I need to control crane trolley (pendulum), I have state space representation as:
$ A=\begin{bmatrix} 0 & 1 & 0 & 0 \\ 0 & 0 & \frac{m_b}{m_j}g & 0 \\ 0 & 0 & 0 & 1 \\ 0 & 0 & \frac{m_b+m_j}{m_j L}g & 0 \\ \end{bmatrix} $
$ B=\begin{bmatrix} 0 \\ \frac{1}{m_j} \\ 0 \\ -\frac{1}{m_j L} \end{bmatrix} $
$ C=\begin{bmatrix} 1 & 0 & 0 & 0 \end{bmatrix} $
$ D=\begin{bmatrix} 0 \end{bmatrix} $
I have been told that if I want to use state feedback, I need to extend this system with integrator. Why?
(I could provide any other possible information, just ask in comment)