Control Systems, Actuators, and Automation Technologies
Understanding Control Circuits
Control circuits represent a significant family of electrical circuits. A circuit is a technological device where information is input to produce an output response. These circuits are broadly classified into two main categories:
- Open-chain circuits (linear control)
- Feedback control circuits (for adjustment)
Sensors and Actuators in Control Systems
Sensors and detectors are positioned at the input stage of a control device, while actuators (or working bodies) operate at the output stage. Key selection criteria for these components include:
- Speed of response
- Location suitability
- Sensitivity
- Reliability
- Robustness
- Maintenance requirements
- Compatibility with other elements
Detailed Look at Sensors and Detection Systems
Most detection systems operate by transforming a physical quantity (e.g., weight, pressure, temperature, volume, light) into a proportional electrical magnitude.
Active Sensors
These sensors directly convert energy forms such as light, thermal, mechanical, or chemical energy into electrical energy.
Passive Sensors
These sensors modify certain electrical properties (e.g., resistance, capacitance) in response to variations in other physical quantities.
Electric Actuators
Electric motors are the most commonly employed actuators in applications requiring rotational movement.
Key Characteristics of Electric Actuators
- Easy operation and good performance for rotational movements.
- Difficulty in achieving direct linear motion (often requiring conversion mechanisms).
- Quick and easy transmission of commands.
- Capability for long-distance movement.
- Readily available and low-cost electric power.
Drawbacks of Electric Actuators
- Difficulty in energy storage.
- Potential explosion risk in certain environments.
- Need for specialized (e.g., purged) regulation and protection systems.
Pneumatic Actuators
Pneumatic actuators are widely used in industry, almost exclusively in cases requiring linear motion or in explosive environments (i.e., where there is a fire risk).
Key Characteristics of Pneumatic Actuators
- Simplicity and good performance for linear motion.
- Operational lengths are typically limited (e.g., up to 2 meters), but they can handle significant forces (e.g., over 5000 kg).
- Can be adapted to perform rotary movements.
- Easy transmission of commands at reasonable speeds.
- High safety and security due to the use of compressed air.
- Simple regulation and protection systems.
Hydraulic Actuators
Hydraulic actuators are less commonly used than electric or pneumatic types but are preferred in applications where very high working forces are necessary.
Key Characteristics of Hydraulic Actuators
- Simplicity and good performance in linear motion.
- Limited stroke lengths but capable of exerting very large forces.
- Can perform rotary movements, though typically at low and constant speeds.
- Easy transmission of commands, but response can be very slow.
- Operate at high pressures, requiring absolute tightness in hydraulic circuits to prevent leaks.
- Hydraulic oil systems can be expensive and require significant installation space (large volume).
- These systems offer good protection against overloads and can possess flameproof characteristics.
Fundamentals of Automation
Automation essentially involves replacing human action with machine work. Modern artificial intelligence (AI) expert systems, which are computer-based and foundational to robotics, delve into the automation of intelligent decision-making processes.
Evolution of Automated Manufacturing Technologies
The evolution of automated manufacturing technologies shows two key trends: mechanization (the incorporation of machines into human activities) and the increasing level of automation within these mechanized activities. This progression can be categorized as follows:
Stages in Manufacturing Technology Evolution
- Manual Manufacturing: Utilizes only human hands without the intervention of any tools.
- Hand Tools: Involves an operator handling one or more tools for both workpiece manipulation and the operation itself.
- Mechanized Hand Tools: These are power-assisted hand tools where the main drive (power) is implemented by the tool itself, while the operator performs positioning and workpiece attachment.
- Universal Machine Tool: The machine performs all functions of workpiece holding, positioning, and operation. Human intervention is limited to general management and process oversight.
- Fixed-Cycle Machine: The machine automatically performs one or more specific, predefined operations. The cycle is not easily changed.
- Programmable-Cycle Machine: Similar to fixed-cycle machines, these perform a series of operations autonomously. However, to execute a different cycle of operations, it is not necessary to remove or change any physical element of the machine; reprogramming is sufficient.
- Intelligent Machine: These machines are programmed with a series of manufacturing objectives and are capable of making decisions to achieve these goals, adapting to variations in the process.
Defining Industrial Robots
An industrial robot is a universal, automatic machine primarily intended for the manipulation of objects. It is endowed with an ability to learn or be reprogrammed, operating within a defined behavioral framework or ‘type’.
A robot is typically composed of two major subsets:
- A mechanical, electrical, pneumatic, and/or hydraulic subset: This performs the functions of motorization (movement) and physical handling of objects.
- An electronic and computer-based subset: This performs tasks related to information processing, decision-making, and overall control of the robot’s actions.