In direct digital control (DDC) a single computer is able to carry out PID control for multiple loops at the same time make that loop data accessible between loops for purposes of cascade control, feedforward control, ratio control… Read more
Tag: control systems
Ratio Control
In some processes, it is a common requirement for two flows to be kept in precise ratio to each other for example, a gas or oil and air in combustion control, and reagents being fed to a chemical reactor hence … Read more
Feedforward Control
Feedforward control is based on principle of pre-emptive load counter-action i.e. if all major loads (i.e. disturbances) on a process variable are monitored, and their effects on that process variable are well-understood, a control system programmed to take the appropriate … Read more
Benefits of Cascade Control
We know very well that closed loop control provides increased performance over open loop control. So it would be rational to expect benefits from adding inner control loop around plant items that have degrading overall performance.
The Figure (a) below … Read more
The Basics of Ladder Diagrams for Programming PLCs
The ladder diagrams are universally used as a symbolic and schematic way to represent the interconnection between the elements in a Programmable Logic Controller (PLC). The ladder network is also used as a tool for programming the operation of PLC. … Read more
Basic Features of Distributed Control Systems (DCS)
In distributed control system, each process has its own separate controller located at the site. These local controllers are interconnected via a local area network so that all controllers on the network can be monitored or reprogrammed from a single … Read more
Proportional-Integral-Derivative (PID) Control Systems
Proportional-Integral-Derivative
For processes that are able to operate with continuous cycling, the relatively inexpensive two position controller is sufficient. For processes that cannot tolerate continuous cycling, a proportional controller is used. For processes that tolerate neither cycling nor offset error, … Read more
Proportional plus Derivative (PD) Control System
Why you should replace your old DCS systems with modern ones
To keep up with evolving technology manufacturers need to upgrade their legacy Distributed Control Systems (DCS). This might be a challenging task to undertake and at a cost to the company, but in the long run the benefits outweigh the … Read more
Proportional Plus Integral (PI) Control System
This type of control is combination of two control modes, proportional and integral (reset). The Combining of the two modes results in gaining the advantages and compensating for the disadvantages of the two individual control modes.
The main advantage … Read more