How can I fix the warning: "Warning: Physical modeling domain definition file output.m not found." Reinforcement Learning DDPG Cart Pole Problem

I attempted to simulate the inverted pendulum (cart-pole) on Matlab using the example here: https://in.mathworks.com/help/reinforcement-learning/ug/train-ddpg-agent-to-swing-up-and-balance-cart-pole-system.html

When I tried to run this, I got the above warning, along with the same warning for file 'input.m' and 'generic.m'. This warning was repeated a few dozen times in a single run, followed by the following errors:

Error using rl.env.AbstractEnv/sim (line 114)

An error occurred while simulating "rlCartPoleSimscapeModel" with the agent "agent".

Caused by:

Error using rl.env.SimulinkEnvWithAgent>localHandleSimoutErrors (line 817)

['rlCartPoleSimscapeModel/Environment/Plant/Cart']: Parameter check for block 'rlCartPoleSimscapeModel/Environment/Plant/Cart' failed.

Error using rl.env.SimulinkEnvWithAgent>localHandleSimoutErrors (line 817)

Insufficient number of outputs from right hand side of equal sign to satisfy assignment.

A possible hint was that the connectors are not connected to the blocks in the simscape model of the plant. I couldn't connect them or modify due to an error dialog box stating "Error evaluating 'OpenFcn' callback of Prismatic Joint block (mask) 'rlCartPoleSimscapeModel/Environment/Plant/Prismatic Joint'. Callback string is 'simmechanics.sli.internal.block_dialog(gcbh,'open');'

Since I am not experienced with Simscape, I attempted to replace the entire model with my own linearized simulink model. However I faced the same errors.

If anyone has any idea how to solve this issue, please suggest a course of action.

[Emmanouil Tzorakoleftherakis]

The example runs fine for me. Did you recently install/re-install MATLAB?

[Savneek Bhatia]

No, I have been using this version of Matlab (2019b) since the past couple of months and have had no issues so far. I did install the Toolboxes required for this example though. (Simscape, Global Optimization, Paralle Computing etc.)

Answer 1

[Vidhathri LNU]

This is most likely due to a corrupt installation. Perform a clean re-installation or update your MATLAB to the latest release to resolve the issue.

You could also try to restore the default states MATLAB and Simulink by resetting search path, system path and Simulink customization.

Before modifying the search path, you can take a backup of your 'pathdef.m' file, which can be located by using the command

which -all pathdef

Before proceeding, you should backup this file by copying it to a folder outside of your MATLAB path.

After making the backup, please execute the following commands in the MATLAB Command Window:

restoredefaultpath
rehash toolboxcache
sl_refresh_customizations 

After this step, please use MATLAB / Simulink normally to see if the issue occurs again. If the issue is resolved, then you can save the new MATLAB search path by executing the following command:

savepath

NOTE: This will remove any custom paths you may have created. If desired, please see the following MATLAB Answers post for how to back them up:

https://www.mathworks.com/matlabcentral/answers/166871-how-will-running-the-restoredefaultpath-and-savepath-commands-affect-my-custom-paths-and-how-do-i-ba