img Closed Loop System

The system below consists of a small electric DC motor that drives a dial and a control system to control the position of a dial. The control system automatically changes the input to the motor based on the difference between the dial's measured position and the desired position. Use the "f", "d", and "s" keys, or the slider, to change the desired position.


Change the plant friction and inertia and notice how that changes the system response.


  1. What is the input to the controller? (answer)
    The controller input is connected to the plant output (the dial position)
  2. What is the controller output? (anwer)
    The controller output is connected to the plant's input (the voltage input).
  3. What is the system input and how does it differ from the plant input? (anwer)
    The system input is the desired position input by the user. The system input is in degrees. This is the desired position of the dial. The plant input is in voltage.
  4. How does friction affect the system response? (anwer)
    Friction adds damping to the system. With enough friction (damping) the system will not overshoot the desired position. However too much friction (damping) slows down the response
  5. How does inertia affect the system response? (anwer)
    Inertia slows down the response, but tends to increase the overshoot.

%    Inertia:
img Open-Loop Experiment