Example: Train DDPG Agent to Swing Up and Balance Pendulum: Where are mechanical constants initialized ?

Inside the pendulum block is a gain block with gain 1/( I + (m * L^2) ), where m is the mass of the pendulum, and L is the length of the pendulum.

What is the first term I (an uppercase i) and why is it there ? To my knowledge theta_ddot = torque/( mass * (length^2) )

Additionally where are these constants initialized ?

Similarly, for the gain block with the gain of c, what are the units for this constant and where is it initialized ?

[William Rose]

@Roy Nordstrom, it seems that this question is related to your recent simulink question. There is not enough information provided here for others to help. Please provide a context and necessary background info. Thanks.

Answer 1

[Emmanouil Tzorakoleftherakis]

I am assuming the question is about this example.

Inside the pendulum subsystem, we are modeling the equation (I + ml^2) theta_ddot = tau - c theta_dot + mgl sin(theta), where I (capital i) is moment of inertia and c is damping coefficient. These parameters are defined inside the workspace of the Simulink model, so if you go to the Modeling tab at the toolstrip -> Model Explorer -> Model Workspace you should be able to see the attached.

As you can see, both I and c are set to 0 for this example.

[Roy Nordstrom]

Thank you. Now it is clear.