This is control theory.

i want to modify the diagram in the first photo model so that only y is available for control. So I replaced the controller at the exit of system at xd$.$ However, when I do like this, I get an error message from $1/$s and Gain$*$u$1.$error: incompatible port sizes, the dimension #$1$ of the output port #$1$ of the block MatrixGain$\_1\_3$ is $1$ The dimension #$1$ of the input port #$1$ of the block x is $4(23)$How should I fix this error and how should I implant a controller to control at y only?