Process Control

Control Your Solder Process - ECD MOLE
Control Your Solder Process. ECD manufactures the MOLE (r) temperature profiling and process optimization equipment and software for the electronic, baking and paint industries.
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Process control is a statistics and engineering discipline that deals with architectures, Mechanism (technology)s, and algorithms for controlling the output of a specific process. See also control theory.

For example, heating up the temperature in a room is a process that has the specific, desired outcome to reach and maintain a defined temperature (e.g. 20°C), kept constant over time. Here, the temperature is the controlled variable. At the same time, it is the input variable since it is measured by a thermometer and used to decide whether to heat or not to heat. The desired temperature (20°C) is the setpoint. The state of the heater (e.g. the setting of the valve allowing hot water to flow through it) is called the manipulated variable since it is subject to control actions.

A commonly used control device called a programmable logic controller, or a PLC, is used to read a set of digital and analog inputs, apply a set of logic statements, and generate a set of analog and digital outputs. Using the example in the previous paragraph, the room temperature would be an input to the PLC. The logical statements would compare the setpoint to the input temperature and determine whether more or less heating was necessary to keep the temperature constant. A PLC output would then either open or close the hot water valve, an incremental amount, depending on whether more or less hot water was needed. Larger more complex systems can be controlled by a Distributed Control System (DCS) or SCADA system.

In practice, process control systems can be characterized as one or more of the following forms:

Discrete – Found in many manufacturing, motion and packaging applications. Robotic assembly, such as that found in automotive production, can be characterized as discrete process control. Most discrete manufacturing involves the production of discrete pieces of product, such as metal stamping.

Batch – Some applications require that specific quantities of raw materials be combined in specific ways for particular durations to produce an intermediate or end result. One example is the production of adhesives and glues, which normally require the mixing of raw materials in a heated vessel for a period of time to form a quantity of end product. Other important examples are the production of food, beverages and medicine. Batch processes are generally used to produce a relatively low to intermediate quantity of product per year (a few pounds to millions of pounds).

Continuous – Often, a physical system is represented though variables that are smooth and uninterrupted in time. The control of the water temperature in a heating jacket, for example, is an example of continuous process control. Some important continuous processes are the production of fuels, chemicals and plastics. Continuous processes, in manufacturing, are used to produce very large quantities of product per year(millions to billions of pounds).

Applications having elements of discrete, batch and continuous process control are often called hybrid applications.

Examples A thermostat is a simple example for a closed control loop: It constantly measures the current temperature and controls the heater's valve setting to increase or decrease the room temperature according the user-defined setting. A simple method switches the heater either completely on, or completely off, and an overshoot and undershoot of the controlled temperature must be expected. A more expensive method varies the amount of heat provided by the heater depending on the difference between the required temperature (the "setpoint") and the actual temperature. This minimizes over/undershoot.

An anti-lock braking system (ABS) is a more complex example.

See also

Actuator
Automation
Automatic control
CALS
Closed-loop controller
Control engineering
Control panel (engineering)
Control system
Control theory
Controllability
Controller (control theory)
Cruise control
Current loop
Digital control
Distributed control system
Enterprise Historian
Feedback
Feed-forward
Fieldbus
Flow control valve
Fuzzy control system
Laplace transform
Measurement instruments
Model predictive control
Negative feedback
Non-linear control
Open-loop controller
Operational Historian
PID controller
Positive feedback
Process capability
Programmable Logic Controller
Regulator (automatic control)
SCADA
Servomechanism
Setpoint (control system)
Simatic S5 PLC
Sliding mode control
Temperature control
Transducer
Valve
Watt governor

External links

NETPROG - industrial automation company - PLC programing
The Michigan Chemical Engineering Process Dynamics and Controls Open Textbook
Process Control Training

Industrial Process Control Equipment - Ball Valves & Instrumentation
PCE is a supplier who works to deliver cost effective industrial process control equipment and solutions, including floating ball valves, instrumentation fittings and gauges.

Course Notes and Learning Resources - Process Control
Disclaimer: The articles/notes indicated by the symbol are compiled from a variety of sources and provided for student usage only ...

Advanced Process Control
SUMMARY: This report takes a non-technical look at the state-of-the-art in modern control engineering, focusing on techniques that are applicable to ...

Process Control: ,
Process Control: , ... Process Control: , A process is basically a single running program.

Connecting Industry - Connectingindustry.com - Process and Control
Process and Control magazine and website covers products, technological developments and solutions to process and control requirements.

X-Stat The Process Control Company
X-STAT (anti-static) is a range of specialist equipment for the control of static electricity on the production line. Uncontrolled static can wreak havoc in the factory and lead ...

Process Control Instrumentation
Cuthbertson Laird Group are authorised distributors of most of the major test equipment manufacturers. We can supply process control instrumentation from Fluke, Cropico & GE Druck.

OLE for Process Control from FOLDOC
OLE for Process Control < standard > (OPC) A set of seven open standards for connectivity and interoperability of industrial automation and the enterprise systems.

Process control consultants
Contek Systems Ltd, Aberdeen: Process control engineering consultant. Developers of U-Tune products. Free PID tuning calculator, tutorials and technical information.

Process Control Supervision Using Qualitative Models - ECS EPrints ...
Stobart, R. K. and Shadbolt, N. R. (1990) Process Control Supervision Using Qualitative Models. In: Proceedings of 3rd International Conference on industrial and Engineering ...