Closed Loop Systems

Summary

In this lecture on control systems, the focus shifts from open loop systems to closed loop systems, which overcome the reliability issues of their predecessors by incorporating feedback. The closed loop system continuously measures and adjusts the output to maintain the desired level, as exemplified by air conditioners and geezers that regulate temperature. The lecture highlights the higher accuracy and reliability of closed loop systems, contrasting them with the simplicity and lower cost of open loop systems. The importance of the feedback mechanism is emphasized, setting the stage for further exploration of control system dynamics and the role of Laplace transform in upcoming sessions.

Takeaways

• 🔁 Open loop systems have a major disadvantage as they cannot handle disturbances and do not know when to stop the process, such as an immersion water heater that heats water until manually switched off.
• 🔄 Closed loop systems overcome the limitations of open loop systems by continuously measuring the output and using a feedback signal to maintain the desired output, improving system accuracy and reliability.
• 📊 The block diagram of an open loop system consists of a controller section and a process section, but lacks the feedback mechanism present in closed loop systems.
• 🌡️ An air conditioner serves as an example of a closed loop system, continuously monitoring and adjusting to maintain the desired room temperature.
• 🚿 A geezer, a type of water heater, is another example of a closed loop system that maintains a set temperature by monitoring and adjusting the heating process.
• 🔍 The presence of feedback in closed loop systems allows for error detection and correction, compensating for disturbances and enhancing system performance.
• 📉 Open loop systems are generally less accurate and less reliable compared to closed loop systems due to their inability to handle disturbances.
• 🛠️ Open loop systems are simpler and less expensive to design because they do not incorporate a feedback mechanism, making them more cost-effective.
• 🔧 Closed loop systems are more complex and expensive to design due to the additional feedback factor and the resulting complexity in circuitry.
• 🔄 The key differentiating factor between open and closed loop systems is the presence of feedback, which is absent in open loop and essential in closed loop systems.
• 📚 The lecture concludes with a预告of reviewing the Laplace transform in the next session, highlighting its importance in the study of control systems.

Q & A

What is the primary disadvantage of open loop systems discussed in the lecture?

The primary disadvantage of open loop systems is that they are not able to handle disturbances effectively and do not know when to stop, leading to a lack of reliability.

How does a closed loop system overcome the limitations of an open loop system?

A closed loop system overcomes the limitations of an open loop system by continuously measuring the output and feeding it back to the input to determine the error with respect to the desired output, allowing for adjustments to maintain the desired output.

What is the role of the error detection unit in a closed loop system?

The error detection unit in a closed loop system measures the output continuously and compares it with the desired output to determine the error, which is then used to adjust the input accordingly.

Can you provide an example of a closed loop system mentioned in the lecture?

An air conditioner is an example of a closed loop system, as it continuously monitors the temperature inside the room and adjusts the operation of the compressor to maintain the desired temperature.

How does a geezer, as a closed loop system, maintain the desired temperature of water?

A geezer maintains the desired temperature by continuously monitoring the water temperature and turning off and on the heating element to maintain the set temperature, adjusting as needed when the temperature decreases.

What is the main difference between open loop and closed loop systems in terms of reliability?

Closed loop systems are more reliable than open loop systems because they can handle disturbances and maintain accuracy, while open loop systems cannot effectively manage disturbances and are less accurate.

Why are open loop systems considered to be less complex in design compared to closed loop systems?

Open loop systems are less complex in design because they do not involve a feedback mechanism, resulting in simpler circuitry without the need for additional components to process feedback signals.

How does the presence of feedback in closed loop systems affect the system's cost?

The presence of feedback in closed loop systems makes them more expensive compared to open loop systems, due to the additional components and complex circuitry required for processing feedback signals.

What is the significance of the Laplace transform in the study of control systems as mentioned in the lecture?

The Laplace transform plays an important role in control systems as it is used for analyzing and designing systems in the frequency domain, which is crucial for understanding system dynamics and stability.

What will be the focus of the next lecture following the one in the script?

The next lecture will focus on a review of the Laplace transform, as it is an essential tool for further study and analysis of control systems.

Why is the feedback mechanism considered the distinguishing factor between open and closed loop systems?

The feedback mechanism is the distinguishing factor because it is absent in open loop systems and present in closed loop systems, enabling the latter to adjust and maintain the desired output in response to disturbances.