The problem with the pressure control was that it seemed to work intermittently and seldom got to setpoint, resulting in large and unacceptable variance on the control.
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There is a commonly held belief in control circles that all PID controllers are similar and relatively simple. This is a dangerous fallacy.
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The example given in this article illustrates some mistakes made by the system integrators and control engineers at a metals extraction plant that used a well-known make of PLC and scada for its controls.
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An inherent phenomenon occurring in most control valves that few people are aware of is ‘stick-slip’.
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A good example that shows how lack of knowledge of the practicalities of control can result in terrible control characteristics.
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Over the years I have had many requests to write a book giving more detailed explanations of some of the problems I have encountered in my work on practical loop optimisation. I am by nature and inclination ...
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Some of the biggest problems associated with the final control element are hysteresis and backlash.
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75-85% of all industrial control loop problems are caused by valve issues.
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Feedback theory generally assumes that the process has a linear transfer function, which means that equal changes on the input will result in equal changes on the output.
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Michael Brown has introduced an online control loop optimisation and tuning consultation service designed to help plant engineers all over the world understand why their loops are not behaving the way ...
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Every time I work on a plant that is using a PLC and scada system for feedback control, I always first do a test on a controller module to ensure that the controllers have been configured correctly.
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This article outlines some of the practical problems and rules of thumb relating to final control elements, which can affect control in the real world.
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