The "DC Machine Block" that you are using in your Simulink Model is intended to be used with Mechanical Inputs and does not talk about a DC Motor. From your use case, I understand that this is not the block you intend to use.
Kindly refer to the below documentation to understand the working of a "DC Machine Block":
The system that you intend to build can be found in the link below:
You may use the "DC Motor Block" and modify the parameters according to your specifications. This also gives you freedom to modify individual block properties of the model.
Hope this helps!
