Lecture Notes: Systems and Control Systems

Overview

• Definition of System Components of Electronic Systems
• Classification of Systems
• Measurement Systems
• Control Systems: Open Loop & Closed Loop

Systems

• Definition: A system can be considered as anything that takes input and produces output, interacting with various components.
• Example: A cylinder can be regarded as a system where water is provided to various components of an electronic system using sensors and actuators.
• System Components:
  • Sensors: Gather and provide information to the system, convert physical parameters to electrical signals.
  • Actuators: Convert energy from one form to another (mechanical to electrical, etc.).
  • Signal Conditioning Unit: Converts signal to a form suitable for the controller to understand.
  • Controller: Understands and processes signals to control outputs effectively.
  • Display System: Shows the final output to the user.

Measurement Systems

• Function: Used to measure and display physical parameters such as speed, water level, etc.
• Components: Sensors, Signal Conditioning Unit, Controller, Display Unit.
• Example: Measuring speed using a sensor that generates a voltage signal, processed by an amplifier, and displayed digitally.

Control Systems

• Definition: Systems used to control processes or parameters.
• Types:
  • Open Loop Control System:
    • No feedback mechanism.
    • Components: Control Unit, Actuator, Process Variable.
    • Example: Room temperature control where a human operator turns the switch on/off based on the desired temperature.
  • Closed Loop Control System:
    • Has feedback mechanism for automatic adjustment.
    • Components: Control Unit, Actuator, Process Variable, Feedback.
    • Example: Automatic room temperature control using a thermostat.

Open Loop Control System

• Components:
  • Control Unit: Generates the control signal.
  • Actuator: Executes the control signal by producing the desired effect.
  • Process Variable: The parameter being controlled (e.g., a motor).
• Characteristics:
  • Simpler, lower cost.
  • No feedback, hence less accurate.
  • Faster response time.
• Examples: Manual room temperature control, certain washing machine operations.

Closed Loop Control System

• Components:
  • Control Unit: Includes feedback to adjust and correct the system.
  • Actuator: Executes the control signal.
  • Process Variable: The controlled parameter (e.g., motor).
  • Feedback Signal: Used for automatic correction and stability.
• Characteristics:
  • More complex, higher cost.
  • Provides accurate and stable control.
  • Slower response time due to feedback processing.
• Examples: Automatic room temperature control, water level control systems.

Comparison: Open vs. Closed Loop Systems

• Feedback: Present in closed loop, absent in open loop.
• Construction Cost: Higher in closed loop.
• Reliability: Closed loop systems are more reliable and accurate.
• Response Time: Open loop systems are faster.
• Stability: Closed loop systems offer better stability.

Conclusion

• Understanding the differences and applications of open and closed loop control systems helps in choosing the appropriate system for various tasks.
• Practical examples include home appliances, industrial machinery, and measurement devices.

Additional Examples

• Electric Refrigerators: A typical example of a closed loop control system using feedback for temperature regulation.