appears that these valves as water faucets that can be opened or closed variable, to do with more or less the volume of water that is piped out (Qout). What happens is the observation that an operator with eyes that look at water depths up to the action, ie close or open the valve. How the process is going on? this can be explained according Figure 2.5. Each of these components, namely the eye, brain and hands can be explained as follows:
a. Eye
Serves to keep an eye on the water level height.
b. Brain
Has two functions: to compare the actual water level with the reference level line (A) and then take a decision, namely:
If the actual water level exceeds the mark A, the valve must be opened
If the water level is actually less than the mark A, then the valve is closed.
If the water level is actually the same as the sign of A, then the valve is left (not closed and not opened)
c. Hand
Serves to open or close the valve.
Figure 2.6 Block Diagram of Process Control in Humans
From the block diagram according to Figure 2.6 we can understand how the process control in the example yangterjadi control system maintains the level of water at the top. Reference height (H) and the actual height (h) than the comparator (+/- sign). Where the altitude is actually observed by a pair of eyes, then of course the signal sent from the eye to the brain through sensory nerves. In this case the comparison was located in the brain.
So we get an error or an error signal. The value of this error bias is positive, negative or nol.Kemudian by the brain, taken a decision in accordance with the above mentioned (there are 3 possible conditions). In this case the function of the brain as a controller. Control signals generated by the brain, transmitted through motor nerves to the hands. Surely this signal will be sent out to open or close the valve water pipe coming out based on the decision of the brain as a function controller.
Because the valve is opened or closed, resulting in the level of a tank water level to be changed, it can be a big semakn or reduced. Then the water level is observed by eye again which is then sent to the brain, compared and a decision taken by the brain. And this regulation occurs continuously. What happened between harapandan reality? of course there will be errors. What if no correction of the errors that occurred there, in this case there is no eye that takes into account the level of the water level.
Surely we will walk in blindness, do not know the exact height of the water level (in fact) how. It could have happened is too little water or the water will overflow because too much is streamed. Here we need more accurate control systems, namely the need for feedback from the output / reality produced (level height) should be compared with the reference (hope) we. And of course, the controller must also be able to take decisions accurately and completely as it should be.
As this is a closed loop control system that works. The concept as it applies to any existing control system. There is a reference value, comparison, controllers, actuators, and sensors plant. These terms will be explained in the next section.