Fundamentals of Control Systems, Automation, and Robotics
Control Systems and Automation Concepts
Control System Definition
A control system is a set of devices integrated into a machine used to manage or regulate its behavior, ensuring a specific magnitude (like temperature, speed, or position) varies as desired. For a machine to operate automatically, it must incorporate a control system.
Types of Control Systems
Open-Loop Control Systems
These systems operate for a predetermined duration or sequence, irrespective of changes occurring in the environment during the activity. They initiate action based on a preset value, known as the setpoint, without monitoring the actual output.
Examples:
- Dishwasher (runs a fixed cycle)
- Washing machine (runs a fixed cycle)
- Simple radiator (outputs heat without checking room temperature)
Basic Schematic: Input Devices → Control Devices → Output Devices
Closed-Loop Control Systems
These systems can modify their activity based on real-time environmental variables or the system’s output. They employ a feedback process: the system continuously measures the value of the magnitude being controlled, and the controller uses this information to make adjustments.
Examples:
- Refrigerator (adjusts cooling based on internal temperature)
- Electric radiator with a thermostat (adjusts heat output based on room temperature)
Basic Schematic: Input Device → Control Device → Output Device → Sensor (providing Feedback) → Control Device
Structure of a Control System
A typical control system includes:
- Sensor: Detects variations in a physical magnitude (e.g., temperature, light, pressure) and converts them into signals usable by the control system.
- Controller: A set of devices that receives information from the sensor, processes it according to its programming or logic, and decides the appropriate action to take.
- Actuator: Transforms the controller’s decision (usually an electrical signal) into a physical action (e.g., opening a valve, turning a motor) that directly affects the system being controlled.
Automation Definition
Automation refers to a component or system within a machine capable of performing one or more actions without direct manual intervention. It can also be defined as a system designed to repeatedly perform specific actions consistently.
Key Mechanical and Electrical Components
Gears
A gear mechanism results from the precise combination of toothed wheels or other mechanical operators designed to transmit motion or change speed/torque. In these systems, the teeth mesh directly. The shape, orientation, and module (a measure of tooth size) of the teeth dictate how they connect and are fundamental to their classification.
Example: The mechanism driving the hands of a clock.
Relays and Their Elements
A relay is an electromagnetic operator that functions as a switch. It allows a low-power signal to control a higher-power circuit by opening, closing, or switching one or more electrical circuits based on the energized state of its coil.
Components:
- Electromagnet: Composed of a magnetic core and a wire coil. When current flows through the coil, it creates a magnetic field.
- Mobile Element (Armature): A movable part (often a plate or lever on a pivot) that is attracted by the electromagnet when energized. It may include a spring or damping system for return action.
- Contacts: The electrical switching parts of the relay. They experience mechanical movement and carry the circuit current. Relays can have:
- Normally Open (NO) contacts: Open when the relay is de-energized, close when energized.
- Normally Closed (NC) contacts: Closed when the relay is de-energized, open when energized.
- Changeover (CO) contacts: Switch the connection between a common terminal and either an NC or NO contact.
Robots and Programmable Automation
A robot is an electronic device, often electromechanical, capable of automatically executing a variety of complex operations or movements. Crucially, it represents a form of reprogrammable automation. This means the set of instructions (the program) residing in its controller can be modified at any time to change its tasks or behavior.
Robot Sensors
Robots utilize sensors to perceive their environment and internal state:
- External Sensors: Detect variables in the robot’s surroundings, such as light, pressure, proximity, sound, or images (vision systems).
- Internal Sensors: Monitor the robot’s own mechanisms, such as joint angles, motor speed, wheel rotation, battery level, or internal temperature.
Levers
A lever is a simple machine consisting of a rigid, elongated bar that pivots around a fixed point called the fulcrum. It works by transforming an input force (the effort) applied at one point into an output force (the load or resistance) at another point, often providing mechanical advantage (amplifying force or distance).
Automation Examples Analysis
Analyzing common automated systems:
- Traffic Light (Semaforo): Primarily operates based on preset timing sequences, potentially adjusted for traffic flow patterns but usually without real-time feedback on individual cars waiting. Typically considered open-loop.
- Answering Machine: Records messages when triggered (e.g., by ringing). Its core function of recording is predetermined and doesn’t adapt based on message content. Generally open-loop.
- Parking Ticket Dispenser: Issues tickets upon request (e.g., button press or vehicle detection). If it simply issues tickets without checking parking availability, it’s open-loop. However, if it connects to a system monitoring the number of parked cars and stops dispensing tickets or controls entry when the lot is full, it incorporates feedback, making it part of a closed-loop system.