Control Technology and Automation: A Comprehensive Guide
Control Technology and Automation
Introduction
Control technology encompasses all procedures and devices that enable automated machines and processes. Robotics, a key application of control technology, has revolutionized industries by replacing human manipulation capabilities. It integrates principles from various engineering disciplines, including mechanics, electrical, electronics, and computer science.
Control Systems
Control systems are composed of different elements called automatisms. The primary objective of a control system is to ensure that a machine or system functions with minimal human intervention. An automatic control system aims to minimize both physical and mental human intervention in the operation of a machine or process.
Some machines and processes require human intervention in certain actions or phases. These are referred to as semiautomatic systems.
Basic Control System Components
Control systems typically consist of the following components:
- Control unit: The brain of the system, responsible for making decisions and executing control actions.
- Actuators: Devices that perform actions on the process, such as changing temperature, movement, speed, or flow.
- Sensors: Devices that gather data from the process and provide feedback to the control unit.
- Auxiliary devices: Elements that facilitate interaction between the operator and the machine, such as input devices and displays.
Open Loop Control
In an open loop system, the output of the system is not monitored or fed back to the input. These systems are simple, inexpensive, and suitable for basic functions. Examples include timed lighting systems, washing machines, and traffic lights.
Closed Loop Control (Feedback Control)
Closed loop systems, also known as feedback control systems, monitor the output and use it to adjust the process to achieve the desired result. The setpoint is the desired value that the system aims to achieve. Examples include temperature-controlled heating or air conditioning systems and water level control in a cistern.
Automated System Technologies
Automated systems can be built using various technologies, including mechanical, pneumatic, hydraulic, electrical, electronic, and microelectronics. These technologies can be used independently or in combination.
Control System: 3 Basic Parts
A control system consists of three fundamental parts:
- Controller: The driving force of the system, responsible for determining and executing the control process. It includes elements for activating and deactivating external devices, receiving instructions, collecting information from sensors, and implementing control logic.
- Actuators: The final elements that act on the process. They can cause changes in temperature, movement, speed, or flow.
- Sensors: Devices that measure process variables and provide data to the controller. Their sensitivity and accuracy are crucial for precise control.
Auxiliary Devices
Auxiliary devices enable interaction between the operator and the machine. They are used for manual data entry, system start/stop, setpoint adjustments, and manual control override.
Control Logic
Wired Logic
Wired logic systems are designed for specific functions and have limited flexibility.
Programmable Logic
Programmable logic controllers (PLCs) offer greater flexibility because their control logic resides in a computer program stored in memory. This program can be modified without changing the circuit connections. Advantages of PLCs include increased flexibility, reduced costs, easier maintenance, smaller size, improved safety, and reduced breakdowns.
Output Devices
Output devices include actuators, data displays, and audio/visual indicators. Actuators can be based on various technologies, such as electric motors, electromagnets, heaters, valves, and hydraulic cylinders.
Data displays provide information about the process status using numerical values, lights, or sounds. Lights can be interpreted using color codes, while sounds can vary in frequency and loudness. Displays can be part of synoptic panels, LCD screens, LED indicators, or monitors.
Acoustic indicators are commonly used for alarms and can range from small buzzers to powerful sirens. Complex systems may use voice synthesizers.
Input Devices
Input devices are divided into two categories:
- Operator command and information entry elements: These include switches, push buttons, keyboards, potentiometers, etc.
- Sensors: These gather information from the machine or process. They convert physical quantities into electrical signals that can be processed by the control system. Examples include temperature sensors, pressure sensors, proximity sensors, presence detectors, level detectors, infrared sensors, load cells, vision sensors, and speed sensors.