I understand that you are encountering an error in the feedback loop and while using the "Sum" block.. The most common cause is when the output of the "Integrator" block does not match the expected input dimensions of the Sum block or vice versa.
For the feedback loop to work without errors, all signals within the loop must have compatible dimensions. If your input signal is a scalar, ensure that the output of the "Integrator" block (and thus the feedback signal) is also a scalar. If dealing with vectors or matrices, all elements in the loop must have matching dimensions.
From the model you've provided, I noticed that the signal dimension from the "Integrator" block is (1), whereas the expected dimension is (4), resulting in a mismatch of signal dimensions. To resolve this issue, you can adjust by setting the initial condition in the "Integrator" block to a size of 4, matching the dimensions of the signals in your feedback loop and ensuring that the initial condition aligns with your system's requirements. Then, try running the model again to see if the error has been resolved.
Hope it helps!
