In DCS control, it is basically used to control equipment systems so that they can be electronically controlled using existing standard signals, and can be applied in the following ways
Single control loop:
The control that can be completed by DCS can arrange tools in one or more loop circuits.
Single Loop is a control system that can directly control the setting of measurement results, and the calculation results of error correction will be transmitted as feedback to the actuator.
This single loop can also be referred to as a feedback control system
Overlap control:
Stacking control is a control system that can be executed by a DCS system, requiring loop control, such as the liquid level control system in a paper machine being a heat exchanger.
Control is commonly referred to as master-slave control, where the master controller is the first controller and the slave controller is the second controller that obtains remote input signals from the master loop
Batch control:
Batch system control is a control system that occurs due to repeated shutdown and startup operations based on consumer orders, with limited results.
The batch control system function on DCS can prevent control saturation, so that when restarting the control, the actuator tool can be in standby mode according to the needs of the product to be manufactured
The use of a batch processing system on the DCS of a paper machine is to maintain the normal operation of the control device when the engine stops to replace products, because with this system, operators only need to input the set points to be achieved based on production targets.
Selective control
Selective control is a control system in which a process has two manipulated variables (measuring instruments) and only one variable is controlled (actuator).
This selective control uses high and low signal selectors, with “<” indicating low and “>” indicating high. The working principle of this selective control is that the process can run well, for example, for a storage tank that will flow with a pump, using a transmitter level and filling the tank with flow control is necessary so that the tank does not overflow. Through the selective control system, it is possible to determine when the control valve must be opened or closed, with main signals from the level and flow meter.
Ratio control:
Ratio control is a control system commonly used in processes where two or more components need to be mixed and compared. An example of controlling ratios is mixing chemicals A and B in a certain proportion, where the required comparison results must always be the same. A / B