Tag: Industrial control
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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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The General Principle of using a Servo Motor for Position Control
Servo motors are typically employed in closed-loop position control; for example let us consider the following application, where the angular position of the output shaft is intended to follow the reference voltage (ϴref). Figure 1.0 Closed loop angular … Read more
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ZigBee Wireless Protocol for Industrial Communication
ZigBee is an open wireless standard for low-rate networks. It is an IEEE standard 802.15.4 protocol. The physical layer radio operates at 2.4 GHz band carrier frequencies with direct sequence spread spectrum (DSSS). It supports a range of up to … 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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How Modbus is used in Industrial Networks
Modbus is an open standardized communication protocol that was founded by Modicon. Initially it was designed for the communication among PLCs in industrial applications but it also gained significance use in building automation domain for instance in HVAC systems, DDCs … 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