Tag: control systems
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How to Effectively Design Control Systems for Distillation Units
A distillation unit is an industrial apparatus used to separate impurities and products of a component based on their boiling point. The distillation process is managed by a control system to ensure optimal operation of the unit.The aim of the control system for a distillation unit is to manage the operations of the distillation process.…
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Basic Features of Numerical Control
Numerical control is a form of digital control that is employed on machine tools such as milling machines and lathes to automatically cut and shape the work-piece without a human operator. Each machine has its own set of axes or parameters that must be controlled; case in point is a milling machine as illustrated in…
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Process Control System Design for a Distillation Unit
The aim of a typical control system is to force a given set of process variables to act in some desired and prescribed way by either fulfilling some requirements of the time or frequency domain or achieving the best performances as expressed by an optimization index. The scope of the control tasks varies widely. The…
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Three-Position Control System: Operation & Typical Application
A three-position control is akin to two-point control, except that in this case, the controller has three states, such as forward-off-reverse, (or up-off-down, hot-off-cold, etc.). This is a control strategy that is usually applied in a system that has no specific self-seeking rest state. To help us demonstrate this control strategy, take a case of…
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How Cascade Control System Enhances Dynamic Response to Load Changes
The major limitation of a conventional feedback control system is that the correction for disturbances does not start until the process output deviates from the setpoint. Feedforward control provides big improvements in processes with large time constraints or time delays. But, feedforward control requires that the disturbances be measured explicitly and a model must be…
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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). The potentiometer mounted on the output shaft provides a feedback voltage proportional to the actual position of the output shaft. The voltage…
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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. Digital signals belong to the group of discrete signals; here the individual signals are represented…
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Steam-heated Reboiler Control System
When steam-heated reboilers are used in distillation columns and the heating medium is steam, a flow control loop for the steam will typically be incorporated. The control valve can then be placed either in the steam or condensate line. Steam pressure compensation is always recommended in these cases, and the controls are illustrated in the…
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Industrial Process Temperature Control System
Let’s consider the industrial process control system shown below: The requirement is to control the temperature ϴ in the tank. The voltage r, obtained from a potentiometer, is calibrated in terms of the desired temperature ϴc. This voltage represents the input quantity to the feedback control system. The actual temperature ϴ, the output quantity, is…
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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 the control are: Most of these activities should be performed iteratively. For example, if the…