Measurement, control and regulation technology
Measurement, control and regulation technology describes a technical and scientific subject that is taught at technical colleges and universities . The field of work represents an area of automation technology and is predominantly part of electrical engineering .
In this subject area, the often overlapping areas of measurement technology , control technology and regulation technology are examined in their connection. The field is often referred to as MSR or I & C technology for e lektrisches M eat S dear and R designates ules.
measuring technology
The task of measurement technology is to obtain information about a real measurement object (measured process; measurement section). Measurement technology deals with devices and methods for measuring electrical and non-electrical quantities such as electrical current or voltage, length, mass, force, pressure, pH value, temperature or time. The continuously measured variable is usually mapped onto an electrical signal and fed to further signal processing, in particular for the evaluation of measured values and for control or regulation.
Control technology
The task of control technology is to force certain processes in a control object (controlled process; control system). The binary control technology that dominates in technology is based on binary measurement signals (possibly generated by threshold switches). As a result, a logical information processing (AND, OR, NOT, memory, counters, timers, etc.) of the binary measuring signals within a control program the respective actuators (so-called actuators or actuators driven) binary to influence of process variables.
It is essential for control technology that a distinction is made between logic controls and sequence controls .
In logic controls , the binary control signals (outputs), the values of which are generated by logically combining the binary input signals of a control device, act on binary control variables of a downstream device (control system). Simple link controls are e.g. B. changeover circuits or cross circuits with which downstream lamps are controlled. There is no feedback from the control path to the control device about an executed switching action in the case of logic controls. As a structure of their signal flow (information flow), they have an open chain and are therefore also referred to as open controls .
In addition, there are still open controls in which no sensor signals are included and which only process a schedule (time program, e.g. simple traffic light controls) or route plan (route program) via their outputs and the downstream actuators.
In sequence controls , the binary control signals act in the sense of step functions via actuators (actuators) on analog control variables of the control path, whereby the function values of these variables are changed. So z. B. when filling a mixing container, the level increases. If a desired fill level is reached during this operation, this is reported back to the control device via a binary measurement signal. Thereupon, new control signals are generated through logical links in connection with the control program, which again influence the control object via other actuators. On the one hand, the current operation is ended, on the other hand, further operations are triggered. Sequence controls have a closed loop structure of their signal flow (information flow) and are therefore also referred to as closed controls . They represent the majority of all controls in the applications.
Application of control technology
The programmable logic controller (PLC) - also known as the programmable logic controller for short - forms a contemporary basis for a wide range of control technology applications. The PLC is basically a microcontroller (CPU module) with corresponding memories for the control program and the control parameters as well as with associated inputs for sensor signals and outputs for actuator signals, supplemented by human-machine interfaces for operation and interfaces for industrial communication for programming and Networking in plants.
The PLC is the most widely used control device in practice today. It is also used as a controller , since the arithmetic-logic unit (ALU) of the internal microprocessor can perform both the logical control functions and the arithmetic control functions during information processing.
The PLC also often coordinates subordinate controllers to stabilize sub-processes within an overall process, the higher-level sequence of which is controlled, monitored and secured by the PLC. In addition, the PLC is also used for processing and evaluating measured values (data logger), as it has both analog and binary inputs.
The PLC therefore also forms the basis for modern measurement, control and regulation technology for automation in the national economy. Thus, because of its universal character, the SPS has developed into a mass product that is manufactured in millions worldwide. It therefore enables the mass application of automation, combined with its widespread use in all areas of the economy.
Control engineering
The task of control engineering is to ensure process stabilization or process control in a control object (controlled process; controlled system ) that is largely independent of disturbance variables . The control is characterized by a feedback of the influenced variable (called controlled variable or actual value), so that there is always a structure with a closed control loop . An actual value is determined from the influenced variable by means of measurement technology , compared with a specified reference value (setpoint value or reference variable) and the control variable is influenced by the controller in such a way that the deviation between actual value and setpoint value is as low as possible despite existing disturbance variables.
Application of control technology
Almost all devices, facilities and systems in the industrial as well as in the private environment contain such MSR aspects, i.e. components that deal with the acquisition of variables, their further processing and the influencing of systems and their behavior. The control is basically a combination of a measurement (recording of a measured value) and processing according to a control algorithm (output of a control value) depending on a specification (setpoint or reference variable) with the simultaneous presence of disturbance variables.
A heating control can, for example, record the current room temperature and compare it with the specification of a desired temperature setpoint and adjust the radiator temperature from this in such a way that the desired room temperature is regulated, and this largely independently of existing disturbances such as changing outside temperatures or solar radiation.
If the control technology is used on machines, these must meet the framework conditions of the Machinery Directive in Germany .
literature
- Christoph Stiller: Basics of measurement and control technology. Shaker Verlag, Aachen 2006, ISBN 3-8322-5582-6 .
- Peter Böttle, Günter Boy, Holger Clausing: Electrical measurement and control technology. 11th edition. Vogel Buchverlag, Würzburg 2011, ISBN 978-3-8343-3192-2 .
- Werner Kriesel , Hans Rohr, Andreas Koch: History and future of measurement and automation technology. VDI-Verlag, Düsseldorf 1995, ISBN 3-18-150047-X .
- Jürgen Müller, Bernd-Markus Pfeiffer, Roland Wieser: Control with SIMATIC: Practical book for control with SIMATIC S7 and SIMATIC PCS 7 for process automation. 4th edition. Publicis, Erlangen 2011, ISBN 978-3-89578-340-1 .
- Günter Wellenreuther, Dieter Zastrow: Automation with PLC: theory and practice; Programming with STEP 7 and CoDeSys, design processes, block libraries; Examples of controls, regulators, drives and safety; Communication via AS-i bus, PROFIBUS, PROFINET, Ethernet-TCP / IP, OPC, WLAN. 6th edition. Springer Vieweg Verlag, Wiesbaden 2015, ISBN 978-3-8348-2597-1 .
- Tilo Heimbold: Introduction to automation technology. Automation systems, components, project planning and planning. Specialized book publisher at Carl Hanser Verlag, Leipzig / Munich 2015, ISBN 978-3-446-42675-7 .
- Hans-Joachim Zander : Control of discrete-event processes. Novel methods for describing processes and designing control algorithms. Springer Vieweg Verlag, Wiesbaden 2015, ISBN 978-3-658-01381-3 .
Web links
Individual evidence
- ↑ G. Wellenreuther, D. Zastrow: Control technology with PLC. Vieweg Verlag, Wiesbaden 1995, ISBN 3-528-24580-8 .
- ↑ H.-J. Zander: Control of discrete event processes. Novel methods for describing processes and designing control algorithms. Springer Vieweg Verlag, Wiesbaden 2015, ISBN 978-3-658-01381-3 , pp. 38–43 and pp. 185–192.