A control system manages, commands, directs, or regulates the behavior of a device or process. Control systems range from a household thermostat controlling a boiler to large industrial systems coordinating machinery and production. This lesson introduces the main parts of control systems, the difference between open-loop and closed-loop control, and common ways to implement control.
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What are the setpoint and process variable?
The setpoint (SP) is the desired target. The process variable (PV) is the measured value or status of the process being controlled.
How does feedback control use error?
The controller compares the setpoint with the measured process variable. The difference, often written as e=SP−PV, guides a control signal intended to reduce the error.
How do open-loop and closed-loop systems differ?
An open-loop system acts without using measured output to correct its action. A closed-loop system measures the output, compares it with the target, and adjusts its action using feedback.
What is fuzzy logic in control?
Fuzzy logic applies rules to measurements that can represent degrees of truth rather than only true or false. Measurements are fuzzified, rules are evaluated, and the result is defuzzified into a control output.
What role does a PLC play in a control system?
A programmable logic controller receives signals from sensors or switches, executes programmed logic, and sends commands to actuators. It is commonly used for industrial logic and sequential control.
Quiz questions
In a control system, what does the term plant refer to?Answer: The equipment or process whose behavior is being controlled.
Which feature distinguishes closed-loop control from open-loop control?Answer: It uses measured output as feedback to adjust the system's action.
Why can on-off control make a process value fluctuate around its target?Answer: It switches between two states rather than continuously varying its control action.
How does fuzzy logic differ from ordinary Boolean logic?Answer: It can represent degrees of truth rather than only true or false.
What is the purpose of sequential control in a packaging process?Answer: To ensure operations such as folding and sealing occur in the required order.
Based on the Wikipedia article Control system, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.