Control Systems Lecture Notes

Centralized Control Systems

Control Systems Overview

  • Definition: A control system is a device or set of devices that manages, commands, directs, or regulates the behavior of other devices or systems.

  • Applications: Can vary in complexity from simple home heating controllers to large industrial control systems for managing processes or machines.

Architecture of a Control System

  • Fundamental Components:

    • Input: Receives information from the environment through sensors.

    • Controller: Processes inputs and makes decisions based on predefined rules or algorithms.

    • Feedback: Provides information on the output's performance to the controller to adjust system behavior if necessary.

    • Output: Executes control commands to affect the environment or system being controlled.

    • Process: The system or operation being controlled.

Everyday Applications of Control Systems

  • Control systems are prevalent in daily technologies, including:

    • Elevators

    • Vending machines

    • McDonald's food ordering systems

    • Airport HKID gates

    • Kitchen appliances (e.g., microwaves)

    • Washing machines

    • Home security systems

    • Air conditioning systems

    • Medical devices (e.g., pacemakers, automated insulin monitors)

    • Automated sensors (e.g., doors)

    • Automobile features (e.g., cruise control, power steering)

Advantages of Automated Control Systems

  • Fast Response: Computers can respond swiftly to changes in state.

  • Continuous Operation: Systems can run 24/7 without rest.

  • Hazardous Environments: Capable of operating where human presence might be dangerous.

  • Consistency: Provide reliable performance unaffected by fatigue.

Limitations of Automated Control Systems

  • Electrical Dependence: Require a constant power supply.

  • Anticipated Events: Only react to predetermined conditions based on programming.

Inputs in Control Systems

  • Types of Inputs:

    • Sensors detecting physical phenomena such as sound, light, and pressure.

    • Inputs must often be converted from analogue to digital using an Analogue to Digital Converter (ADC).

    • Other input devices include keypads, remotes, etc.

Sensors

  • Definition: Devices that detect or measure physical properties and respond accordingly.

  • Types of input signals include analogue signals from sensors converted for processing.

Processing Components

  • Microprocessors:

    • Defined as a complete computer on a microchip, incorporating CPU functions, memory, and I/O connections.

Input Devices

  • Choosing the appropriate input device depends on specific scenarios. Common devices include:

    • Mouse

    • Keyboard

    • Joystick

    • Light Pen

    • Touch Pad

    • Microphone

    • Scanner

    • Track Ball

    • Digital Camera

Outputs from Control Systems

  • Output Devices: Control systems regulate various output devices such as:

    • Speakers

    • Display screens

    • Robot arms

    • Actuators (requiring a control signal and energy source)

Feedback in Control Systems

  • Role of Feedback: Essential for modifying or controlling a process by its results, ensuring operations meet desired outcomes.

  • Feedback Loop Process:

    1. Measurement: Capture output readings.

    2. Comparison: Align actual output with the desired setpoint.

    3. Error Calculation: Determine discrepancies.

    4. Adjustment: Change system behavior based on errors.

    5. Repetition: Continuous adjustments maintain desired system operation.

Open vs. Closed Loop Systems

  • Open Loop: No feedback applied; output does not influence future inputs.

  • Closed Loop: Feedback from output affects future inputs and system adjustments.

Social Impacts and Ethical Considerations

  • Embedded Systems: Technologies like electronic tagging, surveillance, and smart home systems raise social and ethical issues related to privacy and data security. Examples include:

    • Tagging prisoners: Monitors movements, raising concerns about privacy.

    • Surveillance systems: Enhances safety but can invade personal privacy.

    • Smart homes: Offer convenience but may compromise user data security by collecting personal information.

Comparison of Control Systems

  • Centralized Control Systems:

    • Computing occurs at a centralized location with terminals connected to a main computer.

    • Offers unified control but can result in a single point of failure.

  • Distributed Control Systems:

    • Components are networked and interact to achieve goals collaboratively.

    • Redundancy and failure resilience can occur due to multiple points of control.

Advantages of Centralized vs. Distributed Systems

  • Centralized Advantages:

    • Easier administration, more control.

  • Distributed Advantages:

    • Quicker access, shared load, and tailored responses to the environment.

Example Scenarios and Applications

  • Security Systems: Utilizing various sensors (like movement and heat sensors) to enhance safety.

  • Ethical Implications: Discussions around the necessity and risks of personal tracking devices, weighing benefits against privacy rights.

Examination Question Example

  • A hypothetical question asks about implementing smart building controls using sensors and transducers to manage door operations effectively.

  • Students may be prompted to compare centralized systems to distributed ones and analyze the implications of each.