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.