Category: Control Systems
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Control Modes in Automation Systems
The mode of control is the way in which a control system makes corrections relative to an error that exists between the setpoint of a controlled variable and its actual value. We have a number of ways (i.e. control modes) … Read more
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The Performance Limits for PID Controllers
PID Controllers can be applied successfully to most control problems in process control, electrical drive systems and servo mechanisms due to the fact that most of these processes have a dynamic behaviour that can be adequately approximated by a second-order … Read more
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What is Selective Control?
In a number of process control problems, we may have more measurements (controlled variables) than manipulated variables. Hence, it is impossible to eliminate errors in all the controlled variables for arbitrary setpoint changes of disturbances by using only simple (single-input/single … Read more
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5 Control Techniques – Their Features & Applications
We have a number of control theories that have been put forward on how to design control laws to accomplish various purposes. Generally they can be classified as follows: Classical Control This control technique deals with the behaviour of dynamical … Read more
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Hierarchical Control Strategies for a Process Plant
In a process plant, we typically have a number of control goals that require different algorithms and types of information from the process; from the level closest to the process to the plant-wide control. All these activities ought to be … Read more
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What is a Discontinuous Controller?
This is a controller with only 2 switching states, that is, the output signal is switched ON and OFF depending on whether the process variable goes below or above a preset limit or setpoint. An example of a discontinuous controller … Read more
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Analog vs. Digital Controllers
Analog signals pass continuously through a full range of values for example a measuring device converts the process variable (PV), say temperature, into a signal corresponding to this temperature. Each temperature value corresponds to a value of the electrical signal. … Read more
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Position Control System using a Microprocessor-Based Controller
Consider the following figure illustrating a position control system employing a microprocessor-based controller with parallel ports: Figure 1.0 Microprocessor-based controller with parallel ports The system above has one output port and three input ports (each port has its own address). … Read more
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Analog Proportional Controller
An analog controller typically employs op-amps to provide the necessary gain and signal processing. Let’s consider the flow control system below: Figure: Flow control system In the system above, the controller’s function is to maintain the flow of a liquid … Read more
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Basic Steps to Consider in Designing a Control System
Typically a control system should be designed to work together with an already existing process. The control design problem can be stated at local, supervisory or even plant-wide level. If we consider the local level, the typical steps in designing … Read more