Dimension of the matrices in state space

Hey all, I have a question related to state space matrices dimension. As we know that, x_dot = Ax + Bu If the disturbance is included, the state space equation can be rewrite as: x_dot = Ax + Bu + d Let A to be a matrix with size (9x9) and B to be a matrix with size (9x6), what should be the size of d? I faced some difficulties to implement the disturbance in my Simulink.

Answer 1

[Ameer Hamza]

'd' will have dimensions of 9x1. Look at it this way. 'Ax' is 9x1, 'Bu' is 9x1. So to add d in these vectors, it also needs to be 9x1.