Here is a small matlab reference for feedback calculations or simulations:

• roots: Find polynomial roots
• poly: Convert roots to polynomial
• conv: Convolution and polynomial multiplication
• polyval: Evaluate polynomial
• tf: Creation of transfer functions or conversion to transfer function
• pzmap: Pole-zero map of LTI models
• pole: Compute the poles of LTI models
• zero: Computes the transmission zeros of LTI models
• series: Series interconnection of the two LTI models
• parallel: Parallel interconnection of two LTI models
• feedback: Feedback connection of two LTI models
• minreal: Minimal realization and pole-zero cancellation
• step: Step response of LTI models