Exercise: Open Loop

7.3. Exercise: Open Loop#

Question 1

Give one real-world example of a device that uses open-loop control.

Describe why it is open-loop rather than closed-loop.

Solution

A microwave oven set to run for \(2 \text{ minutes}\) is an example of open-loop control.

The microwave does not measure the temperature of the food. It only runs for the fixed time set by the user. This makes it open-loop because the heating action is independent of whether the food is actually hot enough or overcooked.

Question 2

Imagine you program a robot to drive forward for \(2 \text{ seconds}\) at \(50\%\) motor power.

On a smooth floor, it travels \(1 \text{ m}\). On carpet, it only travels \(0.7 \text{ m}\).

Why does this happen in an open-loop system?

Solution

Solution is locked

Question 3

Suppose a fan is set to run at a constant speed by setting the PWM duty cycle. Over time, dust builds up and the fan spins more slowly.

Answer the following:

  1. Why does this happen?

  2. What could be done to fix it?

Solution

Solution is locked